THE GEOLGu, OF TH;:.: CONTENTION MINE ARFA
17,1IN BUTTS'S, ARIZONA
by
Frederick N. Houser
 Thes
submitted to th.- faculty of the
Departnent of Geology
in partial fulfillment of
the requirerents for the degree of
liaster of Science
in th
Graduate College
,nivereity of Arizona
191c
.
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Page
43
43
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°
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°,°"~°,°.°."°
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sidmurlta+°°.,.",.°°.°°^"".~"~°.".°°
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Historical
^^.°".°.~°."°,...°°",~,."°°..°."....."°°..°"°°0
48
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Gladstone
Garnet Queen
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BIBLIOGRAPHY
.,°.^."^,°°".°°
°.°°."°"^.°^^.~"^.,..°"^
1
51
iii
ON3
ILLUSTRA
Following
Page
Plate
1
Geologic Map of the Contention and Senator
Eorgan 'Ane Areas,
in Buttes, Ariz(na..............
Pocket
in Buttes Quadrangle...,
Pocet
Plate
2
Topographical 174ap of the
Plate
3
Index ap Shming Location of Cfmtention Mine Area...
3
clate
14
Geno.alized Colunnar Section.........................
20
,--Iate
5
3ect1on A-A"......
34
:late
6
3ection B-B"........ ...............
?late
7
¡,12+
Plate
(.2
......... .......................
...............
Section C-C 0.*.***0******000****** ... ..
.50
3ection through Contention
43
Map of Levels in Contention
49
10
Map of Southern Claims of Twin Buttes
Aate
11
A. Nabigo and Gartion Faults;
re
Plate
B.
50
*
.4 a
Shaft of 'Annie Mine. .
4
54
4
*
*
?late
12
A. Gartim Fault............. ...*.*******************
Be Abrigo Linestone..................................
¿late
13
A. Naco
B. Garnetized Linestone.......
,'late
1:Ate
14
15
.
**
.
.*
57
A. Abrigo Limestone.......................... ...
B. Tertiary Granite and
cuartz
r_,rite
Granite
A. r'hotoraicroqraph of Biotite
A
56
i
*
.
rr
.
B. Photonicrograph of Rhyolite
:Iate
16
A. ?hoto-ricrograph of Biotite Granite
B. Photomicrograph of Tertiary
?late
17
A. Photomcrograph of Polished --)ection of Ore from
Content:I.:Ai Line..
.
.
B. Sane.
*
********S W.....
?late
18
....
.
4
... .
... a
A. Photomicrograph of eolished Section of Ore from
Contention ine
. ....
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!Si.
....
**
....
**
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s
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4,
.
61
IT
ABSTRACT
This report describes the geology of tie Contention mine area, a
small portion of the Twin Buttes district locatle. in Piria County, 26
miles south...southwest of Tucson,
1
,rizona.
The sedimentary rocks exposed in the area are the Bela quartzite
and Abrigo limestone of Cambrian age$ the Martin limestone cd' Devonian
age, the :_scabrosa linestme of Mississippian age, the Naco fr'rnatien
of Pennsylvanian age, and a quartzite of questi-nable rl.etaceous atze.
The sedimntary rocks are intruded by a biotite granite of probable
Tertiary age.
Dikes of granite, rhyolite porphyry, and quartz diorite
have intruded both the Tortiar., granite and the sedimentary roc:-s.
The formations were intensely faulted presumably d ring thti
Iara,-lide revolution.
Faniting took pince in three stages :
before the
Tertiary intrusion, after the irtrusion but before mineralizatirm, and
after nineralizatLon.
The ore deposits are of the contact -letwiorohic typelvith replace-, nt of favorable liyestone beds.
The mineralizing solutions were
a? arently derived from the Tertiary magma.
Localization of the de-.
2081t8 was mainly influenced by pre-mineral faults.
The develf-sment of
contact silicate -.iner.Lls has been extensive, and the metamorpAsm of
the sedinentary rocks, intonsc.
etal production has come from tac nines, the Minnie and the Contenti-n.
At the 'Annie mine the ore nineral was nainly chalcopyrite,
Nliereas at the Contention it aas predoninantly sphalerite with little
chalcopyrite.
A search for ore mic:ht locate small deposits, especially
along the :::organ or Contention faults.
ININODUCTION
Method of Study
The field work on which this thesis is based as started in
October of 190 and was continued until April of 194% ApprxiatelY
eight days were spent in the field each month.
The area covnred by-
this reo't tocter with the ad,lacent area tr-, the solltheast described
by iia 'old
Jhi
was inpd togographicaliy by
ue
the n ane
iiteodb Harold, The geology of the Senator Loran mine area, Twin
Iluttes, Arizma, Master,s thesis, Univ. of A.rizr_ma,
table
t .i5
telescordc alidade.
?ortion of the wrrk.
iitco
The geolf_:,gy
and the author coopera
as ser-
ir
-sei on tU base
nap by ,cans of t::te intersecti,-n method with use of the 2rvnt-n connass.
Trios ,lere nade to nearby localities for the our-,3cse of -ore precise
stratigraohic correlation.
The igneous rocks were stiied both ;leg
sc:Ticary and nicroscopically.
Literature on the area h s been con-
sulted, and, although s!etchy, has been of assistance, especial:1y with
regard to El ning history and producti-n.
Acknowledgments
The writer desires to express his apreciAtion to Dr. B. S. Butler
'or As valuable advice and innumerable sur7e ti.ens; to rtr. 7. D. Wilsor
.
for maps and inferrlation concerning the surrounding area; to D
:;toy-anon for his helpful discussion3of tie stratigraphy and paleontology;
and to Dr. -.:. N. Sho.ct
rh
c-,cperated in t
Pe -0:graphical deten-inatinns.
Fay contributed info7na ion concerning aining and production in the area, and made available maps
nf
the Contention mine.
The e,,Teraticn of Harold hitocnb in the preparation of the topographic nap and hi s as3istanee in fa' iliarizing the writer with the
stf'aLV;rapUc cniurn i
fully appreciated.
The author is also vevy gmtefll to those whe-se patient eritieisns
have aided in the eompleti-n of this thesis.
rvrT ADMVD
IL-AL,.
GilOG:tTIPTIT
Location
The Contention nine area is located in the Twin Buttes mining
district 26 7113s sr-ith-soctlwest of Tucson (see plate I).
The area
zliay be reach2-d fron Tucson by either the 'N in Bute s road, --lhich naw,es
through the San Xavier minn district s--;thward to Twin Buttes, or
U. 3 lighway
9 to Sahuarita t4en southwest on a well maintained dirt
road to t,le Nin Buttes road. \; The area wa
connected by ran_ in 1-05
to what is now ths Southern Pacific's Nogales route.
This branch has
been abandoned for nany years.
The area described in
this
thesis consists of five square miles
iedíateIy nort::zwest of a northeast line through the Conteuticn
Twin Buttes, a wIall sottl-m-nt inhabited by several Cexica
is a mile to the northeast.
:Aim e
The clinate of the area is
ern Arizena at intermedia,,
a !lean annual
npe-at-ore of
humidity of h5 per cent.
iuch Vv. same as that throughout souttl-ttions. It is a warm, a-id cli-ate vrith
r, a rainfall of 1
incles, and a
The winters are mild and the sarmers hnt.
The
principal rainy seasm comes in July and Augt.
Topography
r:.egiunal
The Ccaltortticn dne area s 'located about five miles east of the
Sierrita NountaIns, a rather lax and unirwesAve range with a lmg-th of
14 miles northeast-sr_sutimest, and a width rarr_'1'y attaining four rdles.
The 3ierritas rise 201:0 to 3e0C feet
above the surrrYanding plain, ne
R9E
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Index /Ìiap Showing fhe Location of Me Confenfion line Area
\J. RI4E _r RISE
RITE
RIOE r
(RI6E. .isRI7E
J RI2E J RI3E y,,
s,e.
,¡ ¡
ï'
yT
r R TENDE
___-J
OAIA,P/
=-0ti4
PRIVATE LAND GRANT
BOUNDARIES
MINING DISTRICTS
IA
11
VIM
U.S. MINERAL MONUMENTS
6AC4 Al OA T
U.S.G S. BENCH MARKS
Scale
1
o
or
o Miles
3 --r' -2-,,
+c,,l
Ns,3
Ws'
?or.
ú
LA /Y
GRq/vT
lANF
.%
áI I
-
oa 1('12+
IS - r/ le+-JS-,F13
+ - -- - '
'Y=.
20 21 22
''/l1-tLicr83
I
24
:Ansome, F. T., are deposits
- 3ierrita Mountains, ?ira County,
U. f3. Geol. Survey null. 725, p. hO7,
- iopographic map, Twin Buttc,s quadraftgle, U. 3, Geol. Survey, 1'42.
est elevaton being 6206 feet.
Sloping gradually to the east tcard the Santa Cruz 7A.. er is the
indoaating pedimmt on Iltich the ?win Buttes district is
4,1
s.
The sioning sl:-face, as is characteristic of mountain pediments rf arid
cut -n the granIte bedrock and arlrered with a venty.'r of
gravel and finer aI1vìu.
It is dissected by s alloy wfs'tes and arroyes.
The prominent hills in the area under dAscus-,ion are eornosnd of re1at4vely
resistant rocks
mainly limestone and quartzite, blat stand ab ve the
pediment.
The Ulis
the near by San Xavierh di8triet are cosed lar-el- -f
4 14,yu- 0 L. N., The geology and ore deposits of ne Helmet Peal: area
2ina County, Arizona, Ph.D. thesis, Univ. Arizona, p 91 1912.
.)aleozcic linestmes.
easily
The saddles and surrounding plains are
on weak,
eroded maris, shales, and sandstones of late Paleozoic and L',esozeic
age, and on "granite".
To the south of the Twin Buttes region is a series of ratier prominent hills of Tertiary
j Tolcanies.
LccaI
The relief in the Contention area sIigt1y exceds 200 feet 'see
nlate 1).
The highest hill is bar-ay over 3T
above sea level.
laost pronlment feature of the ara is a ridge trencYmg amroxinat
west nP,
the southern limit.
The
east-
Tt is 0-r:41-Dosed mainy of ?ennsylvanian
quartzite and epido ized Cretaceous (?) _quartzite, which strike with the
trend of the ridge and dip steeply tn tie south.
The saddles in this
ridge are deternined by non-resi tant granite.
To2ographic develv,onent is related to falllting.
The valley north
-
of Gladstone Hill is delineated primarily by a zone of west-nortl-rwest
faulting in th
Naco quartzites
plate 1).
Structural contra is also well s-,Town by arrcryos immediate.ly to the
west of the Contention nine.
Tlere the rectangular stream pattern (ES-
definite control by faltin,7.
Apparently only those fractures
hich have -undergone sli7ht garnetization affect ne stream dweloprent
to any great degree.
Post-mine ral faits and dertain of the pre-rlineral
faults are included in ,his group..
The more heaily garnetized faults, ort
the other hand, resist erosion and tend to stand (-A,, on ridge and hill
tops.
his is shown near the, Contention nine by the northwest trending
garnet zone.
The area surrounding the sedimentary rocks is composed of relative
unreststant granite and of
dioriti, dikes.
:Tereus, someWhat more resistant quart.
an-' attributes sone of the topographic develepment in
- Brown,
L., Geologr and ore deposits of the Twin Buttes district,
thesis Univ. Arizona, p.
1926.
this section to the effect of tese dikes.
The hills il,lediately south and east-s-rutheast of the Minnie mane were
developed from the hard Niddle Cambrian Bolsa
Uoper Ca.brian Abrigo
uartzite and silicified
o
CHAPTER II GiEL GFarmY
-,edimentary RoeP.S
Ca-lbrian
Belsa Alartzite
The Bola quartzite represents t:c loxest stratigraphie unit of the
se'uo-,c!e in th-, Contention mine area (se-1 plate 4).
reous, comnact, and poorly sorted in nany of the beds.
The grains range
sub-angular to rolindd, tie na4ority being sub-rounded.
-Iostly of white to colorless quartz.
The pinkish color of
due primarily to impurities in the ce-eming silica.
-Lie formation, which are not exposed
6
Ilayuga,
in
Beam,
They are
he 'roe- is
The lower bed s of
this area, are con',1oTle-ac-'
11. op. cit., p. 13, 142.
and, according to Browny? quite ar!:.osie.
7
it is vit-
The lower strata 7rade
op. cit., p. 13, 1926,
into be.ds of finer texture.
Contention mine area.
r the
top silty beds Dredoninate in
Fret silfaces of tle quartzite are
Ash-gray with nany tan or dark gray :Layers.
wrially
the
Ii7ht
The rock in several
,Taaces has a dark brown color which ay be due to 'letamorphism of the
silty beds near the too of the formation'.
weathering has In any ID:laces
da-ened t e o:;,ginal colors and red_ccd Uhe vitreous apDearance.
',he weathered surfaces exhibit rin'te
it ,ing in the ce nnting
natc-ial.
13g.d Ting is indistinct in -Iany outero-)s,
-lore weat-ere-' surfaces.
irosshd ìn
is e-phasized on the
iîs nod ac 5,33reral zones.
7
Fracture surfaces are amooth breaks and somewhat consi tentiy oriented
1th respect to bedding.
This feature , together with color, aids in
differentiating the Bols- from certain quartzite beds in the Naco formation which are in other res2ects similar.
Outcrops of Bolsa have a definite orange or brick red color ,Ach
contrasts with the surrounding, more subdued colors
other rocks in the
area.
The thicker outcrops aro cliff-forming and show a marked influence
upon the to-:3ography.
is conposed
*
The hill immediately to the so'.'th of the
y of this resistant quartzite.
innie mine
posìre s are also 1,re8et
the. Contention mine, but many of these are too small
In the vicinity
individually to have much effect upon relief.
A complete section of the Bolsa quartzite is not shown in the
:7?
Contention mine area, but according to Ya aga° its total thicnes in the
ayuga
N, Q, cit.
1n2.
San ...avier distict, ten miles to the north, is approximateTy 1, 30C feet.
i3rcMfl9 cîte
' Brown,
J=7.
thickness of 700 feet to the Bolsa, 4 feet to the
7.:T. , Ta. son 17,ountains, an Arizona basin range type,
-0. 711, 1939.
Pir
Geol. Soc.
Ane-ica Bull., vi.
sandstone, and 300 feet to the Ccchise fr-r-ation in the Pieachos de la
Calera.
The most comolete exposure in the Contention mine area indcates
ari approximate thic-ess of 50C feet.
No fossils were fo,Ind in the Bo'-a quartzite, consequently its
correlation is based wçon lithology and
tratigraphic position.
The general characte . of the Dolsa quartzite, with its relatively
co7tr e-grained lower .ortion, its cross-bedding, and its irregularity of
grain, suRgests a rather sallow narine deoosit.
The pee-Cambrian sur
face was probably co,7posed of granitic rocks whic',. have contributed to
the arkosic character of the lo4er 17.eds.
Sandstone and Cochise For-ation
einer the i-a sandstone nor the Cochie foratìon -vas recog
nizod in the Contention nine area.
The lower part of the Abri
for-
nation in the area -lay represent both the _Ina sandstone and Cochise
rnation.
morphism.
They cannot be recognized by lithology owing to intense meta-
The strata imediately overlying the Bolsa quartzite are essen-
tially identical with the brigo formation found st-atigraphically higher.
Other than separation into the Bolsa quartzite and Abrigo formation,
differentiation of the Canbrian into lithologie subdivisions is not
feas:
ble in the Contention mine area
Abrigo Forr-ati
In the Contention 7Cne area the Abrigo fo, ,atien overlies Vie Bolsa
quartzite with apparent conformity (plat- (,) .
It is composed essentially
of thin-bedded, iure lirestone with shale beds in the looe
part.
The
limestone is la-Anated by cherty layers which in unnetamorphosed rock
stand out on the weathered surface.
ihere metamorphosed, however, the
limestone layers have been silicated to such an extent that this differential
eathering shows little development.
The color on the fresh sur
face is light brown for the ch rt layers and dark brown for the lirlestone
In the shaly lower portions of the formation the freshly fractured sur-
face is gray to grayish-bro.
Also present at different horizons (fron
100 to 150 fe,lt stratizranhically above the base of the Abrigo fornation
are several beds of quartzite rangin
feet.
in thickness from 18 inches to
These have a close rese-blance on both the fresh and weathered
surfaces, to the underlying 7iolsa nuartzite.
Hower, they are not ,ner
sistent, but pinch out or thin and thicken along the strike.
The lime-
stone has banded, dark brow, weathered surfaces where metarlorohosed.
Southeast cf the 2;innie mine it Is not highly altered and shows rather
blue-gray fretted surfaces--the fresh f-acture being, light gray.
Ohert
layers are les- com 'on 02 entirely- absent, ccnsenuently, the lar.inated
texture is not epearent.
Several areas of :ib'igo to the west of the
Contention mine s'icca li-ht to r:odeeate enidotization.
Although no fossils were found in the Abrigo foerlaticn in the Contention --line area, they have been deecribed from ots-er Mean ies and indicate an Unner Caribrian age.1
10
Stoyanow,
0
Correlation, as in the case of the Bolsa
op. cit., D. 467..4169, 1936.
eueetzite, is based on litholog,y and straulgranhic nesLtion.
The two outerons of tee Abrigo feenation in thn area are southsoutheast of the :ineie mine and west of the Contention mine.
The tniernees of the Abrigo fcreat4nn is about 330 feet in the 3an
Xavier district.
11
12
Uayuga,
Brogn,
cited hnc feet in the Ileac ,e
de la Calera0
op. cit., ? 15, 104.
H., 00. cit., p. 711, 1934.
Southeast of the !Annie mine the section is abr .. ut 50C feet thick although
there may be sone duplication by faeltin7.
The follewIng section of the Boise quartzite and ;e_
fornation
is located apnroximately sixteen hundred feet west of the Contention eine4
It was measrred in a norteeast direction.
abigo Fault
Abeigo Formation
..
Feet
51.0
1.
Concealed. .
2.
Limestone; laeinated by tan limestone and gray chert;
fine to medium grained; thin bedded (1 to 2 inches);
silicate and carbonate ceeent; epidote rare; forms
slight ledges on the slope serfaces, weathers with an
orange brown color; no fossils....
12.5
..
10
14,t
Limestone; la -Mated dark Tray and brown ii-stone with
bown chert; ve 'y fire grained; t=in (3 to 6
inches), flat bedding; enidote co-on; resistant,
fr_rring small ledges or ridges on slones, w-athers
to green ard black pitted c-rfaces; no fcssils......
11.5
Li-,estone; la-linated by brown 1-1.-les,cne 1ayers and
litlt brown and vay chert layers; fine grain
thin (2 to 4 inches) , flat bedding; e.)idcte conron,
nore resistant than '117, weathered surfaces are
dark brown and crunbly; no fossils............ .. .
Concealed................................................
J.
f.
9.
13.5
23.0
26.0
5aía#1i.,.. ..*-00.4.00.4..4wilpelOWO.,..olo,.e
Sane as if4 but less resistant__
r*
21.0
COnCealedr*ar*******4.ror****.************.****** ..... ***
6.0
r
aartzite; gray.; very fine grained; thin C, to 2 inches),
flat and distinct bedding; silica ce,, !ent; impure,
abundant black inclusions (unidentified) with rat.-er
definite boundaries; non-resistant, slope for-ing,
vmataered sirfaces are dark brown; no fcssils.......
Bolsa 2uartsite
10.
COnCealed............v....**..... ..
11.
--'!uartzite; light gray; vey fine grained; thin (2 to 5
inches), flat bedding; comr071117 mttled with black
.
12.0
...
inclusionS of indefte boundaries; ridge forming,
weathered surfaces are pitted and dark gray 41th
orange stain; no fossils...
Total
43.0
222.0
Grani te
Devonian
artin Limestone
The Liartin 1r stone was not fund in sedimentary contact with the
Abrigo in any part of the
contact was not detemined.
conformably upon older fr4,
consequently the nature of the sedimentary
At other localities the :artin rests disAons.1-3-14-1
II
:ayuga,
N., on. cit., p. 17, 1142.
3toyanow, A. A., of.). cit., p. 4I, I.-1'0), 1c3-'
Ili
.
.a.eozoic paleogeography of Arizona, Geol. aoc.
e-ica Bull., vol. 53, D. 12)6, 19t2.
The :Jartin limestone is crvvact da-_-!
gray, medi_:a gray or buff.
The expoaure of :.artin ltncutone west of the Contention nine cont.7.ins or
of the Helmscnaria-Cladopora coral reefs common thmughout the Devonian in
southeastern Arizona.
A si7lilar reef is present one hund:ed feet wee of
the Garnet -Aleon nine.
Both reefs s' ow intense silicification.
exposure west of the Contention
In the
-',ne several -eds of llrvstone strati
craDhic11y above the ref are blui-ffray in color and have a--)1, n4tic,
almost 1it'o7roph1c text:res.
iben metamornhose.' t-7.e linestone is Te.Ate,
a lary, fine- to ziedi-1,-Iraini. 7arOle.
11Pla7 bd EXhibit veinlets,
The beds
strimmrs and i_.--7eza1ar nasses of silica.
'-o
ange in thic'ness
6 incl-:es to 3 feet, a dstinctive feature when co:.pa3,-ed to the
Ahrio or the nore massive :scabrosa.
The bl'ff linestone,
ch nakes ui the nid le portion of tsle
tion, weatlers to a ',èan sandy surface.
The gray oortion be ones fretted
with a dark gray color on the 4eathered surface.
Accordin7, to Stoy,-..nowl
the corals composing the reefs are
16
Stoyanow,
Correlation of Arizona Paleozoic formatirs, Geol.
5oc. America mal., v-1. 47, p. hr'y r736.
xarmnoria
A.*
woodman-3.
davids
ri
,T]dwnrds ard Holme)
,
profunda (Hall), iachyr rt llur"
ci do-mra 'orolifIca Nall and illitfield), and sone
others.
Becase of; the intense niliel_icatien of tese reefs in the Twin
rtes
area the only definite determination that can T)o. nade by the writer
is that of '2,1adopora sp.
.orrelatìon is based on -tis dete7m1nation and on
12
lithological similarity to the hartin in oV11,:r localities.
The
rtin )testone in the Santa 'Rita Mountains has been aeternin-
ed by Stauffer
17
to be 250 feet thick.
Brown13 cites 261 feet at Picachos
17 Stauffer, C. R., Devonian of the Santa 'Ata ountains, Arizona, Geol.
Soc. America Bull., vol. 39* Pp. 429-4330 1928.
13
Brown, .:. fl" op. cit., p. 7121 1939.
de la Calera.
19
type section at :ount iartin VIe formation
Tn
.:ansortes F. L.,
is 340 feet thick.
op. cit.* P. 33* 104.
The most completely exposed section of Martin lire...
stone (243 feet) in the Contention mine area is south of the Garnet
ine.
The west and northwest side of the exposure is cut
by
the ,artion
fault consequently the overall thickness of the martin limestone cannot
be determined. (See description page 14).
Mississippian
Escabrosa Limestone
The -scabrosa limestone in the Contention mine area is -assive and
coarsely crystalline with beds ranging from two to ten feet in thickness.
,I;hert lenses, 1 to 3 inches thick, and irregular nodules are abundant
several horizons.
at
The granular text-:,re, consisting of r-lonbic crystals,
is the result of -etamorphism.
The iscabrosa is in -iost places white or very light ,:ray on the
fresh ss,rface.
The feathered
surface retains the light color except in a
few places where it takes on a dark brown to black coating.
beds near the Contention mine arQ
definitely blue
Two groups of
or dark gray both on
fresh and weathered surfaces and contain chert lenses.
These blue beds
grade into the typical white ones along the beddim, whereas across the
bedding the color changfls are 'much rlore abrupt.
13
The Escabrosa li-lestone outcrops in a northwest trending belt to the
west and south of the Contention nine and in an area around the Garnet
Neon nine.
--last of the _Innie mine there is an east-west belt mtlich has
been traced past the Copper Queen and Glance mines.
The thickness of the 'scabrosa limestone in the Contention nine area
was not determined by measuring directly because of the lack of a co-plete
section.
The most complete one (inmediately southwest of the Contention
nine) is cut on the northeast side by the Contention fault and on the
southgest side it is in fault (?) contact with the Martin linestope.
description page 14).
Gee
The width of the outcro-1 extending southwestward
from the ContrIntion mine indicates a -1-Ininum of 650 feet and suf-7ests a
possibility of greater thickness.
90
Brown,
T1
oraeo
it was found
p. 712, 1931..
.
to be COO feet thick.
21 i
in the Tucson : ountains
In- Bisbee
the section varies from 600 to 600
op. cit.9 p. 43, 1904.
feet.
3everal fossils were fos.Ind in the 3scabrosa northwest of the Conten-
tion mine but owing to poor preservation Could only be determined as .1ssissipp4qn in age by Stoyanow92 .
22
Correlation is based upon -this deter-
:cersonal ccemunication.
nination and on llthologic sirlilarity with the Z;scabrosa limestone in
other areas.
The section of the art in and 'scabrosa limestones just west of the
Contention mine was measured from the nortleast to the southwest.
as follows:
it is
Contention Fault
:scabrosa Lincstone
i.
Limestone; gray; fine to medium c(7stalline; flatbedding (1.- to 3 feet) ; pure; 1ed7e forming,
weathers to rough, slightly pitted surfaces with
light gray color; no fossils.
*
s*
*
**
*
10.0
Zone of garnet ghich has, for all practi_al purPoses,
.conpletell7 replaced the limestone. This zone
cloSely foliC:Is the strike of the '''scabrosa limestone and Content-Ion
3.0
Lirlestone; white; coarse crystalline; flatbedling
04 to 6 rent); pure; cliff forming, weaters to
rough surface and white or buff color; no fossils
#
s
****Ss SOS It it
it
.1k
*so*
AV * V V
V 1. it
V,
-510
V 4.
Liriestone; blue, gradin7 to white a hundred feet south
of the Contention mine; medi= to coarse crystalline; flat-bedding (3 to 6 feet) ; rare s all
silica inclus-lons; cliff fcr-aing, weatlers to
rough surface 7riti no ao7,reciable change in color;
raro, silicified brachioncda of ississipAan
age*.4...oysloSetosel..0easp***wis-***
39
Limestone; light buff; coarse crystalline; flat-bf-Aiding
2 to 4 feA); pure; non-resistant, weathering to
a slight rougla surface with no change in colo, no
...
6.
#
s
**V
if `
V
*
s
s
L ,astone; white; coarse to very coarse crystalline;
flat-bedding (4 to 6 feet); Pure; ledge fon'!ing,
weathers to rough surfaces lt7ht gray, wIlite, or
buff in color; no
245.0
Limestone; blue, grading into white al mg the strike;
coarse crystalline; flat-bedding (2 to 5 feet);
contains numerous dark -,7ay to blue cliefit lenses
parallel to bedfling) 2 to 6 inc'fles
and
from a few inches to 6 feet long; cliff forming,
weathers rough with a little darkening of color;
no fossils..
...**41*.ter ocwse **0001,V.0411P.Ps
40.0
Limestone; white; coarse clistalline; flat-bedding
(3 to 6 feet); pure; non-irosistant, weathers to
sno=7)-th or sligtly rough surfaces, light rray or
mrLite in color; no
Limestone; rhite; coarse crystalline; flat-bdd'
to 6 feet); pure; non.-resistant; weathers
slight rough surface- due to the calcareous
nature of the rock.; white and buff color; no
fOSA1S*****ows.****=**Stsfew
Tilrbrosa Fault (?)
Limestone
oo
.. sass..***.is**.s.00MW
Tscabrnsa Total
57.3
631.0
15
Peet
10.
Limestone; 7ray; fine to medixn crystalline; medium
bedding (1 to 3 feet) ; caavion silia masses
(1 to
incqies in size); forms slight ledges,
weathered surfaces are slitly pitted and gray
17
or buff in color; no fossils........
*!estone; dark gray; dense, coact; thin to nedium
bAding (6 knoes to 3 feet) rarely silica string
el's; slope formin7, weatrhera to rougn,
12.
13.
ji ted
surfaces and medium gray color; no fossils.....
2h.0
Limestone; gray; finely crystalline; thin bedding
(6 to 13 inc_es); comflonly contains silica string
ers and masses; ledge forning weathers to a I-Icaerately Pitted surface and ve -y light gray or buff
color; no fossils...
" ..4.414110011
o em.110
21.0
Limestone; darl:. ?Tay; dense, hard; thin to medium bed
ding (1 to ft feet) ; some epidote; resistant-- form-
ing small ledges, weathers to rouh, pitted surfaces and light gray color; Hexagonaria-Cladopora
reef, 2 to 4 feot th.ck in the rile of -176715757,77....
limestone; very llptt gray; finely crystalline; medt_zm
bedding (1 to 3 feet); silica rasses up to 1 and 2
feet in size common; non..resistant; weathers to
rough surfaces and 3ht gray color; no foils.,....
64.0
Iimeitone; gray; finely crystallie; medium to t'thi bedding (4 inc-,lez to 2 feet); rare ,4 green incllIsions
of indefinite boundaries and noe frelucnt silica
stringers and matase (1 inch to 74 inchs :',A1 size
.nore resistant than
weathors to a buff celcr; no
16.
Li
stone; light gray; medium grained; thin bedding
, to 13 inches); pure, mtth rare silica stringers
and veinleta; slope forming; weathered surfaces are
rough and of medium gray color; no fossils...........
31.0
To4-11
Fault
Pennsylvanian
Naco Fortion
The original "Naco liestone" a
2ansome
L., op. ci
p ODOSed
'?ansorl
inclrded all
_904.
t,le Paleozoic roe!s stratigraDhically above the Lis,Assiwian and con-
tamed faunas representative both of the
period.
and-
the i'ermian
term nNaco formati-7-n" as Nsed in this ria7v-rt includes on
that portien of the "Naco limestone" which contains Pennsyavanian fossils
in other districts.
24
Correlation is based whory upon lithology as
24
Datler, r. 3., aison,
D., and -asoi, O. A., Geology and cyce
denosits of the ToMbstone district, Arizona, Ariz. Rur. lanes, Geol.
Series No. 101 Bull. No. 143, pp. 14-17, 19*.
paleontological proof is absent.
No evidence was found In the Contention
mine area to s-J-fgest tr-le rwl,:sence of Permian strata.
The contact betecln the 7scabrosa limestonP And the Naco for:aation
is located between those beds w-ith faunas of lassissippian age and those
with faunas of Pennsylvanian age.c'
4-0
Butler,
Ilson
A conglomerate, thought to be the
and asor
o". cit.,
1933,
basal bed of the Naco formation is rtortd by Whitcomb26 as °ecru-ring in
26,
Alitecnb, Harold, The geolo, of the Senator L'onlan mine area
Buttes, trizona Y.S. thesis, Univ. Ariz., 194a.
the northeast part of tie area stIld ad for hi
Twin
!:hesis.
At the base of the Naco, linestene nenhers arr, sinilar to those
the 7scabrosa limstone but thinner
interstratified with beds of
,4ornfels which weather to dark brown.
71.1h.er in the section the linestone
is finer grained, darker in color and mo-e thoroughly silicified.
t-le top it is aphanitic, hard, and gray to pale
renn or. blue.
Near
So-e
beds have a pink tnge and In any Places ',he li-test.one is dark brown
or black on the weathered stzrface.
Siliceous veinlets are comm n.
The
long ex7;osed wiz-faces are rough, fretted or covered with irregular pits.
The llomfels at the base of the 11-,estone suer.:ests an ori.,inal shaky
texture of the
ce: at most horizons,
:ost of the beds are laminated.
Colors of the 1a-11-lac are var,Ting combinations of gray, darl, gray, bluish
17
gray, greenish gray, and white.
Some beds are of consistent color and
show no lamination or rattling.
Yost of the hornfels layers are lighter
in color where weathered, but a few are dark.
are pure white on the weathered surface.
Several beds of nuartzite
One of these, a vitreous quart-
zite much like the Bolsa quartzite, has been traced almost the entire
width of the area from east to west.
The Naco limestone occurs as a wide belt which trends in an eastnortheast direction on the slope and in the valley north of Gladstone
Hill.
The actual thickness of the Naco limestone in this area is unknown.
L:ayu27 estimates at least 900 feet as the Naco thickness in the section
*
that he
exa Ined
. cit., p. 22, 1942.
ama.
in the 'Amaral
The
, in the Contention
area suggests a thickness of about 1307 feet, but faulting is pre-
sent; coisquently, an accurate thickness was not measured.
The following partial section of the Naco fornation was neasured
from north to south in a gully 2000 feet west of the Contentiongnine.
U-
4.4-ex
Forrat
cc%
2.
1.
5.
.*****
**
*
* *
**
*
ao
*
**
****
*
Hornfels; lizht gray; dense; thin beds (3 to 6 inches);
pure; non-resistant, weathered surfaces very light
gray or ahite; no fossils...-. .
. .............
12.0
Hornfels; gray; very dense; flat, thin beds (72 to 2
inches) ; pure; non-resistant, weathered surfaces
are smooth and light gray; no fossils........ . ....
3.0
Concealed..........
**
*
*****
*
.... ...
*
**
*
Linestone; ILcht gray; fine crystalline; thick beds (1
to 3 feet) ; contains some snail stringers of gray
silica; ledge-foin', weathered surfaces are gray
to light bluish gray; no
*
o
7.0
18
Feet
6.
7.
8.
9.
Hornfels; light blue; very dense; flat, distinct, thin
beds (1 to 3 inches) ; pure; non-resistant, weather
ed surfaces are smooth, and gray in color; no fossils........-
14.5
Hornfels; gray; dense; thin bedding (1 to 1 inch) ; pure;
non-resistant, weathered surfaces are snooth, and
white or bluish gray; no
7.0
Concealed........
Zone of resistant ga
M. Concealed. 11.
*
et and epidote... OOO OO ...........
Hornfels; light. gray; dense; flat,. thin bedding (2 to
inches) ; pure) non-resistant, weathered surfaces
are smooth and white with black specks ; no fossils.
......
13.
Hornfels; bluish gray; dense; flat, thin bedding (2 to
4 inches); pure; nonesistant (highly fractured),
weathered surfaces are light gray or white, and
15.
.....
.
. . .... ........
Hornfels; grqy; dense; thin beda5ng (1 to 3 inches);
pure; non-resistant, weathered surfaces are smooth
and light gray; no fossiJs............
18.
19.
29.5
3.5
3.0
6.0
Limestone; light gray; medium grained; flat bedding (1
to 12 inches); pure; non-resistant, weathered sur,
faces are bluish gray* rough, and gritty; no fessils.. .0
.
*
II
...
17.
-
Hornfels; pale greenish gray; dense; thin bedding (1 to
2 inches); contains SOMC epidote; non-resistant,
weathered surfaces are light gray, and chall7; no
IOSSilSee .... eeseeer*****ewireeeelie .....
16.
23.0
27. ,
C o n c e a l e d .
chally; no fossils-- ....
12.0
1,4
*
_
12.
14.
18.0
***
10.0
Hornfels; greenish gray; dense; thin, indefinite bedding
(1 to 3 inches) ; contains siall alount of epidote;
non-resistant, weathrrs bluish gray; no fossils....
1.5
Li-estone; white and pinkish white; fine crystalline;
flat, thin bedding (3 to 6 inches); contains
gray silica inclusions; ridge forming, feathers to
a cruìr1y, gray surface; no fossils
7.0
Concealed
4.0
Total
Uabi,,,,e Fault
331.0
19
Pe odan
No strata of Permian a
Contention mine area.
salaried I'm iian age, 'were found in the
There are a nusiber of exposures of Perman (?)
beds in the southeastern part of the adjoining area.
Those are
dis-
cussed by Jhitcorib 23
O.
r ld op. cit.
Cretaceous (.) Quartzite
The formation described as Cretaceous (?) quartzite is found in the
southernmost part of the Contention nine area.
A greater portion of
Gladstone Hill is composed of this formation.
The elastic nature and thin-bedded appearance distinguish it from
the other rocks of the district.
2,
-
,,Lansome
described a
F. L., Ore deoit of the Sierrita _ountains, J. S. Geol.
.2:',..urvey Bull. 725
p4 )f26, 1929.
;Is a calcareous sandstone which has been esidotized and silicified
The sand
rain are fines sub-an alar to sub-rounded, and rather well
ssrted.
_c6s-bedding is well developed at many- horizons.
Te fresh
aurface is gray or grenish gray and weathers to a brick red or rust
brown.
The green is due to the introduced epidote wAch varies in
quantity throughout the rook.
Dark gray to black sale is interbedded
with the quartzite.
Tho assigne nt of Cretaceous age to the rock is open to question
and therefore is only suggestive.
writer.
No fossils were observed by the
Lithologio lly the formation is dissimilar to others
seen
in Vie area or nearby ar-isr..
Outcros are lintted on all sides by either igneous or fault contacts, consesuent3y a complete sectitm is.missins.
The extent of tbe
2C
axp,sure indicates a thickness of over Y-0 feet,
quartzit was
The folicrAng partial section of the Cretaceous
measured qrmthward on Gladstone Hill 1100 feet west of the old Y,organ
shaft.
Granite
Cretaceous ( ?) Quartzite
1.
eet
Quartzite; bluish gray; very fine grains of varying
size although uniform in some thin beds; bedding
thin to medium (6 inches to 2 feet) ; cross-bedding at sane zones; silica cement gdth minor
amount of epidote in some of the beds; ridge form,
ing, weatered surfaces are brick red to dark
brown in color; no
*
it
.
*
*
* *
Jr
2h.o
**
*
*
16240
("),uartzite; dark gray; fine grains of r,,alar size;
bedding thin (1 to 2-7:y inches) and flat; silica
cemnt; no inclusions; ridge forming, weathered
surfaces are bluish gray and gritty; no fossils....
Cluartzite; gray; medium grains of varying size; thin
beds (6 to 13 inces ) ; cross-bedding common;
to
silica and some epidote cent; a fr small
3/4 inch), black inclusirms; non-r esistant, weath
ered surfaces are crumbly and of dark brown color;
no
vr
.
33.0
,,tzite; light bluish gray; fine grains, slightly
varying in size; thin beds (3 to 9 inches); some
cross-bedding; silica and abundant epidote cement;
rarely contains small, black inclusions similar to
ridge forming, weathered surface is .
those in
bronn or bric red and crumbly; no
1St 00110
V
COneealed*
7
Qual,zite; light gray; medium grains of nearly uniform size; thin to medium bedding (3 inches to
I foot); occasional cross-bedding; silica and
epidote cement--the epidote ma!:_ing up to fifty
cent of the cement; non-resistant, weat'Aered
surfaces are brom or brick red and crumbly; no
W.*
3.. .
41
4.
73.0
e
a
pr
fOSSilSoarwee*O011****40...****010.
Total
Fault
a
26.0
354.C,
A//ut.,/urn
Gal
1,
\/ rT_.
ò°<
Tq d
:---\.
1
i
/
.l
"'
\¡
4. Iv
\
\%
%/
, iT 9
+ /\
1
/\
I
\1 "
I
+
»T9d
+
+
F
i\
++ /
/
/1
\ / \ /\
\
WWI
i
-, 1 _
\7
QUarfzife
. .¡
f.
-
i
.
( -
/
.
...--
\/
+
iI
/
+
tf\ l,
}.-' -
1
L
1
1
`' :` r,
.---\::-.-:/:.
,
1
.
t,
1
r-
..
-
Naco Lirnestone
-.
I
T3
\.
T
t
I,i
_L
Escabrosa Limestone
/
1
{
1
[
%
T ¡
1
f
1
/ .r r-z
-r =` 1
1
.__
T
\ / / '-'-)
t.
:
Martin Limestone
Abrigo Limestone
_a_-1-Z--1--z-_
z
.- ,'-
1-
`-'/..
Boise Quar-tzite
Generalized Columnar Section
for Contention Mine Area
Scale lin. = 500f
Plate 4
21
Tertiary and fuatornary Deposits
The Tertiary and -,paternary deposits
consist of small scattered patches of
the Contention the area
caliche"; lithified conglorerat-
ic -ate-ial; a large amount of unconsolidated gravel and talus; and sand
of the arroyo botta-,s.
The unconsolidated gravel and talus is by far the -,,ost prevalent of
the Cenozoic deposits.
It covers nany of the slopes so conpletely that
nuch of the un&r1 In; structure is obscured.
The largest area overlain
by this naterial is in the eastern part of the valley to the north of
Gladstone Hill.
Here it covers all the bedrock except on the arroyo side
and attains thicknesses up to 15 feet.
In other patts of the area the
gravel is less ext-nsive and thinner, rare1y exceeding 6 feet in thick.
ness.
The gravels were derived from the higher country to tl,e west where
granite is the predominate rock and fro- the sedientary and granite
hills i'ediate1y surrounding the area.
The internittent, but powerful
noveents of water down the relatively bare slopes are -ainly responsible
for nost of the accu--,lated gravels.
A minor amount of the gravels have
traveled only a short distance from their source to their present position.
The sand in the arroyo bottoms is composed mainly of naterial derived from tIle rapidly weathering granite to the west.
Feldspar is the most
abundant constituent, followed by quartz and mica with ninor anounts of
agnetit
and other heavy minerals.
igneous Rocks
General
The Sierrita 3,Torantains, lying to the west of the Contention nine
area
are r ade up mainly of plutonio granite.3°
The rocks on the west
22
cit.,
`'e, F. L.,
0s
1°:21.
and limes on
ands tones,
to be older
n intensely ne tamorphesed and deformed and app
have
ne large rnass,
intensely r.etamor$aa sed rocks on the east.
}Ian t
es of granite surr un
,
y with t
ore.
ìe_itliatco
z
coarse,
believes
Eckel,
County,
c>:.
top
Aayu
at
the
:an ral
all area
of
nnv. Ariz ! P.
,
;iansone sugge:
`i and
idea of a st,
14
nw
nce upon the ir t,
e the gene
at
1910.
-ir=f.1.it
=e
f
e
ler..
r
c redeú
agi ees with
r.:
_C*
a_
Tffin Buttes
r and
B.,
a,
ly related
tne 2win Buttes district are s4LI,
sill.
*he'
k,
_sing his
relation
.
_
r.`iT,5test-
exist
e presence of
k.
2an..s
d
LS
e
cut
412, 3921.
F. L.,
and
ably
layuga,
confirmed t, s and correa
etaeeous i 3c`.w cf
el x
'ost-C _.=et
e
.'",,, cp; cit., (Gcc3,
ï u;l. the :: .
i'
robably
the
1
i ,
7?, 19) , 2.
c} rocks
1=
. favored d a
cit., p.
ec
age for all the gra'
n
g2ner-al Hill
23
Brown-5 was doubtful as to the age of the granite in the Twin Buttes
35 Drtwn, R. L., cp. cit.
district.
Geol. Twill Buttes
pp. 18-19,
He states (in speaking of the granite):
It seems to underlie the nre-Carboniferous quartzite
although the contact is very unsatisfactory for the determination of the relations. Its relation to the older rocks
of the district seems to indicate that it is pro-Carboniferous and its lithologie character suggests that it is DreCanbrian...Its coarse texture and gneissic structure suggest
that it is an older granite than the others in the region.
On the other hand fresh specimens from shafts sunk in this
granite yield a 'ray rock-which is quite similar to the
granite intrusive into the li-estone of Veen Ji11.
-.14e recorded descriptions and the geologic setting, togetner with
exanInations of the present writer, seem to indicate a correlation between the granite of the San Xavier district and that of Twin Buttes.
The irregular contacts between the granite and the sedir-entary rocks,
the lac', of evidence to indicate a sedinentary contact at any of the
locations observed, and the probable genetic relatirn with an intrusion of post-Cretaceous age, all point rattler stromly to a post... Cre-
taceous age for the granite of the Twin BI:ttes distrint.
The contact
west of the Contention ml_ne is of pronounced irregularity and certainly
does not appear to be a sedi-eentary contact.
South and soutest of
Gladstone Hill the granite has very definitely intruded the Cretaceou
quartzite.
rol
The exeosure of a oractically ho-izontal Bola-igneees con-
tact in a prosDeet pit southeast of the Contention mine &tows no basal
conglomerate, nor even a tendency toward congloneratic nateral,
Bolsa quaetzite.
On the other hand, the contact is suvestive of either
intrusien or lo a angle t"..!-
36
Brown, a.
L.,
in the
op.
Listing.
-Irown36 describes ne granite as having
34 and 35, 1926.
intruded the Carboniferous limestone at the Copper Glance and Copper
21t
Queen mines.
The possibility of soue pre-CaMbrian granite has not been overlooked.
However, there has been no evidence observed indicative of that
age.
Biotite Granite
Megascooically the granite of they Contention mine area is nedium
grained and dark gray on the fresh speci-en.
It 'meathers to a tan or
brown and comtonly presents a rough crunbly surface on the hand speci
Quartz and orthoclase are the predoninant minerals with subordi-
men.
nate plagioclase.
Late
Bio ite is the only ori'linal mafic constituent (see
1611%
Examination of a thin section shows subhedral to euhe ral orthoclase and plagioclase, both altered in varying amounts to sericite and
kaolin.
Biotite has been lirgy altered to chlo-Ate.
Crus!led or bent
0..aAcr,lase lamellae indicate that the rock has undergone stress.t Quartz,
the last nineral formed as is usually the case, was found occupying interstices between the preceding -lineras.
The following table presents
the approxinate Dercent-,7,es of minerals which indicate a bi
according to Johannson's classification.
Table 1
Biotite Gmni_to -
_Zssential Linerals:
uartz-Orthoclase----------?lagioclase--------Biotite----..1.111.11.111.
Acce
44.05
13.0%
6.0%
Minerals:
Liagnetite--
Apatite-
1.05
-1.0%
(226P
ite
cationt30
Class.
Quarfeloids-mafides
92%-3% (Class 2)
Plagioclase (Andesine) - (Order 2)
Quartz in quarfeloids - 47%
Orthoclase..plagioclase
62.5%-37.5;
226?
(Fanily
Biotite Granite (with biotite as mafic min
37 Johannsen, AThert
descrittive petrography of the igneous
Univ. of Chicago zress, pp. 124-259, 1932.
38
ks,
:3ssentials for the microscopic deternination of
rock-forming minerals and rocks ir thin sections, Univ. of Chicago Press,
PP. 40-522
cit.,
226-22=2, 1932.
Intrusives
":Three
different
dike rocs are
a. The aE!e
pres
tions of these intrustves was indeterAnable because nowhere were they
observed in contact with each other or nutually in contact with a forma
'ion.
They have all intruded and are consequently younger tan the main
granite ylase, and the se-'ientary rocks.»
Only te more prominent occur__
rences have been recorded on the nap for mav of the outcrops are too
to be noted.
iThe numerous quartz diorite dies,
or
dil:e-14ke
the granite mass are confined to the centr.
This localization is ,41.1e to on
as es, ..7..ich are in
portion of the area.late 1).
of three ca is. The central area nay
consist of an inde,y-ndent LlasF, of granite, in nhIch ease it obviously
must b,3 either older or younger than the sr.--und* g granite.
If so,
there -would nest probably be other evidence, either compositional, litho-
logical, or structural
ence in age.
or
co,ination of tl-se, to s7.--zgnst a :14.ffer-
No such evidence was Observed.
Another- possibility is t1,4t these dike-like masses are earlier
solidified basic portions of the magma which were partly roJaorked
by
the
26
main granite magma.
This is suggested by the slla?e and distribution of
the "dike " as mapped (plate 1).
The exact contacts were Obscured by a
thin talus covering, consequently the actual outlines of these "dikes"
night vary from those mapped.
An actual exposure of the contact (plate
14B)
s observed in an arroyo 15GC feet northwest of the Contention
mine.
In this exposure the quartz diorite udikel appears yo-mger than
the 3 anLte
The third possibility is that the central part of the area is
actually a section of the hood of the banolith which subselumt to
solidificatir,n was intruded lyy the basic different4ates of VI- magrnP.
If so, the part under discussion is most likely the trough sectirm
judging from the relati ns.
However, it nay have been fal:lted into its
present nosition, during or after solidifir-ation and Penetratirm.
These dies are cut by quartz-bearing faults north of the Contention
-Ana and northwest of the Garnet Queen mine.
Biotite Granite
The biotite granite was noted at to places in the extreme south,west part of the area.
Both dikes cut the Naco formation and te nain
zranito nass.
rascopically, the rock is li7ht gray,
gray.
herini to a tan or
It is modiun grained but finer than the olde- granite.
ninerals are quart,
The rain
orthoclase and biotite.
icrosco-3ic exanination shs ubhedral
Iagior . lase and orthoclase.
The biotite prlsent has been largely altered to cüorite,
7-;e, plagio-
clase and especially the orthoclase have undergone imohnization. CPOSitiOflai3Z7 this granite is very similar to the nain intrusive.
It
2owlibly represents a sli-qtly more basic portion 7-Thich was intruded
o the hood shortly after the hood solidified.
tiens
are lì3ted below.
The approxLate per
27
Table 2
Biotite
Grani
:sz:ential lancrals:
Orthoclase
Plagioclase
AC
34.0%
31.0%
2
(Andes-I ne)
An-era's:
fir:at t
),uartz Diorite "Dikes"
The occurrence of the quartz diente
under "'Minor Intrusiv
has been discust;ed
sfi.
The rock is dark gray to black and weathers to a light gray or brown.
The texture is fine grained to aphanitic.
guishable.
Quartz, hooever, is distin-
The mafic minerals give the pronounced dark color.
Microscopically euhedral biotite and hornblende crystals: make up
roughly fifty oer cent of the rort.
Magmtite, amtite
Anhedral quartz is interstitial.
.d zircon are disseinated tn snail amounts.
clase is predominate over ortoclase and both are anhedral.
appear only slihtly altel'ed.
The anount of each constituent is as noted
in the follming table.
Table q
The ,:linerals
qual-z Diorite
1]s8ential lancrals:
Quartz
Hornblende--
Plagioclase (77t
Orthoclase-----------
33.0%
28.0%
20.vp
6.0%
3.0%
Acceso:
.inerals:
Apatite-Zircon
1.6%
1.0%
---
'9.U;
Rhyolite Porphyry-
The field relations indicate that tU rock is intrusive
single occurrence observed is
The
est end of the east.m.est valley
north of Gladstone Hill.
The ro&c is light gray to gray and contains about 20 per cent of
relatively large phenocrysts.
The 'lien-scope &lows that the largest
phenoc.ysts are orthoclase and the sral/e- are
iotite, quartz, and
magnetite.
The orthoclase occurs as euhedral crystals and is the most
plentiful.
The groundnaso is holocrystalline.
Table 4
Phenocrys s
2h
2Q_
'ssential Minerals;
67,05
Orthociase---
14.0%
Biatite--Plagioclase (An desine).
Accessory ,anerals:
1:agnetit
Yetar
The profound metamorphism Of the sedi-Aentary rocks was
browh
about by the heat and solutions released from the in-Lading magma.
The inure linestones were altered to silicates in many -.--;laces.
nure limestones li,ke the
The
abrosa have been recrystallized and now
29
exhibit
xi
coarse-grained texture.
Zscabro a outaroewest of the Contention nine.
This is well seen in the
!he sliales have been
mostly altered to hard, aphanitic, chert-like hornfels.
lany of the
shale beds of the Naco formation have been eeetamorphosed in ths nanner.
Ths)Cretaceous (?) quartzite, which was probably a calcareous sandstone
at one tiee, has undergone epidotisation to-rether with 5lIicification.
The degree of metamorphism depended on the proximity to the granite,
the available fractures along which the solutions could travel, and the
iermeability of the rock.
Heat, perhaps the most important factor influ-
the rocks, has been nuch -ore effective nenr the magna or near
ening the
-lajor solution channels.
llag-atic gaseous or liquid solutions, or both,
also had a great influence in the alteration.
These penetrated along
faults, through snaller fractures and pores, and not uncommonly through
bedding planes.
Stresses brought about by the intruding nag-a were
re
lieved nostly by fracturing arid probably to sone extent by granulation.
HecrystallizaAoe by pressure is not apparent.
Some of the pre-mineral
faults and -euch of the jointing of the area -ight be correlated with
these pressures.
The impure limestone beds found in the Abrieo formation were sillcated largely by alteration of the impure constituents with a relatively
smaller amunt of additive netaeorphism.
Heat was probably the nain fac-
tor that brought about the reactions between the calciure, silica, and
various impurities in the limestone.
n the whole, only a sear., propor-
tion of the :,brigo limestone in the area was altered eonpletely.
Lost
of the fornation 24-as affected only partially and has retained much of its
former chara cter.
Same additive metamorphism may be represented by the
substantial amounts of epidote in many of the beds.
Aluminum and iron,
if not originally present in the limestones, were brought in by the
solutions.
Euch iron was transported fron the magma
was available du
alteration.
entions and
This is evidenced by the Prevalence of
epidote and garnet in the relatively pure limestone near -ajor solution
channels.
Some of Vie lnestone beds of the taco formation were not as snscepti_ble to V:e scve_.e silication which altered limestone beds of the
brigo
forration.
ferhaini
this degree of sinicatinn was due to a dif-
ference in original impurity*
The pure
li,,estoncl
such as ,he --_scabnosa limestone and s.ne beds
by
of the 1Taco for-nation, mere netarorohosed in two different ways -
replacement and by recrystallization.
Epidote and garnet are the noe,t
abundant of the replace-lent ninerals although some ninor anounts of other
contact netanor?hic 5iIlcates such as actinolite, hedenbergite, and
wnllaston3te were present
together with
some magnetite and sulf4des.
-,pidotizati,n of the linestone was extensive in nany of the beds.
-
ever, garnet replaced the limestone nore completely and as a r,-le is
more prevalent.
both epidote and garnet were concentrated along bedding
planes and qaflor fractures.
It is very doubtful that t'le I1TeStOne
originally contained enough iron and aluminum to -ake up the quantitdes
of epidote and garnet present.
Additive .,e-tanatrLT-1 very probably
'ed the fiore prominent role of alteration in these beds.
This
is
nore clearly illustrated by the direct relationship of the epidctization
and garnetizatiJn to the structural controls.
This relationship also
emphasizes that -There there has been little or no addition of the neces-
sary constituents there is a complete lacy of silicate replacenent.
The recrystallization of the --:;scabrosa linestone and the oure lime-
stone beds in the Kaco formation has been nartial or coniplete in nost
cases.
Only snall portions of either have ,ascaned tie effects of this
31
form of metaorp isrr.
The agencies responsible for this recrystalliza
ti on were probably the heat and rather barren solutions that penetrated
these roo' s so thorouglay.
Although the solutions may have ben heavily
charged with elements upon leaving the il
they *e-e depleted by
their participation in the nrnatinn of the contact
inera1s at the
margins of the areas so extensively recrystallized.
The 7-3scabrosa lime..
stone
et of Contention nine was penetrated a/ang fractures nornal to
the bedding by solutions -Which had tray-led II? thn Contention fault.
Upon first striking the liriesone the substances carried in solut4-n together with the heat effected the garnetization whIch is so
along Contention fault.
zone to
redomiruuit
The sol-rtions then 11.1nt beyond th's replace-Tent
effect the recrystallization.
; The ore minerals are closely associated with the garnetizations
enidot-lwItions and _Vier silicate alteration.
The sulfides, as pointed
out in the section on ore deposits, may hay been deposited
,
silicates o- succeeding th en.
f
Me
th
si-lications on the other hand, eviden
ly took place d...Iring the initals normal -metamornhism that recr-stallized
the
major portions of the 1-;scabrosa limestone and parts of the Naco
fornation.
The
ait,in li-,stones although relatively
-re, -.vas not so suscep-
tible to the heat and hydrotliermal solutions and recrystalliza ion -mas
not so thorough nor so far-reaching as in the :scabrosa 11 -estone and
Naco formation.
The s all anount of epi±7-te throughout the rock -s
probably indicative of the minor effect of additive metamor2hism1
e shale beds of the taco limestone consi
influence of metamorphism.
fels.
ently show the strong
7..1,7 have been altered to hard
dense horn,-
The process was not complete in same beds where the shaly struc-
ture is still observable, tes ifying to the original character of the
rock.
1Viuch hornfels has been thorough
and intri ately fractured by
32
some deforiing stress during or after alteration.
It is this type of
rock that underlies most of the valley in which Nabigo fault is situated.
The Cretaceous (?) quartzite has unde-gone silicificatirn and
dotizAtion.
epi
The silicification may or -lay not have occurred d- ri9P., the
period of contact netanorpliism
That sirca Tris available at the tire
of netar-iornliism is s'aptin by the large luantities of contact silicate min-
erals in the pure li,',estnnw.
Jether or not encugh silica was available
is largely a matter of spectIlation.
The e?idotization of tie quartzite
is conte-nor-aneous eilth the epidotization in the other rocIrs of the arel..
'Me degree of replace,nent throu-hout the section of quartzite by epic:lip-be
varies considerably.
in 8°,73 beds
Adote is absent -prhreas in others it
may nalce up as m.ith as fifty per cent of the ce enting material.
33
CI-1ATR UI STRUCTITIZAL GE LOGY
General
The Contention mine area structurally includes portins of two
bloOks of sedimentary rocs and the surrounding granite.
These sedinon-
tary blocl-:s are similar to those that make up parts of the San Xavier
Aatimig district to the north.
In briefs:the area was faulted and folded
prior to intrusion; intruded by granite; faulted again, perhaps by adjustment of the hood of the stocIA penetrated by mineralizing.solutions; and
faulted again..
0 Butler, B.
Butler
sunmarizes the sequence of events durn7 t,he
Ore deposits as related to stratigraphie, structural,
and igneous geology in the -western United States, Part I, Sura-,Iary, Ore
deposits cf the western United States, Am. Inst. An. ;Jet. Eng., p. 226,
1933.
post-Cretaceous intrusions in the aoc lly 7,Wintain regirm as follows:
"The Laranide revolution opened with unlift of the
region accopanied by close folding and overthrust faulting along certain belts. This was folloaed by igneous
activity tilat locally at least mas influenced and directed
by the faults but in a broad wry- does not seem to have been
controlled by them. Following the igneous activity was tie
formation of steeply dipping reverse and nor'llal faults.
These were later than much of the igneous activity but earlier than the ore deTiosits and locally exerted an important
control over the -lineralization. Finally came the settling
of the region and a great systx11 of nornal faults, mainly
later tn the igneous activity and most of the vineralization."
The relationships in the Contention mine area show that the structural and igneous evolution coincides With tlis series of events.
The
sedimentary rocl:s-may have been cfverthrust, either before or after intru-
sion, along a northeast-southwest or east-Ilest direction.
34
_Ayua y
N
LI
op. cit., pp. 61-72, 1942.
proposes a pre-granite thrusting in the Mineral Hill ar ea and compares
it with that found in the Tucson Mountains by Brown. 42
The. Igneous activ-
H., op. cit., p. 748, 1939-
ity is apparently post-Cretace
Zae relative age of many faults in the area /ha s not been definitely
determined.
The age classification for the faults is pre-intnision in-
eluding those which occurred befof.e igneous invasion; The-mineral for
nose produced after invasion but before mineralization.
fault (plate 1) has been occupied by the
intrusive age.
The Thran
g:.a., consequently is of pre-
The Gartion fault is pre-mineral in part for it was
traced a o,..)ns:_derable distance into the granite to the northeast -,e_lere
it contains a thick quartz vein.
The Contention fault is also pre-
nineral and is offset by the Gartion.
The Nabigo fault is post-wlineral.
'lost of the remaining faults are probably pre--Ineral in age but a more
definite assigment cannot be -lade ,dthout further evidence,
The folding noted in the area consists of the eastwest trending
Simpson syncline (plate 1) and a similarly trending anticline both of
elich are present in the Abrigo li7estone.. The relations strongly
su7,gest a pre-intrusive age for these structures (plate 6).
A much lamer fold is represented by the north and south sedimentary blocs of the area, which ray actually be the flanks of an anticline.
72escriptive
Faulting
The following discssion
order.
-
suiting is in general chronological
Soo
.
A / /u.u.n
Qat
Naco
Cn
Quo/brr-wry Pennsy/vwr:Qrs
3400'
31CM'
.
.
t
.
I
_
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300
Abripo
fa
£6
BI/S4
C anr brion
EXPLANATION
.
SECT /ON A -A'
l
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Xñc/.j/ r'r
TOT,
/a0o FEET
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Cro n. to
T9
1
Qat
Ciorne
9
A
3600'
3700,
3800"
38 00.
Cn
IVE
SW
PLATE 5
llorgan Tault
!The Morgan fault is a hirrh angle normal fault trikthg generaly
N WO
which has brought the Cretaceous (?) quartzite en the south
zainst the Naco format'on.
to the so7th.
The dip at its western end is 7
degrees
The fault ha s been invaded by the granite intrusion at
two exposures along the strike, :flence is classified as pre-intrusion in
_vidently this fracture was responsible for the locar_zati7m of
age.
1,14neralization as shown by the closely associated garnet tolether with
some metal IC minernls in the western extr,nsion. \in the senator Morgan
area t:2.e rlineralization has been intense in the fault or in the nearby
roc s.
The If_organ fault is cut by a northeast trending fault east of
the Gladstone shaft and by a si7i1ar1y trending fault west of the shaft.
3oth of the ',org.r,n fault the Cretaceous (?) rocks have a solner:ly dip
of 63 to 7
degrees and ,... like IT _5° 7 to N 70
V.
The 1!a co formation
of the Gladstone block strikes in the sP-e di-ecti_on as t' e Cretaceous
f?\
aartzite and dips 65 degrees to the south, a dip -Ye-doh i
maintained
as far west as the for nation is exoosed.
Contention Fault
The north:Test striking fault through the Contention nine is naried
,......__...
.;--,',,,,...
,,,,,,
cy,_,--,71_, .4...0,4,-4.-,1
,
1
the- Contention fault.
It ''
a normal fault,dipaAg steeDly to the south
,
west and is\\deter,»ined ac of -or
_______i
,ineral age because of the intense
,
eralizatim along its trend.
prospect pit southeast of the Contention
-mine shows Bolsa quartzite on granite on the northeast side o f the fault.
The close ilroximity of the grnìte to the present surface as-shown in the
prospect on the east side of the fault suggests strong1y that the faulting
occurred after consolidati_on of te batholith hood.
,Theter or not the
granite was definttely faulted could not be deternined beca,Ase direct
observation of the fault was not Dv,!-,i:ble.
The scabosa limestone has
been faulted to its present contact with portions of the Bolsa quartzite
in some olaces and Abrigo eorratien in other places.
The fault has been cut by the Gartion fault about 400 feet north
northwest of the Contention nine,
The nort--weet strikiru g fracture just
norti of the Garnet Queen is possibly an extension of the Contention fault.
This extension
s again offset to the southwest by another northeast
fault eest of the Garnet ileen nine.
The bloc!: containing the Garnet
,2ueen s'eaft slims a s all exposure of :'tin limestone rest-np: against
the Bolsa.
The dip of the Bolsa and Abrigo which stri' e along the fault is 57
deeres to the southwest.
North of the Garnet Queen the Bolsa strikes
eeetnortlerest and dies to tile south about h0 degrees.
The scabrosa
rest of the Contention mine strikes N 50° ,1 and dips 70 degrees to the
soeth,. Just south of the Gartion this strike swings to S 50°
increase dip of 10 to 15 degrees.
an
:
Nce egest of the Gartion fault the
:artin and Escabrosa strike N 700 - 7 and dip 60 degrees to the south.
Marbra Fault
The nare Marbrosa was obtained by corbining parts of the names of the
two formations, the Martin and the 7:scabrosa which it separates.
This
//fault parallels the Contention fault,just described, and may be cut by the
Gartion as shown by the extension in tl-e stream bed soethwest of the
Garnet lueen.
The presence of the :!arbrosa is infer'ed from the relatien
of the Martin limestone on its southwestern side. Te Ma-in here is
dipping to the southwest at ari average of 70 degrees and strikes roue
parallel to the 'scabrosa.
The Vartin is ter Lnated on the seutheest by a nort-iwest trending
fault and '1as bean brought aeainst the 7aco formation.
This fault appar
ently dies to the soutlywest, conseluent17 it eould be of Vie noe al type
3600'
3700'
3800'
sw
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EXPL ANAT ION
1
O
SECT /ON 5-8"
1
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r1
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SirrPson Syncline
IrII ,
Qd
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Quotenory Cretoceols Perrrr/vcrnión
/1
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PLATE 6
3600-
3700'
3800"
NE
on t'lo basis of stratigraphie novement.
It strikes aproxirateIy paral
lei to the :arbrosa fault and has been traced to the stream bed or the
south where
it is cut by the Nabigo fault.
A small exposure of ascabrosa
ILnestone at the southeast end of the fault is apparently conformable
with the :lartin.
The Naco formation on the southern sde of the fault
strikes N DO° : and dips to t'-,e south at 45 to 50 degrees.
;et of
te Gladstone shaft a northeast fault is cut y the Nabigo
fault to the north.
contact.
This fault meets the Morgan fault at the granite
it is evidently steer and probably normal.
The strong garneti-
zat-!on and epidotization associated with the fault indicate
a
pre-rineral
age, althrith it nay be pr,3.intrusion.
-ast of the Gladstone elaft is a
short,
fault dipoing 72 de-;rees to the southeast.
nore northerly trending
It is cut by an east-west
fracture to the north and by a northeast fault to the
o.W1.
ew hundred fo-A north of the Gladstone shaft there is a fault
striking .11 750
with a steep southerly dip.
It is pre-mineral as evi-
denced by the generous garnet alteration along its arterap .
Gartion
Fault
The name Gartion 5s a combination of the names Garnet lueen and
Contention, the --nes on either siae of the fa-lt.
Gartiem fault
strikes northeasterly but swings more easterly on entering the granite,
and dips about 75 degrees to
the
southeast.
it offsets the garnetized
a
quartz vein in the p:ranite
zone of the Contention fault but contains
at the northeastern end.
by
e:raninatinn
On the basis of this relation and data found
of Dolished secti-ns, It is s.g!7,ested that nineralization
was in two starzes the first a strong contact r.s.acenent stage, and the
second a feeble hypothermal star;e.
A similar trending fault northwest of Vle Garnet Queen also dips
3S
sollthwestward at 75 de7reas.
It too cuts the garnet but, unlike the
Gartion fault, shows no second stage nthera1iaion.
grante and a quartz diorite dike.
it cults the
The TIAvement of the northwest block
has been upward and to the southwest.
This fault is cut by a northwest
fault with a steep sounwest dip located in the strean bed.
The fault
ln -tie stream bed may be an extension of the liarbrosa fault but definite
evidence is Jae.
The northeast str___g failt east of t'-c, Gladstone shaft w'lich cuts
the Eorgan fault to the south, presunenly dins to the southeast at a
rather steer) 8Zi1e,
The
light distaace-ent of the southeast block was
toward the soutl.t-lest.
Two short faults occur at the eastern end of the 3olsa outcrop north
of
here the .;artion and Habig° faults intemuct.
block has been Noved up.
In both the northwest
The fractures are probab-_y vertical although
ttere is little evidence to deter71'me the attitude on either.
The longer
of the two :light he a pat of the northeast fracture west of the Garnet
.deon but novryient within the granite was not evident.
7::abigo Fault
The Nabigo fault is the youngest fault and cuts t:fle area in a gen-
eral eastkIest direction.
to the south.
It dips at a steep angle0;perhaps 7
-
r...rePs
As a result of the Nabigo fault the southern poi __)n of the
area has been lmered so that the Naco formation rests against the Abrigo
fornation for a considerable distance.
-Jestffard along the strike the
Naco, does not appear to havr been intruded by the gran ita in the few ex-
posed outcrops but rather to have been,faulted against the granite.
Folding
The folding of the area consists of one possr:le Tila.lor fold of Which
only
the flanl:s ret3ain as represented by the sedimentaries of the area,
C
3Sao'
3600'
370o"
-
SW
'
1.9
Alluvium
Qni
QUATERNARY
/1 \
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Quartzi+e
K9J
Naco
Cn
I
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Dm
500
Escabrosa
DEVONIAN
{a
Q41
Bolso.
LI
1000
ffEr
T9
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JJ
Garnr{
5
i
"*".
T9
.
C '
3Soo
3600'
3700'
PLATE 7
1
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TERTIARY
i
£b
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Granite
i
(
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I
CAMBRIAN
Abricio
EXPLANATION
0
i
SECTION C-C'
'
L.-._-A_L
//-
CRETACEOVS PhNNSYLVANIAN MISSISSIPPIAN
I
ì :
~
`"U rl
l
T ill / -\. v_1
\/
- / K9}
Q0.1
NE
3-
and two s-ialler folds -- an anticline and the 3ipson syncline.
The
)ossible existence of the major fold will be discussed under "Interpretation°.
The small anticline and 3inpsnn syncline are present in the Abrigo
formation just west of the Gartion fault.
The axis of the (Ampson syn-
cline Plunges in a generally southeast direction .unta it is cut by the
granite contact.
The anticline parallels the Simpson structure and
plunges in the same di-ection.
the northeast.
T3ot.,1 are slight-4 asymmtrical toward
The southern lint of the 3ir3pson s7nc2.ine dips 60 to 65
degrees to the north whereas the nocth li-b dips 50 to 55 decrees to the
south.
This folding probab
occurred during pre-intrusion tine as a
result of conpression exerted upon the areal and maybe genetically related to the thrusting which very possibly occurred in the region.
Interpretation
The 3tructura1 deformation of tie Contention mine area is probably
the result of regional forces acting du revolution.
the post-Cretaceous Laranide
The doninant event of the revolution that may have .lad an
influence upon the development of the area was thrusting 'rich is recognized to the north in the Tucson ijountains" and in the Mineral 7111
At./ P. 754-7551 _939.
ar
4
-e coression -vas strongest al T
a nortlieast-socA to
Cit., 1. 65-66, 720 191t2.
sastmest direction as shown by the deformation in other nearby areas and
the dding in the Twin Buttes area.
The folding of the Abrigo formation west of the Ga_ i(-11, fault suggs
conpression along a northeast-southwest line.
However, it should be
nointed oet that a sliFht directional change in the sedinentary block,
or in the folded portion of the sedimentary hloe, could have occurred
after foldIng, conceivably from the force of the granite intrusion.
elis directional change in the bloc l
If
was nade, then the apnarent north-
east-southwest direction of compression would be in error to the extent
of the amount of directional cange. The amount of change, however, was
evidently only slight for the direction of compression conforms well
with the overall flexing that occurred in the area.
The southern and northern sedimentary blocks in which the Contention
mine and the Minnie nine are located resPectively, illustrate this more
clearly
The strike of the sedimentary rocks of both blocks is remark-
ably consistent, varying bet7een N 40° 71 and N 50 i.
The dip of the
roc's is invariably steep and to the soet!Ivest, except in
he eastern
half of the north block where they dip steeply northeastward.
The strat-
igraphie sequence of the south block is generell- reversed to that of the
north block.
In the southern 'lock the sequence from toe to bottom is
as follows: the Cretaceo,
) quartzite, the Naco formation, the :s
brosa limestone, the :artin liestone, the Abrigo formation, and the
Dolsa quartzite.
This is the normal sequence but in the northern block
it is reversed.
This relationship of the strata toeet_erwIth the conformable strike
suggests that the two sedimentary blocks are actually the li-bs of an
anticline.
The northern block may be considered as a steeply dining and
partly overturned lirb of the anticline, and the sou'hern bloc* as a
seuthvestwardly dieeing limb of the anticline.
The dips of the strata,
as discussed before, indicate tt th western half of the anticline was
quite closely folded.
The eastern half, on the other hand, is an open
type fold.
To allow the more extensive fcldine in elm western half of
tiro halves of the
the anticline there nuat leave been a cleavae,e of the
folds.
northern block by faulting normal to the strike of the
The
block
nortIleast-soutivrest faults in Vle central eart of the nortlIern
may represent this cleavage.
An unliftjng cf Vie area probably
preceded the folding.
acconpanied, and ,eay have eartly
The first stage of faultin,5 the pre.intresien
ste4te, probably occurred at this tine.
Overthrusting, although not definitely recognized in the area,
probably occurred alow: the major northeast-southwest dieection of compression.
As pointed out in the discussion of folding, this direction
the sedimentary block or
nay be in error slightly owing to movement of
blocks involved.
underwent
Following this period of uplift and compression, the area
thrusting
intrusion -.Mich may have been infleenced to some extent by the
in the region.
Locally, the pre-intrusion reverse and normal faults had
the stock .
tee greatest effect in the emplaceT3ent of various parts of
i=ost of the faults of the area were foreed prior to mineralization
and after the consolidation of the hood of the stock,
ividence of this
Gartion fault 7rhich extends
age relationship is found in the mineralized
into the granite.
The highly meneralized Contention fault broiecit
places.
;ranite in contact with the ]scabrosa Belestone in several
The
7ranite in the
localization of the quartz diorite nidikesu fund in the
of the
central part of the area nay have been influenced by fracturing
stock hood.
Alt'iough the pre-mineral faults may not have occurred
time.
simIltaneeusly they probably occurred within a relatively short
anealizetien and alteration-Tere Veen effected by the solutions
from the cooling magna.
.hen the stock became cooled to a sufficient
}t2
ter!iperature nere occurred a settling and adjustment of the area.
clused the final stage of normal faulting.
This
The Nabigo is the only fault
that can be definitely assigned to this age, although several of the
ninor faults are possibly post-nineral.
aumnary
In smm-bary it may be said that during te Laramide revolution the
area was cn-ores:;ed causing folds, reverse faults, and probable clver-
thrsting.
faulting.
intrusion then occurred, folloaed im ediately by pre-T4neral
Contact metamorphism began shortly after intrusir n.
"inor
arounts of other igneous rocks invaded both the hood of the stock and
t le sedlrentary rocks.
Co(ling and shrinkage of t'le stock caused a
settlin.1 and readjustnent of the crist.
-,:neral st ge of faulting.
This produced the final, 'post-
CHAPTR IV
T
7.,C.
Ore Depmits
ieneral
The ore deposits in the Contention area are of the contact reta.
norphic type.
The mineralogical asswiblage, especially that of the
gangue minerals, and the metamorphism of the sedinentary rocks of the
area lead to t'as conclusi-n.
Brown45 pointed out t!lat te de,Doits
i926
.. L., op. cit. (Twin Buttes
.'1,3rt.ywn
at the Contention mine and in the u??er portion of the Senator I:organ
reseribled
He also mentioned that if th'
tenperature vein deoosits.
is true then they were superimposed upon the earlier contact deposits.
The ore minerals, pyri te, chalconyrite, pyrrhetite, snhalerite,
are close v as- ciated with the
magnetite, specul,Lrite, and some
contact
aldrAite,
ngue rinerals, g
wollastonite, cUorit9, and enidote.
actinolite, hedenb,-rgite
The ore is in favorable bd in
limestone near te contact with the granite.
The ore inraI
ave *-
placed the limestone, having been localized by faults and fractures.
The 9:angue rainerais e:ere probbIy del'orited dring the initial
sletanorphjs, rich caused the rec-fsti'alizati-n of the
s one.
The adlitive netamorphism is vv-l'esented by bot
erals and by the Emlfides.
cabosa li-e7a.gue nin-
The stlVdes :lay have been contcripc,-anefmrs
with or later than the silicates.
e Aneralization
alelole, and
CoTeeer is the most abundant metal in the deposits as
occurs predominantly as chalcopyrite.
Zinc occurring as sphalerite is
eredominant at the Contention mine although some copper with silver is
The seall quantities of chalcocite and native copper are
present.
apparent:17 secondary.
after in)The ore-bearing solutions were probably given off shortly
of the
trusion of the magma and continued until after the consolidation
hood as evidenced by the mineralized fractuees in
granite itself.
Contention nine contains a
)ne auc'e fracture to the southeast of the
rent of mineralization in the fo-n of oxidized copoer ninerals.
solutions may have been either eAseous or liquid or both.
The
In the Conten.
silica, copper,
tion area they evidently contained iron, nagnesiun, selfur
zinc, lead, soe silver and a s all a ount of Tianganeee.
tease elements caneot be stated for certain.
The source of
The base metals, copper,
the nagna
lead, zinc' silver, ranganesel and sulfur, probably cane from
The iron, nagnesfean, and silica probably also care frel the nagea
itself.
sedirentary
but may have been derived in part from the alteeation of the
rocks.
From all indications, it aneears that te sedirientaries in the area
great ouantity
are relatively s'Aallow, an the periphery at least, so not a
of eaterial would be supplied by thee
Several uockets in the garnet contain 00e aseociated with a relatively
sal
amount of silic-to ganguee
here the grnnl_te has been exposed
in
the mine eorlrings, the ore is on the limest ne side at a distance from the
contact.
Garnet was the first gangue mineeal deposited and quartz the
last, according to 3rown.46
-
h6
-
Brown,
L., op. ciee
1<:26.
3upergeneLlineralization
Most of the ore produced at te Contention mine and in the Twin
3uttes district as a whole has been from unenriched de?osits.
The
cause of the lack of secondary enric:Iment in the deposits is probably
due to the impermeable character of the rocs as a result of the nassive
silicates and tne easily and quickly mended fractt'res in the lirsestone.
Men, too, it is possible that a sufficient afount of ore has not been
exposed in the geologic past to supply the necessary materials for extensive enrichrent.
The only larle secondarily enriched deposit W 4Ch
was faand close to the surface occurred at the :,enator 1:org-In nine.
Uneralogy
-)re
llnerals
Native Copper (Cu)
secondary.
Foy,
ril
The native copper found in the area is evidently
A considerable anount- was taken from the upper part
personal co-Franication.
of the chalcocite zone in the Copper queen nine.
ite (FeS7)
2yrite is very widely distributed, having been found in
all the mines.
It was the first of the sulfides to be deposited
and occurs as euhed-1 crystals cut by, or altered in part to,
chal-
1
copyrite.
to
Br
At the Sonator Dorgan 8 pyrite is cloely as!3ociated
OD, cit., p. 32, 192:).
with the contact silicates.
yrrhotïte (Fe1.4SWith x betgeen 0 and 0.2)
minor amounts, pyrrhotite is
co only
deposited earlier than ellalcopyri e
-Althgh
occurring
associated with pyrite
in
and was
has
c lief ore 'Iineral of coo er in te a:.ea
Cilalconyrite (CuFeS2)
been chalcopyrite.
the
It is later' than pyrite and 3yrrotite,
associated. A study of
minerals with which it is air() t invariably
mine showed some chalpolished sections of ore fror the Contentirn
than sohalerite.
copyrite altered to e,alcocite and earlier
Sphalerite (7,nS)
district
Sphaleri-he is not abundant in the Twin Buttes
c'-lief metal produced.
except at the Contention -dlere zinc is the
from the u-)ner portions of the Senator
Galena (PbS) - Galena was re)ortod
Morgan deposit.
Some w s found at the Contention minn.
contained chalcocite in
Chalcocite (Cu2S) - Apparently the Vim-lie ore
in the polished sections
the urner 50 feet. Some has ben_ noted
chalcopyrite.
from the Contention where it replaces
:a etite
(FeFe2011)
1:agnetLte is very abundant at the Senator :.,organ
nine.
product cf ')agnetite, occurs
Heratite (Fe203) - Hematite, as an alteration
in quantity at the Senator ;organ.
dendritic de-Posits
:Irolusite (ln02) - The presence of pyrolusite ('n as
on fracture surfaces is conr-on.
ralacnite (011003. Cu(OH)3)
,alach_te is the mo t con carbonate of
surface deposits.
copper and occurred in nearly all the ne:Ir
sparingly throughout the ar,ta.
Azurite (2CuCO3.Cu (OH)3) - Azurite occurred
It is com2only associate with nalachite.
Chrysocolla
1;u3iO3.2H20)
Chrysocolla is midely distributed but not
abundant in near surface deposits.
Allophone (Al2Si05.n1120)
Allo2hane is present in small quantities as a
chrysocolla.
vitreous, pale blue, and brittle surface coating on
Gangue :j.inerals
Andradite (Ca3Fe7(3iO4)3
in the area.
Andradite is very comlon and quite abunaont
It is widely distributed, being localized in favorable
lirestone beds by faults and fractures.
It is practically always
associated with the other contact silicates, especially eAdcte.
At the Contention it is practically the only silicate nrsont accordSo
ing to Foy, and occurs mostly betgeen Cie ore and the granite.
extensive are the exposures of the garnetized lirlestrme that the
larger ones have been plotted on the map.
ketinolite ua9g1F ) 5S13°22 ( °H) 2) Morgan with chlori',e, magnetite,
Actinolite is found at the Senator
-yrite, chalcopyrite, and some
sphalerite.
-Iedenbe-gite (CaFeSi206) -An e2,zaminatirm of the Senator :Torgan dump
showed hedenbergite closely associated ,Itth actinolite and chlorite.
pidote (Ca9(A1,Fe)3(SiO4)3(OH) ) - --pidote is ve-y widely distributed
throughout the area, being nost abundantly associated wit:
ie garnet.
It is common in the Cretaceous (7) quartzite and in some places
naes up about 50 per cent of the cementing material.
'uartz
nine:..al.
- At the Contention mine -,uartz is the most common gr gue
Two generations are observed in the polished sections.
aeplacenent quartz occurs in much of the sedi- entary rock in varying
amounts.
ollastonite (Ca3103)
,cliastonite is emrlon at t:e _3enator :organ mine
There it is associated with actinolite, hedenbergite, and chlorite.
chlorite ((4,Fe)5(A.1,Fe)2Si3010(OH)3) - The dump at the 3enator
organ
shows chlorite closely associated with actinolite, hedenbergite,
pyrite, magnetite, chalcopyrite, and some sphalerite.
Qalcjte
(CaCO3) - Calcite occrs in Elan amounts as a secondary mineral
in the gantTle at the Contention mine.
It is, of courses
he main
constituent of linestrme.
_vagonite (CaCO3) - Aragonite is commonly found in the 1tetono fissures
and is secondary.
eG03) -11 s7all nass of siderite was f-und on the surface in
aderite
the vicinity of thr, Contention mine.
ageneSis
Brown- states that the order of deposition of the ore minerals was
4(..)
4" Brogn,
L., op. cit.,
.
2 $ 1926.
7yrite, pyrrhotte and magnetite, r'ialco-lyrite and sialerite, and
narcasite.
the
The writer's examinations of polished sections
ore from the Contention mine showed that pyrite was deposited firsts
followed by quartz, splIalerites chalcopyrite, chalcocites and a little
second generation quartz, and calcite.
No definite seiluence was determined for the gangue min r ls although
garnet was evidently first with chlorite and quartz last.
This late
stage quartz can probably be correlated with the late quartz in the Garti-n fault and in other fissures of the granite.
It may nossibly re-
resent a second, feeble but yet separate, stage of =ineralizat'cm.
ining
Historical Summary
The history of mining in the Twin Buttes district began in 3.650
50 Brown, H. L., Geology and ore deposits of the Twin Butt-s dLstrict$
Master's thesis, University of Arizona, pp. 4-7, 1926.
March /946
NNW
SECT /ON
SCALE 1" = So FEET
CONTENT /ON MINE
H
H
Piote 8
Fror., Srction by
R.MHernoi
E_Q.$fo/-7
SSE
It°
G. Bush, later
with the clairs located by a TZ.r. Baxter who, with
formed the Bush-Daxter :lining Company
aone work was carried on in
portions of the Senator Morgan and Corer -).tieen ore bodies but the ex..
tensive develo-Inent did not begin until 1903 when the rTin Butte
ing and Smiting Company took control of the area.
in-
Operations from
tat time un through 1926 were intermittent but reasona ly productive.
The ocmanies concerned 7-Tere the Twin Buttes Lthiing Company; tie Busli
3axter ining Comp& ny; the Glance 14ining Conpany; the .'Lnerican Soelting
and
ofining Conpany; and the Midland Cop-,er Ca-now.
sisted of the Cop-0
The nins con-
Amen, Copper Glance, Bullion, Minnie, Senator
organ, Gladstone, and Contention (for'.r3,y the North Star)
Several
other wospects are present throughout the area.
Contention Mine
.10
r: began
t the Contention Mine in i$1951
1926.
C te
to a depth of 210 feet.
Ser ral crosscuts have been nade from the 150
and 210 levels to the south and we t.
taming the
shaft was sunk
These intersect a garnet zone
re, and the :scabrosa limestone, bcth dipoing soutlwest and
striking ap!roxi7ately N 60° 4.
The ore was mainly of zinc with so me
copryer and silver but none was shipped in the oar
days.
The mime was operated from 11 to 19116, and for a short period in
1-7117. -T.ollJotion 'during this perio&amounted to $23(,000.7
L:2
Foy, 7iiliaE1, p
131-11.11iCa
contained about 11.5 per cent zinc,
ounces of silver --er ton.
Tne ore
per cent coper, and about 1.6
December /943
2/0' LEVEL
SCALE 1 "= /00 FEET
CON TEN T /ON MINE
N
P/ote 9
Fr'nrn tri w/o by
E.A. Stone (.7i7cl RM.Hernon
153' LEVEL
Minnie Mine
d in the north tart of the area, about
The Minnie Mine is 1
11 miles west of t'7,e Cooper
Lieen nine.
The depth reached was 750
Oxidized copper ore was located in
feet with levels every fifty feet.
the upper portion and copper sulfide, mainly chalcopyrite, in the lower
part dean to the auartite an the loae t level.
The thaiy limestone
was apparently more easily replaced than was the purer linestonewirich
has been silicified.
Brown, R.
r2p. cit., ,.
Production was carried on in the ear_
in r2'-, when a small sAuraznt was made.
sane ore available at this nine.
ilhia,
Apparently, tere is still
The total¡production, according to
1
has been about
Fay/
the district and also
r
ers (marl communi cat on.
Gladstone :ane
Te
GIad,,tone shft was sunk in 1224 and 1925 by Edward toy.
Water,
which was later used to sup2v the Twin Buttes ca, was struck at a
depth of 365 feet.
lag to F
'15
total depth cl the shaft is 42C feet, and, acc rd-
was all in garnet.
On the hc ai 70C to :Jrr feet of
dward, personal comnunication.
d
s done mostly in the general direction of the Senator !lorgan,
One drift extends from the shaft to the north for 60 fet.
was f,-.'und in the ,lorkings, and metallic
No granite
J]fides were entirely absent.
r
o
N
soO
1000
loo0
3000
4000
Map of southern Claims of Twin Bu f / es At-ea
Sóao Feet
TN. S TF 1iENS
By
CLA/M MAP
MOD /F /ED FROM
Plez te. /0
1
Garnet Queen Prospect
The Garnet
depth.
lieen prospect consists merely of a shaft 100 fet in
No granite was struck, and like the Gladstone, no metallic sul-
fides gere noted.
Other Prospects
the west on the Morgan fault there is a =. ospect where some
copper carbonate was located.
Several other prospecting shafts are lo-
cated throughout the area but apoarent ,
alizaticn.
were in zones devoid of miner-
The deeper prospects are noted on the geolwic map (Plate 1).
Future of the Area
Ytost of the knoan ore bodies of the area are exusted.
Some low-
grade coper remains at the Minnie mine and zinc and copper ore is still
present at the Contentirn mine.')
56
Tdgard, personal .communic
The possibility of small deposits else-
t
on.
ghere in the area stil3 exists, especiar
fault.
nectinn with the Morgan
The Gladstone shaft, al,bouRh ha) feet deep, may still be too
s- llow to exoose some small ore bodies.
A close investigatim of the area
should be preceded by a detailed preliminary study of past rneratirms.
BIBLIOGRAPHY
Broan, H. L., Geology and ore deflosits of the Tain luttes district,
M. S. thesis, Univ. Arizona, 126.
Brown,
:. H., Tucson mountains, an Arizona basin range type, Geol. Soc.
America Bull., vol. 50, 17r.
Butler, B. S., Ore deposits as related to stratigraphic, structural, and
igneous geology in the western United States, Amer. Inst. Mir. and
Net. Ehg., Lindgren volume, 7.2. 223-2261 1933.
Butler, B. 3,, and Alson, R. D., Some Arizona ore deposits, Arizona Bur.
Mines, Bull. 145, PP. 2-25, 1933.
Darton,
11 resume' of Ariz,Tna geology, Arizona Bur. 7anes, Bull.
119, 1925.
Eckel, E. B., Geology and ore deposits of the 71ineral :Till area, Ana
County, Arizona, M. S. theeis, Univ. Arizona, r30.
asing, 14 J., and Heineman,
lanes, Bull. 140, L3..
Arizona metal production, Arizona Bur.
Gordon, P. a., The geology of the Twin Buttes mining district, 14. S.
t:lesis, Univ. Arizrna,
Higdon, C. P. , The geology and ore deposits of the Sunshine Mine area,
Pina County, Arizona,
S. thesis, Univ. Arizona, 1933.
Hinds, N.
A., 7;p-Archean and ç-Ugonk1an intervals in western North
America, abstract, Geol. Soc. Amer. ?roc. 1,734, pp. 319-320, June
1935.
Jones, J. -I., The geology of the Sycamore Ridge area, Pima County,
Arizona, . 5. thesis, Univ. Arizona., 1111.
Lindgren,
:aldnarp
1:4neral doits, :c(Law....Hill 3o k Co., Inc., p. 712,
133.
aga, M. N., The geology and ore deposits of the Helmet Peak area, Ana
County,- Arizona, Ph.D. thesis, Univ. Arizona, 1942.
C. I., Geolov of the San Xavier d:stri_ct, H. S. thesis, Univ. Ariz.,
1939.
°poll', Constantine, The geology cf the .osErlont mining camp, Pima County,
Arizona, M. S. thesis, Univ. Arizona, 1110.
;Zansome, F. L. , 3eoloc7 and ore deoosits of the Bisbee quadrangle, U. S.
Geol. Survey, Prof. Paper No. 21, 1904.
i?ansome, F. L., Some Paleozoic sections in Arizona and their correlation*
U. S. Geol. Survey, Prof. Paper 98K, pp. 165-166, 1910
,
Ore deposits of the Sierrita Mountains, Arizona, U. S.
u1i. 725, 1:21.
,Jebl. Survey,
-3clirader, F. C., 1,Jineral deposits of the Santa Rita and Patagonia Mbun-
tens, Ariz,:ma, 'T. 3. Geol. Survey, Bull, 532, 1915.
St,Tanowl A. A., Correlation of Arizona Paleozoic fortin, Geol.
Anerica Bull., vol. 47, 1736.
Paleozoic paleogeograp4 of Ariz, Geol. Soc. America
voi. 53, 1'742.
iebber, B. N., ::arcasite tn the contact metamorphic ore deposits of the
Twin Buttes district, Pima C imty, Arizona, Econ. Geol., vol. 24,
3C4-31'
.hitcomb, Harold, The geology of the Senator Morgan mine area, Twin Buttes,
Ariznna,
S. thesis, Univ. Arizona,
ilson, :L. A., Thrilet faaltiwr, in the 7.1npire ":ovntains of southeastern
Arizona, Jour. Geol., vol. 42, pp. 442-h59, 1:711.
11
View looking northeast from a point west of the Gladston e
shaft.
7jills i
Ift background are the Twin Buttes.
Head frame of !Annie mine, lof-king nnrtheast.
town is 4n right baci., _und.
Twin Buttes
2Iate 12
A.
View looking northeast sdng uartion fault from
itcc ) feet west of the Contention mine.
D.
Abrigo P,rmation showing differential weat-lering.
a Ir1 r14-
co
L'Iate L3
A.
B.
Naco 2ormatim.
:lass of garnetized _scabrosa limestone near Contention
nine.
?late 14
A.
Abrigo formation, view on bedding plane surface.
B.
Contact of luartz di-rite and granite in arroyo 150( feet
nort7gest of Contention -line.
or]
Plate 15
,A
A.
ilhotordcrograph of biotite granite shming orthoclase (o)
_agiociase (p), quartz (A), and alteration products.
Crossed nicols. X 55.
B.
hyolite porphyry with phenocryst of highly altered
ort'lociase (0).
Crossed nicols.
X
S!
a-re!d
Plate 16
PhotoTalcrograOh of biotite granite dike sh Ang fine
grained quartz (q) , plagioclase (p), an
alterati,-n.
0.
Crossed nicols.
sericitic
X 55.
BiAite granite shryling zoned euhedral crystal of
plagioclase (p) in quartz (I), orthoclase (o) , and
plagioclase.
Crosed nicols.
X )5.
P1 a+e 16
ß
1-late 17
A.
Polished section of are from Contention mine showing
quartz (1), gangue, chalcopyrite (co) as blebs in sphalerite (sp) and being replaced by chalcocite (cc) . X 70.
B.
Polished soctirn of chalcopyrite (ep) blebs in spialente (sp) .
X 7 .
Plafe 17
A
;late 1
Polished section of ore shoving chalcocite (cc)
replacing chalcopyrite (cp) and surr7u1Lde1 by
quartz (1).
B.
X 70.
Photomicrograph showing sDhalerite (sp) , cha1cc9yrite
(cp), and carbonate gangue (cg) .
X 70.
Plahe
18
N
EXPLANATION
SEDIMENTARY
QUATERNARY
ool
IGNEOUS
Mo
Tg
alluvium
granite
ee
Road
quartzite
CRETACEOUS (')
Ka+(?)
limestone
shale
PERMIAN
Pe*
limestone
Tad
quartz diorite
Monzono Beds, marl,
greinte dike
shale
Dol
Naco
PENNSYLVANIAN
Cn
MISSISSIPPIAN
Ce
Esaobrosa
DEVONIAN
On
Martin
I
rhyoli +e rsn hyry
tone
9Orne+ zone
limestone
limes tone
Abrigo
Upper
FAULTS
hroest one
CAMBRIAN
observed
Balsa
Middle
quartzite
Jo
inferred
3600
T9
T9a
Ted
tqa,
Sol
T3
3666
O
Tg
T9
Maya.
Sal
GEOL. OCIO
/VA P
THE SOL,'THERN f i`i R T
I
Dal
OF
T
THE T w//V BUTTES A REA
PIMA M/N/NG D/STR/CT, ARIZO/l/A
Sol
Oc)
kale
3ÓO0
Feet
xso
Fop
Sol
Coitour
Coitour interval 25 feet
!Dalum is mean sea level
"iopo9raphy & Geolo9y by
F. N. Houser
H.A.Whitcvmb
Sal
GEOLOGY
1948
HOU5ER
CO TENT /ON
NE Z,
wrriTCOgne
ARIZONA
(PIMA COUNTY)
UNITED STATES
DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
1 1 1°15'
1710 000 FEET
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89
111
Topography by J. L. Lewis, F. H. Purdy,
J. J. Hayes, S. M. Borrell,K. A. Bunker,
P. J. Frampton, and G. B. Woolley
Surveyed in 1938-1939
...
..
BM
27
3526
.-
25
3377
3
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6
3282
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A
148
71.o
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1/4,'.
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28
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E.
5'
1
3
25
Scale
AMADO 27/2M1.
NOGALES 91 MI.
6215-00
o
4 Mike
3
'2
ROUTES USUALLY TRAVELED
ix
o
1000
-
500
1000
1
APPROXIMATE MEAN
DEOLINATION,1939
0
1000
2000
3000
4000
5000
0
3000
6000
9000
12000
,15000
I-I #4
.6
1
I--i
0
1
2
3
4
7000 Yards
6000
18000 Feet
Datum is mean sea level
780000 FEET
31°45'
111 00'
1927 North American datum
5000 yard grid based on U. S. zone system, F
10000 foot grid based on Arizona (Central)
rectangular coordinate System
Polyconic projection.
\?"
TWIN BUTTES, ARIZ.
1940
5 Kilometers
27
A
R. 13 E.I
HARD IMPERVIOUS SURFACES
OTHER SURFACE IMPROVEMENTS
C3U. S. ROUTE
Contour interval 50 feet
g
Preliminary edi ion 1942
10'
7
....-
STATE ROUTE
N3145-W11100/15
Plate 2