'
GEOLOGY OFTHE
TENTH
POTASH
ORE
ZONE:
PERMIAN SALAD0 FORMATION,
CARLSBAD DISTRICT, NEW MEXICO
ROBERT C.M. GUNN
AND
JOHN M. HILLS
OPEN FILE FEZOF2 146
I wish to thank the personnel of Noranda Mines Limited who allowed Gunn-to
. Hinds,
study and work on their potash exploration program, especially 0Mr.
J.
,.
Dr. J. J. M. Miller, Mr. J. Condon Mr.
and J. F. Brewer., Informationfor this
report could not have been obtained without their help and the friendly relat
ships with the following potash companies and individuals:
Duval Corporation
Mr. W. Blake
Mr. M. P. Scroggin
International Minerals and Chemical Corporation
Mr. R. Koenig
Kerr-McGee Chemical Corporation
Mr. R. Lane
National Potash Company
Mr. P. Brewer
United States Geological Survey
Mr. C. L. Jones
Independent Chemist who assayed Noranda potash core in Carlsbad
Mr. T. J. Futch
Independent Potash Consultant in Carlsbad
Mr. E. H. Miller
Dr. W. N. McAnulty, Dr. W. R. Roser and co-author Hills supervised Gun&
of Texas at El Paso upon which this paper
original Masters thesis at University
is based.
Dr. W. M. Schwerdtner of the University of Toronto has read the manuscript
critically.
Noranda Exploration Company has kindly permitted the publication
of insormation gathered from their properties.
ABSTRACT
zone is a bedded evaporite deposit in the
The Tenth potash ore
(Ochoan) SaladoFormation
New Mexico.The
Permian
i n t h e Carlsbad d i s t r i c t , Eddy and Lex counties,
rocks of the Tenth ore
zone were precipitated in the super-
s a l i n e p a r t of t h e Permian basin and range from 6 t o 10 f e e t (1.8 t o 2.1 meters)
a 1975 study of the Tenth ore
in thickness. This report gives the results of
zone
i n t h e Duval Corporation's Nash Draw mine; t h e Kerr-McGee Chemical Corporation's
potash miner; the National Potash
Company'sLea
mine; and t h e Noranda Exploration
Inc. d r i l l c o r e s .
The Tenth ore zone lithofacies include halite rock, sylvinite
litite.
and carnal-
Brines from t h e s a l i n e environment intrudedthesupersalineenvironment,
dissolved primary carnallite
and released potassium and chloride ions which r e -
precipitatedassylvitebeforeburial.
h a l i t e f a c i e s is markedby
clay in the
The boundarybetween
erosional salt horses,
t h e s y l v i t e and
and a change from g r e e n t o brown
gangue.
After burial, autogenetic events
b a s a l t removed some potentialore.
due t o p r e s s u r e and an intrusion of Tertiary
A f a u l tc r e a t e d
tercrystalline cavities, crystallized as pegmatitic
horses.Hematite,characteristically
lost during recrystallization.
metasomaticallyreplaced
a salthorse.Brines,ininpods o f s y l v i n i t e or a s s a l t
found as rims around s y l v i t e c r y s t a l s ,
was
The rims were corroded i n p l a c e s where s y l v i t e was
by c a r n a l l i t e .
When s y l v i t e was replaced by langbeinite,
l e o n i t e or k i e s e r i t e , remnant hematite rims a r e p r e s e n t .
.
1
INTRODUCTION AND PURPOSE OF THIS STUDY
Potash is the potassium oxide equivalent
parisonofpotassium
which serves a standard for com-
compounds i n t h e world f e r t i z l i e r market.
The carlsbad dis-
t r i c t (Fig. 1) contains the largest soluble potash resource in the
United S t a t e s
(Jones,1975).
Bailey(Smith,
1 9 3 8 ) - i d e n t i f i e d s y l v i t e (KCI) from t h e Snowden-McSweeney
No, 1 McNutt o i l t e s t i n Section 4, Range30E,
Township 21s.
Potash Company produced t h e first refined potash product in
now mined by Mississippi Potash Incorporated
The purpose of
The Unites States
1931 from property
(Fig. 2 ) .
t h i s investigation was t o determine the relationship
s y l v i n i t e and t h e gangue rock i n t h e Tenth potash ore
i s t h e name given t o a group of three evaporite beds
zone.
between
The Tenth ore zone
below 610 f e e t (190 meters)
thetopoftheSalado
Formation (Upper Permian) ( F i g . 3 ) .
zone does not qualify
as ore a t the present time, but the
A l l thepotash
in this
non-ore portion may con-
stitute an important future potash resource.
Gunn gathered the field data
1975.
for ' t h i s r e p o r t i n t h e s p r i n g
He was employed by Noranda Exploration Inc., andlogged
from below t h e 120 Marker Bed, through t h e youngerTenth
119 Marker Bed.Gunn
mined:
35 d r i l l c o r e s
a r e zone t o above t h e
a l s o observed t h e Tenth o r e zoneunderground
Duval Corporation, NashDraw
NationalPotash,
and summer of
Lea mine.
where it is
Mine; t h e Kerr-McGee potash mine;and
An x-raydefractometer
was used t o i d e n t i f y t h e
the
L
Location of Area Investigated
The Carlsbad district is located in Lea and Eddy Counties in southeastern
(24 kilometers) eastof the Cityof Carlsbad.
New Mexico (Fig. 1) about 15 miles
of drilling
location
Figure 2 shows the limits of mining in the district and the
done by Noranda Exploration, Inc.
Seven companies are presently mining in the district. The names of the
mines and their shaft locations are as follows:
1.
Amar Chemical Corporation, Section
9, Township
19S, Range30E.
2.
Duval Corporation
22, Township 18S,
Willis Weaver mine, in Section
Range 30E; Saunders mine, in Section 35, Township
ZOS, Range 30E; and Nash Draw mine, in Section 33,
Township 22S, Range 30E.
3.
International Minerals and Chemical Corporation,
22.5, Range 29E.
in Sections 1, 11, 12, 23, Township
4.
4, Township
Kerr-McGee Chemical Corporation, in Section
21S, Range 31E.
5. National
Potash
Company
ZOS, Range 32E; and
Lea mine, in Section 18, Township
25, Township ZOS, Range 29E.
Eddy mine, in Section
6.
Potash Companyof America, Division Ideal Basic
4, 17, Township205,
Industries Incorporated, in Sections
Range 30E.
i
3
3 4
..(
0
t n
i
0
..
.
. .
. .. .
.
. .
..
, .
F I g w L Limits o f mining I n t h CIrlsbad d l r t r l c t * and location o f
Norantla Explwatlon. Inc. drllllng.
I
.
XALE
6
12 Mter
6
7. Mississippi Potash, Incorporated, in Sections 12,
13, TownshipZlS, Range 29E, and in Section 13,
30.
Township ZOS, Range
GEOLOGICAL SETTING
ore zone
The Tenth potash
deposit
forms
part
of
the
Permian
upper
Salado
Formation in the Delaware basin of west Texas and southeast New Mexico. This
basin is surrounded by the Upper Permian Capitan reef and is separated from t
Midland basin by an uplift known as the Central Basin platform (Cartwright,
1930, p. 970) (Galley 1958).
The area discussed in this study is on the extreme
northeast edgeof the Delaware basin (Fig. 1) and overlies,in part, the Capitan
reef.
The Tenth ore zone (Fig. 4) is a tripartite clusterof strata containing
by halite beds. The whole
potassium minerals. It is underlain and overlain
assemblage is underlain by the 120 Marker Bed ofcomposed
distinctive
anhydrite,
polyhalite and kieserite. Overlying the upper halite bed is the 119 Marker Bed
containing anhydrite, polyhalite and basal claystone. The vertical interval
(4.9feet
meters).
between the two marker beds is about 16
Herefront.
The Noranda Exploration property lies north of the Capitan reef
the Tenthore zone and the
120 Marker Bed beneath it dip to the east-southeast.
The 120 Marker Bed dips
2 to 3 degrees per mile to the east-southeast on the
west side of the property1 to
and2 degrees per mile to the east-southeast on
the east (Fig.2).
However the dip of the Tenth
ore zone is to the south between
the National Potash, Lea mine located over the Capitan reef and the Kerr-McG
evaporite beds
,
. .
COLLRlNAR SEDION
ROCKY TYPE
ROCK NAME
119 MI\N<ER BED
HALITE
..
8
potash mine on the northeast edge of the delaware basin
2 ) . (Fig.
The change
in dip direction may be the result of diagenetic evaporite compaction in the
Delaware
basin.
Salado Formation
3) was named by Lang (1935) from the subsurface
The Salado Formation (Fig.
It
section in the Means Number
1 well on the Pinal dome, Loving County, Texas.
donformably overlies the Castile Formation in the Delaware basin, and is unconformably overalin by the Rustler Formation.
The extent of the Salado Formation and its relationship to the structural
provinces in the Permian basin are shown in Fig. 1. The northern and eastern
to the
margins of the Salado Formation contain clastic material and may
be close
of the Salado Formation is trunoriginal depositional limit. The southern edge
cated by Cretaceous. , beds
along the front of the Marathon-Ouachita geosynclinal
.....
thrust belt. The western boundary
of the Salado Formation is truncated by late
Permian erosion followed by solutioning during Cenozoic time due to the underflow
of the Pecos River. Thus, the western limit
of deposirion of the Salado is unknown.
In the Salado Formation, the sedimentation cycle is as follows:
top
l
argillaceous halite stratum
halite stratum
sulfate marker bed
claystone stratum
siltstone
and
sandstone
bottom
This cycle is not always complete. Individual strata are persistent laterally
foot to 30 feet
for miles. All beds but the claystone stratum range 1 from
thin film to5
(0.3 to 9 meters) in thickness. The claystone units vary afrom
inches (13 centimeters) in thickness. Clastic rocks form
a very small part of
the Salado Formation.
9
OBSERVATIONS
The rock types associated with the Tenth ore
h a l i t e and s u l f a t e .
rock types i s
The following detailed description of the
based on observation of
the Tenth ore
zone a r e h a l i t e , a r g i l l a c e o u s
Noranda Exploration, Inc.
zone i n mine workings.
d r i l l c o r e and exposures of
The color designation is i n accordancewith
of America.
the rock color chart of the Geological Society
Halite Rock
Halite aock is associated with the poorly mineralized middle
Tenth o r e zoneand with the barren beds
and 120 Marker Beds (Fig. 4).
clay. Halite rock
between t h e t e n t h o r e
member of t h e
zone and t h e 119
This type of rock commonly contains 0.8% t o 0.5%
i s also associated with salt h o r s e s i n a l l members of t h e
Tenth o r e zone.
The h a l i t e r o c k i n commonly milky white (NSI or c o l o r l e s s , b u t it i s a l s o
reddish-orange (10 R 6 / 6 ) , yellowish-orange (10 YR 6 / 6 ) , 'very light gray
very dusky purple (5P 2/2) and dark blue in color.
derive their color
(NS),
The milky h a l i t e c r y s t a l s
from minute fluid inclusions trapped within the crystals.
The c r y s t a l s a r e e u h e d r a l t o s u b h e d r a l
and r a n g e i n s i z e from 0.2 t o 0.8 inches
(0.5 t o 2.0 centimeters).
The reddish-orange halite occurs in
centimeters)inthicknessimmediately
above t h e 119 Marker Bed.Adams
believes the reddish-orange color in halite
This sulfate deposition pattern
h a l i t e bands.
bands 1.0 t o 2.0 inches (3.0 t o 5.0
(1967. p. 64)
i s due t o minute polyhalite inclusions.
is reflected in the individual reddish-orange
A thin stringer of polyhalite usually
with underlying occluded polyhalite oontained in
makes a sharp basal contact
a h a l i t e band.
10
Argillaceous Halite Rock
The a r g i l l a c e o u s h a l i t e r o c k d i f f e r s from h a l i t e rock only in the presence
of insoluble, mainly clay minerals in
gillaceous halite occurs
Tenth o r e zone.
amounts ranging from 1%t o 100%. The a r - .
as an lithofacies of the upper
When a r g i l l a c e o u s h a l i t e forms t h e m a t r i x f o r s y l v i t e c r y s t a l s ,
is termed s y l v i n i t e .
then the entire rock
The averagepercentage of insolubles
i n t h e upper and lower members of the Tenth ore
tively.
and lower members of t h e
the insolubles from t h i s typeofrock
Analysesof
dicate the presence
zone is 2.6% and 4.7%. respec;
of q u a r t z , i l l i t e , c h l o r i t e
from t h e d i s t r i c t in-
and c o r r e n s i t e c l a y s (Grim and others,
The c l a y i s either pale green
1969), as well as talc (Bailey,1949),
(10 G 6/2)
or moderate brown (5 YR 3 / 4 ) .
Schaller and Henderson (1932 p. 25) assayed t h e i r o n i n b o t h
Both colors of clay contained about
1%ferrous iron but the
colors of clay.
brown clay contained
5.15% ferric i r o n or 11.7 more f e r r i c i r o n t h a n t h e g r e e n c l a y .
I n .%Val Corporation's Nash Draw mine, t h e b a s e of t h e lower member of t h e
Tenth ore zone i s usually moderate brown a r g i l l a c e o u s h a l i t e r o c k r a t h e r t h a n
sylvinite.
The color of t h e c l a y i n s y l v i n i t e
lizationhasoccurred.
drill core, the base
mixture of carnallite
Twelve miles northeastward, i n a Noranda Exploration,Inc.
of t h e lower member of the Tenth ore
and h a l i t e .
c l a y a t the carnallite-clay contact.
i s chemicallyreduced.
i s pale green even where r e c r y s t a l -
zone i s c a r n a l l i t i t e , a
The basal brown c l a y is a l t e r e d t o pale green
The green color i n d i c a t e s t h e i r o n
The bitterns probably leached out the
i n the clay
ferric iron and pre-
c i p i t a t e d it a s h e m a t i t e p l a t e s i n s y l v i t e
and c a r n a l l i t e .
bably also carried the carnallite into the
lower member of the Tenth o r e zone.
These solutions pro-
Where t h e 119 Marker Bed is a t l e a s t 1.5 feet (0.45 meters) thick,
fractured claystone
a
seam averaging 1 inch(2.5centimeters)inthicknessoccurs
beneath it. This claystone
seam t h i n s o u t and disappears before the overlying sul-
faCe p a r t of t h e 119 Marker bed d i s a p p e a r s l a t e r a l l y .
S u l f a t e Rock
The sulfate rock type includes anhydrite
(CaSO4) and polyhalite
(2Ca-S04-MgS04-K2S04-2H20). No evidenceoforiginal
gypsum c r y s t a l l i z a t i o n i s seen i n
t h e 119 and 120 Marker Beds or i n t h e Tenth ore zonebetween these beds. Other
phate minerals are langbeinite, kieserite
pread rock u n i t s i n the study area.
and leonite, but they
and broad geographic range. In
Survey standardized the stratigraphic terminology
i n t h e d i s t r i c t based on 143 s u l f a t e marker beds.(Table
The 119 and 120 Marker Beds a r e commonlycomposed
line, laminar, nodular
or vuggy anhydrite, polyhalite
H a l i t e is often present as nodules or hhinbands
Anhydrite i s li$ht gray
I).
of massive, finely crystal-
or anhydrite and polyhalite.
and c l a y i s p r e s e n t i n t r a c e
(N7) i n c o l o r and posyhalite ranges
(IO R 3/4)"brickred,"tomoderateorangepink
from t h e p o l y h a l i t e p a r t o f t h i s
M.P.
Scrogginof
119 Marker Bed.
(10 YR 8/4 and 5 YR 8/4). In
and3/40%
anhydrite.
one
pale green clay-
The clay separates the anhydrite
Marker Bed.
Duval Corporation made a chemical analysis of three
of t h e 119 Marker Bed collected by Gunn i n t h e Nash Draw mine.
pink (10 YR 8/4)sample
amounts.
from darkreddish-brown
Noranda d r i l l c o r e a t h i n band of anhydrite is sandwichedbetween
stone seams a t t h e b a s e o f t h e
do not form wides-
The 119 and 120'Marker Beds a r e e x c e l l e n t . s t r a t i -
graphic markers because of their easy identification
1952 the United States Geological
sul-
from above mineable Tenth ore
The moderateorangepink
samples
The moderateorange
zone was 89.58% p o l y h a l i t e
(10 R 7/4)
samplefrom
5
%
.N
#
&
National Farmers Union (NationalPotashCorporation)
*For logs submittedafter 12/17/52RevisedU.S.G.S.system
will beused.
0
0E
..
FreeportSulfur Company
(Kermac
PotashCorporation)
*For logs submitted after 12/17/52Revised
U.S.G.S. system will beused.
. u
E: 2 2
0
4
2
O
mrl
4 4
N O O r l N
NNNN
8 ;
g
5
r l m
12
Table I (Continued)
OLD
Revised
12/19/52
8th Ore Zone 9th
Union Anhydrite
7th Ore zone
6th Ore Zone
5th Ore Zone
123
123
124
124
4th Ore Zone
'3rd Ore Zone
-
2nd Ore Zone
125
1st Ore
Zone
126
127
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
Cowden
Anhydrite
LaHuerta
Siltstone
Fletcher
Anhydrite
127
-
129
130
Smith
Schaller
USPC
20
S y l v i t e #1
#1A
-
-
-
#20A
21
22
-
-
Sylvite
Sylvite
Anhy.
Anhy.
Sylvite
Sylvite
#2
#3
#1
#2
#4
#5
-
Sylvite
#6
#3B
SalmonPoly.
Poly.
28
29
30
31
32
Sylvite
#7
Poly. #10
23
24
25
25A
26
27
-
131
132
133 ,33
134 34
135
136
137
138
-
#2
35
36
37
38
-
139 39
140 40
141 41
42
- 43
Cowden
Anhydrite
LaHuerta
Siltstone
Fletcher
Anhydrite
-
-
-
-
-
#2A
-
A
#3
#3A
#4
--
FSC
SWPC
NFU
above the margin aofsalt horse was 81.14% polyhalite and 5.75% anhydrite.
The
moderate reddish orange (10
R 6/6) sample abovea salt horse was 87.84% polyhalite
I
l
and 5.16% anhydrite. The unreported material needed to make each analyses 100% is
-
mainly halite, with minor insoluble clay. These data indicate that polyhalite
anhydrite lithofacies do not vary significantly whether the 119 Marker Bed ove
o r a barren lithofacies.
lies the ore zone
Where the 119 Marker Bed is thick (TablefI), it commonly
a basal
has claystone seam and the sedimenaary structure of the
Bed Marker
changes from mosaic to
bedded
to
The
nodular
other
polyhalite
extreme
in
and
anhydrite.
marker
bed
structure
is
seen
where
the
119
Marker
is thin (Table 11), the bedded
stwctures dominate and the contacts above and be68 a gradual increaseo r decrease in sulfate
low are sharp. There is no evidence
accumulation such as would be expected for minerals which accumulate
a brine below
from which they precipitate. There is no evidence
of erosion of the underlying
halite and no basal claystone seam. In oneofcore
the 119 Marker Bed with
a fine-
grained anhydrite matrix, there were 0.05-0.08 inch (1-2 millimeters) rounded sand
size grains of anhydrite. Subrounded polyhalite pebbles are present in the argil
laceous halite lithofacies of the lower member.of the Tenth ore zone, and ar
bably derived from erosion of the older consolidated 120 Marker Bed.
Rocks
of
the
Tenth
Ore
Zone
The Tenth ore zone is being mined for its sylvinite rock in the Duval
ation's Nash Draw mine; the National Potash's Lea mine; and the Kerr-McGee potash
mine. Schwerdtner (1964, p. 1109) defined sylvinite a as
rock composed of a mixture
of sylviPe (KC1)'and halite (NaC1) with minor amounts
of carbonates, sulfates and
clay.
Table I1 Vertical change in deposition of sulfate rock (based
on Noranda Exploration d r i l l c o r e ) .
Thick Deposit
(119 Marker Bed)
Thin Deposit
(119 Marker Bed)
(120 Marker Bed)
Nodular
No deposition
Distorted Nodular
I,
It
Distorted Bedded Nodular
11
11
Bedded Nodular
Bedded Nodular
Streaky Laminated, Bedded Massive
Streaky Laminated, Bedded Massive
Bedded Massive
Bedded Massive
Bedded Mosaic
No deposition
Distorted Nodular Mosaic
11
Nodular Mosaic
11
!I
1,
I n t e r p r e t a t i o n of Structures i n Marker Beds
Environment of p r e c i p i t a t i o n and deposition of anhydrite, polyhalite,
with
an
average
thickness
of 1.5 f e e t
(0.49 meters)
Restricted environment of accumulation of transportedanhydrite,ptdyhalite,
and kieserite, with
an
average
thickness
of
0.4 f e e t (0.1 meters)
Terminology from Maiklem and others, 1969.
16
Jones (1972) grouped sylvinite deposits on the basis of sylvite concentratio
as follows: massive deposits, lens deposits and disseminated deposits. The massive
deposits are stratiform, with gradational lower boundaries and sharp upper bound
ies as seen in the members of the Tenth ore
(Pl. zone
I). The lens deposits are
few centimeters toa meter in
erratic, discordant bodies ranging in size a from
thickness. They consist almost entirely of sylvite and resemble pegmatitic salt
horses. The disseminated sylvite deposits disappear gradually into halite or argil-
laceous halite rock. The sylvite in the halite which envelops the Tenth Ore zo
dissiminated. These deposits may be the result
of precipitation of halite and minor
sylvite from different levels in the Ochoan sea brine. For aexample,
sylvite cry-
stal with an eroded red rim containing hematite, was seen in halite rock belo
Tenth ore zone. The sylvite partially dissolved because it was unstable in the
saline halite facies.
In the National Potash's, Lea mine, and the Noranda drill core carnallitit
in the Tenth ore zone. Schwerdtner (1964, p. 1109) defined
and hartsalz are present
carnallitite
as
a rock consisting of
a mixture of carnallite (KC1-MgC12-6M20)
halite and possible sylvite and minor amounts of carbonates, sulfates and clay.
(hIgSO4(1924, p. 225) define'd hartsalz aas
rock composedof a mixture of Kieserite
H20) in sylvinite rock. The tenth ore was mapped before December
19, 1952 as various
ore zone3 : Eleventh by U.S.G.S.,
Seventeenth by Smith, Carnalite #1 by Schaller,
Number 1 by U.S. Potash Corp. and International Minerals and Chemical Corp., Number
117 by Duval dorp., and "J"
theby Potash Company of America(Tab1e
:
)
1
Mineralogy "
of "
the
Tenth Ore Zone
The minerals with which this study is concerned ard: sylvite, carnallite
and minor amounts of kieserite, langbeinite, leonite and epsomite, listed in ord
of decreasing abundance. These minerals are found in host rocks of hklite or arg
laceous halite.
19
Tenth ore zone, is present as c o a r s e t o peg-
Sylvite, the ore mineral in the
matitic, subhedral t o euhedral crystals. These are usually
clear o r a milkycolor
when filled with fluid inclusions. Sylvite can be distinquished
bitter taste.
from h a l i t e by i t s
Sodium c o b a l t i n i t r a t e r e a g e n t forms a yellow precipitate
and not on h a l i t e . S c h a l l e r
on s y l v i t e
and Henderson (1932) idmtified microscopic size hematite
.~~
(Fe203)platesoccluded i n t h e margin o f t h e s y l v i t e c r y s t a l s .
When t h i s h e m a t i t i c
red rim on s y l v i t e is c o m p l e t e l y ' o r p a r t i a l l y a b s e n t , t h e s y l v i t e c r y s t a l
is either
corroded or has been recrystallized.
C a r n a l l i t e is p r e s e n t i n t h e
and 120 Marker Beds.
Tenth o r e zone and is associated with the
Clear,colorlesscarnallite
119
found i n t h e middle member of
t h e Tenth ore zone is interpreted as primary and it has ho e x t e r i o r s r y s t a l f a c e s .
Secondary c a r n a l l i t e i s o c c u r s i n t h i s
zone and v a r i e s i n c o l o r from dark yellowish-
orange (10 YR 6 / 6 ) t o dusky red (5 R 3/4).
t h e i n t e n s i t y of color
According t o McIntosh and Wardlow (1968),
i n c a r n a l l i t e i s r e l a t e d t o t h e d e n s i t y of iron oxide inclu-
sions which are present as hematite plates.
Kieserite, langeinite
and leonite are associated with sylvinite in the
member of t h e Tenth ore zone.
s y l v i n i t e a t the top of the
Potash, Lea mine.
Kieserite occurs as
a sedimentary precipitate with
lower member of the Tenth ore
zone in the National
I t a l t e r s t o epsomite on t h e mine p i l l a r s due t o exposure t o
mine a i r a t 55oF (13OC.).
Kieserite i s a l s o foundalong
it replaces sylvite. Pegmatitic crystals of langbeinite
fractures in the ore
lower
f a u l t s and f r a c t u r e s where
and l e o n i t e f i l l l o c a l
zone i n t h e Duval Corporation's NashDraw mine.
three potassic sulfate minerals replace sylvinite, floating
i n d i c a t e t h e former presence of sylvite.
When these
remnant hematite rims
20
GEOLOGIC HISTORY AND INTERRRETATION OF THE
TENTH ORE ZONE DEPOSITS
The Tenth o r e zone is a sedimentary evaporite deposit of the supersaline
environmentof
t h e Ochoan Permian basin. Evaporite lithofacies
depend on such
f a c t o r s as distance from t h e ocean connection, configuration of the depositional
f l o o r and thermalwatercuments.
The separation of polyhalite
t h e s y l v i t e and c a r n a l l i t e facies by h a l i t e f a c i e s , s h o w n i n t h i s
The area of supersaline
t l e more than the Carlsbad district
salinity of the water
environmentprobablyincluded
lit-
(Fig. 5).
The cross section (Fig. 3) after 3ones
repeatedmarineflooding
study, i n d i c a t e s
i n the saline rather than the supersaline envir-
that polyhalite should be included
onment ofdeposition.
Marker Beds from
(1954) shows the relationship of the
of t h e Permian basin i n Ochoan time.
The channels i n t h e
and i t s .temperature are reflected in the evaporite beds.
During l a t e Ochoan time the evaporation of the brines of the northeastern
The r e s u l t was the precipitation of
t h e Delaware basin went nearly to completion.
the potash salts of the Tenth ore
part of
zone.
The s y l v i n i t e and c a r n a l l i t e r o c k s i n t h e
west direction from National Potash's
Tenth o r e zone extend i n a n e a s t -
Lea mine, Sec. 18, T. 20 S , 4 . 32E, through
a d i s t a n c e of 15 miles (24 ki.lometers).
t h e Noranda Explorationproperty,
They
extend a t l e a s t 21 miles (34 kilometers) in a north-south direction (Jones,
p.199).Thesedataindicate
t h a t from the time of deposition
. .
Bed t o t h e end of deposition of the
s a l i n e b i t t e r n extendedover
some 315 square miles.
no evidenceof
of t h e 120 Marker
119 Marker Bed i n t h e Permian basin, the super-
t h e 120 Marker Bed seem t o i n d i c a t e t h a t t h e
low basin. Since
1972;
The g e n t l e d i p s on t h e t o p of
Tenth ore zone accumulated i n a shal-
karst topography i s seen a t the top of the ore
zone,
X ii"""
KILOMETERS
PALEOGEOGRAPHY
-EARLY AND MIDDLE, OCHOA TIME
I===]
TERRESTIAL ' A N D BRACKISH
WATER
DEPOSIT'S
22
t h e b i t t e r n which p r e c i p i t a t e d t h e Tenth o r e zone was still p r e s e n t a t t h e c l o s e
ofdeposition.
Thus, it appears that the
in a
Tenth o r e zone rocksaccumulated
wet by a concentrated bittern from which potassium salts were
broad, shallow basin
deposited.
Precipitation history of the Tenth ore
The p r e c i p i t a t i o n h i s t o r y o f t h e
beds is shown in Figures 6 and 7.
Zone
Tenth ore zone and i t s eelated evaporite
i s sum-
The v e r t i c a l sequenceofevaporitebeds
marieed i n Table 11':.
The o l d e s t l i t h o l o g i c a l u n i t s t u d i e d
Marker Bed (Fig. 4 ) .
is the halite rock underlying the
T h i s h a l i t e i s commonlyhomogeneous
with sulfate inclusions.
120
but sometrzimes it is banded
The banded h a l i t e shows a g r a d u a l i n c r e a s e i n s u l f a t e
ward t o t h e conformablecontactwiththeoverlying
120 Marker Bed.The
up-
anhydrite
was p r e c i p i t a t e d i n a b r i n e of s a l i n i t y from 199 t o 427 p a r t s p e r thousand(Scruton,
1952).
Then it was probably altered gradually to polyhalite
l o c a l i t i e s where t h e b r i n e wasmore
condary mineral after anhydrite, but
and sedimentary structures of the
and t o k i e s e r i t e i n
a se-
saline. Polyhalite appears to be largely
minor amounts may beprimary.
The thickness
119 and 120 Marker Beds i n d i c a t e t h a t many nearly
monomineralic s u l f a t e beds were transported and winnowed by currents over an
ex-
tensive area.
The basal bed of t h e h a l i t e r o c k above t h e 120 Marker Bed occasionally i s
banded and i s probably conformable with the underlying marker
Where t h e r e is no banding i n t h e h a l i t e r o c k , t h e
bed.
120 Marker Bedmay
been deposited during an hiatus in ha~lite precipitation. This hypothesis
ported by the occurrence of
minor corroded sylvite crystals disseminated
h a l i t e r o c k which probably crystallized in the denser,
i
have
is sup-
i n the
lower p a r t of the brine.
m
m
73
S
L
0
z
!5
L
4-
v
m
m
c,
73
U
a,
M
W
L
m
L
Y
E
N
0
S
U
m
s .
001
'"uo
W-
VI
m .
9s.
W
w
a
L
.-vl
c
.r
-ca,
-I
.r
S
w
VI
f-"
v)
v)
w
y c,.
S
Y
??
d
. w.
O
o
0
-
d
l o o
d
h.
::i
m
w
L
V
E:
Y
w
1.
4 '
2
s
T
25
TABLE
.a..
'
Precip, i t a(tion of the Tenth ore m. n e. . a i d r e l a t e d e v a p o r i t e kRds
Banded halite,
.
minor sulfates decrease
upward
Nodular to bedded h a b i t i n d i c a t e s m s t a b i l i t y
upward; little
,.
or no clay.
. .
Ei4SAL
CIAYSTONE
Maximum evaporite clsy accumdation and halite
I
solution; not alluvium.
Trace potassic menerals, locally cross-cut Tenth
ore zone.
SYLVINITE
Residual c l a y a c c i y u l a t i o n , recrystallization
art: h i g h s a l j n i t y
CRRNALLITITE
b r n d l i t i t e - s y l v i n i t e lower contact is sharp
because bi?ine which p m c i p i t a t e d carnallitite
transgressedchemically stable s y l v i n i t e . Upper
contact is gradational as r e t u r n t o lower s d l i n i t y
SYLVINITE
underlain by
Residual clay accumulation at high s a l i n i t y with
r e c r y s t a l l i z a t i o nC
. arnallitite
in basal part
of Tenth ore zone-with no bmvm c l a y probably ,
represents remnant primary sedimentation not
rep r e c i p i t a t e d as 'sylvinite.
.
CARNALLITITE
HALITE
Traco. c o M e d s y l v i t e crystals and nodules of
' p l y h a l i t e at top; minor halite bands at base.
ANHYPRITE,
POLMlALITE
Bedded to bedded nodular s t r u c ~ and
s
no basal
claystone indicates tmnsported deposit.
HALITE
(Oldest)
3
,
Usually
wed; trace clay.
m
A
.
.. .
Potassic Mineral
Facies
-Carnallite
Facies
n'sylvit:
i x i &. I
f
i
2 3
3000
Drill Holes
4'
b
0
6oundary
6000
- 9000
~12000
5
15000
6
Disunce ( f e r )
.n
27
The corroded s y l v i t e was probably partially dissolved during the diagenesis because
it was out of equilibrium with the host rock.
The h a l i t e r o c k is overlain con-
formably by t h e lower member o f t h e Tenth ore zone (Fig. 8).
Tenth o r e zone (Fig. 9) is marked by disseminated
The lower member of the
clay which probably accumulated
as the result of continual solution
i n highly saline conditions before burial.
lizationoftheevaporitepile
532 p a r t s p e r
The
salts takes place is thought t o be
s a l i n i t y where precipitation of the chloride
greaterthan
and r e c r y s t a l -
thousand(Scruton,
1953).
H a l i t e i s always presentbe-
cause sodium and chloride ions were i n excess of the other elements in the bittern.
The l i t h o f a c i e s of t h e lower member of t h e Tenth o r e zone grade from a r g i l laceous halite upward t o s y l v i n i t e and t o c a r n a l l i t i t e r e f l e c t i n g i n c r e a s i n g b r i n e
salinity during deposition.
The l i t h o f a c i e s boundarybetween
s y l v i n i t e is obscured by p o s t - b u r i a l c a r n a l l i t e metasomatism.
sometimesforms
boundary.There
tional Potash,
anenvelopearound
c a r n a l l i t i t e and
Argillaceous halite
a thinning wedge o f s y l v i n i t e a t t h i s l i t h o f a c i e s
i s a stratiform association of k i e s e r i t e w i t h s y l v i t e i n t h e
Lea mine a t the top of the
lower member.The
Na-
lower member of the
Tenth o r e zone has a sharp conformable upper contact with the non-argillaceous
middle member.
The middle member of the Tenth ore
lower member except t h a t t h e r e
is usually.noclayaccumulation.
member is probablyconformablewith
concentration of clay
zone e x h i b i t s t h e same l i t h o f a c i e s as t h e
t h e lower member.
Locallythere
is a greater
where t h e s y l v i n i t e and a r g i l l a c e o u s h a l i t e o f t h e
member a r e o v e r l a i n by t h e h a l i t e r o c k o f t h e m i d d l e
tion. There
Thus, t h e middle
i s no evidenceof
lower
member due t o minor salt solu-
even minor s a l t s o l u t i o n where s y l v i n i t e i n t h e
member is overlain by s y l v i n i t e and c a r n a l l i t i t e o f t h e
middle member.
lower
Figure 'j
Isopach map o f the lower rtlmkr o f the Tenth ore zone and i t s relationship to the thick-
ness e f s lv'inite i n the lower member, Lea County, New I)exlco (fmm branda Exploration,
Inc. dril ing (Fig.2)).
T
.
.
-
lw€ao
W
E
n&ess o f s y l v i n i t e
6 - 8 feet
a 2 feet
02 4 feet
0.
4 - 6 feet
> 'a tact
0
1.0 2.0 3.0 mles
c--"-c--4
0
1.6 3.2 1.8 Kllaateters
Isoprch cc*,:ntour of the lower d
e
r
.
29
During the deposition
of the middle member, the chloride salts appear to
have been in
a stable environment, protected from repeated solution, recrystallization and accumulation of insolubles. This would be true if they were covered
by a thick layer of brine. Therefore, the sea level in the basin was probably
higher during accumulation of the middle member than for the other
of themembers
Tenth ore zone and maintained
a brine layer over the precipitating potash salts.
3 feet
The parts of the middle member (Fig. 10) thicker
than($meter) are
in the carnallite facies. The areas of carnallite concentrations in the middle
or minor sylvin$e in the
member coincide with the concentration of carnallitite
lower member (Fig.9).
The brine which precipitated the carnallitite in the mid-
dle member probably accumulated in gentle depressions in the lower member. The
middle member is conformably overlain by the upper member. This interpretation
is supported by the gradual increase in clay concentration upward toward the co
tact but no definite claystone bed is present.
The upper member of the Tenth ore zone isofcomposed
halite, sylvinite and
carnallitite lithofacies and is similar to the argillaceous lower minber. The
increase in clay content the
overmiddle
member
may
be:due'to
a drop in sea level
i
and a concomitant increase in wind-born dust, The upper 'member is conformably
overlain by halite rock. The sylvite and carnallitite lithofacies of this stratum
in Noranda drill holes Number
1 and Number 2 is relatively minor. The halite is
commonly nonargillaceous and sometimes it is banded near its upper contact with
119 Marker Bed.
The 119 Marker Bed is present as anhydrite and polyhalite. Like the 120
Marker Bed, it becomes more anhydritic toward to northern margin of the Carlsbad
district. It conformably overlies the halite rock in places where the halite is
banded and there is no claystone seam present. The Claystone
at.the
seambase of
1
. ..
figure IO.
I
Isopach r p o f thr uiddle rakr o f the Tenth ore
Eaplorrtion. Inc. drilling ( F i 9 . a ) .
.
1
2
- 2 feet
- 3 feet
rm~.Lea County. llcw
0
1.0
clcxico( fraa Iloranda
2.0
3.0 Wlcs
c---”---3---.(
0
1.6
‘3.2
4.8 K
i
l
a
m
t
e
r
s
31
l g f t a t a local discon-
t h e 119 Marker Bed probably represented residual material
formity.
ofsuch
During the hiatus evaporites
were eroded and c l a y accumulated in water
low s a l i n i t y t h a t no evaporite minerals could precipitate.
s a l i n i t yi n c r e a s e d ,s u l f a t e s
As the water
accumulated above the claystone seam.The
appears to havepreventedtheanhydrite
from a l t e r i n g t o p o l y h a l i t e .
clay
The 119
Marker Bed is conformably overlain by banded h a l i t e r o c k .
Jones (1954, p. 109) r e p o r t e d t h a t l i t h o f a c i e s o f t h e
from t h e Delaware b a s i n t o t h e
polyhatite to kieserite;
Northwestern shelf as follows: anhydrite to
or a n h y d r i t e t o g l a u b e r i t e t o p o l y h a l i t e t o k i e s e r i t e .
I n the Noranda property, these lithofacies
western shalf north to the
change i n r e v e r s e manneron
t h e North-
limits of t h e d i s t r i c t as follows: Kieserite to poly-
halite to anhydrite. Anhydrite
may have a l t e r e d t o p o l y h a l i t e and k i e s e r i t e w i t h
i n c r e a s i n gs a l i n i t yi ns u p p e r s a l i n e
environment(Fig.
a t i o n is due t o upward migration of potassic,brine
i t should be
Marker Bed change
found i n Duval Corporation's NashDraw
6).
However, i f t h i s a l t e r -
from t h e Tenth o r e zone, then
mine twelve miles to the south-
e a s t where t h e 119 Marker Bed and t h e Tenth o r e zone have t h e l e a s t v e r t i c a l s e paration.
I t was not found there.Therefore,thealterationofanhydritetopoly-
h a l i t e was not the result of migrating
upward through the underlying potash ore
zones.
The s a l i n e sequence shows a n i n c r e a s e i n b r i n e s a l i n i t y
position of the
120 Marker Bed to the top of the middle
The high concentration
member o f t h e Tenth ore zone.
of c a r n a l l i t e i n t h i s member r e f l e c t s t h e e x i s t e n c e
brinewiththehighestsalinityinthesupersaline
position of t h e upper member of the Tenth ore
Marker 119 the water salinity decreased to
cipitated.
from the time of de-
environment.
of a
From thetimeofde-
zone t o t h a t of the claystone seam i n
a l e v e l such t h a t no potash salts pre-
The claystone marks a disconformity and the completion of an uninter-
rupted evaporite cycle.
32
Claystone accumulated at
a disconformity
as.the
result
of
solution
of
under-
lying halite rock. If the claystone seam is enveloped by polyhalite, then slow
reduction in brine salinity caused sulfate and halite to precipitate simultane
before the hiatus which caused the disconformity occurred. When deposition resumed
and salinity increasedrhalite and sulfate precipitated together to
a mosaic
build
structure which was then subjected to current action,
a decEease
and in brine
salinity with solution of halite. Anhydrite a has
low solubility so that is accumulated asa bedded almost monomineralic sediment. As salinity increased, sulfate precipitation decreased and halite became the dominant mineral above the
Marken Bed. This evaporite sedimentation would explain the sedimentsry current
structures in the Marker Bed.
over a
Scruton (1953) reported that sulfate and halite precipitate together
salinity range of 353 to 427 parts per thousand.
A sharp basal contact of polyhalite on occluded polyhalite in halite may indicate that the salinity dropped
low 353 parts per thousand and no halite precipitated. If the brine salinity increased to 427 parts per thousand, sulfate and halite accumulated together. Than
as the brine gradually evaporated to higher salinity only halite precipitated.
This explains the upper gradational contact between polyhalite bearing orange
halite and the colorless pure halite.
Schaller and Henderson (1932) believed that all the polyhalite was formed by
replacement of anhydrite because irregular remnants of magnesitic anhydrite are
closed in the polyhalite. The polyhalite crystals and multigrained aggregates proor vein-like tongues with scalloped
ject into the anhydrite as elongate crystals
margins convex toward anhydrite. A possible chemical reaction is:
(Magnesitic Anhydrite) + (Brine)+(Polyhalite)
Ca2Mg(S04)3
+ (2K+ + SOqe + 2H20) $ K2Ca2Mg(S04)4
(as)
+ (Brine)
+
(2H20)
33
The iron present in the sylvite probably did not result
carnallite, but
from 0.17 ppm Fe++found in sea water saturated to the point
carnallitedeposition(Braitsch,
in the red
from a l t e r a t i o n from
1971).
Adams (1967)found
of
thecontentofiron
rims t o be 1,800 t o 1,300 ppm by weight.Therefore,there
is about
10,000 times more iron concentrated by s y l v i t e r e d rims than is p r e s e n t i n c a r n a l l i t e .B a c t e r i a( F l i n t
may have been important
andGale,
1958) and algae(Morris
andDickey,1957)
i n the concentration of iron.
According t o Borchert and Muir (1964, p. 223) t h e primarymineralogy
in the
Carlsbad d i s t r i c t was c a r n a l l i t e + h a l i t e , or c a r n a l l i t e + h a l i t e + epsomite.
S y l v i t e was absent probably because
it cannot precipitate under equilibrium
d i t i o n s by evaporation in the temperature range
beforec6ranallite(Stewart,1963).
con-
of l l ° C t o 72OC (5Z°F t o 106OF)
The seatemperaturein
Recenttime
is rarely
above 25OC (77 F) according to Horne (1969) and t h e Permian s e a i n t h i s r e g i o n
probablynot
much above t h i s average.
Thus, s y l v i t e was not a primarydeposit.
was probably the result of leaching of carnallite
became saturatedwithpotassium.
was
by an undersaturated brine, which
Then sylvite precipitated with other
salts
(Schwerdtner, 1964) a s s y l v i n i t e or hartzsalz such a s i s present in the National
Potash's Lea mine a t t h e t o p of t h e lower member of the Tenth ore
zone.
It
34
AutogeneticEvents
zone and its r e l a t e d
Autogenetic events refer to changes in the Tenth ore
evaporites due to pressure after burial.
Because of relatively shallow depths,
temperature was notanimportantfactor.
The autogenetic events are
summarized i n
TableIIV.
The gneissic banding, as observed i n t h e Tenth o r e zone s y l v i n i t e , is interpretedtobetheresult
ofpressure(Stewart,1963).
u a l l y found i n t h e b a s a l p a r t
Halite, sylvite
The claystone seam us-
of t h e 119 Marker Bed is folded and fractured.
and c a r n a l l i t e have migrated
surfaces of the 119 and 120 Marker Beds.
laterally along the top
T h i s migration of bitterns
and bottom
i s commonly
accompained by metasomatism which i s not confined to evaporite lithofacies but cuts
acrossevaporitebeds.
For example, a dusky-red c a r n a l l i t e a g g r e g a t e may extend
from t h e lower member into the middle member.
Nitrogen gas pressure
may have contributed to this migration
Brine f i l l e d c a v i t i e s under nitrogen gas pressure are often
The source of the nitrogen
andmetasomatism.
Eound during mining.
is unknown.
Intercrystallinebrinesare
s t i l l present in the potash ores.
Howarth (1937) measured t r a c e s t o 3 . 0 oz(86
pression of 29.2 pound (13.2 kilogram)samples
grams) of brine
Greenwald and
exuded during com-
of s y l v i n i t e from a depth of 900
t o 1000 f e e t (270 t o 310 meters).
S a l t Horses in the.Tenth Ore Zone
A salt horse is a mining term used
i n t h e Carlsbad d i s t r i c t t o i n d i c a t e a
gangue salt bodY?-~which breaks the continuity of the ore
zone, t h e salt horses studied are
zone.
In t h e Tenth ore
composed of c a r n a l l i t e , h a l i t e , a r g i l l a c e o u s h a l i t e
and kieserite. Salt horses in the National Potash,
Lea mine; t h e Kerr-McGee
TMLE
,JV
..
,
Autogenetic events i n t h e Tenth o m zone and +elated evaporite beds.
RCCK TYPE
HALSTE
(Youngest)
”
“
”
”
_
. .
.’
;
No evidence
-’>
POLYIiALITE
Polylmlite
around anhvdrite and
pm%ected by clay (Schaller and- Hcndcrson,
1932)
BASIL
CLAYSIONE
Wcciated
F r a c t m ’ - f i l l i n g by c a r n a l l i t e and s y l v i t e
between. clayseone. fragnents.
Anhvdrite
Polvhalite
enveiows
ANiFiDRITE,
<
HALITE
NO
SYLVINSPE
Corrcded h e m t i t e - r i m e d s y l v i t e is suprounded.by carnallite
or
CARMALLITITE
evidence
Duslcy r e d c a r n a l l i t e m i g r a t e s uptmrd from
lover memtm
HALITE
01-
CARiiAlALITLTE
Sylvin5.t-e s t r a t u m and s y l v i t e crystals
float in camallitite and c a r n a l l i t e
SYLVDIIITE
Oj?
CAIWALLiTXTE
Remnant hematite rims f m s y l v i t e in
liibserite
No evidence
HALITE
ANHYDRITE,
POLYWUITE
Anhydrite
>
Polyhalite
->
Msalz
1 2 0 Marker k d found as both anhydrite and
p l y h a l i t e (Schaller and Hendemon, 1932)
Hartsalz fonns envelopes around polyhdlite
No evidence
36
Potash mine; the Duval Corporation, Nash Draw mine; and the Noranda core can
divided into four types: metasomatic, structurally controlled, lithofacies, and
erosional. The type of salt horse exposed at the mining face determines what
exploration method is used.
A metasomatic
salt horse is an irregularly shaped discordant body
a
with
sharp contact with the ore and awith
pegmatitic texture. There is little clay
present in the horse, except on its margins where it accumulated during salt ho
recrystallization. The size and distribution of thisoftype
salt horse are unso it is
predictable. No slumping o r collapse is observed around the salt horse,
probably formed by the metasomatic alteration after burial of the Tenth ore zon
(P1. 11)
The source of the metasomatic solutions is probably brine trapped durin
A continuburial and released during phase changes of the buried salt minerals.
a
ation of the Tenth ore zone is likely to be found by drilling horizontally
metasomatic sait horse because ita is
local secondary feature.
A structurally-controlled
salt horse originate6 by faulting and folding of
the Tenth ore zone. In the National Potash's Lea mine, the Tenth ore zone was su
jected to isoclinal folding associated with
a reverse fault. Which elevated the
5 feet (1.5 meters) higher than its normal position. Gangue
lower member about
halite rock was carried by this fault into the plane of mining operations, but
the ore resumes with a in
short horizontal distance. The cause of the folding and
faulting is unknown. The position of the Tertiary basalt dike (Jones and others,
1973).is thought tobe structurally controlled. It removed ore in the Kerr-McGee
mine.
A lithofacies
salt horse is an irregular
- shaped and randomly sized concor-
dant body. Due to variations in brine salinity at the time of deposition of the
37
Tenth o r e zone, d i f f e r e n t l i g h o f a c i e s v a r i a t i o n s i n t h e o f t h e
subzoneaccumulate.
same geologic
For example, the contact zone between t h e s y l v i n t e o r e
argillaceous halite horse in the
and an
lower member is a l a t e r a l t h i n n i n g wedge of syl-
v i n i t e enveloped by a r g i l l a c e o u s h a l i t e P1. 111. The a r g i l l a c e o u s h a l i t e h o r s e
contains rounded, disseminated polyhalite pebbles,
t h e c l a y i s moderate brown (5 Y 4/4).
no s y l v i t e , and the color of
Incontrast,thesylviniteorecontains
no polyhalite pebbles and t h e c l a y i s pale green
(10 G 6/2).
In an interval of
40 f e e t (10 meters) i n t h e Kerr-McGee mine d r i f t t h e r e is a t r a n s i t i o n from t h e
argillaceous halite horse to the sylvinite ore in the
zone.
A continuation of the Tenth ore
tion of this type
lower member of t h e Tenth o r e
zone i s n o t l i k e l y t o
befound
by penetra-
of salt horse because it is a laterally extensive primary sedi-
mentary feature.
An erosional salt horse i s anangular unconformable body.
above t h e Tenth ore zone cuts across the
upper (Pl. I V ) , middle and most of the
lower member of t h e Tenth o r e zone i n p a r t o f t h e
mine.
Clay i s highly concentrated in the halite
between t h e h a l i t e r o c k
The h a l i t e r o c k
Duval Corporation, Nash Draw
above s y l v i n i t e a t the contact
and t h e lower member of the Tenth ore
zone.
I t appears that
d i l u t e b r i n e s d i s s o l v e d and eroded troughs i n t h e margin of Tenth o r e zone s y l v i n i t e .
The h a l i t e rock of the horse
argillaceoushaliterock.
fills the trough in contrast to the sylvinite
A sink feature with channel entries
or
on a l l s i d e s , a s
described by Baar (1974), would f i t i n t o t h i s cAassification, but this geologic
phenomena is probably not present in the study area, because the Tenth ore
not exhibit
any k a r s t f e a t u r e s such as those in Ethiopia
196s). A continuation of an
(Holwerda and Hutchinson,
economic thickness of t h e Tenth ore zone i s n o t l i k e l y
t o be found by penetaation of this type of salt horse because the erosion
primary sedimentation feature
zone does
a t the margin of sylvinite sedimentation.
is a
38
SUMMARY AND CONCLUSIONS
The Tenth ore zonea bedded
is
evaporite potash deposit in the Upper Permian
(Ochoan) Salado Formation in the Carlsbad district. Sylvinite is mined in the
Duval Corporation's Nash Draw mine; the Rerr-McGee Chemical Corporation's potash
mine; and the National Potash Company's Lea mine; and it is present in the Inte
i
I
national Minerals and Chemical Corporation's potash mine; and in an area explored
by Noranda Exploration, Inc.
The Tenth zone ore mineral is sylvite and the marketed product is muria
of potash. The Tenth ore zone was intersected by the Noranda Exploration drilli
but the exploration failed to find enough tonnage of ore atonewsupport
mine
development.
The Ochoan Series is dominated by evaporitic sediments which accumulated
in a restricted saline sea within the Rermian basin. The potash evaporites were
precipitated ina supersaline environment. Structural contours on the of
topthe
120 Marker Bed indicate that the Tenth ore zone was deposited
a broad, flat
on
be due to downward movement on the west
basin. The regional southeast dip may
side of the fault separating the Delaware basin from the Central Basin platform.
The
Tenth
ore
zone
is
part
a cyclic
of sequenceof beds in which cycles of
evaporation and deposition were interruped and renewed as the brine concentration
in the basin changed.A brine of high salinity transgressed from the Northwestern
shelf into the Delaware basin whenever marine circulation in that basin became
restricted because of
a fall in sea level. The brine moved in the opposite directio
at times when the basin became open to marine circulation and the sea level r
Northeasterly
movementof the
brines
may
have
been
facilitated
by the eastward
39
tectonic tilting of the Delaware basin in late Permian time. During these transgressions and regressions, evaporitic sediments of differing composition precipbtated from brines of various salinititis and accumulated on the floor of the
A cycle of evaporite precipitation started with the sulfate (120
facies
Marker Bed). This bed is overlain conformably by halite rock and a
then
series
by
more.saline.evaporite.strata of various facies: Halite,
of increasingly younger,
sylvite and carnallite of the lower member of the Tenth ore zone, and sylvit
carnallite of the middle member. The middle member is overlain conformably by an
upper member composed of increasingly younger, less saline evaporiteofstrata
various facies; sylvite and carnallite, halite and then sulfate (119 Marker Bed).
A claysbone seam is commonly associated with the 119 Marker Beda local
and marks
so low that no evaporite minerals precipitated.
discondormity caused by salinity
Clay concentration in the supprsaline environment seems
a function
to be of the number
of solutions and recrystallizations an evaporite bed is subjected to befone bu
The lithofacies of the 120 Marker Bed grade from anydrite and polyhalite
deposited ina saline environment to kieserite a in
superline envornment. Anhydrite
was
probably
the
primary
sulfate
mineral
which
was
partially
altered
af
it was carried by currents into environments of different-salinity. The 120 and
119 Marker Beds have
a wide distribution because once anhydrite and polyhalite
have formed, they are hard and nearly insoluble. Thus they will survive transpo
by water currents. Since these marker beds are not contemporaneous with the ore
zone, they do not indicate the continuation of mineable ore.
The Tenth ore zone ranges from
6 to 10 feet
( 2 to 3 meters) in thickness.
Favorable mining conditions occur when the sylvite facies of all members of t
Tenth ore zone occur one on top of the other. This does not always happen be
each member precipitated from
a bittern witha different salinity distribution.
415
Carnallite was precipitated from the bitternthewith
highest salinity and
density, which gravitated into the depressions in the underlying strata. Carnal-
lite is usually found in localities where the Tenth ore zone is unusually thick
Often brines undersaturated in aarmablite dissolve the carmall5te amd release th
potassium ions which recombine in brines of higher salinity as sylvite with
amounts of kieserite. Therefore the sylvite facies often forms alteration shells
around incompletely replaced the carnallite facies.
The lack of clay in the middle member of the Tenth ore zone is proba
due toa rise in sea level and less dust transport, for the depth of the brine
The lack of karst features indicates that the
does not restrict sylvite formation.
Tenth ore zone was always below sea level before burial.
Autogenetic events occurred in the Tenth ore'zonedue to pressure after bu
. >
The claystone seam at the base
of the 119 Marker Bed was.fractured. Buried inter-
crystalline brines caused minor recrystallization, such as gneissic banding, whil
brine in cavities, often under nitrogen gas pressure, caused major recrystallizat
forming pegmatitic pods of ore and salt horses,
Carnallite
metasomatic
replacement
of
sylvinite
and
sylvite
to
produce
carnallitite was common. Characteristic red rims of hematite plates are found arou
sylvite crystals. The hematite plates migrate to the edge of the recrystallized
their presence "floating" in
sylvite zones. Corrosion of the hematitic or
rims
langbeinite, leoniteor kieserite is evidence of metasomatic replacement of sylvite.
The clay in the sylvite facies is characteristically pale green, in contr
to brown clay in the halite facies. Carnallite metasomatism caused the brown clay
to be chemically reduced to green clay through leaching of the ferric iron fro
brown clay by the bittern. The ferric iron recombines as hematite plates in carn
lite and sylvite.
41
of evaporite minerals and their alterations
The facies relationships
can
be
used
to
explain
the
presence
of absence of sylvinite,
and
help
to
reduce
the risk involved in reaching for sylvinite ore.
Carnallite
associated
with
some
of
the
sylvinite
ore
cause
recovery
of the Tenth ore zone is too great
blems in the mill. The insoluble content
A Tertiary basalt dike drilled on the
to permit economical solution mining.
form a costly barrier to underground mining as it has in
Noranda property may
the Kerr-McGee potash mine.
pro-
42
REFERENCES CITED
Adams, S.S., 1967, Bromine in the Salado Formation, Carlsbad potash district,
New Mexico: Harvard Univ. unpub. Ph.D. Thesis,202 p.
, 1970, Ore
in Rau, J. L.
-
controls, Carlsbad potash district, southeast New Mexico,
and L. F. Dellwig, ed., Third Symposium on Salt,
v. I :
Northern Ohio Geol. SOC., p.
246-257.
Baar, C.A., 1974, Geologic problems in Saskatchewan potash mining due to peculiar
conditions during deposition
of potash beds, in Coogan, A.H.. ed., Fourth
Symposium on Salt,v. 1: Northern Ohio Geol. SOC.,
p. 101-118.
Bailey, R.K., 1949, Talc in the salines of the potash field near Carlsbad, Eddy
County, New Mexico: A
m. Mineralogist, v . 34, p. 757-759.
Borchert, H. and R.O.'Muir,
1964,.Salt deposits -- the origin, metamorphism and
deformation of evaporites: New York, D. Van NostrandLtd.,
Co. 338 p.
Braitsch, O., 1971, Salt deposits, their origin and composition: New York,
Springer-Verlag, 297 p.
Cartwright, L.D., F., 1930, Transverse sectionof Permian basin, west Texas and
Southeast New Mexico: Am. Assoc. Petroleum Geologists Bull,,v. 14,
no. 8, p. 969-981.
Clark, F.W., 1924, The data of geochemistry:U.S. Geol. Survey Bull.770, p. 225.
Flint, R.F. and W.A. Gale, 1958, Stratigraphy and radiocarbon dates at Searles
Lake, California: Am. Jour. Sci., v. 256, p. 689-714.
Galley, J.E., 1958, Oil and geology in the Permian basin of Texas and New Mexico,
in Weeks, L.G., ed., Habitat of oil-- a symposium: Am. Assoc.
Petroleum Geologists, p.395-446.
Greenwald, H.P. and H.C. Howarth,1937, Tests of the compressibility and bearing
U.S. Bur. Mines Tech. Pub. 575, p. 18.
strength of potash salt:
Grim, R.E., J. B. Droste andW.F. Bradley, 1961, Diffraction data of
a regular mixed
in Eighth Nat'l. Conf. on Clay and
layered clay mineral inevaporite,
an
Clay Minerals: Pergammon Press, p. 228-236.
Hills, J.M., 1972, Late Paleozoic sedimentation in west Texas Permian basin:
Am. Assoc. Petroleum Geolggists Bull.,v. 56, no. 12, p. 2303-2322.
Holwerda, J.G. andR.W. Hutchinson, 1968, Potash bearing evaporites in the Danakil
area, Ethiopia: Econ. Geology,v. 63, no. 2, p. 124-150.
43
Jones, C.L., 1954, The occurrence and distribution of potassium minerals in
southeastern New Mex~ico, i n S t i p p , T.F., ed., Guidebook of southeastern
New Mexico; F i f t h Field Conference of t h e New Mexico Geological Society,
Oct. 21-24: New Mexico Geol. SOC., p. 107-112.
, 1972, Permian basinpotashdeposits,southwestern
Geology of s a l i n ed e p o s i t s :
Unesco, EarthSci.Ser.,
United S t a t e s , i n
no. 7, p. 191-201.
, 1975, Potash resources of Los bfedanos area of Eddy and Lea Counties,
New Mexico: U.S. Geol.Survey,open-filereport,
(USGS-75-407), 47p.
, C.G. Bowles and A.E. Disbrow, 1954; Generalized columnar section and
radioactivitylog,Carlsbadpotashdistrict:
U.S. Geol.Survey Pub.
, M.E. Cooley and G.O. Bachman, 1973, Salt deposits of LosMedanos area,
Eddy and Lea Counties, New Mexico: U.S. Geol. Survey,open-filereport,
(USGS-4339-7), 67p.
Lang, W.T.B., 1935, Upper Permian formations of Delaware basin of Texas and New
19,no.
2, p. 262-270.
Mexico: Am. Assoc. PetroleumGeologistsBull.,v.
Maiklem, W.R., D.G. Bebout and R.P. G l a i s t e r , 1969, Classification of anhydrite
---a p r a c t i c a l approach: Canadian Petroleum Geology Bull.,v.
17, no. 2,
p. 194-233.
McIntosh, R.A. and N.C. Wardlaw, 1968, Barren h a l i t e b o d i e s i n t h e s y l v i n i t e
mining zone a t Esterhazy, Saskatchewan:Canadian
Journ.EarthSci..v.
p. 1221-1238.
5,
Schaller, W.T. and E.P. Henderson, 1932, Mineralogyof d r i l l c o r e s from potash
U.S. Geol.SurveyBull.
833, 124 p.
f i e l d of New Mexico andTexas:
-
i n Middle Devonian P r a i r i e ':
Schwerdtner, W.M., 1964, Genesis of potash rocks
Evaporite FormationofSaskatchewan:
Am. Assoc. PetroleumGeologists
Bull.,v. 48, no.7, p. 1108-1115.
Scroggin, M.P. 1975, Personal Communication
Scruton, P.C., 1953, Depositionofevaporites:
37, no. 11, p. 2503.
Bull.,v.
Am.
Assoc. PetroleumGeologists
Smith, H.I., 1938, Potash i n t h e Permian saltbasin:Ind.
no. 8,p.
854-860.
Stewart, F.H., 1963, Marine evaporites,dataofgeochemistry:
Prof.Paper 440-Y,52
p.
Eng. Chemistry, v. 30,
U.S. Geol.Survey
United S t a t e s Department of t h e I n t e r i o r , Bureau of LandManagment, New Mexico
StateOffice, 1975, Preliminaryregionalenvironmentalanalysisrecord;
Potashleasing i n southeastern New Mexico: U.S. Dept. o f t h e I n t e r i o r ,
Bur. LandManaglement, .New Mexico State Office, 579 p.