Economic Geology
Vol. 73, 1978, pp. 1539-1555
Varietiesof GraniticUraniumDepositsandFavorable
ExplorationAreasin the EasternUnited States
JOHNJ. W. ROGERS,
PAUL C. RAGLAN'D,
RICHARDK. NISHIMORI,
JEFFREYI•. GREENBERG,
ANDSTEVEN'
A. HAUCK
Abstract
Primary uranium depositsformed by granitic magmascan be classifiedon two bases:
petrologle processof ore formation and tectonic occurrence. The processesof ore
œormation can be subdivided as follows:
1. $yngenetic,orthomagmaticdisseminations.
2. High-temperature,late-magmaticdeposits,including pegmatitestage deposits,such
as the pegmatite-alaskitedepositsof R6ssing, .Bancroft,and Crocker Well; contact
metasomaticdeposits,including occurrencesof garnetiferous skarns around pegmatite-alaskite bodies; high-temperature vein deposits, commonly associatedwith
quartz-fluorite veins; and autometasomaticdeposits, including many of the dis~
semihatedand local concentrationsin albite-riebeckitegranites.
3. Local pegmatitesformed by in situ melting of country rocks.
Basedon occurrence,granitic uranium depositscan be describedin the context of two
ideal end members: (1) anatectic, mignmtitic, pegmatite-alaskitebodies formed by remobilization of preexisting basement--a type example is the R6ssing depositof Namibia
(South West Africa )--limited geochemicalinformationsuggeststhat thesedepositshave
very low Th/U ratios, are probably rich in elementsthat are concentratedby surface
processes,and may have high initial S7$r/S6$r ratios; and (2) post-tectonic,alkali-rich
(including albite-riebeckite)granitesin stocksprobablyderived directly from mantle or
deep crustal levels in the form of aliapiriemagmas--limitedgeochemicalevidencesuggeststhat thesedepositshave Th/U ratios> 1 and are rich in elementsthat form late
differentiates during magmatic and deuteric processes;some bodies have low initial
SVSr/SOSrratios.
The precedingconsiderationspermit the selectionof sevenareas in the eastern United
States that are most favorable for the developmentof uranium depositsin crystalline,
dominantlygranitic, rocks: (1) the Lithonia Gneissof Georgia; (2) the northernNorth
Carolina Blue Ridge (GrandfatherMountain;vindowand Crossnoreplutons); (3) the
central and northern Virginia Blue Ridge (Irish Creek tin district and RobertsonRiver
and LovingstonFormations;(4) the Raleighbelt of North Carolinaand Virginia; (5)
the 300-m.y.-oldplutonbelt of Georgia,South Carolina,North Carolina,and Virginia;
(6) portionsof the White Mountain Magma Seriesof New England; and (7) the
molybdenum-copper
province of Maine.
Introduction
in graniteshaverecentlybeenreviewedby Moreau
(1977).
THE expandingsearchfor uranium ore in the United
States has extendedto many types of depositsin
The presentauthorshaveconducted
a 2-yearinvestigation of economicuranium concentrationsin
igneousrocks. Two reports have been issuedas a
addition to the conventional sandstone ores that have
beenmostproductivein the past. A numberof the
resultof thiswork. Xishimoriet al. (1977) discuss
differenttypesof ore deposits,and the problemsin- the theoreticalbasisfor explorationfor uranium in
volved in their use, have been discussedin recent
symposia
andsummaries(e.g., I.A.E.A., 1977; Jones,
1977; Ruzicka, 1977). In particular,the development of the massiveRSssingdeposit(Berning et al.,
1976) of South West Africa (Namibia) has given
impetusto the explorationof crystallinerocks. Armstrong (1974) predictsthat low-gradeporphyry-type
depositsin igneousrockswill becomemajor sources
of uraniumin the future. Someaspectsof uranium
graniticrocks,and Greenberg
et al. (1977) apply
thesecriteriato theidentification
of zonesof potential
economic interest in the eastern United States.
Uraniumis a mobileelement. In internalprocesses
in the earth (generallyin the reduced,tetravalent,form) it is classified
as a lithophilicelement
and tends to accumulate in the later differentiates of
1539
igneousmelts. It may oxidize to the hexavalent
1540
ROGERS, R./tGL./tND,NISHIiIIORI, GREENBERG../tND H./tUCK
stateas tl•c co•nplcxuranylion (I[().zI 2,) whichgen- within an ig•cous body will obviously rc,qrict the
erally permits even more extensiveseparationinto ore to the pluton. ]n homogeneous
plutonsthe ore
fluid and volatile phases. The tendency of hexa- may be distributed throughout much of the body,
valent uranium to forln fluoride and carbonate comallowingthe entire pluton to be mined,generallyfor
plexesmay enhancethis accumulation. In sediments, low-grade,large-tonnageore. In differentiatedpluthese complex ions are easily moved, thus causing tons the ore may be restrictedto specificrock types,
the ultimateformationof sedimentaryuraniumores. generallythe more siliceousand alkali-rich varieties.
All metalsposegeologicproblemsfor the explora- Similarly, contact metasomatic,pegmatitic,hydroriohist. The mobilityof uranium,however,addseven thermal,etc., depositsall have specificshapes,tenors
more complexities. In fact, the adage that "ore is of ore, and relationshipsto pluton and country rocks.
where you find it" may not be applicableto most
A second major reason for understandingthe
surficial explorationfor uranium owing to surface origin of a uranium depositis connectedwith the
leaching,transportation,and redeposition,which can surface mobilization of uranium mentioned in the
easilyremoveall indicationsof ore depositsat depth Introduction.
If surface measurements of uranium
and leave no ground or air radiometric or rock concentrations are not reliable indicators of ore at
sample anomalies. Conversely,shallow accumula- depth,then it is necessaryto discoversomeelements
tions of surfaceuranium may yield false signatures associated
with uranium that are lessreadily leached
of nonexistentburied deposits.
during weatheringand may remain as pathfinders
Thus, in the searchfor uranium in igneousrocks, for economicconcentrationsof uranium at depth.
the geologistgains an advantagewith an under- The metals associated
with uraniumclearlydepend
standingof the fundamental
geologicandgeochemical on the processof deposition.For example,primary
processes
that concentrateuraniumand the environ- uraniumin normalmembersof batholithicsequences
ments in which ore is most likely to occur. The should be closely associatedwith high concentraabsence of conventional surface anomalies cannot be
tionsof thorium; thus,high Th concentrations
in surusedto condemnpotential explorationarea, nor can facerocksmay indicateU enrichmentat depth.Consimpleairborneradiometry1napsbe usedas an indi- ßversely,vein and pneumatolyticdepositsmight showa
cation of detailed location.
closeassociationof U and Mo (which is also an acThis paperis dividedinto threeparts. First is an companimentof U in sonhesedimentaryores), in
overview of the basic igneous processesthat cause which case Mo anomaliesmight be a useful pathconcentrationof uranium and the typesof rocks in finder for uranium.
whichthesedeposits
are mostlikely to occur.Second
is a discussion of the source of uranium and the tec-
tonic environmentsin which uraniuln-rich igneous
General9eochemistryof uranium
Uranium geochemistry
has beensummarizedin a
rocksare likely to form. Third is an application
of
theseprinciplesto the delineationof favorablebelts variety of places(Rogers and Adalns, 1969a and b;
for uranium explorationin crystallinerocksin the I. A. E. A., 1970, 1974). The most important aseastern United
States.
pectsfrom the standpointof the ore geologistare:
1. The uranous(U +•) ion has a radiusof 0.89 A
This paperis restrictedto a discussion
of those
depositsin which high-uraniumconcentrations
are and fits very poorly into the latticesof major rockcausedby magmaticprocesses.Thesedepositsin- forming minerals. Thus, it tends to accumulatein
cludesyngenetic
occurrences
in granitesand occur- residualmagmasduring igneousdifferentiation.The
rences in which extensive uranium mineralization in
wall rocks is presumablycausedby fluids formed
during the magmaticcrystallizationprocess. The
paper does not cover the closelyrelated topic of
vein deposits,includingsuch well-knownsuitesas
the Hercynianmassifsof Franceand variousdeposits
of centralEurope. Hydrothermaldepositshavebeen
reviewedby Rich et al. (1977).
Uranium in Igneous Processes
uranium may then crystallizein late-stageprimary
minerals such as zircon, allanite, sphene,xenotime,
pyrochlore,or, where sufficientlyconcentrated,in
sonhemember of the uraninite-pitchblende(UOeUO2+,•) series. Sonheprimary depositsalso contain
uranothorianite,(U, Th)O2; davidite (a complex
hydrous iron-uranium-rareearth-titaniumoxide);
and brannerite(principallyuraniumtitanate).
2. Instead of crystallizingin primary minerals
within the maglnaticrock itself, the uranium may be
There are two practicalreasonswhy it is necessary sufficientlysegregatedinto volatile phasesso that it
to understand the mode of formation of a uranium
is distributedby late-stageprocesses
or escapesfrom
and
deposit. One is that the methodof formationhas a the magmachamberin pegmatitic,pneumatolytic,
major influenceon the shapeand magnitudeof the high-temperature hydrothermal fluids. Minerals
deposit.Primarycrystallization
of uraniumminerals commonlyassociatedwith this stage of deposition
GR•INITIC
U DEPOSITS IN THE E•ISTERN U.S.
1541
referredto as pegmatitedepositsin this classification.
Metasomaticdepositsof uranium (type 2B) aswholly or partly oxidizedto the hexavalentform. sociatedwith intrusiveigneousrocksare most likely
Depositionof partiallyoxidizedmaterialcommonly formedl)y the actionof ore-carryingfluids or vapors
formspitchblende(UO2+x) in veinsor hydrotherm- emanatingfrom magmas. Used here, the term metaally disseminated
deposits. Veins and broaderdis- somaticuranium depositappliesmainly to carbonate
seminations
may alsocontainuranylmineralssimilar or mafic igneouscountry rocks that have undergone
to thoseof sedimentary
depositsand includevarious metasomaticreplacementduring ore deposition;an
equivalent term would be contact replacementdesilicates,phosphates,carbonates,etc.
4. Uranimn and thorium are closelyassociated
iu posit. The depositat Mary Kathleen, Australia, has
most primary magmaticrocks,but separationgradu- been proposedas an important exampleof this type
ally occursduring igneousdifferentiation. Thus, the of deposit (Hughes and Muuro, 1965), although
Th/U ratio commonlyincreasesfrom 2 to 3 in Hawkins (1975) suggeststhat the uranium in the
mafic rocks to values of 5 to 6 in the more differdepositmay have been mobilized from preexisting
entiatedplutonsof an igneoussequence. Some of sedimentary rocks during metamorphism. Other
thisseparation
may be the resultof uraniumlossinto examplesof contact replacementare the uraniumlate-stagefluids,in part becauseof oxidationof the rich skarnsat Bancroftand R6ssing.
High-temperaturevein deposits(type 2C) gradauranium. Thorium is lessefficientlyseparatedinto
vein fluids,and thus primary igneousdepositstend tional into pegmatiticand metasomaticuranium defrom pegmatiticdepositson
to have Th/U ratios much higher than pegmatites positsare distinguished
and other uranyl silicatesiu minor amounts.
3. In late-stage, water-rich fluids, uranium is
and veins.
Classificationof processes
the basis of mineralogy. Pegmatite depositsare
mineralogicallyvery similar to their associated
intrusive mass,and vein-type depositslack someor all of
Based on the precedingconsiderations,
Table 1 the rock-formingmineralsof the associated
igneous
showsthe possibletypes of igneousprocesses
that intrusive. For example, pegmatite uranium decould lead to an economic concentration of uranium.
positsat Crocker\Vell, Australia,grade into quartz
The table also predictsthe generalform of the de- vein depositsas feldspardecreases
in the pegmatite
assemblage.
posit and indicatesexamplesof actualdeposits.
Syngeneticuranium depositsin igneousrocks
Autometasomatic
deposits(type 2D) form during
(type 1 in Table 1) form duringthe orthomagmaticthe alteration of igneous intrusives by their own
stageof crystallizationof magmas.the stageduring uranium-richfluidsand vapors. Albitizationor siliciwhichapproximately90 percentof the magmacrys- ficationcommonlyaccompauies
this type of deposit.
tallizes. Uranium-beariugminerals crystallizeat or
Metamorphic pegmatitesformed by local, in situ
about the sametime as the other mineral components meltingof crustalrocks(type 3) evolvewhenuranifof the host rock and are distributed in a disseminated erous metamorphic rocks undergo partial melting
fashion.
and form small pocketsof uraniferousmagma. This
Uranium depositsformedfrom late magmaticdif- type of mineralizationoccurs specificallyat Mt.
ferentiatesand associatedfluids and vaporsare sub- I•aurier, Canada (Allen, 1971; Kish, 1975).
dividedinto four genetictypesin Table 1. Deposits
Uranium depositsat the contactof someigneous
formed during the pegmatitestageof crystallization intrusivesare composedentirely of secondaryura(type 2A) comprise
deposits
in pegmatites,
alaskitic nium minerals, as at Austin, Nevada (Sharp and
pegmatites,or aplites that apparentlycrystallized Hetland, 1954). At the Midnite mine, Washington
after the main body of magmafrom late-stage,vola- (Xash and Lehrman, 1975; Nash, 1977), ore-grade
tile-rich differentiates. In many cases,thesedeposits concentrations
are causedlargely by secondaryproare concentrated
near the marginsof the bodies.This cesses,but soaking of the contact area around the
groupincludessomeof the largestigneousuranium principal igneousintrusive body may have caused
depositsin the world,suchas R6ssing,Bancroft,and high-temperatureformation of protore from magCrocker Well.
matically derived fluids. These depositsare not
Somepegmatiteuraniumdepositshaveundergone discussedin this paper becauseso much of the conmineral replacementor growth becauseof alteration centrationprocessappearsto have been causedby
by magmaticfluids or vaporsand are metasomatic low-temperaturefluids.
depositsin the strictest sense: see, for example,
descriptionsin Berning et al. (1976) of the R6ssing lqelationshipof processesto experimentalstudies
The depositsdiscussed
in the precedingclassificaalaskitic pegmatites. However, sincethese"metasomaticpegmatite"deposits
generallyretainthe min- tion have formed through a considerablespectrum
1542
ROGERS, R.4GLZfND, NISIII:]IORI,
Tzm. i,• 1.
GREENBERG, zlND HMUCK
Gcnctic Classification of t'l'anium l)cposit,• in Intl,•ivc
lg]]eous Rocks
1. Syngeneticdisseminations
of uranium in igneousrocksformedduring the orthomagmaticstageof crystallization
Characteristics: Primary uranium-bearing minerals such as uraninite, sphene,zircon, monazite, allanire, and pyrochlore
disseminatedthrough unaltered, nonpegmatitic igneousrocks.
Form of deposit:Has shapeof igneousbody; may be localizedin specificzonesif body is differentiated.
Examples:
Granites
Conway Granite, New Halnpshire (Billings and Keevil, 1946; Hurley, 1956; Rogers, 1964; Rogers et al., 1965);
Granite Mts., Wyoming (Malan, 1972; Stuckless, 1977); Silver Plume Granites, Colorado (Phair and Gottfried,
1964); and granitic and alkalic rocks in the easternSeward Peninsula,Alaska (Miller and Bunker, 1976)
Alkaline
rocks
Lovoze.
ro massif,Kola Peninsula,USSR (Gerasimovskyet al., 1968); Ililnaussaq,Greenland (Sorenson,1970; Bohse
et al., 1974); and Pocosde Caldas, Brazil (Ramos and Fraenkel, 1974)
Carbonatites
Oka and Lake Nippising,Canada (Rowe, 1958); Phalaborwa,SouthAfrica (Verwoerd,1967; yon Backstr6m,1974);
and Tapira (Sobrinho,1974) and Araxa (Maciel and Cruz, 1973), Brazil
2. Late-stage,high-temperaturedepositsformed from late lnagmaticdifferentiatesand associatedfluidsand vapors
A. Deposits formed during the pegmatite stageof crystallization
Characteristics:Pegmatites,aplites, alaskitic pegmatitesranging in texture from pegmatitic to aplitic; may show
evidenceof replacement(metasomatism)due to attack by late-stagemagmaticfluidsand vapors; primary uranium
minerals such as uraninite, davidire, uranothorianite, or brannerite disseminated through host rock; uraniferous
Zr, Ta, Nb, etc., minerals in alkaline pegmatites.
Form of deposit: May have shapeof pluton; commonlylocalizedalong contacts,cupolas,etc.
Examples:
Granites
R6ssing,South West Africa (Berninget al., 1976); Bancroft,Ontario (Satterly, 1957; Cunningham-Dunlop,
1967; Robinson, 1960); Olary district including Crocker Well, Australia (Campana, 1956; Raynet, 1960);
Wheeler Basin, Colorado (Young and Hauff, 1975); and Currais Novos, Brazil (Ramosand Fraenkel, 1974)
Alkaline
rocks
Pegmatitesand lujavrites at Ilimaussaq,Greenland(Sorenson,1970; Bohseet al., 1974)
B. Contact metasomaticdepositsin country rocksadjacent to igneousintrusions
Characteristics:Mineral replacementapparently causedby the reaction of magmatic fluids with country rock;
depositsoccurmostcommonlyin calcareousrocksat igneouscontacts(skarns).
Form of deposit: Irregular bodies along contacts.
Examples:
Depositsin pyroxenites
and skarnsat Bancroft,Ontario(Satterly,1957);skarnsat R6ssing,
South\VestAfrica
(Berninget al., 1976); and Mary Kathleen,Australia (Hughesand Munro, 1965)
C. High-temperature
veindeposits
gradational
into metasomatic
andpeglnatiteuraniumdeposits
Characteristics:
Distinguished
from pegmatiteuraniumdeposits
by lack of someor all mineralscommonlyfound
in igneouspegmatites;distinguished
frommetasomatic
depositsby vein morphology.
Form of deposit: Veins
Examples:
Quartz-fluorite
veinsat R6ssing,
SouthWestAfrica(Bern!ng
et al., 1976);calcite-fiuorite-apatite
veinsat Ban-
croft, Ontario (Satterly,1957);brannerite-rich
quartz vmnsat CrockerWell, Australia(Campanaand King,
1958);carbonate-hematite-fluorite
veinsat BokanMr., Alaska(MacKevett, 1963);and carbonate-fluorite
veins
at Oka carbonatite, Canada (Rowe, 1958)
D. Autometasomatic deposits
Characteristics:
Disseminations
of prilnary uraniummineralsin nonpegmatiticigneoushost rocks;crystallization
of uraniummineralsis speculatedto be approximatelycontemporaneous
with autometasomatic
alterationby
magmaticvaporsor fluids.
Form of deposit:May have shapeof pluton, but commonlylocalizednear contacts.
Examples:
Ross-Adams
deposit,BokanMt., Alaska(MacKevett,1963);and KaffoValley,Nigeria(McKay et al., 1952;
Bowden and Turner, 1974)
3. Pegmatitedeposits
formedby local,in situ,partialmeltingof uraniferous
countryrock
Characteristics:
No associated
comaglnatic
pluton;pegmatites
apparently
formedby partialmeltingof layersof biotite
gneiss.
Form: Localized concentrationsin metamorphic sequences.
Examples:
Mr. Laurier,Canada(Alien,1971;Kish,1975);andThackaringa
belt,NewSouth\Vales(WillisandStevens,
1971)
GR.4NITIC U DEPOSITS IN THE E•tSTERN U.S.
TYPE OF
CRYSTALLIZATION
ORTHOMAGMATIC
PHASES
PRESENT
PRODUCTS
XLS + MELT
PHANERITIC RX
1543
ASSOCIATEDURANIUM
DEPOSITS
URANIUM-RICHGRANITES
FROM MAGMA
AND
MELT+ XLS
AQUEOUS
FLUID +GAS
FROMAQUEOUS
HIGH-P
PEGS
I
APLITES
FLUID
OR
FLUIDS HIGH-P
LOW-P
XLS
XLS
+
+
••
LOW-P
PEGMATITE-ALASKITE-
MIGMATITE
•
I
I
•
•
I
ZONES
•
QUARTZ-FLUOR
•o
I VAPOR•
CONTACT
METASOMATIC
AND
AUTOMETASOMATIC
•
GAS
I LIQUID
• I
+
BODIES
CALCITE
VEINS
>
,,
FIG. 1. Relationshipsbetweenprocessesof uranium ore formation and cooling of granitic
melts. Portions of the diagram are modified from Jahns and Burnham (1969). The subdivision between high-pressure generation of a homogeneousgas phase and low-pressure
fractionationinto separatevapor and liquid phasesis about 1 kb (Luth and Tuttle, 1968). Progressivechangewith cobling is shown from orthomagmatic,high-temperaturecrystallization to
low-temperatureprecipitation from hyslrousphases. Uranium depositsare formed primarily
during high-temperature, high-pressure crystallization from hydrous gas phasesin pegmatitealaskite-migmatitebodiesand also during hydrothermal (vein and autometasomatic)activity at
lower temperatures and pressures.
ranging from magmaticcrystallizationthrough pegmatitic and pneumatolyticprocessesto vein-type
deposition. This spectrumcan be explainedin terms
of evidenceobtainedfrom a variety of studieson the
relationships between silicate melts and volatile
phases.
Experimentalstudiesby Tuttle andBowen(1958),
Luth and Tuttle (1968), Jahns and Burnham
(1969), and Whitney (1975) subdivide granite
crystallizationinto threegeneralstages: (1) crystallization of liquidus crystals from the silicate melt
(liquid + crystals); (2) crystallizationof liquidus
mineralsand active generationof an aqueousfluid or
vapor phase (hereaftercalledthe fluid phase) from
the coexistingmelt (liquid + crystals+ fluid); and
(3) subsolidusstagereactions,after completedcrystallizationof the silicatemelt (crystalsq- fluid).
The main body of intrusive granite crystallizes
during stage 1. Development of pegmatites and
aplites can begin with either stage 1 or 2; however,
Jahns and Burnham (1969) suggestthat the processesinvolvedin stage2 are essentialto the origin
of pegmatites. Steps 2 and 3 can bring about important exchanges of materials between the fluid
phase,the early formed crystals,and the wall rock.
These effects can inchide metasomatism,autameta-
somatism,and hydrothermalalteration. The fluids
separatedfrom granitemelts during crystallization
are generallybelievedto be important contributors
to hydrothermalore deposits(see Holland, 1972,
for a reviewof thistheory). Figure1, adaptedfrom
Jahns and Burnham (1969), illustratesthe various
stagesof granite crystallizationand correlatesthem
with the resultantrock types;the varioustypesof
uraniumdepositsthat wouldlikelybe formedat each
stageof the processare also shown.
Variationsin pressure,
temperature,
watercontent,
and volatilecontentof the magmacausedifferences
in the durationand tilningof thesethreestagesof
granitecrystallization.At low pressures
(lessthan
1 kb), graniteswith 3 to 4 percentinitial water con-
tent will exsolvea fluid phaseat sufficiently
high
temperatures
abovethesolidus
sothatcrystals,
liquid,
and fluid coexistover a large temperature
range
(X¾hitney,
1975). Secondboiling,the earlyrelease
of hydrothermalfluidsfrom magmas,is believedto
explaincertainfeaturesof porphyrycopperdeposits
and is probablyimportantfor uranium ore formation.
At higherpressures(5-10 kb), the behaviorof •vater-tmdersaturated
granitesis quite different; the
followingare someof the differences
betweenhighand l•w-pressuregranitecrystallization.
1544
ROGERS, RAGLAND, NISHIMORI, GREENBERG,AND H•UCK
1. At high fluid pressures,dissolvedsilicatesolids suresin excessof about 1 kb may accountfor the
are moresolublein the fluid phase,and fluid and melt affiliation of pegmatitic, metasomatic,and vein depositsin the vicinity of batholithsat Bancroft.
are more miscible(Tuttle and Bo•ven,1958).
2. At high fluid pressures,the compositionof the
Source and Tectonic Environments
oœ
dissolvedsolids in the fluid approachesthe comUranium
Deposits
positionof the coexistinggranite melt; at low pressures, the compositionof the dissolvedsolids apA knowledgeof the petrologicprocesses
described
aboveis necessaryin order to predict the detailed
proachesSiO= (Luth and Tuttle, 1968).
3. At pressuresin excessof about 1 kb and water- locationof uranium in and around specificintrusive
undersaturatedconditions,the fluid phase is not bodies. In order to determinebroad regionswhich
exsolveduntil the melt and crystalsare at a tem- mightbe fruitful for reconnaissance
exploration,it is
perature that is approximately 20øC above the necessaryto understandthe relationship between
solidus. Crystals,liquid,and fluid thuscoexistovera uranium concentration,the source of the uranium,
narrow temperaturerangeabovethis pressure.How- and the tectonicenvironmentin which the igneous
ever, crystals,liquid, and fluid coexist over a large body occurs. Among the most important distinctemperature range at pressuresbelow about 1 kb tions to make is the one between those areas in which
(Whitney, 1975).
uraniumhas beenreleaseddirectlyfrom the mantle
Uraniferouspegmatiticgranitesat depositssuchas into the igneoussequenceand thoseareasin which
Bancroft and R6ssing may have formed as a con- uraniumhasbeenderivedby remobilization
of earlier
sequence
of stage2 of granitecrystallization(crystals crustal materials.
+ liquid + vapor). The RiSssingdepositis discussed
more completelyin a later section,but several fea- Separationof uranium from the mantle
tures which may be explained by high-pressure The mechanismby which uranium is releasedfrom
crystallizationof hydrousgranite magma shouldbe the mantleis unclearandhasmanypuzzlingaspects.
mentioned here.
Much of the problemcanbe demonstrated
by a brief
1. Becausethe solids dissolvedin the fluid phase discussion
of Th-U-Pb systematics
in volcanicrocks.
are similar to granitein composition,
pegmatitesand Most basalts(and gabbros)of islandarcs,mid-ocean
alaskites can crystallize from this phase. The ridges, and other areas of direct mantle derivation
uranimn concentratedin the fluid phase can then containPb isotoperatios that have evolvedin mantle
crystallizein a disseminated
fashionin thepegmatites regionsin whichthe Th/U ratio hasattaineda presunder the appropriateredox and temperaturecondi- ent value of 3.5 to 4 (e.g., Tatsumoto,1966, 1969;
tions.
Churchand Tatsmnoto,1975); this Th/U ratio
2. The fluid phaseat higher pressures(greater is also characteristic of chondritic meteorites and
than5 kb) cancontainonlyabout10 percentgranitic appearsto be the primordialratio for the entire earth.
solids(Luth andTuttle.1968,p. 544). Furthermore, Oceanicandarc tholeiiticrocks,however,commonly
Luth and Tuttle statethat "the vapor changesfrom haveTh/U ratiosof 1 to 2, thussignifying
a prefergranitecomposition
to 96+ percentsilicaasthetem- ential release of uranium relative to thorium from
peraturedropsa few degrees."Thus,oncevoided the mantleinto the derivedmeltduringpartialmeltof thesegraniticsolids,the remainingfluid at lower ing.
temperaturecould constitutea more "normal," Preferential release of uranium relative to thoriron
quartz-rich,hydrothermal
solution,giving rise to may be explainableby a comparisonof the relative
hydrothermal
vein deposits;hydrothermal
vein de- bondingenergiesbetweenoxygenandthetxvocations.
posits grade into pegmatitedepositsat Bancroft. Althoughthe U +* ion is slightlysmaller(0.89 A)
While the granitic solidsare still in solution,the thanthe Th+* (0.95 A), andthusmightbe expected
in solidphases,thereare major
fluidphasecouldactasa granitizing,metasomatizingto remainselectively
in electronegativity
of the U +* (1.7) and
agent. At R6ssing,the alaskitesallegedlygre•vas a differences
values).
consequence
of metasonmtism
(Bernluget al., 1976); Th+* (1.3); (Pauling'selectronegativity
moreover,the •vall rocks surroundingthe alaskites Assigning the O--øion a radius of 1.40 A and an
apparentlywere altered by a granitizing, meta- electronegativityof 3.5 permits the use of the folsomatizingfluid, and it has been suggestedthat lowingequation(Damon, 1968) for the calculation
"granitizingfluids saturatedand replacedalready of bondingenergy:
migmatizedcountryrock" (Berning et al., 1976,p.
330 Z•(1 -- e-ø.2•a•)
BE=
361).
3. The narrow temperaturerange (lessthan 20øC)
R
that separatesthe magmatic,pegmatitic,and hydro- whereBE: bondingenergy,Z• = chargeon cation,
thermal stagesof crystallizationof granitesat pres- /x = electronegativity
differencebetweencation and
GRANITIC U DEPOSITS IN THE EASTERN U.S.
1545
anion,and R. = sumof cationand unionradii (inter- hydrothermaldeposits,pitis the possibilitythat some
atomicdistance). The restiltsof this calculationare siliciclnagmasmay be sufficientlyenrichedin urabondingenergiesof 320 kcal/molefor U +• and 394 nium that the primary, crystallizedrock itself could
kcal/molefor Th+•. If the bondingenergywith be a sourceof low-grade,disseminatedore.
oxygenis the critical factor in determiningthe release of elementsfrom solid phases,the uranium Relationshipof uranium depositsto geologicage
Relationships
of uranium depositsto geologicage
would be expectedto be releasedpreferentiallyto
and/or processesof crustal evolution have been
thorium, thus explainingthe relatively low Th/U
ratiosin primary maficrocks. The tendencyof the discussedby a number of writers (e.g., Robertson,
Th/U ratio to increasetowardthe later differentiates 1974; Xishimori et al., 1977; Robertsonand Tilsley,
of igneoussequences
is opposite
to thepredictionthat 1977). One of the bestexamplesof an age relationwould be made on the basis of bondingenergy cal- ship is the concentrationof uranium in basal Prowhich has been attributed to
culations,but the ratio may be largely controlledby terozoicconglomerates,
lossof hexavalenturaniumfrom the magmachamber a variety of processes,suchas changein atmospheric
compositionat the end of the Archeart or release of
during igneousdifferentiation.
In short,there is a poorlyunderstood
mechanism uranium from the earth's interior during an end-ofby which uranium is releasedfrom the mantle into Archeartorogenicpulse. Uranium depositsare also
liquid and fluid phases. •¾here these phasesare common in Grenville-age terranes (e.g., Bancroft,
mafic magmas,the concentrationin the crystallized Ontario) and in Pan-African orogenicbeltsof 500 to
rocks is generallylow (1 ppm or less), and sig- 600 m.y. age (e.g., R6ssing,Nambia; easternEgypt;
nificant concentrationof uranium must depend on Currais Novos, Brazil). The reasonsfor the concrystallizationdifferentiationor possiblyeven liquid centrationof uranium depositsat a particular time
ilnmiscibility (Philpotts, 1976). This differentia- are unknown,but theymaybe relatedto the necessity
tion producesrockswith uraniumconcentrations
up for accumulatingradioactiveelementsin the upper
mantle and lower crust for considerable
periodsof
to a maximum of a few tens ppm and having Th/U
ratiosin thevicinityof 5. Concentrations
of uranium time in order to supplythe energyneededfor worldhigh enoughto be economicprobablycan be obtained wide orogenicpulses.
One very significantobservationhas been the
in such rocks only by separationof uranium into
late-stagevolatile phasesand localizeddeposition absenceof uranium depositsfrom Arcbean terranes.
This absencecorrelateswith the generallylesslithofrom hydrothermalfluids.
It is possible
thaturaniumnmybereleased
fromthe philic compositionof the Arcbean crust than of the
mantlenotonlyintomagmasbut directlyintovolatile Proterozoic crust (e.g., Eade and :Fahrig, 1971).
phases.Thispossibility
is supported
by the evidence One explanation for this observationcould be that
cited above for the ease of separationof uranium
from the mantle.
mantle differentiation
and crustal evolution
occurred
Such broad release of uranium
only to a limited extent in the Arcbean and generally
mightbe expectedto yieldareasof regional,moderate did not producelithophile-rich,granitic crust in siguranium mineralization,with the possibilityof high nificant amounts. An alternative explanationis that
concentration in localized zones of favorable strucArcbean crust was originally as uraniferous as
younger crusts but lost mobile elements such as
ture or wall-rock lithology.
uranium during later orogenicactivity.
3[obilizationof uraniumby crustalreactivation
of i,qneous
uranium deposits
Mobilization of uranium from preexisting crustal Tcctmticclassification
Basedon thesegeneralconceptsfor the generation
of uranium-richmaterials,a classification
canbe proposedfor igneousuranium depositsthat placesthe
process of uranium mineralization in its tectonic
setting. For this purpose, two end members of
igneous depositshave been established: the Bokan
Mountain depositof southernAlaska, which is considered to be an ideal example of mantle-derived
uranium: and the R•3ssingdeposit of South Wrest
Africa (Namibia), which is consideredto be an ideal
example of anatecticremobilizationof preexisting
sialic crustal material. The identifying characterlater differentiate to fluids. In either case, there is isticsof thesedepositsare shownin Table 2.
the possibilityfor the developmentof regionalor local
BokanM'ountain: The BokanMountaindepositof
rocks is the secondlikely possibilityfor a sourceof
mineralizingfluids. In particular, sedimentaryprocesseshave the ability to concentrateuranium into
certain rocks (e.g., organic-rich shales) and to
separateit from thorium (e.g., into organic-rich
shalesand other rocksof low Th/U ratios). Anatectic processes
may then operateeither on primary,
felsic igneousrocks containingmoderate levels of
uranium enrichmentor on sediments,which may contain moderateto high initial uranium concentrations.
Theseanatecticprocesses
may eitherproducevolatile,
mineralizingphasesor felsic magmas,which could
1546
ROGERS, RAGLAND,
NISHIMORI,
GREENBERG,
AND
HA UCK
T•tBLE 2. Summary of Principal Differencesbetween the R6ssingand Bokan Mountain
Models for Granitic Uranium Deposits
Characteristic
R6ssing Model
Lithology
Pegmatite-alaskite-gneiss;anatectic
granite and migmatite
Derivation
Reworked and recycled sialic crust
Generally greater than 0.710
Generally less than 1.0
Deep
Initial Sr isotope ratios
Th/U ratios
Levels of erosion
Levels of emplacement
Tectonic stage
Age
Tectonic setting
Metamorphic rank of country rocks
Bokan Mt. Model
Alkaline and/or peralkaline granite; associated syenites; commonly albiteriebeckite granite
Mantle
or Iower crust
Generally less than 0.710
Generally greater than 1.0
Shallow
Catazonal
Epizonal
Syntectonic
Commonly Proterozoic to early Paleozoic
Orogenic
Middle- to upper-amphibolite
Post-tectonic
southeastern Alaska is associated with a Mesozoic
Any age (post~Archean)
Anorogenic or post-orogenic
Any rank (including unmetamorphosed)
As indicatedabove,Bokan Mountain and many
intrusion of peralkalinealbite-riebeckitegranite. The post-tectonicplutonsare consideredto be mineralizapluton is a post-tectonicplug intruding geosynclinal tion sitesof uraniumderivedfairly directlyfrom the
sedimentsof upper Proterozoicand lower Paleozoic mantle. There is, of course, no absoluteproof of
age (Churkin and Eberlein, 1977). Four types of this sourceof uranium,and the proposalis basedon
uraniumdepositshavebeenrecognizedby MacKevett the following considerations.
1. The Bokan Mountain plutonshowsno evidence
(1963) in .the Bokan Mountain area: (1) primary
disseminationsand segregationsof uranium minerals of havingbeenproducedby localanatexis,in strong
in the peralkalinegranite--it appearsthat the min- contrastto the stratigraphicallyrestrictedmigmatites
erals becamemore concentratedin the later phases of the R6ssingarea (describedbelow). The nature
of crystallization,possiblyas a result of magmatic of the crust into which the Bokan Mountain pluton
hydrothermalactivity; (2) primary mineralization was intruded is uncertain. Churkin and Eberlein
(syngenetic)in the aplitesand pegmatitesassociated (1977) cite limited evidencethat the southernpart
with thegranite; (3) secondary
hydrothermaldeposi- of Prince of Wales Island, containingBokan Mountion (epigenetic)in veins and fractureswith some tain, containstrondhjemiticigneousrocks,as old as
sediments.
replacement; and (4) secondary hydrothermal 700 m.y.,intrusiveintoearliergeosynclinal
This observationmight indicatedevelopmentof a
depositionin poresof clasticsedimentaryrocks.
With very few exceptions,the uranium deposits sialic crust in late Proterozoic time, which would be
are in or near the granitestock. The exceptionsin- consistentwith the generaltendencyof alkalineigneclude prospectsin an older seriesof pegmatitesas- ous rocksto intrude areasof crustalstability.Eugeosociatedwith quartzmonzonite-granodiorite
and one synclinalactivity in the area, however,continuedat
prospectin a fracturedmafic dike. There can be leastthroughthe lower Paleozoic,which raisesqueslittle doubt, however, that the main source of the tionsas to the degreeof crustalstabilityin any porAlaska area. Thus, although
uranium is the peralkalinegranite. The ore-forming tion of the southeastern
processmay havetakenplacein two stagesor it may it is conceivable that sialic crust was available for
have acted in a continuousprogression. MacKevett anatecticor sedimentaryrecycling to produce the
(1963) discussed
a two-stageprocessin which a Bokan Mountain magma, there is far less evidence
peralkalinegranite of anomalousuranium content for suchan origin than there is for the RSssingarea
initially crystallizedto form the types 1 and 2 con- and similar miglnatitic, syntectonicterranes. Therecentrations. Sometimelater, hydrothermalactivity fore the presentwriters considerthat the mostlikely
moved uranium-rich solutionsinto the surrounding origin for the Bokan Mountain magma is either a
country rocks and thus produced types 3 and 4 partial melting of the mantle or a partial melting
deposits,
whichare the principaluraniumoccurrences of sedimentsformedby the erosionof eugeosynclinal,
in the Bokan Mountain area. The contrastingcon- mantle-derived,volcanic and plutonic rocks. The
tinuous processrequires the hydrothermalenrich- lack of cratonic contribution and the mantle source of
ment system from granite to country rock to be such eugeosynclinalassemblageshas been discussed
originally magmatic. That is, the same magmatic by Rogers and McKay (1972).
2. Insofar as chemical evidence is available, the
flnids that causedthe primary uranium ore mineralizationwithin the granite also producedmineral- Th/U ratio of the Bokan Mountainpluton appears
ized aplitesand pegmatitesand enrichedthe country to be high (greater than 1). A Th/U ratio greater
rock in uranium.
than 1 is generally characteristicof such mantle-
GRANITIC
U DEPOSITS
IN THE E,4,S'TERN U.5'.
1547
derived volcanicrocks as mid-oceanridge basaltsand
The principal cvidcncethat man.• oœthe g•anitcs
in the deeplyerodedportionof the Damaran belt are
anatectic and/or syntectic is the stratigraphic restrictionof two of the major intrusivetypes. One of
the older granites (G4) is the major host of the
uranium depositsand is restrictedprinmrily to the
Xosib MetasedimentaryGroup, with some metamorphismof marblesin the overlyingR6ssingFormation and nilnor intrusion into younger metasedimentary rocks. The developmentof skarns along
cess.
contactsof G4 and the R6ssingmarbles,plusthe con4. Some post-tectonicplutons with geochemical formity of overlyingmetasediments
with the R6ssing
similaritiesto Bokan Mountain have initial *YSr/S6Sr Formation,indicatesthat G4 postdatesmost of the
ratiosof 0.705 and lower (see Table 3 and discussion sedimentationin the area, and thus its restriction to
in next section). These low ratios indicate deriva- the Nosib Group is prestonablythe result of very
tion of the magmasby partial meltingof the mantle local anatectic derivation of the G4 melt. The G4
or primitive, possiblylower, crust with low Rb/Sr granite at R6ssingalso has a high *YSr/SøSrinitial
values. Strontium isotopic data, however, are not ratioof 0.734 (Kr6ner andHawkesworth,1977).
High uranium concentrationsare associated•vith
availablefor Bokan Mountain.Wenner et al. (1978)
have found low •sO/•O initial ratios in some 300- the G4 granites. Thesegranitesconsistprimarilyof
m.y.-old,possiblymantle-derived,plutonsof the Ap- quartz and alkali feldsparswith minor biotite. Mafic
palachianpiedmont,which may be Bokan Mountain- mineralsare sufficientlyscarcein most samplesthat
type with respectto uranium potential. The low the G4 has been referred to as an alaskite. Anhedral
•sO/•O ratios are generally correlatedwith loxv textures predominate,and the grain size is highly
initial sYSr/S6Srratios. Oxygen isotopedata, how- variable,becomingpegmatiticin manyplaces. There
ever, are also lacking for Bokan Mountain, and the is no readilydiscernible
patternof grain-sizevariausefulnessof this geochemicalcriterion is not yet tion.
clear.
The uranium in the G4 granite is very irregularly
RSssing: The RSssing deposit of South West distributed. Uranium valuesrange upxvardfrom 30
Africa (Nantibia) occursin the Damaranorogen,a ppm to 1,000 ppm or more, and Th/U ratios are
northeast-southwest-striking
belt most recently de- very low (<<1). High concentrationsof U are
formed in Pan-African time, about 500 m.y. ago. particularly noted near contacts with the biotite
(Clifford, 1967; Jacob,1974). The orogenextends schistsof the Khan MetasedimentaryFormation,and
continentaltholelites (Rogers and Adams, 1969a).
Conversely,Th/U ratiosgreaterthan 1 are not found
in magmaticrocksproducedby local anatexis,as at
R6ssing. Too muchrelianceshouldnot be placedon
Th/U ratios of surfacesamples,however,owing to
the continualmobilizationof uranium by ground
water in near-surfacerocks (e.g., Stuckless,1977).
3. As discussedabove, substantialreleaseof uranium from the mantleappearsto be a commonpro-
between older cratons to the southeast and northwest.
in some contact zones uranium
has been added to the
The belt is approximately400 km wide, and the Khan Formation by fluids from the granite. Much
regionaltrend is northeast-southwest
in all portions. of the high-uraniumgranitecontainsslightlyhigher
The southeastern one-third of the width of the belt is
concentrations
of biotite
than the remainder
of the
a graywackeassemblage
that may be ensimatic,but granite. Particularly high concentrations
of uranium
evidenceof suturing between the cratons on either are commonlyassociatedwith smoky quartz because
side has not been found within the exposedportions of the development
of the smokyappearance
by radiaof the belt.
tion damage. Uranium is also commonlyassociated
The northwestern
two-thirds
of the Damaran
with reddish, ferruginous zones, although it is not
orogencontainsa wide variety of rock types. The clear whether these discolorations
are causedby
entire area appearsto be underlainby preexisting maglnaticor weatheringprocesses.
(possiblyArcheart) sialicbasement,now exposedat
Reported mineralogy at R6ssing indicates that
numerous places as mantled gneiss domes. The about60 percentof the uraniumis in primary minbasementis overlain by quartzites,arkoses,marbles, erals (chiefly uraninite) and 40 percentin a large
and other shallow-water
sediments that have noxv variety of secondaryminerals. The extent to which
been metamorphosedto moderate- to high-rank the variability of uranium concentrationsin the
gneissesand schists. The belt appearsto pitch to variousgranitesis causedby primaryor by secondary
the northeast, thus exposing deeper levels of the processesis unknown. Furthermore, there is no
orogentoward the southwest,near the coast. High clear evidenceto indicate whether the secondary
uranium concentrationsoccur in the more deeply uranium mineralizationis hypogeneor supergene.
erodedportionsof the orogen,wherebasementrocks, Most of the uranium values in the Khan Formation
high-rank metasedimentaryrocks, and anatectic near its contactwith G4 are in secondaryminerals
granitesare closelyintermingled.
insteadof uraninite,and thus it seemslikely that at
1548
ROGERS,RAGLAND, NISHIMOR[, GREENBERG,AND H.4UCK
k'a.•t.,•,lmmc
of t],' .•,cc•lary •li.qrilm•i• is caused
lmx'cl•{'t'•lctt'cclivc•ttlring llm c;,rlv l•i.5•,,ry,ff tl,c
latemagmaticprocesses.A numberof workers(e.g., cartlband igneonsnraniumdel)ositsare unknownin
Jacob and •ambleton-Jones, 1977), however, em- Arcbean rocks.
phasizethe importanceof supergeneactivity.
Table 3 showsa number of igneous-related
uranium deposits and their principal characteristics.
Significanceand examples
Many of themcomparecloselywith BokanMountain
As indicatedin the precedingdiscussion,recogni- or RGssing,
thusindicatingthe generalvalidityof the
tion of the sourceof the igneousbodyand of tectonic two-foldclassification.Somedeposits,however,have
conditions during its formation is important for characteristics intermediate between those of the two
explorationpurposes. In general,only vein-typede- end-membervarieties. In particular:
positswill be of major importancein areasof post1. Depositsin Wheeler Basin, Colorado(Young
tectonicplutonsof the Bokan Mountain type, whereas and Hauff, 1975), showmanyelements
of similarity
disseminated
depositsmay be found in R•ssing-type to RGssing. They occur in gneiss-migmatiteterbodies.
ranes,are concentrated
in zonesthat havebeenhighly
Both the Rbssingand Bokan Mountain types of injectedby the 1.4-b.y.-oldSilver Plume Granite,
depositsform only under conditionsthat permit and occurin rocksin the upperamphibolitefaciesof
considerable
fractionation
of uranium
from initial
naetamorphism. Principal uranium concentrations
source rocks. At R6ssing, this fractionation has are in biotitic massesscatteredthroughoutthe inconsisted of igneous differentiation following ex- jection zone. The major uranium mineral is uranitensivecrustalreworking during the complexhistory nite, with minor uranophaneand other uranyl minof the Damaran orogenicbelt, which may involve erals. The only significant differences between
several cyclesof igneouscrystallization,sedimenta- WheelerBasinand RGssing
are that the Th/U ratio
tion, metamorphism,and anatexis. At Bokan Moun- of the Silver Plume host rock at XVheeler Basin is
tain, the fractionationhas beenaccomplished
by the high (as muchas 10; Phair and Gottfried,1964) in
productionof a highly differentiated,alkali-rich,and contrastwith the very low Th/U ratio (< 1) in the
peralkaline melt and an ultimate releaseof volatiles. GagranitesnearR6ssing;and that, whereasR6ssing
Neither of thesefractionationmechanisms
appearsto wasformedin an area of ensialiccrustalreactivation,
this process has not been identified at XVheeler
TABLE 3.
Examples of Granitic Urauium Deposits
Bokan
Mountain
1. Cretaceous granites of Seward Peninsula, Alaska (Miller,
1972; Miller and Bunker, 1976; Staatz and Miller, 1976)
2. Early Tertiary and some Precambrian (Pikes Peak')
plutons in Front Range, Colorado (Wells, 1960; Phair
and Gottfried, 1964; Phair and Jenkins, 1975)
3. White Mr. Magma Series, New England (Billings and
Keevil, 1946; Adams et al., 1962; Rogers, 1964; Rogers
et al., 1965)
4. Younger Granite at Kaffo Valley, Nigeria (McKay et al.,
1952; Bowden and Turner, 1974)
5. Younger Granites of Red Sea Hills, Egypt (Hussein et al.,
1970; Hussein and E1 Kassas, 1970)
R6ssing
1. Wheeler Basin, Colorado (Young and Hauff, 1975)
2. Charlebois Lake, Saskatchewan (Mawdsley, 1952; Lang
et al., 1962; Beck, 1970)
3. Bancroft, Ontario (Satterly, 1957; Robinson, 1960; Lang
et al., 1962; Cunningham-Dunlop, 1967)
4. North shore of St. Lawrence River, Quebec, including
Sept Iles, Bale Johan Beetz, etc. (Baldwin, 1970)
5. Crocker Well, Olary district, Australia (Campana, 1956;
Campana and King, 1958; Johnson, 1958; Raynet,
1960; Thompson, 1965)
6. Six Kangaroos area of Cloncurry-Mt. Isa District, Australia (Brooks, 1960; Carter et al., 1961)
7. Nanambu, Nimbuwah, and Rum Jungle complexes of
Katherine-Darwin area, Australia (Dodson et al., 1974;
Ayers and Eadington, 1975)
8. Currais Novos, Brazil (Favali, 1973; Ramos and Fraenkel,
1974)
9. Minor gneiss and mlgmatite in Laborador uranium area
(Beavan, 1958; Gandhi et al., 1969)
Basin.
2. The Conway Granite of New Hampshire is the
principal member of the Mesozoic, post-tectonic
XVhite Mountain Magma Series, which occursin a
variety of ring dikes and plugs throughout New
England. The granite has a number of similarities
to Bokan Mountain, includingits post-tectonicintrusion into a former geosynclinalterrane and a high
Th/U ratio. The Conway Granite, however, is
dominantly potassic,rather than sodic; also, peralkalinity is shown by other membersof the series
rather than by the Conway Granite. The Conway
Granite is largely a potential thorium resource
(Adams et al., 1962), and uranium concentrations
rarely exceed20 ppm. It is possiblethat somesmaller
bodiesof the White Mountain Series, which are also
more sodicand peralkaline,may be better potential
uranium sources(e.g., four bodiesin Vermont discussedin a later section).
3. The albite-riebeckite
granitesof Kaffo Valley,
Nigeria, are similar to Bokan Mountain in virtually
all petrologic respects, including post-tectonicintrusion, sodic and peralkaline character, vein and
disseminateduranium deposits, and high Th/U
ratiosin hostrocks. The Kaffo Valley granites,however, were intruded into a craton stabilizedin Proterozoictime, whereasthe Bokan Mountain pluton
intrudeda terraneof uncertaincrustalcharacteristics;
GRANITIC U DEPOSITS IN THE E.4STERN U.S.
1549
cugc•,,•y•cliJ•al
activity, l,,wcver, 1)crsistc(lin tile r•,cl<s. The ;[l'Ca,ll•c11,lllaV lit' all CXatlq,lc•,f ilw
Bokan Mountain area at least througllout h)wcr direct rclcasc of uranium œro•n the mantle in volatile
Paleozoictime. Both the Kaffo Valley and Bokan phases.
Mountain areaswere apparentlycrustallystabilized
at the time of intrusion, which may be the only requirementfor the developmentof the igneoushost
Igneous Uranium in the Eastern United States
The precedingsectionscan be summarizedin the
form of a setof criteria that can be usedto judge the
Another possiblyanomalouscharacteristic
of the favorability of an area for uranium explorationand
Kaffo Valley plutonmay be its initial a*Sr/SøSrratio. the varieties of depositsthat the area may contain.
The ratio has not been determinedfor Kaffo Valley These criteria are the following.
itself,but measurements
on an apparentlycorrelative General (for all types of deposits):
body (Arno) of the Nigerian Younger Granite suite
1. Belts or regionsof broadly similar geologicfeayield an initial a*Sr/SøSrratio of 0.7212 (Bowden tures in which nranimn nfineralizationhas already
and Turner, 1974). This high ratio contradictsthe been reported in several (preferably numerous)
conceptof mantle derivation of the pluton. Unfor- areas. Although, as discussedabove,the mobility of
tunately,no strontiumisotopework hasbeendoneon uranium makes it impossibleto predict uranium
the Bokan Mountain pluton,and thus adequatecom- concentrationsat depth from surfacemeasurements,
parisonscannot be made.
geologicallyhomogeneousareas that do not contain
4. Uranium depositsassociated
with the Younger reported uranium occurrencessomewhere must be
Granitesof the Red SeaH/Ils of Egypt are enigmatic. considered less favorable than those that do.
rock.
The Younger Graniteswere formedin Pan-African
2. Abundance of silicic and alkali-rich
intrusive
time (500-600 m.y. ago), have low initial s*Sr/•Sr rocks. Uranium tendsto concentratein thesehighly
ratiosof 0.702to 0.706,are highlypotassic,
and range. differentiatedrock types.
from peralmninousto slightly peralkaline (Rogers
3. Presenceof suitablestructural traps and wailet al., 1978). They are clearlypost-tectonic
andthus rock lithology to prolnote depositionfrom volatile
mightbe expectedto comparewith BokanMountain. 1)hases.
MeasuredTh/U ratios,however,are approximately 4. Abnndanceof fluorite or other fluorine-bearing
2 (Rogerset al., 1978), whichis clearlyin the range phases. These mineralsindicate the availability of
of mantle-derivedmagmaticrocks but considerably fluorine,which apparentlyaids in the distributionof
lower than the 4 to 6 expectedof highly potassic uranium because of the formation of uranium-fluoride
granites(Rogersand Adams,1969a).
complexes.
The lower-than-expectedTh/U ratios in the
5. Post-Archeanageof the magmaticactivity. As
Younger Graniteslead to interestingspeculationsdiscussed
previously,for somereasonArcheau rocks
concerning
the sourceof the nranimnfor the entire are impoverishedin lithophilic elements such as
area. Completemineralogicalstudieson the occur- uranium.
rence of the uranium have not been made, but radio-
metric surveysclearly showthat uraniumminerals
are disseminated
throughthe morefelsicgranitesand
in broad zonesin the surroundingwall rocks. If the
uranium
mineralization
R6ssing-typedeposits:
1. Occurrence in zones of crustal remobilization;
ensialic
belts
deformed
between
cratens
or
era(on
in the wall rocks resulted
fragments. The high concentrationof uranium in
from uranium-bearing
fluidsescapingfrom adjoining these depositsapparentlyhas its original sourcein
granites,then the Th/U ratio in the sourcegranite sialic crustal rocks.
should increaseas a result of the uranium loss; this
2. Medimn- to high-rank metamorphic terranes
processhas been proposedto explain the general (amphibolitefacies). The depositscan form only in
tendency
for morefelsicigneousrocksto havehigher areasof migmatizationand anatexis.
3. Pegmatitic,highly silicicgranitesand pegmatite
Th/U ratiosthan moremarievarieties(Rogersand
Adams,1969a,b). Thus, Th/U ratiosof 2, instead (likes and veins, in which the uranium-bearingvolaof the expected4 to 6, in the Younger Granitespre- tile phasescan concentrate.Metasomaticallyaltered
sumablyindicatethat the uranimn in the area was pegmatitesare of particular interest.
4. Contact zones of pegmatite-aplite-alaskite
not derived from the plutons themselves. One
explanation
is that the entirearea,includingplutons bodies. These zonesare areasof particular concenand wall rocks,was soakedin uranium-bearingfluids tration of volatiles; in some casesparticularly high
structurallyassociated
with the granitesbut derived concentrations of uranium are associated with biotitic
from some source at depth. This processwould zones.
5. High initial s;Sr/•6Sr ratiosindicativeof crustal
explain both the comparativelylow Th/U ratios of
the granitesand the dissemination
of uraniumin wall remobilization.
15,50
ROGERS, R.4GL.4ND, N[SHhl•ORI r, GREENBERG, .4ND H.4UCK
•,. Commonly
a•st•ciatcd
ttuorinc(Grcenbcrgct aI.,
1977).
Mountain windo•v,which seemsto fit a R/sssing
model; and the Crossnoreplutons,which have propertiesof both R6ssingand Bokan Mountain.
Bokan •[ountain-typedeposits:
The Grandfather Mountain window contains up to
1. Post-tectonic
plutonsintrudingany variety of 6,000 m of arkoses,siltstones,shales,and conglomwall rocks. Possiblymost importantin areas of erates(GrandfatherMountainFormation)overlying
former ensimaticgeosynclinal
activity.
a varietyof granites,gneisses,
and augengneisses
of
2. Sodicplutons,generallywith high concentra- Grenville age (about 1,000 m.y.). All rocks aptionsof albite; possiblyperalkaline(shownby pres- parently underwentlow-rank metamorphism
about
enceof riebeckite,etc.).
3. Abundance of favorable structures and wall-
350 m.y. agoand nov½
appearas a windowthrough
the major Blue Ridge thrust sheet. A more com-
rocklithologies.Mostof thesedeposits
are probably plete descriptionof the geologyis given by Bryant
veinsand hydrothermaldisseminations.
and Reed (1970).
4. Major pathfinderelements
may be thorium,nioUranium occursin variouswaysin the Grandfather
bium, and fluorine.
Mountain windo•v.
The \Vilson Creek Gneiss con-
Basedon thesecriteria,a generalsurveyhas been tains uraninite-filledjoints in shearedpegmatites
madeof crystallineterranesin the easternUnited localizedalong phyllonitezones. Heavy mineral
States; the detailsare reportedby Greenberget al.
beds in the Grandfather Mountain Formation (as
(1977). Sevenareashavebeenchosen
ashavingthe well as the ChilhoweeGroup of an overlyingthrust
greatestpossiblepotentialfor •urther uraniumex- sheet)containmetamict
zirconandallanire.Abunploration (Fig. 2).
R6ssing types:
danceof thesemineralsin generallyarkosicrocksis
one of the criteria listed by Dennisonand Wheeler
(1975) for potential
sandstone-type
uraniumores.
The Crossnore
plutonic-volcanic
groupcontainsa
(Grandfather
MountainwindowandCrossnoreseriesof peralkalinegranitesand gabbrosintrusive
1. the Lithonia Gneissof Georgia;
2. the northern North Carolina Blue Ridge
intothe BlueRidgebasement
complex.The granites
plutons);
similarto volcanicrocksof the Grand3. the central and northern Virginia Blue Ridge arechemically
(Irish Creektin districtand Robertson
River father Mountainand Mt. RogersFormations(Rankin, 1975) andare characterized
by the presence
of
andLovingstonFormations);and
4. theRaleighbeltof North CarolinaandVirginia. aegerineand/or riebeckitewith commonaccessory
Bokan Mountain-type deposits:
fluorite. The granitesare alsorich in Nb, Y, and
rare earth elements. Although the granites have
1. the 300-m.y.-oldplutonbelt of Georgia,South manyof the properties
of BokanMountaindeposits,
Carolina,North Carolina,and Virginia;
they also have initial s•Sr/S•Srratios of 0.7125
2. portionsof the \Vhite MountainMagmaSeries (Odom and Fullagar,1971), indicativeof crustal
of New England; and
reworking. Geochronologic
studiesof the granites
3. themolybdenum-copper
province
of Maine.
areinconsistent
(Rankin,1970;OdomandFullagar,
age.
As discussed
below,the placingof someof theseareas 1971) but generallyagreeon a late Precambrian
Rankin
(1975)
believes
that
the
series
was
associated
into the R6ssingor B.okanMountain categoryis
problematical,
andsomeareasappear
to contain
both with crustal rifting.
The centralandnorthernVirginia BlueRidgeconThe Lithonia Gneissis a layeredgranitic gneiss tainstwo areasof potentialuraniumdeposits:the
containing
numerous
peglnatites
andshowing
fiuidal Irish Creektin district,RockbridgeCounty;and the
structure. It is in the sillimanitegrade of metamor- Robertson River Formation and Lovingston Gneiss
types.
Counties.
phisre. The gneissprobablyrepresents
metamor- in Greene,Madison,andRapahannock
phisinof Precambrian-early
Paleozoic
rocksabout The Irish Creek tin district is formed in a pregranodioriteintru4.50m.y.ago (Butler,1972); it hasbeenintruded sumedPrecambrianhypersthene
gneisses.The granodiorite
by thepost-tectonic
StoneMountainGranite,which siveintoquartz-feldspar
Tin occurs
hasan Rb-Sr isochronageof 291 m.y. and an initial is olderthantheregionalmetamorphism.
as
cassiterite
in
quartz
veins
and
greisens.
Fluorine
87Sr/86Sr
ratioof 0.725,indicating
its probable
derivationby anatexis
of the LithoniaGneiss(¾Vhitneyis abundantin the area, occurringas fiuorapatitein
andveins.
et al., 1976). A numberof radioactivity
anomaliesthegraniteandasfluoritein thegreisens
description
is givenby Koschmann
are found in the Lithonia Gneiss and related rocks A morecomplete
et al. (1942) andGlasset al. (1958).
(HigginsandZietz,1975).
The northernNorth CarolinaBlue Ridge contains
The Robertson River Formation is a massive,fine-
granitewithvariableamounts
of hornblende
two areasof particularinterest: the Grandfather grained
GR•NITIC U DEPOSITSIN THE EASTERNU.S.
1551
BELTS OF •
,¾•
PRE•IAN
GNEISS
TERRANES
ß 1•
CROSSNORE
PLUTONI
C-•PLCAN
IC
BELT
/
YONAZITE
BELT
• '•
.,
N
]•00-M,Y,-OLD
PLUTONS
(•N
APPALACHIANS)
•'&'•,
SOkFFHEASTERN
PIEZIvoN'r
,,•
,.
,•,j•?..•,
t.1,,, HIGH-C4RADE
BELT
..;3½½.}:;
LIT.tufA
GNEISS
Z•
I•rlITE NT. NAGtqA
SERIES
ß.•
NEWENG•
(•
NEW
ENG•
PE(•'4ATITE
•,•o
•
ALKALINEPROVINCE
DISTRICTS
[qAINE
•O-CU
PROVINCE
i OLIVERIAN
GNEISS
D(lv•S
(N•3R•RN
APPALACHIANS)
•/• • SOUTHERN
AND
CENTRAL
APPALACHIAN
PE(•'4ATI TES
•[As
2-1qAXltl•
I:AVORABILIIZf•
I C.
iNEOUS URANI LI•
A-1
LITI4•NIA GNEISS
•-2
NORT1-ERN
N,C, BLUERIDGE
A-3 CENTRAL
•
NOR•RN VA, BLUERIDGE
TECTONIC DIVISIONS
A-q RALEIGHB•LT
B-1 300-mW,-Ok• PLUTONS
1-Bz BREVARD
ZONE
•r-2 •ITE NT, NAGtqA
SERIES
2 PINE Mr, BELT
•r-J MAIN•MO-CU
PROVINCE
• KIOKEEBELT
SLATEBELT
KINGSMr, B•LT
6 INNERPIEIJIMOI•r
7 BLUERIDC,
E BASF_t'!•NT
8 •FATI•_R
Mr,
9 SALIRATOV•I
Mr, ANTICLIN(IRILI•
lO ca•Lo•
il
BELT
RALEIGHBELT
12 BALTIt'I3RE
GNEISSD(]•!ES
]• PENNSYLVANIA
HIGHLANDSj
READING HILLS
1L•NEWJERSEY•
0
I
200
HLDSON
HIGHI_AI•3S
Km
,
16 BERKSHIRE
HILLSj HOUSATONIC
HIGHLANDS
1• GREEN
MT, MASSIF
18 ADIRONDACK
Mrs,
Fid. 2. Tectonicindex map of the easternUnited Statesshowingareas of maximumfavor-
ability for igneousuraniumdeposits.The sevenspecificareasof principalinterestare shown
by arrowsandare discussed
morecompletely
in the text. Belts of possible
uraniumpotential
investigated
by the writersare shoxvn
by varioussymbols.Major, readilyrecognizable,
tectonic
divisions are shown by numbers.
and biotite(Allen, 1963) and an ageof about700 (Rankin, 1975, 1970); thusit hassortiesinlilaritics
plutons. Its post-tectonic
m.y. Someportions
of thegranitecontainaegerine to nearby Crossnore-type
character
might
1)lace
it
in the Bokan Mountain
and/or riebeckiteand abundantaccessory
fluorite
1552
ROGERS,R.,4GL.4ND,
NœSHIMOR[,GREENBERG,
.4ND H.,4UCK
category,but no informationis availableon Th/U
not particularly abundant in the Conway Granite
(10-15 ppm; Rogers, 1964), but a number of isoThe LovingstonGneissis a quartz-biotiteaugen lated plutons in Vermont belongingto the \Vhite
gneisswidely distributedin the northern Virginia MountainSeriesare more sodic,showminor molybBlue Ridge (Allen, 1963). It is foliated,gradational denuln mineralization, and have radiometric anominto manywall rocks,and clearlysyntectonic.Mona- alies. These smallerbodiesmay be very similar to
and include:
Mt.
Monadnock
zite and allanite are disseminatedin the unit, and Bokan Mountain
radioactivity anomalies are known. Thus, the (Wolff, 1929; Chapman,1954); Mt Ascutney(Daly,
LovingstonGneissmay fit fairly closelywith a 1903; Chapmanand Chapman,1940); Cuttingsville
R6ssing-typemodel.
(Eggleston, 1918; Laurent and Pierson, 1973); and
The Raleigh belt of Xorth Carolinaand Virginia Barber Hill (Laurent and Pierson, 1973).
The molybdenum-copperprovince in Maine has
consistsof high-rank (up to kyanite-grade)gneiss
and schistintruded by severalsyntectonicgranites. formed in the vicinity of a number of granitic to
The plutonshavebeendatedin the rangeof 300 to quartz monzoniticintrusions. Magmatic activity in
450 m.y., and one pluton has an initial 8rSr/søSr the area appearsto have occurredthroughoutmuch
ratioof 0.7141(Fullagar,pers.conminn.),indicating of Ordovicianto Devoniantime (Spoonerand Fairpossibleorigin by anatexis. Pegmatitesare common bairn, 1970). At the Catheart Mountain Mo-Cu
throughoutthe belt. Most of the featuresof R6ssing- deposit,Schmidt (1974) describedan epizonalor
type depositsare present.
subvolcanictype of igneouseraplacement. GreenThe 300-m.y.-oldplutonsof Georgia,South Caro- berget al. (1977) list a numberof high-levelplutons
lina, Xorth Carolina, and Virginia are post-tectonic in Maine that were apparentlyformed in the general
and representthe last major thermal event in the age range and that showmolybdenummineralization
southern Appalachians (Fullagar and Butler, in associatedwith pegmatitesand fluorite. The suiteas
press). There are approximately 20 plutons con- a whole is hard to define, but many of the plutons
sisting of typical calc-alkaline,coarse- to medium- appear to have characteristicssimilar to those of
grained granite intrusive into rock types of all meta- Bokan Mountain.
morphicgrades. Most graniteshave initial s7Sr/SøSr
The variousareasand rock types listed aboveare
ratiosof 0.702 to 0.705 (Fullagar, 1971; Fullagar certainly not the only ones of promisefor uranium
and Butler, in press), but a few plutonshave initial exploration in the eastern United States. The
ratiosgreaterthan 0.710. Molybdenum-copper
min- writers feel,however,that they are wherethe present
eralizationis associated
with four plutons (with low evidenceindicates maxinmm potential for major
initial strontium isotoperatios), and uranium con- discovery.
tentsup to 12 ppm have beenmeasuredin the Sparta
Acknowledgments
Graniteof Georgia(\Vanger, 1972; Garvey,1975).
Work discussedin this paper was supportedby
Different portions of the Sparta pluton, however,
have initial s*Sr/SoSrratios as high as 0.744 (Fulla- contract E(05-1)-1661 from the Energy Research
gar and Butler, in press). The high strohtitaniso- and DevelopmentAdministration(now Department
tope ratios and calc-alkalinecharacter of somebodies of Energy), administered by the Bendix Field
indicatethat theseplutonsdo not fit all aspectsof the EngineeringCorporation,awardedto the University
Bokan Mountain model.
of Xorth Carolinaat ChapelHill. The writers wish
The White Mountain Magma Series is a suite of to thank Dr. Hans Adler (Departmentof Energy.
Mesozoic,post-tectonicring dikes and isolatedplu- Germantown) for initial supportand organizationof
tonsin New England. Rock typesrangefrom gabbro the project. During the course of this work the
to granite; some of the rocks are peralkaline,con- writers have received great assistancefrom many
taining riebeckite, and most rocks are alkali-rich. personson the staffs of the Department of Energy
Initial s•Sr/S%r ratios are low (about 0.706; Foland and Bendix in Grand Junction,Colorado. A number
at the Universityof Xorth Carolinaat
et al., 1971), and the Th/U ratiosare high (Rogers, of colleagues
1964). Ages of the various intrusive complexes Chapel Hill have also contributed valuable ideas and
range from 235 to 100 m.y., and Foland and Faul information. In addition, the writers ;vould like to
(1977) shoxvthat the distributionof ages doesnot thank the following people: R. Alexander, I. E1
supportpreviousproposalsthat the \Vhite Mountain Kassas, E. E1 Shazly, Z. Hassan, R. Jacob, A.
Seriesrepresentsa Mesozoicplume track. The Con- KrSner, C. Reilly, R. Schick,J. yon Backstrbm,and
way Granite is the largestrock bodyin the seriesand P. Woodhouse.
has been proposedas a low-grade thorium resource
]-)EP.\RTMENT OF •EOLOGY
or Sr isotopic ratios.
on the basis of its average concentrationof about
50 ppm thorium (Adams et al., 1962). Uranium is
UNIVERSITY OF NORTH CAROLINA AT CHAPEL
CHAPELHILL, NORTH CAROLINA27514
GI2,4NIT[C
U DEPOSITS
R. 14. N. ^N•, S. ,.'\. l[. ['•r.s•.;N'r ,\DI)IiESN:
UNION CARBIDE METALS DIVISION
GRANDJUNCTION,COLORADO
81501
July 25, 1978
REFERENCES
IN
THE
E,4STERN
U.S.
1553
('l•urkiu, Michael, Jr., mid El,{'rlchb (L I)., 1977, Al•cic•d
borderland
tcrranes of the North
American
Cordillera--
Correlation and microplate tectonics: Geol. Soc. America
Bull., v. 88, p. 769-786.
Clifford, T. N., 1967, The Damaran episode in the upper
Proterozoic-lowerPaleozoicstructural history of southern
Africa: Geol. Soc. America Spec. Paper 92, 100 p.
Cunningham-Dunlop,P. K., 1967, Geology of economicuraniferous pegmatitesin the Bancroft area, Ontario: Unpub.
Ph.D. dissertation,Princeton Univ., 160 p. (University
Hampshire as a major low-grade thorium resource: Natl.
Microfilms •68-8915).
Acad. Sci. Proc., v. 48, p. 1898-1905.
Daly, R. A., 1903,The geologyof AscutneyMountain, VerAllen, J. N., 1971, The genesisof Precambrianuranium demont: U.S. Geol. Survey Bull. 209, 122 p.
posits in eastern Canada, and the urauiferouspegmatites Damon, P. E., 1968, Behavior of some elements during
of Mont Laurier, Quebec: Unpub. M.Sc. thesis,Queen's
magmatic crystallization: Geochim.et Cosmochim.Acta,
Univ., Kingston, Ontario.
v. 32, p. 564-567.
Allen, R. M., Jr., 1963, Geology of Greene and Madison Dennison,J. M., and Wheeler, W. H., 1975,Stratigraphy of
Counties:Virginia Div. Mineral Resources
Bull. 78, 102 p.
PrecambrianthroughCretaceousstrata of probablefluvial
Armstrong, F. C., 1974, Uranium resourcesof the future-origin in southeastern
United Statesand their potentialas
"porphyry"uranium deposits,in Formationof uraniumore
uranium host rocks: SoutheasternGeology,Spec. Pub. 5,
deposits: Vienna, Internat. Atomic Energy Agency, p.
210
p.
625-635.
R. G., Needham,R. S., Wilkes, P. G., Page, R. W.,
Ayers, D. E., and Eadington,P. J., 1975, Uranium min- Dodson,
Smart, P. G., and Watchman, A. L., 1974, Uranium mineralization in the South Alligator River valley: Mineralization in the Rum Jungle-Alligator River province,
eralium Deposita, v. 10, p. 27-41.
Northern Territory, Australia, in Formation of uranium
Bald•vin, A. B., 1970, Uranium and thoriron occurrenceson
ore deposits:Vienna, Internat. Atomic Energy Agency,p.
the north shore of the Gulf of St. Lawrence:
Canadian
551-567.
Mining Metall. Bull., v. 63, p. 699-707.
Eade,
K. E., and Fahrig, W. F., 1971,Chemicalevolutionary
Beavan, A. P., 1958, The Labrador uranium area: Geol.
trends of continentalplates--a preliminary study of the
Assoc. Canada Proc., v. 10, p. 137-145.
Canadianshield: CanadaGeol. Survey Bull. 179, 51 p.
Beck, L. S., 1970, Genesis of uranium in the Athabasca Eggleston, J. W., 1918, Eruptive rocks at Cuttingsville,
region and its significancein exploration: Canadian Inst.
Vermont: Am. Jour. Sci., v. 45 (4th series), p. 377-410.
Mining Metallurgy Trans., v. 73, p. 59-69.
Fayall, J. C., 1973, Mineralizacao uranifera na area do geoBerning, J., Cook, R., Hiemstra, S. A., and Hoffman, U.,
synclinedo Serido: CongresoBrasileiro do Geologico,v.
1976, The RiSssinguranium deposit, South West Africa:
1, no. 1, p. 48-49.
Ecox. G•oL., v. 71, p. 351-368.
Foland, K. A., and Faul, Henry, 1977, Ages of the White
Billings, M.P., and Keevil, N. B., 1946, Petrography and
Mountain intrusives--New Hampshire, Vermont, and
radioactivity of four Paleozoic magma series in New
Maine, U.S.A.: Am. Jour. Sci., v. 277, p. 888-904.
Hampshire: Geol. Soc. America Bull., v. 57, p. 797-828.
Foland, K. A., Quinn, A. W., and Giletti, B. J., 1971, K-Ar
Bohse, H., Rose-Hansen, J., Sorenson, H., Steenfelt, A.,
and Rb-Sr Jurassic and Cretaceousages for intrusives of
Lovborg, L., and Kunzendorf, H., 1974, On the behavior of
the White Mountain magma series,northern New England:
uranium during crystallization of magmas--with special
Am. Jour. Sci., v. 270, p. 321-330.
emphasis on alkaline magmas, in Formation of uranium
Fullagar, P. D., 1971, Age and origin of plutohie intrusions
ore deposits: Vienna, Internat. Atmnic Energy Agency, p.
in the Piedmont of the southeastern Appalachians: Geol.
Adams, J. A. S., Kline, M.-C., Richardson,K. A., and
Rogers, J. J. W., 1962, The Conway Granite of New
49-60.
Soc. America Bull., v. 82, p. 2845-2862.
Bowden, P., and Turner, D.C., 1974, Peralkaline and asFullagar, P. D., and Butler, J. R. (in press), 325- to 265sociated ring-dike complexes in the Nigeria-Niger provm.y.-old granitic plutons in the Piedmont of the southeastince, West Africa, in Sorenson,H., ed., The alkaline rocks:
ern Appalachians: Am. Jour. Sci.
New York, John Wiley, p. 330-351.
Gandhi, S.S., Grasty, R. L., and Grieve, R. A. F., 1969,
Brooks, J. M., 1960, The uranium depositsof northwestern
The geology and geochronologyof the Makkovik Bay area,
Queensland: QueenslandGeol. Survey, Pub. 297, 48 p.
Labrador: Canadian Jour. Earth Sci., v. 6, p. 1019-1035.
Bryant, Bruce, and Reed, J. C., Jr., 1970, Geology of the Garvey, M. J., 1975, Uranium, thorium, and potassium
Grandfather Mountain window and vicinity, North Caroabundancesin rocks of the Piedmont of Georgia: Unpub.
lina and Tennessee: U.S. Geol. Survey Prof. Paper 615,
Master's thesis, Univ. Florida, Gainesville, 95 p.
190 p.
Gerasimovsky, hr. I., Volkov, V. P., Kogarko, L. N.,
Butler, J. R., 1972, Age of Paleozoic regional metamorphism
Polyakov, A. I., Saprykina, T. V., and Balashov, Y. A.,
in the Carolinas, Georgia, and Tennessee,southern Ap1968, The geochemistry of the Lovozero alkaline massif:
palachians: Am. Jour. Sci., v. 272, p. 319-333.
Canberra, Australian Natl. Univ. Press, 395 p. (English
Campana, Bruno, 1956, Granite, orogenies, and mineral
translation by D. A. Brown).
genesis in the Olary province (South Australia): Geol. Glass, J. J., Koschmann, A. H., and Vhay, J. S., 1958, MinSoc. Australia Jour., v. 4, p. 1-12.
erals of the cassiterite-bearingveins at Irish Creek, VirCampana, Bruno, and King, D., 1958, Regional geology and
ginia, and their parageneticrelations: EcoN. GEOL.,v. 53,
mineral resourcesof the Olary province: South Australia
p. 65-84.
Geol. Survey Bull. 34, p. 1-91.
Greenberg, J. K., Hauck, S. A., Ragland, P. C., and Rogers,
Carter, E. K., Brooks, J. H., and Walker, K. R., 1961, The
J. J. W., 1977, A tectonic atlas of uranium potential in
Precambrian mineral belt of northwestern Queensland:
crystalline rocks of the eastern U.S.:
Grand Junction,
Australian Bur. Mineral Resources,Geology Geophysics
U.S. Dept. Energy, Open-File Rept. GJBX-69(77), 94 p.
Bull. 51, p. 228-234.
Chapman, R. W., 1954, Criteria for the mode of emplacement Hawkins, B. W., 1975, Mary Kathleen uranium deposit, i•
Knight, C. L., ed., Economic geology of Australia and
of the alkaline stockat Mount Monadhock,Vermont: Geol.
Papua New Guinea. 1. Metals: Victoria, Australasian
Soc. America Bull., v. 65, p. 97-114.
Inst. Mining Metallurgy, p. 398-402.
Chapman, R. W., and Chapman, C. A., 1940, Cauldron subsidence at Ascutney Mountain, Vermont:
Geol. Soc. Higgins, M. W., and Zietz, Isidore, 1975, Geologic interpretation of aeromagnetic and aeroradioactivity maps of
America Bull., v. 51, p. 191-212.
northern Georgia: U.S. Geol. Survey Map 1-783.
Church, S. E., and Tatsumoto, Mitsunobu, 1975, Lead isotope relations in oceanic ridge basalts from the Juan de Holland, H. D., 1972, Granites, solutions,and base metal deposits: EcoN. GzoL., v. 67, p. 281-301.
Fuca-Gorda Ridge area, N. E. Pacific Ocean: Contr.
Mineralogy Petrology, v. 53, p. 253-279.
Hughes, F. E., and Munro, D. L., 1965, Uranium ore deposit
1554
ROGERS',
R/iGLzIND,NISHI3i'ORl',GREENBERG,
•IND [[dUCK'
at Mary Kathleen, in McAndrew, j., ed., Geology of
Australian ore deposits,2rid ed., v. 1: Commonwealth
Mining Metall. Cong., 8th, Melbourne,p. 256-263.
Hurley, P.M.,
1956, Direct radiometricmeasurement
by
gamma ray scintillation spectrometer; Part II, uranium,
thorium, and potassium in common rocks: Geol. Soc.
America Bull., v. 67, p. 405-411.
Hussein,H. A., and El Kassas,I. A., 1970,Occurrenceof
someprimary uraniummineralizationat El Atshan locality,
central Eastern Desert: United Arab Republic (Egypt)
Jour. Geology,v. 14, p. 97-110.
Hussein,H. A., Faris, M. I., and Assaf, I4. S., 1970,Some
radiometric investigations at Wadi Kariem-Wadi Dabbah
area, Eastern Desert: United Arab Republic (Egypt)
Jour. Geology,v. 14, p. 13-21.
I. A. E. A., 1970, Uranium explorationgeology: Vienna,
Internat. Atomic Energy Agency, 384 p.
1974, Formation of uranium ore deposits: Vienna,
Internat. Atomic Energy Agency, 748 p.
- 1977, Recognition and evaluation of uraniferous areas'
Vienna, Internat. Atomic Energy Agency,295 p.
Jacob,R. E., 1974, Geologyand metamorphicpetrologyof
part of the Damara orogen along the Lo•ver Swakop
River, South West Africa: Cape Town, ChamberMines,
PrecambrianResearchUnit Bull. 17, 184 p.
Jacob, R. E., and Hambleton-Jones,B. B., 1977, Geological
Albite-riebeckitegranites of Nigeria: London, Dept. $ci.
Indus. Research,Geol. Survey and Museum Rept., GSM/
AED 95, 25 p.
Miller, T. P., 1972, Potassium-rich alkaline intrusive rocks
of western Alaska: Geol. Soc. America Bull., v. 83, p.
2111-2128.
Miller, T. P., and Bunker, C. M., 1976, A reconnaissance
studyof the uraniumand thorium contentsof plutonicrocks
of the southeasternSeward Peninsula, Alaska: U.S. Geol.
Survey Jour. Research,v. 4, p. 367-377.
Moreau, Marcel, 1977, L'uranium et les granitoides--essai
d'interpretation,in Jones,M. J., ed., Geology,mining, and
extractive processingof uranium: London, Inst. Mining
Metallurgy, p. 83-102.
Nash, J. T., 1977, Geology of Midnite mine uranium area,
Washington--maps,description,and interpretation: U.S.
Geol. Survey Open-File Rept. 77-592, 39 p.
Xash, J. T., and Lehrman, N.J., 1975, Geologyof the Midnite uranium mine, Stevens County, Washington: U.S.
Geol. Survey Open-File Rept. 75-402, 36 p.
Nishimori, R. K., Ragland, P. C., Rogers, J. J. W., and
Greenberg,J. K., 1977,Uranium depositsin granitic rocks:
U.S.
Energy Research Devel. Adm., Open-File Rept.
GJBX-13(77), 311 p.
Odom, A. L., and Fullagar, P. D., 1971, A major discordancy
between U~Pb zircon ages and Rb-Sr whole-rock ages of
Late Precambrianrocksin the Blue Ridge province [abs.]:
Geol. Soc. America Abstracts with Programs, v. 3, p. 663.
Phair, George, and Gottfried, David, 1964, The Colorado
Front Range as a uranium and thorium province,in Adams,
J. A. S., and Lowder, W. E., eds., The natural radiation
environment: Houston, Rice Univ., p. 7-38.
Pbair, George, and Jenkins, L. B., 1975, Tabulation of
and geochemical setting of granites in the eugeosynclinal
portion of the Damara orogen, R6ssing area, South West
Africa [abs.]: Geol. Soc. America Abstracts with Programs, v. 9, p. 1035.
Jahns, R. H., and Burnham, C. W., 1969, Experimental
studiesof pegmatite genesis; 1, A model for the derivation
and crystallization of granite pegmatites: Ecox. GEOL.,
uranium and thorium data on Mesozoic-Cenozoic intrusive
V. 64, p. 843-864.
Johnson, W., 1958, Geological environments of some radiorocks of known chemical compositionin central Colorado:
active mineral depositsin South Australia: Sydney, AusU.S. Geol. Survey Open-File Rept. 75-501, 57 p.
tralian Atomic Energy Symposium, Sect. I, Geology, p. Philpotts, A. R., 1976, Silicate liquid immiscibility; its prob35-41.
able extent and petrogeneticsignificance: Am. Jour. Sci.,
v. 276, p. 1147-1177.
Jones, M. J., ed., 1977, Geology, mining, and extractive
processingof uranium: I.ondon, Inst. Mining Metallurgy, Ra.mos,
J. R. de Andrade,and Fraenkel,M. O., 1974,Ura171 p.
mum occurrences in Brazil, in Formation of uranium ore
Kish, L., 1975, Radioactive occurrencesin the Grenville of
deposits: Vienna, Internat. Atomic Energy Agency, p.
637-658.
Quebec, Mont Laurier-Cabonga district: Quebec Dept.
Nat. Resources,Mineral Deposits Service, DP-310, 30 p.
Rankin, D. W., 1970, The Blue Ridge and the Reading
Koschmann, A. 14., Glass, J. J., and Vhay, J. S., 1942, Tin
Prong; stratigraphy and structure of Precambrian rocks
depositsof Irish Creek, Virginia: U.S. Geol. Survey Bull.
in northwestern North Carolina, in Fisher, G. W., et al.,
936-K, p. 271-296.
eds., Studiesof Appalachian geology; central and southern:
Kr;Sner, Alfred, and Hawkesworth, C. J., 1977, Late PreNew York, Interscience,p. 227-245.
cambrian eraplacement ages for R;Sssingalaskitic granite
---- 1975,The continentalmargin of easternNorth America
(Damara belt) in Namibia and their significance for the
in the southern Appalachians; the opening and closing of
timing of metamorphic events: 20th Ann. Rept., Research
the proto-Atlantic Ocean: Am. Jour. Sci., v. 275-A, p.
298-336.
Inst. African Geology, Leeds Univ., p. 14-17.
Lang, A. H., Griffith, J. W., and Steacy, H. R., 1962, -1976, Appalachian salients and recesses;Late PrecamCanadian depositsof uranium and thorium: Canada Geol.
brian continental breakup and the opening of the Iapetus
Survey, Econ. Geology Ser., no. 16 (2nd ed.), 324 p.
Ocean: Jour. Geophys. Research, v. 81, p. 5605-5619.
Laurent, R., and Pierson, T. C., 1973, Petrology of alkaline Rayher, E. O., 1960, The nature and distribution of uranium
rocks from Cuttingsville and Shelburne Peninsula, Verdeposits in New South Wales: New South Wales Dept.
mont: Canadian Jour. Earth Sci., v. 10, p. 1244-1256.
Mines, Tech. Rept., v. 5, p. 63-101.
I.uth, W. C., and Tuttle, O. F., 1968, The hydrous vapor
Rich, R. A., Holland, H. D., and Petersen,U., 1977,Hydrophase in equilibrium with granite and granite magmas, in
thermal uranium deposits: Amsterdam, Elsevier, 264 p.
Larsen, L. H., Prinz, M., and Manson, V., eds., Igneous Robertson, D. S., 1974, Basal Proterozoic units as fossil
and metamorphic geology: Geol. Soc. America Mere. 115,
time markers and their use in uranium production, in
p. 513-547.
Formation of uranium ore deposits: Vienna, Internat.
Maciel, A. C., and Cruz, P. R., 1973, Perill analitico do
Atomic Energy Agency, p. 495-511.
uramo: Rio de Janeiro, Minist. Minas Energia, Dept.
Robertson, D. S., and Tilsley, J. E., 1977, The time-bound
Nacional Producao Mineral, Bol. 27, 70 p.
character of uranium deposits [abs.]: Geol. Soc. America
MacKevett, E. A., 1963, Geology and ore deposits of the
Abstracts with Programs, v. 9, p. 1143.
Bokan Mountain uranium-thorium area, southeastern Robinson, S.C., 1960, Economic uranium depositsin granitic
Alaska: U.S. Geol. Survey Bull. 1154, 125 p.
dikes, Bancroft district, Ontario: Canadian Mineralogist,
Malan, R. C., 1972, Summary report--Distribution of urav. 6, p. 513-521.
nium and thorium in the Precambrian
of the western United
Rogers, J. J. W., 1964, Statistical tests of the homogeneityof
States: U.S. Atomic Energy Comm. Rept. AEC-RD-12,
the radioactive components of granitic rocks, in Adams,
59 p.
J. A. S., and Lowder, W. E., eds., The natural radiation
Mawdsley, J. B., 1952, Uraninite-bearing deposits,Charlebois
environment: Houston, Rice Univ., p. 51-62.
Lake area, northern Saskatchewan: Canadian Mining
Rogers, J. J. W., and Adams, J. A. S., 1969a, Thorium, in
Metall. Bull., v. 45, p. 366-375.
Wedepohl, K. H., ed., Handbook of geochemistry, Part
McKay, R. A., Beer, K. E., and Rockingham, J. B., 1952,
II/I: Berlin, Springer Verlag, Chap. 90, 39 p.
,
GR•INITIC
U DEPOSITS
1969b,Uranium, in Wedepohl, K. H., ed., Handbook of
geochemistry,Part II/I:
Berlin, Springer Verlag, Chap.
92, 50 p.
Rogers, J. J. W., and McKay, S. M., 1972, Chemical evolution of geosynclinalmaterial, in Doe, B. R., and Smith,
D. K., eds., Studies in mineralogy and Precambrian
geology: Geol. Soc. America Mem. 135, p. 3-28.
IN THE E•ISTERN
---
Rogers, J. J. W., Adams, J. A. S., and Gatlin, Beverly,
1965,Distribution of thorium, uranium,and potassiumconcentrationsin three coresfrom the Conway Granite, New
Hampshire,U.S. A.: Am. Jour. Sci., v. 263, p. 817-822.
Rogers, J. J. W., Ghuma, M. A., Nagy, R. M., Greenberg,
J. K., and Fullagar, P. D., 1978,Plutonism in Pan-African
belts and the geologic evolution of northeastern Africa:
Earth Planet. Sci. Letters,v. 39, p. 109-117.
Rowe, R. B., 1958, Niobium (columbium) deposits of
Canada: Canada Geol. Survey, Econ. Geology Ser., No.
18, 108 p.
Ruzicka, V., 1977, Conceptualmodelsfor uranium deposits
and areas favourable for uranium mineralization in Canada:
Canada Geol. Survey Paper 77-1A, p. 17-25.
Satterly, J. 1957, Radioactive mineral occurrences in the
Bancroft area: Ontario Dept. Mines Ann. Rept., v. 65,
181 p.
Scblnidt, R. G., 1974, Preliminary study of rock alteration in
the Catheart Mountain Mo-Cu deposit, Maine: U.S.
Geol. Survey Jour. Research, v. 2, p. 189-194.
Sharp,B.. J., and Heftand,D. L., 1954,Preliminaryreport
on uranmm occurrencein the Austin area, Lander County,
Nevada: U.S. Atomic Energy Comm. Rept. RME-2010,
16 p.
Sobrinho, E.G.,
1974, Prospecao do uranio na chamine
alcalina do Tapira-Minas Gerais: Rio de Janeiro, Minist.
Minas Energia, ComissaoNacional Energia Nuclear, Bol.
10, 16 p.
Sorenson,H., 1970, Occurrenceof uranium in alkaline igneous rocks,i• Uranium explorationgeology:Vienna, Internat. Atomic Energy Agency, p. 161-168.
U.S.
1555
1977 NURE Geology Uranium Symposium,Sedimentary
Host Rock Sess., p. 64-77.
Tatsumoto, Mitsunobu, 1966, Genetic relations of oceanic
basaltsas indicated by lead isotopes: Science,v. 153, p.
1094-1101.
•
1969, Lead isotopesin volcanic rocks and possibleoceanfloor underthrusting beneath island arcs: Earth Planet.
Sci. Letters, v. 6, p. 369-376.
Thompson, B. P., 1965, Geological mineralogy of South
Australia, in McAndrew, J., ed., Geology of Australian ore
deposits,2nd ed., v. 1: CommonwealthMining Metallurgy
Cong., 8th, Melbourne, p. 270-284.
Tuttle, O. F., and Bowen, N. L., 1958, Origin of granite in
light of experimental studies on the system NaAISiaOsKA1Si:•O•-SiO•-H_oO: Geol. Soc. America Mem. 74, 153 p.
Verwoerd, W. J., 1967, The carbonatitesof South Africa and
South West Africa--a nuclear raw material investigation
primarily for the Atomic Energy Board: Pretoria, South
Africa Geol. Survey, Handbook 6, 452 p.
yon BackstrSm, J. \V., 1974, Other uranium deposits, in
Formation of uranium ore deposits: Vienna, Internat.
Atomic Energy Agency, p. 605-624.
Wanger, J.P., 1972, Relationships among uranium, thorium,
and other elements in igneous rock series from the Carolina Piedmont: Unpub. Master's thesis, Univ. North
Carolina at Chapel Hill, 64 p.
Wells, J. D., 1960, Petrography of radioactive Tertiary igneous rocks, Front Range mineral belt, Colorado: U.S. Geol.
Survey Bull. 1032-E, p. 223-272.
Wenner, D. B., Whitney, J. A., and Stormer, J. C., Jr.,
1978, Oxygen isotope studies of post-metamorphicgranitic
plutons from the piedmont province of Georgia [abs.]:
Geol. Soc. America Abstracts with Programs, v. 10, p. 201.
\¾hitney, J. A., 1975, Vapor generation in a quartz monzonite
magma; A synthetic model with application to porphyry
copper deposits: Ecox. GF•o•.,v. 70, p. 346-358.
Whitney, J. A., Jones, L. M., and Walker, R. L., 1976, Age
and origin of the Stone Mountain granite, Lithonia district, Georgia: Geol. Soc. America Bull., v. 87, p. 1067-
Spooner, C. M., and Fairbairn, H. W., 1970, Relation of
1077.
radiometric age of granitic rocks near Calais, Maine, to \Villis, J. L., and Stevens, B. P. J., 1971, The mineral industhe time of the Acadian orogeny: Geol. Soc.America Bull.,
try of Nexv South Wales--uranium: New South Wales
v. 81, p. 3663-3670.
Geol. Survey Pub. 43, 58 p.
Staatz, M. H., and Miller, T. P., 1976, Uranium and thorium Wolff, J. E., 1929, Mount Monadhock, Vermont--a syenite
content of radioactive phasesof the Zane Hills pluton:
hill: Jour. Geology, v. 37, p. 1-15.
1,5.S. Geol. Survey Circ. 733, p. 39-41.
Youlag, E. J., and Hauff, P. L., 1975, An occurrenceof disStuckless,J. J., 1977, A synthesisof uranium-related studies
seminated uraninite in V•heeler Basin, Grand County,
in the Precambrian rocks of the Granite Mountains,
Colorado: U.S. Geol. Survey Jour. Research, v. 3, p.
305-311.
•Vyoming: Grand Junction, Bendix Field Eng. Corp.,