Rare Earth Elements (REE)

44 Pages·2017·5.23 MB·English

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Article
Rare Earth Elements (REE) Deposits Associated with
Great Plain Margin Deposits (Alkaline-Related),
Southwestern United States and Eastern Mexico
VirginiaT.McLemore ID
NewMexicoBureauofGeologyandMineralResources,NewMexicoInstituteofMiningandTechnology,
Socorro,NM87801,USA;[email protected];Tel.:[phone]
Received:13November2017;Accepted:18January2018;Published:23January2018
Abstract: W.G. Lindgren in 1933 first noted that a belt of alkaline-igneous rocks extends along
the eastern edge of the Rocky Mountains and Basin and Range provinces from Alaska and
British Columbia southward into New Mexico, Trans-Pecos Texas, and eastern Mexico and that
these rocks contain relatively large quantities of important commodities such as, gold, fluorine,
zirconium,rareearthelements(REE),tellurium,gallium,andothercriticalelements. InNewMexico,
these deposits were called Great Plain Margin (GPM) deposits, because this north-south belt of
alkaline-igneousrocksroughlycoincideswithcrustalthickeningalongthemarginbetweentheGreat
PlainsphysiographicprovincewiththeBasinandRange(includingtheRioGranderift)andRocky
Mountains physiographic provinces, which extends into Trans-Pecos Texas and eastern Mexico.
Since1996,onlyminorexplorationanddevelopmentofthesedepositsinNewMexico,Texas,and
easternMexicohasoccurredbecauseoflowcommodityprices,permittingissues,andenvironmental
concerns. However,asthecurrentdemandforgoldandcriticalelements,suchasREEandtellurium
hasincreased,newexplorationprogramshaveencouragedadditionalresearchonthegeologyof
these deposits. The lack of abundant quartz in these systems results in these deposits being less
resistanttoerosion,beingcovered,andnotaswellexposedasothertypesofquartz-richdeposits,
thereforeadditionalundiscoveredalkaline-relatedgoldandREEdepositsarelikelyintheseareas.
DepositsofTh-REE-fluorite(±U,Nb)epithermalveinsandbrecciasarefoundintheseveralGPM
districts, but typically do not contain significant gold, although trace amounts of gold are found
inmostGPMdistricts. Gold-richdepositsinthesedistrictstendtohavemoderatetolowREEand
anomalously high tungsten and sporadic amounts of tellurium. Carbonatites are only found in
New Mexico and Mexico. The diversity of igneous rocks, including alkaline-igneous rocks, and
associatedmineraldepositsalongthisboundarysuggeststhatthisregionischaracterizedbyhighly
fractionatedanddifferentiated,multiplepulsesofmantle-derivedmagmasevolvingtolowercrustal
magmasrelatedtothesubductionoftheFarallonplate.Thedifferencesinincompatibletraceelements,
includingREEandberyllium,betweenthedifferentgranitictorhyoliterocksarelikelyrelatedtoeither
differencesinthecrustalrocksthatwereassimilatedduringmagmaticdifferentiationorbypotential
minorcontaminationfromcrustalsourcesand/ormagmamixing. Deep-seatedfracturesystems
orcrustallineamentsapparentlychanneledthemagmasandhydrothermalfluids. Oncemagmas
andmetal-richfluidsreachedshallowlevels,thedistributionandstyleoftheseintrusions,aswellas
theresultingassociatedmineraldepositswerecontrolledbylocalstructuresandassociatedigneous
rockcompositions.
Keywords: gold;REE;alkaline-igneousrelateddeposits;alkaline-igneousrocks;carbonatites
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1. Introduction
Lindgren[1]firstnotedthatabeltofalkaline-igneousrocksextendsalongtheeasternedgeof
theRockyMountainsandBasinandRangeprovincesfromAlaskaandBritishColumbiasouthward
intoNewMexico,Trans-PecosTexas,andeasternMexico. Theserocksareassociatedwithrelatively
largequantitiesofgold,fluorine,zirconium,rareearthelements(REE),tellurium,gallium,andother
critical elements [2–5] and over the years, many commodities, especially gold and molybdenum,
have been produced from the North American Cordilleran alkaline-igneous belt. Deposits within
this belt that have produced significant amounts of gold in the United States and Canada include
Cripple Creek, Colorado (731 metric tons of gold production) [5], Black Hills, South Dakota (235
metrictonsgoldproduction)andLandsky-Zortman,Montana(71metrictonsgoldand586metric
tonssilverproduction)[6]. AlthoughtherehasbeenlittleREEproductionfromthesedepositsinthe
past, explorationisoccurringandsomecouldbeproductiveinthefuture, suchastheBearLodge
MountainscarbonatitedepositinWyoming,wheremorethan16.3millionmetrictonsof3.05%total
REEarereported[7,8].
Rareearthelements(REE)andothercriticalelementsareincreasinglybecomingmoreimportant
inourtechnologicalsociety,andbecauseofthechemicalandphysicalpropertiesofREE,theyareused
inmanydiversedefense,energy,industrial,andmilitaryapplications,likecellphones,computers,
magnets,batteries,solarpanels,andwindturbines[7–12]. REEincludethe15lanthanideelements
(atomicnumber57to71),yttrium(Y,atomicnumber39),andscandium(Sc,atomicnumber21;Table1)
andarecommonlydividedintotwochemicalgroups,thelightREE(LathroughEu)andtheheavy
REE(GdthroughLuandY).REEarelithophileelements(orelementsenrichedinthecrust)thathave
similarphysicalandchemicalproperties,and,therefore,occurtogetherinnature. ThenameREEis
misleading;thecontentoftheREEintheearth’scrustrangesfrom60ppmforCeto~0.5ppmforTb
andLu,whichisgreaterthanthecrustalabundanceofsilver(Ag). FourREE(Y,La,CeandNd)have
largercrustalabundancesthanlead(Pb)[8,9]. However,REEarenotalwaysconcentratedineasily
minedeconomicdepositsandonlyafewdepositsintheworldaccountforcurrentproduction[8–14].
TheU.S.onceproducedenoughREEforU.S.consumption,butsince1999morethan95%to100%of
theREErequiredbyU.S.industrieshavebeenimportedfromChina[9,14–16]. However,theprojected
increaseindemandforREEinChina,India,UnitedStates,andothercountries[8,9,12]couldresultin
increasedexplorationandultimateproductionfromfuturedepositsintheU.S.andelsewhere[16].
REEdepositshavebeenreportedandproducedfromNewMexico[17–19],butwerenotconsidered
importantexplorationtargetsbecausethedemandinpastyearshasbeenmetbyotherdepositsin
theworld. Alsotherearepotentialpermittingandenvironmentalissuesthathamperexplorationand
developmentintheU.S.However,withtheprojectedincreaseindemandandpotentialuncertaintyof
availableproductionfromtheChinesedeposits,theseareasinNewMexico,Texas,andeasternMexico
shouldbere-examinedfortheirREEpotential.
TheNorthAmericanCordilleranalkaline-igneousbeltisanorth-southbeltofalkaline-igneous
rocksandcrustalthickening,roughlycoincidingwiththeGreatPlainsphysiographicmarginwiththe
RockyMountainsandtheBasinandRange(includingtheRioGranderift)physiographicprovinces
(Figure 1) [2,3,20–26]. Chapin et al. [27] referred to this zone as the Rocky Mountain front. Other
namesincludetheEasternAlkalicBelt[28]andtheRockyMountainGoldProvince. InNewMexico,
themineraldepositsfoundintheNorthAmericanCordilleranalkaline-igneousbeltareassociated
with Eocene-Oligocene alkaline to calc-alkaline rocks that were called Great Plain Margin (GPM)
deposits[23,24,29–32]. Thistermisretainedinthispaperandextendedtoincludesimilardepositsin
Trans-PecosTexasandeasternMexico.
In New Mexico, the GPM portion of the North American Cordilleran alkaline-igneous belt
extendsnearRaton,southwardtotheTrans-Pecosalkalinebelt(Figure2). TheGPMbeltcontinuesinto
Trans-PecosTexasandnortheasternMexico. TheGPMdepositsinNewMexico,Texas,andMexicoare
eastoftheRioGranderift,alongtheborderwiththeGreatPlains.
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Manyauthorshaveuseddifferentclassificationschemesindescribingthemineraldepositsfound
intheNorthAmericanCordilleranalkaline-igneousbelt. Alternativeclassificationsofthesemineral
depositsbyotherworkersincludeAu-Ag-Teveins[33–36],alkalic-goldoralkaline-igneousrelated
golddeposits[2,3,20–22,25,37–39],andporphyrygolddeposits[39,40]. REEalsoareassociatedwith
peralkalineintrusion-relatedigneoussystemsandsomearefoundintheNorthAmericanCordilleran
alkaline-igneous belt, but not in New Mexico ([8,39,41], this report). The U.S. Geological Survey
mineraldepositclassificationsystemisusedinthisstudywithminormodifications[8,32,34,39].
ThereareninetypesofdepositsfoundinGPMdistrictsinNewMexico,Texas,andMexico(revised
from[19,23,24,32]):(1)polymetallic,epithermaltomesothermalveins(USGSmodelno.17,22b,22c[33,39]),
(2)brecciapipes(USGSmodelno. 10b,11d[32,33,39]),(3)porphyrycopper-molybdenum-gold(USGS
modelno. 20c,21a,16[32,39,40]),(4)copper,lead-zinc,and/orgoldskarnsand/orcarbonate-hosted
replacementdeposits(USGSmodelno. 18b,18c,19a[32,39]),(5)ironskarnsandreplacementbodies
(USGSmodelno.18d[32,39]),(6)Th-REE-fluorite(±U,Nb)epithermalveinsandbreccias(USGSmodel
no. 10b,11d[32,39]),(7)carbonatites(USGSmodelno. 10[8,32,39]),(8)peralkalineintrusion-related
REEdeposits(USGSmodelno. 11[8,39,41])and(9)placergold(USGSmodelno. 39a[32,39])(Table1).
Additionaltypesofdepositsarelocallyfoundspatially(andperhapsgenetically)inthevicinityofGPM
deposits:fluorsparveinandbrecciadeposits(USGSmodelno.26b[39]),tungsten-bearingveins(USGS
modelno. 15a[39]),andvolcanogenicberylliumdeposits[42]. Mostofthesedepositsareproximal
magmaticdeposits,whereasironskarnsandreplacementbodiesaremoredistalmagmaticdeposits.
Placergolddepositshavebeenweatheredfromtheiroriginalsourceandhaveeitheraccumulatedin
placeorbeentransported,generallybywater.
Alkaline-tosub-alkaline-igneousrocksarefoundinallGPMdistricts,butgoldmineralizationis
locallyassociatedwitholder,moresilica-saturated(monzonite)oroversaturated(quartzmonzonite)
rocks[21,24,43–46].Alkaline-igneousrocksareenrichedinsodiumandpotassium(Na O,K O)relative
2 2
to similar rocks at given silica (SiO ) content. Most GPM deposits are associated with Oligocene
2
intrusiverocks,38–23Ma(Figure2;Table1),exceptforthedepositsintheJicarillaMountainsand
Orograndedistricts,whichareassociatedwithEoceneintrusiverocks(39.45–45.6Ma)(Table1;[45]).
Thelarger,moreproductivegolddepositsarefoundinnorthernandcentralNewMexico(Figure2;
Table1). Carbonatites,whicharetheworld’slargesteconomicsourceofREEtoday[8],arefoundonly
atLaughlinPeak(ChicoHills,ColfaxCounty)[44]andineasternMexico[47],butaresuspectedto
occuratdepthintheGallinasMountains(Table1).
Since1996,onlyminorexplorationanddevelopmentoftheseREEdepositshasoccurredbecause
oflowcommodityprices,permittingissues,andenvironmentalconcerns. However,oneimportant
changeisthatnowthereisanincreaseddemandforcriticalelementslikeREE,tellurium,niobium,and
otherelementsthatarefoundintheNorthAmericanCordilleranalkaline-igneousbelt,includingNew
Mexico’sGPMdistricts[8,10,48].Inaddition,newgeochemicalandgeochronologicaldataareavailable
inmanyGPMdistrictsinNewMexico,Texas,andeasternMexico. ManyGPMdistrictsinNewMexico
havebeenmappedorre-mappedaspartoftheNewMexicoBureauofGeologyandMineralResources
(NMBGMR) geologic mapping program, including the Ortiz porphyry belt, Santa Fe County and
thesouthernLincolnCountyporphyrybelt(Table1;http://geoinfo.nmt.edu/publications/maps/
geologic/ofgm/home.cfml,accessed21January,2018). Thisnewmapping,alongwithgeochemical
andgeochronologicalstudies,haverevisedthevolcanicstratigraphyandenhancedourknowledgeof
thetimingofmagmaticevents,mineralogyandgeochemistry,andgeologicprocessesformingGPM
depositsinNewMexico. NewresearchattheRoundTopMountaindepositatSierraBlanca,Texas
andnewlydiscoveredcarbonatitesinMexicoalsohaveincreasedourareaofeconomicinterestto
thesouthtoincludeTrans-PecosTexasandeasternMexico. Thus,thepurposesofthispaperareto
(1)summarizethegeology,geochemistry,geochronologyandmineralproductionofEocene-Oligocene
alkaline-igneousrelatedGPMmineraldepositsinNewMexico,Texas,andeasternMexico,(2)discuss
theageandformationofthesedeposits,and(3)commentonthefutureeconomicpotentialofthese
mineraldepositsinNewMexico,TexasandeasternMexico. Earlierpapers[23,24]describedthegold
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potentialofGPMdepositsinNewMexico;thispaperfocusesontheREEpotentialofGPMdeposits.
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ThisworkispartofongoingstudiesofmineraldepositsinNewMexicoandincludesupdatesand
reviosfi oonnsgoofinpgr isoturdwieosr kof[ m4,2in3e,2ra4l, 3d0e,p31o,s4it8s] .in New Mexico and includes updates and revisions of prior
work [4,23,24,30,31,48].

FiguFirgeu1r.e E1x. tEexntetnotf othf tehNe NorotrhthA Ammeerricicaann CCoorrddiilllleerraann aalklkalailnien-eig-ingenoeuosu bseblte [l2t,3[2,2,33,,2234,,4294],.4 9].
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Figure2.MiningdistrictsrelatedtotheNorthAmericanCordilleranalkaline-igneousbelt(GPMor
Figure 2. Mining districts related to the North American Cordilleran alkaline-igneous belt (GPM or
GreatPlainsMargindeposits),RioGranderift,calderas,andotherEocene-Mioceneminingdistrictsin
NewMexico[23,24,27,31,32,48–54].GPMdistrictsaresummarizedinTable1.
Great Plains Margin deposits), Rio Grande rift, calderas, and other Eocene-Miocene mining districts
in New Mexico [23,24,27,31,32,48–54]. GPM districts are summarized in Table 1.
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Table1.GPMminingdistrictsrelatedtotheNorthAmericanCordilleranalkaline-igneousbeltinNewMexico,Texas,andeasternMexico.Theminingdistrictsare
arrangedroughlyfromnorthtosouth,CrippleCreekisincludedonlyforcomparisontothesoutherndistricts.NamesofminingdistrictsinNewMexicoareafterFile
andNorthrop[55]whereverpractical,butsomeformerdistrictshavebeencombinedandnewdistrictsadded.ThedistrictidnumberreferstotheNewMexicoMines
Databasedistrictnumber[53,54].LocationsofdistrictsinNewMexicoareshowninFigure2.Typesofdepositsarenumberedasdiscussedinthetextbelowandare
describedinMcLemoreandLueth[32].Magmaticcharacteristicsareusinggeochemicalandtectonicdiagrams[56–61].Databaseofgeochemicalanalysesusedisin
supplementalmaterial.WPG=withinplategranite.VAG=volcanicarcgranite.Goldproductionisfrom[5,26,62].na=notavailable.
AssociatedElements GoldProduction
DistrictID Name (ProducedAreinBold AgeMa(BoldItalicsAre TypeofMineralDeposits MagmaticCharacteristics[56–61] (MetricTons)*Gold SelectedReferences
Italics) 40Ar/39Ar) ResourcesRemain
CrippleCreek, Veins(1),brecciapipes(2),gold
na Au,Ag,F,Te 32–37 na 731* [5,26,63]
CO placers(9)
Magnesiantoferroan,subalkaline,
Veins(1),brecciapipes(2),Mo
DIS237 Questa Mo,Be,F 22.7–28.5 alkali-calcictocalc-alkalic, 0 [53,63–71]
porphyry(3)
metaluminoustoperaluminous
Magnesian,subalkaline,alkalito
DIS238 RedRiver Au,Ag,Cu,Mo,Be,Te 24.9 Veins(1),goldplacers(9) alkali-calcic,metaluminousto 0.01* [66,67,71–73]
peraluminous
Magnesiantoferroan,subalkaline,
Veins(1),Cu,Pb,Zn,Auskarns
DIS019 Elizabethtown-Baldy Au,Ag,W,Te 29.1 alkalitocalc-alkalic,metaluminous 14.6* [73–77]
(4),Feskarns(5),goldplacers(9)
toperaluminous
Magnesiantoferroan,subalkaline,
DIS018 Cimarroncito Au,Ag 29.1 Veins(1),goldplacers(9) alkalitocalc-alkalic,metaluminous 0.003 [73,75–77]
toperaluminous
Ferroantomagnesian,metaluminous
Veins(1),brecciapipes(2),
DIS020 LaughlinPeak REE,Th,U,F 22.8–32.3 toperalkaline,mostlyalkaline, 0 [44,78–83]
Th-REEveins(6),carbonatites(7)
mostlyalkali,WPG
calc-alkalictoalkaline,ferroanto
magnesian,calc-alkalictoalkalic,
DIS180 Cerrillos Au,Ag,Cu 28.9 Veins(1),porphyry(3) 0.08* [73,84,85]
metaluminoustoperaluminous
rocks,andplotasWPGtoVAG
calc-alkalictoalkaline,ferroanto
Veins(1),Cu,Pb,Zn,Auskarns magnesian,calc-alkalictoalkalic,
DIS186 NewPlacers Au,Ag,Cu,Te 33.7–33.9 3.6* [73,86,87]
(4),goldplacers(9) metaluminoustoperaluminous
rocks,andplotasWPGtoVAG
calc-alkalictoalkaline,ferroanto
Veins(1),brecciapipes(2),
magnesian,calc-alkalictoalkalic,
DIS187 OldPlacers Au,Ag,Cu,W,Te 34.3–35.8,33.3–31.7 porphyry(3),Cu,Pb,Zn,Au 14* [73,86–91]
metaluminoustoperaluminous
skarns(4),goldplacers(9)
rocks,andplotasWPGtoVAG
DIS271 Duran Fe ? Feskarns(5) na 0 [92,93]
Veins(1),brecciapipes(2),Fe Ferroan,metaluminousto
Gallinas
DIS092 Cu,Ag,REE,F,Th,U,Te 26.5–29.7 skarns(5),Th-REEveins(6), peraluminous,alkaline,mostlyalkali <0.001 [73,92,94–111]
Mountains
carbonatites??(7) toalkali-calcic,A-type,WPG
DIS098 TecoloteIron Fe ? Feskarns(5) na 0 [92,94,112]
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Table1.Cont.
AssociatedElements GoldProduction
DistrictID Name (ProducedAreinBold AgeMa(BoldItalicsAre TypeofMineralDeposits MagmaticCharacteristics[56–61] (MetricTons)*Gold SelectedReferences
Italics) 40Ar/39Ar) ResourcesRemain
Veins(1),brecciapipes(2),Cu, subalkalinetoalkaline,ferroanto
[94,113,114],unpublished
DIS093 Jicarilla Au,Ag,Fe 39.16–45.63 Pb,Zn,Auskarns(4),Feskarns magnesian,calc-alkalictoalkali, 0.3*
data
(5),goldplacers(9) metaluminoustoperaluminous,VAG
WhiteOaks Veins(1),Cu,Pb,Zn,Auskarns [73,92,94,115–118],
DIS099 Au,Ag,W,Te 31.7,34,34.75 na 5.1*
(LoneMountain) (4),Feskarns(5),goldplacers(9) unpublisheddata
Ferroantomagnesian,peralkalineto
Capitan Veins(1),Feskarns(5),Th-REE
DIS091 Fe,REE,Th,U,F,Be 28.3 peraluminous,subalkaline,alkalicto 0 [43,46,73,92,94,119–129]
Mountains veins(6)
calc-alkalic,A-type,WPG
Veins(1),porphyry(3),Cu,Pb,
Metaluminoustoperaluminous,
Au,Ag,Cu,Mo,Fe,Te, Zn,Auskarns(4),Feskarns(5),
DIS095 Nogal-Bonito 26–33 mostlyalkaline,alkalitocalc-alkalic, 0.5* [37,38,73,94,130–143]
REE(?) Th-REEveins??(6),goldplacers
WPGtoVAG,A-typetoIandS-type
(9)
Metaluminoustoperaluminous,
DIS096 Schelerville Au,Ag 26–33 Veins(1),goldplacers(9) mostlyalkaline,alkalitocalc-alkalic, <0.01 [73,94,140–144]
WPGtoVAG,A-typetoIandS-type
Veins(1),Th-REEveins??(6),Fe Ferroan,metaluminous,alkaline,
DIS132 ThreeRivers Fe,Au,Ag,REE? 28.95–28.24 0 [92,141–143,145]
skarns(5) alkali-calcic,VAG
Magnesian,metaluminous,alkaline,
DIS216 JonesCamp Fe,Au 28.88 Feskarns(5) 0 [92,146]
alkalitoalkali-calcic
Magnesiantoferroan,metaluminous,
DIS241 ChupaderaMesa Fe,Au 30.2 Feskarns(5) 0 [92,93,147]
alkaline,alkalitoalkali-calcic
Magnesiantoferroan,metaluminous
Veins(1),porphyry(3),Cu,Pb,
toperaluminous,alkalineto
DIS129 Orogrande Cu,Au,Ag,Fe,Te 45.6–41.4 Zn,Auskarns(4),Feskarns(5), 0.5* [45,73,148]
subalkaline,alkalitocalcic,WPGto
goldplacers(9)
VAG
alkaline,ferroantomagnesian,
Organ Cu,Pb,Zn,Au,Ag,F,Te, Veins(1),porphyry(3),Cu,Pb, predominantlyalkalic,metaluminous
DIS030 26–36.45 0.35 [73,149–157]
Mountains Be Zn,Auskarns(4) toperaluminous,andplotasWPGto
VAG
Cornudas Veins(1),brecciapipes(2), Ferroan,metaluminousto
DIS128 REE,Th,U,Be 36.3 0 [28,158–171]
Mountains Th-REEveins(6) peralkaline,alkaline,alkali,WPG
Ferroan,metaluminousto
Hueco
DIS255 Fe,REE,Th,U 34.5–34.7 Feskarns(5),Th-REEveins(6) peralkaline,alkaline,alkali,WPGto 0 [171,172]
Mountains
VAG
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Table1.Cont.
AssociatedElements GoldProduction
DistrictID Name (ProducedAreinBold AgeMa(BoldItalicsAre TypeofMineralDeposits MagmaticCharacteristics[56–61] (MetricTons)*Gold SelectedReferences
Italics) 40Ar/39Ar) ResourcesRemain
RoundTop, Th-REEveins(6),peralkaline Metaluminoustoperaluminous,
na REE,Be,U,Th 36.2±0.6 0 [8,42,173–186]
SierraBlanca intrusion-relatedREEdeposits(8) WPG
VillaAhumada
na carbonatites, U,Th,REE 36.35±0.27 Th-REEveins(6),carbonatites(7) na 0 [47]
Mexico
Veins(1),Th-REEveins(6),
Aguachile
na Be,F,U,REE? peralkalineintrusion-relatedREE Alkali,peralkalinetoperaluminous 0 [42,49,187–189]
Be-F-Udeposit
deposits??(8)
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2. MaterialsandMethods
SevendistrictscontainingREEdepositsarehighlightedinthisreportanddescribedinSection3
ofthisreport. Datausedinthisreporthavebeencompiledfromaliteraturereview(referencescitedin
Table1),fieldexaminationandmappingbytheauthor,andincludethemineralogy,geochemistry,and
geochronologyofthealkaline-igneousrocksandassociatedmineraldeposits. Thegeochemicaldata,
analyticalprecisionandaccuracy,andanalyticalmethodsaredescribedinthevariouscitedreports
(Table1).
MineralandchemicalcompositionsofigneousrocksintheGPMdistrictswereobtainedfrom
numerousreportsascited,aswellasunpublisheddatabytheauthor,andareinthesupplemental
material. The data were plotted on various standard geochemical and tectonic diagrams [56–61]
and compared. These chemical plots are standard methods used to describe and classify igneous
rocksandprovideabasisforcomparisonsbetweenareas(Table1). Onlyselectedplotsareshown
forspacelimitations. Avarietyofnomenclaturesfortheigneousrocksinthesedistrictswereused
inpreviousstudies,becausetherockstypicallyareporphyriticinafine-grainedmatrixandinclude
shallowintrusionsaswellasextrusivevolcanicrocks. TheInternationalclassification[190]isused
inthisreport,wheretheprimaryclassificationofigneousrocksisbaseduponmineralogyand,iftoo
fine-grainedtodeterminemineralogy,bytheuseofwhole-rockgeochemicalanalysesusingtheTAS
(totalalkalisilica)[190]andR1-R2[191]diagrams.
Mineraloccurrences,deposits,mines,andprospectswithinGPMdistrictswerecompiledfrom
publishedandunpublisheddata,summarizedinTable1,plottedonbasemaps,andenteredinthe
New Mexico Mines Database [53,54,62]. Mineralized areas were examined and sampled during
1980–2017bytheauthorandduring1982–1993bytheU.S.BureauofMinesaspartofmineral-resource
assessments[82,102,104,119,133,168]. ArcGISwasusedforNewMexicodepositsandotherregional
mapswereusedforTexasandMexico.
Anyresourceorreservedatapresentedherearehistoricaldataandareprovidedforinformation
purposesonlyanddonotconformtoCanadianNationalInstrumentNI43-101requirements,unless
otherwisestated.
3. DescriptionsofSelectedAreas
3.1. LaughlinPeakDistrict
The Laughlin Peak district (DIS091), located within the Laughlin Peak-Chico Hills igneous
complex (Figure 3), is in the southern portion of the younger Raton-Clayton volcanic field in
northeasternNewMexico,alongtheJemezLineament. TheLaughlinPeak-ChicoHillscomplexwas
emplacedjustbeforeoratthebeginningofRioGranderiftextension(22–37Ma[44]). TheLaughlin
Peak-ChicoHillsigneouscomplexconsistsofavarietyofalkalineextrusive(trachyandesite,32.3±1.5,
K/Ar; basalt, trachybasalt, rhyodacite) and intrusive lithologies (Figure 4a), including trachyte
(36.7±1.3Ma,K/Ar[78]),trachyphonolite,trachyandesite,phonotephrite(25.3±0.9Ma,K/Ar[79]),
ChicoPhonolite(22.8±0.23;40Ar/39Ar[83]),lamprophyredikes(24.06±1.01Ma,K/Ar[79]),and
carbonatitedikes[44]. Manyofthevolcanicandintrusiverockshaveaporphyritictexture,suggesting
emplacement near or at the surface. Associated igneous rocks in the Laughlin Peak district are
alkaline(Figure4b;alkalitocalc-alkalicaccordingtoFrostandFrost[59]),predominantlyferroanto
magnesian,metaluminoustoperalkalineandplotasA-typegranitesandWPG(within-plategranites
accordingtoPearceetal.[57])(SupplementalMaterial). Theassociatedigneousrocksexhibittypical
lightREE-enrichedchondrite-normalizedREEpatternsofalkaline-igneousrockswithnoeuropium
anomaly(Figure4c). Veinsarehostedbymostvolcanicrocktypes,exceptthecarbonatitedikes.
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