High-grade Granite-related Molybdenum Systems: Classification and Origin

States t::;eological Survey, School of Mines, Reno, Nevada 89557-0047 U.S,A,

United States Geological Survey, 1200 University Drive, Anchorage, Alaska 99508-4667 U.S,A,

and

H.J. United States Geological SurveYi MS 90S, Denver Federal Center, Denver. Colorado 50225 U.S,,,-;\.

WI{, and Stein, HJ, 1993, granite-reL'lted mOi'VD>CLenL,m in Kirkham, R. V, Sinciair, TrdJrpe, RJ and Du,ke,

Carten, RR, White, C~lassification and Deposit Modeling: ;",OhWlrYi{ Assoctation of Canada, Special Paper 40, p, 521-554,

Abstract extractable molybdenulfi- is contained or

deposits. Based on hydrotrJ.£rmal, the divided two associations: (1) rift-related deposits

rhyolitic stocks; and (2) low-grade, arc-rela.ted dePOS1tS or plutons. rllrI;nVTV two

rhyolite-aikalic suite or a monzogranLie respec-the compositional. structural and thermal differences betu'een interplate

rift environments, Th,..ese differences affect th~ that upper crustal

generation of mafic tnagma. and tite associated potassium. sodiurn, niobium, tantalum and uraniurn in tr~ COTL'., ide red to the Jtlrrn..ation nf high-grade O()TlOrtVT'V flH)LVI"Lf";;IL,n

The high-sdica rhyolite-alkalic suite contains - that are

centres (1 protracted period of regional silicic magmatism, The or with brittle failure (imbricate norrnal

exrel1aea upper crust. Differences an!.ong subclasses the GS'1f1Pr'O"OI1£,r£,

States Geological Survey, 913 ~ationaI Cente::, Reston, Virginia 22092 C.S.A.

521

CARTEN E1'

reflectIng thr; addition fluorine, chlorine, sulphur introduction of volatiles scavenge cornponents L'olumes

f'nrichissement concomitant en fluori intraplaque

TlC'rTrn'Vr"fJllPa teneUT.

magmas (par ex., injection Pine Grove) et Ia formation

UfUlnnrUPllLl-'flJ dans

peuuent etre subdiuises en deux regroupernenrs: de lnagnLatisrrlJ! de acc()mp~ones de stochs

a faibles teneUTS dan.s un contexte de fluor" Les f5--risements

d£ rhyolites

pniCL4nt irarnediatenlent au accornpagnent Ia rn;'m'JLW;m

tion COUTante. ces evenements seraient ie re{let d 'un apport de felsique. et plus solubles tels Ips

au degazage du

the associated Granite-related mineral denum,

522

of a common sequence tectonic events that centrations of metals.

an upper crustal chamber

differentiation of intermediate to felsic magma ~ or

volatiles into the root zone of

of vol-residual magma into a near-surface

environment of 1-5 0. of volatiles and are ,>n~'~~~., dur-

solidification of magma;

In VCln-

filled fractures or in skarn. interrelated variables affect final pro-

derived from this sequence of events: the

Western United States

GRANITE-RELATED MOLYBDENUM SYSTEi\IS

523

Dep(lBiI (Ma) MethoJ

1. Clunax

Urad -I Il,.

Middle IIltn. Mt. Emmo"s I\edweli BaBin Mt. Hope

Mt Plellllllt1t. HI. Pine, Grove

I. Questa Cabin

14. Bordvika l~ellk

16. MalmbJerg

18. Flattll11eljeld

USCO LJSMT

USCO USCO

USNV

CNNB USUT

USNM USNM

NllWY USTX

N!(WY WILD

Cl(LIJ

Nordli NllWY ~.O. Throe IIi vcr" USN1\!

Poak USNM

Adanac

Aniluramba HalJ Huttt., !:lell Moly

llJol'nttarn ~ltn.

CanlcBnian

CNHC

AUQL

SW[)N

CNIlC Pl.!'!'!

KAl'

FT

:J9 KAr

1718 I( At 36<18 FT l(·At

l(·A!',llo·Sr

j(·Ar, ArAr 1(·Ar,

{(·Ar

Estimate 34<17 At

71

HbS!' FT l(·Ar

,tH Esttmate

24(J

Ho·Sr I(·i\r

El:ltilOulc

KAr h.

UFb ~8 JlJ7 K Ar

HI!

tedou i c and and

Table

Production t·

grade References (Wt.'fu) Metal (%1 (%)

Gmnite-reIUl()d. lVIo: high·siliell He-alkalic Bookstrom 76 Me

lUi. and L.W (utl[lltbl.)

and (unpub!.) ~lu"vlt1 e( (IY7:Jb)

Ranta (1974) and Ga ley (1982)

Galey II. Amini (writ.ten comm., l~e2) Siloerman and l(ooiman of OfJ86) Keith a/.(19Sill

,jobnson 01. (1990) ,Joitnsotl al. (1990)

Naeser et al. (I B80), 01. (1986)

Frice Hnd (1986) Sundvull (1978)

al. (1910),

uI (19'19),

Cleadow Hnd Brooke (HI79) Cleaciow LWei (19791, Stens!.t·op (lV~7)

Schonwandt anJ (lD83) 'I'[,omp0(./11 (lV7'2)

1',13, ThoHl{HHJn (puru ('U!l\riL,

lllJO)

n

77

76 76

76

77

Mo

Me

Mo Mo Mo Mo

Mo\\'Sn Mo

Mo Mu

Mo

'I'll 1110 'l7r MoWNb

Mo Mo

771 Mo

Mo Mo

771 Mo

Gl'anite-relt!ted lVIo:

Hlft·C

Hift·C

T T

T

T

A

A

A

A

0.240

71

0.090 0.098

0098 lI.

100

Ol'l(J

0.144 o.m)O

O:lJ 0

o 00·10

0.1

UOS·I

CI,ricllopher and Pinson!. (19b2) Mo M 0.U9" al (J 98~)

Witcher (1975), Hocum (1978) Mo M 0.1J70 1\",tud (1971)) Mo Iv! 0.100 Caeter M" M 0 Wilson and Fullicli (l8K2) Mo M 0 Wh,le cl "I. WIGS) Mo \\ 0.074 [Itlltlel and But'LOn (985) 71 Mo M 0.051

Mn cllt·oH

(~!t) (%1

0.12U Mineable 907 ~6G 0.180

() 120 0.060

1 Of) 0.036 ~l",eable

376 0.060

141 0.1 Mineable 0.060 Geologic

0.120

0.120 Mineaulc O.O(i(j

40 0.200 Geologic

0.100 Mlflenble

O.lOO

IH] 0.0:10 ecologic

O.O(ill Ceolog ic 0.030

14 C(;o)ov,ic Mineable

GtJuiuglC

1990) S.H UnpuLtI. Unpubl. datil

01 (19880) Wllilaco el a/. (IU'18j

W.H. ,Vltile (pet's. romm., 1990) Wll.Wbite ltJHO) Hantn (974)

cl (l981) Thomas and Galey (1,182) WHo White (writt,·" comm.,

cornm, 1::100) Kooiman (l:Jt\il) Silliloe (J~3()), IlK Hantn

!9R~}

Climm., IfJ~)O)

Oltlwre (wr:tI.ctl comm., 1979)

Call1crun (l986)

Schotlwandt(1979) (l979), W.H.

COlum., 1990) Ihlen at. (198:1.)

ond 'j'howaR'"n (1984)

and (198·t)

(1986) ("dUB Hnd Tbompson ( Thooq)I:lUI,1 (lU:i~l

'I' H, ThUluptiu!\ (pOrt:L romm"

I~DIJ)

W lI. White (~1It'8. 1990) l\\l'khllill al

cOtnm.,I!)90)

(Ul7il) Oblander (lDH5)

Kirkham (ID8~~)

Knittel and Burton (198;',)

Cannivaf1

KOlllll'ad

~!I.. HU8kin ~lullkl!

4(). Pidgeon Ma

Quart'. Hill

I(ed Bird Hed Mountuin

4G. Roundy .1'/. Sturie Moly

Trout Lake [,0. 'l'yrnYllu1.

York,] I fardy

Buckingham

Hall

Jill

Mocoa 60 Ml. Tolmall

Hilllt"

CNHC PE[{u

CNIlC CNBC CNqU

CNlJC

YUGU CNBC SWIJN CNON c:,,({U

USN V

US!\K

CNLlC CNYT

LIS 1Il

Lilms CNBC

USNV

MXCO

lISNV

(j l:if'.

USWA

lJSNM

30

57 Tertiury

6670

iO

]Gli fiO·6U

:31

KAt

!( AI" K Estimate KM,HbSr

I(M

U PO E;jtlmale

1\

KAr K Ar

I\ Ar

I<

KAr

K Ar

KAr EHttrnullJ

KAt, Ul:'L '1

KAr

1<

1197d)' ai. (l~79)

Sinclair (1~8fi) Wilaan alld Fallick (l8b2)

d 01 (l979)

(1981)

Sinclai,' (19i)6},

und l(uhlcrL (l91lG) (1981)

Pant.eleyev (1980) (107:1&),

Schmidt ai (1982) Boyle Hnd Leit.eh (1

PaKlllav (1977) ( 1981

McKee (1 fJ:!2)

Holliater (1078u) (1978)

W.lf Wb'tc (perti 19~1())

Schcrkcnbac:h d (lUS:,) Loon anJ Slillor (lDSl)

~baver (19841 WaHm comm.,

Sdlll"o ct "I. (198·0 W.C. Utlahack (I/C"8

Thompson (1982)

67

70

mg

mg?

!fig

68

?:l

7:3

Mo

Mo Mo

MoW Mo Mo MoBi ~!IJ'W

Mo hlo

Mu 1\10 Mulli ~lo Hi Mo

Mo

Mo Mo

Mo

Mo ~'1o"W MoW

[e-related

70

mg

mg

~·lo·Cn

M(I·Cu

~Io

Mo·en

Moen

Mo·Cu Mo ell

:\IuCu

Arc liift·C

M

:VI Iv!

Iv! Iv! M

Iv! hi

M M

M

M

1\1 M

M

M

M M

o O:JG

O.()Vl

O.ISO 0.087 Ill!

00:31 () OBO

O.ODO o OOBO

0060

O.Ob4

(Jon O.OBI 0.108 0.100

O.20S 0.078 0.110

0.138 () 065

lJ

(J.O:')"

0010 0069 O.OiIG OOJ(J 0.074 (I

0.091 0.100

0.056 (i.OS! 0.070

0.034 0040 (UIIO 0074 o

0.060 0071

(103C1

0100 O.ODO o O,lQ 0.100

Geolugic 10()

30 o

108 iJ.u60 Ueologic l\1ilH!able

162 Ce,ilogic 14

C(:ulogic

Guulo"ie Gvol()/iiie

Geologic 181 O.O:lO Gculogic

G.OOO

1,216 0.027 G cologie 793 0.060 Milleable

O.OGO IWi O.IJGIJ

Geulogic 101 OO·H) 181 O.ObO Geologic

0.060 50

0.120 Geologie 1l.()6(J Gcologic

Gt1ulogic O.U60 (J,,(,logic

00

060 Geologic 0.060

IllJ ()O~lO

126 0.060 hlinoablo Minl'able

907 Ccolugic

G00jOgie

'19~1 0.036 Miru]llblc 0.027 Geologic

Worl.hington (l9'l7)

Ki,.kl,,"1\ el ,,/. (1982) (J lfollistcr(197SlJ)

Sut\l:OV (

Kirkham cl oi. NuLlo 01 a/. rt9iJ·1, 19iJ61 I'lid,c,. and ~lCl.lougllll (I WIG) H.T (wnttell comm., (961)

I{lrkhurn ('l (ri. (1982) Ohltmder 11885) Kirkham cl nl. (l Dil21 K,rlrhaltl (ID8:1,) K. I(oxlo and E. Ilanl.a (writl.en

191>2) K. floxla Hanta

comm, 19\JO) (omlll.,lfJ90)

Kirkham Wid;!') and Kalrlerc (I fI8!i)

Kirkham (1982) Bloomer (If)81)

Schmidt "I. (1982)

Boyle and (l9S:l) Sutuloy (19'78) W.H. Wbite (pors. comm., 19(0)

Whito 10:1())

W.H. cumm.,I!)90) WH. CtHllm,I!I!II.!)

W H comm.,IUHO) IV II, Whit" comm.,I!i!)OI IV.!!. COll\ l1\. , 1!1!)(t) WIt. ,'ottltll.,I!IDOI W.l COinm, lU90)

S.H comm., t!190)

Sill,loe cl al W.C.

cumm.,19di,)

119GB, and comm., 1990;, [1"lilSter (1978b)

Table X

cut-of!' CmJ11try" (Mo) Method HefereneeN (wt.%) Metal (%) (%)

GraniLtl-:related Andina CILl': b nl. (1983), :3,000 Geolot,ic

(1085) Damon and Mauger (l9GGI 0030 0480

(lGBI) 0.031 0.348 308 While al. (l8G8) Warnaars o/. (UJ78) Ndtionul

CNYT l( Ar Godwin gel O:l7O l\CUR 11 Muller·Kahle and Damon Illg eu·Mo 00:10 0700

(lD7(J), Snelling ([970) G~ CILE I{·Ar Ambnl8 (19'17) mg Cu·Mo () SululoY (1978) 70. Copper Mtn. CNQU K·Ar Alkuck (l982) gd'lIIg Cu·Mo () Allcoek (1982),

Kirkham e/ ,,/ (1982) L'EIW 01. (1990) Cll·1vh) O.02fi 0.700 SUlnloy (1\)711), 8alchwdl (1983) C!LE Custufson Hnd Hunt (1976) Cu*Mo LIllO 5:l5 An;brnB (1978)

73 ill ']'eniente (1983 ) Cll-illo 0030 0.68U 8,350 SUIliloy (1978), Gilmour (1982) 74 Gnawed Mln. (I ()45 O.~'/O ,14 Kirkham et (I~S2)

Hlghmont CNBC Nortb role mg Co·Mo 0045 0.258 l\irl,ham Cht'lsmns III (I9tlfll

'16 Lawici<u (1976) Cu-Mu 0.050 0:300 100 SUlulov (1978), Sillitue et 01 (1984)

KiyulykhUzen' UlmS Co-illo 0.050 1000 Sutuloy (l9'18)

La AlumLrura ACTN 00·10 0400 100 Slltuluy ( Los l'elambres CILE 10 I llild Sou v iron

0.029 0.280 IS] Miller (1976) PErm 0.022 o.no Gilmoor (lfJb2)

~Iitleral Purk USAZ n KAr 72 Cll·Mo 0.530 Lowell H3 M'Jl:hu CILE gd 0030 l.OOO 107

Needle Min. O.O:l5 lIirkham et ai (19821 Ox Lake 86 l{-Ar f{ichards (1976) }\lramount CNllC 186 (1972) Kirilham (1982) IJuHhpup PEHU 15 ell-Mil 0.('50 O.bOO Geologlc Gilmour (lfJll~),

(1984 ) Quellaveco PEf{lJ CuMo O.1J30 O.U50 200 liu!l,sler (1~J7ba)

CILl:: Cu·Mo () 0·10 WAN Mo 00:10 Hamill'"1 (1975)

Hnd

Schar, Crook CNIJC 18(, K·Ar Pailluloyoy unJ DuduH (19'72) 0020 03ilil HIl7 l\lrkboltl vi 01. (I USAZ I( AI' unJ KiHlloc (1962), Cu·Mo (J O:IO·! 7 I(rlli, llD7b)

CuMo () 024 0.130 113 Guologlc Cooner (19731 I{elly ml(7) CuMo 0 0.ti33 41:1

libted for whicll reii"lrle grMI" and lonnage uvailable. IlcpOSll" without and tonnage informaLion mentIOned tho lI1.c:iud"d in for add,tlonui or wldcomed.

Bulletin 16(1:J recalculated

Hno:wd on [tr!hyJn.Jll::l com.pol:liLtvll., normalized Lo 1000(0; granodj()riU~ !lod [(ift designatiun mantle or deep mantle upwelling;

IVlle; '1', transitional type; A, ulkul,r M, 01' IJrll'l IIf

of an individual IS

minerai economics. As an eXlli'I1-

have a

reserves underestimate or do not include copper. these most de-

that contain economic or subeconomic con­centrations of either of these metals are either copper

0.3

J<

~

0.1

" 6

-=-------~- -~~--=-~ - 6

?fl 0.03 6 -0 ~

0.01

0.003

0.001

O. i 0.3 3

literature.

GRAN[TE-R,~LATED ~lOLYBDENUM SYSTEMS

. } loS are

This restricted distribution of ages cannot ex-the erosion of older

erOSion no

with the onset of basin blocks are buried beneath detritus and should have

of survival similar to that of other basin­such as sediment-hosted sul-

the mantle and crust, as a result of processes in the lower mantie related to subduction

As will alkali basalt is a critical in the formation of

rocks in arc formed in association with more felsic

rocks continental-rift

527

CARTEN ET :\L

in the

m nCWT, nFT">'

mafic to intermediate

528

140

r H ~

i 20 L- N ~{

o

break do\vn~ .A.s V/ill be

100

and associated ore bodies are into tectonic environments. The

of related to intracontinen-

Cu-Mo, and Me-Cu Deposits

'.MO 16,0 million tonnes; -

OJ 5i6 million iormes

200 300 400 500 500

the literature.

IS to events and processes re-

for their occurrence. fea-tures common and distinctive

we can evaluate the effects of extensive intensive variables on the outcome The the number and

cause economic recent additions to

sive variables. !JV'~0'~r,~ C-lJlCH 'lo;C" in extensive and inten­

classification schemes and

3

models are less less reliable,

based and conse-

, • Kll,yoirtE'-ilJKal;1C suite , IT'diIion tOfmes

...--2 r +-'

~

0 ~ -

o o 100 200 300 400 500 600

calc-alkaline magma. Less successful classifications

of t\VO fundamen­environments: rift. The rift environment

related , Bookstrom.

tholeiitic to the presence of normative This also includes

normative transitional basalts that eline-normative alkali basalts. In

with concentrations of in tholeiitic and alkaiine magmas and enriched in alkalic rocks.

Differences trace-element and volatile contents of crustal magma in part reflect the of mantle from which basalts were derived. DePaolo crust in island-arc and continental-arc duct ion

tin ental and mantle

has em-

GRANITEREL\TED yl0LYBDENUM SYSTEMS

mantle sources

associated with magma million years that form in the middle to later

of an extended of tism. As IS

fractionation col­an upper crustal magma chamber

strontlrnn-support a silica associated with Henderson and Mount Emmons

Stein and Crock. 19901. mafic lower crust or subcontinental mantle may have

roles in the of evolved magma critical volatiles, Involvement of upper crust in the level chambers is minimal

the heat

transfer of mass, essential to the formation of economic tems, The

4' IS tone common occurrence of mixed mafic and felsic mag·

gases are consistent with a

529

CARTEN ET liL.

tion et aI., 1978: Irwin and concentrations of fluorine are

environments associated mafic volcanism

al the abundance major elements

-o

530

0,4

0.2

based classifications are

, ,1' m magma Laan are vana-the abundance of trace elements, Unfor-

and rare The common oCC'Jrrence of

the loss of elements to effect subsolidus

:0.099

A .. 0.209':: A

. A o k-__ ~ __ ~L-~~-LL-__ ~~ ____ ~~~

0.02 0.03 0,05 0.1 0,15 0.2 0.3 0.4 0.5

thermal alteration hinder any sification, Because of

the combined of both classes

UolHlt::i'~cl1n similar processes of ore formation,

8

N = 47

0.8

0.6

0.4

0.2

., .... --i

:3 30 100 300 1000

Differentiated

100 tonnes (or 200 and t"£ mean 0.09% Mo and 50 lUt

features. This elements of the tectonic 0V"V'Uh

as subclasses for discussion purposes, of this suite are considered as of

contL'1Uum. All of these de-

05

0.3

s!-"

0.05

0.03

0.02

0,01 1000 10000

Climax-Henderson Mo Me-Cu CLl-Me II A

o :2:

GRt\NITE·RELATED MOLYBDENUM SYSTEMS

Climax

as intermediate as used in pa-

The Climax and Henderson

the mag­and tectonic characteristics of

Climax and Henderson

0.35

0.3

0.25 !II Climax

0.2

iii Henderson

O. 5

0.1

0.05

o L-~~~~~ __ ~~~~~~ __ L-~~~

o 200 1400

Climax-Henderson Transitional Alkalic

531

ETAL.

Structural and

Pre-e~ wae of a'.lSW Colondo mmernl belt w~

Composition of initial ~Im in !he region

532

Calc-Iilkaline (rntermediate )

Table II

characteristics of selected ,,,,rn!lV,'V nlOlyr,ae:nttm

28 18 22

Cootinelltl!.! Continenti!.! Cootillif'llllIl ex!cnsion extel!2ion exten.rion

Yt:3 Ye3 Yes

50 50 25

-280 -300 -210

Vent Vent? Vent

Colorndo minad CoIorndo ll'Iinad Pioche minetll.! belt belt beit

''Prvto~ Rio Off~ofRio Off~of~

GWlderift G~deRift Great &sin Rift

Post-ore COO!c~eous Conternpcnnrous to post-ore (to 1 TIl. y_ younger)

Calc-allWine Calc-allWine Calc-allWine (m~); (gWlodiorite; (andesi te-4£ci!e-

mo!1ZOO.ite &!ldesi~ite) myoii!c }

rhyolite (JT) myolite ()6)

Yes Yes

No Yes Yes

No No No

37

Conrinellllll ene!!.$ioll

Yes

30

-190

Veil!., slIYill

~

Post-oce

Calc-allWille

?

?

No

GRANITE-RELATED .:'vlOLYBDENUM SYSTEMS

I High-silica HlJ ~ik,.lir suite Differentiated I Transitional Alkalic I

I ~ I BigBen uvePeak mbja:g Nocdli I Boo:!vib Compolli!ed ~

I 23-25 51 I 36 30 247-200 I 290 30-186 ¥d I

I i

I !

~ i Con!:inenu.! I Con!:inenu.! Continenu.! Continenu.! Coo.tinenu.! Col1Unenu.!

I e~ I I extension eJttelYioo exteruion exteMioo ! e~iol1 ~io!l

I Yes I Yell I Yes Yes Yes Yes Corr,mon I I

I 40-50 1

40 40 I 35 30 I <40, typiWJy 30-40 ! !

! I I I I -270 ! -160 I -ISO 7 '[ ? >-2"'1 j

I ~mIqi!l I None Ver!J.1 I Caldera mugin; Caldera UJden~

I GelW:illy 00 rol~ I

I vent? margin edifice pre:rerved I I ! !

I lemezwne'7 I I i None B£mble li_ bell:

I Yes

I

Lewis IDd QlllK None &mille I ! I line I I linear belt

I L

I ~~Rio I Trn.ruverne I

'"'ProtoRRio Initial magmatic Oslo Rift 0310 Rift i

?

Grnnde rift Gomde rift lineament I i ~yrj j

I I Con!.e~ ICo!lte~ I Contemporaneous '7 '[

I Pre-ore to I I contemponme<:lW I to~-ore I to ~-ore (3-5 I

I I

I I m.y. yoonga) I , I I

Ca!c-~e Calc-allailine Alkaline Tholeiitic basalt; AlWine Thokiitic~ Calc-alb! in"

(mdesite-dacitt>- (mten:nediate) ; (traclI ybasalt- traclIybasalt- (syenite- ttu:hyl:;asa!t- (quartz diorite -

myolite alkaline (syerutt>- traclIyte-myolite ) tnl.chY'~yolite monzonite) traclIyte-rl:iyolite quartz monzodiorite -

,UHVU" HC,

, I a'1gv",,,n

High-silic£ High-silica High-silica High-silica I-lig,."'-silica Hioh_.ili"" '-~

myoiite (TT) myolite (7T) rhyoii~yte myolitt>- myolite (TT) myolite (TT)

No ? No No ? No

Yes Yes Yes Yes ? Trace Yes

Yes No Yes Yes No No Yes

533

CARTE]'.; ET

~..3tics ClilllJiX Mt.Emmons MlHope

T~lement composition at productive in;rusiOrul

RbISI' 25 135 6.5 10 4.2

t<olZr 1.7 1.6 OA2 OAl 7 (No = 24 ppm)

u (x cl!oOOrite) 80 95 80 40 ?

N¥+Kji (wt.%) 93 8.6 Ill; 117 ?

~ed co-genetic rock;

Syeru~c rocks No No No No No

~yre yefj~te) Yes~tite) Yes Yes

I

?

Albli ~t-;:mdesite No No No Yes ?

Dilcite O£ mollIDgrWte No No No Yes

Evidence foe lll.lWc-felllic Yes Yes No Yes ?

~mixi.ng

~ideoce time for unmixed >2 lILy. >L5lILY· ? :>;1 m.y. ? high-level InIilgIDa in ciwnber

In;rusion or extrusion of topaz ClJ.ill;; Mountain 0-4 nLY. Woods Mountain Boston PeU:: Wah Wah NOll£ myolite (age relalive to yooager) (4 m.y. younger) (8 m.y. younger) Moon~(1-3 m.y. ~ization) younger)

Composition of younger Tradl~Hmyo!ite} None BlI.Salt-i"hyolite TrachylUldesite- BlI.Salh-ilyoiite regional ma.gmali3m myolite (2 IlL y. (19-23 MI.)

younger)

HYDROTHERMAL

Fluorite Yes Yes

Garnet Yes Yes

Topaz Yes Yes Yes Yes ?

Cassiterite Yes Trace Yes ? ?

Wolframite Yes Yes Yes Yes Yes

Scheelite No No No No Yes (hornfels)

2.8 4.6 9.7

039 '[ 0.43

35 '1 1

ll5 8.9 8.9

Yet!l Ye$ Yes

Ye;; Ye3 No

No No Ye3

Yes 'I No

Yes Ye$ Yes

I I I !

I <1 rIJ..y.'I I '1 I <1 m.y.

I I I f N "logo Pm; Gnniie I No I ,Olle

I Moon!ain I !

! (1 m.y. younge!) I I ~yoiiie (6 m.)'.

I Tro:hyb.-.lt ~ ! yoonga} ,

I I

. Minoc No ! Yes

I M.inoc ! No I No

Yes Yes Yes

No No No

Trace No Yes

'1 No Yes

'I No Yes

No No No

n. r

Mnrl,.,...,,"

8.9

Yes

Yes

Yes

No

Yes I i

11 I I No I

I I None !

! I

I Yes

I No!

Yes

No

Yes

Yes

Yes

NQ

C-"tnmfh.,

GRANITE-RELATED MOLYBDENUM SYSTEMS

'1

1

1

1

Yes Yes

Yes '1

No Yes

No

1

I 'I I No No

I Syenite '{

7 !

! ! '1

Yes Yes

! ?

'1 1

!

'1 ?

!

I I No I Uncommon , I No

I y~ I !

I Unknown.

I I No I

I I

None I I

I

No

Uncommon

U

Uncommon

No

No

No

Yes

I I ,

I I I

I

I

535

CARTEN ET

200

150

100

.0 70

Z

50

536

Pine Grove and

the term "Cli­Climax and Henderson.

and localities at which tectonic

conditions 'Nere of

A (~

"A

A A 41. A A

-1

Urad-Henderson

100 120 150170 200

--r" t: a.. a.. -.0 a::

intnlsions arc characterized that

500

000

• A A~

~ -, t=':

500 A x

A A

200

100

Urad-Henderson

Sr Pre-Henderson Main Late

A

to th,.;Jse that intr~,;ions associated with

late intrcLSions that were

evolved mation.

RR Carten and L.iN.

with the for-

The absence of such common accessory miner-als as and titanite from Climax and Hender-

fractionated

intrusions at Climax and >

elements among stocks of show both a continuous

variation with age of intrusion and an discontinuous variation at the of forma-

tion of the Henderson Elements that over time include zirconium

The behaviour of these elements can be accounted for

fractionation of monaz ite and zircon Other trace elements

Rb increases from 460 ppm to ppm, from 1 20.5 PpmJ Ta increases

to and Nb increases from 94 ppm. These increases followed the forma­

into which the of was em-

stocks and a se-cond brecciation event was followed intrusion of

Seriate stock al variations cannot fractionation. The occurrence

brecciation and con-with mineralization that dif-

ferentiation and ore concentration may involved

rocks of Crock, Frazier

of trace metals volatile rocks at Climax and Henderson

Both

tuff may have et from local vents of

magma chamber as underlies the Urad­Henderson system.

Additional features of nent to this paper are recorded In Table II. Par-

et al.,

most

GRANITE-REL4.TED MOLYBDENUM SYSTEMS

relative to transitional u",,,,,,,,,,,,,, thick

the absence

are similar in and tectonic char-

aderistics to the Henderson and Climax

This

are associated with met­contain fluorine-rich

a","''',H'-na~c;,,,, and

association with Cave older Urad rln~D0,t-closer in character to transitional

from contains similar con­

ZIrCOnIUm

may represent a Paleozoic transitional aLlCUV~ The correlation of niobium and zirconiurn

concentrations as de-is characteristic of alkaline and re-

of zircon in the magma. The

rather than of zircon units of the Latir volcanic field

and in-

relative concentrations of niobium and zir-conium in transitional may reflect the de-

537

CARTEN ETAL

gree and of interaction of mafic alkali -rich magma or chamber. Mahood ( ment

1 • alumHI0US

200

100

.0 Z

50

50 100

chlorine and a similar pro­

and

o

ME

RS

200 300 500

magmas enrichment trends similar to those of mineralized metaluminous aluminous intrusions

of mafic and felsic magmas has been observed at most The presence of

B 1500

1000

A. !Ill !Ill

t A. !Ill !ill I ;}!l

!ill A. A.~ !ill CP

t ~ JA.A.:A.. -.

500 -- A. :"J'"

E A.

a. A. a. ---.0 a: ~MH

200

100

Questa Mt Pleasant Transit!onal Alkalic

G. Pouliet (written comm., Mount Emmons Stein

Keith and Shanks Redwell Basin (RB D.E. Cameron

magma

538

may have been coincident with the arrival the base of the

fractionation at Pine Grove was less extensive

than at Henderson and CILmax

matic fractionation and for fertile intrusions characteristic of

transitional

shov!s no evidence for caldera or vent formation and

are similar to those of the Climax-Grades in ore zones exceed

and the Most

mineralization. Concentrations of Cu

GHANITE-HEL"'-TED MOLYBDENU:Y'[ SYSTEMS

above and within range from 50 to 500 ppm. not Cu content is ~50-100 ppm in the ore zone of

Lower copper concentrations may resuit from

fractionation. noted that fluids evolved late in the

events arc

0.24% are intrusive breccia that lies above a stock in the intrusive at Goat Hill. Intrusive is not common at Mount and Pine but

magma of and may reflect

Alkalic.

volcanic

intrusions events. In this

that one of the two more resurgence is vesiculation of

caldera formation. The resurgence the formation of intrusive breccias

intrusions enriched In niobium

of the

their strong alkaline these

539

CARTEN

way. In cases, mineralizatioL is related to brecciation and follows this event. At Marble

surface south\vest and are unbrecciated and unmineralized.

eralization succeeded

"'''FDr,"V surrounds the tectonic affiliations in the United States.

the Great

540

correlated with shallow subduction oceanic crust American at

1981). As that middle

volcanic centres southwestern New Mexico and the Great Basin were formed

Basin is related subduction. dude from

rather than a

Ma' calc-alkal inc

a bimodal basalt­used to date the

concluded tha~

basaltic rocks ofTrarIs-Pecos Texas of the tectonic that Cenozoic subduction did

affect volcanism in this area. character of the 38-32

to inheritance of com-

Proterozoic. noted that mafic lavas

to ca. 20

as 1.vithin a true subduction.

simiiar sequence of diachronous events in many of the stnlc­

of the Great Basin and COITtmon middle

younger or basaltic volcanism is

related to extension. Based on evidence of a flat beneath both extended and non-extended ter-

the Great Gans that upper crust overlies a

lower crust-mantle. De-ductile may

in structural do-

faults but that may have been Such a domain is found in and

central Colorado. It is within these less-extended upper crustal domains that most dcnUlll form.

the axis of the Rio Grande alkalic volcanic and subvolcanic rocks in the Trans-Pecos of west Texas vol-canism and caldera 32-38 Ma: and

central Colorado: for Obradovich Mount Aetna

Between areas, the 35-26 ;VIa Sierra Blanca

of of Hialtoo Three Rivers and Cone

The alkalic character of the volcanic-subvolcanic that are associated with

observed, ore-related magma­

tism thickness of continental crclst intersected the

Rio Grande rift tudes Other factors such as zones of crustal weakness and rate of magma flow account for local variations in ofmag-rna observedo To the south, thin crust

alkaline volcanism dominated, Farther north thicker Precambrian

and Sierra alkaline and calc-aLkaline magma­tism are mixedo Still farther Precambrian crust

and alkalic with

GRANITE-RELATED p.l0LYBDENUlVI

necessary to maintain above its soliduso Alkaline

magma chamber

Creek

as in the , Cruistiansen alo, IS an un-

source for these differentiated magmaso In CA!JtJ';,C;U to similar stress and thermal

near-surface ascent of mafic magma is more Smaller volumes of felsic melt are

because of more heat ioss and shorter residence the crusto values are corre-

Other

off Rift and reflect the continuation of young felsic mag­

from the axis to the of the Rio basinHo In a similar manner, younger

in the Great Basin has of the

nature of extensional accounts for the differences in age of the

The transitional at located on the Transverse

, (" , ana ,-,OaK

Ma: belt of characterized at its

sys- northeastern end volcanic and subvolcanic rocks

This viewed as

occurred beneath the Climax and Hendersono The crust behaved more column than thinner crusL

at thicker continental

and acted as ascent of mafic mag­

Because these silicic volcanic centres appear to have lifetimes (::c 1

a ificant volume of mafic rn.agma must be added the to thermal energy

of the Montana alkalic

with an intermediate calc-alkalic

541

CARTENETAL

alkalic rocks uncommon and calc-alkalic and younger bimodal basalt

be a of the younger matism. The distribution northeast to southwest is north distribution of 'te'Ln:;UU,;::'

Rio Grande rift: and calc-alkalic.

In ~r,~'nG" tions of alkali desite and in East Greenland Gleadow

of voluminous tholeiitic

the formation of volcanic and subvolcanic alkalic centres that host dentL"1l this transition corre­

in Trans-Pecos

LH'-'~,HJ<A~Hjl.H in the volcanic centres felsic with

mineralization is sociated with a younger suite

volcanism is not observed.

The alkalic-related

influx of alkaline magma, The

formed in

occurred at levels below the transitional and Climax­

542

in those and

denum a more direct vievv of pro-

5.2 ppm; and in .5 ppm. Price et al. observed that all of the studied

rocks in the Trans-Pecos are char-

the mafic rocks. Interaction of lower crust basalt is in mafic rocks associated with silicic lavas

the 38-32 Ma and The small volume of

in these otherwise alkalic systems were volatile flux of

thermal may account for the

concentrations of niobium and in rocks such as those at Marble - Cave P , LeaK.

The alkalic of East Greenland are simi-1ar to those of the Trans-Pecos Nielsen

concluded that the small rocks intruded into the

crust and contamination with undersaturated mag­ma. The less well-described

are similar in tee-character to the East Greenland

with

Pine Grove. Similar rocks may appear in the root zones of

magma chambers Henderson and Cli-max. Their the local

m the

in tra~sitional and from the differentiation of

and mineralized intrusions processes of

of in magma associated with ore­

Mount Ernmons. Henderson the of

the ultimate source for the derivation magma in mineralized com-

and involves both mantle and crustal compo-Based on detailed and

of the et al. were

Stress

com-

GRANITE-REI~"'TED MOLYBDENUM

extension-related per-in the lower middle crust and preven-

tion of brittle failure of the upper crust. ex­tended upper crust is u.'1iavourable for the formation

stable magma chambers essential to the of

strain in the crust increases rate of ascent of mafic magma.

Volatile flux may dramat-

of upper crustal magma chfullber.

basalt may not mix

and in the formation of Mahood

35-f01d increase between intrusions with and

these elements are also enriched in ore-associated metaluminous magma. The common occurrence of intrusive breccia may reflect the additional involve­ment of a volatile that has low m

This volatile enrich-of metasomatism be­

of alkali elements

LIL and

543

CARTEN ETAL

0,711

0,710

0.708

0,707

0.714

0,712

0,710

0.708 =- 08 '_"- 71 ~- ~~ --- 0,8 1::6 72 - - _~ v

~

56 0,706

0.704 Basalt ,;.

o 500 000

544

Redwell 05122 ~ $

Mt Redwell

::yClimax

0.5128 r--------------------,

1500

A'

0,5126

l:J Z 0.5122

Mt

2000 o 20 30 40 50 60

! I

-'

", I A' ~

70

The ore

of introduction of and in the magma chamber is not

tend­et al.

the introduction of dacitic magma of the chamber into the upper

eVl-

GRANITE RELATED MOLYBDENUM SYSTEM

a1.

were in the chamber and of mafic magma. Their data are the

for the direct of with

and other are intro-

are involved in of concentration. For exam-V~U"UA volatiles may the structure of

the melt and increase the

ueULlHl in transitional and that most of the mag-

and in the or8-

dur-

de-of sources. Keith

nrrm'rlD" a summary of evidence for the deri­from the mamle. Additional

includes the presence of In non-

in the litho­of mantle-derived alka-

line magma and volatiles. ocean-island an uncontaminated of

546

continental

In active additions will both contribute the formation of a

of such events. More critical are the formation volumes and the

tion and time of mafic-derived volatiles In-

troduced into the magma chamber.

tantalum and magma chamber. The interaction of rocks with this enhances the

of formation of a transitional Cli-of this tec­

tonic association can be difficult. Alkalic rocks behind an arc

the cessation

7

(ii U 0 E ·c ::J

,

Rhyodacite

(monzogranite)

Dacite

(granodiorite)

Andesite

Tholeiitic basalt

(J <;: !\! E 0 ill iii cr:.

Adal1l!.C

Yorke-Hardy

Buckingham

Porphyry Cu

Bingham

Nogal Peak

GR?NITE-RELATED MOLYBDENU1\1 SYSTEM

Mrumbjerg

Nordi!

Rhyolite

(ij u o E

CD

, basalt

Calc-Alkaline CI, F, C~, Nb, Zr, Y, Zn, Ta, Rb, Na, K (volatiie flux)

Alkaline

Rate of Percolation

moderate. The volatiles derived magma may centres. At extensional strain or the onset

volcanic centres are 110

tlw cn..LSt an.4 minor volumes Hildreth

547

CARTEN ET

ible-element-enriched volatile

of the alkalic between the two

of and concentration

magma chamber. Low con-

may contain lesser volumes ate magma because of their formation thicker

extended 10\ver and middle crust.

solved in meta luminous

derived magma is essential felsic magma of

or all of these ,-,V",U1JVU<C LH,,;'

the matu­processes that effi­

dis-

4. continental crust is critical to the forma-because

of mafic magma, serves as an extended fractionation contributes volumes of felsic from its lower levels to a

a stable upper level suitable for magma chambers.

5. Extensive fractionation of magTIla essential to the forma­

tion of an alkalic or of introduction of mafic-derived volatiles into

magma chamber. The the volume of

548

for

stable chambers increase the that mafic-derived volatile will be

interact with a

to of

small-volume melts. R

are

magma from extended lower crust

and

in a volcanic centre, formation of the maximum

and to brittle failure of upper Cr'..lst. Under conditions of low moderate rates

total extensional strain of mafic magma and volatiles

of volatiles with evolved magma. Continued e;,.i:ension ultimate-

leads to failure of the upper crust and of mafic less felsic

cr'..lstal chambers that reser-

de-

systems can

Slve processes magma chamber remain to be defined. One of

EaSL Greenland: Nieddelelse:r om

the elu-ore In

and

- Cannivan

In p.

GRANITE·RELATED Ivl0LYBDENUM SYSTEMS

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549

550

ET

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551

CARTEN

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