1989, Granites and Rhyolites

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by  Collected Reprint Series(auth.)

Collected Reprint Series
Granites and Rhyolites
American Geophysical Union
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Copyright 1989 by the American Geophysical Union
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CONTENTS
Chapter 1: Introduction to special issue on Granites and Rhyolites: A commentary for the nonspecialist
Fred Barker .....................................................................................................................................................10131
Chapter 2: A summary of the geology and petrology of the Sierra La Primavera, Jalisco, Mexico
Gail A. Mahood ..............................................................................................................................................10137
Chapter 3: Gradients in silicic magma chambers: Implications for lithospheric magmatism
Wes Hildreth ..................................................................................................................................................10153
Chapter 4: Partitioning of rare earths and other trace elements between sanidine and coexisting
volcanic glass
William P. Leeman and David W. Phelps ..........................................................................................................10193
Chapter 5: Volcanic ash beds: Recorders of Upper Cenozoic silicic pyroclastic volcanism in the
western United States
Glen A. Izett ...................................................................................................................................................10200
Chapter 6: Pleistocene high-silica rhylolites of the Coso Volcanic Field, Inyo County, California
Charles R. Bacon, Ray Macdonald, Robert L. Smith, and Philip A. Baedecker ..................................................10223
Chapter 7: The mineralogy and chemistry of the anorogenic Tertiary silicic volcanics of the SE
Queensland and NE New South Wales, Australia
A. Ewart ..........................................................................................................................................................10242
Chapter 8: Petrogenesis of oceanic andesites
Sven Maaløe and Tom Svane Petersen ............................................................................................................10273
Chapter 9: Gravity and thermal models of the Twin Peaks Silicic Volcanic Center, southwestern Utah
Daniel L. Carrier and David S. Chapman .........................................................................................................10287
Chapter 10: Late Cenozoic volcanism at Twin Peaks, Utah: Geology and Petrology
H. R. Crecraft, W. P. Nash, and S. H. Evans Jr. ..................................................................................................10303
Chapter 11: Geochemistry and petrology of mid-Tertiary ash flow tuffs from the Sierra el Virulento Area,
Eastern Chihuahua, Mexico
Elizabeth J. Moll ..............................................................................................................................................10321
Chapter 12: Three S-type volcanic suites from the Lachlan Fold Belt, southeast Australia
D. Wyborn, B. W. Chappell, and R. M. Johnston ..............................................................................................10335
Chapter 13: Calderas in the Precambrian terrane of the St. Francois Mountains, southeastern Missouri
J. Ronald Sides, M. E. Bickford, R. D. Shuster, and R. L. Nusbaum ....................................................................10349
Chapter 14: Chemical evolution of magmas in the Proterozoic terrane of the St. Francois Mountains,
southeastern Missouri, 1, Field, petrographic, and major element data
M. E. Bickford, J. R. Sides, and R. L. Cullers ......................................................................................................10365
Chapter 15: Chemical evolution of magmas in the Proterozoic terrane of the St. Francois Mountains,
southeastern Missouri, 2, Trace element data
R. L. Cullers, R. J. Koch, and M. E. Bickford ..... ................................................................................................10388
Chapter 16: Contrasting eolution of calc-alkalic volcanic and plutonic rocks of Western Chihuahua,
Mexico
W. C. Bagby, K. L. Cameron, and M. Cameron .................................................................................................10402
Chapter 17: Phase relationships of I-type granite with H O to 35 kilobars: The Dinkey Lakes
2
biotite-granite from the Sierra Nevada Batholith
Charles R. Stern and Peter J. Wyllie .................................................................................................................10412
Chapter 18: The Redskin Granite: Evidence for thermogravitational diffusion in a Precambrian granite
batholith
Steve Ludington ..............................................................................................................................................10423
Chapter 19: Chemistry of rock-forming minerals of the Cretaceous-Paleocene batholith in
southeastern Japan and implications for magma genesis
Gerald K. Czamanske, Shunso Ishihara, and Stevan A. Atkin ...........................................................................10431
Chapter 20: A neodymium and strontium isotopic study of the Mesozoic calc-alkaline granite
batholiths of the Sierra Nevada and Peninsular Ranges, California
Donald J. DePaolo ..........................................................................................................................................10470
Chapter 21: Petrology and geochronology of metamorphosed volcanic rocks in a Middle Cretaceous
volcanic neck in the east-central Sierra Nevada, California
Ronald W. Kistler and Samuel E. Swanson .......................................................................................................10489
Chapter 22: Caledonian plutonism in Britian: A summary
G. C. Brown, J. Cassidy, C. A. Locke, J. A. Plant, and P. R. Simpson ...................................................................10502
Chapter 23: Phase relationships of S-type granite with H to 35 kbar: Muscovite granite from
2
Harney Peak, South Dakota
W. L. Huang and P. J. Wyllie ............................................................................................................................10515
Chapter 24: The New England Batholith, eastern Australia: Geochemical variations in time and space
S. E. Shaw and R. H. Flood ..............................................................................................................................10530
Chapter 25: Manaslu Leucogranite: A collision signature of the Himalaya, a model for its genesis and
emplacement
Patrick Le Fort .................................................................................................................................................10545
Chapter 26: Hybrid granodiorites intruding the accretionary prism, Kodiak, Shumagin, and
Sanak Islands, southwest Alaska
Malcolm Hill, Julie Morris, and Joseph Whelan ...............................................................................................10569
Chapter 27: Petrogenesis of garnet two-mica granites in the Ruby Mountains, Nevada
R. W. Kistler, E. D. Ghent, and J. R. O’Neil .......................................................................................................10591
Chapter 28: Two-mica granites of northeastern Nevada
Donald E. Lee, Ronald W. Kistler, Irving Friedman, and Richard E. Van Loeren .................................................10607
Chapter 29: The Late Archaean Qôrqut Granite Complex of southern west Greenland
Michael Brown, C. R. L. Friend, V. R. McGregor, and W. T. Perkins ...................................................................10617
Chapter 30: Seismic reflections from the basal contacts of batholiths
Heloise B. Lynn, Laura D. Hale, and George A. Thompson ..............................................................................10633
JOURNALO F GEOPHYSICALR ESEARCHV, OL. 86, NO. BII, PAGES1 0131-1013N5O, VEMBER1 0, 1981
Introductiotno SpeciaIls sueo n Granitesa ndR hyolites'
A Commentaryfo r the Nonspecialist
FRED BARKER
U.S. GeologicaSl urveyD, enverF ederalC enterD, enver.C olorado8 0225
WHY GRANITES AND RHYOLITES? containing2 5% of other mineralsn eed containo nly 15%
The siliceousp, otassicig neousr ockst hat containm ore than quartzt o fall into the granitef ield( Figure1 ). This petrogra-
phicd efinitiono f granitet husp recludeesx actc hemicadl efini-
~69%S iO2a ndt ypically3 .5-5.5%K 20--the graniteasn dr hy-
tions.
olites--nowf ollowb asaltsin theiri mportancteo earths cien-
tists.T hough the 1970'sc ouldb estb e termeda 'Decadeo f Ba- Rhyolitesp osea differenpt roblemin terminologbye cause
salts'[ Hart andA llegre,1 980],a n increasingn umbero f earth mosta rep artlyt o largelyg lassayn ds oc annobt ec lassifiebdy
scientistsa re now turningt heir attentiont o the more siliceous proportionso f mineral phases.A chemicalc lassificationis
rocksT. he presenct ollectioonf paperso n granitesa nd rhyo- necessarAy. usefuly et simpleo ne,s hownh erea sF igure2 , is
liteisn cludgeeso logaicnadgl eophysfiiecladslt udipesh,y sicabla seodn S iOa2n dK 20a bundanacnedws asp roposbeyd
andc hemiceaxlp erimensttuald ieasn,a lysoifsb othro ckasn d. Pecceriallnod T aylo[r1 976a]n dm odifiebdyE war[t1 979A].s
the constituenmt ineralsf or major and minor elementsa nd ther eaderw ouldju dge,t hec orrespondenocf ec hemicalldye -
variousis otopicra tios,a nd consideratioonf pertinenpt late finedr hyolitea ndo f granited efinedb y proportionosf miner-
tectonicp rocesseasn d environmentPs.r ocesseWsh ichg ener- als is haphazard.C lassificationo f theser ocksr emainsa minor
ate granitic-rhyolitmice ltsa nd mechanismosf emplacement problem.
of thesem eltsi n the upperc rusto r at the earth'ss urfacea re of Many petrologisatsn d geochemisftusr thers eparateg ran-
ites, rhyolitesa nd relatedr ocksi nto the followingt hree
paramounitn teresht ere.T his speciails suei s a sampleo f
modernr esearchan d conceptasb outg ranitesa nd rhyolites. groupsb y molar proportionso f severalm ajor constituents
[Shand, 1951]:
NOMENCLATURE
peraluminous:A 120>3 Na20+ K20 + CaO
Becausteh e definitionso f granitea nd rhyoliteh ave been
metaluminous: Na(cid:127)O + K20 < AI(cid:127)O3< Na(cid:127)O + K(cid:127)O
changedr ecently,t erminologyi s discussedfi rst.
+ CaO
AlmOsat ll granitesa re intrusivea nd mostr hyolitesa re ex-
peralkaline: AI(cid:127)O(cid:127) < Na20 + K(cid:127)O
trusiveH. owevera, classificatitohna ti s independeonft mode
of occurrencies preferreda nd so granitei s definedp etro-
Two other classifications chemeso f igneousr ock suitesd e-
graphicallyI.t is a whollyc rystallinero ckw hosem ajor min-
servem ention. The CIPW rock norm classification[C rosse t
eral constituentasr e 1-25 mm in averaged imension(f iner-
al., 1902;J ohannsen1, 939] is basedo n the calculation( by
grainedv arietiesa re termedf elsiteo r aplite;c oatsetv arieties
weightp roportions)o f a completes et of hypotheticanl orma-
arep egmatitea) ndi t containse ssentiaall kalif eldsparq, uartz,
tive 'minerals' that include quartz (SiOn), orthoclase
andp lagiøclasCeo. mmonliyt alsoc ontainosn eo r morev ari-
(KA1Si(cid:127)Os)a, lbite (NaAISi(cid:127)Os),a northite( CaAl(cid:127)Si(cid:127)Os),c o-
etal mineralss uch as biotite, hornblende,m uscovite,s odic,
rundum (AI20(cid:127)), enstatite( MgSiO3), and others.T he CIPW
amphiboleo, r othersa nd accessorpyh ases(cid:127)u ch(cid:127) magnetite,
classificatiogne nerallyi s bettera ppliedt o volatile-poorb asal-
ilmenite, apatite, zircon, allanitc, garnet, or others.T he his-
tic systems[s eeM orse, 1980]t han to mostg raniteo r rhyolite
tory of rockc lassificationdse,f initionos f a multitudeo f pet-
suites,b ut it has provenv ery usefult o experimentapl etrolo-
rographicte rms,a nd a now little-usedb ut internallyc onsis-
gistsi n describingr elativelys implea rtificial systemss, ucha s
tent systemo f classificatioanr e given by Johannsen[1 939,
the classici nvestigationb y Tuttle and Bowen[ 1958] of the
1932, 1937, 1938]. Many modem workers,h owever,u se the
granite-H(cid:127)Os ystema t low to moderatew ater pressuresS. ome
more recent International Union of Geological Sciences
workersa lso use the CIPW schemet o describeg raniteso r
(IUGS) classification[S treckeisen1, 976].T he IUGS defini-
rhyolitesa s corundum-normativoer diopside-normativ(ei. e.,
tion of granite and similar holocrystallineS, iO2-saturated
showingc orundumo r diopsidea s a calculatedn ormative
rocksi s showni n Figure 1.
'mineral').
The IUGS classificatioanl lowsg ranitet o containa s much
Another notable descriptives chemei s that of Peacock
as9 0%o f mineralso thert hanq uartza ndf eldsparsF.e w gran-
[1931],w hich is usedt o classifys uiteso f igneousr ockst hat
ites, though, contain more than about 20% of other minerals.
rangef rom mafico r intermediatteo siliceoucso mpositions.
The readers houldk eepi n mindt hat in thiss chemeth e pro-
Plotso f Na(cid:127)O + K(cid:127)O versusS iO(cid:127) and of CaO versusS iO(cid:127) are
poRionso f the three definingm ineralsa re relativea nd that
superposed.T he SiO2 content at which the two lines intersect
their absolutec ontentisn a giveng ranitev ary inverselyw ith
is termedt he alkali-limein dex( ALI). Peacockd istinguishes
total contento f other,n onessenti(avl arietala nd accessory)
four groupso f rock serieso n this index: ALI< 51 --'alkali½
mineralsT. husa granitec ompriseodf onlyt he two feldspars
(alkaline),5 1 <ALI < 56 alkali-calcic5, 6 <ALI < 61 = calc-
and quartzm ustc ontaina t least2 0%q uartz,w hereasa granite
alkalic (ca(cid:127)lc-alkalinea),n d ALI> 61 calcic.P eacock'sc lassifi-
cationis morea pplicablteo rocks uitesfo rmedb y closed-sys-
Thisp apeirs nots ubjectot U.S.c opyrighPtu. blisheind 1981b y tem crystal-liquifdra ctionatioonf a basaltico r andesiticp a-
theA mericaGne ophysiUcanli on. rentaml agmaT. het erms'c alc-alkalinaen' d' alkalines' tilla re
Paper number IBI015.
10132 BARKER: INTRODUCTION TO GRANITES AND RHYOLITES
Quartz cussede arly in this century.I t wasa pproachedfr om two very
different points of view. One considered the Precambrian
crystallinec omplexeso f granitic to tonalitic gneissesm, ica
schists,a mphobolites, and other intensely deformed and
metamorphosedro cksi ntruded by siliceousm agmasr anging
from quartz diorite to granite. Sealerholm[1 907] gave us a
classice xample of such a complex in the mid-Proterozoic
6O
rocks of southern Finland and coined the word 'anatexis' for
ALKALI-FELDSPAR the partial to complete( ?) meltingo f a siliceousg neissto pro-
GRA E
duceg raniticm agma.T he seconda pproacht o partial melting
involved the geosynclineo r fold belt. Loewinson-Lessing
[1911] describedf olding of a 10- to 15-kin-thick filling of a
large sedimentaryb asin wherein sufficientc rustalt hickening
20/ / ! \ \ (cid:127),.QUARTZ occurredt hat the lower parts of the basin reached melting
temperaturesF. usiono f shale,s andstonea, nd other sediments
producedg ranitic magmas.T hese rise diapirically or stope
their way into the overlyingr ocks.
10 35 65 90
Alkalif eldspar Plagioclase Modem studieso f crustalm eltingu set he pressure-temper-
Fig;. 1. Ternaryd iag;ramin volumetricp roportionsa fter $treckei- ature constraintse stablishedb y experimentalp etrology.H art
sen [1976] showing;c ompositionalf ields of g;ranit½a nd other rock and (cid:127)lllegre [1980]s ummarizem uchr ecentw ork, emphasizing
types.P roportionso f other minerals,n ot shownh ere, may rangef rom the use of O, St, Nd, and Pb isotopesi n evaluating both
0 to 90% of the rock. sourcreo cksa ndp rocessePsa.r tiaml eltingin thisi ssueis dis-
cussedb y Bickford et al., Cullerse t al., Czamanskee t al., Hill
widely used.T hese termsa nd othersa re usedi n the extended et al., Le Fort, Shaw, and Flood, and Wyborn et al.
chemical classificationsin the papers of Irvine and Baragar Australianw orkersl ed by Chappella nd White [1974] have
[1971] and Miyashiro [1974]. given a large impetust o considerationo f partial melting proc-
essesIn. the Lachianfo ldb elt,s outheasteAruns traliath, ey
GENERATION OF GRANITIC-RHYOLITIC MAGMAS distinguisht wo major typeso f graniteb y sourcem aterial---S
Granitic-rhyolitic magmas typically are generated in re- type and I type. The S type is derivedf rom sedimentaryr ocks
sponset o thermal and tectonic processesin the mantle. To (actuallym etamorphosedsh aleo r pelitic schistf or all Austra-
date no one has demonstratedt hat suchm agmasm ay form in lian S type granites),a nd the I type granitesa re derived from
the mantle. Indeed, much experimental and geochemical igneourso cksth atm ayr angef romg abbroitco graniticc om-
work indicates that such siliceousl iquids cannot originate positions.B oth types are intruded as magma or mush con-
there (e.g., Stern and Wyllie, Huang and Wyllie, this issue). sistingo f variousp roportionso f melt and residuum( or 'res-
Therefore,s uchm agmasm ust be generatedin the crust,a l- tite'). S type granites are biotite-muscovite-bearing and
though somem ay contain material of immediate mantle deri- chemicallya re stronglyp eraluminousI. types,b y contrast,a re
vation (see, e.g., DePaolo, this issue). Furthermore, though metaluminous,b iotite or biotite-hornblendeg ranites.T he S
rhyolite doeso ccuri n oceanice nvironments,s ucha s the low- type designationa pplies to similar granitesi n other parts of
K rhyolites of some island arcs and the normal to alkaline the world (see,e .g., Kistler et al., Le Fort, Lee et al., this is-
rhyolites located near some oceanic spreadingc enters ($i- sue), typically with only minor changes in Chappell and
gurdsson[1 977]m akesa n excellentc asef or generationo f Ice- White's [1974] original definition. However, there are other,
landic rhyolite by partial melting of plagiograniteo f the oce- far more voluminousg raniteso f sedimentaryo rigin,m ostlyi n
anic crust)--they are minisculei n amount as comparedt o the the Precambrians hieldst, hat do not fit Chappell and White's
granitesa nd rhyoliteso f the continents.T he latter occur in classificationT. hese granitesa re derived from graywackes--
environmentsr angingf rom accretionaryp rismsa t continental
maxginsto continentaml arginm agmatica rcsa nd fold beltst o 6 i
extensionalr egionsa nd hotspotsi n continentali nteriors.
The origin of granite and rhyolite has been debatedf or the
last two centuries.T hree general processesh ave been sug-
gested,a s showni n Table 1. These are: (1) partial melting of (BANAKITE)
HIGH-K RHYOLITE
pre-existings olid rocks;( 2) closed-systemcr ystal-liquidf rac-
tionation;a nd (3) coupledf ractionation-meltingo, r open-sys- HIGH-K DACITE
-- HIGH-K
tem fractionationi n which a mafic or intermediatel iquid may
ANDESITE
extensivelyr eactw ith, or incorporatet, he immediatew allrocks RHYOLITE
DACITE
or roof. A subsidiaryp rocess(cid:127)liquid state differentiation--
(talc-alkaline)
may operatet o produces ignificantc ompositionalg radientsi n ANDESITE
many magma chambers( Hildreth, Bacon et al., Mahood, this
LOW-K RHYOLITE
issue). L'(cid:127)--KA NDESITEL'O W-K DACITE
I I I I
63 65 69 70 75
Partial Melting SiO2 (WEIGHTP ERCENT)
The concepto f partial to completem elting of crustalr ocks Fig. 2. Classificatioonf andesited, acite,a nd rhyohteb y K20 and
to produce granitic-rhyoliticm agmas was extensivelyd is- SiO2c ontents[ afterE wart,
BARKER: INTRODUCTION TO GRANITES AND RHYOLITES 10133
TABLE 1. A HypotheticalS chemef or the Generationo f Granitic-RhyoliticM agmas
General Process
PartialM elting Crystal-LiquidF ractionation CombinedM elting-Fractionation
Geologicael nvironment Fold belts,a ccretionarpyr isms(?), Midoceanr idgeso, ceanica nd Continentaml arginm agmatica rcs,
Precambriagnr eenstonbee lts, continentainl traplatem agmatism continentarilf. ts,c ontinental
old metamorphica nd plutohie or hotspotsis, landa rcs,o ceanic hotspotslo, callyi n accretionary
complexes. and continentarli fts,o ther prismsp, robablyi n other
environments. environments.
Source materials Graywackep, elite( S type liquids), Basalticl iquid of olivine- or Marie melt plus crustalm elt less
volcanicr ocks,m etamorphic quartz-tholeiitict ype, or precipitatedl iquidusp hasesa nd
complexesp, lutonicc omplexes. andesiticli quid in some lessp recipitatedre fractory
environments. crustal material; crustal melt
from any crustalr ock containing
K(cid:127)_O,N a(cid:127)_O,S iOn(_o ther
componentsa re incidental).
Heat source Depressiono f sourcer ocksi nto (Self-contained.) Heats of crystallizationo f magmatic
higher geotherms. (liquidus) phaseso f mantle-
derivedm arie magma, locally (or
commonly?)s uperheato f mantle-
derivedm agma,c rustalr ocks
initially about 200ø-600øC.
Derivation of liquid Partial melting of sourcer ock and Separationo f olivine, pyroxenes, Mantle-derivedm ariem agmap ools
then (1) separationo f liquid plagioclasea, nd other phases in crusta t deep to shallowl evels
from refractoryr esidueo r (2) from increasinglys iliceous and (1) while precipitating
ascento f liquid-residuem ush. liquid: e.g., 100p artsb asaltic liquidusp hasesr eactsd irectly
liquid yield 8-10 partsg ranitic with crustalr ocks,p artly
liquid. meltinga nd incorporatingt hem,
partly reactingw ith and precipi-
tating their refractoryp arts,o r
(2) simplyh eatinga nd melti(cid:127)
nearbyc rustalr ocks,o r (3)
mixing of liquidsp roducedi n
1 and2.
Types of rocksp roduced S type from pelite only;t rondhjemite Granophyric-texturedh, igh Fe/Mg Metaluminou(asp proachinpger a-l
from metabasalt;m inimum melt to typesc ommon;s yenitic-trachytic kaline) and peralkalinet ypeso f
calc-alkaline-trendty pe from typesa lso common. high Fe?Mg, low H(cid:127)_Oa ctivity
other sources. from 1 and 3 above;2 above
producest ypesa s under 'partial
melting' at left.
See text for details and references.
ofteno f volcanogenitey pe(cid:127)and soy ield partial meltso f met- quartz in diabased ikesa nd sills;a nd the sodar hyolitest hat
aluminousto mildlyp eraluminoucsh aracterA. n excellenet x- are foundw ith trachytea nd otherm oderatelya lkalinel avas
amplei s givenb y Arth and Hanson[ 1975]i n their chemical of somen ear-ridgeo ceanici slands( e.g., as at EasterI sland
modellingo f the late ArcheanV ermiliona nd Giants Range [Bakere t al., 1974]).M any yearsa go Grout[ 1926]c alculated
Graniteos f northeasteMrni nnesotaT.h eI typed esignatioonf thata moderatelpyo tassibca sal(tK 20 -- 1.52%c) ouldy iedl a
Chappella nd White, howeverh, asn ot met with similarw ide- maximumo f about 10% graniteb y crystal-liquidf ractiona-
spreada pplication( seed iscussionin Czamanskee t al., this is- tion.
sue). Controversya risesa s to the scaleo f the fractionationo f ba-
salt to granite and rhyolite. Can granite stocksa nd batholiths
Closed-SyCsrtyesmta l-LiFqruaicdt ionation severtaolm ancyu bikci lometienr vso lumoer c ontinental
The secondm ajor modeo f origino f siliceousm agmasis by rhyolitica sh flowso f similarv olumef orm by the closed-sys-
crystal-liquidf ractionationo r differentiationin which the tem fractionationo f basalticli quid?B owen[ 1922a,1 928]p ro-
magmad oesn ot interactw ith any of the enclosingr ockso r poseda 'reactions erieso' f mineralst hat successivelcyr ystal-
fluids.I n this processm ineralst hat are lesss iliceousth an the lizeda nd separatedfr om a primaryo r mantle-derivedb asaltic
liquid crystallizea nd eithers ettleo r float out of the magma liquid. This seriesc ommencewd ith olivinea nd calcicp lagio-
and therebyc auset he remainingl iquid to becomem ore si- ½lasea nd terminatedw ith potash feldspar,m uscovitea nd
liceousT. his mechanismw asf irsts uggestebdy Darwin [1851] quartz,a nd led to productiono f calc-alkalineg ranitic-rhyo-
and has sinceb eena ppliede xtensivelyto many crystal-liquid litic liquid. Bowen[ 1948]f urther suggestetdh at mostg ranites
systemso f marie to intermediatec ompositionT. here is little were producedb y suchf ractionationa nd that assimilationo f
doubtt hat basalticli quidsf ractionateto yield granitic½ ompo- crustalr ocksb y the liquid waso f minore xtent.B owen'sin flu-
sitionse: xamplesin cludet he interstitiarlh yoliticg lasse(sS iO2 encew asp ervasivea nd a generationo f geologists(cid:127)excepfot r
75.0-75.9%,K 20 5.5-6.0%)f ormedb y crystallizationo f basalt the quasi-rationalg ranitizersw ho contendedt hat fluids or
(SiO25 0-51%, K20 -- 0.5-0.6%)o f the Makaopuhi and Alae cloudso f ions formed granites(cid:127)tacitly agreedw ith him. To
lava lakes,H awaii [Wright and Okamura, 1977];t he world- date, however,n o one has demonstratedth at any graniteo r
wide occurrenceo f a few percento f scatteredd ikeletsa nd rhyolitem asso f severacl ubick ilometerso r largerh as formed
pods of granophyreo r intergrowthso f alkali feldspara nd by simplef ractionationT. here are severapl roblemsp osed
10134 BARKER: INTRODUCTION TO GRANITES AND RHYOLITES
fractionationo n sucha scalet hat have not yet been fully re- type (e.g., the rapakivi massifso f southernF inland, and the
solved:o ne involvest he small yield of siliceousl iquid from Pikes Peak batholith) originally may have graded upward
basalticl iquid and the mechanicso f its aggregationin to large from deep anorthosite-gabbroc omplexest o syenite-granite
magmab odies[ Holmes,1 936].A nother involvesm aintaining complexest o rapakivitic batholithst o overlying subvolcanic-
reservoirso f basaltic liquid in the crust of sutiicients ize to volcanic ring complexes( such as the Younger Granites and
generateg ranitic batholiths 2 to 8 km thick and 5000-10,000 associatedrh yolitesa nd other rockso f Nigeria and nearby re-
km2 in area,s ucha st he PikesP eakb atholitha nd the Wiborg gions), and at the surfacet o largely bimodal basalt-rhyolite
granite massifo f southernF inland and RussianK arelia. The fields such as Yellowstone.
intermediatet o ultramaficr esidualm aterial from sucha large Taylor [1980] has consideredth e role of oxygena nd stron-
fractionation event would be of 25- to 100-km aggregate tium isotopes in coupled fractionation-melting. DePaolo
thicknessI.f suchr esiduae xisted,h ave they all sunkb ack into [1981] has derived equationsd escribingt he behavior of trace
the mantle?L astly,i sotopics tudieso f someg raniticr ocksl ong elements and isotopesi n such systems,a nd in this issueh e
thought to be generatedb y simple fractionationi ndicate that considerst he origin of the Sierra Nevada and Peninsular
they containm oderatet o large fractionso f wallrockm aterial. Ranges batholithsi n this context.
A prominent example is the late-stageg ranophyreo f the Many aspectso f coupledf ractionation-meltingn eed eluci-
Skaergard intrusion, East Greenland [Leemah and Dasch, dation. Especially,d o we have a completer angeo f interaction
19781. from an endmemberi n which the thermal sourcem agmas im-
ply suppliest he heat of partial melting but doesn ot mix with
CoupledF ractionation-Melting
or incorporatec rustalm aterial to situationsi n which the ther-
The third major mode of origin of granite and rhyolite is a mal sourcem agma incorporatesv ery high fractionso f crustal
coupling or combinationo f crystal-liquidf ractionationa nd melt?
melting of the enclosingc rustalr ocks (Table 1). As long ago
FUTURE WORK
as 1914, Daly speculatedt hat superheatedb asaltic liquid
might assimilatel arge fractionso f crustalr ocks( his 'abyssal As seeni n this issue,t he currently active areaso f research
assimilation').I n notable papers a few years later, Bowen on granitesa nd rhyolitesa re in the disciplineso f geochemistry
[1922b, 1928] set forth the principlesc ontrollingr eaction of and petrology, and in volcanic processesW. e need further
magmasw ith inclusions.I n particular, he pointed out that studieso n the magmatics ourcer egionsi n the lower and inter-
heats of crystallizationo f liquidus minerals--rather than su- mediate crust.T hesew ould include modelling studieso n ther-
perheat-would be the major energys ourcef or the melting of mal aspectso f melting,s ucha s that of Yoder[ 1980];t heoreti-
siliceous to intermediate crustal inclusions in basaltic or ande- cal considerationo f all possibles ource rocks, e.g., that of
sitic liquids. Thus much of the heat originally suppliedb y a pelitesb y Grant [1973]a nd Thompsona nd Algor [1977];s tudy
mantle reservoiri n heating ultramafic mantle material to pro- of geothermometersa nd geobarometerso f xenoliths to give
duce basalt is transferredb y injection of that basalticl iquid direct information on conditionso f magma generation,l ike
into the crusta nd it becomesa vailable for the melting of crus- that of Wyborn et al. in this issue;g eophysicasl tudiesth at will
tal rocks.B owen,h owever,d id not assigna major role to this give us physicali nformation on regionsw here magnaasa re
mechanismf or the productiono f granitic-rhyoliticli quids, as generated,s ucha s that by the COCORP projecto f a magma
mentioned above. Holmes, however, did this in a notable but body in the Rio Grande rift, New Mexico (seeR eilingere t al.
neglectedp aper of 1931, using as examplest he largely bi- [1980] for references)a; nd especiallys tudiesr elating tecton-
modal gabbroica nd dioritic-graniticH ebredeans ubvolcanic ism to the chemicals tyle of magmatism.
complexeso f northwesternS cotland. Wager et al. [1965] re-
vived Holmes' model for the shallow graniteso f the Western
Red Hills complex, Skye. Strontium isotopicr atios indicate AcknowledgmentsI. extend my thanks to many people for their
that these granites,i ndeed, were derived largely from Pre- guidance and cooperationw ith this special issue.R obert Coleman
cambrian basementr ocks [Moorbath and Bell, 1965]. suggesteJdG R-Red as its vehicle,p ointingo ut JGR's rare combina-
tion of worldwide distribution and modest cost. Allan Cox enthusias-
The Hebredeang raniteb odiesa re roughly 10-100 km3 in
tically backedC oleman'ss uggestionE.d itor ThomasA hrensg uided
volume. Seriousa pplication of mantle-derived,b asaltich eat severala spectso f the reviewp rocessw ith care and goodj udgment
sourcest o generationo f larger batholithsi nclude: (1) Har- and wash elpfuli n manyo therw ays.R uth Ridenourg avee xemplary
graves'[ 1962] and Ashwals'[ 1978] discussiono f anorthositic editoriala ssistancaen d her expeditioush andlingo f manuscriptasn d
reviewsm ade our presentp ublicationd ate possibleL. astly,t he more
gabbroa nd the associatedg ranite and syeniteo f the Adiron-
than 50 earth scientistsw ho reviewedt he papersh erein deserveo ur
dack massif;( 2) Presnalla nd Bateman's[ 1973] and Brown's
thanks for their effectivec ommentary.
[1973]c onclusionth at andesitico r basalticl iquid generateda t
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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 86, NO. BII, PAGES 10137-10152, NOVEMBER 10, 1981
A Summaryo f the Geology and Petrologyo f the Sierra La Primavera,
Jalisco, Mexico
GAIL A. MAHOOD
Departmento f GeologyS, choolo f Earth SciencesS, tanfordU niversityS, tanford,C alifornia9 4305
The SierraL a Primavera,n ear Guadalajara,M exico, is a Late Pleistocenerh yolitic centerc onsistingo f
lava flows and domes,a sh flow tuff, air fall pumice, and calderal ake sedimentsA. ll eruptive units are
high-silicar hyolites,b ut systematicc ompositionadl ifferencesc orrelatew ith age and eruptivem ode. The
earliestl avas erupteda pproximately1 45,000y earsa go and were followed approximately9 5,000 years
agob y the eruptiono f about2 0 kra3 of magmaa s ashf lowst hat form the Tala Tuff. The Tala Tuff is
zonedf rom a mildly peralkalinef irst-eruptedp ortion enrichedi n Na, Rb, Cs, CI, F, Zn, Y, Zr, Nb, Sb,
HREE, Hf, Ta, Pb, Th, and U to a metaluminousla st-eruptedp art enrichedi n K, LREE, Sc, and Ti; AI,
Ca, Mg, Mn, Fe, and Eu are constantw ithin analyticale rrors.C ollapseo f the roof zone of the magma
chamberl ed to the formation of a shallow 1l -km-diameter calderai n which lake sedimentsb egant o col-
lect. The earliestp ostcalderala va, the south-centradl ome, is nearly identicalt o the last-eruptedp ortion
of the Tala Tuff, whereast he slightly younger north-central dome is chemically transitional from the
south-centradl omet o later, more marie,r ing domes.T his sequenceo f ashf low tuff and domesr epresents
the tapping of progressivelyd eeperl evels of a zoned magma chamber9 5,000 + 5,000 years ago. Sedi-
mentationc ontinueda nd a period of volcanicq uiescencwe asm arkedb y the depositiono f some3 0 m of
fine-graineda shys edimentsA. pproximately7 5,000y earsa go a new group of ring domese rupteda t the
southernm argino f the l(cid:127)tke. Thesed omesa re lappedb y only 10-20 m of sedimentsa s uplift resulting
from renewedi nsurgenceo f magma broughta n end to the lake. This uplift culminatedi n the eruption,
beginninga pproximately6 0,000y earsa go, of aphyricl avasa long a southerna rc. The youngesto f these
lavase rupteda pproximately3 0,000y earsa go. The lavast hat erupted7 5,000,6 0,000,a nd 30,000 years
agob ecamed ecteasingplye ralkalinea ndp rogressiveelyn richedo nly in Si, Rb, Cs,a ndp ossiblyU with
time. They represents uccessiveer uption of the uppermostm agma in the postcalderam agma chamber.
Eruptive units of La Primaveraa re either aphyrico r containu p to 15%p henocrystso f sodics anidine_ >
quartz >> ferrohedenbergit>e fayalite > ilmenite + titanomagnetiteM. ajor elementc ompositionso f san-
idine, clinopyroxene,a nd fayalite phenocrystsv ary only slightly betweene ruptive groups,b ut the con-
centrationso f many tracee lementsc hangeb y factorso f 5-10. This is reflectedi n phenocryst/glasps arti-
tion coefficienttsh at differ by factorso f up to 20 betweens uccessiveleyr uptedu nits. Becauseth e major
elemenct ompositioonfs t hep henocrysatns dt hep ressurtee, mperaturaen, df o2o f them agmaws eree s-
sentiallyc onstant,t he large variationsi n partitioningb ehaviora re thoughtt o result from small changes
in bulk compositiono f the melt. Crystal settlinga nd incrementalp artial melting are by themselvesin -
capable of producinge ither the chemicalg radientsw ithin the Tala Tuff magma chamber or the trends
with time in the post-95,000-yearla vas. Rather, diffusionalp rocessesin the silicatel iquid are thought to
have been the dominant differentiation mechanisms. The zonation in the Tala Tuff is attributed to trans-
port of trace metalsa s volatile complexesw ithin a thermal and gravitationalg radient in a volatile-rich
but water-undersaturatemd agma.T he evolutiono f the postcalderala vasw ith time is thoughtt o involve
the diffusivee migrationo f tracee lementsfr om a relativelyd ry magmaa s a decreasingp roportiono f net-
work modifiersa nd/or a decreasingc oncentrationo f complexingl igandsp rogressivelyre ducedo ctahe-
dral site availability in the silicate melt.
INTRODUCTION pose of this study of the Sierra La Primavera, therefore,h as
been to trace the chemical evolution of a rhyolit(cid:127)ic complex
One way to understandt he differentiationp rocesseso per-
through time, interpretingi t as the periodic samplingo f an
ating in high-level magma chamberst hat solidify as granitic
evolving magma chamber.
plutonsi s to studym aterial eruptedf rom suchc hambers.A sh
To determinet he eruptive history,t he Sierra La Primavera,
flow tuffs are rapidly quenched voluminous samples of
locatedo n the westerno utskirtso f Guadalajara, Jalisco,M ex-
magma chambers;a s sucht hey have made possiblet he char-
ico (Figure 1), was mapped at a scaleo f 1'25,000. Eruptive
acterizationo f chemicala nd thermal gradientsw ithin the up-
units were classifiedi nto groups based on stratigraphic rel(cid:127)a-
per portionso f silicicm agmac hambersju st prior to eruption
tions, and the eruptive sequencew as calibrated with over 50
[Lipman et al., 1966; Smith and Bailey, 1966; Hildreth, 1977,
K-At dates performed at University of California, Berkeley
1979; Smith, 1979; Ritchie, 1979; Hildreth et al., 1980]. Com-
[Mahood, 1980a]. This paper summarizest he geological and
plementaryt o studieso f ash flow tuffs, which are inverted rec-
chemical evolution of the Primavera system;t he geology of
ords of magma chambersa t singlep oints in time, is the infor-
the Sierra La Primavera is describedi n more detail by Ma-
mation contained in a sequenceo f eruptive units, which
hood [1980a, 1980b],w hereast he petrologyi s discussedm ore
record the chemicale volution of the upper portionso f a silicic
fully by Mahood [1980a, 1981].
magma chamber through time. Making the reasonablea s-
sumptionth at a lavaf lowo r ashf lowt apst he mostd ifferenti- REGIONAL SETTING
ated uppermostm agma in the systema t a particular moment,
The Sierra La Primavera lies at the intersection of the two
a sequenceo f eruptive units providesp rogressr eportso n the
major Cenozoicv olcanicp rovinceso f Mexico (Figure 1). Its
differentiationm echanismso peratinga t depth. The main put-
mildly peralkaliner ockss tandi n marked chemicalc ontrastt o
Copyright¸ 1981 by the AmericanG eophysicaUl nion. both the andesitic stratovolcanoes and basaltic cinder cones
Paper number IB0529.
0148-0227/81/001B-0529501.00