geochemical constraints on the petrogenesis of the - terrapub

Geochemical Journal, Vol. 37, pp. 603 to 625, 2003

603

*Corresponding author (e-mail: [email protected])

Geochemical constraints on the petrogenesis ofthe Middle Miaoershan granitoids, South China

M.-Z. MIN,1* X.-Z. LUO,2 X.-G. LI,3 Z. YANG3 and L.-Y. ZHAI3

1Department of Earth Sciences, State Key Laboratory of Mineral Deposit Research, Nanjing University,Nanjing 210093, P.R. China;

Center of Material Analyses, Nanjing University, Nanjing 210093, P.R. China2Department of Environmental Engineering, Nanjing University, Nanjing 210093, P.R. China

3310 Geological Party, Central-South China Uranium Geology Bureau, Guangxi 541307, P.R. China

(Received January 28, 2002; Accepted June 2, 2003)

The Middle Miaoershan batholith in South China is one of the best examples of a composite graniticcomplex, comprising coarse-grained, porphyritic, biotite monzogranites, quartz monzonites, and medium-and fine-grained two-mica granites, formed respectively during the Caledonian, Hercynian, Indosinianand Yanshanian tectonic activity. This is confirmed by radiometric (Rb-Sr, U-Pb, and K-Ar) isotopic agesof 368, 296, 214, and 120 Ma, respectively. The majority of the granitic rocks are peraluminous withaluminum saturation indices [ASI, molar Al2O3/(CaO + Na2O + K2O)] of 1.05–1.48 and high 87Sr/86Srinitial ratios, i.e., (87Sr/86Sr)i (0.71012–0.72935). Chondrite-normalized (N) rare earth element (REE) abun-dance patterns for the granitoids are heterogeneous with (La/Yb)N between 5.75 and 14.38, variably nega-tive Eu anomalies (Eu/Eu* = 0.24–0.80), and overall patterns similar to those of the host metasedimentaryrocks. With respect to the old intrusive unit (CMG), the three young intrusive units (HXG, IDG and YG)possess generally lower ∑REE and Zr abundances, and larger negative Eu anomalies, indicating that theymay be partially derived from re-melting of the CMG; plagioclase, zircon, and LREE-bearing accessoryphases remained in the source during this partial re-melting of the CMG. δ18O values for all of the granitoidsare relatively uniform at 10.12 to 12.99, with a mean of 11.36. The lead isotopes for K-feldspar from thegranitoids have a limited variation both within and between massifs, and all of the sample points fall nearthe upper crust growth curve in a 207Pb/204Pb vs. 206Pb/204Pb plot, indicating derivation from supracrustalsources for rock lead and rock-forming material.

The Caledonian Miaoershan granitoids (CMG), however, are proposed to have had a supracrustalmetasedimentary source mixed with a minor component of infracrustal derivation, resulting in a relativelylow initial (87Sr/86Sr)i value (0.70761) and ASI (<1.0). The presence of inherited zircon as ancient corerelicts within young magmatic zircons in the CMG shows that partial melting of crustal material, domi-nantly of metasedimentary origin, combined with re-melting of the granitoids formed by previous partialmelting episodes, may be the dominant processes in the genesis of the granitoids. Limited variations oftheir chemical compositions and Sr, Pb isotopes among different massifs are probably related to the prov-enance of their source materials.

Guangxi to Hunan Province, South China (Fig. 1).The Middle Miaoershan granitoids (MMG) con-tain an important economic uranium ore district(Min et al., 1999). The uranium-rich Douzhashangranitoids, which are one of four main intrusiveunits within the Middle Miaoershan granitic com-

INTRODUCTION

The Middle Miaoershan granitic complex (329km2) (25°40 ′00″–25°55 ′00″ N, 110°20 ′00″–110°32′00″ E) is part of the 1633 km2 Miaoershancomposite granitic batholith, extending from

604 M.-Z. Min et al.

plex, were investigated as part of a regional ura-nium prospecting program organized by the Geo-logical Bureau of China National Nuclear Corpo-ration. The granitoids in the Middle Miaoershanarea are relatively well known from a geologicalpoint of view, due to the tight relationships be-tween the granitoids and several mineralizations(U, W, fluorite) of economic importance, and nu-merous studies of geochemistry, petrography andgeochronology that are cited below. Thepetrogeneses of the granitoids, however, are poorlyunderstood (e.g., Liu, 1986, 1988; Sayilin, 1990;Xu, 1994).

The aim of this work is to constrain the possi-ble petrogenetic models that concern the MMGbased on geochemical and isotopic data.

GEOLOGICAL SETTING

The study area is situated in the middle por-

tion of the Miaoershan composite graniticbatholith, and extends from northern Guangxi tosouthern Hunan Province, South China. The Mid-dle Miaoershan granitic complex includes over tendiscrete granitic plutons. Individual plutons rangefrom over 100 km2 to 30 km2, down to less than 1km2 in outcrop area (Fig. 1). During Caledonian-age tectonism that affected a vast region of SouthChina, the Miaoershan granitic rocks intruded intothe core of the Miaoershan composite anticline,forming a huge granitic batholith. The core unitof the composite anticline consistsstratigraphically of carbonaceous slates, peliticschists, felsic volcaniclastics, metasandstones anddolostones of Presinian and Sinian-Cambrian age.

Within the study area, the MMG can bepetrographically classified into four units of vari-ous ages:

(1) The Caledonian-age Miaoershan coarse-grained, porphyritic, amphibole-bearing biotite

Fig. 1. Sketch map of the geology for the Middle Miaoershan granitic complex (modified after the Sayilin Geo-logical Party, 1990), showing four main intrusive units and sampling location of zircon for U-Pb isotopic dating.

Geochemical constraints on the petrogenesis of the Middle Miaoershan granitoids, South China 605

granitoids (CMG), dated at 368 ± 15 Ma by Rb-Srwhole-rock isochron with a (87Sr/86Sr)i of 0.719(Liu, 1988). The CMG intruded into Precambrianand Sinian-Cambrian metasedimentary rocks,forming a large batholith with an outcrop area ofabout 150 km2. They occur in the eastern portionof the study area (Fig. 1), and were locally overlainconformably by Devonian sandstone in the south-ern portion of the Miaoershan batholith. The CMGare the oldest intrusive unit in the study area.

(2) The Hercynian-age Xiangcaoping medium-to coarse-grained, porphyritic, biotite or two-micagranitoids (HXG), dated at 260 ± 5 Ma by Rb-Srwhole-rock isochron with a (87Sr/86Sr)i of 0.717(Liu, 1988). The HXG intruded into the CMG andformed a batholith with an outcrop area of about117 km2. They occupy the central portion of thestudy area (Fig. 1).

(3) The Indosinian-age Douzhashan medium-grained, two-mica granitoids (IDG), dated at 214± 3 Ma by Rb-Sr whole-rock isochron with a (87Sr/86Sr)i of 0.726 (Xu, 1994). The IDG intruded intothe HXG and formed almost a circular stock withan outcrop area of about 30 km2, and occupy thecentral portion of the Xiangcaoping graniticbatholith.

(4) The Yanshanian-age fine-grained, biotite ortwo-mica granitoids (YG), dated at 120 Ma by K-Ar mica method (Sayilin, 1990). The YG occur asstocks and apophyses, with an outcrop area rang-

ing from 14 to less than 1 km2 for each body, in-truded into the granitic rocks of various ages andexist in the eastern and northern portion of thestudy area (Fig. 1).

In addition, a large number of intrusive dikesof various compositions, e.g., fine-grained gran-ite, monzogranite, granitophyre, quartz porphyry,and pegmatite, occur in the area.

The most prominent structural features in thearea on a regional scale are major fault zoneswhich strike mainly north-east and approximatelysouth-north (Fig. 1). Both sets of fault zones aremade up of a multitude of individual faults show-ing a reverse sense of movement. Movement ofthe fault zones was mostly from Caledonian (430–

Table 1. Representative modal analyses for the Middle Miaoershan granitoids (MMG)

Note: chlorite, titanite, apatite, episote, ilmenite, magnetite, zircon and monazite are at trace levels in the all samples.(a)Abbreviations: YG = Yanshanian-age granitoids, IDG = Indosinian-age Douzhashan granitoids, HXG = Hercynian-ageXiangcaoping granitoids, CMG = Caledonian-age Miaoershan granitoids; — = below detection limit; tr. = trace. Presentedmodal analyses were done from 30 thin sections with a total count of 1200 points for the YG, from 25 thin sections with a totalcount of 1080 points for the IDG, from 28 thin sections with a total count of 1100 points for the HXG and from 36 thin sectionswith a total count of 1421 points for the CMG, respectively.

Fig. 2. The QAP diagrams (after Le Bas andStreckeisen, 1991), showing the CIPW normalized min-eral composit ions of: (a) the Caledonian-ageMiaoershan granitoids (CMG), (b) Hercynian-ageXiangcaoping granitoids (HXG), (c) Indosinian-ageDouzhashan granitoids (IDG), (d) Yanshanian-agegranitoids (YG), and (e) late intrusive vein-like fine-grained granitoids.


Table 2. Major oxide compositions (wt.%) for the MMG and host rocks


380 Ma) to Himalayan (10.0–1.5 Ma) in age. Eachfault of both sets is several to tens of kilometerslong and tens of meters wide.

PETROGRAPHY AND MINERAL COMPOSITION

Liu (1986, 1988) and Sayilin (1990) have con-ducted detailed petrographic studies on the gra-nitic rocks of the area. The descriptions given here

Table 2. (continued)

(a)Data from Liu (1986); (b)Carbonaceous slate; (c)Pelitic schist; (d)Metasandstone. Part of the present data from Sayilin (1990).LOI = loss on ignition.

represent summaries of their work plus our newobservations.

Petrographically, the Middle Miaoershan com-posite granitic batholith is predominantly com-posed of monzogranite, with minor granite, quartzmonzonite and quartz monzodiorite (Table 1, Fig.2). The granitoids contain almost equal amountsof quartz, plagioclase and K-feldspar. K-feldsparis generally microcline, microperthite and twinned


or untwinned orthoclase. Accessory minerals in-clude apatite, zircon, monazite, tourmaline,sillimanite, garnet, ilmenite, allanite (zonedeuhedral prisms), titanite, rutile and iron sulfides.Biotite usually contains small accessory mineralinclusions of apatite, zircon and monazite. Apa-tite is the most common accessory mineral and,unlike zircon and monazite, is not restricted toinclusions within biotite.

The CMG are characteristically gray-white inhand-specimen and generally heterogeneous. Theycontain abundant xenoliths, composed of slate,schist, sandstone and metapelite, and feldsparphenocrysts, ranging from 3 to 4 cm in length andexceeding 20% of the rock volume. Occasionally,some K-feldspar phenocrysts are up to 7 cm inlength. Based on modal analyses (Table 1), theCMG are biotite granite and amphibole-biotitemonzogranite, while they are mainly biotite- oramphibole-biotite monzogranite according toCIPW-normalized mineral compositions (Table 2,Fig. 2). Amphibole is a dominant mafic mineral.Plagioclase is weakly zoned oligoclase-andesine(An28–40). K-feldspar phenocrysts contain inclu-sions of quartz, biotite, and plagioclase. Quartzforms large interstitial crystals and crystal aggre-gates. Coarse-grained porphyritic biotite- oramphibole-biotite granitoids are located in thetransitional zone of the Middle Miaoershanbatholith. The core of the batholith comprisesmedium- to coarse-grained amphibole-biotitegranitoids. The core passes gradationally (increas-ing in grain size, amount and size of feldsparphenocrysts, and biotite proportion) to fine-grained porphyritic biotite granitoids, which cropout in the border of the batholith. The feldsparphenocrysts within the CMG show an obviousmagmatic flow alignment throughout.

Within the HXG massif, medium- to coarse-grained porphyritic biotite and two-micagranitoids contain K-feldspar crystals up to 3 cmin length, set in a medium- to coarse-grainedgroundmass of plagioclase, K-feldspar, biotite andquartz. Petrographic changes in grain size andmineral composition from the core to border ofthe HXG massif are obscure. Parallel alignment

of K-feldspar phenocrysts is often observed. Theabundance of K-feldspar phenocrysts ranges from10 to 25 per cent. The K-feldspar phenocrysts con-tain inclusions of plagioclase, quartz, biotite, andmuscovite. Muscovite occurs as epitaxial second-ary growth upon biotite. Plagioclase is unzonedoligoclase (An15–20).

Within the IDG massif, medium-grained two-mica granitoids are characterized by the presenceof primary muscovite (Table 1). They are medium-grained rocks with a hypidiomorphic texture. Oc-casionally they have a porphyritic texture definedby euhedral K-feldspar phenocrysts. The size ofthe K-feldspar phenocrysts ranges from 1 to 2 cmin length. Tourmaline (schòrl) is occasionally ob-served. Plagioclase in the rocks is oligoclase(An10–15).

The Yanshanian-age fine-grained biotite andtwo-mica granitoids (YG) (Fig. 2) are mainlyequigranular, with sparse quartz or biotitephenocrysts up to 6 mm in size, set in a fine-grained (1–2 mm) groundmass of K-feldspar,plagioclase, mica and quartz. Plagioclase in theYG is albite-oligoclase (An6–15).

SAMPLING AND ANALYTICAL NOTES

All analyzed samples in the present study werecollected from fresh surface exposures, drill coresand quarries of the main granitic massifs in theMiddle Miaoershan composite granitic batholith.Large (3–5 kg) fresh sample was crushed and pul-verized for bulk chemical analyses. Mineral sepa-rates of >99% purity were obtained by magneticmethods, using an auto-electromagnetic separa-tor, and careful hand picking with a binocularmicroscope.

Major element compositions of whole-rocksamples were determined with wet chemical meth-ods at the Sayilin Geological Party, and trace ele-ments were analyzed on whole-rock and biotitesamples with automated X-ray fluorescence (XRF)spectrometry on a Philips PW1400 system atNanjing University, following techniques de-scribed by Franzini et al. (1972), with a relativeaccuracy of 1% for major elements and 10% for


trace elements. Rare earth elements were deter-mined on whole-rock samples at Nanjing Univer-sity using an ICP-AES, following standard pro-cedures with a relative accuracy of 5–10%.

Oxygen isotopes were measured on quartz andwhole-rock samples with a Finnigan Mat 251-mode mass spectrometer at Nanjing University.Oxygen was extracted from samples by the fluori-nation method of Clayton and Mayeda (1963).Precision of triplicate analyses (error in 2σ) wasbetter than 0.2‰. Lead isotopes of K-feldspar

samples from the MMG were measured with amass spectrometer and isotope dilution techniquesat Beijing Research Institute of Uranium Geology.Precision estimates (2σ) are 0.05% for 207Pb/204Pband 0.1% for all other ratios. The Pb isotopes werecorrected for fractionation using a factor of 0.1%per AMU based on multiple analyses of the NBSSRM 982 standard. Zircon samples for U-Pb iso-topic dating were separated from a sample of theHXG and IDG, respectively. The zircon grainsexhibit well-defined crystal facets typical of a

Fig. 3. Variation diagram of major-element oxides (wt.%) plotted against TiO2 for the Middle Miaoershan granitoids(MMG).


magmatic origin, and have an elongate prismatichabit. Most grains are translucent, while othersare darker. Zircon separates were purified accord-ing to above-mentioned classical methods. Mea-sured grains of zircon are clear, transparent, andcolourless. U-Pb isotopic dating (error in 2σ) ofzircon samples was made on a solid-source sin-gle-collector mass spectrometer at Beijing Re-search Institute of Uranium Geology, using the

methods described by Trocki et al. (1984). Thedecay constants used in U-Pb isotopic dating ofzircon here are: λ (238U) = 1.55125 × 10–10 a–1, λ(235U) = 9.8485 × 10–10 a–1. The following Pb iso-topic compositions are assumed for the commonlead correction: 206Pb/204Pb = 18.0, 207Pb/204Pb =15.5, 208Pb/204Pb = 37.0. All results were correctedfor mass fractionation and the results were cor-rected by lead isotopes for galena from non-ra-dioactive ore in the district, following the proce-dures described by Ludwig (1991).

Fig. 4. Variation diagram of some major-element ox-ides (wt.%) plotted against SiO2 for the MiddleMiaoershan granitoids (MMG). Symbols as for Fig. 3.

Fig. 5. Histogram of SiO2 contents (a) and SiO2 vs.P2O5 plot (b) for the Middle Miaoershan granitoids(MMG). S- and I-type fields from Chappell (1999). Sym-bols as for Fig. 3.


MAJOR AND TRACE ELEMENTS

Representative whole-rock major elementanalyses for seventy-nine samples from the MMGand three samples from their metasedimentary hostrocks are given in Table 2. Selected major-elementvariation diagrams are illustrated in Figs. 3 and 4.TiO2 and SiO2 are used as the index offractionation in the variation diagrams because Tiis normally the least mobile of the major elementsand thus affords an evaluation of the mobility ofthe other elements. On a plot of TiO2 vs. oxidecontent (Fig. 3), the granitoid sequence of theMiddle Miaoershan complex defines relativelypoor trends for Fe2O3, Al2O3, SiO2, P2O5, K2O andNa2O, but a more or less well-defined trend forMgO and CaO. Plots of SiO2 vs. oxide contentshow more scatter but generally decrease with in-creasing SiO2 (Fig. 4). These compositional vari-ations appear to correspond to mixed source rocksfor the different intrusive units.

The SiO2 contents of the analyzed granitoidsrange from 63.60 to 76.45 wt.% (Fig. 5a). On aplot of SiO2 vs. P2O5 content (Fig. 5b), almost alldata points, except for one sample (No. A4-266),fall within the field of S-type granites (Chappell,

1999). With the exception of three samples fromthe CMG, the majority of the MMG samples areperaluminous with aluminous saturation indices[ASI, molar Al2O3/(CaO + Na2O + K2O)] of 1.05–1.48 (Fig. 6).

The compositional variation of biotite in suitesof granitic rocks has important petrogenetic im-plications and provides a way of classifying thehost rocks (Nachit et al., 1985). Chemical com-positions of thirteen biotite samples from theMMG are presented in Table 3 and plotted in theAltotal vs. Mg diagram (Fig. 7) of Nachit et al.(1985). All of the sample points fall within thealuminopotassic and calc-alkaline domains.

Trace-element data of the MMG are given inTable 4. Normalized geochemical patterns of thegranitoids are plotted in Fig. 8. The patterns havepositive Rb and Th anomalies and negative Ba,Nb and Zr anomalies. Values of Ce, Sm, Y and Ybare, however, close to the normalizing value,which could indicate a contribution frominfracrustal components in the source rock.

Average U and Th contents for fifty-three sam-ples from the MMG are 26.3 and 28.2 ppm, re-

Fig. 6. Al2O3/(CaO + Na2O + K2O) (molar) vs. Al2O3/(Na2O + K2O) (molar) plot of the Middle Miaoershangranitoids (MMG). Symbols as for Fig. 3.

Fig. 7. Altotal-Mg diagram (after Nachit et al., 1985)for biotites from the Middle Miaoershan granitic com-plex. Fields of the granitic biotite discriminated ac-cording to their host-rock magmatic type: A = alka-line-peralkaline series, SA = subalkaline (monzonitic)series, CA = calc-alkaline series, AK = aluminopotassicseries. Symbols as for Fig. 3.


Tabl

e 3.

C

hem

ical

com

posi

tion

s (w

t.%

) an

d st

ruct

ural

for

mul

ae o

f bi

otit

e fr

om t

he M

MG

(a) A

bbre

v iat

ions

as

for

Tabl

e 1.


Tabl

e 4.

Tr

ace

elem

ent

com

posi

tion

s (p

pm)

for

the

MM

G

(a) A

bbre

v iat

ions

as

for

Tabl

e 1;

— =

be l

ow d

e te c

tion

lim

it.


spectively. Average U and Th contents for thegranitoids of different intrusive stage are: 8.6 and31.4 ppm (n = 11) for the CMG, 9.2 and 23.9 ppm(n = 16) for the HXG, 34.0 and 32.0 ppm (n = 11)for the IDG, 40.3 and 18.6 ppm (n = 5) for theYG, and 25.0 and 25.0 ppm (n = 10) for the late,vein-like, fine-grained granites (VG) (Fig. 9a). Theaverage values are higher than those commonlyfound in granitic rocks (3–5 ppm U, 10–12 ppmTh, Adams et al., 1959, Clark et al., 1966). More-over, generally the U contents increase and Th/Udecreases steadily with evolution of the graniticmagmas (Fig. 9). Th/U of the MMG ranges from3.7 to 0.5 with an average value of 1.1. Contentsof U, Th and Th/U in the rocks are highly vari-able. There are many local enrichments and de-pletions in U, and the lack of correlation betweenindividual U and Th values indicates that someremobilization of U has occurred in the graniticrocks. Some important vein-type, hydrothermal Udeposits formed in the IDG, which contain anoma-lously high U contents (up to 34.0 ppm).

Representative REE contents of the MMG andtheir host rocks are given in Table 5. The granitoidsof various intrusive stages have distinctivechondrite-normalized REE patterns (Fig. 10). Thesamples are generally depleted in the HREE.Chondrite-normalized REE patterns for the

granitoids are heterogeneous with (La/Yb)N be-tween 5.75 and 14.38 and variably negative Ce,Eu anomalies (Eu/Eu* = 0.24–0.52). From theearly to late intrusive stage, the magmatic units

Fig. 8. Normalized trace-element abundance patterns of the Middle Miaoershan granitoids (MMG) (normalizingvalues from McDonough et al., 1991). Symbols as for Fig. 3.

Fig. 9. Variation diagram of U and Th concentrations(a) and Th/U (b) for the Middle Miaoershan granitoids(MMG). Symbols as for Fig. 3.


Tabl

e 5.

R

EE

ana

lyse

s (p

pm)

for

the

host

roc

ks a

nd M

MG

(a) D

ata

from

Say

ilin

(19

90)

and

Liu

(19

86).


Fig. 10. Chondrite-normalized REE diagram for: (a) the metasedimentary host rocks of the Miaoershan compos-ite granitic complex, (b) the Yanshanian-age granitoids (YG), (c) the Indosinian-age Douzhashan granitoids (IDG),(d) the Hercynian-age Xiangcaoping granitoids (HXG), and (e) the Caledonian-age Miaoershan granitoids (CMG).Normalization values from Taylor and Mclennan (1985).


show decreases in ∑REE and Eu/Eu*. The (La/Yb)N and SiO2 for the granitoids show a poor cor-relation (Fig. 11a). In a Eu/Yb-Ce/Yb plot (Fig.11b) however, all sample points of the granitoidsare arrayed linearly, typical of S-type granites(Chappell, 1999). In all the intrusive units, theCMG have the highest ∑REE (Table 5) and thesteepest, light REE (LREE)-enriched patterns, (La/Yb)N = 9.35–14.38. The YG and host rocks of thebatholith have low ∑REE and steep REE patternswith (La/Yb)N = 8.08. Most of the granitoidsrocks, however, have somewhat higher REE con-tents than the host rocks, indicating that thegranitoid rocks were slightly REE-enriched dur-ing anatectic generation of the granitic magmafrom the metasedimentary host rocks. Chondrite-normalized REE patterns of all of the granitoidsand their host rocks show a quite similar shape

and negative Ce, Eu anomalies. The negative Ceanomalies for the host metasedimentary rocks(Fig. 10a) may imply that the host rocks containbiolithites which often show negative Ce anoma-lies on their REEN patterns (Hansen et al., 2002).The negative Ce anomalies for some of the CMG,HXG and IDG may result from inheritance to thoseof the host metasedimentary rocks and from some-what weathering (oxidation) of the granitoids. Thisindicates that the REEs in the granitoids were mostlikely derived from the host metasedimentaryrocks.

ISOTOPE GEOCHEMISTRY

Sr isotopic variationRepresentative whole-rock Sr isotopes for the

three granitic massifs, viz. the CMG, HXG andIDG, were reported by Xu (1994). The granitoids

Fig. 11. (La/Yb)N vs. SiO2 (a) and Ce/Yb vs. Eu/Yb(b) plots for representative the Middle Miaoershangranitoids (MMG). Symbols as for Fig. 3.

Fig. 12. (87Sr/86Sr)i vs. SiO2 (a) and (87Sr/86Sr)i vs.Rb/Sr (b) diagrams for the Middle Miaoershangranitoids (MMG), drawn according to data from Xu(1994). Symbols as for Fig. 3.


have variable Rb/Sr values (1.3–18.1) and haveevolved to high and variable present-day 87Sr/86Srvalues (0.7380–1.0030, 2σ). Reported 87Sr/86Srinitial ratios, i.e., (87Sr/86Sr)i, range from 0.70761to 0.71446 (mean 0.71237, 4 samples) for theCMG, from 0.71476 to 0.71959 (mean 0.71667, 7samples) for the HXG and from 0.72325 to0.72935 (mean 0.72670, 5 samples) for the IDG,respectively. A low (87Sr/86Sr)i value of 0.70761(1 sample) for the CMG was also reported (Xu,1994), suggestive of an infracrustal origin. Thesample points for the CMG and HXG, however,display significant scatter (Fig. 12) that points toa heterogeneous source of the granitic melts. To-gether the sample points form a broad linear ar-ray in the plots of (87Sr/86Sr)i vs. SiO2 (Fig. 12a)and (87Sr/86Sr)i vs. Rb/Sr (Fig. 12b), and show thatincreasing (87Sr/86Sr)i correlates with increasingSiO2 content and Rb/Sr values. It thus is indicatedthat the different intrusive units may have mixedsource rocks.

Isotopic compositions of leadRecent studies have shown that lead isotopes

provide useful information in the understandingof crustal evolution, and often record evidence ofan ancient crustal memory. The lead isotopes foreighteen K-feldspar samples from the MMG aregiven in Table 6 and plotted in Fig. 13. The leadisotopes for the MMG have a limited variationboth within and between massifs. The plots of207Pb/204Pb vs. 206Pb/204Pb (Fig. 13a) and 208Pb/204Pb vs. 206Pb/204Pb (Fig. 13b) show that 18 sam-ple points are near the upper crust growth curvedetermined by Doe and Zartman (1979) in theirsynthesis of lead isotopic signatures of differentgeological environments for their plumbotectonicmodel. The data thus indicate that the majority ofthe rock lead was derived from pre-existing,evolved crustal material. The Pb isotopes plot ina rather wide array and display scatter in the 207Pb/204Pb vs. 206Pb/204Pb diagram. The data indicateinvolvement of heterogeneous sources for the gra-

Table 6. Lead isotopic compositions of K-feldspar from the MMG

Sample No. U (ppm) Pb (ppm) 206Pb/204Pb 207Pb/204Pb 208Pb/204Pb

Yanshanian-age granitoids (YG)

Ag-19 22.3 45.3 19.336 15.729 38.618G02 12.8 46.3 18.770 15.713 38.592G19 11.4 54.1 18.465 15.718 38.781G20 19.8 40.2 18.759 15.747 39.310

Indosinian-age Douzhashan granitoids (IDG)

Y1 11.8 40.2 18.913 15.701 38.847Y2 10.6 43.1 19.120 15.733 39.053Y3 12.1 56.0 18.969 15.757 39.013Y4 14.1 45.6 19.037 15.707 38.827Y5 22.3 50.4 19.178 15.750 39.034

Hercynian-age Xiangcaoping granitoids (HXG)

S2 10.2 84.1 19.045 15.702 38.881S3 6.7 54.3 18.966 15.718 38.943S4 6.8 75.2 19.103 15.766 39.150S6 7.4 45.7 18.930 15.750 38.947S7 8.3 37.9 19.281 15.701 38.478

Caledonian-age Miaoershan granitoids (CMG)

Ag-7 10.4 50.1 19.222 15.733 38.616Ag-17 9.8 63.7 19.1859 15.764 39.032Ag-32 9.6 60.5 19.0626 15.680 38.829G-002 6.7 55.3 19.1336 15.697 38.796


nitic melts. The lead isotopic data, combined with(87Sr/86Sr)i (0.70761–0.72935) for the MMG, in-dicate that the MMG may be different products ofa granitic magma, and possess characteristics ofS-type granite (Chappell and White, 1974). Thesefeatures preclude large scale involvement of an-cient lower crustal granulites in the generation ofthe granitic melts (Tomascak et al., 1996).

U-Pb isotopes of zirconSix different grain-size fractions of zircon from

the HXG were analyzed for U-Pb age (Table 7)and the results are shown on the isochron plot ofFig. 14. For the HXG, it may be noted that the206Pb/238U ages of six samples (234, 261, 267, 230,225 and 233 Ma) are in the proximity of their207Pb/235U ages (224, 261, 298, 235, 300 and 294

Fig. 14. U-Pb isochron plot of zircon from theHercynian-age Xiangcaoping granitoids (HXG). Ana-lytical data in Table 7.

Fig. 13. Plots of 207Pb/204Pb vs. 206Pb/204Pb (a) and208Pb/204Pb vs. 206Pb/204Pb (b) for K-feldspar from theMiddle Miaoershan granitoids (MMG). Symbols as forFig. 3.

Ma), respectively. The U-Pb isochron age for thesix zircon samples is 296 ± 31 Ma (2σ errors, Fig.14). This age is close to the Rb-Sr whole-rockisochron age (260 Ma) reported by Liu (1988) andfalls in the time range of early Hercyniantectonism (early Permian), that affected a vast re-gion in South China. It is confirmed that the HXGformed during Hercynian regional tectonism. Sev-eral Hercynian-age granite bodies have been rec-ognized in South China during the past 30 years(Min, 1992; Zhang, 1982).

Xu (1994) reported that five zircon samplesfor the CMG are discordant with a lower inter-cept at 364 Ma and an upper intercept at 1126 Maon the U-Pb Concordia diagram. The lower inter-cept of 364 Ma corresponds to a Rb-Sr isochronage of 368 Ma (Liu, 1988) and is equivalent tothe CMG emplacement age. The upper interceptof 1126 Ma may be a sedimentary age of sourcerock of the CMG. The most likely source rocksare slates and schists of the Presinian Lower BanxiFormation. There are metasedimentary rocks dis-tributed over a vast region of the Miaoershan area.Thus, magmatic zircons within the MMG, contain-ing a component of inherited radiogenic lead, ap-pear to yield an upper intercept age of 1126 Ma.The present-day position of zircon points on theConcordia diagram could be the result of mixingbetween radiogenic lead in 368 Ma old magmatic


zircons and a more ancient component derivedfrom detrital zircons in metasedimentary basementin this area. The presence of inherited zircons asancient core relicts within the magmatic zirconsof the CMG is evidence for this process. Cathodeluminescence images show that many grains ofzircon from the CMG have distinct rounded coressurrounded by more or less euhedral rims. It isinferred that the former is inherited zircon derivedfrom the metasedimentary source rocks, and thelatter is magmatic zircon grown during solidifi-cation of the CMG.

To summarize, the contribution of U-Pb zir-con studies to granitoid petrogenesis is to indi-cate the presence of an inherited radiogenic leadcomponent and a multi-stage evolution history.

Oxygen isotopesδ18O values of nineteen quartz samples and one

whole-rock sample from different massifs in theMiddle Miaoershan granitic complex range from10.12 to 12.99‰ (mean 11.36‰, 1σ) (Table 8).All of the δ18O values fall within a relatively nar-row range. Comparison of the whole-rock andmineral values suggests that the oxygen isotopiccompositions of the MMG have not been signifi-cantly modified by post-magmatic processes suchas interaction with a meteoric-hydrothermal sys-tem. The δ18O values of quartz are thus consid-ered to be representative of the isotopic composi-

tions of the magmas at the level of emplacement.The small variation of δ18O values for both withina single massif and between different intrusionsmay be a consequence of some different processes.In part, such variations probably reflect small dif-ferences in the isotopic compositions of themetasedimentary source rocks, and in isotopicfractionations associated with partial melting frac-tional crystallization (Taylor, 1978).

DISCUSSION

Possible source rocksIn summary, the field relations, petrographic

and mineralogical characteristics, major oxide,trace element and isotopic geochemistry of theMMG are consistent with the possibility that thegranitoids were predominantly derived by partialmelting of Proterozoic and Lower Paleozoicmetasedimentary source rocks, and clearly iden-tify the granitoids as S-type in origin accordingto the classification of Chappell and White (1974).

The reported whole-rock initial (87Sr/86Sr)i

values for the MMG, ranging from 0.71012 to0.73463 except 0.70761 for 1 sample from theCMG (Xu, 1994), are comparatively radiogenic.Zhang (1985) reported that the initial (87Sr/86Sr)i

values for the Sinian-Cambrian slates and schistsin the area range from 0.712 to 0.720 (600 Ma)and from 0.715 to 0.724 (590 Ma), respectively.

Table 7. U-Pb age determination on zircon from the Hercynian-age Xiangcaoping granitoids (HXG)


Oxygen isotopic compositions of the MMG arehigh and relatively homogeneous (10.12–12.99‰,mean 11.36‰) (Table 8). Such high and relativelyhomogeneous δ18O values are typical formetasedimentary rocks including aluminum-richones (Taylor, 1978), and similar to those of otherperaluminous granitoids from southern ArmoricanMassif (Bernard-Griffiths et al . , 1985),Ploumanac’h in Brittany (Albarède et al., 1980)and North Black Forest (Hoefs and Emmermann,1983). All of these granites have been interpretedto have been derived from a crustal meta-sedimentary source based on their 18O-rich char-acter. The K-feldspar lead isotopic compositionsfor the MMG are significantly more radiogenicand also suggest that the source rocks of thegranitoids had Th/U typical of the upper crust (Fig.

13) (Pressley and Brown, 1999). The limited vari-ation in K-feldspar lead isotopic compositionsobserved both within a single massif and betweendifferent massifs (Table 6) is more probably re-lated to the provenance of their metasedimentarysource rocks. Mixing of sediments from two dif-ferent rocks with distinct lead isotopic composi-tions for a metasedimentary source could also pro-duce variable lead isotopic ratios for differentgranite samples within a single massif (Downeset al., 1997). This mixing could also explain thelimited variation of the chemical compositions andinitial (87Sr/86Sr)i values occurring both within andbetween different massifs for Middle Miaoershancomplex (Tables 2, 4 and 5).

The late three intrusive units, viz. the HXG,IDG and YG, have high ASI values (1.05–1.48)in chemical compositions, and the data points fallwithin the field of peraluminous granites (Fig. 6)containing muscovite, biotite and tourmaline, im-plying metasedimentary sources (Benard et al.,1985). Chemical compositions of the three lateintrusive units are similar to those of S-type gran-ites from the Lachlan Fold Belt, Australia(Chappell and White, 1992). They contain signifi-cantly less CaO, Na2O, and Sr, and more K2O, Rb,and Pb than the I-type granites. The REE patternsof the late three intrusive units are similar to thoseof the host metasedimentary rocks of the MMG(Fig. 10).

Relative to the HXG, IDG, and YG however,the CMG are somewhat in terms of differentchemical compositions. A number of samples forthe CMG have low initial (87Sr/86Sr)i of 0.70761(Xu, 1994) and low ASI values below the S-typethreshold of 1.1 (0.92–1.1). On the Al2O3/(CaO +Na2O + K2O) (molar) vs. Al2O3/(Na2O + K2O)(molar) plot (Fig. 6), three sample points of theCMG fall in the field of the metaluminous gran-ites containing amphibole and biotite (modal pro-portions of muscovite almost absent), implyingsource rock materials of mafic to intermediate ig-neous composition or an infracrustal derivation(White and Chappell, 1988). However, the major-ity of sample points for the CMG fall in the fieldof the peraluminous granites (Fig. 6). Thus, there

(a)WR = whole rock, Qtz = quartz; (b)Data from Sayilin (1990).

Table 8. Oxygen isotopic data of quartz from theMMG

Sample No. Phase(a) δ18O (‰)

Yanshanian-age granitoids (YG)

G02 Qtz 11.15G19 Qtz 12.28

Indosinian-age Douzhashan granitoids (IDG)

A8-78(b) Qtz 10.39Y1 Qtz 11.13Y2 Qtz 11.05Y3 Qtz 10.57Y4 Qtz 11.38Y5 Qtz 11.16Y6 Qtz 11.60G18 Qtz 11.90

Hercynian-age Xiangcaoping granitoids (HXG)

S1 Qtz 11.08S2 Qtz 12.99S3 Qtz 11.37S4 Qtz 11.59S9 Qtz 10.12G21 Qtz 12.02G34 Qtz 11.16

Caledonian-age Miaoershan granitoids (CMG)

Ag-7(b) Qtz 11.37Ag-17(b) WR 11.89Ag-32(b) Qtz 11.02


are reasons to believe that magma of the CMGwas not generated solely from partial melting ofpure metasedimentary protoliths. The existence ofcoherent geochemical trends in the chemical com-positions between different intrusive units, theirclose spatial-temporal relationships and the pres-ence of inherited zircons as relict ancient coreswithin magmatic overgrowths of the CMG sug-gest a cogenetic origin for some members of Mid-dle Miaoershan batholith. In addition, the major-ity of greenschist-facies metasedimentaryxenoliths occurring within the granitoids of vari-ous intrusive stages contain garnet, indicating ametasedimentary source. Neither mafic nor felsicmeta-igneous granulite-facies lower-crustalxenoliths contain garnet (Williamson et al., 1996).

Petrogenetic processesIn the Middle Miaoershan granitic complex,

the following characteristics suggest that the in-dependent granitic bodies are the products of fluid-magmatic processes: presence of sharp intrusivecontacts between different massifs and a strongthermal-contact metamorphic aureole in the ex-ternal contact zone of the complex, pervasivemetasedimentary xenoliths consisting of biotite-quartz schists, sandstones and pelitic slates, par-allel and semiparallel alignment of K-feldsparphenocrysts showing a magmatic flow which ismore pronounced close to the country rock con-tacts. The minerals and their textures appear tohave formed by crystallization of granitic melt.

The overall similarities in geochemical andisotopic compositions for all four intrusive unitsindicate a common model of origin. Thegeochronology and the somewhat differentgeochemical trends suggest that they each repre-sent a separate pulse of magma.

By combining the available evidence, it ap-pears that partial melting of the ancientmetasedimentary basement as well as re-meltingof pre-existing granitoids (e.g., a re-melting of theCMG for forming the HXG, IDG, and YG, andre-melting of the CMG and HXG for forming ofthe IDG and YG) may be the dominant processesin the genesis of the MMG:

(1) As there are large time-gaps between dif-ferent intrusive events of the granitic complex,they are unlikely to represent fractionated equiva-lents. The time-gap ranges based on isotopic dat-ing are 72, 82, and 94 Ma between intrusions ofthe CMG and HXG, the HXG and IDG, and theIDG and YG, respectively.

(2) Limited variations and inheritances in themajor- and trace-element compositions betweendifferent intrusive units are better explained byvarying degrees of partial melting for mixedsource rocks. The degree of partial melting islikely to have been a function of source fertility,which itself is likely to have been strongly influ-enced by previous partial melting episodes thatproduced the earlier granitoids. The REE patternsof the four intrusive units are consistent with ori-gins by equilibrium partial melting of meta-sedimentary sources (Sevigny et al., 1989;Tomascak et al., 1996). This is supported by thefact that granitoids of the main units have highand relatively homogeneous δ18O values (Table8). Magmas with δ18O > +7.5‰ must have beenderived from, or have exchanged with, a precur-sor material that once resided on or near theEarth’s surface, and rule out the possibility of frac-tional crystallization from a mafic magma (withδ18O ≈ +6‰) (Taylor and Sheppard, 1986). Withrespect to the old intrusive unit (CMG), the threeyoung intrusive units (HXG, IDG and YG) pos-sess generally lower ∑REE, Zr and larger nega-tive Eu anomalies (Tables 4 and 5), indicating thatthey may be partially derived from re-melting ofthe CMG, and that plagioclase, zircon and LREE-bearing accessory phases remained in the sourcefollowing partial re-melting of the CMG.

(3) Within the MMG, there are pervasiveresidues and metasedimentary xenoliths. Higher-degree partial melts will contain larger amountsof residual phases (White and Chappell, 1977).Sayilin (1990) reported that crystallization tem-peratures of the MMG range from 780° to 850°Cbased on detailed melting experimental determi-nation of glass inclusions in quartz. The crystalli-zation temperatures are consistent with those ofalmost all granitoids formed by partial melting of


metasedimentary sources in South China (Xu,1982). A maximum crystallization pressure of 0.25GPa for the CMG, corresponding to emplacementdepths of ~8.25 km, has been estimated based onan amphibole-biotite geobarometer (Liu, 1986).It is inferred that the emplacement depth of theHXG, IDG, and YG should be less than that ofthe CMG, and shallowed from the HXG to YG,coincident with a change of intrusive scale for thebatholith from CMG and HXG, through the stockfor the IDG, to stock and apophyse for the YG.

(4) The Miaoershan Batholith is regarded as asatellite of the huge Yuechengling graniticbatholith in South China. Both batholiths, with atotal present-day outcrop area of 3160 km2, aresituated structurally within the core of the NE-striking Miaoershan-Yuechengling composite an-ticline formed by Early Caledonian orogenesis andregional metamorphism, resulting in localmigmatization and melting of Palaeozoic base-ment rocks. The Miaoershan Batholith is regardedas having cut upward and discordantly across sev-eral formations in the core, and obtained emplace-ment space from melting of the basement rockswithin the anticline core. However, partial re-melt-ing of granitic magmas for the HXG, IDG, andYG (unlike the CMG), were channeled by a NNE-striking fault system (Fig. 1) generated during themain episodes of Hercynian, Indosinian andYanshanian regional tectonism, respectively. TheNNE-striking fault system is likely to have beenreactivated during the main episodes of regionaltectonism. It is certain that some granitoids nearthe fault systems were remelted by the ascendinggranitic magmas. This is confirmed by the verylow abundances of Cs within the HXG, IDG, andYG (Table 4), indicating that the granitoids werepartially derived from a source which had experi-enced a previous episode of melting because thehighly incompatible Cs would have been lost inthis process (London, 1995). Thus the HXG, IDGand YG, unlike the CMG, were derived from overtwo supracrustal sources. This results in limitedvariations and inheritances of the major- and trace-element compositions between different intrusiveunits (Figs. 3–8). It is supported by presence of

inherited zircons as ancient core relicts within themagmatic zircons of the CMG.

(5) One of the important features for the MMGis the coeval emplacement of various granite typesshortly after the end of collisional orogeny. Melt-ing of the Early Palaeozoic metasedimentary base-ment rocks in the Middle Miaoershan area mostlikely was a consequence of anomalously highcrustal temperatures due to radioactive heat-pro-ducing elements in the rocks combined with anadditional tectono-heat supplied by regionaltectonism. The additional tectono-heat is sup-ported by fact that the above-mentioned four mainintrusive events in the study area are in time co-eval with the four main regional tectonic events:the Caledonian, Hercynian, Indosinian andYanshanian tectonism, that occurred in vast regionof South China. The study area was affected byfolding and faulting during the main regionaltectonism. It is most likely that the regionaltectonism not only supplied partial heat for melt-ing of the metasedimentary sources, but also in-fluenced the localization of ascent pathway.

A commonly favored hypothesis for the originof the Miaoershan S-type granitoids involvescrustal melting in response to radioactive heatingfrom U, Th and K within a thickened crust (>60km) (Kröner and Willner, 1998). In South China,there are lots of U-rich granitic massifs that hostimportant economic U deposits. Almost all of themare S-type in origin and roughly have a similargeological setting of emplacement. Usually, theirsources (mainly metasedimentary rocks) and in-truded host rocks contain high contents of heat-producing radioactive elements, especially U(Zhang, 1982).

CONCLUSIONS

The field relations, and petrographic andgeochemical data presented in this study suggestthat the Middle Miaoershan granitic complex iscomposed of four independent intrusive stages.Commonly, there are sharp intrusive contacts be-tween the complex and its host metasedimentaryrocks, and between different intrusive massifs.


This is confirmed by the Rb-Sr, U-Pb and K-Arisotopic dating of 368 Ma (Caledonian in age),296 Ma (Hercynian in age), 214 Ma (Indosinianin age) and 120 Ma (Yanshanian in age) for theCMG, HXG, IDG and YG, respectively.Petrographically, the complex consists ofmonzogranite and granite with minor quartzmonzonite and quartz monzodiorite.

Geochemical and isotopic data suggest that themajority of the MMG, including the HXG, IDG,YG, and partial CMG, are peraluminous and pos-sess a crustal origin. They most likely are derivedfrom Proterozoic and Lower Paleozoic meta-sedimentary source rocks with a high initial (87Sr/86Sr)i and ASI values. The CMG, however, areconsidered to have had a mixed supracrustalmetasedimentary source, with minor infracrustalcomponents that had a low initial (87Sr/86Sr)i

(0.70761), a low ASI value, and contained somemafic minerals. The inner phase of the CMG ismetaluminous and amphibole-bearing and simi-lar to that of Lachlan Fold Belt I-type granites.More probably, the Sr isotopic variations withinthe CMG could be related to mixed sources withdifferent Sr isotopic compositions. Partial melt-ing of the ancient metasedimentary basement com-bined with re-melting of the granitoids, formedby previous partial melting episodes, may be thedominant processes in the genesis of the MMG.This type of genetic model could better explainthe limited variations and inheritances in thechemical composition, Sr, Pb isotopeheterogeneities between different intrusive units,and the presence of inherited zircons as ancientcore relicts within the young magmatic zircons.Partial melting of the Middle Miaoershan terrainis considered to have been produced by radioac-tive heat combined with additional tectono-heat,initiated by the liberation of large volumes ofwater from metamorphosed basement lithologies.

Acknowledgments—Our study was supported by theNational Natural Science Foundation of China (GrantNo. 40173031). Thanks are due to the Bureau of Geol-ogy, China National Nuclear Corporation and the Ura-nium Geology Bureau of Center-South China for theirfinancial supports to the present research, to the Sayilinand Salinliu Geological Party for their aid in the field

and partial unpublished data. We greatly appreciate thecritical review and helpful comment of Prof. R. J.Arculus and one anonymous reviewer on the presentdraft.

REFERENCES

Adams, J. A. S., Osmond, J. K. and Rogers, J. J. W.(1959) The geochemistry of thorium and uranium.Phys. Chem. Earth 3, 298–348.

Albarède, F., Dupuis, C. and Taylor, Tr. H. P. (1980)18O/16O evidence for noncogenetic magmas associ-ated in a 300 Ma old concentric pluton atPloumanac’h (Brittany, France). J. Geol. Soc.London 137, 641–647.

Benard, F., Moutou, P. and Pichavant, M. (1985) Phaserelations of tourmaline leucogranites and the signifi-cance of tourmaline in silicic magmas. J. Geol. 93,271–291.

Bernard-Griffiths, J., Peucat, J. J., Sheppard, S. andVidal, Ph. (1985) Petrogenesis of Hercynianleucogranites from the southern Armorican Massif:contribution of REE and isotopic (Sr, Nd, Pb and O)geochemical data to the study of source rock charac-teristics and ages. Earth Planet. Sci. Lett. 74, 235–250.

Chappell, B. W. (1999) Aluminum saturation in I- andS-type granites and the characterization offractionated haplogranites. Lithos 46, 535–551.

Chappell, B. W. and White, A. J. R. (1974) Two con-trasting granite types. Pacific Geol. 8, 173–174.

Chappell, B. W. and White, A. J. R. (1992) I- and S-type granites in the Lachlan Fold Belt. The SecondHutton Symposium on the Origin of Granites andRelated Rocks. Proceedings of a Symposium Held atthe Australian Academy of Science Canberra, 23–28September, 1991 (Brown, P. E. and Chappell, B. W.,eds.), 1–26, Northern Ireland and bound in U.S.A.

Clark, S. P., Peterman, Z. E. and Heier, K. S. (1966)Abundances of U, Th and K. Geol. Soc. Am. Mem.97, 45–52.

Clayton, R. N. and Mayeda, T. K. (1963) The use ofbromine pentafluoride in the extraction of oxygenfrom oxides and silicates for isotopic analysis.Geochim. Cosmochim. Acta 27, 43–52.

Doe, B. R. and Zartman, R. E. (1979) PlumbotectonicsI, the phanerozoic. Geochemistry of HydrothermalOre Deposits (2nd ed.) (Barnes, H. L., ed.), 22–70,Wiley-Interscience, New York.

Downes, H., Shaw, A., Williamson, B. J. and Thirlwall,M. F. (1997) Sr, Nd a 136 (1997) 99–122 Hercyniangranodiorites and monzogranites, Massif Central,France. Chem. Geol. 136, 99–122.

Franzini, M., Leoni, L. and Saitta, M. (1972) A simplemethod to valutate the matrix effect in X-ray fluo-


rescence analysis. X-Ray Spectrum 1, 151–154.Hansen, J., Skjerlie, K. P., Pedersen, R. B. and Rosa, J.

D. L. (2002) Crustal melting in the lower parts ofisland arcs: an example from the Bremanger granitoidcomplex, West Norwegian Caledonides. Contrib.Mineral. Petrol. 143, 316–335.

Hoefs, J. and Emmermann, R. (1983) The oxygen iso-topic compositions of Hercynian granites and pre-Hercynian gneisses from the Schwarzwald, SWGermany. Contrib. Mineral. Petrol. 83, 320–329.

Kröner, A. and Willner, A. P. (1998) Time of formationand peak of Variscan HP-HT metamorphism ofquartz-feldspar rocks in the central Erzgebirge,Saxony, Germany. Contrib. Mineral. Petrol. 132, 1–20.

Le Bas and Streckeisen, A. L. (1991) The IUGS sys-tematics of igneous rocks. J. Geol. Soc. London 148,825–833.

Liu, J. S. (1986) On studies of the geological charac-teristics of the Middle Miaoershan granites and theorigin of a uranium deposit. M.D. Thesis (in Chi-nese, unpublished).

Liu, Y. B. (1988) Relationship between uranium min-eralization and the Miaoershan granites (in Chinese,unpublished report).

London, D. (1995) Geochemical features ofperaluminous granites, pegmatites, and rhyolites assource of lithophile metal deposits. Magmas, Fluids,and Ore Deposits (Thompson, J. F. H., ed.), 175–202, Mineralogical Society of Canada Short CourseSeries 23.

Ludwig, K. R. (1991) Isoplot: a plotting and regres-sion program for radiogenic-isotopic data, version2.53. US Geol. Sur. Open File Rep. 91-445, 39.

McDonough, W. F., Sun, S., Ringwood, A. E., Jagoutz,E. and Hofmann, A. W. (1991) K, Rb and Cs in theearth and moon and the evolution of the earth’s man-tle. Geochim. Cosmochim. Acta (Ross Taylor Sym-posium volume), 68–76.

Min, M.-Z. (1992) The forming conditions of LiuchenHercynian potash-feldspar granite. Guangxi Prov-ince, South China. Journal of Guilin College Geol-ogy 12, 282–288 (in Chinese with English abstract).

Min, M.-Z., Luo, X.-Z., Du, G.-S., He, B.-A. andCampbell , A. R. (1999) Mineralogical andgeochemical constraints on the genesis of the gran-ite-hosted Huangao uranium deposit, SE China. OreGeology Reviews 14, 105–127.

Nachit, H., Razafimahefa, N., Stussi, J. M. andCarron, J. P. (1985) Composition chimique desbiotites et typologie magmatique des granitoids. C.R. Acad. Sci. Paris 301, 813–818.

Pressley, R. A. and Brown, M. (1999) The Phillipspluton, Maine, USA: evidence of heterogeneouscrustal source and implications for granite ascent andemplacement mechanisms in convergent orogens.

Lithos 46, 335–366.Sayilin Geological Party (1990) Reconnaissance report

of uranium mineralization in Middle Miaoershan area(in Chinese, unpublished report).

Sayilin Geological Party (1990) The Miaoershan gran-ites (in Chinese, unpublished report).

Sevigny, J. H., Parrish, R. R. and Ghent, E. D. (1989)Petrogenesis of peraluminous granites, MonsheeMountains, southeastern Canadian cordillera. J. Pet-rol. 30, 557–581.

Taylor, H. P., Jr. (1978) Oxygen and hydrogen isotopestudies of plutonic granitic rocks. Earth Planet. Sci.Lett. 38, 177–210.

Taylor, H. P., Jr. and Sheppard, S. M. F. (1986) Igne-ous rocks: I. Processes of isotopic fractionation andisotope systematic. Stable Isotopes in High Tempera-ture Geological Processes (Valley, J. W., Taylor, H.P., Jr. and O’Neil, J. R., eds.), 227–271, Rev. Miner.

Taylor, S. R. and Mclennan, S. M. (1985) The Conti-nental Crust: Its Composition and Evolution. Oxford,Blackwell, 350 pp.

Tomascak, P. B., Krogstad, E. J. and Walker, R. J.(1996) Nature of the crust in Maine, USA: evidencefrom the Sebago batholith. Contrib. Mineral. Petrol.125, 45–59.

Trocki, L. K., Curtis, D. B., Gancarz, A. J. and Banar,J. C. (1984) Ages of major uranium mineralizationand lead loss in the Key Lake uranium deposits,northern Saskatchewan, Canada. Econ. Geol. 79,1378–1386.

White, A. J . R. and Chappell , B. W. (1977)Ultrametamorphism and granitoid genesis.Tectonophysics 43, 7–22.

White, A. J. R. and Chappell, B. W. (1988) Somesupracrustal (S-type) granites of the Lachlan FoldBelt. R. Soc. Edinburgh Earth Sci. 79, 169–181.

Williamson, B. J., Shaw, A., Downes, H. and Thirlwall,M. F. (1996) Geochemical constraints on the genesisof Hercynian two-mica leucogranites from theMassif Central, France. Chem. Geol. 127, 25–42.

Xu, K.-Q. (1982) Geneses of granitoid and metallogeny.Proceedings of Symposium on Granite Geology andMetallogeny (Tu, G.-C. and Xu, K.-Q., eds.), 235–248, Jangsu Science and Technique Publisher, China.

Xu, W. C. (1994) Geochronological study on theMiaoershan composite granitic batholith. Acta Pet-rological Sinica 10, 330–337 (in Chinese with Eng-lish abstract).

Zhang, L.-G. (1985) Employment of Stable Isotopes inGeosciences. Science and Technique Publisher, Xian,384 pp. (in Chinese).

Zhang, Z.-H. (1982) S- and I-type granitoids and theiruranium mineralization in South China. Proceedingsof Symposium on Granite Geology and Metallogeny(Tu, G.-C. and Xu, K.-Q., eds.), 267–274, JangsuScience and Technique Publisher, China.

geochemical constraints on the petrogenesis of the - terrapub

Documents