下地壳部分熔融的产物：燕山早期广东腊圃花岗岩成因

下地壳部分熔融的产物：燕山早期广东腊圃花岗岩成因

刘昌实, 陈小明, 王汝成, 张爱铖, 胡欢

南京大学,地球科学系,内生金属矿床成矿机制研究国家重点实验室,江苏,南京, 210093

收稿日期:2005-09-20 修回日期:2005-09-20 出版日期:2005-09-20 发布日期:2005-09-20

The Products of Partial Melting of the Lower Crust： Origin of Early Yanshanian Lapu Monzogranite, Guangdong Province

Liu Chang-shi, Chen Xiao-ming, Wang Ru-cheng, Zhang Ai-cheng, Hu Huan

Department of Earth Sciences, State Key Laboratory for Mineral Deposit Research, Nanjing University, Nanjing 210093, China

Received:2005-09-20 Revised:2005-09-20 Online:2005-09-20 Published:2005-09-20

摘要/Abstract

摘要： 出露于广东省从化市南的腊圃角闪黑云二长花岗岩占地面积约500km^2,由钙质角闪石（0．5％）,黑云母（11％～13％）,斜长石（An35～41,29％～31％）,隐纹长石（24％～31％）和石英（36％～37％）组成,含富Ca,Ti副矿物褐帘石和榍石等。根据颗粒锆石u—Ph定年,其定位时间为163±2Ma（中侏罗世）。化学成分上为弱过铝质（平均A／NKC=1．043）,富K2O（平均4．72％）,属高钾钙碱性系列。稀土总量较高,EREE=（180～460）×10^-6,轻稀土明显富集,重稀土明显亏损,具有大的（La／Yb）。值（平均19）,说明熔融作用是在下地壳深度进行（P〉10^8Pa）,石榴子石是主要的残留相矿物。多种源岩示踪方法指出,形成腊圃岩体岩浆的源岩是变硬砂岩或变角闪岩（包括变火成岩）。模拟计算显示,下地壳深度的该类源岩55％部分熔融形成的熔体,与腊圃花岗岩岩浆有极为相似的地球化学性质。Sr,Nd同位素成分测定表明,岩石具有较高的Isr值（0．7124～0．7155）和较低的εNd（t）值（-11．18～-11．54）,模拟计算显示,这显然是一种下地壳部分熔融的产物。

Abstract: Exposed at the south of Conghua city, Guangdong province, the Lapu amphibole- and biotite-bearing monzonitic granite occupies an area of about 500 km2. The rock is composed of calcic amphibole （0.5%）, biotite （ 11 - 13% ）, plagioclase （An35 -41,29 -31% ）, cryptoperthite （24 -31% ） and quartz （36 -37% ）, carrying some amounts of Ca-, Ti-rich minor minerals such as allanite and titanite. Based on zircon U-Pb isotopic dating, the rock emplaced at 163 ±2 Ma （mid-Jurassic）. Petrochemically, the Lapu granite is weakly peraluminous （A/ NKC = 1. 043 in average） and with higher K20 content （4.72% in average）, belonging to the high-K calcic-alkaline series. The rock has high EREE contents （（ 180 -460） × 10-6）, showing an evident LREE-enriched and HREE-depleted tendency, and with higher （La/Yb）N values （19 in average）. These features indicate that partial melting of source materials for forming Lapu magma occurred at a deeper （ lower crust） level （p 〉 10 × l0s Pa） and that garnet would be a main residual phase, which resulted in HREE depletion in the melt. According to many trac- ers for source rocks （Patino Douce, 1999）, it is suggested that the source rocks for forming Lapu magma were metagreywakes or meta-amphibolites. Analyses for Sr, Nd, Pb isotopic compositions of the Lapu granite yielded a feebly high Isr （0.7124 - 0.7155 ） and lower εNd （t） values （ - 11. 18 - - 11. 54 ）. Model calculation shows that the melt formed by 55% partial melting of the lower crust rocks would have the similar geochemical features as those of real Lapu granite magma.

刘昌实, 陈小明, 王汝成, 张爱铖, 胡欢. 下地壳部分熔融的产物：燕山早期广东腊圃花岗岩成因[J]. J4.

Liu Chang-shi, Chen Xiao-ming, Wang Ru-cheng, Zhang Ai-cheng, Hu Huan. The Products of Partial Melting of the Lower Crust： Origin of Early Yanshanian Lapu Monzogranite, Guangdong Province[J]. J4.