赣南兴国东固高分异花岗岩成因及地质意义  

Genesis of Donggu Highly Fractionated Granites,Xingguo,Southern Jiangxi,and Its Geological Significance

作　　者：舒徐洁 陈志洪[1] 朱延辉[1] 廖圣兵[1] 周博文[2] 李功振[3] 赵旭辰 刘爽 陈雷超 

机构地区：[1]南京地质矿产研究所,南京210016 [2]中国地质科学院研究生院,北京100037 [3]成都理工大学,成都610059

出　　处：《地质论评》2018年第1期108-126,共19页Geological Review

基　　金：中国地质调查局1:25W兴国幅区域地质调查修测项目(项目号12120115030101)的成果~~

摘　　要：本文对江西省兴国县东固花岗岩体进行了岩石学、全岩元素地球化学、锆石U-Pb及Lu-Hf同位素研究。研究结果表明,东固岩体中东固、雪竹坑和佛子山单元均形成于152±2Ma,为近同期岩浆作用的产物,而非前人认为属于三个不同时期,这一发现对于认识东固岩体的成因有着重要作用。东固岩体具有较高的全岩Si O2含量、Rb含量(>350μg/g),较低的Zr/Hf、Nb/Ta值,地球化学上兼有部分铝质A型花岗岩和高分异S型花岗岩的特征,其成因类型较难界定。其中白云母花岗岩单元分异程度最高,与成矿作用密切相关,已经发现的矿床多产于其中或其与围岩接触带。东固岩体中不同单元的锆石εHf(t)值均集中,佐证前人划分的不同单元可能来自于同一源区。其锆石εHf(t)值介于-9^-11之间,对应两阶段亏损地幔模式年龄为1.7~1.9 Ga,同位素特征显示其可能起源于古元古代地壳变质基底的部分熔融。结合附近存在的"裂谷型"正长岩类,我们认为东固岩体可能产生于古太平洋板块向华南板块俯冲所产生的拉张构造背景之下,高分异岩体的界定有利于后期进一步找矿工作的开展。Systematic mineralogical, whole-rock geochemistry, zircon U-Pb dating and zircon Lu-Hf isotopic compositions analysis were done on the Donggu granitic pluton. The different rock units which former named Donggu,Xuezhukeng and Fozishan unit were formed contemporary at 152±2 Ma rather than formed at different periods. Donggu pluton is characteristic with high whole rock SiO2content, Rb（ 〉350 μg/g） and low Zr/Hf, Nb/ Ta value. It has geochemical features similar to the aluminous A-type granite and highly fractionated S-type granite, which is hard to define its rock genetic type. The mica bearing granite unit has the highest differential degree and closely related to the tungsten ore. Ore deposits were found in the mica bearing units or the wall rock contact zone. The zircon εHf（t） values of Donggu pluton have narrow variations which suggest the different units of the granite probably from the same source area. Zircon eHf（t） values vary from -9 to -11 and the TEDM ages vary from 1.7-1. 9Ga, indicating the granite were formed by partial melting of the metamorphic basement. Combine with ＂rift-type＂ syenites which were found near the study area, we suggest that the Donggu pluton were formed at extensional geological background which triggered by the subduction of the paleo-Pacific plate. Determination of the highly fractionated granite is conductive to further ore deposit prospecting works.

关 键 词：高分异花岗岩 岩石成因 东固岩体 江西 

分 类 号：P588.121[天文地球—岩石学]