赣东北蛇绿岩中的埃达克型花岗岩——地球化学和Nd同位素证据

赣东北蛇绿岩中的埃达克型花岗岩——地球化学和Nd同位素证据

李武显, 李献华

中国科学院广州地球化学研究所，广州 510640

收稿日期:2004-06-20 修回日期:2004-06-20 出版日期:2004-06-20 发布日期:2004-06-20

Adakitic Granites within the NE Jiangxi Ophiolites，South China Geochemical and Nd Isotopic Evidence

LI Wu-xian, LI Xian-hua

Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China

Received:2004-06-20 Revised:2004-06-20 Online:2004-06-20 Published:2004-06-20

摘要/Abstract

摘要： 报道了赣东北蛇绿岩中西湾钠长花岗岩的地球化学和Nd同位素研究结果，它的许多特征与现代环太平洋地区的埃达克岩(Adakite)极为相似，包括高Al2O3(15％～17％)，Sr(383×10^-6～920×10^-6)和Sr／Y(166～444)，低HREE(Yb=0．14×10^-6～0．21×10^-6)和Y(1．66×10^-6～2．81×10^-6)以及高εNd(t)值(+4．9～+6．9)。与现代典型埃达克岩的差异仅在西湾钠长花岗岩具有异常高的Na2O／K2O(12～37)，Na2O／CaO(2．7～3．6)比值和异常低的MREE(Sm=0．6×10^-6～1．2×10^-6)和HREE含量。上述地球化学特征表明，西湾钠长花岗岩为俯冲的细碧岩化的洋壳玄武岩(MORB)在高压条件下小比例部分熔融形成，源区残留矿物相有较大比例的角闪石和石榴石，而缺少斜长石。这种形成过程类似于现代的埃达克岩的成因。

Abstract: The geochemistry and Nd isotope compositions of Xiwan albite gmaites within NE jiangxi ophiolites were reported in this paper．The granites share some geochemical similarities with modem adakite，including high Al203(15％～17％)，Sr(383 x 10-6～920 x 10-6)，Sr／Y(166～444)and high εNd(t)values(+4．9～+6．0)．Compared with the typical adakites，these granites are lower in HREE(Yb：0．14×1O-6～0．21×10-6)，MREE(Sm=0．6 x 10-6～1．2 x 10-6)and Y(1．66 x 10-6～2．81 x 10-6)contents but higher in Na20／K20(12～37)and Na20／CaO(2．7～3．6)ratios．Geological and geochemical features suggest that they were generated by lower degree of partial melting of subducting spillitized oceanic crest at pressure high enough to stabilize garnet and amphibole but the plagioclase absent．The scenario is similar to the formation of the modem adakite in circum-Pacific margin．

李武显, 李献华. 赣东北蛇绿岩中的埃达克型花岗岩——地球化学和Nd同位素证据[J]. J4.

LI Wu-xian, LI Xian-hua. Adakitic Granites within the NE Jiangxi Ophiolites，South China Geochemical and Nd Isotopic Evidence [J]. J4.