诸广山南体乐洞花岗岩的地球化学特征与成因研究  

STUDIES ON THE GEOCHEMICAL CHARACTERISTICS AND GENESIS OF THE LEDONG GRANITE BATHOLITHS IN SOUTHERN ZHUGUANG MOUNTIANS

作　　者：曹豪杰 黄乐真[1] 刘国安[1] 叶永钦[1] 黄海玲 李钟枢 王小冬 许丽丽 CAO Haojie;HUANG Lezhen;LIU Guoan;YE Yongqin;HUANG Hailing LI Zhongshu;WANG Xiaodong;XU Lili(No.290 Research Institute,CNNC,Shaoguan 512029,China)

机构地区：[1]核工业二九〇研究所,广东韶关512029

出　　处：《矿物岩石》2018年第3期19-27,共9页Mineralogy and Petrology

基　　金：中国核工业集团有限公司集中研发项目(编号:LTD1602);中国地质调查局”基础性公益性地质矿产调查”所属二级项目(编号:DD20160136);中国核工业地质局铀矿勘查专项基金项目(编号:201639)

摘　　要：乐洞花岗岩位于诸广山岩体南部的北缘,其岩性主要为中粒二云母花岗岩。针对乐洞花岗岩的6件样品进行了岩石学、主量元素、微量元素、稀土元素和Sr,Nd同位素分析。主量元素方面,具有富硅(w(SiO_2)70.76%~71.90%,平均为71.63%)、富铝(A/CNK值0.97~1.14,平均为1.07)、钾大于钠(K_2O/Na_2O比值1.58~1.90,平均为1.75)等特征;富集大离子元素Rb,Th和亏损Ba,Sr,Nb,Ta,P,Ti等元素;ΣREE值(124.1×10^(-6)~244.9×10^(-6),平均值为170.3×10^(-6))较高,配分模式表现为明显的右倾型,Eu明显亏损(δEu值0.23~0.27,平均为0.25);具有低ε_(Nd)(t)值(-11.8)、较高[n(^(87)Sr)/n(^(86)Sr)]_i值(0.720 23)及古老Nd模式年龄(1 966Ma)的同位素特征;源区成分以泥质岩为主,砂质岩为次要组分。上述地球化学特征与南岭地区的S型花岗岩十分相似。指示乐洞花岗岩是在华南地块和印支地块碰撞形成的伸展构造环境中,古元古代地壳组分在减压、导水等因素的综合影响下,由变质沉积岩发生部分熔融而形成的,属于后碰撞花岗岩。The main elements,trace elements,rare earth elements, Sr and Nd isotopes of 6 samples from the Ledong middle grained monzonite in the southern granite pluton of Zhuguang Mountains are studied. It shows that the rock is rich in （w（SiO2） 70. 76%-71.90%, average 71.63%） and AI（A/CNK=0.97-1.14, average 1.07）,with high ratio of K2O/Na2O（1.58- 1.90, average 1.75）. In the aspect of trace elements,the rock is enriched in large ion elements （Rb,Th）and depleted in Ba,Sr,Nb,Ta,P and Ti. The rare earth elements in the monzonite are significantly enriched（124. 1 × 10^-6 ～244.9 × 10^-6 ,average 170.3 × 10^-6 ） ,with right-declined distribution patterns,and with obvious negative Eu anormaly （δEu=0. 23～0. 27, average 0. 25）. Analysis of isotopes reveals that the eNd （t） value is low（ - 11. 8）, [n （^87 Sr）/n （^86 Sr） ]i value is high （0. 720 23）and the Nd model age is 1 966 Ma. Source region compositions are dominated by argillaceous rock with minor sandy rocks. These geochemical features consistently indicate that Ledong granite is resulted from partial melting of metamorphic sedimentary rocks in the Paleoproterozoic crust under the influence of decompression and water diversion,and in the extensional tectonic environment during the collision between the South China and Indo China block.

关 键 词：元素和同位素地球化学 伸展构造 乐洞花岗岩 诸广山南体 

分 类 号：P581[天文地球—岩石学] P595[天文地球—地质学]