吉林省集安县上绿水桥铝质A型花岗岩体的地球化学特征及其构造意义

Geochemical Characteristics and Tectonic Significance of the Shanglüshuiqiao Aluminous A-Type Granites Intrusive in the Ji'an Area,Jilin Province

吉林省集安县上绿水桥岩体主要岩石类型为晶洞碱长花岗岩。岩石的化学成分具有高硅(SiO2质量分数为75.94%～76.34%)、富碱(ALK质量分数为8.29%～9.63%)、高TFeO/MgO值(比值为39.6～66.1)、富钾(K2O质量分数为5.14%～5.20%,K2O/Na2O值为1.47～1.68)、低CaO和TiO2的特点;强烈亏损Ba、Sr、Ti、Nb、Ta、P,富集K、Rb、Th等亲石元素;具有右倾海鸥型的球粒陨石标准化稀土配分型式及强烈的负铕异常等。主量和微量元素研究表明,上绿水桥岩体为铝质A型花岗岩(A/CNK为0.99～1.10,A/NK为1.05～1.16)。LA-ICP-MS锆石U-Pb定年结果为(117.8±2.3)Ma,属早白垩世侵入体。岩体具有相对较低的Ce/Nb、Y/Nb、Yb/Ta值,为A1型非造山花岗岩,是华北板块东部岩石圈减薄在吉南地区的浅部地质响应。

The Shangltishuiqiao instrusion exposed in Ji＇an area of Jilin Province mainly consists of miarolitic K-feldspar granite. The granites in the Shangltishuiqiao instrusion are characterized by high SiO2 （75.94%- 76. 34%） and TFeO/MgO value （39.6 -66. 1）, enrichment in alkali（ALK = 8. 29%-9.63%）and K（K2O=5.14%-5.20%,K2O/Na2O= 1.47- 1.68）,low CaO and TiO2. On the primitive mantle--normalized spider diagrams,the granites show positive K, Rb and Th anomalies and negative Ba, Sr, Ti, Nb,Ta and P anomalies. Moreover,They have particularly intensive Eu negative anomaliesare the shallow geological response of the lithosphere thinning event of the eastern North China plate in the southern Jilin Province.