胶西北丛家岩体岩石成因探讨——岩石地球化学、年代学和Sr—Nd同位素的证据  

Petrogenesis of Congjia granodiorite in northwestern Jiaodong Penisula——Constraints from geochemistry,chronology and Sr-Nd isotopes

作　　者：迟乃杰 于学峰 孙雨沁 马祥县 张伟 张晨西 申颖 李敏 郭广军 徐珺 CHI Naijie;YU Xuefeng;SUN Yuqin;MA Xiangxian;ZHANG Wei;ZHANG Chenxi;SHEN Ying;LI Min;GUO Guangjun;XU Jun(Shandong Institute of Geological Sciences,Key Laboratonry of Gold Mineralization Processes and Resource Utilization,MNR,Shandong Provincial Key Laboratory of Metallogenic Geological Process and Resource Utilization,Jinan,250013;College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao,Shandong,266590)

机构地区：[1]山东省地质科学研究院自然资源部金矿成矿过程与资源利用重点实验室,山东省金属矿产成矿地质过程与资源利用重点实验室,济南250013 [2]山东科技大学地球科学与工程学院,山东青岛266590

出　　处：《地质论评》2023年第6期2141-2157,共17页Geological Review

基　　金：国家自然科学基金资助项目(编号:42272104);山东省自然科学基金资助项目(编号:ZR2019PD019);省部级重点实验室开放课题(编号:kfkt201810)的成果。

摘　　要：胶东地区大规模金成矿作用与中生代郭家岭期岩浆活动关系紧密,但针对胶东郭家岭期岩浆岩体的成因仍存在不同认识。笔者等选择焦家金矿带北段与金矿具有时空关系的郭家岭期丛家岩体作为研究对象,开展系统岩相学、地球化学、LA-MC-ICP-MS锆石U-Pb年代学及Sr—Nd同位素研究。丛家岩体花岗岩的Na_(2)O/K_(2)O分别为0.69~1.23,Na_(2)O+K_(2)O值为7.29%~9.58%,A/CNK值为1.39~1.51,为高钾钙碱性系列过铝质花岗岩;丛家岩体具有轻稀土富集、重稀土亏损、负铕异常(0.41~0.68)、大离子亲石元素Ba、Sr等富集、Nb、Ta、Ti等高场强元素亏损、以及高Sr/Y值(81.59~235.5)等岩石地球化学特征;丛家岩体锆石LA-MC-ICP-MS的U-Pb年龄为126.1±0.3 Ma,可以代表丛家岩体结晶年龄;岩体n(^(87)Sr)/n(^(86)Sr)值为0.711463,其低于地壳的平均值(0.7170),高于地幔的平均值(0.7090),表明其有幔源物质的参与;[n(^(87)Sr)/n(^(86)Sr)]i为0.711117,ε_(Nd)(t)的值为-17.14,亏损地幔模式年龄(TDM2)为3396 Ma。综合分析成因为幔源基性岩浆与下地壳重熔中酸性岩浆发生混合而成,并在上侵过程中受到玲珑期花岗岩的同化混染,是典型幔源物质直接参与混合的壳幔混合成因的花岗岩。The large-scale gold mineralization in the Jiaodong area is closely related to the Mesozoic Guojialing magmatic activity,but the origin of the Guojialing magma is still controversial.This paper,the Guojialing Congjia pluton,which has a time—space relationship with the gold deposit in the northern part of the Jiaojia gold belt,isselected as the research object.Petrography,geochemistry,LA-MC-ICP-MS zircon U-Pb chronology and Sr—Nd isotope studies are carried out.The Na_(2)O/K_(2)O values of Congjia granite are 0.69~1.23,the Na_(2)O+K_(2)O values 7.29%~9.58%,and the A/CNK values 1.39~1.51,which are peraluminous granites of high potassium calc alkaline series.Congjia pluton is characterized by enrichment of LREE,depletion of HREE,negative Eu anomaly(0.41~0.68),enrichment of LILE such as Ba and Sr,depletion of HFSE such as Nb,Ta and Ti,and high Sr/Y ratio(81.59~235.48).The zircon U-Pb age is 126.07±0.3 Ma,which can represent the crystallization age of Congjia pluton.The^(87)Sr/^(86)Sr value is 0.711463,indicating the participation of mantle derived materials.[n(^(87)Sr)/n(^(86)Sr)]i is 0.711117,ε_(Nd)(t)is-17.14,TDM2 is 3396 Ma.Based on analysis,the granite is formed by the mixing of mantle derived basic magma and acidic magma during the remelting of the lower crust.The magma is assimilated and contaminated by Linglong granite during the upwelling process.It is a typical granite formed by the direct participation of mantle derived materials in the mixing of crust and mantle.

关 键 词：丛家岩体 岩石成因 锆石U-PB Sr—Nd同位素 胶东 

分 类 号：P587[天文地球—岩石学] P597.3[天文地球—地质学]