山东即墨马连山地区新元古代花岗质片麻岩捕掳体的发现及其地质意义  

The discovery of Neo Proterozoic granitic gneiss xenolith in Malianshan of Jimo, Shandong province, and its geological significance

作　　者：侯建华[1] 任天龙[1] 杨仕鹏[1] 朱学强[1] 郭晶[1] 黄永波[1] 

机构地区：[1]山东省地质调查院,济南250013

出　　处：《地质调查与研究》2016年第2期81-88,共8页Geological Survey and Research

基　　金：中国地质调查局工作项目"山东1/5万即墨等5幅区域地质调查(1212011120749)";"山东省地质系列图件编制和综合研究(1212010811029)"

摘　　要：在苏鲁造山带中段即墨马连山地区新发现的花岗质片麻岩组合,为亚铝质-弱过铝质高钾钙碱性花岗岩类。呈捕掳体形体赋存于中生代崂山花岗岩中,普遍含有大理岩、变粒岩、片岩类等表壳岩包体。采用LA-MC-ICPMS技术,对岩石中的锆石进行了U-Pb同位素测定,测得黑云二长花岗质片麻岩样品(D04)的206Pb/238U年龄,其中15个数据的加权平均值为770.2±2.4 Ma(n=15,MSWD=0.14),该年龄解释为原岩的形成时代。含石榴二长花岗质片麻岩样品(D0501)的206Pb/238U年龄为784.3±6.6 Ma和930±5 Ma,其中8个数据的加权平均值为784.3±6.6 Ma(n=8,MSWD=0.39),该年龄解释为原岩的形成时代;12个数据的加权平均值为930±5 Ma(n=12,MSWD=0.65),该年龄解释为早期残留锆石年龄。该套岩石形成于新元古代中期,其岩石特征、岩石化学特征与胶南月季山片麻岩及胶北高钾I型花岗质片麻岩相似,属苏鲁造山带基底岩系。该套岩石组合类型的新发现为造山带北段西边界的研究提供了新的依据。The large-scale granitic gneiss xenolithes were first discovered in Laoshan series granites at the middle part of the Sulu orogen, Malianshan Jimo area. And they generally captures the supracrustal rock inclusion such as marble, granulite, schist and so on. The granitic gneiss belongs to subaluminous-weakly peraluminous high-k calc-alkaline granitoid. By using the method of LA-MC-ICP-MS to measure the U-Pb isotope of zircon, shows that the206Pb/238 U age of biotite granite-gneiss（D04） is 770.2±2.4 Ma（n=15, MSWD=0.14）which is the age of the protolith. The weighted average of206Pb/238 U ages from garnetiferous granite- gneiss（D0501） are 784.3 ± 6.6Ma and 930±5 Ma, separately representative the age of the protolith and relict zircon.The LA-MC-ICP-MS zircon U-Pb dating shows that it was formed in the Mid Neoproterozoic. According to the features of petrological and lithogeochemical analyis, and compare with the Yuejishan gneiss and I type granitic gneiss of Jiaobei, it is suggested that the granitic gneiss belongs to the fundamental series of the Sulo orogenic belt. So, the discovery of granitic gneiss provides a new direct field evidence to study the western boundary of the north Sulu orogenic belt.

关 键 词：花岗质片麻岩 新元古代 苏鲁造山带 锆石U-PB LA-MC-ICP-MS 

分 类 号：P588.345[天文地球—岩石学]