华北克拉通～2.5Ga地壳再造事件:来自中条山TTG质片麻岩的证据  

Crustal reworking in the North China Craton at ～ 2.5Ga:Evidence from zircon UPb ages,Hf isotopes and whole-rock geochemistry of the TTG gneisses in the Zhongtiao Mountain

作　　者：张瑞英[1] 张成立[1] 孙勇[1] 

机构地区：[1]大陆动力学国家重点实验室,西北大学地质学系,西安710069

出　　处：《岩石学报》2013年第7期2265-2280,共16页Acta Petrologica Sinica

基　　金：国家"973"项目(2012CB416606);西北大学大陆动力学国家重点实验室科技部专项联合资助

摘　　要：华北克拉通中部中条山区涑水杂岩是华北克拉通新太古代TTG质片麻岩地体之一。为了探讨华北克拉通新太古代构造-岩浆事件的性质及早前寒武纪地壳的形成和演化,选择涑水杂岩中TTG质岩石进行研究。研究表明这套TTG质岩石富Na、高Al、Sr,低Y、Cr、Ni含量。稀土元素配分曲线右倾,富Rb、Ba等大离子亲石元素,强烈亏损Nb、Ta等高场强元素。LA-ICP-MS锆石U-Pb定年结果表明,这套TTG质片麻岩形成于2553～2561Ma,属新太古代晚期产物。锆石Lu-Hf同位素分析结果显示εHf(t)为正值,两阶段模式年龄集中在2.7～2.8Ga。结合涑水杂岩中TTG质片麻岩的岩石地球化学特征,认为这套TTG片麻岩可能主要来自2.7～2.8Ga的下地壳镁铁质岩石在新太古代晚期的部分熔融,可能有少量的地幔物质加入。考虑同期发育大量花岗质岩石的事实,说明新太古代晚期在华北克拉通中部并不存在大规模的俯冲作用,华北克拉通在新太古代晚期已经基本成型。结合前人研究成果和本文锆石Lu-Hf同位素分析结果,提出中条山区～2.5Ga岩浆事件代表一期重要的陆壳再造事件。The Sushui Complex in the Zhongtiao Mountain,located in the central NCC,is one of the reprehensive TTG gneisses in Late Archaean of North China Craton.In order to study the tectono-magmatic thermal event of the North China Craton during Late Archaean and the formation and evolution of the Early Precambrian continental crust,we choose the TTG gneisses of Sushui complex as the research object.The results show that the TTG gneisses are characterized by high Na,Al and Sr contents,but low Y,Cr,Ni contents.The TTG rocks are rich in LREE,and chondrite normalized REE patterns are characterized by right inclining type.And their trace elements display the features of enrichment of large ion lithophile elements （such as Rb and Ba） and strongly depleted in high field strength elements （Nb and Ta）.LA-ICP-MS zircon U-Pb age data indicate that the rocks formed within the range of 2553 ～ 2561Ma,so their formation age is restricted at Late Archaean.In-situ zircon Lu-Hf isotopic analyses show that they have positive ε Hf （t） values and the corresponding two-stage model age are mainly between 2.7Ga and 2.8Ga.According to geochemical characteristics of TTG gneisses in Sushui Complex,we can conjecture that their magmatic origin was mainly related to the partial melting of 2.7 ～ 2.8Ga basaltic lower crust at the end of Neoarchaean,and contaminated by a few mantle sourced materials.With the fact of the widely distributed granitic rocks in the NCC,we hold that there was no proof of large-scale subduction process in the central NCC and the North China Craton should have been formed in Late Archaean.Based on the zircon Lu-Hf isotopic analyses in this article and previous research results,we consider that the magmatic event in ～ 2.5Ga in the Zhongtiao Mountain represents a major event of crustal reworking.

关 键 词：涑水杂岩 TTG片麻岩 ~2 5Ga岩浆热事件 地壳再造 华北克拉通 

分 类 号：P588.12[天文地球—岩石学]