胶北地体早前寒武纪重大岩浆事件、陆壳增生及演化  

Early Precambrian major magmatic events,and growth and evolution of continental crust in the Jiaobei terrane,North China Craton

作　　者：刘建辉[1] 刘福来[1] 丁正江 刘平华[1] 王舫[1] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]山东省第三地质矿产勘查院,烟台264000

出　　处：《岩石学报》2015年第10期2942-2958,共17页Acta Petrologica Sinica

基　　金：国家自然科学重点基金项目(41430210);科技部973项目(2012CB416603);中国地质科学院地质研究所基本科研业务经费(J1404;J1214;J1005);中国地质调查局地质大调查项目(12120114061901;1212011120150)联合资助

摘　　要：早前寒武纪重大岩浆事件是早期陆壳增生及演化的主要地质作用。本文通过系统总结最近几年胶北地体早前寒武纪重大岩浆事件代表性岩石的岩相学、锆石U-Pb年代学、岩石地球化学及锆石Hf同位素研究的最新成果,厘定出太古宙～2.9Ga、2.7Ga及2.5Ga三期以TTGs岩浆事件为代表的陆壳增生事件。这些TTGs具有典型太古宙高铝TTGs的地球化学特征及正的εHf（t）值,锆石Hf模式年龄主要集中在ca.3.2～2.7Ga。两种不同的构造模式被用来理解胶北太古宙TTGs（陆壳）的成因：（1）加厚基性下地壳的部分熔融;（2）俯冲洋壳的部分熔融。根据胶北TTGs在时间上呈事件性侵位,空间上呈面状分布,以及相对较低的Mg#、Cr及Ni含量,前者可能更适合胶北TTGs的成因。确定了胶北古元古代2.2～2.0Ga黑云母/角闪石二长花岗片麻岩及～1.8Ga以二长（正长）花岗岩为代表的多期陆壳重熔事件。综合这些研究结果,初步总结出胶北早前寒武纪陆壳形成及演化历史：1）〉2.9Ga,主要为基性地壳（洋壳）的增生,并可能存在规模有限的、被剥蚀殆尽的太古宙早期陆壳;2）在～2.9Ga、～2.7Ga及～2.5Ga,由于地幔（热）柱上涌,ca.3.3～2.7Ga新生的加厚基性玄武质下地壳发生事件性部分熔融,并伴随有早期陆壳的重熔,形成主要由TTGs及少量陆壳重熔型（高钾）花岗岩组成的太古宙陆壳;3）ca.2.2～2.0Ga,可能由于地幔物质上涌,陆壳伸展,形成裂谷,陆壳物质重熔,形成ca.2.2～2.0Ga花岗质岩石;4）ca.1.95～1.85Ga,发生强烈的挤压碰撞构造作用,裂谷闭合,卷入挤压作用的物质发生高角闪岩相到高压麻粒岩相变质;5）～1.8Ga,地幔物质上涌,陆壳伸展减薄,陆壳物质重熔,形成～1.8Ga花岗岩。Early Precambrian major magmatic events are important geological processes of early growth and evolution of early continental crust. In this paper, we systematically summarized the studies on the petrography, zircon U-Pb geochronology, geochemistry and zircon Hf isotope for representative rocks of the Early Precambrian major magmatic events in the Jiaobei terrane. We defined three stages of Archean continental crustal growth by TrGs magmatisms at -- 2.9Ga, 2. 7Ga and 2. 5Ga, respectively. The TrGs are of geochemical characteristics of typical high-A1 TTGs. They have positive zircon zHf （t） values, and two-stage Hf model ages clustering at ca. 3. 3-- 2.7Ga- Two alternative tectonic models are proposed to account for petrogenesis of the TTGs ： （ 1 ） partial melting of thickened mafic lower crust; or （2） partial melting of oceanic crust during slab subduction. Nevertheless, the first one might be more appropriate for the Arcbean TTGs on the base of temporally episodic emplacements, spatially planar distribution, and low Mg~ number, Cr and Ni concentrations of the TTGs. We confirmed that there are multi-stage Paleoproterozoic granitic magmatisms by remelting of continental crust. By synthesizing the previous researches, we summarize that the growth and evolutional history of Early Precambrian continental crust in the Jiaobei terrane is following： 1 ） 〉 - 2. 9Ga, the Jiabei terrane were dominated by basic crust （oceanic crust） with limited Early Archean continental crust which had been denuded; 2） At-- 2. 9Ga, 2. 7Ga and 2. 5Ga, the ca. 3.3 --2. 7Ga juvenile thickened basaltic lower crust experienced episodic partial melting companied with remelting of continental crust triggered by upwelling of mantle plume, and formed the Archean continental crust consisting of plenty of TrGs and minor continental crust-remelted （high K） granites; 3） During ca. 2.2 -- 2. 0Ga, the continental crust took place rifting and thinning caused by upwelling of mantle materials, resulting in formation of ca. 2.

关 键 词：胶北地体 早前寒武纪地质 陆壳增生 太古宙TTGs片麻岩 华北克拉通 

分 类 号：P581[天文地球—岩石学]