区域地球化学不均一性起因初探——以吕梁中条古元古代裂谷带为例  

A Preliminary Discussion about Origin of Geochemical Heterogeneity--An Example from Luliang-Zhongtiao Paleoproterozoic Rift

作　　者：刘建忠[1] 欧阳自远[1] 

机构地区：[1]中国科学院国家天文台

出　　处：《矿物岩石地球化学通报》2003年第1期1-7,共7页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国科学院知识创新工程项目(KZCX1 07);中国科学院院长基金特别资助项目;中国科学院地球化学研究所所长择优选择基金项目的资助

摘　　要：研究表明,现代地幔的化学和同位素具有明显的横向及纵向不均一性,且这种不均一性在太古宙就已存在;目前,对于地球化学不均一性起因的争论仍然非常激烈,为此本文选定华北克拉通中部的吕梁 中条裂谷带进行深入探讨。该裂谷带形成于古元古代,尽管其中的岩石建造生成于相同的大地构造背景,经历了相同的构造、热事件的改造,但在不同空间位置上,其岩石建造从老到新存在系统的地球化学特征的差异,说明这种地球化学差异性应是对源区地球化学特征的继承,后期的改造并没有对其进行明显的改造,更进一步说明区域地球化学不均一性是对源区不均一性的继承,区域地球化学不均一性起源于初始不均一性。从而表明后期的地质过程对岩石化学组成的影响与其初始组成对其控制作用相比,明显处于次要地位。The study on geology and geochemistry indicates that chemistry and isotope of mantle and crust are heterogenetic. In order to discuss the origin of the geochemical heterogeneity, this paper chooses the LuliangZhongtiao rift as a object of study. After carefully analyzing the data of regional geology, geochemistry and chronology, it was found out that although the metamorphic volcanic rocks in the basement formed 500-600 million years earlier than their overlying rocks the metamorphic volcanic rocks in Paleoproterozoic still inherited the geochemical characters of old rocks. Especially,some trace elements in the two kinds of rocks have the similar geochemical characters even though they experienced a series of different metamorphic & deformation processes. It means that with time and structural environment changing, the trace element and isotope compositions of the rocks at one place keep constant, and the new rocks inherited the geochemical characters of old rocks, in other words, the geochemical characters of new rocks reflect that of old rocks. But in different places, from the basement to its overlying middle Proterozoic subera rocks, especially for the rift valleys formation of Paleoproterozoic located in the same rift and formed at the same stage, the systematic difference in the geochemical characters was showed.As stated above, the difference of geochemistry is inherited from that of the original position, the later reform has little effect on it. This confirms that the regional geochemical heterogeneity is inherited from the heterogeneity of original area. Regional geochemical heterogeneity is caused by its initial inhomogeneities. Therefore, compared to the initial composition, the succedent geological events produced little influence on the chemical composition of rocks. Further, three sets of metamorphic supercrust rocks formed at different periods and tectonic backgrounds in the north part of Jidong area in North China, and two sets of metamorphic supercrustal rocks in the south part of Xi

关 键 词：区域地球化学 不均一性 古元古代 吕梁-中条裂谷带 岩石建造 大地构造 岩石化学 

分 类 号：P596[天文地球—地球化学]