赣南寨背A型花岗岩体的地球化学特征及其构造地质意义  

Geochemical Characteristics and Tectonic Implication of Zhaibei A type Granitic Intrusives in South Jiangxi Province

作　　者：陈培荣[1] 章邦桐[1] 孔兴功[1] 蔡笔聪 凌洪飞[1] 倪琦生[1] 

机构地区：[1]南京大学内生金属矿床机制研究国家重点实验室

出　　处：《岩石学报》1998年第3期289-298,共10页Acta Petrologica Sinica

基　　金：国家自然科学基金

摘　　要：赣南寨背岩体主要为黑云母钾长花岗岩，黑云母结晶晚于长石和石英，锆石群型地温测量标尺显示其结晶温度为８００℃～９００℃，表明寨背岩体形成于一种高温贫水的花岗质岩浆。岩石的化学成分特点为准铝质（Ａｌ２Ｏ３为１２．２１％～１２．６２％），富硅（ＳｉＯ２为７５．６６％～７６．７４％），偏碱（Ｎａ２Ｏ＋Ｋ２Ｏ为７．９３％～８．９０％），ＦｅＯＴ／ＭｇＯ值高（５９～１４８），ＣａＯ和ＭｇＯ含量低（分别为０．１０％～０．６５％和０．０１％～０．０２％），富含ＲＥＥ（Ｅｕ除外，ΣＲＥＥ平均为５００μｇ／ｇ），Ｙ、Ｇａ、Ｎｂ等高场强元素（ＨＦＳＥ）以及Ｆ，Ｓｒ和Ｂａ较低。这些特点与本区的Ｉ型和Ｓ型花岗岩有明显差别，是一种典型的Ａ２型花岗岩。寨背岩体Ｒｂ－Ｓｒ等时线年龄为１７６Ｍａ，与辉长岩、双峰式火山岩有密切的时空关系，表明赣南地区在燕山早期即进入拉张裂解阶段。Zhaibei intrusive in southern Jiangxi province mainly consists of biotite potassium feldspar granites .It is suggested that Zhaibei intrusive derived from an anhydrous granitic magma of high temperature, because biotite crystallization is after feldspars and quartzs, and zircon at 800℃～900℃ by a geothermometric scale of zircon populations. The granites of Zhaibei intrusive are metaluminous(Al 2O 3=12 21%～12 62%) and characterized by high SiO 2(75 66%～76 74%),K 2O+Na 2O(7 93%～8 90%), FeO T/MgO radio(59～148),REE(except Eu,ΣREE average value is 500μg/g),Y,Ga,Nb and F,and low CaO(0 10%～0 65%),MgO(0 01%～0 02%),Sr and Ba. The characteristics are very different from those observed for I and S type granites in southern Jiangxi province, but quite similar to those of A2 or PA type granites. Zhaibei intrusive,which obtains a Rb Sr isochron age of 176 Ma ,is closely related to gabbros and bimodal volcanic rocks in time and space .Therefore,it is suggested that crustal rifting might start in the period of early Yanshanian movement in southern Jiangxi Province.

关 键 词：花岗岩 A型花岗岩体 地球化学 构造地质意义 

分 类 号：P588.121[天文地球—岩石学]