广西花岗岩微量元素特征

TRACE ELEMENT GEOCHEMISTRY OF GRANITES IN GUANGXI PROVINCE

本文阐述了广西地区不同时代、不同成因花岗岩中微量元素及其组合的丰度变化;岩浆演化及有关矿床与微量元素丰度变化的关系.

Through the analytic data of rare earth elements and 17 trace elements, this paper discusses the variations of the abundances of trace elements in granites of various ages and genetic types in Guangxi and the relations between the evolution of granitic magmas and mineratization. 1.According to a comparison of the trace element abundances with the Viuogradov values,Guangxi Province,is a geochemical region rich in W,Sn and Sc and poor in Ba and Sr. 2.From the Sibaoian stage to late Yanshanian stage,the abundances of the trace elements such as Gr,Ni,Co,V,Ti,Sc,Ba,Sr and Zn show a“W” -shaped change,being generally lower in the Xuefengian stage and early Yan- shanian stage;the abundances of trace elements such as W.Sn,Li,Be and Rb show a“saddle”-shaped change,being generally relatively high in the early Yanshanian and Caledonian(or Xuefengian)stages;the abundance of ∑REE, Pb and Nb have a general tendency to increase and the abundance of Cu has a general tendency to decrease. 3.In terms of genetic types,anatectic granites have relatvely hing abun- dances of Rb,W and Sn,i.e.“grauitophile elements”;syntectic granites have relatively high abundances of Nb,V,Ba,Sr,Ti and Cu,i.e.mainly“chalco- phile-siderophile elements”;differentiated granites have relatively high abundan- ces of Cr,Ni and Sc,mainly“siderophile elements”. 4.In terms of the comagmatic evolution,from the early to late times,the acid and alkaline components increased,while the basic components decreased. Trace elements W,Sn,Li,Be,Rb and Pb increased markedly,while Cr,Ni,Co, V,Ba,Sr,Ti,Sc Cu and Zn decreased obviously.∑REE,∑Ce/Y and δEu decreased.