安徽铜陵鸡冠山角闪石堆积岩的岩相学和矿物学特征  

Petrographic and Mineralogical Characteristics of Hornblende Cumulate in the Jiguanshan,Tongling,Anhui Province,China

作　　者：胡乐[1] 杜杨松[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《矿物岩石地球化学通报》2016年第1期163-170,共8页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国地质调查局地质调查项目(12120113069900)

摘　　要：本文旨在探究安徽铜陵鸡冠山辉石闪长岩中角闪石堆积岩的岩相学和矿物学特征及其地质意义。岩相学研究表明,钛铁磁铁矿和磷灰石早于角闪石结晶并被角闪石包裹形成包含结构,钛铁矿与磁铁矿以固溶体分离结构共存。矿物学分析显示角闪石为具幔源特征的镁绿钙闪石和韭闪石,钛铁磁铁矿中磁铁矿Ti含量极低。地质温压计计算得出角闪石的形成压力为0.70~0.76 GPa,相当于23~25km深度,形成温度为890~975℃;钛铁矿与磁铁矿固溶体分离的平衡温度为501~613℃。综合已有研究及本次分析表明,鸡冠山角闪石堆积岩是由下地壳深位岩浆房中由底侵的碱性玄武岩浆与下地壳发生同化混染作用形成的中基性岩浆结晶分异形成,而钛铁磁铁矿的平衡是随上述的中基性岩浆侵位到地表浅部逐渐冷却在固相线下达到的,角闪石堆积岩记录了鸡冠山岩体的形成过程。This paper is to probe the petrographic and mineralogical characteristics of hornblende cumulate exposed in the Jiguanshan pyroxene diorite,Tongling,Anhui Province,as well as their geological significance. Petrographic research shows that the ilmenite-magnetite and apatite were crystallized earlier than hornblende as they occurred as inclusions in hornblende. Ilmenite and magnetite are intergrown as solid solution. Mineralogical analyses reveal that the hornblende in cumulate belongs to mantle-derived magnesiohastingist and pargasite and the magnetite has a very low Ti content. The application of relevant geothermobarometers show that the hornblende in the cumulate were formed under the pressure of 0. 70-0. 76 GPa,corresponding to the depth of 23-25 km,and the temperature of 890- 975℃. The ilmenite and magnetite were reached equilibrium at the temperature of 501-613℃. Based on data of previous studies and this paper,we conclude that the formation of hornblende cumulate was resulted from crystallization of intermediate-basic magma which was developed through the assimilation of the uplifted alkali basaltic magma from the deep magma chamber and the lower crust. The equilibrium between ilmenite and magnetite in the hornblende cumulate was finally reached under the solidus at shallow level with the gradual cooling of the above uplifted intermediate-basic magma. Therefore,the hornblende cumulate had taken note of the formation process of the Jiguanshan pyroxene diorite.

关 键 词：角闪石堆积岩 岩相学 矿物学 岩浆侵位 安徽铜陵 

分 类 号：P586[天文地球—岩石学]