透辉石—锥辉石在交代岩中形成的物理化学条件  

PHYSICO-CHEMICAL CONDITIONS FOR THE FORMATION OF THE DIOPSIDE-ACMITE PARAGENESIS IN METASOMATIC ROCKS

作　　者：梁祥济[1] 曲国林[2] 林月英[2] Liang Xiangji;Qu Guolin;Lin Yueyeng

机构地区：[1]中国地质科学院地质研究所 [2]中国地质科学院矿床地质研究所

出　　处：《岩矿测试》1983年第1期35-43,I0003,共10页Rock and Mineral Analysis

摘　　要：透辉石是岩浆岩、变质岩和交代岩中最常见的矿物之一。锥辉石在一些传统的矿物学书中都归入霓石一栏内,笼统地谈到产在碱性岩中。但是,锥辉石产出比霓石广的多。原生锥辉石在美国科罗拉多、怀俄明和犹他州Green—River的一些岩系中普遍可见,它还可在蚀变的含铁片岩和角页岩中出现,有的还产在含有Na、Fe的蚀变围岩之中,它的产出与辉石和闪石类矿物密切相关。然而,透辉石—锥辉石这一对矿物作为气成高温蚀变产物究竟在什么样的物理化学条件下共存呢?它们又与哪些矿物密切共生呢?这是本文将要论及的问题。Diopside-acmite is a pair of coexistent minerals in a solid solution which dissolves imperfectly. Sometimes they are associated with each other in meta-somatic rocks. But under what physico-chemical conditions can this pair of minerals actually occur together? Author has summarized the experimental data on the diopside-acmite paragenesis obtained from the modeling of the formation of the Makeng iron deposit, which is undoubtedly significant for the study of the formation of this pair of minerals. Author used natural diabasa and marble as starting test materials.The experiments were carried out in a cold-seal high-pressure vessel with a gold lining. The experimental results show that the diopside-acmite paragenesis is formed within the range of 90% diabase and 10% marble to 50% diabase and 50% mar-ble,under the temperature of 500-650℃ and the pressure of 500 - 650 bar.,and in a nearly neutral medium of XCO2 = 0.0104 -0.002 within the H2O-CO2 fluid. Some of the diopside-acmite solid solution produced in our tests has a perfect crystal form;It is found that in this solid solution, the diopside is always more and the acmite less.This pair of minerals is often associated with garnet, tremolite, vesuvianite, and magnetite, etc. Because of the small ranges of temperature, pressure, pH of the medium solution and XCO2 for the coexistence of this pair of minerals, they seidom occur together in metasomatic rocks in nature.

关 键 词：物理化学条件 角页岩 交代岩 透辉石 美国科罗拉多 碱性岩 锥辉石 岩系 

分 类 号：P61[天文地球—矿床学]