滇西双江县勐库地区退变质榴辉岩中闪石类矿物的成因研究

发布时间：2018-03-15 12:42

  本文选题：闪石类矿物　切入点：退变质榴辉岩　出处：《岩石矿物学杂志》2017年01期 　论文类型：期刊论文

【摘要】：勐库地区新近发现的退变质榴辉岩中晚期退变质作用形成的闪石类矿物十分丰富,其携带了大量晚期退变质过程中的岩石成因信息。本文通过系统的矿物学研究,鉴定出了3期10种闪石类矿物,其中以镁钙闪石、镁角闪石、铁镁钙闪石、铁韭闪石、透闪石、阳起石等钙质闪石类为主,有少量冻蓝闪石、蓝透闪石等钠-钙闪石类。研究发现,随着退变质过程中时间的推移,角闪石的形成环境逐渐由还原环境向弱氧化环境、氧化环境演变。根据角闪石电子探针成分测试结果计算了相应的温度、压力条件。结合岩相学的资料,将退变质过程分为3期:(1)第1期早阶段为近等温降压过程(p=0.56~0.75 GPa,t=642~709℃),主要形成铁韭闪石、铁镁钙闪石、镁钙闪石;晚阶段为等温降压过程(p=0.39~0.56 GPa,t=619~642℃),主要形成镁钙闪石及少量镁绿钙闪石、铁韭闪石;(2)第2期为降温降压过程(p=0.23~0.42 GPa,t=460~610℃),主要形成镁角闪石、冻蓝闪石及铁角闪石;(3)第3期为近等温降压过程(p=0.09~0.31 GPa,t=350~420℃),主要形成透闪石、阳起石、蓝透闪石等。闪石类的成分变化反映了退变质榴辉岩从地壳底部的角闪石榴辉岩-高压麻粒岩相温压环境向中上地壳角闪岩相、绿片岩相温压环境的渐次退变质作用过程。这与昌宁-孟连构造带上印支期的碰撞造山作用、燕山期的区域性地壳伸展、喜马拉雅期的陆内造山运动具有较好的对应关系。
[Abstract]:The amphibole minerals formed by the late retrograde metamorphism of retrograde eclogite discovered recently in Mengku area are very rich and carry a large amount of petrogenetic information during the late retrograde metamorphism. In this paper, a systematic mineralogical study is carried out. Ten kinds of amphibole minerals were identified in three periods, among them, magnesium calcite, magnesium hornblende, ferric calcium amphibole, leek amphibole, tremolite, actinolite and other calcareous amphiboles, with a small amount of frozen blue amphibole, were identified. The study shows that with the time of retrograde metamorphism, the environment of hornblende formation gradually changes from reducing environment to weak oxidation environment. Evolution of the oxidation environment. The corresponding temperature and pressure conditions have been calculated based on the results of the amphibole electron probe composition test. Combined with petrographic data, The retrograde metamorphic process is divided into 3 stages: 1) the first stage is a near isothermal depressurization process, the first stage is a near isothermal depressurization process, the first stage is a near isothermal depressurization process, and the main formation of the retrograde metamorphic process is amphibole, ferromagnesium-calcium amphibole and magnesium-calcium amphibole. In the late stage, the isothermal depressurization process was 0.39 ~ 0.56 GPat ~ (619) ~ (642 鈩，

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