滇西云龙漕涧地区高压片麻岩的发现及厘定
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P588.34+5

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国家自然科学基金特提斯重大研究计划重点项目(92055207);国家自然科学基金地区基金项目(420602005);中国地质调查局地质调查项目(DD20160345-02;1212010000150007-26);云南省地勘基金项目(D201901)


The discovery and determination of high-pressure gneiss in Caojian area of Yunlong, western Yunnan Province
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    摘要:

    笔者在滇西云龙县漕涧新发现了一套以黑云斜长片麻岩为主的变泥质岩石,其呈构造透镜体状产出,出露面积极小,中高级变质矿物发育,与围岩特征明显不同。岩相学研究表明,片麻岩保留有明显的俯冲-折返的矿物学记录,矿物世代具顺时针变质演化特征,其中还残存有蓝晶石+铝直闪石的共生矿物组合,对应的变质压力达1.0 GPa以上。通过GBP平均温压计法计算得到岩石的变质温压范围为566~623℃和0.36~0.53 GPa;此外,片麻岩中还有少量的多硅白云母矿物,根据相平衡模拟p-T视剖面图及其硅原子数最大值为3.23的特点,推断其属蓝片岩类。综合研究认为,黑云斜长片麻岩属于高压变质岩(峰期变质压力最小约为1.60 GPa),为昌宁-孟连结合带的北段寻找高压变质岩提供了新的信息,并表明昌宁-孟连结合带为一条连续的高压-超高压变质带。

    Abstract:

    A set of meta-argillaceous rocks mainly composed of biotite plagioclase gneiss have been newly discovered in Caojian, Yunlong County, western Yunnan Province, which are existent in the form of structural lenses, with small outcrops and well-developed medium-high metamorphic minerals, which is obviously different from the feature of surrounding rocks. Petrographic study shows that gneiss has obvious mineralogical records of subduction-exhumation, and there is also a paragenetic mineral assemblage of kyanite+aluminum amphibole, and the corresponding metamorphic pressure should have reached 1.0 GPa or higher. The metamorphic temperature and pressure of rocks calculated by GBP average temperature and pressure meter method are 566~623℃ and 0.36~0.53 GPa respectively. In addition, there is a small amount of siliceous muscovite minerals in gneiss. According to the p-T visual profile of phase equilibrium simulation and the characteristics of its maximum silicon atomic weight of 3.23, it is inferred that the rock belongs to blueschist. According to the comprehensive study, the biotite plagioclase gneiss belongs to high-pressure metamorphic rocks (the minimum metamorphic pressure in peak period is about 1.60 GPa), and these data provide new information in search for high-pressure metamorphic rocks in the northern part of Changning-Menglian junction zone, and also show that Changning-Menglian junction zone is a continuous high-pressure and ultrahigh-pressure metamorphic zone.

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黄亮,田素梅,张虎,熊波,王晓林,浦涛,杨仕潘,方雄,2021,滇西云龙漕涧地区高压片麻岩的发现及厘定[J].岩石矿物学杂志,40(4):747~756.

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  • 收稿日期:2020-10-23
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  • 在线发布日期: 2021-07-16
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