滇西昌宁地区西盟岩群变质变形作用研究
发布时间：2018-07-24 07:46
【摘要】：滇西昌宁地区的“西盟岩群”东与石炭纪牛井山蛇绿混杂岩(CNop)断层相接,西被燕山期花岗岩侵入接触。前人对西盟岩群的变质作用、变形作用以及它们之间的关系研究较少,本文在野外地质调查的基础上,结合室内薄片鉴定,准确研究西盟岩群的变质岩岩石类型及矿物共生组合类型;通过野外产状和岩石地球化学(全岩、稀土及微量元素)的分析测试工作,对西盟岩群进行原岩恢复并确定其原岩性质;通过矿物对的电子探针分析,确定变质作用温压条件;运用锆石U-Pb年代学测试分析,准确限定变质变形作用期次。研究区西盟岩群共划分为三个岩性段:a段以(石榴)长英质糜棱岩、变粒岩、云母(石英)片岩、黑云斜长片麻岩为主,夹少量大理岩、角闪黑云片岩等;b段以浅色变质岩为主,主要包括长英质糜棱岩、黑云斜长片麻岩、浅粒岩、石榴二云斜长片岩等;c段以黑云斜长片麻岩与长英质片麻岩互层为主,夹少量黑云片岩和花岗质片麻岩。野外地质特征结合地球化学特征表明:黑云片岩类和石英片岩类的原岩总体应为副变质岩,它们可能是由粉砂质粘土岩或泥岩变质而成;角闪黑云片岩的原岩可能是中基性火山岩;片麻岩类的原岩多数为长石砂岩,少数为中酸性岩浆岩;长英质糜棱岩类可能为中酸性的岩浆岩变质后再经韧性剪切变形改造而成。西盟岩群中两件锆石U-Pb年代学样品表明,原西盟岩群应予解体为燕山期花岗岩和中深变质岩系。变质岩系仅包括片岩类、片麻岩类、变粒岩类、大理岩类、和部分长英质糜棱岩类。西盟岩群共有三期变质作用:主期变质作用(M1)为角闪岩相的区域中温中压变质作用,其温压条件为:540±10°C,0.4±0.03GPa,变质时间为晋宁期;第二期变质作用(M2)为同变形变质作用,是绿片岩相的区域动力变质作用,其变质时间为20Ma—14Ma间的喜山期;第三期变质作用(M3)为绿片岩相的退变质作用,其时间为14Ma以后。西盟岩群共有三期变形作用:第一期变形作用(D1)为主期变质作用(M1)的同变质的变形作用,形成了区域性的片理和片麻理;第二期变形作用(D2)是主期变质作用(M1)后片理、片麻理发生扭折弯曲的变形作用;第三期变形作用(D3)为近南北向的左旋走滑剪切变形作用。
[Abstract]:The "Ximeng rock group" in Changning area of western Yunnan is connected with the (CNop) fault of Carboniferous Niujingshan ophiolite melange in the east and is intruded by Yanshanian granite in the west. There are few studies on metamorphism, deformation and their relationship between the Ximeng rock group. Based on the field geological survey, this paper combined with laboratory sheet identification, The types of metamorphic rocks and mineral symbiotic assemblages of Ximeng rock group are studied accurately, and the field occurrence and rock geochemistry (whole rock, rare earth elements and trace elements) are analyzed and tested. The original rocks of Ximeng rock group are restored and the original rock properties are determined; the temperature and pressure conditions of metamorphism are determined by electron probe analysis of mineral pairs; and the period of metamorphic deformation is accurately defined by zircon U-Pb chronological analysis. The Ximeng rock group in the study area is divided into three lithologic members: (pomegranate) felsic mylonite, granulite, mica (quartz) schist, black cloud plagioclase gneiss, and a small amount of marble. The amphibolite schist is mainly composed of light-colored metamorphic rocks, including felsic mylonite, black-cloud plagioclase gneiss, shallow-grained rock, pomegranate eryun plagioclase schist and so on. A small amount of black cloud schist and granitic gneiss. The field geological features combined with geochemical characteristics indicate that the source rocks of the black cloud schist and quartz schist should be metamorphic rocks, which may be metamorphic from silty clay rocks or mudstones. The primary rocks of hornblende schist may be intermediate basic volcanic rocks, most of gneiss are feldspar sandstone, a few are intermediate-acid magmatic rocks, and felsic mylonite may be formed by ductile shear deformation after metamorphism of intermediate-acid magmatic rocks. Two zircon U-Pb geochronological samples from the Ximuiyan Group indicate that the Proto-XIMU rock group should be disintegrated into Yanshanian granite and medium-deep metamorphic rock series. Metamorphic rocks include only schist, gneiss, granulite, marble and some felsic mylonites. There are three metamorphic stages in Ximeng rock group: the main metamorphism (M1) is a regional metamorphism of amphibolite facies, and the temperature and pressure conditions are as follows: (1) the metamorphism time is Jinning period, and the second stage metamorphism (M2) is syndesic metamorphism, and the temperature and pressure conditions are: (1) 540 卤10 掳C _ (10) 掳C _ (10) 掳C _ (0) 卤0.03 GPa. It is the regional dynamic metamorphism of the greenschist facies, whose metamorphic time is the Himalayan period between 20Ma-14Ma and the retrograde metamorphism of the greenschist facies in the third metamorphism (M3) after 14Ma. The Ximeng rock group has three stages of deformation: the first stage deformation (D1), the main metamorphism (M1), the formation of regional lithology and schism, and the second stage deformation (D2) is the main stage metamorphism (M1), and the second stage deformation (D2) is the main stage metamorphism (M1), and the second stage deformation (D2) is the main stage metamorphism (M1). The third stage deformation (D 3) is a near S N direction left lateral strike-slip shear deformation.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.3
本文编号：2140700
[Abstract]:The "Ximeng rock group" in Changning area of western Yunnan is connected with the (CNop) fault of Carboniferous Niujingshan ophiolite melange in the east and is intruded by Yanshanian granite in the west. There are few studies on metamorphism, deformation and their relationship between the Ximeng rock group. Based on the field geological survey, this paper combined with laboratory sheet identification, The types of metamorphic rocks and mineral symbiotic assemblages of Ximeng rock group are studied accurately, and the field occurrence and rock geochemistry (whole rock, rare earth elements and trace elements) are analyzed and tested. The original rocks of Ximeng rock group are restored and the original rock properties are determined; the temperature and pressure conditions of metamorphism are determined by electron probe analysis of mineral pairs; and the period of metamorphic deformation is accurately defined by zircon U-Pb chronological analysis. The Ximeng rock group in the study area is divided into three lithologic members: (pomegranate) felsic mylonite, granulite, mica (quartz) schist, black cloud plagioclase gneiss, and a small amount of marble. The amphibolite schist is mainly composed of light-colored metamorphic rocks, including felsic mylonite, black-cloud plagioclase gneiss, shallow-grained rock, pomegranate eryun plagioclase schist and so on. A small amount of black cloud schist and granitic gneiss. The field geological features combined with geochemical characteristics indicate that the source rocks of the black cloud schist and quartz schist should be metamorphic rocks, which may be metamorphic from silty clay rocks or mudstones. The primary rocks of hornblende schist may be intermediate basic volcanic rocks, most of gneiss are feldspar sandstone, a few are intermediate-acid magmatic rocks, and felsic mylonite may be formed by ductile shear deformation after metamorphism of intermediate-acid magmatic rocks. Two zircon U-Pb geochronological samples from the Ximuiyan Group indicate that the Proto-XIMU rock group should be disintegrated into Yanshanian granite and medium-deep metamorphic rock series. Metamorphic rocks include only schist, gneiss, granulite, marble and some felsic mylonites. There are three metamorphic stages in Ximeng rock group: the main metamorphism (M1) is a regional metamorphism of amphibolite facies, and the temperature and pressure conditions are as follows: (1) the metamorphism time is Jinning period, and the second stage metamorphism (M2) is syndesic metamorphism, and the temperature and pressure conditions are: (1) 540 卤10 掳C _ (10) 掳C _ (10) 掳C _ (0) 卤0.03 GPa. It is the regional dynamic metamorphism of the greenschist facies, whose metamorphic time is the Himalayan period between 20Ma-14Ma and the retrograde metamorphism of the greenschist facies in the third metamorphism (M3) after 14Ma. The Ximeng rock group has three stages of deformation: the first stage deformation (D1), the main metamorphism (M1), the formation of regional lithology and schism, and the second stage deformation (D2) is the main stage metamorphism (M1), and the second stage deformation (D2) is the main stage metamorphism (M1), and the second stage deformation (D2) is the main stage metamorphism (M1). The third stage deformation (D 3) is a near S N direction left lateral strike-slip shear deformation.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.3
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