滇西点苍山杂岩的组成与构造特点
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摘要
点苍山变质杂岩体作为红河-哀牢山韧性剪切带上一个具有重要意义的变质杂岩体,其与众不同的出露位置和出露特点受到众多地质学家们的关注。
本文从几个方面对点苍山变质杂岩体进行了观察和研究。1)点苍山变质杂岩体东、西两部分的宏观构造变形与组成特点的测量和观察;2)点苍山东、西两部分发育不同的变质岩组合规律和变质矿物组成特点的观察和总结。研究结果显示,点苍山变质杂岩体的主体,分属两个构造单元,即西部到中部的中深变质岩带和东部叠加的退变质岩带。其中主要的深变质岩带主要是由达高绿片岩相到角闪岩相的变质岩岩石组合而成,岩石普遍遭受强烈的左行走滑剪切变形改造,东部由1500m厚的退变质岩石构成,主要是一套绿片岩相叠加的变质岩带和花岗质糜棱岩组合而成的杂岩。3)对长石斑晶的变形行为的认识和总结,点苍山的长石斑晶分为“硬残斑”和“软残斑”两种类型。“软残斑”又分为两种状态,一种长石残斑具有明显的拖拽现象呈σ、δ、Φ形产出,另外一种长石残斑呈条带状、条纹状,条痕状产出。4)本文试图通过了解点苍山变质杂岩、及其周边地质体的构造特点,以期正确理解它们对点苍山变质杂岩体剥露的作用和意义。
点苍山变质杂岩体东、西两部分岩石保存了不同的显微构造现象,是由微观尺度不同特点的变质与变形作用所致。点苍山花岗质糜棱岩中赋存了亚晶粒旋转动态重结晶,出溶构造,双晶扭折,显微分层现象,条带状构造,书斜式构造等典型的晶质塑性变形与脆-韧性转变变形作用的证据。并对点苍山东西两部分岩石在显微尺度下所表现出来的不同的显微构造现象进行了观察和总结。在显微尺度下点苍山西坡的岩石表现出了高温塑性变形的证据,而在点苍山东坡岩石主要表现的是一种韧-脆性过度的一种显微表现。无论是在显微尺度还是宏观尺度上都反映了点苍山变质杂岩体是遭受了多期变形叠加作用的结果。
对于点苍山变质杂岩体进行了锆石U-Pb的年龄测定,并对测定结果进行了分析和总结。锆石U-Pb的测年结果得到了760-780Ma,240Ma,30Ma和23Ma四个年龄区间。可以说明,点苍山地区曾经经历了四次重要的区域构造-岩浆活动。
The Diancangshan (DCS) metamorphic complex is a highly significant metamorphic complex along the Red River-Ailaoshan ductile shear zone which attracted the attention of many geologists because of its distinctive location and characteristics.
This paper conducts the studies about the DCS metamorphic complex in several respects. 1) The constitutions of both of the western and eastern parts of the DCS metamorphic complex .2)The contrasts between the two parts in metamorphic rock associations. The author figured out that the main body of DCS metamorphic complex should be divided into two tectonic parts, i.e. the middle or deep metamorphic rock zone from west part to central part, and the retrogressive metamorphic zone in east part. The deep metamorphic rock zone is mainly composed by rock which is of upper greenschist facies to amphibolite facies. Rocks suffered strong sinistral slip shearing deformation. The eastern part is composed by 1.5km wide retrogressive metamorphic rocks, which is mainly composed by a suit of greenschist facies metamorphic rocks and granitic mylonite. 3) The studies of feldspar porphyroclasts and their deformational behaviors. The feldspar porphyroclasts can be subdivided into two types, the“hard porphyroclast”and the“soft porphyroclast”. The latter can be further subdivided into two sub-types. One is that feldspar porphyroclasts obviously haveσ,δ, orΦtype tails and the other feldspar porphyroclasts show banding, stripe and striation textures. 4)By studying structural characteristics of the DCS metamorphic complex and geologic bodies around it, the author tries to understand their roles in the exhumation of DCS metamorphic complex.
The DCS metamorphic complex possess many different microstructural phenomena in the eastern and western parts, which are caused by their different metamorphic and deformation characteristics. There are many microstructural phenomena in the granitic mylonites, e.g. subgrain rotation dynamic recrystallization, exsolution structure, kinking, microlayering,, banded structure, book shelf structure etc. They are of typical crystalline plastic deformation and brittle-ductile transition deformation evidences. The differences in metamorphism and deformation at the microscopic scale of rocks from the western part and eastern part are summarized. At the microscopic scale the rocks from the western part of the DCS show evidences of high temperature plastic deformation, but those from the eastern part mainly display evidences for brittle to ductile transition. In both the micro- and macro-scales the DCS metamorphic complex has undergone deformation superpositions.
U-Pb dating of zircons from the granitic rocks in the revealed four stages of tectono-magmatic activities i.e. 760-780Ma, 240Ma, 30Ma and 23Ma, in the DCS area.
本文从几个方面对点苍山变质杂岩体进行了观察和研究。1)点苍山变质杂岩体东、西两部分的宏观构造变形与组成特点的测量和观察;2)点苍山东、西两部分发育不同的变质岩组合规律和变质矿物组成特点的观察和总结。研究结果显示,点苍山变质杂岩体的主体,分属两个构造单元,即西部到中部的中深变质岩带和东部叠加的退变质岩带。其中主要的深变质岩带主要是由达高绿片岩相到角闪岩相的变质岩岩石组合而成,岩石普遍遭受强烈的左行走滑剪切变形改造,东部由1500m厚的退变质岩石构成,主要是一套绿片岩相叠加的变质岩带和花岗质糜棱岩组合而成的杂岩。3)对长石斑晶的变形行为的认识和总结,点苍山的长石斑晶分为“硬残斑”和“软残斑”两种类型。“软残斑”又分为两种状态,一种长石残斑具有明显的拖拽现象呈σ、δ、Φ形产出,另外一种长石残斑呈条带状、条纹状,条痕状产出。4)本文试图通过了解点苍山变质杂岩、及其周边地质体的构造特点,以期正确理解它们对点苍山变质杂岩体剥露的作用和意义。
点苍山变质杂岩体东、西两部分岩石保存了不同的显微构造现象,是由微观尺度不同特点的变质与变形作用所致。点苍山花岗质糜棱岩中赋存了亚晶粒旋转动态重结晶,出溶构造,双晶扭折,显微分层现象,条带状构造,书斜式构造等典型的晶质塑性变形与脆-韧性转变变形作用的证据。并对点苍山东西两部分岩石在显微尺度下所表现出来的不同的显微构造现象进行了观察和总结。在显微尺度下点苍山西坡的岩石表现出了高温塑性变形的证据,而在点苍山东坡岩石主要表现的是一种韧-脆性过度的一种显微表现。无论是在显微尺度还是宏观尺度上都反映了点苍山变质杂岩体是遭受了多期变形叠加作用的结果。
对于点苍山变质杂岩体进行了锆石U-Pb的年龄测定,并对测定结果进行了分析和总结。锆石U-Pb的测年结果得到了760-780Ma,240Ma,30Ma和23Ma四个年龄区间。可以说明,点苍山地区曾经经历了四次重要的区域构造-岩浆活动。
The Diancangshan (DCS) metamorphic complex is a highly significant metamorphic complex along the Red River-Ailaoshan ductile shear zone which attracted the attention of many geologists because of its distinctive location and characteristics.
This paper conducts the studies about the DCS metamorphic complex in several respects. 1) The constitutions of both of the western and eastern parts of the DCS metamorphic complex .2)The contrasts between the two parts in metamorphic rock associations. The author figured out that the main body of DCS metamorphic complex should be divided into two tectonic parts, i.e. the middle or deep metamorphic rock zone from west part to central part, and the retrogressive metamorphic zone in east part. The deep metamorphic rock zone is mainly composed by rock which is of upper greenschist facies to amphibolite facies. Rocks suffered strong sinistral slip shearing deformation. The eastern part is composed by 1.5km wide retrogressive metamorphic rocks, which is mainly composed by a suit of greenschist facies metamorphic rocks and granitic mylonite. 3) The studies of feldspar porphyroclasts and their deformational behaviors. The feldspar porphyroclasts can be subdivided into two types, the“hard porphyroclast”and the“soft porphyroclast”. The latter can be further subdivided into two sub-types. One is that feldspar porphyroclasts obviously haveσ,δ, orΦtype tails and the other feldspar porphyroclasts show banding, stripe and striation textures. 4)By studying structural characteristics of the DCS metamorphic complex and geologic bodies around it, the author tries to understand their roles in the exhumation of DCS metamorphic complex.
The DCS metamorphic complex possess many different microstructural phenomena in the eastern and western parts, which are caused by their different metamorphic and deformation characteristics. There are many microstructural phenomena in the granitic mylonites, e.g. subgrain rotation dynamic recrystallization, exsolution structure, kinking, microlayering,, banded structure, book shelf structure etc. They are of typical crystalline plastic deformation and brittle-ductile transition deformation evidences. The differences in metamorphism and deformation at the microscopic scale of rocks from the western part and eastern part are summarized. At the microscopic scale the rocks from the western part of the DCS show evidences of high temperature plastic deformation, but those from the eastern part mainly display evidences for brittle to ductile transition. In both the micro- and macro-scales the DCS metamorphic complex has undergone deformation superpositions.
U-Pb dating of zircons from the granitic rocks in the revealed four stages of tectono-magmatic activities i.e. 760-780Ma, 240Ma, 30Ma and 23Ma, in the DCS area.
引文
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[3]Shuyun Cao, Junlai Liu, Bernd Leiss, Franz Neubauer, Johann Genser, Chunqiang Zhao.Oligo-Miocene shearing along the Ailao Shan-Red River shear zone:Constraints from structural analysis and zircon U/Pb geochronology of magmatic rocks in the Diancang Shan massif,SE Tibet,China,Gondwana Research,19(2011):975～993.
[4]Shuyun Cao,Junlai liu,Bernd Leiss,Axel Vollbrecht,Johann Genser,Franz Neubauer,ChunqiangZhao.Initiation of left-lateral deformation along the Ailao Shan-Red River Shear zone:new microstructural,textural,and geochronological constraints from the Diancang Shan metamorphic massif,SW Yunnan,China,International Geology Review 2011,iFirst article,1～20.
[5]Shuyun Cao,Ph.D,Franz Neubauer,PhD,Junlai Liu,PhD,Johann Genser,PhD,Bernd Leiss,PhD.Exhumation of the Diancang Shan metamorphic complex along the Ailao Shan-Red River belt,southwestern Yunnan,China:evidence from 40Ar/39Ar thermochronology,JAES-D-10-00266R2.
[6]曹淑云,刘俊来,Bernd LEISS,等.哀牢山-红河剪切带左行走滑作用起始时间约束-点苍山高温糜棱岩的显微构造与热年代学证据.地质学报,2009,83 (10): 1388～1400
[7]曹淑云,刘俊来,胡玲.角闪石高温脆-韧性转变变形的显微与亚微构造证据——以滇西点苍山深变质剪切糜棱岩为例.中国科学(D辑),2007,37(8):1004～1013
[8]曹淑云.滇西点苍山高温糜棱岩显微构造和流动机制研究:[博士学位论文].北京:中国地质大学(北京),2007
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[12]李宝龙,季建清,付孝悦,等.滇西点苍山-哀牢山变质岩系锆石SHRIMP定年及其地质意义.岩石学报,2008,024(10):2322～2330
[13]李光容,金德山.程海断裂带挽近期活动性研究.云南地质,1990,9(1):1～24
[14]李齐,陈文寄,万景林,等.哀牢山-红河剪切带构造抬升和运动形式转换时间的新证据.中国科学(D辑),2000,30(6):576～583
[15]刘本培,冯庆来,Chonglakmani C,等.滇西古特提斯多岛洋的结构及其南北延伸.地学前缘,2002,9(3):161～171
[16]刘俊来,曹淑云,翟云峰,等.用陆块旋转解释藏东南渐新世-中新世伸展作用-来自点苍山及邻区变质核杂岩的证据.地学前缘, 2007, 14(4):40～48
[17]刘俊来,岛田充彦.实验变形岩石低温破裂作用的微观机制.地质科学,1999,34(2):242～250
[18]刘俊来,宋志杰,曹淑云,等.印度-欧亚侧向碰撞带构造-岩浆演化的动力学背景与过程—以藏东三江地区构造演化为例.岩石学报,2006,22(4):775～786
[19]刘俊来,王安建,曹淑云,等.滇西点苍山杂岩中混合岩的地质年代学分析及其区域构造内涵.岩石学报,2008,24(3):413～420
[20]刘俊来.变形岩石的显微构造与岩石圈流变学.地质通报,2004,23(9-10):980～985
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[2]Chen Haihong,Jon Dobson,Friedrich Heller,Hao Jie.Paleomagnetic evidence for clockwise rotation of the Simao region since the Cretaceous:A consequence of India-Asia collision,Earth and Planetary Science Letters 134(1995):203～217.
[3]Shuyun Cao, Junlai Liu, Bernd Leiss, Franz Neubauer, Johann Genser, Chunqiang Zhao.Oligo-Miocene shearing along the Ailao Shan-Red River shear zone:Constraints from structural analysis and zircon U/Pb geochronology of magmatic rocks in the Diancang Shan massif,SE Tibet,China,Gondwana Research,19(2011):975～993.
[4]Shuyun Cao,Junlai liu,Bernd Leiss,Axel Vollbrecht,Johann Genser,Franz Neubauer,ChunqiangZhao.Initiation of left-lateral deformation along the Ailao Shan-Red River Shear zone:new microstructural,textural,and geochronological constraints from the Diancang Shan metamorphic massif,SW Yunnan,China,International Geology Review 2011,iFirst article,1～20.
[5]Shuyun Cao,Ph.D,Franz Neubauer,PhD,Junlai Liu,PhD,Johann Genser,PhD,Bernd Leiss,PhD.Exhumation of the Diancang Shan metamorphic complex along the Ailao Shan-Red River belt,southwestern Yunnan,China:evidence from 40Ar/39Ar thermochronology,JAES-D-10-00266R2.
[6]曹淑云,刘俊来,Bernd LEISS,等.哀牢山-红河剪切带左行走滑作用起始时间约束-点苍山高温糜棱岩的显微构造与热年代学证据.地质学报,2009,83 (10): 1388～1400
[7]曹淑云,刘俊来,胡玲.角闪石高温脆-韧性转变变形的显微与亚微构造证据——以滇西点苍山深变质剪切糜棱岩为例.中国科学(D辑),2007,37(8):1004～1013
[8]曹淑云.滇西点苍山高温糜棱岩显微构造和流动机制研究:[博士学位论文].北京:中国地质大学(北京),2007
[9]陈福坤,许荣华.云南点苍山混合岩中锆石的U-Pb年龄及其地质意义.科学通报,1991,7:538～541
[10]韩竹君,徐杰,虢顺民,等.滇西北伸展构造区的构造特点及其动力学研究.中国地震, 1993,9(2):138～145
[11]胡玲.显微构造地质学概论.北京:地质出版社,1998
[12]李宝龙,季建清,付孝悦,等.滇西点苍山-哀牢山变质岩系锆石SHRIMP定年及其地质意义.岩石学报,2008,024(10):2322～2330
[13]李光容,金德山.程海断裂带挽近期活动性研究.云南地质,1990,9(1):1～24
[14]李齐,陈文寄,万景林,等.哀牢山-红河剪切带构造抬升和运动形式转换时间的新证据.中国科学(D辑),2000,30(6):576～583
[15]刘本培,冯庆来,Chonglakmani C,等.滇西古特提斯多岛洋的结构及其南北延伸.地学前缘,2002,9(3):161～171
[16]刘俊来,曹淑云,翟云峰,等.用陆块旋转解释藏东南渐新世-中新世伸展作用-来自点苍山及邻区变质核杂岩的证据.地学前缘, 2007, 14(4):40～48
[17]刘俊来,岛田充彦.实验变形岩石低温破裂作用的微观机制.地质科学,1999,34(2):242～250
[18]刘俊来,宋志杰,曹淑云,等.印度-欧亚侧向碰撞带构造-岩浆演化的动力学背景与过程—以藏东三江地区构造演化为例.岩石学报,2006,22(4):775～786
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