松潘—甘孜造山带三叠系极低级变质与变形作用研究
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摘要
松潘-甘孜造山带夹于塔里木-柴达木地块、羌塘和扬子地块之间,呈一个“倒三角形”,其主体范围:西以义敦岛弧带与羌塘地块相隔,北界为阿尼玛卿混杂岩带,东界及南界为龙门山-盐源前陆逆冲带。许志琴称其为中国“地质百慕大”。该地区三叠系分布极广,出露面积超过10 万km2,绝大多数区域以发育极低级变质作用和较强的变形为特征。
极低级变质作用介于沉积成岩作用与变质作用之间,缺乏新形成的变质平衡矿物组合,很难找到确定变质作用的矿物温压计的物理条件,构筑精细的P-T-t轨迹图解非常困难。因此,极低级变质作用研究成为地质作用研究的难点。自20世纪60 年代起,国际上先后有Weaver、Kubler 、Martin Frey 和 Doug Robison对极低级变质作用提出划分方案。在国内,毕先梅、索书田等人,通过测定板岩中伊利石、云母、绿泥石等矿物及多形矿物的结晶度和其它成熟度参数,可大致判断极低级变质作用的温度、压力区间,厘定极低级变质作用的上、下限。
为了对松潘-甘孜地区三叠系强变形浅变质的特征及变质与变形的对应关系作出解释,揭示变质与变形的温-压条件,本论文总结前人研究成果,通过野外地质调查和实测剖面研究,结合室内薄片鉴定、电子探针和流体包裹体测试分析,对松潘-甘孜地区三叠系主体岩性(板岩、砂板岩、变质砂岩及千枚岩)的变质作用得出5 个认识结论:1、整个松潘-甘孜地区经受了自北向南的强大挤压;2、变质矿物组合简单,除雏晶黑云母外,典型的变质矿物组合为Al+Chl+Ser(Mu)+Cc+Q等,变质矿物主要沿区域性劈理面(S1)的劈理域发育,具有区域动力变质作用特征,属于低级变质作用中的硬柱石-钠长石-绿泥石相;3、区域变质作用P-T 变化集中在T:180～200oC,P:1～2kbar(<0.2Gpa)。4、变质作用形成的时代为175～159Ma;5、在大地构造事件上,属于印支期碰撞造山后,加厚地壳重力调整及伸展作用的结果。
Songpan-Garze Orogenic zone lies between Tarim -Qaidam block,Qiangtang block and Yangtze block. It appears an ‘inversed triangle’. The main body of this zone: the west is Yidun island belt and separated from Qiangtang block;the north is Animaqing mélange belt;the east and south is Longmenshan-Yanyuan foreland thrust belt. Xu Zhiqin considered it ‘Geology Bermuda’. In this region Triassic stratum distributes very widely, and its area exceeds 100 thousand km2. The most zone develops very-low-grade metamorphism and obvious transformation.
The very-low-grade metamorphism intervenes between sedimentary and metamorphism,and it is short of new metamorphosed balanced mineral combination. It is difficult to find mineral index of temperature and stress in this process. To construct elaborate P-T-t diagram. Therefore it becomes a nodus in geological process study. Since 1960s, Weaver, Kubler, Martin Frey,and Doug Robison have put forward compartmentalization projection in the international. In country, Bi xianmei, Suo shutian, etc. can only estimate the temperature and stress interval of this metamorphism and centigram the upper and lower limit by mensurating the crystallinity and other maturity degree parameters of illite, mica, and chlorite, etc. in slate.
For giving an explaintion of strong transmogrification but feebleness metamorphism of and their corresponding relation of the Triassic stratum in Songpan-Ganzi area and opening out the temperature and stress condition, this paper summarized study production of predecessors, and put forward 5 conclusions about Songpan-Ganzi area Triassic main lithology(slate, sandrock,and blastopsammitic) through field geological investigation , actual measurement section plane study and combining indoor slice identification , electron probing and fluid enclosure testing analysis:1.Field outcrop strongly transmogrification, and often developed same cleavages(S1) erection or approximately erection ‘B’fold and symmetry similituded fold. 2.The metamorphosed mineral combination is simple, and the typical metamorphosed mineral combination is Al+Chl+Ser(Mu)+Cc+Q, etc. The metamorphosed mineral develops mainly along the cleavages of the territorial cleavages faces(S1), bearing territorial dynamic metamorphism character and belonging to the lawsonite-albite-chlorite face of slightly metamorphism. 3.Territorial metamorphism P-T change focus on T:180～200oC, P:1～2kbar(<0.2Gpa).4.The age of the metamorphism is 175～159Ma; 5.It is the result of lithosphere gravity adjust and stretch function after Indo-chinese epoch impinging orogen in geotectonic events.
极低级变质作用介于沉积成岩作用与变质作用之间,缺乏新形成的变质平衡矿物组合,很难找到确定变质作用的矿物温压计的物理条件,构筑精细的P-T-t轨迹图解非常困难。因此,极低级变质作用研究成为地质作用研究的难点。自20世纪60 年代起,国际上先后有Weaver、Kubler 、Martin Frey 和 Doug Robison对极低级变质作用提出划分方案。在国内,毕先梅、索书田等人,通过测定板岩中伊利石、云母、绿泥石等矿物及多形矿物的结晶度和其它成熟度参数,可大致判断极低级变质作用的温度、压力区间,厘定极低级变质作用的上、下限。
为了对松潘-甘孜地区三叠系强变形浅变质的特征及变质与变形的对应关系作出解释,揭示变质与变形的温-压条件,本论文总结前人研究成果,通过野外地质调查和实测剖面研究,结合室内薄片鉴定、电子探针和流体包裹体测试分析,对松潘-甘孜地区三叠系主体岩性(板岩、砂板岩、变质砂岩及千枚岩)的变质作用得出5 个认识结论:1、整个松潘-甘孜地区经受了自北向南的强大挤压;2、变质矿物组合简单,除雏晶黑云母外,典型的变质矿物组合为Al+Chl+Ser(Mu)+Cc+Q等,变质矿物主要沿区域性劈理面(S1)的劈理域发育,具有区域动力变质作用特征,属于低级变质作用中的硬柱石-钠长石-绿泥石相;3、区域变质作用P-T 变化集中在T:180～200oC,P:1～2kbar(<0.2Gpa)。4、变质作用形成的时代为175～159Ma;5、在大地构造事件上,属于印支期碰撞造山后,加厚地壳重力调整及伸展作用的结果。
Songpan-Garze Orogenic zone lies between Tarim -Qaidam block,Qiangtang block and Yangtze block. It appears an ‘inversed triangle’. The main body of this zone: the west is Yidun island belt and separated from Qiangtang block;the north is Animaqing mélange belt;the east and south is Longmenshan-Yanyuan foreland thrust belt. Xu Zhiqin considered it ‘Geology Bermuda’. In this region Triassic stratum distributes very widely, and its area exceeds 100 thousand km2. The most zone develops very-low-grade metamorphism and obvious transformation.
The very-low-grade metamorphism intervenes between sedimentary and metamorphism,and it is short of new metamorphosed balanced mineral combination. It is difficult to find mineral index of temperature and stress in this process. To construct elaborate P-T-t diagram. Therefore it becomes a nodus in geological process study. Since 1960s, Weaver, Kubler, Martin Frey,and Doug Robison have put forward compartmentalization projection in the international. In country, Bi xianmei, Suo shutian, etc. can only estimate the temperature and stress interval of this metamorphism and centigram the upper and lower limit by mensurating the crystallinity and other maturity degree parameters of illite, mica, and chlorite, etc. in slate.
For giving an explaintion of strong transmogrification but feebleness metamorphism of and their corresponding relation of the Triassic stratum in Songpan-Ganzi area and opening out the temperature and stress condition, this paper summarized study production of predecessors, and put forward 5 conclusions about Songpan-Ganzi area Triassic main lithology(slate, sandrock,and blastopsammitic) through field geological investigation , actual measurement section plane study and combining indoor slice identification , electron probing and fluid enclosure testing analysis:1.Field outcrop strongly transmogrification, and often developed same cleavages(S1) erection or approximately erection ‘B’fold and symmetry similituded fold. 2.The metamorphosed mineral combination is simple, and the typical metamorphosed mineral combination is Al+Chl+Ser(Mu)+Cc+Q, etc. The metamorphosed mineral develops mainly along the cleavages of the territorial cleavages faces(S1), bearing territorial dynamic metamorphism character and belonging to the lawsonite-albite-chlorite face of slightly metamorphism. 3.Territorial metamorphism P-T change focus on T:180～200oC, P:1～2kbar(<0.2Gpa).4.The age of the metamorphism is 175～159Ma; 5.It is the result of lithosphere gravity adjust and stretch function after Indo-chinese epoch impinging orogen in geotectonic events.
引文
[1]四川省地质矿产局.四川省区域地质志.北京:地质出版社.1991:455～512
[2]许志琴,侯立伟,王宗秀等.中国松潘甘孜造山带的造山过程.北京:地质出版社,1992.
[3]杨宗让.川西松潘-甘孜弧前盆地的形成及演化.沉积与特提斯地质,2002,22(3):53～59
[4]王乃文.青藏印度古陆及其与华夏古陆的并合[A].李光岑,J.L.麦尔西叶.中法喜马拉雅考察成果[C].北京:地质出版社,1984:39～62.
[5]梁斌,何文劲等.川西北壤塘地区三叠纪西康群极低级变质作用.矿物岩石,2003,23(1):42～45
[6]索书田,祁向雷, 毕先梅 右江中生代极低级变质带的变质变形过程 地质科技情报,1996,5(4):65～7122
[7]索书田,毕先梅等 右江盆地三叠纪岩层的极低级变质作用及其地球动力学意义 地质科学,1998(4)
[8]索书田 低级变质地体的构造特征———以右江印支—燕山褶皱带为例 地球科学进展 武汉:中国地质大学出版社,1992,20
[9]尹安.喜马拉雅 青藏高原造山带地质演化[J].地球学报,2001,22(3):193～230.
[10]刘斌,沈昆.流体包裹体热力学.地质出版社.1999
[11]赵孟为 划分成岩作用与埋藏变质作用的指标及其界线 地质论评,1995,41(3):238～242
[12]索书田,游振东,周汉文.极低级变质作用和极低级变质带综述.地质科技情报,1995,14(1) :1～8
[13]Frey M.Very-low-grade metamorphism of clastic sedimentary rocks.In:Frey M ed.Low Temperature Metamorphism. Blachie,Glasgow,1988,9～57
[14]任磊夫 变质作用与成岩作用界线问题的研究 长春地质学院学报,变质地质专辑,1987 35～4418
[15]索书田,王砚耕.用伊利石的结晶度及晶格参数b0确定右江构造带低级区域变质作用pt 条件的初步结果。地质构造学刊,1993,3(2):65～68
[16]朱光,徐嘉炜,Fletcher,CJN.应用X射线衍射分析胶北蓬莱群板岩中的变质作用 地质与勘探,1994,30～42
[17]沈正嘉,杨宏仪 台湾低度变质岩中钠云母产状之研究 海峡两岸地质学术研讨会论文摘要(1),1995 294～297
[18]俞震甫,黄怡祯,徐济安 碳质物之拉曼光谱可能成为低度变质岩变质度的指标 海峡两岸地质学术研讨会论文摘要(1),1995 307～310
[19]Frey, M., 1978, Progressive low-grade metamorphism of a black shale formation, central Swiss Alps, with special reference to pyrophyllite and margarite bearing assemblages. Journal of Petrology 19 (part), 95～135
[20]Frey, M., 1988, Very-low-grade metamorphism of clastic sedimentary rocks. In: (Frey, M., ed.) Low temperature Metamorphism. Blackie, Glasgow, 9～57
[21]Frey, M., Robinson, D., 1999, Low-grade metamorphism. London: Blackwell Science Ltd, pp 313.
[22]Martin Frey and Doug Robison,Low-Grade Metamorphism. Blackwell. 1999
[23]Martin Frey,low temperature metamorphism.Blackie.1987
[24]毕先梅,索书田等.极低级变质作用的研究现状.地学前缘,1998,5(4):302～306
[25]Barr T Dahlen F A,Mephail D C.Brittle frictional mountain building.J.Geophysical Res.1991,96(B6):10319～10338
[26]Chen chao-hsia.application of k -mica crystallinity to the study of very-low-grade metamorphism in the central range of Taiwan. Igcp proiect 294 international Symposium,1994,176～183
[27]M.-H.Huang,I.S.BUICK & L.W.Hou.Tectonometamorphic Evolution of the Easten Tibet Plateau:Evidence from the Central Songpan-Garzê Orogenic belt,Western China.Journal of Petrology,2003
[28]Pique A.Relations between stages of diagenetic and metamorphic evolution and the development of a primary cleavage in the northwestern Morcoccan Meseta.J.Struct.Geol.,1982,4(4):491～500
[29]Robinson D,Warr L.N,Bevins R E.The illite crystallinity technique:a critical appraisal of its precision.J.Metamorphic Geol.,1990,8(3):333～344
[30]Robinson D.Transition fron diagenesis to metanorphism in extensional and collision settings.Geology,1987,15(9):866～869
[31]Weaver C E.Possible uses of clay minerals In search for oil.Bulletin of the American Association of Petroleum Gellogists,1960,44(9):1505～1518
[32]潘桂棠,陈智梁,李兴振等.东特提斯地质构造形成演化.北京:地质出版社,1997:104～128
[33]张儒瑗,从柏林.矿物温度计和矿物压力计,地质出版社.1983
[34]Huang, M.H., Buick, I.S., and Hou, L.W., 2003a, Tectonometamorphic evolution of the Eastern Tibet Plateau: evidence from the central Songpan-Ganze orogenic belt, western China: Journal of Petrology, v. 44, p. 255～278
[35]Huang, M., Maas, R., Buick, I.S., and Williams, I.S., 2003b, Crustal response to continental collisions between the Tibet, Indian, South China and North China blocks: geochronological constraints from the Songpan-Ganze
[36]Kisch H J.Calibration of the znchizone:a critical comparison of illite crystallinity scales used for definition.J.Metamorphism Geol.1990,8(1):31～36
[37]Shan Yem-Hong,Yang Houng-Yi.Very-low-grade metamorphism of ultramafic fragments in basaltic tyffs from hsuebshan Range,northern Taiwan.Igcp proiect 294 international Symposium,1994,76～91
[2]许志琴,侯立伟,王宗秀等.中国松潘甘孜造山带的造山过程.北京:地质出版社,1992.
[3]杨宗让.川西松潘-甘孜弧前盆地的形成及演化.沉积与特提斯地质,2002,22(3):53～59
[4]王乃文.青藏印度古陆及其与华夏古陆的并合[A].李光岑,J.L.麦尔西叶.中法喜马拉雅考察成果[C].北京:地质出版社,1984:39～62.
[5]梁斌,何文劲等.川西北壤塘地区三叠纪西康群极低级变质作用.矿物岩石,2003,23(1):42～45
[6]索书田,祁向雷, 毕先梅 右江中生代极低级变质带的变质变形过程 地质科技情报,1996,5(4):65～7122
[7]索书田,毕先梅等 右江盆地三叠纪岩层的极低级变质作用及其地球动力学意义 地质科学,1998(4)
[8]索书田 低级变质地体的构造特征———以右江印支—燕山褶皱带为例 地球科学进展 武汉:中国地质大学出版社,1992,20
[9]尹安.喜马拉雅 青藏高原造山带地质演化[J].地球学报,2001,22(3):193～230.
[10]刘斌,沈昆.流体包裹体热力学.地质出版社.1999
[11]赵孟为 划分成岩作用与埋藏变质作用的指标及其界线 地质论评,1995,41(3):238～242
[12]索书田,游振东,周汉文.极低级变质作用和极低级变质带综述.地质科技情报,1995,14(1) :1～8
[13]Frey M.Very-low-grade metamorphism of clastic sedimentary rocks.In:Frey M ed.Low Temperature Metamorphism. Blachie,Glasgow,1988,9～57
[14]任磊夫 变质作用与成岩作用界线问题的研究 长春地质学院学报,变质地质专辑,1987 35～4418
[15]索书田,王砚耕.用伊利石的结晶度及晶格参数b0确定右江构造带低级区域变质作用pt 条件的初步结果。地质构造学刊,1993,3(2):65～68
[16]朱光,徐嘉炜,Fletcher,CJN.应用X射线衍射分析胶北蓬莱群板岩中的变质作用 地质与勘探,1994,30～42
[17]沈正嘉,杨宏仪 台湾低度变质岩中钠云母产状之研究 海峡两岸地质学术研讨会论文摘要(1),1995 294～297
[18]俞震甫,黄怡祯,徐济安 碳质物之拉曼光谱可能成为低度变质岩变质度的指标 海峡两岸地质学术研讨会论文摘要(1),1995 307～310
[19]Frey, M., 1978, Progressive low-grade metamorphism of a black shale formation, central Swiss Alps, with special reference to pyrophyllite and margarite bearing assemblages. Journal of Petrology 19 (part), 95～135
[20]Frey, M., 1988, Very-low-grade metamorphism of clastic sedimentary rocks. In: (Frey, M., ed.) Low temperature Metamorphism. Blackie, Glasgow, 9～57
[21]Frey, M., Robinson, D., 1999, Low-grade metamorphism. London: Blackwell Science Ltd, pp 313.
[22]Martin Frey and Doug Robison,Low-Grade Metamorphism. Blackwell. 1999
[23]Martin Frey,low temperature metamorphism.Blackie.1987
[24]毕先梅,索书田等.极低级变质作用的研究现状.地学前缘,1998,5(4):302～306
[25]Barr T Dahlen F A,Mephail D C.Brittle frictional mountain building.J.Geophysical Res.1991,96(B6):10319～10338
[26]Chen chao-hsia.application of k -mica crystallinity to the study of very-low-grade metamorphism in the central range of Taiwan. Igcp proiect 294 international Symposium,1994,176～183
[27]M.-H.Huang,I.S.BUICK & L.W.Hou.Tectonometamorphic Evolution of the Easten Tibet Plateau:Evidence from the Central Songpan-Garzê Orogenic belt,Western China.Journal of Petrology,2003
[28]Pique A.Relations between stages of diagenetic and metamorphic evolution and the development of a primary cleavage in the northwestern Morcoccan Meseta.J.Struct.Geol.,1982,4(4):491～500
[29]Robinson D,Warr L.N,Bevins R E.The illite crystallinity technique:a critical appraisal of its precision.J.Metamorphic Geol.,1990,8(3):333～344
[30]Robinson D.Transition fron diagenesis to metanorphism in extensional and collision settings.Geology,1987,15(9):866～869
[31]Weaver C E.Possible uses of clay minerals In search for oil.Bulletin of the American Association of Petroleum Gellogists,1960,44(9):1505～1518
[32]潘桂棠,陈智梁,李兴振等.东特提斯地质构造形成演化.北京:地质出版社,1997:104～128
[33]张儒瑗,从柏林.矿物温度计和矿物压力计,地质出版社.1983
[34]Huang, M.H., Buick, I.S., and Hou, L.W., 2003a, Tectonometamorphic evolution of the Eastern Tibet Plateau: evidence from the central Songpan-Ganze orogenic belt, western China: Journal of Petrology, v. 44, p. 255～278
[35]Huang, M., Maas, R., Buick, I.S., and Williams, I.S., 2003b, Crustal response to continental collisions between the Tibet, Indian, South China and North China blocks: geochronological constraints from the Songpan-Ganze
[36]Kisch H J.Calibration of the znchizone:a critical comparison of illite crystallinity scales used for definition.J.Metamorphism Geol.1990,8(1):31～36
[37]Shan Yem-Hong,Yang Houng-Yi.Very-low-grade metamorphism of ultramafic fragments in basaltic tyffs from hsuebshan Range,northern Taiwan.Igcp proiect 294 international Symposium,1994,76～91