The western boundary of the Eastern Himalayan Syntaxis (EHS) is a deformation belt up to 30km wide (Fig.1). Trending ca. N35°E, it separates the Gangdise magmatic belt in the west from the gneiss of EHS in the ea...The western boundary of the Eastern Himalayan Syntaxis (EHS) is a deformation belt up to 30km wide (Fig.1). Trending ca. N35°E, it separates the Gangdise magmatic belt in the west from the gneiss of EHS in the east. Its rock association, mica\|schist, quartzite, marble, and amphibolite, can be traced to the south to Gangdise belt and they were probably metamorphosed from the sediments along Yarlung Zangbo. This belt consists of several intensive deformation zones, the largest one of which is along the belt’s western margin from Dongjug to Mainling and we called this ca. 10km wide shear zone as the Dongjug\|Mainling shear zone (DMSZ).DMSZ experienced earlier ductile shear and later ductile\|brittle normal faulting. The earlier deformation produced mylonitic rocks. Their foliation trends N30°～40°E and dips northwest with the angle ranging from 55°to 80°, steepening northeastward. The penetrative kinematic lineation in the rocks has a varying attitude along the trend of DMSZ. It dips southwest with an angle of ca.35° in the southwest near Mainling, whereas dips northeast in the northeast. Moreover, the northeast dipping lineation steepens northeastwards, e.g., its angle ranges form 30° to 45° in the segment from Serkyim La to Dongjug but becomes 60～70° in the northeast most in another zone near Parlung. Kinematic indicators show that the motion of DMSZ had a left\|lateral slipping component, but the vertical motion components were different in the southwest from the northeast. From Serkyim La to the northeast, DMSZ had a kinematics of NW plate (Gangdise belt) thrusting over the SE plate (EHS) and its thrusting component increased toward northeast. However, the DMSZ has a vertical motion with the SE plate (EHS) as the uplifting plate.展开更多
Lanping basin is located between Lancangjiang fault and Jinshajiang fault. Himalayan movement is the important tectogenesis, during which the activity of mid\|alkali magma is strong. For a long time, because the previ...Lanping basin is located between Lancangjiang fault and Jinshajiang fault. Himalayan movement is the important tectogenesis, during which the activity of mid\|alkali magma is strong. For a long time, because the previous had focused on studying porphyry copper, lead, zinc multi metal ore deposit in east uplift to this area, and they had ignored the relationship between Himalayan tectonomagnetic movement and multi\|metal mineralization in the basin.1 Characteristic of the Himalayan magmatic rock Himalayan magmatic rocks, a part of Himalayan porphyry zone, mainly distributed along Lijiang\|Beiya\|Weishan, which is the east to Lanping basin. There are a few magmatic rocks in the basin, a big scale of which is Yongping Zhuopan rock body, Yunlong Zaojiaochang rock body and Eryuan Shangyicun rock body. These magmatic rocks are mainly intrusion rocks and their characteristics are quartz syenite porphyry, alkalic rock, and granite porphyry. The ratio 87 Sr/ 86 Sr of rocks is 0 7046～0 7084, which reflects the magma source comes from mantle.The average isotopic age of these magmatic rocks is 40Ma. For example, Zhuopan rock body’s age of K\|Ar is 33 8Ma, Weishan rock body’s age of K\|Ar is 46 9Ma.展开更多
During the last 40Ma the marine 87 Sr/ 86 Sr record shows a rapid rise (from 0 7078 to 0 7092) [1] , a trend which has been linked to the Himalayan Orogeny [2] . Indeed, many Himalayan rivers, principally those of the...During the last 40Ma the marine 87 Sr/ 86 Sr record shows a rapid rise (from 0 7078 to 0 7092) [1] , a trend which has been linked to the Himalayan Orogeny [2] . Indeed, many Himalayan rivers, principally those of the Ganges\|Brahmaputra system, display high 87 Sr/ 86 Sr relative to [Sr] [3] . Theories concerning the cause of this radiogenic Sr enrichment are diverse, but our results suggest that Lesser Himalayan carbonate\|rich lithologies play a vital role [4,5] .The Bhote Kosi originates in Tibet at ca.5km elevation from Tibetan Sedimentary Series (TSS) bedrock, before traversing the High Himalayan Crystalline Series (HHCS) and Lesser Himalaya (LH) of eastern Nepal, joining the Indrawati (at ca.0 6km elevation) to form the Sun Kosi, part of the Ganges system. Carbonates, calc\|silicates and silicates have been identified from the TSS, HHCS and LH, and the Bhote Kosi provides an opportunity to study the influence of these upon fluvial chemistry. Interest is focused on the cause of a rapid rise in riverine Sr\|isotope ratios immediately downstream of the Main Central Thrust (MCT) and the role of carbonate\|rich lithologies exposed in this section. Similar lithologies are lacking in the catchment of a second Nepalese river system, the Lantang Khola—Trisuli, sampled during the same period, and used as a baseline indicator for the effect of LH carbonates on the dissolved load of the Bhote Kosi.展开更多
The paper focuses on geological and geochemical evidence of thermal brine genesis of Pb Zn deposits in Wuqia district, Xinjiang. The results suggest that the known Pb Zn deposits, such as Wulagen, are thermal brine ge...The paper focuses on geological and geochemical evidence of thermal brine genesis of Pb Zn deposits in Wuqia district, Xinjiang. The results suggest that the known Pb Zn deposits, such as Wulagen, are thermal brine genesis, which is supported by the features of tectonic setting, magma and regional metamorphism, and the characteristics of trace element distribution in strata and redistribution in the ore forming process, the REE patterns and their main parameters of main type ores, the composition features and the source indicators of Pb, S isotopes. Ore forming conditions of superlarge Pb Zn deposits studies show that there exists tectonic and sources setting of Jinding type superlarge Pb Zn deposits in this area. Five Pb Zn ore belts and central uplift belts discovered lately have not only confirmed that the genesis of Wulagen Pb Zn deposits is thermal genesis, but also further proved that there exists tectonic and source setting of Jinding type superlarge Pb Zn deposit in the study area. Mineral deposit model was described and prospecting potentiality of superlarge Pb Zn deposit and their significance were discussed.展开更多
Sanjiang (Jinshajiang River,Lancangjiang River and Nujiang River) concentration area in southwest China is within the Tethys\|Himalayan tectonic domain,and it is the main area where develops Himalayan movement and rel...Sanjiang (Jinshajiang River,Lancangjiang River and Nujiang River) concentration area in southwest China is within the Tethys\|Himalayan tectonic domain,and it is the main area where develops Himalayan movement and relative ore deposits,such as Yulong super large Cu\|Mo deposit,Jinding super large Pb\|Zn deposit,etc ,in West China.So it is a best place to study Himalayan movement and metallogeny.1 Metallogenic geological background Sanjiang concentration area has passed complex Tethys tectonic development before Cainozoic era,and it begins Himalayan inland basin\|mountain tectonic development at the end of Yanshan movement.It commonly accepts autochthonous platform type deposits since Mesozoic era,and the basin\|mountain tectonic pattern has already appeared.Old metamorphic terrains and paleo\|Tethys orogenic belts become “mountains”,as well as microplateforms sink to become “basins”.Comparing to Mesozoic basins,Eogene basins are many smaller garben\|type extension basins or strike\|slip extension basins on the background of big large basins.展开更多
The Eastern Sikkim area forming a part of the Lesser Himalaya is located between 27°10′～27°30′N latitudes and 88°25′～88°40′E longitudes (750km 2). The previous workers agreed that a domal str...The Eastern Sikkim area forming a part of the Lesser Himalaya is located between 27°10′～27°30′N latitudes and 88°25′～88°40′E longitudes (750km 2). The previous workers agreed that a domal structure is present in Sikkim which is constituted by low to high grade metamorphic rocks characterised by inverted metamorphism. The rocks were repeatedly deformed and were metamorphosed at about 550 to 770℃ (550 to 750MPa). Geologically, the oldest rocks of Eastern Sikkim are represented by Darjeeling Formation showing medium to high grade metamorphism. It is followed by low grade Daling Formation which is characterised by tectonic wedges of Lingtse gneiss. The potassic syenite intrusive i.e. the Sikkim igneous formation is youngest rock type of the area. The Darjeeling Formation associated with amphibolite bands consists of kyanite\|sillimanite, staurolite and garnet zones, while the Daling Formation is characterised by low grade chloritoid and chlorite zones. Lingtse Formation is gneissic in which patches of retrograded and sheared garnet schists are present. Intrusions of potassic syenites (Sikkim Formation) occur in the form of oval and concordant bodies. The F 1, F 2 and F 3 folds are well developed in rocks of Eastern Sikkim area.. The F 1 folds are rootless, tightly isoclinal or reclined and highly obliterated in their attitude. The F 2 folds belong to class IC of Ramsay (1967). Their interlimb angles vary from 20～50 degrees. Intersection lineation due to S 0/S 1 and S 2 surfaces is parallel to the F 2 folds axis. Third generation structures are represented by open to moderately tight and kinked folds. Superimposition of F 3 folds on F 2 folds resulted into type II interference pattern of Ramsay (1967). Structural analysis of these folds have revealed that F 2 folds are non\|cylindrical. The kink or F 3 folds were possibly responsible for the formation of a megakink resembling with the domal structure. The repeatedly deformed rocks of Eastern Sikkim area were folded, faulted, sheared/thrusted during the Himalayan orogeny. The Main Central Thrust (M C T) is actually a ductile shear zone and was subjected to imbrication during later phases of F 2 folding.展开更多
Most carbonatites occur in relatively stable, intra\|plate areas but some are found to occur in near to plate margins and may be linked with plate separation (Woolley, 1989). Although many carbonatites have been disco...Most carbonatites occur in relatively stable, intra\|plate areas but some are found to occur in near to plate margins and may be linked with plate separation (Woolley, 1989). Although many carbonatites have been discovered to occur in the orogenic belts in recent years, most of these rocks are related to post\|orogenic magmatism, that is, the rocks occur in the specially extensional setting. Therefore it is unusual that such magmatic rocks occur in the typical convergent environment. Here we report carbonatites and associated ultramafic and mafic rocks in the core of the eastern Himalayan syntaxis. The eastern Himalayan syntaxis consists of three tectonic units: the Gangdise, the Yarlung Zangbo, and the Himalayan units, each of which is bounded by faults (Liu & Zhong, 1997). The Himalayan unit, the northernmost exposed part of the Indian plate, is divided into two complexes, the amphibolite facies complex in the south and the granulite facies complex in the north. The granulite facies complex in the Himalayan unit have been argued to experience high\|pressure metamorphism and represent materials buried to upper\|mantle depths (Liu & Zhong, 1997). The carbonatites and associated ultramafic and mafic rocks only occur in the granulite facies rocks and are divided into two belts: northern and southern belts.The northern belt extends at least 30km, and is about 20km in width. The southern belt extends several kilometers, and is 3km or so in width. Each belt consists mainly of differently compositional dykes, extending parallel to gneissosity of granulite facies gneiss. Carbonatitic agglomerates are observed in the northern belt. From the center of carbonatite dykes to country rocks, five types of rock are observed: the center parts of carbonatites, the rim parts of carbonatites, ultramafic and mafic rocks, altered rocks and country rocks. The gneissosity of country rock was deformed by intrusion of dykes.展开更多
The Arun mega\|antiform, a large N—S structure transversal to the tectonic trend of the E Nepal Himalaya, is a tectonic window offering a complete section of the Himalayan nappe pile, from the Lesser Himalayan zone t...The Arun mega\|antiform, a large N—S structure transversal to the tectonic trend of the E Nepal Himalaya, is a tectonic window offering a complete section of the Himalayan nappe pile, from the Lesser Himalayan zone to the Tethyan Himalaya. At the northern end of the Arun tectonic window (ATW), the Ama Drime—Nyonno Ri range of south Tibet exposes a section of that portion of the Main Central Thrust (MCT) zone and Lesser Himalayan Crystallines (LHC) which elsewhere in Nepal is concealed below the overlying Higher Himalayan Crystalline (HHC) nappe (Fig. 1). As throughout the Himalaya at the structural level of the MCT, the ATW is characterized by an inverted metamorphic field gradient characterized by a progression from chlorite to sillimanite grade from low to high structural levels of the nappe pile. Metamorphic peak temperatures rise from circa 400℃ in the pelitic and psammitic Precambrian metasediments of the Lesser Himalayan Tumlingtar Unit, to 550～620℃ in the overlying LHC, to over 700℃ in the muscovite\|free Barun Gneiss, the lowermost HHC unit in the Arun valley.展开更多
The Eastern Himalayan Syntaxis (EHS) is one of the strongest deformation area along the Himalayan belt resulted from the collision between Indian plate and the Eurasian plate since 50～60Ma, and has sensitivity tracke...The Eastern Himalayan Syntaxis (EHS) is one of the strongest deformation area along the Himalayan belt resulted from the collision between Indian plate and the Eurasian plate since 50～60Ma, and has sensitivity tracked and preserved the whole collisional processes. It should depend on the detail geological investigations to establish the deformational accommodate mode, and the uplift history, to elucidate the deep structure and the crust\|mantle interaction of the EHS. The Namjabarwa metamorphic complex indented into the Gangdise arc along the sinistral Pai shear fault and the dextral Aniqiao shear fault on the both sides of the Great Canyon of Yalung Zangbo river since the collision of the NE corner of the Indian plate and the Eurasian Plate at 60～70Ma [1] . The distance between Yarlung Zangbo suture and Bangong—Nujiang suture is shortened more 120km in the EHS area than that of the Lhasa block.展开更多
The Tarim Basin corresponds to a large sedimentary depression which separates (Yang et al.,1996)the Tianshan belt to the North from the Kunlun—Pamir belt to the South (Fig.1A).Its western part can be divided into the...The Tarim Basin corresponds to a large sedimentary depression which separates (Yang et al.,1996)the Tianshan belt to the North from the Kunlun—Pamir belt to the South (Fig.1A).Its western part can be divided into the following structural units,from North to South (Fig.1B):①Foreland belts of Southern Tianshan.which involve Palaeozoic and Cenozoic sediments overlapping southward the Quaternary infilling of the basin (Dong Jia et al.,1998);②Bachu NW\|SE oriented Uplift of Central Tarim. where NE dipping reverse faults crossing Palaeozoic and Cenozoic series can be found (Hendrix et al.,1992);③SW depression of Tarim Basin. filled up with thick (up to 15000m),weakly deformed,post hercynian sediments;④Foreland belts of West Kunlun\|Pamir. made up of Precambrian,Palaeozoic,Mesozoic and Cenozoic materials overlapping northeastward the preceding unit(Qu et al.,1996).展开更多
Different attempts have been done to deduce the shortening of the Himalayan belt during the India\|Asia convergence. Dewey et al. (1989) and Le Pichon et al.(1992) calculated an India\|Asia shortening of 2300～2150km ...Different attempts have been done to deduce the shortening of the Himalayan belt during the India\|Asia convergence. Dewey et al. (1989) and Le Pichon et al.(1992) calculated an India\|Asia shortening of 2300～2150km and 2800～3000km in the western and eastern syntaxes, respectively, since the late 45Ma. According to seafloor\|spreading reconstruction, a total shortening of 3000～500km was estimated after the initial contact of the two plates at 55～50Ma (Molnar and Tapponier, 1975 ; Molnar et al., 1988 ; Replumaz, 1999). Since 40Ma, the part of shortening only accommodated by the Himalayan belt was estimated around 470km in the western part (Coward and Butler, 1985) and 550 to 630km to the east (Ratsbacher et al., 1994 ; Replumaz, 1999). In contrast, global plate reconstructions suggest that the shortening in the Himalaya is of about 1250～250km (Achache et al., 1984 ; Powell et al., 1988 ; Dewey et al.,1989 ; Klootwijk et al., 1992 ; Matte et al., 1997). This discrepancy between the amount of shortening estimated by balancing the Himalayan belt and by plate reconstruction favour the existence of a greater India buried up to 1000km north of the present\|day Indus suture zone and subducted before Middle Eocene time (Klootwijk et al., 1979 ; Patriat and Achache, 1984).展开更多
文摘The western boundary of the Eastern Himalayan Syntaxis (EHS) is a deformation belt up to 30km wide (Fig.1). Trending ca. N35°E, it separates the Gangdise magmatic belt in the west from the gneiss of EHS in the east. Its rock association, mica\|schist, quartzite, marble, and amphibolite, can be traced to the south to Gangdise belt and they were probably metamorphosed from the sediments along Yarlung Zangbo. This belt consists of several intensive deformation zones, the largest one of which is along the belt’s western margin from Dongjug to Mainling and we called this ca. 10km wide shear zone as the Dongjug\|Mainling shear zone (DMSZ).DMSZ experienced earlier ductile shear and later ductile\|brittle normal faulting. The earlier deformation produced mylonitic rocks. Their foliation trends N30°～40°E and dips northwest with the angle ranging from 55°to 80°, steepening northeastward. The penetrative kinematic lineation in the rocks has a varying attitude along the trend of DMSZ. It dips southwest with an angle of ca.35° in the southwest near Mainling, whereas dips northeast in the northeast. Moreover, the northeast dipping lineation steepens northeastwards, e.g., its angle ranges form 30° to 45° in the segment from Serkyim La to Dongjug but becomes 60～70° in the northeast most in another zone near Parlung. Kinematic indicators show that the motion of DMSZ had a left\|lateral slipping component, but the vertical motion components were different in the southwest from the northeast. From Serkyim La to the northeast, DMSZ had a kinematics of NW plate (Gangdise belt) thrusting over the SE plate (EHS) and its thrusting component increased toward northeast. However, the DMSZ has a vertical motion with the SE plate (EHS) as the uplifting plate.
文摘Lanping basin is located between Lancangjiang fault and Jinshajiang fault. Himalayan movement is the important tectogenesis, during which the activity of mid\|alkali magma is strong. For a long time, because the previous had focused on studying porphyry copper, lead, zinc multi metal ore deposit in east uplift to this area, and they had ignored the relationship between Himalayan tectonomagnetic movement and multi\|metal mineralization in the basin.1 Characteristic of the Himalayan magmatic rock Himalayan magmatic rocks, a part of Himalayan porphyry zone, mainly distributed along Lijiang\|Beiya\|Weishan, which is the east to Lanping basin. There are a few magmatic rocks in the basin, a big scale of which is Yongping Zhuopan rock body, Yunlong Zaojiaochang rock body and Eryuan Shangyicun rock body. These magmatic rocks are mainly intrusion rocks and their characteristics are quartz syenite porphyry, alkalic rock, and granite porphyry. The ratio 87 Sr/ 86 Sr of rocks is 0 7046～0 7084, which reflects the magma source comes from mantle.The average isotopic age of these magmatic rocks is 40Ma. For example, Zhuopan rock body’s age of K\|Ar is 33 8Ma, Weishan rock body’s age of K\|Ar is 46 9Ma.
文摘During the last 40Ma the marine 87 Sr/ 86 Sr record shows a rapid rise (from 0 7078 to 0 7092) [1] , a trend which has been linked to the Himalayan Orogeny [2] . Indeed, many Himalayan rivers, principally those of the Ganges\|Brahmaputra system, display high 87 Sr/ 86 Sr relative to [Sr] [3] . Theories concerning the cause of this radiogenic Sr enrichment are diverse, but our results suggest that Lesser Himalayan carbonate\|rich lithologies play a vital role [4,5] .The Bhote Kosi originates in Tibet at ca.5km elevation from Tibetan Sedimentary Series (TSS) bedrock, before traversing the High Himalayan Crystalline Series (HHCS) and Lesser Himalaya (LH) of eastern Nepal, joining the Indrawati (at ca.0 6km elevation) to form the Sun Kosi, part of the Ganges system. Carbonates, calc\|silicates and silicates have been identified from the TSS, HHCS and LH, and the Bhote Kosi provides an opportunity to study the influence of these upon fluvial chemistry. Interest is focused on the cause of a rapid rise in riverine Sr\|isotope ratios immediately downstream of the Main Central Thrust (MCT) and the role of carbonate\|rich lithologies exposed in this section. Similar lithologies are lacking in the catchment of a second Nepalese river system, the Lantang Khola—Trisuli, sampled during the same period, and used as a baseline indicator for the effect of LH carbonates on the dissolved load of the Bhote Kosi.
基金TheNationalNaturalScienceFoundationofChina (No .4 0 0 72 0 32 )
文摘The paper focuses on geological and geochemical evidence of thermal brine genesis of Pb Zn deposits in Wuqia district, Xinjiang. The results suggest that the known Pb Zn deposits, such as Wulagen, are thermal brine genesis, which is supported by the features of tectonic setting, magma and regional metamorphism, and the characteristics of trace element distribution in strata and redistribution in the ore forming process, the REE patterns and their main parameters of main type ores, the composition features and the source indicators of Pb, S isotopes. Ore forming conditions of superlarge Pb Zn deposits studies show that there exists tectonic and sources setting of Jinding type superlarge Pb Zn deposits in this area. Five Pb Zn ore belts and central uplift belts discovered lately have not only confirmed that the genesis of Wulagen Pb Zn deposits is thermal genesis, but also further proved that there exists tectonic and source setting of Jinding type superlarge Pb Zn deposit in the study area. Mineral deposit model was described and prospecting potentiality of superlarge Pb Zn deposit and their significance were discussed.
文摘Sanjiang (Jinshajiang River,Lancangjiang River and Nujiang River) concentration area in southwest China is within the Tethys\|Himalayan tectonic domain,and it is the main area where develops Himalayan movement and relative ore deposits,such as Yulong super large Cu\|Mo deposit,Jinding super large Pb\|Zn deposit,etc ,in West China.So it is a best place to study Himalayan movement and metallogeny.1 Metallogenic geological background Sanjiang concentration area has passed complex Tethys tectonic development before Cainozoic era,and it begins Himalayan inland basin\|mountain tectonic development at the end of Yanshan movement.It commonly accepts autochthonous platform type deposits since Mesozoic era,and the basin\|mountain tectonic pattern has already appeared.Old metamorphic terrains and paleo\|Tethys orogenic belts become “mountains”,as well as microplateforms sink to become “basins”.Comparing to Mesozoic basins,Eogene basins are many smaller garben\|type extension basins or strike\|slip extension basins on the background of big large basins.
文摘The Eastern Sikkim area forming a part of the Lesser Himalaya is located between 27°10′～27°30′N latitudes and 88°25′～88°40′E longitudes (750km 2). The previous workers agreed that a domal structure is present in Sikkim which is constituted by low to high grade metamorphic rocks characterised by inverted metamorphism. The rocks were repeatedly deformed and were metamorphosed at about 550 to 770℃ (550 to 750MPa). Geologically, the oldest rocks of Eastern Sikkim are represented by Darjeeling Formation showing medium to high grade metamorphism. It is followed by low grade Daling Formation which is characterised by tectonic wedges of Lingtse gneiss. The potassic syenite intrusive i.e. the Sikkim igneous formation is youngest rock type of the area. The Darjeeling Formation associated with amphibolite bands consists of kyanite\|sillimanite, staurolite and garnet zones, while the Daling Formation is characterised by low grade chloritoid and chlorite zones. Lingtse Formation is gneissic in which patches of retrograded and sheared garnet schists are present. Intrusions of potassic syenites (Sikkim Formation) occur in the form of oval and concordant bodies. The F 1, F 2 and F 3 folds are well developed in rocks of Eastern Sikkim area.. The F 1 folds are rootless, tightly isoclinal or reclined and highly obliterated in their attitude. The F 2 folds belong to class IC of Ramsay (1967). Their interlimb angles vary from 20～50 degrees. Intersection lineation due to S 0/S 1 and S 2 surfaces is parallel to the F 2 folds axis. Third generation structures are represented by open to moderately tight and kinked folds. Superimposition of F 3 folds on F 2 folds resulted into type II interference pattern of Ramsay (1967). Structural analysis of these folds have revealed that F 2 folds are non\|cylindrical. The kink or F 3 folds were possibly responsible for the formation of a megakink resembling with the domal structure. The repeatedly deformed rocks of Eastern Sikkim area were folded, faulted, sheared/thrusted during the Himalayan orogeny. The Main Central Thrust (M C T) is actually a ductile shear zone and was subjected to imbrication during later phases of F 2 folding.
文摘Most carbonatites occur in relatively stable, intra\|plate areas but some are found to occur in near to plate margins and may be linked with plate separation (Woolley, 1989). Although many carbonatites have been discovered to occur in the orogenic belts in recent years, most of these rocks are related to post\|orogenic magmatism, that is, the rocks occur in the specially extensional setting. Therefore it is unusual that such magmatic rocks occur in the typical convergent environment. Here we report carbonatites and associated ultramafic and mafic rocks in the core of the eastern Himalayan syntaxis. The eastern Himalayan syntaxis consists of three tectonic units: the Gangdise, the Yarlung Zangbo, and the Himalayan units, each of which is bounded by faults (Liu & Zhong, 1997). The Himalayan unit, the northernmost exposed part of the Indian plate, is divided into two complexes, the amphibolite facies complex in the south and the granulite facies complex in the north. The granulite facies complex in the Himalayan unit have been argued to experience high\|pressure metamorphism and represent materials buried to upper\|mantle depths (Liu & Zhong, 1997). The carbonatites and associated ultramafic and mafic rocks only occur in the granulite facies rocks and are divided into two belts: northern and southern belts.The northern belt extends at least 30km, and is about 20km in width. The southern belt extends several kilometers, and is 3km or so in width. Each belt consists mainly of differently compositional dykes, extending parallel to gneissosity of granulite facies gneiss. Carbonatitic agglomerates are observed in the northern belt. From the center of carbonatite dykes to country rocks, five types of rock are observed: the center parts of carbonatites, the rim parts of carbonatites, ultramafic and mafic rocks, altered rocks and country rocks. The gneissosity of country rock was deformed by intrusion of dykes.
文摘The Arun mega\|antiform, a large N—S structure transversal to the tectonic trend of the E Nepal Himalaya, is a tectonic window offering a complete section of the Himalayan nappe pile, from the Lesser Himalayan zone to the Tethyan Himalaya. At the northern end of the Arun tectonic window (ATW), the Ama Drime—Nyonno Ri range of south Tibet exposes a section of that portion of the Main Central Thrust (MCT) zone and Lesser Himalayan Crystallines (LHC) which elsewhere in Nepal is concealed below the overlying Higher Himalayan Crystalline (HHC) nappe (Fig. 1). As throughout the Himalaya at the structural level of the MCT, the ATW is characterized by an inverted metamorphic field gradient characterized by a progression from chlorite to sillimanite grade from low to high structural levels of the nappe pile. Metamorphic peak temperatures rise from circa 400℃ in the pelitic and psammitic Precambrian metasediments of the Lesser Himalayan Tumlingtar Unit, to 550～620℃ in the overlying LHC, to over 700℃ in the muscovite\|free Barun Gneiss, the lowermost HHC unit in the Arun valley.
基金TheNationalNaturalSciencesFoundationofChina (No .49732 10 0 )andNationalKeyProject (No .19980 40 80 0 )forBasicResearchofTibet
文摘The Eastern Himalayan Syntaxis (EHS) is one of the strongest deformation area along the Himalayan belt resulted from the collision between Indian plate and the Eurasian plate since 50～60Ma, and has sensitivity tracked and preserved the whole collisional processes. It should depend on the detail geological investigations to establish the deformational accommodate mode, and the uplift history, to elucidate the deep structure and the crust\|mantle interaction of the EHS. The Namjabarwa metamorphic complex indented into the Gangdise arc along the sinistral Pai shear fault and the dextral Aniqiao shear fault on the both sides of the Great Canyon of Yalung Zangbo river since the collision of the NE corner of the Indian plate and the Eurasian Plate at 60～70Ma [1] . The distance between Yarlung Zangbo suture and Bangong—Nujiang suture is shortened more 120km in the EHS area than that of the Lhasa block.
基金theNationalNaturalScienceFoundationofChina (No ..4982 5 10 2 )
文摘The Tarim Basin corresponds to a large sedimentary depression which separates (Yang et al.,1996)the Tianshan belt to the North from the Kunlun—Pamir belt to the South (Fig.1A).Its western part can be divided into the following structural units,from North to South (Fig.1B):①Foreland belts of Southern Tianshan.which involve Palaeozoic and Cenozoic sediments overlapping southward the Quaternary infilling of the basin (Dong Jia et al.,1998);②Bachu NW\|SE oriented Uplift of Central Tarim. where NE dipping reverse faults crossing Palaeozoic and Cenozoic series can be found (Hendrix et al.,1992);③SW depression of Tarim Basin. filled up with thick (up to 15000m),weakly deformed,post hercynian sediments;④Foreland belts of West Kunlun\|Pamir. made up of Precambrian,Palaeozoic,Mesozoic and Cenozoic materials overlapping northeastward the preceding unit(Qu et al.,1996).
文摘Different attempts have been done to deduce the shortening of the Himalayan belt during the India\|Asia convergence. Dewey et al. (1989) and Le Pichon et al.(1992) calculated an India\|Asia shortening of 2300～2150km and 2800～3000km in the western and eastern syntaxes, respectively, since the late 45Ma. According to seafloor\|spreading reconstruction, a total shortening of 3000～500km was estimated after the initial contact of the two plates at 55～50Ma (Molnar and Tapponier, 1975 ; Molnar et al., 1988 ; Replumaz, 1999). Since 40Ma, the part of shortening only accommodated by the Himalayan belt was estimated around 470km in the western part (Coward and Butler, 1985) and 550 to 630km to the east (Ratsbacher et al., 1994 ; Replumaz, 1999). In contrast, global plate reconstructions suggest that the shortening in the Himalaya is of about 1250～250km (Achache et al., 1984 ; Powell et al., 1988 ; Dewey et al.,1989 ; Klootwijk et al., 1992 ; Matte et al., 1997). This discrepancy between the amount of shortening estimated by balancing the Himalayan belt and by plate reconstruction favour the existence of a greater India buried up to 1000km north of the present\|day Indus suture zone and subducted before Middle Eocene time (Klootwijk et al., 1979 ; Patriat and Achache, 1984).
