Two generations of monazite were identified in one mica schist sample from the central zone of the eastern Kunlun Orogen at the northern margin of the Qinghai-Tibet Plateau. The first generation was found in the cores...Two generations of monazite were identified in one mica schist sample from the central zone of the eastern Kunlun Orogen at the northern margin of the Qinghai-Tibet Plateau. The first generation was found in the cores of garnet porphyroblasts with relatively high Y2O3 contents (averaging 1.012±0.088 wt%). The second generation occurs either as inclusions in the rims of garnet porphyroblasts,matrix kyanite,plagioclase and quartz,or as separate crystals associated with matrix biotite and muscovite mostly having a relatively low Y2O3 content (averaging 0.479±0.100 wt%). Electron microprobe (EMP) Th-U-Pbtotal chemical dating for two grains of the first generation monazite yields average ages of 455 ± 18 Ma and 420 ± 20 Ma,respectively; six grains of the second generation gave an average age of 246.1 ± 3.8 Ma. These ages suggest that the core and rim of the garnet porphyroblasts and their associated assemblages record two events of significant tectonometamorphism. The formation of the Ordovician monazite is related to the tectonometamorphic event responsible for continuous amalgamation of the Gondwanaland in the Late Pan-African period or for consumption of the Proto-Tethys,whereas the development of the Triassic monazite is related to the tectonometamorphic event for consumption of the Paleo-Tethys.展开更多
The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small u...The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic-ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni-Cu-hosted rocks. Zircon U-Pb dating suggests that the Shitoukengde Ni-Cu deposit formed in late Silurian （426-422 Ma）, and their zircons have ~Hf（t） values of-9.4 to 5.9 with the older TDMm ages （0.80-1.42 Ga）. Mafic-ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion iithophile elements （e.g., K, Rb, Th） and depleted in heavy rare earth elements and high field strength elements （e.g., Ta, Nb, Zr, Ti）. Sulfides from the deposit have the slightly higher ~34S values of 1.9-4.3%o than the mantle （0 ~ 2%o）. The major and trace element characteristics, and Sr-Nd-Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction-related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni-Cu deposit formed in the post-collisional, extensional regime related to the subducted oceanic slab break-off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian.展开更多
The Dabie orogen, Eastern Qinling orogen and Eastern Kunlun orogen are the major components of the Central Mountain Ranges of China and each has distinctively metamorphic processes in their oldest rock units. The Dab...The Dabie orogen, Eastern Qinling orogen and Eastern Kunlun orogen are the major components of the Central Mountain Ranges of China and each has distinctively metamorphic processes in their oldest rock units. The Dabie orogen oldest rock units had experienced an intermediate-higher pressure, upper amphibolite to lower granulite facies metamorphism in the Indosinian intracontinental subduction collision event. The clockwise pt path, synchronous attainment of t max and p max and a segment of high slope retrograde path suggest a tectono driven rapid exhumation of the oldest rock units to upper middle crustal level following the end of the subduction collision process. The oldest rock units, also called Qinling Group, of Eastern Qinling Mountains suffered intensively collisional metamorphism at an immature plate tectonic framework during Jinningian movement about 1 000 Ma ago. The clockwise pt path with reach of t max following several hundreds of MPa decreasing from p max suggests that the denudation of the deeply burial rock units was due essentially to isostatic relaxation. During the Caledonian stage, the highly metamorphosed oldest rock units suffered from a high t thermal event in arc environment and superimposed by contact metamorphism. After thermal peaks, the rock units were exhumed in a short distance and cooled down isobarically. No regional metamorphism higher than upper greenschist facies condition since 300 Ma has been traced within exposed rocks in the eastern portion of Northern Qinling orogen. The oldest rock units in the Eastern Kunlun orogen were metamorphosed to upper amphibolite facies to lower granulite facies rocks early or during the Luliang movement (some 1 800 Ma ago). The high grade metamorphic rock units had a long resident time at the deep crustal level, and were exhumed to middle upper crustal level during the Caledonian to Hercynian tectonometamorphic events. Shallow erosion of the orogenic belt led to good preservation of th展开更多
The small-scale Balugou Cu-Pb-Zn skarn deposit（45 298 tonnages of ore at 0.1% to 3.99% Cu, 0.20% to 0.43% Pb and 0.76% to 10.92% Zn） is located in the Wulonggou area in the eastern Kunlun orogen, NW China. Ore depos...The small-scale Balugou Cu-Pb-Zn skarn deposit（45 298 tonnages of ore at 0.1% to 3.99% Cu, 0.20% to 0.43% Pb and 0.76% to 10.92% Zn） is located in the Wulonggou area in the eastern Kunlun orogen, NW China. Ore deposition is spatially and temporally related with the pre-collisional Anisian Balugou granites（~244 Ma）. The mineralization hosted by the contact between marble beds within the Paleo-Proterozoic Jinshuikou Group and Balugou granites, was structurally and lithologically controlled. The mineralogy of the Balugou deposit includes an early simple skarn mineral gangue（epidote with little diopside） and a late complicated quartz sulfide assemblage（pyrite, pyrrhotite, chalcopyrite, sphalerite, galena, bornite, quartz, carbonate and chlorite）. The δ34S values of eighteen sulfides range from-2.1‰ to ＋2.8 ‰, with an average of ＋0.07‰, and the calculated δ34SH2S values for H2 S in hydrothermal fluids range from-3.2‰ to ＋2.4‰, with an average of ＋0.03‰, suggesting a relatively homogeneous magmatic（±mantle） source, with sulfur produced directly by the Balugou granites. The sixteen sulfides have 206Pb/204 Pb ratios from 18.367 4 to 18.384 1, 207Pb/204 Pb ratios from 15.634 6 to 15.641 5, and 208Pb/204 Pb ratios from 38.455 5 to 38.485 0, which are close to those of K-feldspars from the Balugou granites, but are far away from age-corrected lead isotopic ratios of six wall-rock samples. So it was considered that the Pb sources of sulfides must be almost derived from the Balugou granites rather than the older wall-rocks. Collectively, it＇s suggested that the Balugou Cu-Pb-Zn deposit belongs to skarn deposit, and the sulfur and lead deposited in it were leached from the Anisian Balugou granites.展开更多
Topography, as a net result of the dynamic interaction between endogenesis and exogenesis, holds immense information on tectonic uplift, surface erosion and thus mountain building. The eastern Kunlun （昆仑） orogen, ...Topography, as a net result of the dynamic interaction between endogenesis and exogenesis, holds immense information on tectonic uplift, surface erosion and thus mountain building. The eastern Kunlun （昆仑） orogen, which experienced significant Late Neogene tectonic uplift and is located in an arid environment, is advantageous for morphotectonic analysis based on well-preserved tectonic landforms. The digital elevation model （DEM） analysis was carried out for the central segment of the eastern Kunlun orogen based on shuttle radar topography mission （SRTM） data. River longitudinal profile analysis indicates that major rivers across the orogen are characterized by high river gradient indexes and intensive tectonic uplift. Differential uplift was also identified in swath-topography analysis in the studied area, which can be divided into three major tectonic-geomorphie units by orogenicstrike-parallel faults. It is indicated that the most active region is located to the south of the Xidatan （西大滩） fault with significant differential uplift. Another identified fault with differential uplift is the Middle Kunlun fault; however, the timing of which is suggested to be much older than that of the Xidatan fault. These analyses are concordantly supported by both field survey and studies of thermochronology, which in turn indicates that the DEM analysis bears great potential in morphotectonic analysis.展开更多
The Wulonggou area located in the Eastern Kunlun Orogen in NW China is characterized by extensive granitoid magmatism,ductile faulting and orogenic gold mineralization.The Huanglonggou granodiorite is cut by an orogen...The Wulonggou area located in the Eastern Kunlun Orogen in NW China is characterized by extensive granitoid magmatism,ductile faulting and orogenic gold mineralization.The Huanglonggou granodiorite is cut by an orogenic gold-bearing fault.This study investigated the major and trace-element compositions,zircon U-Pb dates and zircon Hf isotopic compositions of the Huanglonggou granodiorite.One Huanglonggou granodiorite sample yielded a weighted mean U-Pb zircon age of^221 Ma(Carnian).The Carnian granodiorite is metaluminous,with high alkalis contents of 6.37%--8.86%,high Al_2O_3contents of 15.41%--16.19%,high Sr contents of(426--475)×10^(-6),relatively high Sr/Y ratios,high(La/Yb)_Nvalues and low HREE,suggesting an adakite type high-Si O_2granite.The Huanglonggou granodiorite sample has zirconε_(Hf)(t)values ranging from-4.4 to+1.1.These Hf isotopic data suggest that the Carnian granodiorite was likely derived from the partial melting of subducted Paleo-Tethys oceanic slab.It is suggested that the Late Triassic granodiorite was emplaced during the northward subduction of Paleo-Tethys oceanic slab.Orogenic gold mineralization in the Wulonggou area formed after the emplacement of the Late Triassic intrusive rocks.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40272030 and 49972023)Outstanding Research Award of HK
文摘Two generations of monazite were identified in one mica schist sample from the central zone of the eastern Kunlun Orogen at the northern margin of the Qinghai-Tibet Plateau. The first generation was found in the cores of garnet porphyroblasts with relatively high Y2O3 contents (averaging 1.012±0.088 wt%). The second generation occurs either as inclusions in the rims of garnet porphyroblasts,matrix kyanite,plagioclase and quartz,or as separate crystals associated with matrix biotite and muscovite mostly having a relatively low Y2O3 content (averaging 0.479±0.100 wt%). Electron microprobe (EMP) Th-U-Pbtotal chemical dating for two grains of the first generation monazite yields average ages of 455 ± 18 Ma and 420 ± 20 Ma,respectively; six grains of the second generation gave an average age of 246.1 ± 3.8 Ma. These ages suggest that the core and rim of the garnet porphyroblasts and their associated assemblages record two events of significant tectonometamorphism. The formation of the Ordovician monazite is related to the tectonometamorphic event responsible for continuous amalgamation of the Gondwanaland in the Late Pan-African period or for consumption of the Proto-Tethys,whereas the development of the Triassic monazite is related to the tectonometamorphic event for consumption of the Paleo-Tethys.
基金financially supported by the National Natural Science Foundation of China(No.41272093)China geological survey project(No.12120114080901)
文摘The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic-ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni-Cu-hosted rocks. Zircon U-Pb dating suggests that the Shitoukengde Ni-Cu deposit formed in late Silurian （426-422 Ma）, and their zircons have ~Hf（t） values of-9.4 to 5.9 with the older TDMm ages （0.80-1.42 Ga）. Mafic-ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion iithophile elements （e.g., K, Rb, Th） and depleted in heavy rare earth elements and high field strength elements （e.g., Ta, Nb, Zr, Ti）. Sulfides from the deposit have the slightly higher ~34S values of 1.9-4.3%o than the mantle （0 ~ 2%o）. The major and trace element characteristics, and Sr-Nd-Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction-related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni-Cu deposit formed in the post-collisional, extensional regime related to the subducted oceanic slab break-off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian.
文摘The Dabie orogen, Eastern Qinling orogen and Eastern Kunlun orogen are the major components of the Central Mountain Ranges of China and each has distinctively metamorphic processes in their oldest rock units. The Dabie orogen oldest rock units had experienced an intermediate-higher pressure, upper amphibolite to lower granulite facies metamorphism in the Indosinian intracontinental subduction collision event. The clockwise pt path, synchronous attainment of t max and p max and a segment of high slope retrograde path suggest a tectono driven rapid exhumation of the oldest rock units to upper middle crustal level following the end of the subduction collision process. The oldest rock units, also called Qinling Group, of Eastern Qinling Mountains suffered intensively collisional metamorphism at an immature plate tectonic framework during Jinningian movement about 1 000 Ma ago. The clockwise pt path with reach of t max following several hundreds of MPa decreasing from p max suggests that the denudation of the deeply burial rock units was due essentially to isostatic relaxation. During the Caledonian stage, the highly metamorphosed oldest rock units suffered from a high t thermal event in arc environment and superimposed by contact metamorphism. After thermal peaks, the rock units were exhumed in a short distance and cooled down isobarically. No regional metamorphism higher than upper greenschist facies condition since 300 Ma has been traced within exposed rocks in the eastern portion of Northern Qinling orogen. The oldest rock units in the Eastern Kunlun orogen were metamorphosed to upper amphibolite facies to lower granulite facies rocks early or during the Luliang movement (some 1 800 Ma ago). The high grade metamorphic rock units had a long resident time at the deep crustal level, and were exhumed to middle upper crustal level during the Caledonian to Hercynian tectonometamorphic events. Shallow erosion of the orogenic belt led to good preservation of th
基金supported by the National Natural Science Foundation of China(Nos.41572056 and 40802021)the Open Foundation from the State Key Laboratory for Mineral Deposits Research,Department of Earth Sciences in Nanjing University(No.17-1112-4)
文摘The small-scale Balugou Cu-Pb-Zn skarn deposit（45 298 tonnages of ore at 0.1% to 3.99% Cu, 0.20% to 0.43% Pb and 0.76% to 10.92% Zn） is located in the Wulonggou area in the eastern Kunlun orogen, NW China. Ore deposition is spatially and temporally related with the pre-collisional Anisian Balugou granites（~244 Ma）. The mineralization hosted by the contact between marble beds within the Paleo-Proterozoic Jinshuikou Group and Balugou granites, was structurally and lithologically controlled. The mineralogy of the Balugou deposit includes an early simple skarn mineral gangue（epidote with little diopside） and a late complicated quartz sulfide assemblage（pyrite, pyrrhotite, chalcopyrite, sphalerite, galena, bornite, quartz, carbonate and chlorite）. The δ34S values of eighteen sulfides range from-2.1‰ to ＋2.8 ‰, with an average of ＋0.07‰, and the calculated δ34SH2S values for H2 S in hydrothermal fluids range from-3.2‰ to ＋2.4‰, with an average of ＋0.03‰, suggesting a relatively homogeneous magmatic（±mantle） source, with sulfur produced directly by the Balugou granites. The sixteen sulfides have 206Pb/204 Pb ratios from 18.367 4 to 18.384 1, 207Pb/204 Pb ratios from 15.634 6 to 15.641 5, and 208Pb/204 Pb ratios from 38.455 5 to 38.485 0, which are close to those of K-feldspars from the Balugou granites, but are far away from age-corrected lead isotopic ratios of six wall-rock samples. So it was considered that the Pb sources of sulfides must be almost derived from the Balugou granites rather than the older wall-rocks. Collectively, it＇s suggested that the Balugou Cu-Pb-Zn deposit belongs to skarn deposit, and the sulfur and lead deposited in it were leached from the Anisian Balugou granites.
基金supported by the China Geological Survey (Nos. 1212010610103 and 200313000005)
文摘Topography, as a net result of the dynamic interaction between endogenesis and exogenesis, holds immense information on tectonic uplift, surface erosion and thus mountain building. The eastern Kunlun （昆仑） orogen, which experienced significant Late Neogene tectonic uplift and is located in an arid environment, is advantageous for morphotectonic analysis based on well-preserved tectonic landforms. The digital elevation model （DEM） analysis was carried out for the central segment of the eastern Kunlun orogen based on shuttle radar topography mission （SRTM） data. River longitudinal profile analysis indicates that major rivers across the orogen are characterized by high river gradient indexes and intensive tectonic uplift. Differential uplift was also identified in swath-topography analysis in the studied area, which can be divided into three major tectonic-geomorphie units by orogenicstrike-parallel faults. It is indicated that the most active region is located to the south of the Xidatan （西大滩） fault with significant differential uplift. Another identified fault with differential uplift is the Middle Kunlun fault; however, the timing of which is suggested to be much older than that of the Xidatan fault. These analyses are concordantly supported by both field survey and studies of thermochronology, which in turn indicates that the DEM analysis bears great potential in morphotectonic analysis.
基金Supported by Project of National Natural Science Foundation of China(No.41572056)
文摘The Wulonggou area located in the Eastern Kunlun Orogen in NW China is characterized by extensive granitoid magmatism,ductile faulting and orogenic gold mineralization.The Huanglonggou granodiorite is cut by an orogenic gold-bearing fault.This study investigated the major and trace-element compositions,zircon U-Pb dates and zircon Hf isotopic compositions of the Huanglonggou granodiorite.One Huanglonggou granodiorite sample yielded a weighted mean U-Pb zircon age of^221 Ma(Carnian).The Carnian granodiorite is metaluminous,with high alkalis contents of 6.37%--8.86%,high Al_2O_3contents of 15.41%--16.19%,high Sr contents of(426--475)×10^(-6),relatively high Sr/Y ratios,high(La/Yb)_Nvalues and low HREE,suggesting an adakite type high-Si O_2granite.The Huanglonggou granodiorite sample has zirconε_(Hf)(t)values ranging from-4.4 to+1.1.These Hf isotopic data suggest that the Carnian granodiorite was likely derived from the partial melting of subducted Paleo-Tethys oceanic slab.It is suggested that the Late Triassic granodiorite was emplaced during the northward subduction of Paleo-Tethys oceanic slab.Orogenic gold mineralization in the Wulonggou area formed after the emplacement of the Late Triassic intrusive rocks.
