A huge thrust system, the North Lhasa Thrust (NLT), was discovered in the northern Lhasa block of the Tibetan Plateau based on geological mapping of the Damxung region and its vicinity, the Deqen-Lunpola traverse and ...A huge thrust system, the North Lhasa Thrust (NLT), was discovered in the northern Lhasa block of the Tibetan Plateau based on geological mapping of the Damxung region and its vicinity, the Deqen-Lunpola traverse and the Amdo-Bam Co profile. The NLT consists of the Dongqiao-Lunpola thrust (DLT), the west Namco thrust (WNT) and the south Damxung thrust (SDT) and ductile shear zones, ophiolite slices and folds extending in a WNW direction. Major thrust faults of the NLT seem to merge into a single deep-seated detachment of the upper-crust and totally displaced southward as far as 100-120 km. Chronological analyses with 39Ar-40Ar of plagioclase and hornblende, Rb-Sr isochron of minerals and fission-tracks of apatite from mylonite within the WNT yield ages of 174-173 Ma, 109 Ma and 44 Ma, showing 3 periods of thrusting in the north Lhasa block caused by subduction of the Tethys oceanic plate and the India-Eurasia continental collision respectively.展开更多
Kuruqtagh block is the best area for Precambrian geology in Xinjiang Autonomous Region, NW China, since it exposed complete Precambrian lithology units. The study of this ancient base will deepen the understanding of ...Kuruqtagh block is the best area for Precambrian geology in Xinjiang Autonomous Region, NW China, since it exposed complete Precambrian lithology units. The study of this ancient base will deepen the understanding of the Precambrian evolution of the Tarim Basin. In this paper, we studied the petrology, geochemistry, zircon LA-ICPMS U-Pb chronology and zircon Hf isotope of Daxigou anorthosite(DA) which is located at the northern margin of Tarim craton and discussed the rock formation, tectonic and geological significance. Zircons from the intrusions display oscillatory zoning and high Th/U ratios(0.39–1.35), implying their magmatic origin. Zircon LA-ICP-MS U-Pb dating results indicate that they formed during the Paleoproterozoic age with the weighted 206Pb/238 U average age of 1818±9 Ma, which is significantly different from former's Neoproterozoic age, and is coincidentally identical with its associated syenite granite age within the error range. Studies on petrogeochemistry suggest that DA belongs to medium-sodium peraluminous alkaline type, rich in Pb, La, Th and LILE, and poor in HFSE(Gd, Nd, and Ta). The chondrite-normalized REE pattern is slightly to the right form. The average ∑REE is 317.2×10-6; HREE show moderate fractionation [average LREE/HREE is 14.71, average(La/Yb)N is 24.77; average(La/Sm)N is 3.85, and average(Gd/Yb)N is 3.46]; and the δEu and δCe are not obvious. Their initial Hf isotope ratios and Hf two-stage model ages range from-6.6 to-4.43 and 2.63 to 2.74 Ga, respectively. Taken together, it is suggested that Daxigou anorthosite is a typical volcanic anorthosite and its primary magma could be contaminated by the partial melt Neoarchaean crust and mainly formed in the arc environment, which recoded the tectonic-magma activities response of the Tarim refers to the amalgamation of the supercontinent Columbia.展开更多
The regional migmatites in the Yunkai Block were formed under low\|pressure metamorphism. The majority of their protolith are biotite\|rich peraluminous gneisses. Detailed field observations, and studies of petrology,...The regional migmatites in the Yunkai Block were formed under low\|pressure metamorphism. The majority of their protolith are biotite\|rich peraluminous gneisses. Detailed field observations, and studies of petrology, spatial distribution of minerals and geochemistry suggest that the leucosomes were derived from anatexis. The single grain zircon U\|Pb dating data indicate that a pulse of migmatization occurred at 394～449 Ma and may have resulted from the large\|scale Caledonian magmatism in the Yunkai Block.展开更多
文摘A huge thrust system, the North Lhasa Thrust (NLT), was discovered in the northern Lhasa block of the Tibetan Plateau based on geological mapping of the Damxung region and its vicinity, the Deqen-Lunpola traverse and the Amdo-Bam Co profile. The NLT consists of the Dongqiao-Lunpola thrust (DLT), the west Namco thrust (WNT) and the south Damxung thrust (SDT) and ductile shear zones, ophiolite slices and folds extending in a WNW direction. Major thrust faults of the NLT seem to merge into a single deep-seated detachment of the upper-crust and totally displaced southward as far as 100-120 km. Chronological analyses with 39Ar-40Ar of plagioclase and hornblende, Rb-Sr isochron of minerals and fission-tracks of apatite from mylonite within the WNT yield ages of 174-173 Ma, 109 Ma and 44 Ma, showing 3 periods of thrusting in the north Lhasa block caused by subduction of the Tethys oceanic plate and the India-Eurasia continental collision respectively.
基金founded by the 305 Project of State Science and Technology Support Program(Grant No.2011BAB06B04-05)the China Postdoctoral Science Foundation Funded Project(Grant No.2012M521492 and 2013T60758)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(Grant No.CUG120840,CUG120702 and CUGL120296)
文摘Kuruqtagh block is the best area for Precambrian geology in Xinjiang Autonomous Region, NW China, since it exposed complete Precambrian lithology units. The study of this ancient base will deepen the understanding of the Precambrian evolution of the Tarim Basin. In this paper, we studied the petrology, geochemistry, zircon LA-ICPMS U-Pb chronology and zircon Hf isotope of Daxigou anorthosite(DA) which is located at the northern margin of Tarim craton and discussed the rock formation, tectonic and geological significance. Zircons from the intrusions display oscillatory zoning and high Th/U ratios(0.39–1.35), implying their magmatic origin. Zircon LA-ICP-MS U-Pb dating results indicate that they formed during the Paleoproterozoic age with the weighted 206Pb/238 U average age of 1818±9 Ma, which is significantly different from former's Neoproterozoic age, and is coincidentally identical with its associated syenite granite age within the error range. Studies on petrogeochemistry suggest that DA belongs to medium-sodium peraluminous alkaline type, rich in Pb, La, Th and LILE, and poor in HFSE(Gd, Nd, and Ta). The chondrite-normalized REE pattern is slightly to the right form. The average ∑REE is 317.2×10-6; HREE show moderate fractionation [average LREE/HREE is 14.71, average(La/Yb)N is 24.77; average(La/Sm)N is 3.85, and average(Gd/Yb)N is 3.46]; and the δEu and δCe are not obvious. Their initial Hf isotope ratios and Hf two-stage model ages range from-6.6 to-4.43 and 2.63 to 2.74 Ga, respectively. Taken together, it is suggested that Daxigou anorthosite is a typical volcanic anorthosite and its primary magma could be contaminated by the partial melt Neoarchaean crust and mainly formed in the arc environment, which recoded the tectonic-magma activities response of the Tarim refers to the amalgamation of the supercontinent Columbia.
文摘The regional migmatites in the Yunkai Block were formed under low\|pressure metamorphism. The majority of their protolith are biotite\|rich peraluminous gneisses. Detailed field observations, and studies of petrology, spatial distribution of minerals and geochemistry suggest that the leucosomes were derived from anatexis. The single grain zircon U\|Pb dating data indicate that a pulse of migmatization occurred at 394～449 Ma and may have resulted from the large\|scale Caledonian magmatism in the Yunkai Block.
