Objective Lhasa terrane has recorded the geologic history conceming the formation and evolution of Paleo-Tethys and the intra-continental convergence in Qinghai-Tibet Plateau （Yin and Harrison, 2000）. Previous inve...Objective Lhasa terrane has recorded the geologic history conceming the formation and evolution of Paleo-Tethys and the intra-continental convergence in Qinghai-Tibet Plateau （Yin and Harrison, 2000）. Previous investigations have focused on the initial timing of the India-Asia collision and the Cretaceous-Cenozoic magmatism and sedimentation （Wang Tianyang et al., 2017）, however, there are only few studies concerning the Paleozoic evolution in Lhasa terrane. This paper mainly reports a new discovery of 341 Ma gabbro, which is located in the Xiongcun copper-gold district at the southern margin of Lhasa terrane, Tibet. As an important magmatic record during the Paleozoic evolution process of Lhasa terrane, the Early Carboniferous Xiongcun gabbro will provide new constraints for the tectonic evolution of Paleo-Tethys Ocean in the Late Devonian to Early Carboniferous.展开更多
The Tiegelongnan Cu(Au,Ag)deposit in central Tibet contains more than 10 Mt of copper ranking 29 th in the world.It is characterized by typical porphyry-epithermal alteration and mineralization.In order to improve the...The Tiegelongnan Cu(Au,Ag)deposit in central Tibet contains more than 10 Mt of copper ranking 29 th in the world.It is characterized by typical porphyry-epithermal alteration and mineralization.In order to improve the understanding of porphyry-epithermal copper deposit in Tibet,new zircon U-Pb age and sulfur isotope data along with published data in the Tiegelongnan are presented to investigate the formation and preservation mechanism.Ore-related intrusive rocks in the Tiegelongnan including Early Cretaceous(about 120 Ma)granodiorite porphyry and diorite porphyry are closely related to the northward subduction of Bangongco-Nujiang ocean.Sulfur mainly comes from deep magma,and ore-forming fluid is affected by both magmatic and meteoric water.The metallogenic setting of Tiegelongnan is consistent with those of Andean porphyry copper deposits in South America.The cover of the Meiriqiecuo Formation volcanic rocks,Lhasa-Qiangtang collision and India-Eurasian collision have significance in the preservation and uplift of the deposit.The formation,preservation and discovery of Tiegelongnan play an important role in exploration of ancient porphyry-epithermal deposits in Tibet.展开更多
Early-crystallizing chromian spinel(Cr-spinel) in the Nagqu ophiolite has high Os and low Re contents,and it is resistant to alteration during serpentinization,weathering and metamorphism.The chemical composition of p...Early-crystallizing chromian spinel(Cr-spinel) in the Nagqu ophiolite has high Os and low Re contents,and it is resistant to alteration during serpentinization,weathering and metamorphism.The chemical composition of primitive magma is preserved in Cr-spinel,which makes it suitable for determining the initial Os-isotope composition of the mantle source.This study presents Cr-spinel Os isotopes and zircon U-Pb ages for cumulate dunite and gabbro,respectively,in the same cumulate section of the ophiolite at Nagqu in Tibet.The results shed light on the formation and evolution of lithospheric mantle.The Nagqu ophiolite is located in the central part of the Bangong-Nujiang suture zone.It is a remnant of the Neotethyan oceanic crust,and contains cumulate dunite and gabbro.Zircon from the gabbro yielded a weighted mean 206 Pb/238 U age of 183.7±1 Ma.Cr-spinel exhibits Os values of 0.2 to 0.3,suggesting that the mantle source for the dunite is similar to that of carbonaceous chondrites.Thus,the Tibetan lithosphere is primarily a relic of Tethyan oceanic lithosphere,which has formed by the transformation of the normal asthenospheric mantle in the Mesozoic.This is the first study to combine the spinel Os isotopes with accurate zircon U-Pb ages to constrain the geochemical characteristics of the mantle source for the ophiolite.展开更多
基金financially supported by the National Natural Science Foundation of China(grant No.41502079)China Geological Survey(grants No.[2012]03-002-055 and [2014]01-028-042)
文摘Objective Lhasa terrane has recorded the geologic history conceming the formation and evolution of Paleo-Tethys and the intra-continental convergence in Qinghai-Tibet Plateau （Yin and Harrison, 2000）. Previous investigations have focused on the initial timing of the India-Asia collision and the Cretaceous-Cenozoic magmatism and sedimentation （Wang Tianyang et al., 2017）, however, there are only few studies concerning the Paleozoic evolution in Lhasa terrane. This paper mainly reports a new discovery of 341 Ma gabbro, which is located in the Xiongcun copper-gold district at the southern margin of Lhasa terrane, Tibet. As an important magmatic record during the Paleozoic evolution process of Lhasa terrane, the Early Carboniferous Xiongcun gabbro will provide new constraints for the tectonic evolution of Paleo-Tethys Ocean in the Late Devonian to Early Carboniferous.
基金funded by the National Natural Science Foundation of China(42002103)the Technical Service for Quality Monitoring of Mineral Exploration in Tiegelongnan Mining Area,Duolong Ore district,Gaize County,Tibet(XZJL-JS-2021-004)+1 种基金the Chinese Geological Survey(DD20190167)the Basal Research Fund of Chinese Academy of Geological Sciences(KK2017)。
文摘The Tiegelongnan Cu(Au,Ag)deposit in central Tibet contains more than 10 Mt of copper ranking 29 th in the world.It is characterized by typical porphyry-epithermal alteration and mineralization.In order to improve the understanding of porphyry-epithermal copper deposit in Tibet,new zircon U-Pb age and sulfur isotope data along with published data in the Tiegelongnan are presented to investigate the formation and preservation mechanism.Ore-related intrusive rocks in the Tiegelongnan including Early Cretaceous(about 120 Ma)granodiorite porphyry and diorite porphyry are closely related to the northward subduction of Bangongco-Nujiang ocean.Sulfur mainly comes from deep magma,and ore-forming fluid is affected by both magmatic and meteoric water.The metallogenic setting of Tiegelongnan is consistent with those of Andean porphyry copper deposits in South America.The cover of the Meiriqiecuo Formation volcanic rocks,Lhasa-Qiangtang collision and India-Eurasian collision have significance in the preservation and uplift of the deposit.The formation,preservation and discovery of Tiegelongnan play an important role in exploration of ancient porphyry-epithermal deposits in Tibet.
基金supported by the National Basic Research Program of China (2011CB403101)the National Natural Science Foundation of China (41172059,40972056 and 40930316)
文摘Early-crystallizing chromian spinel(Cr-spinel) in the Nagqu ophiolite has high Os and low Re contents,and it is resistant to alteration during serpentinization,weathering and metamorphism.The chemical composition of primitive magma is preserved in Cr-spinel,which makes it suitable for determining the initial Os-isotope composition of the mantle source.This study presents Cr-spinel Os isotopes and zircon U-Pb ages for cumulate dunite and gabbro,respectively,in the same cumulate section of the ophiolite at Nagqu in Tibet.The results shed light on the formation and evolution of lithospheric mantle.The Nagqu ophiolite is located in the central part of the Bangong-Nujiang suture zone.It is a remnant of the Neotethyan oceanic crust,and contains cumulate dunite and gabbro.Zircon from the gabbro yielded a weighted mean 206 Pb/238 U age of 183.7±1 Ma.Cr-spinel exhibits Os values of 0.2 to 0.3,suggesting that the mantle source for the dunite is similar to that of carbonaceous chondrites.Thus,the Tibetan lithosphere is primarily a relic of Tethyan oceanic lithosphere,which has formed by the transformation of the normal asthenospheric mantle in the Mesozoic.This is the first study to combine the spinel Os isotopes with accurate zircon U-Pb ages to constrain the geochemical characteristics of the mantle source for the ophiolite.
