Recently,a new kind of volcanic rock,felsite porphyry,has been revealed by drilling in Xiangshan area,Jiangxi Province,China.To better understand petrogenesis and magmatic evolution sequence of the Xiangshan volcanic-...Recently,a new kind of volcanic rock,felsite porphyry,has been revealed by drilling in Xiangshan area,Jiangxi Province,China.To better understand petrogenesis and magmatic evolution sequence of the Xiangshan volcanic-intrusive complex,we studied systematic petrology,geochemistry,LA-ICP-MS zircon U–Pb dating,and Hf isotope results of the felsite porphyry.Results show that the felsite porphyry has similar geochemical characteristics to the porphyroclastic rhyolite,which is the predominant lithology of Xiangshan uranium orefield.Felsite porphyry and porphyroclastic rhyolite have high SiO2,Al2O3,and K2O contents,low Na2O,and MgO contents,and slightly negative Eu anomalies.Moreover,these rocks are relatively depleted in large ion lithophile elements(K,Ba,and Sr)and are enriched in high field strength elements(Th,Zr,and Hf).LA-ICP-MS zircon U–Pb dating of the felsite porphyry yielded a crystallization age of 132.2±0.9 Ma,which is coeval to that of the porphyroclastic rhyolite.These ages signified that Xiangshan volcanic-intrusive complex formed in the Early Cretaceous,during which the entire South China was in the back-arc extension tectonic setting related to the subduction of the Pacific Plate under the Euroasian Plate.In-situ zircon Hf isotope data on a felsite porphyry sample show eHf(t)values from-8.82 to-5.11,while the Hf isotope two-stage model age(TDM2-Hf)ranges from 1513 to 1747 Ma.Combined with petrological,mineralogical,geochemistry,and geochronology results of the felsite porphyry,it is concluded that the felsite porphyry in Xiangshan might be originated from the partial melting of the Mesoproterozoic ancient metamorphic rocks,with possible input of small amounts of mantle materials.展开更多
Through the finite-element modeling. a quantitative analysis of paleogeothermal evolution after the main volcanic eruption at Cretaceous period for the Xiangshan uranium ore-field. East China. has been presented. Rese...Through the finite-element modeling. a quantitative analysis of paleogeothermal evolution after the main volcanic eruption at Cretaceous period for the Xiangshan uranium ore-field. East China. has been presented. Researches reveal that the energy from the volcanic lava could affect the geothermal field for only three million years after their eruption. and could not provide heat for the Xiangshan uranium ore-foming hydrothermal system because the time gap between the volcanic activities and the uranium mineralizations is longer than 40 million years. The evidences show that the heat energy for the ore-forming system came from anomalously high paleogeothermal gradient in the study area during the mineralization period.展开更多
基金“Comprehensive Study of 3D Metallogenic Geologic Environment of Key Zones for Exploration in Xiangshan Uranium Orefield”the sub-project of“Longcan Science and Technology Innovation Demonstration Project”of China National Nuclear Corporation(Project No.:LCD116)。
文摘Recently,a new kind of volcanic rock,felsite porphyry,has been revealed by drilling in Xiangshan area,Jiangxi Province,China.To better understand petrogenesis and magmatic evolution sequence of the Xiangshan volcanic-intrusive complex,we studied systematic petrology,geochemistry,LA-ICP-MS zircon U–Pb dating,and Hf isotope results of the felsite porphyry.Results show that the felsite porphyry has similar geochemical characteristics to the porphyroclastic rhyolite,which is the predominant lithology of Xiangshan uranium orefield.Felsite porphyry and porphyroclastic rhyolite have high SiO2,Al2O3,and K2O contents,low Na2O,and MgO contents,and slightly negative Eu anomalies.Moreover,these rocks are relatively depleted in large ion lithophile elements(K,Ba,and Sr)and are enriched in high field strength elements(Th,Zr,and Hf).LA-ICP-MS zircon U–Pb dating of the felsite porphyry yielded a crystallization age of 132.2±0.9 Ma,which is coeval to that of the porphyroclastic rhyolite.These ages signified that Xiangshan volcanic-intrusive complex formed in the Early Cretaceous,during which the entire South China was in the back-arc extension tectonic setting related to the subduction of the Pacific Plate under the Euroasian Plate.In-situ zircon Hf isotope data on a felsite porphyry sample show eHf(t)values from-8.82 to-5.11,while the Hf isotope two-stage model age(TDM2-Hf)ranges from 1513 to 1747 Ma.Combined with petrological,mineralogical,geochemistry,and geochronology results of the felsite porphyry,it is concluded that the felsite porphyry in Xiangshan might be originated from the partial melting of the Mesoproterozoic ancient metamorphic rocks,with possible input of small amounts of mantle materials.
文摘Through the finite-element modeling. a quantitative analysis of paleogeothermal evolution after the main volcanic eruption at Cretaceous period for the Xiangshan uranium ore-field. East China. has been presented. Researches reveal that the energy from the volcanic lava could affect the geothermal field for only three million years after their eruption. and could not provide heat for the Xiangshan uranium ore-foming hydrothermal system because the time gap between the volcanic activities and the uranium mineralizations is longer than 40 million years. The evidences show that the heat energy for the ore-forming system came from anomalously high paleogeothermal gradient in the study area during the mineralization period.
