The Mesoproterozoic Dongchuan Group that is widely exposed in Yimen area,central Yunnan Province is a series of sedimentary sort of low-grade metamorphic rocks interbedded with volcanic rocks,which are closely related...The Mesoproterozoic Dongchuan Group that is widely exposed in Yimen area,central Yunnan Province is a series of sedimentary sort of low-grade metamorphic rocks interbedded with volcanic rocks,which are closely related to the early tectonic evolution of the Earth.However,its formation era,sedimentary filling sequence,and geotectonic characteristics have always been in dispute.In this study,several rhyolitic tuffaceous slate interlayers with a centimeter-level thickness were found in the previously determined Heishan Formation of the Dongchuan Group located to the western part of Yimen-Luoci fault zone.This paper focuses on the study of the rhyolitic tuffaceous slate in Qifulangqing Village,Tongchang Township,Yimen County.LA-ICP-MS zircon dating was conducted,achieving the crystallization age of magma of 2491±15 Ma and the metamorphic ages of about 2.3 Ga,2.0 Ga,and 1.8 Ga for the first time.Meanwhile,according to in-situ Hf isotope analysis,the zirconεHf(t)values were determined to range from−3.0 to 7.6,with an average of 2.7.Furthermore,the first-stage Hf model age(TDM1)was determined to be 2513−2916 Ma,indicating that the provenance of the rhyolitic tuffaceous slate is the depleted mantle or juvenile crust between the Middle Mesoarchean and the Late Neoarchean.Therefore,it is believed that the strata of the slate were deposited in the Late Neoarchean,instead of the Mesoproterozoic as determined by previous researchers.Accordingly,it is not appropriate to group the strata into the Mesoproterozoic Dongchuan Group.Instead,they should be classified as the Maolu Formation of the Neoarchean Puduhe Group given the lithologic association and regional information.Furthermore,the magma ages of 2491±15 Ma are highly consistent with the eras of the large-scale Late Neoarchean orogenic magmatic activities on the northern margin of the Yangtze Craton,and thus reflect the orogenic process consisting of subduction and collision from Late Neoarchean to Early Paleoproterozoic.The magmatic activities during this period were展开更多
The Pearl River Mouth Basin(PRMB)is one of the most petroliferous basins on the northern margin of the South China Sea.Knowledge of the thermal history of the PRMB is significant for understanding its tectonic evoluti...The Pearl River Mouth Basin(PRMB)is one of the most petroliferous basins on the northern margin of the South China Sea.Knowledge of the thermal history of the PRMB is significant for understanding its tectonic evolution and for unraveling its poorly studied source-rock maturation history.Our investigations in this study are based on apatite fission-track(AFT)thermochronology analysis of 12 cutting samples from 4 boreholes.Both AFT ages and length data suggested that the PRMB has experienced quite complicated thermal evolution.Thermal history modeling results unraveled four successive events of heating separated by three stages of cooling since the early Middle Eocene.The cooling events occurred approximately in the Late Eocene,early Oligocene,and the Late Miocene,possibly attributed to the Zhuqiong II Event,Nanhai Event,and Dongsha Event,respectively.The erosion amount during the first cooling stage is roughly estimated to be about 455-712 m,with an erosion rate of 0.08-0.12 mm/a.The second erosion-driven cooling is stronger than the first one,with an erosion amount of about 747-814 m and an erosion rate between about 0.13-0.21 mm/a.The erosion amount calculated related to the third cooling event varies from 800 m to 3419 m,which is speculative due to the possible influence of the magmatic activity.展开更多
1 Introduction The Weibei Uplift is located in the southwest of the North China Plate,where is the stable block(the Ordos Block)in the north and the active belt(the QinlingOrogenic Belt)in the south(Ren et al,2014,201...1 Introduction The Weibei Uplift is located in the southwest of the North China Plate,where is the stable block(the Ordos Block)in the north and the active belt(the QinlingOrogenic Belt)in the south(Ren et al,2014,2015).And the belt is separated from the Weihe basin.The Weibei uplift has a uniform crystalline basement with the North展开更多
All gold deposits in North-Eastern Hunan are of vein type, and hosted by the low grade metamorphic rocks of Lengjiaxi Group of the Middle Proterozoic Era. Their geochemical characteristics show that the ore-forming ma...All gold deposits in North-Eastern Hunan are of vein type, and hosted by the low grade metamorphic rocks of Lengjiaxi Group of the Middle Proterozoic Era. Their geochemical characteristics show that the ore-forming materials came from their host rocks. Oreforming fluids are rich in CO2 and SO2-4,with high Na+/K+ ratio, low Cl - and varied δ18O and δD values, showing that they are from multisources. These gold deposits were formed by a series of tectonic-thermal events which reworked the Lengjiaxi Group. There are two main stages of tectonic-thermal events: the Wulingian Period forming the auriferous quartz veins by syntectonic metamorphic differentiation, and the Indosinian-Yanshanian peroid causing re formation and enrichment of the former auriferous quartz veins.展开更多
基金The work was financially supported by Project of 1∶50000 Regional Geological Survey of Samaki,Yinmin,Guicheng and Shugu Sheets in Yunnan Province by Land and Resources Department of Yunnan Province(D201905)Project of 1∶50000 Regional Geological Survey of Erjie,Yimen,Mingyihe and Shangpubei Sheets in Yunnan Province(DD20160017)Regional Geological Survey Area Summary and Service Product Development in Yunnan Province by China Geological Survey(121201102000150012-02).
文摘The Mesoproterozoic Dongchuan Group that is widely exposed in Yimen area,central Yunnan Province is a series of sedimentary sort of low-grade metamorphic rocks interbedded with volcanic rocks,which are closely related to the early tectonic evolution of the Earth.However,its formation era,sedimentary filling sequence,and geotectonic characteristics have always been in dispute.In this study,several rhyolitic tuffaceous slate interlayers with a centimeter-level thickness were found in the previously determined Heishan Formation of the Dongchuan Group located to the western part of Yimen-Luoci fault zone.This paper focuses on the study of the rhyolitic tuffaceous slate in Qifulangqing Village,Tongchang Township,Yimen County.LA-ICP-MS zircon dating was conducted,achieving the crystallization age of magma of 2491±15 Ma and the metamorphic ages of about 2.3 Ga,2.0 Ga,and 1.8 Ga for the first time.Meanwhile,according to in-situ Hf isotope analysis,the zirconεHf(t)values were determined to range from−3.0 to 7.6,with an average of 2.7.Furthermore,the first-stage Hf model age(TDM1)was determined to be 2513−2916 Ma,indicating that the provenance of the rhyolitic tuffaceous slate is the depleted mantle or juvenile crust between the Middle Mesoarchean and the Late Neoarchean.Therefore,it is believed that the strata of the slate were deposited in the Late Neoarchean,instead of the Mesoproterozoic as determined by previous researchers.Accordingly,it is not appropriate to group the strata into the Mesoproterozoic Dongchuan Group.Instead,they should be classified as the Maolu Formation of the Neoarchean Puduhe Group given the lithologic association and regional information.Furthermore,the magma ages of 2491±15 Ma are highly consistent with the eras of the large-scale Late Neoarchean orogenic magmatic activities on the northern margin of the Yangtze Craton,and thus reflect the orogenic process consisting of subduction and collision from Late Neoarchean to Early Paleoproterozoic.The magmatic activities during this period were
基金This study is financially supported by the National Natural Science Foundation of China(42072181).
文摘The Pearl River Mouth Basin(PRMB)is one of the most petroliferous basins on the northern margin of the South China Sea.Knowledge of the thermal history of the PRMB is significant for understanding its tectonic evolution and for unraveling its poorly studied source-rock maturation history.Our investigations in this study are based on apatite fission-track(AFT)thermochronology analysis of 12 cutting samples from 4 boreholes.Both AFT ages and length data suggested that the PRMB has experienced quite complicated thermal evolution.Thermal history modeling results unraveled four successive events of heating separated by three stages of cooling since the early Middle Eocene.The cooling events occurred approximately in the Late Eocene,early Oligocene,and the Late Miocene,possibly attributed to the Zhuqiong II Event,Nanhai Event,and Dongsha Event,respectively.The erosion amount during the first cooling stage is roughly estimated to be about 455-712 m,with an erosion rate of 0.08-0.12 mm/a.The second erosion-driven cooling is stronger than the first one,with an erosion amount of about 747-814 m and an erosion rate between about 0.13-0.21 mm/a.The erosion amount calculated related to the third cooling event varies from 800 m to 3419 m,which is speculative due to the possible influence of the magmatic activity.
基金supported by Natural Science Foundation of China (Project No. 41630312)The National Nature Science Foundation of China (Project No. 41372208 and 40534019)The Open Found of the State Key Laboratory of Ore Deposit Geochemistry, CAS(Project No. 201304)
文摘1 Introduction The Weibei Uplift is located in the southwest of the North China Plate,where is the stable block(the Ordos Block)in the north and the active belt(the QinlingOrogenic Belt)in the south(Ren et al,2014,2015).And the belt is separated from the Weihe basin.The Weibei uplift has a uniform crystalline basement with the North
文摘All gold deposits in North-Eastern Hunan are of vein type, and hosted by the low grade metamorphic rocks of Lengjiaxi Group of the Middle Proterozoic Era. Their geochemical characteristics show that the ore-forming materials came from their host rocks. Oreforming fluids are rich in CO2 and SO2-4,with high Na+/K+ ratio, low Cl - and varied δ18O and δD values, showing that they are from multisources. These gold deposits were formed by a series of tectonic-thermal events which reworked the Lengjiaxi Group. There are two main stages of tectonic-thermal events: the Wulingian Period forming the auriferous quartz veins by syntectonic metamorphic differentiation, and the Indosinian-Yanshanian peroid causing re formation and enrichment of the former auriferous quartz veins.
