The Neoproterozoic Kangdian Rift Basin is a continental rift basin in the western Yangtze Continent.Determining its time of opening and subsequent filling pattern is an important aspect of understanding the formation ...The Neoproterozoic Kangdian Rift Basin is a continental rift basin in the western Yangtze Continent.Determining its time of opening and subsequent filling pattern is an important aspect of understanding the formation and evolution of the Yangtze Continent,South China.The Luliang Formation is the early filling in the eastern part of this rift basin,and its deposition age and filling sequence are significant for studies of the regional stratigraphic correlation,opening time,and filling pattern of this basin.Having been correlated to the upper part of the Mesoproterozoic Kunyang Group or to the Neoproterozoic Chengjiang Formation,the age and regional stratigraphic correlation of the Luliang Formation have long been uncertain.This is due to a lack of reliable absolute age constraints.To address this issue,the first zircon SHRIMP U-Pb geochronology has been established for this formation,yielding two high-precision isotopic ages of 818.6±9.2 and 805±14 Ma for the tuff layers at the bottoms of the lower and upper members of the Luliang Formation,respectively.Given the error factor,the bottom age of the lower member of the Luliang Formation can be interpreted as ca.820 Ma,corresponding to the bottom age of the lower part of the Banxi Group,which is the early filling of the Neoproterozoic Xianggui Rift Basin,a representative basin of the Neoproterozoic rift basins in the Yangtze Continent,South China.The bottom age of the upper member of the Luliang Formation can be interpreted as ca.800±5 Ma,corresponding to the bottom age of the Chengjiang Formation in the western part of the Neoproterozoic Kangdian Rift Basin and also corresponding to the bottom age of the upper part of the Banxi Group in the Neoproterozoic Xianggui Rift Basin.These ages indicate that the Neoproterozoic Kangdian Rift Basin shares the same opening time and filling sequences as those of the other Neoproterozoic rift basins in South China.Basin analysis shows that the Neoproterozoic Kangdian Rift Basin is a typical half-graben basin,with its main boundary fault in the west and basin center in the east.This basin consisted of mini unidirectional half-graben basins in its juvenile stage and simplified to become a large united half-graben basin in its mature stage,i.e.,a supradetachment basin.展开更多
A gneissic granite with an U-Pb age of 313±4 Ma was found in northeastern Fujian Province,South China.It is an S-type granite characterized by high K2O,Al2O3 and low SiO2,Na2O contents with high A/CNK ratio of 1....A gneissic granite with an U-Pb age of 313±4 Ma was found in northeastern Fujian Province,South China.It is an S-type granite characterized by high K2O,Al2O3 and low SiO2,Na2O contents with high A/CNK ratio of 1.22 for the whole rock.Zircons with stubby morphology from the gneissic granite yield 206 Pb/238 U ages ranging from 326 to 301 Ma with a weighted average age of 313±4 Ma,and negative εHf(t) values from -8.35 to -1.74 with Hf model ages (TCDM) of 1.43 to 1.84 Ga.This S-type granite probably originated from late Paleoproterozoic crust in intracontinental orogeny.Integrated with previous results on paleogeographic reconstruction of South China,the nature of Paleozoic basins,Early Permian volcanism and U-Pb-Hf isotope of detrital zircons from the late Paleozoic to early Mesozoic sedimentary rocks,we suggest the occurrence of a late Paleozoic orogeny in the eastern Cathaysia Block,South China.This orogenic cycle includes Late Carboniferous (340-310 Ma) orogeny (compression) episode and Early Permian (287-270 Ma) post-orogenic or intraplate extension episode.Therefore,the late Paleozoic magmatism in the southeastern South China probably occurred during the intraplate orogeny rather than the arc-related process.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.4103031541072088)China Geological Survey(Grant No.1212011121105)
文摘The Neoproterozoic Kangdian Rift Basin is a continental rift basin in the western Yangtze Continent.Determining its time of opening and subsequent filling pattern is an important aspect of understanding the formation and evolution of the Yangtze Continent,South China.The Luliang Formation is the early filling in the eastern part of this rift basin,and its deposition age and filling sequence are significant for studies of the regional stratigraphic correlation,opening time,and filling pattern of this basin.Having been correlated to the upper part of the Mesoproterozoic Kunyang Group or to the Neoproterozoic Chengjiang Formation,the age and regional stratigraphic correlation of the Luliang Formation have long been uncertain.This is due to a lack of reliable absolute age constraints.To address this issue,the first zircon SHRIMP U-Pb geochronology has been established for this formation,yielding two high-precision isotopic ages of 818.6±9.2 and 805±14 Ma for the tuff layers at the bottoms of the lower and upper members of the Luliang Formation,respectively.Given the error factor,the bottom age of the lower member of the Luliang Formation can be interpreted as ca.820 Ma,corresponding to the bottom age of the lower part of the Banxi Group,which is the early filling of the Neoproterozoic Xianggui Rift Basin,a representative basin of the Neoproterozoic rift basins in the Yangtze Continent,South China.The bottom age of the upper member of the Luliang Formation can be interpreted as ca.800±5 Ma,corresponding to the bottom age of the Chengjiang Formation in the western part of the Neoproterozoic Kangdian Rift Basin and also corresponding to the bottom age of the upper part of the Banxi Group in the Neoproterozoic Xianggui Rift Basin.These ages indicate that the Neoproterozoic Kangdian Rift Basin shares the same opening time and filling sequences as those of the other Neoproterozoic rift basins in South China.Basin analysis shows that the Neoproterozoic Kangdian Rift Basin is a typical half-graben basin,with its main boundary fault in the west and basin center in the east.This basin consisted of mini unidirectional half-graben basins in its juvenile stage and simplified to become a large united half-graben basin in its mature stage,i.e.,a supradetachment basin.
基金supported by the National Basic Research Program of China(2012CB416701)the National Natural Science Foundation of China(40972127)the State Key Laboratory for Mineral Deposits Research(Nanjing University)(ZZKT-201106)
文摘A gneissic granite with an U-Pb age of 313±4 Ma was found in northeastern Fujian Province,South China.It is an S-type granite characterized by high K2O,Al2O3 and low SiO2,Na2O contents with high A/CNK ratio of 1.22 for the whole rock.Zircons with stubby morphology from the gneissic granite yield 206 Pb/238 U ages ranging from 326 to 301 Ma with a weighted average age of 313±4 Ma,and negative εHf(t) values from -8.35 to -1.74 with Hf model ages (TCDM) of 1.43 to 1.84 Ga.This S-type granite probably originated from late Paleoproterozoic crust in intracontinental orogeny.Integrated with previous results on paleogeographic reconstruction of South China,the nature of Paleozoic basins,Early Permian volcanism and U-Pb-Hf isotope of detrital zircons from the late Paleozoic to early Mesozoic sedimentary rocks,we suggest the occurrence of a late Paleozoic orogeny in the eastern Cathaysia Block,South China.This orogenic cycle includes Late Carboniferous (340-310 Ma) orogeny (compression) episode and Early Permian (287-270 Ma) post-orogenic or intraplate extension episode.Therefore,the late Paleozoic magmatism in the southeastern South China probably occurred during the intraplate orogeny rather than the arc-related process.
