The Qinling Complex from the Qinling orogenic belt was generally considered to be part of the Caledonian orogeny, however information of the Grenville event of the Qinling Complex has been poorly recognized. Two grani...The Qinling Complex from the Qinling orogenic belt was generally considered to be part of the Caledonian orogeny, however information of the Grenville event of the Qinling Complex has been poorly recognized. Two granite samples of greenschist-facies and two paragneiss samples of amphibolitefaices are identified from the Qinling Complex. The granites occur along the regional gneissosity of the Qinling Complex, thus it is suggested that their magmatic zircon ages(~970 Ma) mark the lower boundary of the main metamorphic age(amphibolite-granulite facies). In addition, some early-formed metamorphic zircons(~1 000 Ma) are distinguished in the granites, which may reflect the information about the source area of the granites. Therefore the major metamorphism of amphibolite-granulite facies in the Qinling Complex is constrained at Early Neoproterozoic(~1 000 Ma), not Early Paleozoic as conventionally considered. In the Early Paleozoic, the Qinling Complex was characterized by multiple extension-shear activities, overprint of greenschist-facies metamorphism and emplacement of extensive granites. These granites and related thermal events could reset the U-Pb isotopic system of the early-formed zircons, leading to the apparent zircon ages younger than their protolith age. As a result, the Qinling Complex is a modified Early Neoproterozoic orognenic belt or an independent block, which became a continental margin arc during the Early Paleozoic, being accompanied by metamorphism, deformation, and emplacement of continental arc granites. The Erlangping, Kuanping, and Taowan groups to the north of the Qinling Complex show more intensive deformation of the Caledonian, and their oblique subduction towards the Qinling Complex caused the formation of eclogites. Afterwards, the Qinling Complex was amalgamated with the Erlangping, Kuanping, and Taowan groups, which all experienced the same Caledonian orogeny, and possible later orogenies.展开更多
We carried out SHRIMP zircon U-Pb dating on A-type granitic intrusions from the Namaqua-Natal Province,South Africa,Sverdrupfjella,western Dronning Maud Land,Antarctica and the Nampula Province of northern Mozambique....We carried out SHRIMP zircon U-Pb dating on A-type granitic intrusions from the Namaqua-Natal Province,South Africa,Sverdrupfjella,western Dronning Maud Land,Antarctica and the Nampula Province of northern Mozambique.Zircon grains in these granitic rocks are typically elongated and oscillatory zoned,suggesting magmatic origins.Zircons from the granitoid intrusions analyzed in this study suggest^1025-1100 Ma ages,which confirm widespread Mesoproterozoic A-type granitic magmatism in the Namaqua-Natal(South Africa),Maud(Antarctica)and Mozambique metamorphic terrains.No older inherited(e.g.,~2500 Ma Achean basement or^1200 Ma island are magmatism in northern Natal)zircon grains were seen.Four plutons from the Natal Belt(Mvoti Pluton,Glendale Pluton,Kwalembe Pluton,Ntimbankulu Pluton)display 1050-1040 Ma ages,whereas the Nthlimbitwa Pluton in northern Natal indicates older 1090-1080 Ma ages.A sample from Sverdrupfjella,Antarctica has^1091 Ma old zircons along with^530 Ma metamorphic rims.Similarly,four samples analysed from the Nampula Province of Mozambique suggest crystallization ages of^1060-1090 Ma but also show significant discordance with two samples showing younger^550 Ma overgrowths.None of the Natal samples show any younger overgrowths.A single sample from southwestern Namaqualand yielded an age of^1033 Ma.Currently available chronological data suggest magmatism took place in the Namaqua-Natal-MaudMozambique(NNMM)belt between^1025 Ma and^1100 Ma with two broad phases between^1060-1020 Ma and 1100-1070 Ma respectively,with peaks at between^1030-1040 Ma and^1070-1090 Ma.The age data from the granitic intrusions from Namaqualand.combined with those from Natal,Antarctica and Mozambique suggest a crude spatial-age relationship with the older>1070 Ma ages being largely restricted close to the eastern and western margins of the Kalahari Craton in northern Natal,Mozambique.Namaqualand and WDML Antarctica whereas the younger<1060 Ma ages dominate in southern Natal and western Namaqualand and are largely restricted to 展开更多
基金supported by the China Geological Survey (Nos. DD20190358, 20190370 and 20190448)the National Natural Science Foundation of China (No. 41472172)
文摘The Qinling Complex from the Qinling orogenic belt was generally considered to be part of the Caledonian orogeny, however information of the Grenville event of the Qinling Complex has been poorly recognized. Two granite samples of greenschist-facies and two paragneiss samples of amphibolitefaices are identified from the Qinling Complex. The granites occur along the regional gneissosity of the Qinling Complex, thus it is suggested that their magmatic zircon ages(~970 Ma) mark the lower boundary of the main metamorphic age(amphibolite-granulite facies). In addition, some early-formed metamorphic zircons(~1 000 Ma) are distinguished in the granites, which may reflect the information about the source area of the granites. Therefore the major metamorphism of amphibolite-granulite facies in the Qinling Complex is constrained at Early Neoproterozoic(~1 000 Ma), not Early Paleozoic as conventionally considered. In the Early Paleozoic, the Qinling Complex was characterized by multiple extension-shear activities, overprint of greenschist-facies metamorphism and emplacement of extensive granites. These granites and related thermal events could reset the U-Pb isotopic system of the early-formed zircons, leading to the apparent zircon ages younger than their protolith age. As a result, the Qinling Complex is a modified Early Neoproterozoic orognenic belt or an independent block, which became a continental margin arc during the Early Paleozoic, being accompanied by metamorphism, deformation, and emplacement of continental arc granites. The Erlangping, Kuanping, and Taowan groups to the north of the Qinling Complex show more intensive deformation of the Caledonian, and their oblique subduction towards the Qinling Complex caused the formation of eclogites. Afterwards, the Qinling Complex was amalgamated with the Erlangping, Kuanping, and Taowan groups, which all experienced the same Caledonian orogeny, and possible later orogenies.
基金supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science to K.S.(Nos.09041116and 13440151)a Grant-in-Aid for the Young Scientists from JSPS to T.H.Antarctic Research funding to GHG from the NRF,SouthAfrica,Grant ID.110739
文摘We carried out SHRIMP zircon U-Pb dating on A-type granitic intrusions from the Namaqua-Natal Province,South Africa,Sverdrupfjella,western Dronning Maud Land,Antarctica and the Nampula Province of northern Mozambique.Zircon grains in these granitic rocks are typically elongated and oscillatory zoned,suggesting magmatic origins.Zircons from the granitoid intrusions analyzed in this study suggest^1025-1100 Ma ages,which confirm widespread Mesoproterozoic A-type granitic magmatism in the Namaqua-Natal(South Africa),Maud(Antarctica)and Mozambique metamorphic terrains.No older inherited(e.g.,~2500 Ma Achean basement or^1200 Ma island are magmatism in northern Natal)zircon grains were seen.Four plutons from the Natal Belt(Mvoti Pluton,Glendale Pluton,Kwalembe Pluton,Ntimbankulu Pluton)display 1050-1040 Ma ages,whereas the Nthlimbitwa Pluton in northern Natal indicates older 1090-1080 Ma ages.A sample from Sverdrupfjella,Antarctica has^1091 Ma old zircons along with^530 Ma metamorphic rims.Similarly,four samples analysed from the Nampula Province of Mozambique suggest crystallization ages of^1060-1090 Ma but also show significant discordance with two samples showing younger^550 Ma overgrowths.None of the Natal samples show any younger overgrowths.A single sample from southwestern Namaqualand yielded an age of^1033 Ma.Currently available chronological data suggest magmatism took place in the Namaqua-Natal-MaudMozambique(NNMM)belt between^1025 Ma and^1100 Ma with two broad phases between^1060-1020 Ma and 1100-1070 Ma respectively,with peaks at between^1030-1040 Ma and^1070-1090 Ma.The age data from the granitic intrusions from Namaqualand.combined with those from Natal,Antarctica and Mozambique suggest a crude spatial-age relationship with the older>1070 Ma ages being largely restricted close to the eastern and western margins of the Kalahari Craton in northern Natal,Mozambique.Namaqualand and WDML Antarctica whereas the younger<1060 Ma ages dominate in southern Natal and western Namaqualand and are largely restricted to
