This paper reports petrological and geochemical features and zircon U-Pb age of plagiogranite from the Hongliugou-Lapeiquan ophiolitic melange belt in the northern Altyn Tagh. The zircon U-Pb dating results yield a me...This paper reports petrological and geochemical features and zircon U-Pb age of plagiogranite from the Hongliugou-Lapeiquan ophiolitic melange belt in the northern Altyn Tagh. The zircon U-Pb dating results yield a mean ^238U/^206pb age of 512.1 ± 1.5 Ma, representing an emplacement time of the plagiogranites in the Middle Cambrian. The plagiogranites are interpreted to have derived from anatexis of hydrated amphibolites by ductile shearing during transports of the oceanic crust. Thus it is believed that the formation age of such type of plagiogranite was coeval to or slightly younger than the spreading of the Hongliugou-Lapeiquan limited oceanic basin. The new results from the plagiogranites suggest that an oceanic basin existed in the northern Altyn area during the Middle Cambrian.展开更多
The Yinisala ophiolitic melange is located in the southern part of the Xiemisitai Mountains in western Junggar （NW China）, and is composed of mafic-ultra mafic rocks, siliceous blocks, marble （marbleized limestone...The Yinisala ophiolitic melange is located in the southern part of the Xiemisitai Mountains in western Junggar （NW China）, and is composed of mafic-ultra mafic rocks, siliceous blocks, marble （marbleized limestone） and pyroclastic rocks, which all crop out as faulted blocks. Rich radiolarian and sponge spicule fossils are found in the siliceous rock for the first time. There are six genera of radiolarians （including one gen. et sp. Indet.） belonging to two families： Inaniguttid gen. et sp. Indet., Inani- gutta sp., Inanibigutta sp., Inanihella bakanasensis （Nazarov）, Triplococcus acanthicus （Danelian and Popov）, Antygopora sp., which are identified to be of late Early to Middle Ordovician age, representing the upper limit of the formation age of the Yinisala ophiolite melange. The ophiolites were developed in the Early Cambrian-Middle Ordovician oceanic environment, probably an important part of the early Paleozoic Paleo-Asian Ocean, based on the composition and structure of the siliceous rock and associated deep-water fossils. The Yinisala, Taerbahatai, and Hongguleleng ophiolitic melange belts can be correlated as a suite of unified subduction accretionary complex, which extends eastward to the eastern Junggar. We consider that there existed an ancient ocean connecting the east and west of northern Junggar in the Early Cambrian-Middle Ordovician.展开更多
基金financially supported by the China Geological Survey (Grant No. 1212010911025)National Natural Science Foundation of China (Grant No. 41002020)
文摘This paper reports petrological and geochemical features and zircon U-Pb age of plagiogranite from the Hongliugou-Lapeiquan ophiolitic melange belt in the northern Altyn Tagh. The zircon U-Pb dating results yield a mean ^238U/^206pb age of 512.1 ± 1.5 Ma, representing an emplacement time of the plagiogranites in the Middle Cambrian. The plagiogranites are interpreted to have derived from anatexis of hydrated amphibolites by ductile shearing during transports of the oceanic crust. Thus it is believed that the formation age of such type of plagiogranite was coeval to or slightly younger than the spreading of the Hongliugou-Lapeiquan limited oceanic basin. The new results from the plagiogranites suggest that an oceanic basin existed in the northern Altyn area during the Middle Cambrian.
基金supported by China Geological Survey(Grant No.1212011120502)National Natural Science Foundation of China(Grant Nos.41472001,41290260)the Special Research Fund for the Doctoral Program of Higher Education of China(Grant No.2012014-5110012)
文摘The Yinisala ophiolitic melange is located in the southern part of the Xiemisitai Mountains in western Junggar （NW China）, and is composed of mafic-ultra mafic rocks, siliceous blocks, marble （marbleized limestone） and pyroclastic rocks, which all crop out as faulted blocks. Rich radiolarian and sponge spicule fossils are found in the siliceous rock for the first time. There are six genera of radiolarians （including one gen. et sp. Indet.） belonging to two families： Inaniguttid gen. et sp. Indet., Inani- gutta sp., Inanibigutta sp., Inanihella bakanasensis （Nazarov）, Triplococcus acanthicus （Danelian and Popov）, Antygopora sp., which are identified to be of late Early to Middle Ordovician age, representing the upper limit of the formation age of the Yinisala ophiolite melange. The ophiolites were developed in the Early Cambrian-Middle Ordovician oceanic environment, probably an important part of the early Paleozoic Paleo-Asian Ocean, based on the composition and structure of the siliceous rock and associated deep-water fossils. The Yinisala, Taerbahatai, and Hongguleleng ophiolitic melange belts can be correlated as a suite of unified subduction accretionary complex, which extends eastward to the eastern Junggar. We consider that there existed an ancient ocean connecting the east and west of northern Junggar in the Early Cambrian-Middle Ordovician.
