| The Origin of Bedded Cherts of the Early Permian Gufeng Formation in the Lower Yangtze Area, Eastern China |
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| 作者姓名： | Xia Bangdong Zhong Lirong Fang Zhong and Lu Hongbo |
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| 作者单位： | Xia Bangdong，Zhong Lirong，Fang Zhong and Lu HongboDepartment of Earth Sciences，Nanjing University，Nanjing，Jiangsu Fei Zhenbi |
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| 基金项目： | This study was supported by China National Natural Science Foundation Grant 4880131 |
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| 摘 要： | Bedded cherts occurring in the Early Permian Gufeng Formation in the Lower Yangtze region, eastern China, are nearly 20-80 m in thickness and contain varying amounts of radiolarians and sponge spicules. There are three types of section for the Gufeng Formation: chert, carbonate and chert-carbonate mixing types. Bedded cherts mainly occur in the first and third types of section. The depocentres of silica are marked by some small (not larger than a few thousand square kilometres in area) rhombic or elliptic hollows and their formation was controlled by faults. Argillaceous volcanic rocks in cherts occur as numerous thin layers. Bedded cherts are characterized by higher Fe and lower Al contents, enrichment in such trace elements as As, Sb, Bi, Ga, Au, Ag and Cr, lower total REE abundance, negative Ce anomaly and varying degrees of HREE enrichment. These characteristics are important evidence for hydrothermal cherts. Minor amounts of substances of non-hydrothermal origin are mixed in the cherts. The tempera
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The Origin of Bedded Cherts of the Early Permian Gufeng Formation in the Lower Yangtze Area, Eastern China |
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| Authors: | Xia Bangdong Zhong Lirong Fang Zhong and Lu Hongbo |
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| Institution: | Xia Bangdong,Zhong Lirong,Fang Zhong and Lu HongboDepartment of Earth Sciences,Nanjing University,Nanjing,Jiangsu Fei Zhenbi |
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| Abstract: | Abstract Bedded cherts occurring in the Early Permian Gufeng Formation in the Lower Yangtze region, eastern China, are nearly 20-80 m in thickness and contain varying amounts of radiolarians and sponge spicules. There are three types of section for the Gufeng Formation: chert, carbonate and chert - carbonate mixing types. Bedded cherts mainly occur in the first and third types of section. The depocentres of silica are marked by some small (not larger than a few thousand square kilometres in area) rhombic or elliptic hollows and their formation was controlled by faults. Argillaceous volcanic rocks in cherts occur as numerous thin layers. Bedded cherts are characterized by higher Fe and lower Al contents, enrichment in such trace elements as As, Sb, Bi, Ga, Au, Ag and Cr, lower total REE abundance, negative Ce anomaly and varying degrees of HREE enrichment. These characteristics are important evidence for hydrothermal cherts. Minor amounts of substances of non - hydrothermal origin are mixed in the cherts. The temperatures of sea water range approximately from a few tens of degrees to over 160°C. during the deposition of siliceous sediments. |
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| Keywords: | hydrothermal cherts argillaceous volcanic rocks radiolarian |
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