Carbon isotopic variations of Proterozoic carbonates in Jixian,Tianjin, China |
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Authors: | Email author" target="_blank">Xuelei?ChuEmail author Tonggang?Zhang Qirui?Zhang Lianjun?Feng Fusong?Zhang |
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Institution: | 1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;Key Laboratory for Mineral Resources Research, Chinese Academy of Sciences, Beijing 100029, China 2. Key Laboratory for Mineral Resources Research, Chinese Academy of Sciences, Beijing 100029, China |
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Abstract: | Along the Proterozoic stratigraphic sections of Jixian, Tianjin, the δ13C values of carbonates are mostly negative in the Changchengian (Changcheng System), varying approximately within a range
of (0±1 )‰ in the Jixianian (Jixian System), and have commonly positive values of (2±2)‰ in the Qingbaikouan (Qingbaikou System).
From Chuanlinggou Formation to Dahongyu Formation, i.e. from ca. 1700 Ma to 1600 Ma, the δ13C values of carbonates increase from about -3‰ to 0‰, but oscillate with large excursion in Dahongyu Formation. Two large
excursions occur in the Jixianian, one in Yangzhuang Formation and the other in the third submember of Wumishan Formation
overlaying. These integrated and continuous records of carbon isotope reflect secular variations of δ13C value in ancient
seawater from ca. 1700 Ma to ca. 800 Ma. The increase and subsequent oscillation of seawater δ13C value occurring from the ages of ca. 1700 to ca. 1600 Ma and <1300 Ma may signify two correlative global tectonic events. |
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Keywords: | Proterozoic Jixian carbon isotope chemostratigraphy secular variation global tectonic event |
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