Carbon isotopic variations of Proterozoic carbonates in Jixian, Tianjin, China  

作　　者：CHU Xuelei, ZHANG Tonggang, ZHANG Qirui, FENG Lianjun & ZHANG Fusong1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 2. Key Laboratory for Mineral Resources Research, Chinese Academy of Sciences, Beijing 100029, China Correspondence should be addressed to Chu Xuelei (email: [e-mail]) 

出　　处：《Science China Earth Sciences》2004年第2期160-170,共11页中国科学（地球科学英文版）

基　　金：This work was supported by the National Natural Science Foundation of China (Grant Nos. 49973008, 40172015) ; the Chinese Academy of Sciences (Grant No. KZCX2-116).

摘　　要：Along the Proterozoic stratigraphic sections of Jixian, Tianjin, the ??13C 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.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.

关 键 词：Proterozoic  Jixian  CARBON isotope  chemostratigraphy  SECULAR variation  global tectonic event. 

分 类 号：P534[天文地球—古生物学与地层学]