Petrology and geochemistry of cold seep carbonates from the northern Okinawa Trough,East China Sea:implications to early diagenesis  

作　　者：Kehong YANG Zhimin ZHU Yanhui DONG Weiyan ZHANG Fengyou CHU 

机构地区：[1]Key Laboratory of Submarine Geosciences&Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China

出　　处：《Journal of Oceanology and Limnology》2022年第4期1388-1403,共16页海洋湖沼学报（英文）

基　　金：Supported by the National Natural Science Foundation of China(Nos.41476050,41106047)。

摘　　要：Carbonate samples were collected from the northern Okinawa Trough in the East China Sea in 2013.The petrology,mineralogy,carbon and oxygen isotopes,and rare earth elements(REEs)of these samples were analyzed.Aragonite,high-Mg calcite,and dolomite were the main carbonate minerals,the contents of which varied greatly among the carbonate samples.Petrological observations revealed the common occurrence of framboidal pyrites.Theδ^(13)C values of carbonates varied from-53.7‰to-39.3‰(average of-47.3‰based on Vienna Pee Dee Belemnite(V-PDB),n=9),and theδ^(18)O values ranged from 0.6‰to 3.4‰(average of 1.9‰;V-PDB,n=9).The carbon and oxygen isotope characteristics indicated that the carbonates precipitated during the anaerobic oxidation of methane.The carbon source was a mixture of thermogenic methane and biogenic methane,possibly with a greater contribution from the former.The oxygen isotope data showed that gas hydrate dissociation occurred during carbonate precipitation.The Ce anomalies suggested that the carbonates precipitated in an anoxic environment.A slight enrichment of middle REEs(MREEs)could be attributable to the early diagenesis.The structures,minerals,oxygen isotopes,and MREEs all indicated that the carbonates experienced some degree of early diagenesis.Therefore,the infl uence of early diagenesis should be considered when using geological and geochemical proxies to reconstruct original methane seepage environments.

关 键 词：authigenic carbonate carbon and oxygen isotopes rare earth elements(REEs) anaerobic oxidation of methane(AOM) northern Okinawa Trough 

分 类 号：P736.4[天文地球—海洋地质]