Geochemical constraints on CO2-rich mantle source for the Kocebu Seamount,Magellan Seamount chain in the western Pacific  

作　　者：LIU Yuhao ZHANG Guoliang ZHANG Ji WANG Shuai 

机构地区：[1]Center of Deep Sea Research&Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China [2]Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266000,China [3]University of Chinese Academy of Sciences,Beijing 100049,China [4]Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao 266071,China

出　　处：《Journal of Oceanology and Limnology》2020年第4期1201-1214,共14页海洋湖沼学报（英文）

基　　金：the National Natural Science Foundation of China(Nos.91858206,41876040);the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22050101,XDB42020302);the Taishan Scholars Program of Shandong Province(No.tsqn201909157),Senior User Project of R/V Kexue(No.KEXUE2018G09);the Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology(No.MGQNLMTD201806)。

摘　　要：The alkaline oceanic island basalts(OIBs)with under-saturated SiO2 and high contents of CaO and alkaline are usually attributed to mantle sources different from typical tholeiitic OIBs.Based on the results of high pressure and temperature experiment study,the genesis of silica under-saturated alkaline basaltic melts could be explained by the role of CO2,thus,the genetic relationship of alkaline basalts with CO2 has become a topic of relevance because it is closely related to the deep carbon cycle.The Magellan Seamount chain in the West Pacific Seamount Province has wide distribution of alkali basalts.For the first time,we collected alkaline basalt samples from the Kocebu Seamount of the Magellan Seamount chain and found that magmatic apatites widely occur in the less evolved volcanic rock samples,and the high contents of phosphorus should be a feature of the alkaline OIBs of the Magellan Seamounts.Compared with typical OIBs,these alkaline volcanic rocks have higher CaO and P2O5,lower SiO2 content,negative anomaly of high field strength elements(HFSEs),more distinctly negative anomaly of potassium(K)and the ubiquity of titanaugite,indicating a CO2-rich mantle source.Based on the relatively high K2O and TiO2 contents and La/Yb ratio and low MgO content of these alkaline rocks,we suggest that the volcanic rocks of the Magellan Seamounts are originated from carbonated eclogites derived possibly from ancient subducted altered oceanic crust.

关 键 词：alkaline oceanic island basalts(OIBs) CARBONATITE geochemistry mantle source Magellan Seamounts 

分 类 号：P59[天文地球—地球化学] P736[天文地球—地质学]