Cenozoic potassic volcanic rocks from the Keluo and Wudalianchi volcanic districts,northeast China:origin from the new sub-continental lithospheric mantle(SCLM)metasomatized by potassium-rich fluids from delaminated lower crust  

作　　者：Fanchao MENG Yulu TIAN Yaoqi ZHOU Jiaqi LIU Gengchao ZUO Qing DU 

机构地区：[1]School of Geosciences,China University of Petroleum(East China),Qingdao 266580,China [2]Pilot National Laboratory for Marine Science and Technology(Qingdao),Qingdao 266061,China [3]Shandong Provincial Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China),Qingdao 266580,China [4]Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China

出　　处：《Frontiers of Earth Science》2022年第4期989-1004,共16页地球科学前沿（英文版）

基　　金：supported by the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(No.2021QNLM020001-1);Natural Science Foundation of Shandong Province(No.ZR2021MD083);National Natural Science Foundation of China(Grant Nos.41302102 and 41772190);Graduate Innovation Project of China University of Petroleum(East China)(No.YCX2021020).

摘　　要：A series of Cenozoic potassium-rich volcanic rocks developed in the Xiaoguli-Keluo-Wudalianchi-Erkeshan districts,northeast China.The source region and potassium-rich mechanism of the potassic rocks remain highly disputed.In this paper,the major elements,trace elements,and Sr-Nd-Pb isotopes of the volcanic rocks in Keluo(KL)and Wudalianchi(WDLC)volcanic districts were analyzed systematically.The results show that the volcanic rocks are characterized by high K2O(4.36wt.%-6.13wt.%),remarkable enrichment in LREEs and LILEs,as well as the strong fractionation of HREEs.The isotopic characteristics with high 87Sr/86Sr(0.704990-0.705272),low 143Nd/144Nd(0.512306-0.512417),low 206Pb/204Pb(16.546-17.135)and 207Pb/204Pb(15.002-15.783)of the volcanic rocks suggest the involvement of EM-I-type mantle.On the basis of the geochemical characteristics,the potassium-rich volcanic magma originated from the new SCLM forming after delamination of the ancient SCLM,with metasomatism of the potassium-rich fluids released from the ancient lower crust during the Late Mesozoic.The proposed genetic model assumes the source which represented by a phlogopite-bearing garnet peridotite(with modal garnet in the range of 2%-10%)experienced very low degrees(i.e.,~0.5)of partial melting.During Cenozoic,the lithosphere in northeast China was affected by the extension and decompression of continental rift,and the metasomatized SCLM underwent low degree partial melting,resulting in the formation of potassium-rich primitive basaltic magma.

关 键 词：northeast China Keluo-Wudalianchi volcanic districts Cenozoic potassic volcanic rocks petrogenesis sub-continental lithospheric mantle 

分 类 号：P618.13[天文地球—矿床学]