The water content and hydrogen isotope composition of continental lithospheric mantle and mantle-derived mafic igneous rocks in eastern China  

作　　者：XU Zheng GONG Bin ZHAO ZiFu 

机构地区：[1]Chinese Academy of Sciences Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences,University of Science and Technology of China

出　　处：《Science China Earth Sciences》2016年第5期910-926,共17页中国科学（地球科学英文版）

基　　金：supported by funds from the Chinese Ministry of Science and Technology (Grant No. 2015CB856100);the National Natural Science Foundation of China (Grant Nos. 41303005 & 41590620);the Fundamental Research Funds for the Central Universities

摘　　要：The water contents of minerals and whole-rock in mantle-derived xenoliths from eastern China exhibit large variations and are generally lower than those from other on- and off-craton lithotectonic units. Nevertheless, the water contents of mineral and whole-rock in Junan peridotite xenoliths, which sourced from the juvenile lithospheric mantle, are generally higher than those elsewhere in eastern China. This suggests that the initial water content of juvenile lithospheric mantle is not low. There is no obvious correlation between the water contents and Mg~# values of minerals in the mantle xenoliths and no occurrence of diffusion profile in pyroxene, suggesting no relationship between the low water content of mantle xenolith and the diffusion loss of water during xenolith ascent with host basaltic magmas. If the subcontinental lithospheric mantle（SCLM） base is heated by the asthenospheric mantle, the diffusion loss of water is expected to occur. On the other hand, extraction of basaltic melts from the SCLM is a more efficient mechanism to reduce the water content of xenoliths. The primary melts of Mesozoic and Cenozoic basalts in eastern China have water contents, as calculated from the water contents of phenocrysts, higher than those of normal mid-ocean ridge basalts（MORB）. The Mesozoic basalts exhibit similar water contents to those of island arc basalts, whereas the Cenozoic basalts exhibit comparable water contents to oceanic island basalts and backarc basin basalts with some of them resembling island arc basalts. These observations suggest the water enrichment in the mantle source of continental basalts due to metasomatism by aqueous fluids and hydrous melts derived from dehydration and melting of deeply subducted crust. Mantle-derived megacrysts, minerals in xenoliths and phenocrysts in basalts from eastern China also exhibit largely variable hydrogen isotope compositions, indicating a large isotopic heterogeneity for the Cenozoic SCLM in eastern China. The water content that is higher than that of 矿物质的水内容并且在从东方中国的导出披风的捕虏体整个岩石展出大变化并且通常是比从另外的 on-craton 和 off-craton lithotectonic 单位的那些低的。不过，水矿物质满足并且在橄榄岩捕虏体，从少年 lithospheric 披风采购原料，通常是的 Junan 整个岩石比在其它地方的那些高在东方中国。这建议少年 lithospheric 披风的起始的水内容不是低的。在水内容和在披风捕虏体和在辉石的散开侧面的没有出现的矿物质的 Mg ^# 值之间没有明显的关联，不上升建议在披风捕虏体的低水内容和在捕虏体期间的水的散开损失之间的关系与招待玄武岩的岩浆。如果 subcontinental lithospheric 披风(SCLM ) 底被 asthenospheric 披风加热，水的散开损失被期望发生。在另一方面，抽取玄武岩从 SCLM 融化是更有效的机制减少捕虏体的水内容。主要在东方中国中生代和新生代暗岩融化正常海中央山脉暗岩(MORB ) 比那些高有水内容，从斑晶的水内容计算了。中生代暗岩岛弧暗岩展出类似的水内容到那些，而新生代暗岩与他们中的一些一起展出可比较的水内容到海洋的岛暗岩和 backarc 盆暗岩类似于岛弧暗岩。这些观察由水的液体由于交代作用在大陆人暗岩的披风来源建议水丰富并且含水融化源于脱水并且融化深深地 subducted 外壳。导出披风的 megacrysts，在捕虏体的矿物质和在从东方中国的暗岩的斑晶也展出大部分可变的氢同位素作文，在东方中国为新生代 SCLM 显示大同位素的异质。比弄空的 MORB 披风和从弄空的 MORB 披风的被背离的氢同位素作文的高的水内容建议新生代大陆人 lithospheric 披风承受了交代作用由含水融化源于在东方中国大陆下面的 subducted 太平洋平板的部分融化。交代作用将在 SCLM 底然后到它的粘性的减少导致水内容的增加。作为后果， SCLM 底将被削弱并且这

关 键 词：Eastern China Continental basalt Lithospheric mantle Water Hydrogen isotope 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学]