西南印度洋洋中脊49.6°E高H_(2)O/Ce比值玄武岩  

The High H_(2)O/Ce Ratio Basalts from Southwest Indian Ridge 49.6°E

作　　者：王青青 刘佳[3] 陶春辉 李伟 梁锦 柳云龙 WANG Qing-qing;LIU Jia;TAO Chun-hui;LI Wei;LIANG Jin;LIU Yun-long(School of Geography and Ocean Science,Nanjing University,Nanjing 210023,China;Second Institute of Oceanography,MNR,Hangzhou 310012,China;School of Earth Science,Zhejiang University,Hangzhou 310027,China)

机构地区：[1]南京大学地理与海洋科学学院,江苏南京210023 [2]自然资源部第二海洋研究所,浙江杭州310012 [3]浙江大学地球科学学院,浙江杭州310027

出　　处：《矿物学报》2023年第5期573-580,共8页Acta Mineralogica Sinica

基　　金：国家重点研发计划课题(编号:2018YFC0309902)。

摘　　要：本文报道来自西南印度洋超慢速洋脊49.6°E洋脊处的新鲜洋中脊玄武岩(MORB)玻璃样品的主微量元素和w(H_(2)O)。样品w(H_(2)O)范围为0.31%~0.40%,高于其他洋脊一般的N-MORB样品。样品H_(2)O/Ce的比值范围为543~613,显著高于大西洋、太平洋MORB和前人发表的邻近洋脊样品数据。根据熔融模型计算,地幔源区w(H_(2)O)高于450×10^(-6),显著高于前人估计的亏损地幔源区(DMM)w(H_(2)O)范围50×10^(-6)~200×10^(-6)。流体活动性元素和Nb之间的线性正相关关系,以及w(H_(2)O)与不相容元素之间的相关关系表明,相对高的w(H_(2)O)和H_(2)O/Ce比值并非遭受混染了的蚀变产物造成的。相反,它们反映了源区地幔的特殊性,很有可能来自于源区中小尺度的古老地幔楔熔融残余。The water contents,and the concentration of major and trace element of the fresh quench basaltic glasses from Southwest Indian Ridge(SWIR)49.6°E are quantitatively analyzed.The results show that the H_(2)O contents of these glasses are in the range of 0.31%-0.40%,which are considerably higher than that of many N-MORB samples from other ridges.In addition,the H_(2)O/Ce ratio was calculated to be 543-613,significantly higher than of Atlantic and Pacific ridge MORB.The water contents in the mantle sources calculated by batch or fractional melting models are higher than 450×10^(-6),which is significantly higher than the normal MORB source(50×10^(-6)-200×10^(-6)).Significant positive correlations between fluid-active elements and Nb,as well as the good linear correlations between water content and incompatible elements,indicate that the relatively high water content and H_(2)O/Ce ratio are not caused by mixed alteration products.On the contrary,they reflect the uniqueness of the mantle in the source region,and may be due to the melting remnants of the mesoscale ancient mantle wedge in the source region.

关 键 词：淬火玻璃 FTIR MORB 西南印度洋脊 含水量 

分 类 号：P581[天文地球—岩石学] P717[天文地球—地质学]