WANG Qing-qing1, 2*, LIU Jia 3, TAO Chun-hui2, LI Wei2, LIANG Jin2, LIU Yun-long2

(1. School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China; 

2. Second Institute of Oceanography, MNR, Hangzhou 310012, China; 

3. School of Earth Science, Zhejiang University, Hangzhou 310027, China)

Abstract: The water contents, and concentrations of major and trace elements of the fresh quenched basaltic (MORB) glasses at 49.6°E of the Southwest Indian Ridge (SWIR) have been quantitatively analyzed and reported in this paper. The results show that the H2O contents of these glasses vary from 0.31% to 0.40%, which are considerably higher than those of many N-MORB samples from other ridges. In addition, the H2O/Ce ratios, varying from 543 to 613, are significantly higher than those of MORB samples from the Atlantic and Pacific ocean ridges, and previous published data of MORB samples from adjacent Indian ocean ridges. The water contents in the mantle sources calculated by using the batch or fractional melting models are higher than 450×10-6, which is significantly higher than the previously estimated range of the depleted mantle source (50×10-6－200×10-6). The significant positive correlation between fluid-active elements and Nb and the good linear correlation between water contents and contents of incompatible elements indicate that the relatively high water contents and H2O/Ce ratios are not caused by the contaminated alteration products. On the contrary, they reflect the uniqueness of the mantle source, and could be caused by the melting remnants of the mesoscale ancient mantle wedge in the source region. 

Keywords: Quenched glass; FTIR; MORB; Southwest Indian Ridge; the water content

ACTA MINERALOGICA SINICA Vol. 43, No. 5, 2023, Page 573