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Durham University

Department of Earth Sciences


Publication details for Professor Yaoling Niu

Niu, Yaoling & Batiza, R. (1991). In Situ Densities of Morb Melts and Residual Mantle: Implications for Buoyancy Forces beneath Mid-Ocean Ridges. Journal of Geology 99(5): 767-775.

Author(s) from Durham


Recent theoretical studies of mid-ocean ridge (MOR) accretion have shown that the density differences between silicate melt and solid phases and between fertile and residual mantle may be important controls on the upward flow of upper mantle and separation of melt from the upwelling matrix. Both compositional and thermal buoyancy may play an important role. To assess quantitatively the magnitude of these effects, we have compiled the available data for calculating densities of silicate melts and solid phases as a function of composition, temperature (1000-1500°C), and pressure (1 atm to any pressure where the solid phases of interest remain stable ). We include measured and calculated values of thermal expansion and compressibility for both solids and liquids. Our calculations for mantle material undergoing decompression-induced melting show that density differences between instantaneous melt and residual solids increase toward the surface, implying an increasing melt migration rate with continuing upwelling and melting. However, the density difference is significantly less than the value of commonly assumed in theoretical models. In agreement with previous studies, we also find that residual mantle is less dense than unmelted mantle; however, using realistic pressures for MORB generation, the difference is small.