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Experimental Investigation on the Transport of Sulfide Driven by Melt-rock Reaction in Partially Molten Peridotite
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  • Zhenjiang Wang,
  • Zhuosen Yao,
  • Zhenmin Jin,
  • Yannan Wang
Zhenjiang Wang
Key Laboratory of Resource Exploration Research of Hebei Province, and School of Earth Science and Engineering, Hebei University of Engineering
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Zhuosen Yao
Department of Earth Sciences, Carleton University

Corresponding Author:yaozhuosen@163.com

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Zhenmin Jin
China University of Geosciences (Wuhan)
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Yannan Wang
Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences
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Extraction of sulfide liquid from partially molten mantle is vital to elucidate the cycling of metal and sulfur elements between different geochemical circles but has not been investigated systematically. Using the reaction couple method of laboratory experiments and theoretical calculations, this study documents systematical variations in lithologies and compositions of silicate minerals and melts, which are approximately consistent with the results of thermodynamically-constrained model. During melt-peridotite reaction, dissolution of olivine and precipitation of new orthopyroxene produce an orthopyroxene-rich layer between melt source and peridotite. With increasing reaction degree, more melt is infiltrated into and reacts with upper peridotite, which potentially enhances the concomitant upward transport of dense sulfide droplets. Theoretical analyses suggest an energetical focused melt flow with a high velocity (~ 170.9 μm/h) around sulfide droplet through pore throat. In this energic melt flow, we, for the first time, observed the mechanical coalescence of sulfide droplets, and produced drag force was likely driving upward entrainment of fine μm-scale sulfide. For coarse sulfide droplets whose sizes are larger than the pore throat in partially molten peridotite, their entrainment through narrow constrictions in crystal framework seems to be physically possible only when high-degree melt-peridotite reaction drives high porosity of peridotite and some channelized melt flows with extremely high velocity. Hence, melt-rock reaction could drive and enhance upward entrainment of μm- to mm-scale sulfide in the partially molten mantle, potentially contributing to the fertilization of the sub-continental lithospheric mantle and the endowment of metal-bearing sulfide for the formation of magmatic sulfide deposits.
31 Mar 2023Submitted to ESS Open Archive
04 Apr 2023Published in ESS Open Archive