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Chemical Indicator of Spinel During Partial Melting and Subsolidus Equilibration of Mantle Peridotite: Experimental Study and Application to Natural Rocks
Author(s) -
Jianping Li,
Kornprobst Jacques,
Vielzeuf Daniel
Publication year - 1995
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.1995.mp8004007.x
Subject(s) - spinel , partial melting , peridotite , geology , mantle (geology) , mineralogy , crystallization , geochemistry , thermodynamics , paleontology , physics
Systematic experimental studies on partial melting and subsolidus equilibration of three reconstituted spinel ‐ peridotites have been carried out at temperatures ranging from 1000 to 1380°C. and pressures of 1.0 and 1.5 GPa: The results show: (1) during partial melting, Mg# [=Mg/(Mg+Fe)]and Cr# [=Cr/ (Cr+Al)] of spinel increase with an increase in degrees of melting; (2) during subsolidus equilibration, with increasing temperatures, Mg# of spinel increases but Cr# of spinel remains almost unchanged in dunite and increases slightly in lherzolite and harzburgite. The negative and quasi ‐ linear Mg# ‐ Cr# correlation of spinel represents an isotherm of total non ‐ equilibrium. The same results have been obtained by means of mathematical modelling. It is also proved by Mg# ‐ Cr# correlation of spinel in natural peridotites. As a result of the spinel subsolidus equilibration, only variation of Cr# of spinel is limited, and then Cr# of spinel can be used to estimate the relative degree of melting undergone by host rocks. The bigger Cr# of spinel is, the higher the degree of melting will be. By contrast, during crystallization magma, Mg# and Cr# of spinel decrease with decreasing temperatures. Likewise, Cr# of spinel in basalts may be used to indicate the feature of Cr 2 O 3 /Al 2 O 3 of magma, and the compositional zoning of spinel may be used to study the evolution of magma (cooling rate and contamination).