Discovery of moissanite in retrogressive eclogite from the Pre-pilot Hole of the Chinese Continental Scientific Drilling Project (CCSD-PP2) and its geological implication Journal Article uri icon

DCO ID 11121/9553-1499-7099-6041-CC

in language

  • eng

year of publication

  • 2007

abstract

  • The thin-sections for retrogressive eclogite are observed by Microscope and analyzed by Raman spectrum from the Pre-pilot Hole of the Chinese Continental Scientific Drilling Project (CCSD-PP2). A series of the inclusions within garnet are recognized including moissanit, omphacite, apatite, zircon, rutile, coesite, quartz, magnesite, and magnetite, among which the moissanit is firstly found in retrogressive eclogite, and is of important implication to temperature and pressure. The Raman shifts of moissanites are typical and stable, the main shifts, secondary ones, and another two weaker ones are 786 similar to 789 cm(-1), 966 similar to 977cm(-1), and 769 similar to 781 cm(-1) and 915 similar to 918 cm(-1), respectively. The compositional zoning and mineral assemblages in garnets show that the retrogressive eclogite in CCSD-PP2 were from retrogressive metamorphism of rutile eclogite which formed in ultrahigh pressure and temperature, and the moissanite formed at the peak stage metamormism. According to the formed conditions of moissanite, that is extremely low redox state and T > 1000 degrees C, P > 6.0GPa. and the temperature and pressure condition for eclogite calculated by mineralogical thermometer and barometer, speculate that a few eclogite in the Sulu ultrahigh pressure metamorphic belt was the result of subduction of Yangzi plate and rapid exhumation after captured moissanite, and the depth of subduction is deeper than 200 km, which equivalents to the low part of the upper mantle.

volume

  • 23