Discovery and geological implication of rodingites derived from eclogites of ophiolites at Changawuzi, western Tianshan, China

摘要

We here report the first case of rodingites that were formed at the expense of eclogite enclosed in the ultramafic rocks of Changawuzi ophiolites. The rodingites contain a mineral assemblage of grossular, diopside, prehnite, chlorite, and relict omphacite and Fe-Mg-Al garnets. The presented data indicate that the formation of the rodingites resulted from a phase of secondary serpentinization during exhumation of the subdueted oceanic plate. The rodingitization started at 370-410 deg C / 6.5-8.5 kbar, while pervasive rodingitization took place under the condition of 200-350 deg C/4-6 kbar. The established PT path shows a retrograde track from eclogites to rodingites. We conclude that the process of rodingitization could also take place under subduction conditions in addition to its more common occurrence under ocean-floor metamorphic conditions.