Coesite inclusions have been discovered in dolomite from carbonate-bearing eclogite in the Dabie UHP terrane. The eclogite boudins are enclosed in calc-silicate rocks that contain quartz aggregates after coesite in the matrix. The carbonate-bearing eclogite is composed of garnet, coesite or quartz, dolomite, magnesite, omphacite, rutile, ±minor phengite, apatite, and zircon, and was formed at ∼760 °C, >28 kbar, and 0.01 < XCO2 <0.1. In addition to coesite inclusions in dolomite, inclusions of coesite and quartz pseudo-morphs after coesite are abundant in garnet. One inclusion of quartz + calcite aggregates after coesite and aragonite (?) was identified in garnet. Radial fractures developed in garnet around the coesite inclusions but are absent in the dolomite. Dolomite contains about 14 mol% ankerite component, whereas magnesite contains about 2 mol% calcite and 23 mol% siderite. This is the first reported occurrence of coexisting magnesite + dolomite + possible aragonite + coesite in a single eclogitic sample and is consistent with experimentally determined stabilities of these phases at mantle conditions. Systematic mineral parageneses of eclogite, marble, and country-rock gneisses support the previous conclusion that supracrustal rocks were subducted to mantle depths of >100 km.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.