Discovery of Early Paleozoic eclogite from the East Kunlun, Western China and its tectonic significance

Abstract

Eclogites discovered in the eastern part of the East Kunlun Mountains, Western China, are primarily composed of garnet+omphacite+quartz+rutile. The garnets show end-member components of 48–55% almandine, 1–2% spessartine, 19–29% grossularite and 16–29% pyrope, and the omphacite has a jadeite content of 21–63%. The peak-metamorphic assemblage of eclogites records a P–T condition of >1.6GPa and 590°C–650°C. Zircon U–Pb dating of the inherited magmatic zircons from fine-grained eclogite reveals a Neoproterozoic age of 934Ma, representing the protolith age of the eclogite. Zircons from the coarse-grained eclogite contain inclusions of garnet, omphacite and rutile, and yield a weighted mean age of 428Ma, indicating the metamorphic age of eclogite. The eclogites, together with the Late Cambrian (508Ma) high-pressure granulite to the west, constitute an Early Paleozoic high-pressure metamorphic belt in the East Kunlun.