The ages of U-Pb and Sm-Nd for eclogite from the western segment of Altyn Tagh tectonic belt——Evidence for existence of Caledonian orogenic root

The ages of U-Pb and Sm-Nd for eclogite from the western segment of Altyn Tagh tectonic belt——Evidence for existence of Caledonian orogenic root

The eclogites of Altyn Tagh tectonic belt occur as lens within gneisses characterized by amphibolite-facies mineral parageneses. The well-preserved eclogite is selected for Sm-Nd and U-Pb isotopic dating. The Sm-Nd isotopic data yield a whole rock-garnet-omphacite isochron of (500 ± 10) Ma. The U-Pb isotopic measurements of zircons show that the four grain populations are nearly concordant and well plotted on concordia curves, giving a weighted mean age (503.9 ± 5.3) Ma. Two kinds of methods obtain a similar age which reveals the peak meta-morphic age of eclogites, and reflect the existence of orogenic root related to Caledonian sub-duction and continent-continent collision.