U-Pb ID-TIMS AGE OF RUTILE FROM THE NORTH MUYA BLOCK ECLOGITES (NORTHEASTERN TRANSBAIKALIA) AS A TRACER OF DURATION FOR OF THE CONTINENTAL LITHOSPHERE EXHUMATION

Abstract

Being an abundant mineral phase of high-grade rocks, rutile is used as a tracer of lithospheric evolution for deep zones of orogenic belts. This study presents the new ID-TIMS U–Pb geochronological, mineralogical and geochemical data for rutile from the North Muya block (Baikal-Muya Foldbelt) eclogites in order to examine the applicability of its age estimates relative to the exhumation process of high-grade rocks. The assemblage of mineral inclusions in rutile (mainly titanite, epidote and amphibole) indicate rutile growth through titanite breakdown reactions during prograde metamorphism epidote-amphibolite or amphibolite-facies rocks. The range of Zr contents and estimated Zr-in-rutile crystallization temperatures correspond to conditions from prograde (619–638°С at 1.5 GPa) till peak ones (659–684°С for 2.5 GPa). The U–Pb age estimate (604 Ma) is notably younger than that of peak eclogitic metamorphism (630 Ma), and highlight the protracted cooling history of eclogite-bearing complex during its evolution below closure temperature of the U–Pb isotope system (~500–525°С) during tectonic unroofing or erosion of continental complexes.