U–Pb ID-TIMS Age of Rutile from the North Muya Block Eclogites (Northeastern Transbaikal Area) as a Tracer of the Duration for Exhumation of the Continental Lithosphere

Rutile, an abundant mineral phase of high-grade rocks, is used as a tracer of lithospheric evolution for deep zones of orogenic belts. This study presents new ID-TIMS U–Pb geochronological, mineralogical, and geochemical data for rutile from eclogites of the North Muya block (Baikal–Muya fold belt) 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) up to peak ones (659–684°С for 2.5 GPa). The U–Pb age estimate (605 Ma) is notably younger than that of peak eclogitic metamorphism (630 Ma) and highlight the protracted cooling history of the eclogite-bearing complex during its evolution below the closure temperature of the U–Pb isotope system in rutile (~500–525°С) during tectonic denudation or erosion of continental complexes.