Monazite petrochronology constrains the metamorphic evolution of high-grade metamorphic rocks in the Dai Loc shear zone, Central Vietnam
Journal
Vietnam Journal of Earth Sciences
ISSN
2615-9783
Date Issued
2026-03-16
Author(s)
Abstract
The Dai Loc shear zone in central Vietnam contains granulite-facies rocks and is a key area for studying the Early Paleozoic metamorphic evolution of the Indochina Block. An integrated study of in-situ geochronology, trace element geochemistry, and microtextural analysis was conducted to decipher the metamorphic evolution of this highgrade unit. Monazites from the two granulite samples display three distinct chemical domains, whose trace element compositions closely correlate with gamct growth and breakdown. Yttrium-and heavy rare-earth clement (HREE)-rich monazite core domains arc interpreted to have formed with limited gamct growth, recording a discrete growth episode during prograde metamorphism at-435 Ma. Y-and HREF.-poor domains arc linked to significant garnet growth during peak conditions at-420 Ma. The elevated Y+HREE concentrations in the outermost rim domains indicate their formation during garnet breakdown and likely date the retrograde metamorphism to-390 Ma. These U-Pb monazite ages align well with the U-Pb zircon ages from granulites and syn-metamorphic granitoids in the study area, reinforcing the inferred metamorphic timeline. The results of this pctrochronological study highlight the importance of integrating petrology with trace element data from major and accessory phases to link gcochronological data to metamorphic P—T paths.
Subjects
garnet
Indochina block
monazite
Petrochronology
REE partitioning
restite
U-Pb geochronology
Publisher
Publishing House for Science and Technology, Vietnam Academy of Science and Technology (Publications)
Type
journal article