Titanite U-Pb dating by LA-Quadrupole-ICP-MS: analytical procedures and applications to Rhyacian metamorphic rocks of the Southeastern Guiana Shield.

Abstract

We present a comprehensive set of LA-Q-ICP-MS U-Pb ages on titanite standards (Tory Hill, Khan, Mud Tank, and CKHB titanites) together with samples from the Southeastern Guiana Shield, as a geological application of the method implemented at the Pará-Iso Laboratory. The results showed good reproducibility, accuracy, and precision for Mesoproterozoic to Mesozoic titanite standards, with uncertainties below 2%. The analytical protocol was validated through interlaboratory calibration with SHRIMP IIe dating, yielding ages consistent with LA-Q-ICP-MS results. Khan titanite were the most suitable primary standard due to its low common Pb content, high analytical signal, and homogeneous U-Pb radiogenic ratios. Distinct ages were observed for Tory Hill titanite and for a selected sample based on different common Pb-correction approaches, with the 204Pb correction being less effective than the 207Pb method. New titanite U-Pb ages identified a late orogenic metamorphic event around 2.05 Ga recorded in an orthogneiss of the Neoarchean Guianense Complex and a collisional metamorphic event around 2.11-2.10 Ga in two samples located at the frontier between the French Guiana and Amapá state. Both linked to the Transamazonian geodynamic evolution of the Southeastern Guiana Shield during the late Rhyacian.