Zircon Dating by Raman Spectroscopy: An Experimental Study with Fission Tracks and U-Pb

• Grant number: 25/01804-3
• Support Opportunities: Scholarships in Brazil - Master
• Start date: July 01, 2025
• End date: January 31, 2027
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Carlos Alberto Tello Sáenz
• Grantee: Pedro Brandão Christante
• Host Institution: Faculdade de Ciências e Tecnologia (FCT). Universidade Estadual Paulista (UNESP). Campus de Presidente Prudente. Presidente Prudente , SP, Brazil

Abstract

The understanding of the thermal and structural evolution of rocks over geological time requires reliable and innovative geochronological methods. Among the available techniques, Raman spectroscopy has emerged as a promising tool for dating minerals such as zircon, due to its ability to detect structural alterations induced by accumulated alpha radiation. Despite advancements in its application, gaps remain in the universal calibration of the technique and in the correlation of Raman results with well-established methods such as U-Pb and fission tracks (FT). These challenges limit its adoption as a globally accepted geochronological method. In this context, the present project proposes the integration of multiple dating techniques-Raman, FT, and U-Pb-to explore their compatibility and investigate the reconstruction of the thermal history of specific geological regions. The objectives include validating the relationships between Raman band widths and the accumulated alpha radiation dose, assessing the limitations of the Raman method under controlled experimental conditions, and establishing an integrated protocol for the combined application of the three techniques in zircon samples. The methodology involves the preparation of polished zircon grains, acquisition of Raman spectra in the laboratories of FCT/Unesp, fission track counting after chemical etching, and isotopic analyses by LA-ICP-MS in partner laboratories, with the possibility of a BEPE-FAPESP project in London under the supervision of Prof. Dr. Pieter Vermeesch. The applicant for this project has applied these methods during two years of Scientific Initiation research, funded by FAPESP (Process No. 2022/11589-4), on a sample from the Peixe Alkaline Complex. The use of well-known reference samples, such as FCT and OD-3, and Brazilian samples, such as Peixe, as well as unknown samples, will allow for precise calibrations and cross-validation among the techniques. Thermal annealing experiments may be conducted to evaluate the limitations and, potentially, correct the ages obtained with this novel Raman dating technique. It is expected that the results will provide a foundation for its routine implementation, establishing new reference materials and promoting its unprecedented application in Brazil. As a further advancement, the project will contribute to expanding the available dating tools in materials science and geology, benefiting both academic research and industrial and environmental applications, such as mineral prospecting and the detection of tectonic hydrogen, a potential renewable energy resource. (AU)