Crystallographic and isotopic characterization apatite mineral by Fission Track Method: Geochronology of plutonic rocks from the São José do Campestre tectonic domain, Natal, RN, Brazil

Abstract

It is intended to study the etching effects on the crystallographic structure of mineral apatite and its implications for the Fission Track Method (FTM) in grains collected from three plutonic rocks that emerge in the northern part of Borborema Province, Natal, RN, Brazil. For this, we will characterize these apatites through FTM, micro-Raman Spectroscopy, and Scanning Electron Microscopy with Energy dispersive spectroscopy (SEM/EDS). The isotopic characterization will be performed through the FTM, using a Laser Ablation system coupled to a mass spectrometer (LA-ICPMS). Thus, through the study of the physical-chemical phenomena that occur in the natural crystallization of mineral apatite, we will have enough elements to make a new protocol for the crystallographic characterization of apatite prior to the determination of its Fission Tracks age. This project will be fulfilled at the Research Group on Nuclear Track Detectors (DETRAN), Physics Department, UNESP - Presidente Prudente, where there is already a similar protocol, and which is routine in the zircon mineral. The ages of each grain will be obtained by measuring the amount of 238 U directing the laser in the micro area where the density of fission tracks was previously determined. This avoids sample irradiation, which is a very time-consuming process. To put this method into the routine, we will use the standard apatite samples, Durango and FCT (Fish Canyon Tuff) to compare both crystallographic studies and age determination of TF via LA-ICPMS.