Crystallographic and isotopic characterization of mineral zircon using the fission trace method, U-Pb and U-Th/He: geochronology of Borborema province, RN, Brazil

Abstract

It is intended to study the effects of chemical etching on the crystal lattice of mineral zircon and the implications on the Fission Trace Method (MTF) in zircon grains collected in the northern part of Borborema Province, Natal, RN, Brazil. For this, we will characterize these minerals through MTF, Micro-Raman Spectroscopy, and Scanning Electron Microscopy with Energy dispersive spectroscopy (SEM/EDS). The Isotopic characterization will be performed through the U-Pb systematic using a Laser Ablation system coupled to a mass spectrometer (ICPMS) and U-Th/He (Alphachron) in zircon grains collected in Borborema Province. Thus, by studying the physical-chemical phenomena that occur in the natural crystallization of each mineral, we will have enough elements to improve the MTF and U-Pb Methodology in zircon, and routinely put the U-Th/He method into our Nuclear Trace Detector Research Group (DETRAN) of DF/FCT, of UNESP of Presidente Prudente. The U-Pb ages will be obtained in the zircon grains in the same areas where their ages will be determined via MTF, that is, we will have simultaneous ages of U-Pb and MTF. On the other hand, in parallel, to start the U-Th/He method, we will choose 4 samples of zircon, in which 4 grains per sample will be dated. Considering the different closing temperatures of each methodology: i) ~ 180 oC in the U-Th/He; ii) ~ 240 oC in the case of MTF; iii) ~ 900 oC in the U/Pb method. This will allow a comprehensive geochronological term study of the northern part of Borborema Province, a region in which there are five oil wells in operation. In order to reach this objective, a selective collection of 16 samples corresponding to plutonic granites of the Brasilian period (~ 600 Ma) was performed, intruded along 800 km in parallel transects from East-Northeast to West-Northwest of this region. (AU)