New Techniques Applied to the U-Pb Method at the Centre for Geochronological Research of the University of S o Paulo: Chemical Digestions, TIMS Mass Spectrometry and Examples of Integrated Application of SHRIMP

The present work describes new techniques of U-Pb ID-TIMS developed at the CPGeo-IGc/USP. Techniques of partial and total chemical digestions, U and Pb concentration using anion exchange in a micro column, and the utilization of a 205Pb spike are discussed. Main geochronological equations used are also discussed. Examples of the application of U-Pb data, obtained by leaching technique using a microwave oven in zircon with isotopic inheritances in the core and border, are presented. The genesis of zircon based on the initial 176Hf/177Hf ratio is discussed. Finally complete listings of the mathematicalformulations used in the PBDAT software are given in the appendix.