Sensitive High Resolution Ion Micro Probe Facility

Fletcher, Birger Rasmussen , Neal Mcnaughton. N2 – SHRIMP Sensitive High-Resolution Ion MicroProbe analytical procedures have been developed to enable dating of the small, early diagenetic xenotime overgrowths that commonly occur on zircons in siliciclastic sedimentary rocks. The method will be particularly useful in Precambrian terranes, where diagenetic xenotime dating could play a role equivalent to biostratigraphic dating in the Phanerozoic.

In contrast, greenschist-facies metasediments of the Archaean Witwatersrand Basin, South Africa, contain both authigenic and alteration xenotime that record a complex history of growth from early diagenesis to the last major thermal event to affect the basin. Overview Fingerprint. Abstract SHRIMP Sensitive High-Resolution Ion MicroProbe analytical procedures have been developed to enable dating of the small, early diagenetic xenotime overgrowths that commonly occur on zircons in siliciclastic sedimentary rocks.

Three dating methods on zircon (Pb-evaporation, ID-TIMS and SHRIMP) were Dating of zircons by the conventional U-Pb method, using TIMS after zircon.

Jelinek I ; Artur C. Bastos-Neto I ; Jayme A. McNaughton III. These ages were obtained by U-Pb isotopic determinations with the sensitive high mass-resolution ion microprobe on igneous zircons from Pedras Grandes Suite in Santa Catarina State. Euhedral zircons remained unaltered close to a fluorite vein deposited at ? C or more. These ages suggest a northern limit for the Pedras Grandes Suite, explaining the spatial relationship between the fluorite veins and the source rock.

Its major significance for crustal building motivated this geochronological investigation. Granitic rocks are exposed in most of the southern part of the shield and their emplacement ages in the entire shield has been bracketed between and Ma by conventional U-Pb zircon dating Basei et al. The granitic rocks in the southernmost part of the batholith have been included either in the Pedras Grandes Suite or in the Tabuleiro Suite, an issue that requires clarification.

The stability of zircon in many geological environments has been long recognized e. The mineral may remain as a closed system for long periods of time, even at high temperatures Cherniak et al. Because the continued investigation of zircon stability led to the systematic decrease in the blocking temperature, our secondary goal in this study is to verify the stability of zircon under conditions of strong but low temperature alteration.