Quantified, whole section trace element mapping of carbonaceous chondrites by Synchrotron X-ray Fluorescence Microscopy: 1. CV meteorites

摘要

We present the application of a new synchrotron-based technique for rapid mapping of trace element distributions across large areas of the CV3 meteorites Allende and Vigarano. This technique utilizes the Australian Synchrotron X-ray Fluorescence Microscopy (XFM) beam line with its custom designed and built X-ray detector array called Maia. XFM with Maia allows data to be collected using a 2 lm spot size at very low dwell times (~0.1–0.5 ms), resulting in maps of entire thin sections in ~5 h. Maia is an energy dispersive detector system with a large collection solid-angle, which allows full spectral acquisition and high sensitivity. Hence, there is no need to constrain the elements of interest a priori. We collected whole section maps (~2 cm× 1 cm) from 3 thick sections of Allende and a single map (2 cm × 1.5 cm) from a thick section of Vigarano. Our experimental conditions provide data for elements with 20 ≤ Z ≤ 40 (K-shell, Ca through Zr) and the L-emissions of Os, Ir, Pt, Au, and Pb. We illustrate the unique capabilities of this technique by presenting observations across myriad length scales, from the centimeter-scale down to the detection of sub-micrometer particles within these objects. Our initial results show the potential of this technique to help decipher spatial and textural variations in trace element chemistry between CAIs, chondrules, matrix, and other chondritic components. We also illustrate how these datasets can be applied to understanding both nebular and parent-body processes within meteorites.