Non-destructive REE determination by high-energy sub-micro XRF in aqueous alteration products and fluid bubbles and veins in the water-rich

The aim of this experiment is to investigate, in a non-destructive manner, the rare-earth element (REE) abundance and obtained concentration trends (e.g. light REE vs high REE, REE anomalies) in intense aqueously altered and fluid-rich regions found inside unique samples of the Winchcombe and Northwest Africa 6693 meteorites. These Ca, P-rich regions of interest correspond to the calcium phosphate minerals apatite and merrillite, which contain trace amounts (1-10 ppm) of REEs like Y and the lanthanide series (La-Lu). Quantified REE values normalised to early Solar System abundances reveal concentration trends which hint at which stage fluids started to mobilise on the water-rich parent bodies of these meteorites.

本实验旨在以无损方式，探究温奇科姆（Winchcombe）陨石与西北非6693（Northwest Africa 6693）陨石的独特样品内部，经强烈水蚀变且富流体区域的稀土元素（rare-earth element，REE）丰度及其浓度变化趋势（如轻稀土与重稀土对比、稀土元素异常）。上述富含钙、磷的目标区域对应钙磷酸盐矿物磷灰石（apatite）与陨磷钙镁矿（merrillite），二者均含有浓度为1~10 ppm的痕量稀土元素，包括钇（Y）与镧系元素（La-Lu）。将量化得到的稀土元素值按早期太阳系丰度归一化后，可揭示其浓度变化趋势，进而推断流体在这些陨石的富水母体天体上启动迁移的阶段。