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Mineral chemistry (U, Th, Zr, REE) in accessory minerals from Wadi Rod Elsayalla granitoids, South Eastern Desert, Egypt
Arabian Journal of Geosciences Pub Date : 2021-09-13 , DOI: 10.1007/s12517-021-08367-7
Ahmed E. Abdel Gawad 1
Affiliation  

Detailed electron probe microanalyses (EPMA) of accessory minerals from Wadi Rod Elsayalla granitoids (SE Desert, Egypt) furnished insights into U, Th, Zr, and REE mineralization. Thorite and uranothorite are the main radioactive minerals, in addition to zircon and monazite. Thorite occurs in syenogranite and quartz syenite rocks with marked enrichment in UO2 up to 6.89 wt% in the former rock type. High Y and Zr elements content in thorite indicates marked replacement of Th by Y and Zr. Uranothorite in syenogranite contains up to 51.68 wt% ThO2, 19.12 wt% SiO2, and 20.62 wt% UO2, in addition to minor amount of Y2O3 up to 1.94 wt%. Zoned zircon shows thorium-rich core, with marked fluctuation in UO2 content, owing to extensive hydrothermal alterations. Total REE content as REE2O3 reaches to about 6 wt% in zircon rims from the syenogranite. Zircon from quartz syenite shows U, Th, and REEs below the detection limit of the electron microprobe. Identified REE prospects in the study area contain (i) REE fluorocarbonates and fluoride (bastnäsite, synchysite, and flocerite), (ii) REE phosphates (monazite-Ce, xenotime, and florencite), and (iii) REE silicates (allanite-Ce and zircon), with a clear predominance of LREE minerals, in which Ce is the main REE. The average REE contents of bastnäsite-Ce, flocerite, synchysite-Ce, and synchysite-Y are 77.28, 74.01, 52.89, and 49.09 wt%, respectively. Xenotime from syenogranite and quartz syenite has average HREE contents (Gd2O3–Lu2O3) of 20.45 and 23.72 wt%, respectively.



中文翻译:

埃及东南沙漠 Wadi Rod Elsayalla 花岗岩中副矿物的矿物化学(U、Th、Zr、REE)

来自 Wadi Rod Elsayalla 花岗岩(埃及东南沙漠)的副矿物的详细电子探针微量分析 (EPMA) 提供了对 U、Th、Zr 和 REE 矿化的深入了解。除了锆石和独居石之外,钍长石和铀钛矿是主要的放射性矿物。钍石出现在正长花岗岩和石英正长岩中,UO 2显着富集,前者的岩石类型高达 6.89 wt%。钍石中的高 Y 和 Zr 元素含量表明 Y 和 Zr 显着取代了 Th。除了少量的 Y 2 O 3外,正长花岗岩中的铀钙石含有高达 51.68 wt% ThO 2、19.12 wt% SiO 2和 20.62 wt% UO 2高达 1.94 重量%。由于广泛的热液蚀变,分带锆石显示富含钍的核心,UO 2含量显着波动。REE 2 O 3总REE含量在来自正长花岗岩的锆石边缘中达到约 6 wt%。来自石英正长岩的锆石显示 U、Th 和 REE 低于电子微探针的检测限。研究区已确定的 REE 远景包含 (i) REE 氟碳酸盐和氟化物(氟碳铈矿、合闪石和萤石),(ii) REE 磷酸盐(独居石-Ce、磷钇矿和萤石)和 (iii) REE 硅酸盐和锆石),LREE 矿物明显占优势,其中 Ce 是主要的 REE。氟碳铈矿-Ce、絮石、合闪石-Ce 和合闪石-Y 的平均稀土含量分别为 77.28、74.01、52.89 和 49.09 wt%。来自正长花岗岩和石英正长岩的磷钇矿的平均 HREE 含量(Gd 2 O 3 –Lu 2 O 3)分别为 20.45 和 23.72 wt%。

更新日期:2021-09-13
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