Geochemical Characteristics and Chemical Electron Microprobe U-Pb-Th Dating of Pitchblende Mineralization from Gabal Gattar Younger Granite, North Eastern Desert, Egypt

摘要

Pitchblende mineralization was studied in the younger granite samples collected from Gabal Gattar, north Eastern Desert, Egypt using electron scanning microscope (ESM) and electron probe microanalyses (EPMA). This study revealed that this pitchblende contains significant Zr content reaching up to (66.80% ZrO2), which suggests that volcanic rocks were probably the source of such a deposit. High level emplaced high-K Calc-alkaline plutons as Qattar granite may have been associated with their volcanic equivalent emplaced in the surrounding area or now eroded. Lead content of the pitchblende mineralization is high and with moderate volcanics (up to 7.71% PbO). In contrast, it is low in ThO2, Y2O3 and REE2O3. High Zr and Pb content associated with pitchblende mineralization from Gattar granite indicates that the source of this mineralization derived from volcanic magma not from granitic magma. According to the calculation of U-Pb chemical ages using U, Th and Pb content measured with an electron microprobe for this pitchblende yielded ages within 543 - 657 Ma indicating a Pan-African age for this mineralization. This is the first time that a Pan-African age (543 to 657 Ma) is recorded for a U-mineralization in Gabal Gattar younger granite in the north Eastern Desert, Egypt.