Document Type : Original Article
Authors
1
Geology Department, Faculty of Science, Zagazig University, Sharkia Governorate, Zagazig 44519, Egypt.
2
Geology Department, Faculty of Science, Suez University, Suez Governorate, El Salam City, 43518, Egypt.
3
Geology Department, Faculty of Science, Suez University, El Salam City, P.O. Box 4Geology Department, Faculty of Science, Suez University, Suez Governorate, El Salam City, 43518, Egypt3518, Suez Governorate, Egypt
Abstract
This study focuses on the petrogenesis of A-type granites and associated fluorite in the Qattar area, Northeastern Desert, Egypt. These granitoids show a geochemical signature typical for an A-type granite, characterized by a slightly peraluminous, highly SiO2, alkalis (Na2O+K2O), U, Rb, Zr, contents, and belong to a group of Ferroan granites with low MgO, CaO, and MnO contents and high FeOtot/ FeOtot+MgO ratios. These rocks emplaced during a late-collisional stage at a temperature of~755.3 °C and pressures from 2.33 to 2.95 kbars under oxidizing conditions (log fO2 -14.85 to -14.91). Moreover, a high 10,000×Ga/Al ratio, negative Eu anomaly, and the tetrad pattern of Qattar alkali–feldspar granites backed up their formation by fractional crystallization and fluid-melt interactions during the late stage of magmatic differentiation. Fluorite mineralization is recorded as four fluorite types (sky blue-, light-yellow-, colorless-, and yellow-type) formed by hydrothermal processes. These fluorites show a wide range of rare earth element variations (∑REE from 76.05 to 166.15) and negative Eu anomaly, which indicates crystallization temperatures above 200 °C. Moreover, Gd / Yb ratios are < 1 in sky blue and light-yellow fluorite and >1 in colorless and yellow fluorites, reflecting various conditions of REE leaching.
Keywords
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