地理情報学と地球統計学: 概要

Geology, Spectrometric Prospecting and Rare Earth Elements Geochemistry of the Fluorite Mineralization at Some Localities Eastern Desert, Egypt

Gehad M. Saleh*, Mohamed Abd El Monsef, and Bahaa M. Emad

The present work deals with the geology, radioactivity and geochemical investigations of rare earth elements associated with fluorite veins. The latter is intruded in granites with as a peculiar distribution of economically important mineralization and has a variety of colours (mostly green and violet) and occurs as banded with distinct alternation bands of silica and carbonate and also as veins. Field work spectroscopy measurements over these fluorite veins reveal that some veins are radiometrically anomalous. Geochemically, the averages of total rare earth elements (ΣREE) of fluorites are 178.44 ppm for G. Um Rekhta area, 135.28 ppm for G. Anwayib area, 184.17 ppm for G. Eir Arib area, 235.15 ppm for G. Homret Mikpid area and 179.79 ppm for G. Egat area. The LREE concentrations are dominantly higher than HREE concentrations and REE normalized patterns indicate decreasing abundances with increasing atomic number. All fluorites in the studied areas have strong positive Y anomalies are between 1.51 and 4.10 (with mean of 2.60), negative Eu anomalies are between 0.09 to 0.78 (with mean of 0.38) and slightly positive Ce anomalies are between 0.54 and 1.57 (with mean of 1.00). The Y/Ho values range from 36 to 118 with av. 77.18. The Tb/Ca and Tb/La ratios of the studied fluorites are intermediate to high and these ratios also indicate a formation of fluorites from fractionated ore-bearing fluids at an early stage of mineralization, mainly a hydrothermal stage. The hydrothermal fluids which formed the fluorites were probably derived from the granitic melt. Consequently, the field geology and REE geochemistry show that the composition of mineralizing fluids, the location of ore formations, the mineralizing mechanisms and the prevailing physicochemical conditions of the depositional environments for the fluorite veins of the studied areas were different. The high contents of radioactivity and rare earth elements mineralization in some fluorite veins make them a target to enlarge the potentiality of the highly mineralized localities