Chemistry and Origin of Enigmatic Monazite and Chevkinite/Perrierite in the Egyptian Black Beach Sand

Abstract

The content of monazite in the Egyptian black beach sand and coastal sand dunes is normally equal to or below 0.01 wt.%. The obtained high grade monazite concentrate includes three minor monazite groups in addition to major canary and lemon yellow coloured monazite: (i) the colourless to pinkish white coloured monazite; (ii) the opaque light to dark resinous, reddish brown and dark brown coloured monazite; and (iii) opaque yellowish red to brownish red coloured monazite grains group. These groups represent 3%, 4% and 2%, respectively, in the high grade monazite concentrate. A negligible amount of euhedral to subhedral black to brownish black chevkinite/perrierite mineral crystals was detected in the obtained monazite concentrate. The presence of these minor mineral groups affects the chemical composition of the obtained high grade monazite concentrate.The Ce 2O3 is the main REE in the studied monazite. In the colourless-pinkish monazite grains, the analyzed REE are the following, in order of abundance; Ce > La > Nd > Pr > Sm > Gd > Dy. UO2 ranges between 0.11 and 1.74 wt.%. The contents of Eu2O3 is under the limit of detection while ThO2 ranges between 3.99 and 8.58 wt.% with an average value of 5.57 wt.%. These grains are most probably igneous monazite from a highly differentiated granite.The resinous, brown monazite grains have lower Ce 2O3 content (24.63 wt.%) and much lower La2O3 content (6.00 wt.%) but greater content of Eu2O3 (0.41 wt.%) than those of the colourless-pinkish monazite. These monazites have the lowest contents of Th, U and Ca among the three groups. The resinous, brown monazites are most probably formed by metamorphism or alteration leading to leaching or replacement of pre-existing minerals.The red monazite group has a lower average Ce 2O3 content (25.28 wt.%) than the colourless-pinkish variety (28.02 wt.%) but slightly greater than that of the resinous, brown ones. The red monazite group has the highest ThO 2 and UO2 contents; 5.84 wt.% and 1.24 wt.%, respectively. It has the lowest monazite component mole fraction (0.75). The red monazite seems to have been formed by hydrothermal alteration of pre-existing monazite and other mineral species bearing for Y, REE, Ca, Th and U.The , are obvious in the studied colourless-pink monazite.

Physical and Chemical Beneficiation of the Egyptian Beach Monazite

“…Some monazite grains have elongate or tabular shapes. Monazite grains of the minor groups are brown, reddish brown, reddish to brownish yellow, and dark red in color (Moustafa, 2010;Fig. 6b).…”

Analysis and Interpretation of the Field and Laboratory Geophysical Measurements of Black-Sand Beach Deposits, East Rosetta, Egypt

“…Placer sand deposits in the northern Nile Delta, especially in Koam Mashaal area, have received the attention of several researchers since the early years of the 20th century. The most recent researches that carried out studies on these placer sands include Hedrick and Waked [2], Elhadary [3], AbuDiab [4], El-Sadek and Elkhateeb [5], Bakheit [6], Ammar et al [1], and Moustafa [7]. The study area is a part of the semiarid coastal region which is characterized by its wide plain covered by placer sand deposits.…”