Significance of REE study for origin of sparry magnesite in Orhaneli Region, Turkey

Pattern of REE distribution in various types of magnesite ore occuring within the Late Cretaceous ultramafics in Orhaneli Region (Western Anatolia) were studied to interpret their genetic significance. The samples were classified into three different groups viz. massive, lentiform and pignolite or stockwork. Individual groups exhibit distinctly different REE distribution pattern with variable Eu, Ce and Yb anomalies. Three types of REE distribution patterns are recognizable with the following characteristics: (1) high LREE/HREE ratios without having Ce and Eu anomalies, (2) similar LREE and HREE abundance with uncertain positive and negative Eu and Ce anomalies, and (3) low REE abundance with markedly positive Eu, negative Ce and slightly negative Yb anomalies. It is postulated that the redox conditions in the primary mineral formation system was subjected to change and as a result, subsequent mobilization followed by recrystallization took place in the formation of primary magnesite minerals. Although a low temperature environment is indicated for magnesite formation, it is possible that REE-poor solutions derived from the fluid-rock interaction had caused mobilization and later recrystallization of magnesite ore.