The Open Mineralogy Journal

2009, 3 : 17-27
Published online 2009 September 10. DOI: 10.2174/18744567000903010017
Publisher ID: TOMJ-3-17

Elaboration and Characterization of Natural Diatomite in Aktyubinsk/ Kazakhstan

Sobhi Nasir , Thomas Theye and Hans-Joachim Massonne
Department of Earth Sciences, Sultan Qaboos University, P.O.Box 36, 123 Al-Khod, Oman

ABSTRACT

Aeschynite-(Ce) and nioboaeschynite-(Ce) occur as late stage minerals in apatite-dolomite-carbonatite in the eastern Oman Mountains. Micro Raman spectroscopic analysis confirmed that the analysed minerals are aeschynites. Microprobe analyses revealed that the concentrations of REE2O3 are very high, ranging from 33 to 43 wt.%. The chondritenormalized REE patterns are LREE-rich. La/Nd ratios vary in the range ~ 0.4 to 5.8. Several complex substitution mechanisms have been proposed for aeschynite, which are mainly governed by charge balance considerations, with (OH)- + Ti4+ = O2- + (Nb5+, Ta5+) being the most prominent one. In addition, the composition of aeschynite is affected by local compositional parameters.

Keywords:

Aeschynite group, rare earth elements, compositional variation, carbonatite, Oman, Raman spectroscopy.