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Spectroscopic Studies on Fluorites from Li-F and Alkaline Granitic Systems in Central Kazakhstan. In: Granite-Related Ore Deposits of Central Kazakhstan and Adjacent Areas.

Abstract:

Fluorite is commonly presented in all types of granite-related rare-metal deposits. Because of its chemical and structural properties, this mineral is an excellent probe for the detection of the evolution in related ore-forming fluid systems. Tungsten(-molybdenum-beryllium) and Nb-Zr-REE-bearing deposits are found in the Central Kazakhstan region in connection with Li-F granitic and alkaline granitic intrusions, respectively. A sequence of differently coloured fluorites (brown to rose - green - violet) may be established in the Karaoba (W), Akchatau (W) and Kent (Nb-Zr-REE) deposits. The investigation of chemical properties and real structure of these fluorites by NAA, ICP-MS, optical absorption spectroscopy, photoluminescence, thermoluminescence (glow curves) and EPR shows typical properties for fluorite from rare-metal deposits. The evolution of the colouration is a result of changes in the trace element content as well as in the defect structure of the mineral. These changes reflect changes in the character of the fluids during fluorite crystallization. The different colours are of radiogenic origin. On the background of the decreasing influence of the Th-radiation on the colour the intensity of thermoluminescence also decreases. The highest signal intensities of defect centres of the REE were detected for the intermediate green fluorite variety. Centres of bivalent manganese are more typical for early brown to rose fluorite. Late violet fluorite is characterized by the presence of M-centres and very low TL-intensities with high-temperature glow-curve peaks. From the form of the TL glow curves, it is possible to distinguish violet fluorite from veins from dark violet metasomatic fluorite.

Authors:

Morozov, Mikhail and Trinkler, Michael and Plötze, Michael and Kempe, Ulf

Index Terms:

FLUORITE; EPR; Luminescence; Clay; ClayGroup

Further Information:

Date published: 1996