Mineralogy of Dolomite Carbonatites of Sevathur Complex, Tamil Nadu, India

Maria Rampilova,Elizaveta Zubakova,Anna Doroshkevich,Shrinivas Viladkar

doi:10.3390/min11040355

Abstract

The main mass of the Sevathur carbonatite complex (Tamil Nadu, India) consists of dolomite carbonatite with a small number of ankerite carbonatite dikes. Calcite carbonatite occurs in a very minor amount as thin veins within the dolomite carbonatite. The age (207Pb/204Pb) of the Sevathur carbonatites is 801 ± 11 Ma, they are emplaced within the Precambrian granulite terrains along NE–SW trending fault systems. Minor minerals in dolomite carbonatite are fluorapatite, phlogopite (with a kinoshitalite component), amphibole and magnetite. Pyrochlore (rich in UO2), monazite-Ce, and barite are accessory minerals. Dolomite carbonatite at the Sevathur complex contains norsethite, calcioburbankite, and benstonite as inclusions in primary calcite and are interpreted as primary minerals. They are indicative of Na, Sr, Mg, Ba, and LREE enrichment in their parental carbonatitic magma. Norsethite, calcioburbankite, and benstonite have not been previously known at Sevathur. The hydrothermal processes at the Sevathur carbonatites lead to alteration of pyrochlore into hydropyrochlore, and Ba-enrichment. Also, it leads to formation of monazite-(Ce) and barite-II.

Highlights

Carbonatites are igneous rocks, which consist of more than 50 vol.% of primary magmatic carbonates and less than 20 wt.% of SiO2 [1]
We present new mineralogical data on the Sevathur Nb-Ba-REE minerals because little information on many of these minerals is available in the literature, and this will help to determine the history of crystallization and subsequent alteration of the Sevathur minerals
We present new data on the mineralogy of dolomite carbonatites of the Sevathur complex

Summary

Introduction

Carbonatites are igneous rocks, which consist of more than 50 vol.% of primary magmatic carbonates and less than 20 wt.% of SiO2 [1]. A wide range of deposits of strategically important mineral materials, such as rare (Nb, Ta, Zr, Li et al.), rare earth (REE+Y) and radioactive elements, as well as the apatite, and fluorite deposits and others, are associated with carbonatite complexes. A great scientific and practical interest in orebearing carbonatite complexes today has been caused by the accumulation of a considerable amount of information about their geological structure and mineral composition. The Sevathur carbonatite complex is the first discovered carbonatite from Tamil Nadu province in 1966 by the State Geology Survey [2] ( referred to as Koratti) and was confirmed by Deans in 1968 (Deans, unpublished report, Overseas Geological Survey, England). Afterward, detailed geological prospecting of the Sevathur carbonatite and adjacent areas was carried out by the United Nations Development Program as part of the Tamil Nadu Mineral Development project. Eight more carbonatite occurrences were reported from this region, all of which are located along the same NE-trending lineament [3], and intrusive into Archean Peninsular gneisses

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