Pyroxene-Sövite in Amba Dongar Carbonatite-Alkalic Complex, Gujarat
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Carbonatite Research Centre, Amba Dongar, Gujarat
Shrinivas G. Viladkar
DOI:
https://doi.org/10.1007/s12594-017-0756-yAbstract
The present paper for the first times gives details of pyroxenesövites of Amba Dongar and discusses significance of these pyroxenes in evolution of carbonatite magma in Amba Dongar. Calciocarbonatite (sövite) forms the major mass of carbonatite in Amba Dongar complex. It shows large variation in texture and mineral composition and has complex evolutionary history. Three types of compositional variations are observed in sövite samples, (1) monomineralic sövites are coarse grained with 99% calcite, (2) sövites with abundant apatite, barite, pyrochlore, magnetite and zirconolite and (3) silico-sövite with of clinopyroxene and phlogopite. In the crystallization history of various sövite types, silico-sövite seems to have crystallized as an earlier phase and was later caught up in major sövite mass. Both, phlogopite-sövite and pyroxene-sövite are coarse grained and exhibit hypidiomorphic texture. Phlogopite is strongly zoned with Mg-rich core to Fe-rich rims. Pyroxenes also exhibit zoning with decrease in Ca and Mg and increase in Fe and Na from core to rim. In general composition of clinopyroxene varies from diopsidic to aegirine-augite. Pyroxenesövites show good concentration of Ba, Sr, Nb and LREE. Elevated concentrations of LREE are found in two aegirine-sövites.
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References
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