Significance of Mineral Chemistry of Syenites and Associated Rocks of Elagiri Complex, Southern Granulite Terrane of the Indian Shield

Abstract

The Elagiri complex (12°31' N: 78°35' E) represents one of the important silica -oversaturated syenite plutons of the Southern Granulite Terrane of the Indian shield. This article for the first time reports the mineral chemistry of the Elagiri complex and brings out important petrogenetic significance. The litho-members of Elagiri complex are intrusive into high grade country rocks viz. granite gneiss, amphibolite and pyroxene granulite. The country rocks are foliated bearing evidences of multiple folding and deformation. On the other hand, the constituent litho members of the Elagiri complex (syenites, gabbro and later intrusives marked by lamprophyre and carbonatite) show preservation of igneous layering in terms of discernible parallelism of the constituent minerals. The Elagiri complex shows presence of sharp contacts among litho members and marked absence of chilled facies peripheral to the margin. Electron microprobe data have been critically used to systematize the constituent mineral-phases of the different lithomembers of the complex. Geothermobarometric data indicate a temperature of equilibration in the range of ~700° to 500°C at ~2.0 to 5.2 kb which corresponds to shallow level (cf. 18.2 km) equilibration-depth of the complex. Field observations and mineral chemistry data suggest that liquid immiscibility plays an important role during the evolution of the Elagiri complex.

Multivariate statistical analysis of heavy metal concentration in soils of Yelagiri Hills, Tamilnadu, India – Spectroscopical approach

“…The country rocks are foliated bearing evidences of multiple folding and deformation. On the other hand, the constituent lithe members of the Yelagiri complex (senates, gabbro and later intrusive marked by lamprophyre and carbonate) show preservation of igneous layering in terms of discernible parallelism of the constituent minerals [21]. The Seasonal variations in the atmospheric temperature of Yelagiri Hills are not extreme and the place experiences pleasant climate throughout the year.…”

Geochemistry and petrogenesis of syenites and associated rocks of the Elagiri complex, Southern Granulite Terrane, India

“…Alkaline complexes in other parts of the world also possess such signatures (McSween et al, 1984;Kramm and Kogarko, 1994). The petrographic characters for different syenite members show broad overlap and show a smooth variation attesting magmatic differentiation from a common parent magma (see Mukhopadhyay et al, 2011). The major and trace element variations also show smooth patterns favoring differentiation from a common magma.…”

“…The Elagiri complex is exposed in the shape of a mushroom in plan (Mukhopadhyay et al, 2011). The lithologic units of the complex show an intrusive relationship with the surrounding high grade metamorphic rocks consisting of granite gneisses, amphibolites and pyroxene granulites.…”

“…The gabbro bodies including hornblende gabbro occur as lenses. The later intrusives are marked by lamprophyre (minette and monchiquite varities) and carbonatite dykes which intrude both syenites and country rocks (Mukhopadhyay et al, 2011).…”

“…The lamprophyre dykes intrude into the porphyritic syenite and also in the granite gneiss country rocks (Mukhopadhyay et al, 2011). The lamprophyres belong to two subtypes: biotite-bearing lamprophyre and green pyroxene-bearing lamprophyre.…”