Review Paper:
Geochemical characters
of Leptynite from Melur, Madurai District, Tamil Nadu, South India
Vijayaragavan K., Thirunavukkarasu A., Rakkiannan S. and Sakthivel C.
Res. J. Chem. Environ.; Vol. 29(10); 128-141;
doi: https://doi.org/10.25303/2910rjce1280141; (2025)
Abstract
Leptynite occur with minor bands of basic granulites, charnockites, calcsilicate
rocks, quartzites and khondalites in the Melur area in the Southern granulite terrane
(SGT), India. Interbedded grey and cream leptynite types are distinguished based
on field relations and geochemistry. They are paragneisses (khondalites) comprising
to quartz-felspar-sillimanite gneiss, quartz-felspar-garnet-sillimanite gneiss and
their variants: charnockite series consisting of pyroxene granulites (basic) and
charnockites (acidic), granites, pegmatites and aplites and dolerites. Charnockites,
granites and dolerites are successfully emplaced into the basement rocks' interbanded
paragneiss and pyroxene granulites. Leptynite is noticed at the contact of paragenesis
and charnockite.
Based on whole-rock geochemistry, it is evident that both charnockite patches and
host leptynites are isochemical. The adamellite composition, per-aluminous nature
with positive Europium anomaly of host leptynite and charnockite patches, suggest
their co-genetic relation. Higher values of (La/Yb)N and (Gd/Lu)N of leptynites
indicate the highly fractionated HREE pattern of leptynites. The total REE, LREE/HREE
and Eu-Eu∗ data indicate their derivation from the post-Archaean granodioritic upper
crust comprising of large proportions of impure greywackes with K-rich granitic
components.
