1 - Cochin University of Science and Technology

abundant proportions. Geochemical data reveal a predominance
of KZO (Z.87 wt %) over NaZO (1.76 wt %) for type while,
the reverse holds true for type 11 with NaZO (2.51 wt %)
predominating over KZO (1.97 wt %). Petrogenetic
characterisation implies a protolith of impure, si! ica-rich
calcareous sediments admixed with phyllosilicates and clays.
Crystalline limestones are medium-to coarse-grained
rocks with typical crystalline texture, often passing over to
elongated granoblastic texture.
of the limestones into two
4
Geochemical characterisation
groups, based on elemental
concentrations, is also borne out by the modal analyses.
Group
elements.
magnetite,
marbles are richer in CaO and poor in other major
Presence of diopside, sphene, hornblende,
muscovite and higher percentages of
characteristic of group I I marbles. The
quartz are
ubiquitous
association of dolomite with silicates suggests that dolomite
is a product of silicate + calcite reaction and is presumed
to be not of primary origin. Geochemical
protolith consisting of an admixture of
variable proportions of marly impurities.
Migmatitic rocks comprise biotite
hornblende gneisses. A stromatic structure,
plots
imply a
limestone with
and biotite-
often grading
into 5urreitic and schollen types is exhibited with rafts of
amphibolite boudins preserved in them. They are medium-to
coarse-grained rocks, displaying xenomorphic granular
texture. Biotite gneiss is typically coarse-grained with a