Indian Journal of Geosciences, Volume 68, No. 2 & 3 April - September, 2014; pp. 211-222
Nature of PGE mineralization in the ultramafics of Kondapalli Layered Complex, Andhra Pradesh Tushar M. Meshram1*, Shraddha Nannaware1, Santanu Bhattacharjee1 and T. Rajakumar1 1 Geological Survey of India, Southern Region, Bandlaguda, Hyderabad 500 068, Andhra Pradesh, India
*Corresponding author. E-mail:
[email protected]
Abstract: Scanning electron microscope studies reveal the presence of platinum group of minerals as inclusions within chromite in orthopyroxenite of the Kondapalli Layered Complex (KLC). The minerals identified are mainly laurite (RuS2), irarsite (IrAsS), iridosmine (Os-Ir alloys), unidentified PGE-alloys i.e., (Ir + Os + Zr) and (Ir + Os + S). They are usually less than 10 µm in size, euhedral to subhedral, white to light greyish white with high reflectance and occur within chromite and pyroxene. Mineralogy and textural relations indicate that most of the PGM in the KLC chromitite have crystallized at high magmatic temperatures, prior to or concomitant with precipitation of chromite. Chemical analysis of bed rock samples shows åPGE values ranging from 55 ppb to 173 ppb, in which IPGE group (Ir- group) dominates over PPGE group (Pt-group). Analytical results show inhomogeneous distribution of PGE due to random occurrence of PGM. Keywords: PGM, chromite, Kondapalli Layered Complex
Introduction
PPGE (Pt group) assemblages (Barnes et al., 1988). PGE is
The platinum group of elements (PGE) is the most valuable of elements and is of strategic importance due to its growing
rocks. These magmatic sulphide deposits can be classified into two major groups: (a) those that are valued primarily for their
use in advanced technologies. PGE also has unique
Ni and Cu and that are mostly sulphide-rich (>10% sulphide),
geochemical characteristics, can be used to identify the
and have formed as a result of an interaction of mantle-derived
magma sources and unravel the complex petrogenetic processes, such as partial melting, melt percolation, and
magma with the crust that gave rise to the early sulphide immiscibility, like the komatiite-related deposits and (b) those
metasomatism in the mantle (Barnes et al., 1988). Mafic-
that are valued primarily for their PGE, concentrated in well-
ultramafic rocks have lower REE contents but higher PGE
defined stratiform layers (reefs) of large intrusions and are
contents than other rocks, so the PGE has advantages in studying petrogenetic processes (Barnes et al., 1985; 1988;
sulphide-poor (
