Platinum group elements geochemistry of ultramafic and associated rocks from Pindar in Madawara Igneous Complex, Bundelkhand massif, central India

• Published in: Journal of Earth System Science 2013-02, Vol.122 (1), p.79-91
• Main Authors: BALARAM, V, SINGH, S P, SATYANARAYANAN, M, ANJAIAH, K V
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Chromite; Chromium; Copper; Crystallization; Dunite; Earth and Environmental Science; Earth Sciences; Electron microscopy; Geochemistry; Geology; Heavy metals; Iridium; Komatiites; Lava; Magma; Massifs; Metamorphism; Mineralization; Nickel; Olivine; Palladium; Platinum; Rhodium; Rocks; Saturation; Scanning electron microscopy; Silica; Silicon dioxide; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Sulfides; Sulphides; Sulphur; Titanium dioxide; Ultramafic materials; Ultramafic rocks
• ISSN: 0253-4126; 0973-774X
• DOI: 10.1007/s12040-012-0260-0

Ultramafic rocks comprising dunite, harzburgite, lherzolite, olivine webserite and websterite occur as intrusives in the form of small hillocks at Pindar into the granite–gneisses of Bundelkhand Gneissic Complex (BnGC). The peridotites are dominated by olivine cumulates where chromite and precious metal-bearing sulphides crystallized along with pyroxenes, subsequent to crystallization of olivine into the interstitial spaces of cumulates during cooling. Ultramafic rocks of Pindar are characterized by high MgO (up to 46.0 wt%) and FeO (up to 5.8 wt%); low SiO 2 (40.8 to 48.0 wt%), TiO 2 (0.2 to 0.5 wt%), Al 2 O 3 (~3.2 wt% av.), CaO (~2.7 wt% av.) and Cu (11 to 73 μg/g). Cr and Ni values range from 2297 to 3150 μg/g and 2434 to 2767 μg/g, respectively. Distribution of Ir (up to 20 ng/g), Ru (27 to 90 ng/g), Rh (3 to 14 ng/g), Pt (18 to 72 ng/g), Pd (10 to 27 ng/g) and Au (22 to 57 ng/g) indicate platinum group element (PGE) and associated gold mineralization in these ultramafic rocks. A mineral phase representing sperrylite (PtAs 2 ) was also identified within the sulphides in scanning electron microscopy with energy dispersive spectrometer (SEM–EDS) studies. The primitive mantle-normalized siderophile elements pattern shows platinum group element PGE (PPGE) enrichment (Rh, Pt, Pd). Discrimination diagrams of Pd/Ir vs. Ni/Cu, Pd/Pt vs. Ni/Cu, Cu/Pd vs. Pd, and Cu vs. Pd for the peridotites of Pindar attribute to affinity towards komatiite magma, derived from high degree of partial melting of prolonged depleted mantle, and the sulphur saturation condition incurred during the crystallization of chromite which was favourable for PGE mineralization.