ARTICLE Geochemistry and mineralogy of Pd in the magnetitite layer within the upper gabbro of the Mesoarchean Nuasahi Massif (Orissa, India) Hazel M. Prichard 1 & Sisir K. Mondal 2 & Ria Mukherjee 3 & Peter C. Fisher 1 & Nicolas Giles 1 Received: 26 October 2016 /Accepted: 26 June 2017 /Published online: 20 July 2017 Abstract Palladium concentrations of 1–3 ppm with an aver- age Pt/Pd ratio of 0.15 have been located for the first time in a magnetitite layer in the Nuasahi Massif in Orissa India. This layer occurs at a high stratigraphic level in the complex and is nearly 4-km long and 5–12-m thick. The sections of the Pd- rich zone identified to date extend over a distance of 1 km at the southern end of the layer. Several phases of mineralization are evident. The first, primary assemblage of platinum-group minerals (PGM) contains Pd-sulfides (vysotskite), Pd-Pb al- loys (zvyagintsevite), and a Pd-In alloy, a mineral probably new to mineralogy. These PGM are confined to central mag- netite grains in the magnetitites. The magnetite grains with exsolved fine laths of ilmenite at centers are referred to as central magnetite grains. These central magnetite grains are commonly surrounded by blebs of ilmenite and magnetite that contain the majority of the PGM. These are dominated by Pd- antimonides, variably altered to Pd-oxides, and other PGM including PtAs 2 (sperrylite), RuS 2 (laurite), and IrRhAsS (irarsite/hollingwothite). Many of these PGM also occur in the interstitial silicates, with rare occurrences in the central magnetite grains. We propose that the platinum-group ele- ments (PGE) crystallized during a minor sulfide saturation event that occurred as the magnetitites crystallized. This event produced the minor Cu-sulfides in these magnetitites. Later introduction of antimony and arsenic, during the alteration event that produced the blebby ilmenite and magnetite, led to the more primary PGM being succeeded by the main PGM assemblage, dominated by Pd-antimonides. These are associated with secondary Cu minerals and sperrylite. Subsequent oxidation during weathering in the hot wet Indian climate produced the Pd-oxides. The Nuasahi Massif is a sill-like Archean layered ultramafic-mafic intrusion genet- ically linked to high-Mg siliceous basalt or boninites and is characterized by unusually thick layers of chromitite. PGE are concentrated in these chromitites and in the base metal sulfide- bearing breccias in the overlying gabbro. The Pd in the magnetitites described here indicates the presence of a third level where PGE are concentrated and a magma that crystal- lized to produce PGE concentrations at three stratigraphic levels in the massif. This indicates that similar thin sill-like intrusions, hosting unusually thick chromitites, may also have PGE concentrations at a number of stratigraphic levels. Keywords Platinum-group elements . Palladium . Magnetitite . Chromitite . Sill-like layered igneous complex . Upper gabbro unit . Nuasahi Massif Introduction Magnetitite layers or magnetite-rich lithologies are a common occurrence in the upper parts of mafic and ultramafic igneous intrusions at a level where the magma is in the final stages of Editorial handling: M. Fiorentini Hazel M. Prichard deceased Electronic supplementary material The online version of this article (doi:10.1007/s00126-017-0754-4) contains supplementary material, which is available to authorized users. * Sisir K. Mondal sisir.mondal@gmail.com 1 School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, UK 2 Department of Geological Sciences, Jadavpur University, 188 Raja S.C. Mallik Road, Kolkata 700032, India 3 School of Geosciences, University of the Witwatersrand, Johannesburg 2001, South Africa Miner Deposita (2018) 53:547–564 DOI 10.1007/s00126-017-0754-4 # Springer-Verlag GmbH Germany 2017