Mineralogical variation in platinum group element within altered chromitite of the Kondapalli Layered Igneous Complex (Southern India): implication on magmatic evolution and its petrogenetic significance

Минералогические вариации элементов платиновой группы в измененном хромитите расслоенного магматического комплекса Кондапалли (Южная Индия): влияние на эволюцию магматизма и его петрогенетическое значение

Platinum Group Minerals (PGMs) associated with Chromite form in a wide range of geotectonic settings, namely, (1) stratiform or layered magmatic complexes, (2) podiform complexes in ophiolites, (3) the Alaskan zoned complexes and (4) Chromite-rich Archean complexes are also called ‘conduit-type’ (Mondal and Baidya, 1997; Auge et al., 2002; Ahmed and Arai, 2003; Economou-Eliopoulos, 2010; Mukherjee et al., 2012; Mungall, 2014; Peck and Huminicki, 2016; O’Driscoll and González-Jimenez, 2016; Prichard et al., 2017a-b; Mondal et al., 2019). They may also form as a result of hydrothermal remobilization and may occur as placers. Economic deposits of platinum-group elements (PGEs) in mafic-ultramafic layered intrusions that are derived mainly from basaltic magmas are commonly referred to as PGE-reefs and are the primary hosts of the world’s significant PGE resources (Scoates and Friedman, 2008; Mungall and Naldrett, 2008; Naldrett et al., 2008; Peck and Huminicki, 2016; Barnes and Ripley, 2016; Day et al., 2008; O’Driscoll et al., 2009). The key factors responsible for the formation of large and super-large magmatic sulfide deposits (Ni-Cu-PGE) are (1) large volumes of mantle-derived mafic-ultramafic magmas that are participated in the formation of the deposits; (2) fractional crystallization and crustal contamination, particularly the input of sulfur from crustal rocks, resulting in sulfur saturation and immiscibility and segregation metal-sulfide liquid; and (3) the timing of sulfide concentration in the intrusion (Song et al., 2011). PGE associated with Ni-Cu sulfides in magmatic rocks are also classified into two major groups, (a) Komatiite-related sulfiderich deposits (>10% sulfide), which are formed due to interaction of mantle-derived magma within the crust that gave rise to the early sulfide immiscibility and (b) stratiform layers (reefs) of large intrusions, e.g., the Bushveld Complex, South Africa, which are generally sulfide poor (<5% sulfide). Earlier it was divided into Ni-Cu-PGE and Ni-Cu-(Co) deposits (Lesher and Keays, 2002; Seabrook et al., 2004; Naldrett et al., 2008; Naldrett, 2010; Song et al., 2011; O’Driscoll and González-Jimenez, 2016; Lu et al., 2019).  <...>