Reconstructing physico-chemical parameters of hydrothermal mineralization of copper at the Malanjkhand deposit, India, from mineral chemistry of biotite, chlorite and epidote

Abstract

Mineral chemistry of biotite, chlorite and epidote associated with the granitoid ore body of the Malanjkhand coppermolybdenum deposit have been studied to constrain temperature, oxidation and sulfidation states as well as fugacity ratios of HF, HCl and H 2 O of the hydrothermal mineralizing fluid. Calculated mineralizing temperatures from biotite, chlorite and epidote are mutually consistent and agree well with earlier estimates derived from fluid inclusion studies. Major element chemistry of biotite indicates low oxidation state (FMQ-NNO) and re-equilibrated nature (~300°C). However, exchange of Cl-F-OH between biotite and the fluid continued to lower temperatures. Subtle differences between the Malanjkhand deposit and known porphyry copper deposits have been evidenced by the fugacity ratios of halogens and water. Chlorite registers equilibrium with fluid down to 200°C and, together with biotite composition, indicates that copper was transported as chloride complex in the fluid. Sulfide deposition occurred during a prompt rise in fugacity of H 2 S at 300°C, possibly resulting from a coupled oxidation of Fe 2+ and reduction of SO 4 2-. Interaction of ore fluid with epidote in the wall-rock favored the deposition of chalcopyrite, enhanced the Ca 2+ activity in the fluid and inhibited a fall in pH and a subsequent acid alteration of K-feldspar in the wall-rock. These physicochemical characteristics of the mineralized fluid suggest that the Malanjkhand deposit represents an ancient granitoid-associated geothermal system rather than a classic porphyry copper ore deposit.

Transitions between explosive and effusive phases during the cataclysmic 2010 eruption of Merapi volcano, Java, Indonesia

“…Biotite may have a magmatic origin but possibly may also originate from hydrothermal alteration of basaltic andesite or may be derived from metasomatic skarn material (e.g. Panigrahi et al 2008;Afshooni et al 2013;Balassone et al 2013). Biotite composition, especially in terms of its FeO, MgO, MnO, TiO 2 and Al 2 O 3 contents, is indicative of its mode of formation.…”

“…Biotite composition, especially in terms of its FeO, MgO, MnO, TiO 2 and Al 2 O 3 contents, is indicative of its mode of formation. For example, the mole fraction of Mg in the octahedral site (X Mg ) has been used to distinguish between igneous biotite and that which formed in hydrothermal alteration zones of porphyry deposits, with the hydrothermal biotite containing higher X Mg and less FeO (Selby and Nesbitt 2000;Panigrahi et al 2008). At Vesuvius for example, distinct mica compositions have been identified, depending on whether they are magmatic or associated with hydrothermal or metasomatic material (Balassone et al 2013).…”

Mineral chemistry of Plio-Quaternary subvolcanic rocks, southwest Yazd Province, Iran

“…Li et al 2003;Idrus et al 2007;Ayati et al 2008;Panigrahi et al 2008;Boomeri et al 2009). The fugacity ratios were estimated by using the equations for experimental and thermodynamic data of biotite (Munoz 1984(Munoz , 1992, which are based on the revised coefficients for F-Cl-OH partitioning between biotite and hydrothermal fluid Sverjensky 1991, 1992 Plio-Quaternary subvolcanic rocks on the Al 2 O 3 -FeO totMgO ternary diagram (de Albuquerque 1973) are shown in Figure 13A.…”

“…The mole fraction of Mg (X Mg ) in the M-site of biotite is a significant parameter to visualize trends, together with other elements in different sites of the biotite structure. It can also distinguish least altered and most altered biotite (Selby and Nesbitt 2000;Panigrahi et al 2008). In the studied biotite, variation of some elements at the tetrahedral (T) and octahedral (M) positions for the X Mg is given in Figure 9.…”

Comparative petrogenesis and tectonics of Paleoproterozoic Malanjkhand and Dongargarh granitoids, Central India

“…However, Stein et al (2004) suggest that MG may be part of a separate micro-continent in the Neoarchean-Paleoproterozoic times that experienced growth through subduction-related calc-alkaline magmatism and subsequently dismembered between the Bastar and Bundelkhand Cratons. Stein et al (2004Stein et al ( , 2006 also provided Re-Os models and isochron ages of molybdenite (2.49-2.44 Ga) from the Malanjkhand deposit and interpreted them as discrete deformation episodes and molybdenite deposition, which overlaps with the zircons ages ($2.48 Ga) possibly due to protracted or episodic hydrothermal activity (Panigrahi et al, 2008). Further, microstructural and anisotropy of magnetic susceptibility studies reveals that emplacement of MG and tectonic evolution of CITZ was synchronous during the Neoarchean/Paleoproterozoic time (Majumder and Mamtani, 2009).…”