- Department of Earth Sciences, Pondicherry University, Puducherry, India (devikadev296@gmail.com)
The Vemula-Velpula hydrothermal barite deposit is hosted by mafic dykes (ca. 1850 Ma. [1]) intruding into the uppermost part of about 1900 m thick carbonate strata of the Vempalle Formation (ca. 2000 Ma. [2]) in Cuddapah basin and occurs as fracture-fill and breccia-fill veins. The veins dominantly consist of barite with minor quartz. The host mafic rock has undergone various extents of hydrothermal alteration, due to which the primary calcic plagioclase-clinopyroxene assemblage is altered to albite and clinochlore, along with the introduction of secondary epidote, quartz, and calcite. The wide range in Ba concentration of mafic rock (68 to 3012 ppm) associated with the barite mineralization indicates that Ba was mobilized and subsequently leached from the mafic rock by the hydrothermal fluid during this alteration event. The δ34S values of barite range from +16.19 to +23.24‰ which falls within the range of δ34S value of +10 to +30‰ estimated for Proterozoic seawater [3]. At shallow crustal depth where this deposit was formed, direct participation of seawater is unlikely and therefore basinal brine is inferred to be the source of sulphate ion required for barite mineralization. Primary aqueous biphase fluid inclusions in barite have homogenization temperatures ranging from 180 to 300 °C, with most of them clustering in the range 220-250°C, and salinities ranging from 2.4 to 25.8 wt.% NaCl equivalent. The first ice melting temperature of these inclusions was measured between -55 and -37°C, broadly pointing towards an H2O-NaCl-CaCl2 fluid system. Petrography and microthermometric data of fluid inclusions indicate the involvement of two fluids of different salinities, which, upon mixing and cooling, led to barite precipitation.
This research work was funded by SERB, New Delhi (Scheme No. CRG/2019/001015).
References
[1] Chakraborty K. et al. (2016), Journal of the Geological Society of India 87, 631–660.
[2] Rai A.K. et al., (2015), Journal of the Geological Society of India 86, 131–136.
[3] Strauss H (1993) Precambrian Research 63(3–4), 225–246.
How to cite: Devanand Sreekala, D. and Muthusamy, S. P.: Insight into the genesis of barite deposit in Vempalle Formation, Cuddapah basin, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4666, https://doi.org/10.5194/egusphere-egu25-4666, 2025.
