The role of fluids in the formation of talc deposits of Rema area, Kumaun Lesser Himalaya

Abstract

Talc deposits of Rema area in the Kumaun Inner Lesser Himalaya are hosted within high magnesium carbonates of the Proterozoic Deoban Formation. These deposits occur as irregular patches or pockets mainly within magnesite bodies, along with impurities of magnesite, dolomite and clinochlore. Textures represent different phases of reactions between magnesite and silica to produce talc. Petrography, XRD and geochemistry reveal that the talc has primarily developed at the expense of magnesite and silica, leaving dolomite largely un-reacted. Early fluid inclusions in magnesite and dolomite associated with talc are filled with H 2 O+NaCl+KCl± MgCl 2 ± CaCl 2 fluids, which represent basin fluid system during diagenesis of carbonates. Their varied degree of re-equilibration was although not pervasive but points to increased burial, and hence requires careful interpretation. H 2 O-CO 2 fluid with XCO 2 between 0.06 and 0.12 was equilibrated with talc formation. The reaction dolomite+quartz o talc was not extensive because T-XCO 2 was not favourable, and talc was developed principally after magnesite+quartz.

WITHDRAWN: Seismic Imaging of the Kumaon-Garhwal Himalaya: Insights into the Main Himalayan Thrust and the Crust-Mantle Boundary

“…Then, our modelled seismic velocity values reduce between 5 and 15 km depths, suggesting a 10-20% drop in Vp, dVp, Vs and dVs and an increase in Vp/Vs by 10-14%, which could be explained in terms of the presence of meteoric water, aqueous uids and wet-sediments of the Eurasian plate. Several studies [32][33][34] (Boulier et al, 1991;Sachan et al, 2001;Sharma et al, 2008) have shown that the uids in the higher Himalaya and the MCT are dominantly carbonic whereas the uids in the Lesser Himalaya and the MBT are dominantly brines or syntectonic uids (Ojha and Srivastava, 2016). Between 15 and 20 km depth, a slight increase (i.e.…”

Genetic Classification of Pyroclastic Ejecta Based on Physical Volcanology of Possible Large Cauldron in Bombay Volcanic Complex, Western Deccan Trap Province, India

“…For this purpose, the study area has been subdivided into various sectors characterized by a common field and depopsitional characteristics. The pyroclastic ejecta in the area has been grouped in various sub groups based on clastsize, type of the clasts, and depositional features/structures associated with them (R.K. Sharma, 2000 [54], 2020 [55], 2022 [56] and Sharma 1992 [8], 2018 [57], Sharma and Pandit 1998 [58]). The main categories identified are…”

“…compositionally banded vitric tuffs along with agglomerates of varying thickness and proportion dot the entire area. Felsic rocks including the compositionally banded (light and gray) tuffs together with andesitic and acidic flows as well as pumiceous flows of the acidic nature(Sharma and Pandit, 1998) [58], constitute an important litho unit in the area and forms parts of this category of deposit.The banded and pumiceous nature has a significant bearing on the mechanismof deposition. The salient characters of these rocks exposed in various areas are summarized for attempting a non-genetic classification.…”

An Experimental Study of the Formation of Talc through CaMg(CO3)2–SiO2–H2O Interaction at 100–200°C and Vapor-Saturation Pressures

“…The most economically viable of these deposits are usually related to the metamorphic reaction between an Mg-carbonate infiltrated by a silica-rich hydrothermal fluid [18,20,21,37]. Intense fractures that increase the permeability of geological fluid flow generally develop near such deposits [18,20,21,37,38]. Investigating the formation temperature of talc can improve our understanding of its mineralization process.…”

“…The reaction has been theoretically calculated to occur at ≥150 ∘ C [5,35,36], but most geological studies have indicated that talc mainly forms at 250-400 ∘ C (e.g., [21,37,38]). For example, in the Saint-Barthélemy deposits in Switzerland, oxygen isotope thermometric calculations showed that talc mineralization occurred at about 300 ∘ C [21], which is consistent with fluid inclusion data (250-300 ∘ C) [39,40].…”