Geological, geochemical and Rb–Sr isotopic studies on tungsten mineralised Sewariya–Govindgarh granites of Delhi Fold Belt, Rajasthan, NW India

Abstract

Neoproterozoic granites are widespread in the Delhi Fold Belt of the Aravalli craton, some of which are associated with tungsten mineralisation. In one such instance, the volcano-sedimentary sequence of Barotiya Group in the South Delhi Fold Belt is intruded by a pluton of biotite granite gneiss known as Sewariya Granite (SG) and later by stocks and dyke swarm of tourmaline leucogranite known as Govindgarh Granite (GG). GG magmatism was associated with wolframite mineralisation in hydrothermal quartz veins occurring along the sheared contact between SG pluton and Barotiya mica schist. SG pluton shows the evidence of ductile and brittle deformations, whereas GG is by and large undeformed. Apart from quartz and feldspars, SG contains biotite and muscovite, and GG contains muscovite, tourmaline and garnet. Although both SG and GG are peraluminous, SG has a wide range of SiO 2 and narrow range of alkalis, and GG has a narrow range of SiO 2 and a wide range of alkalis. REE (rare Earth elements) modelling shows that the parent magma of SG and GG was derived from partial melting at different crustal levels. Rb-Sr isotope data of GG yield a mineral isochron age of 860 ± 7.4 Ma which represent the time of igneous crystallisation and cooling of the granite to less than 400 • C.

Dynamics, EPMA Th‐U‐Total Pb Monazite Geochronology and Tectonic Implications of Deformational Fabric in the Lower‐Middle Crustal Rocks: A Case Study of Ambaji Granulite, NW India

“…Association of slivers of basement gneisses (Tobisch et al, ) in this part of SDT supports the argument that the granulites were probably part of Sandmata terrane. Further, in the northern part, the SDT was intruded by several phases of granites such as circa 967 Ma old Sendra granite ( 87 Sr/ 86 Sr—Tobisch et al, ; U‐Pb TIMS—Pandit et al, ) and 860 Ma old Sewariya granite (Rb‐Sr magmatic cooling age; Sivasubramaniam et al, ). Both types show the imprint of pervasive deformational‐metamorphic fabric, suggesting a major tectonothermal event in the SDT could be much younger (≤860 Ma) than the age of Grenvillian orogeny.…”

Tracing source and palaeo‐weathering conditions of quartzose sandstone in the Cretaceous Cambay Basin: A combined petrographical, geochemical and geochronological approach

“…Prominent highlands in these areas include ADFB, Deodar Ridge and Devikot High (Figure 12). Accordingly, The Pan-African orogeny-related rocks are poorly exposed in the western and northwestern part of India (Ashwal et al, 2013;Crawford, 1975;Islam et al, 1999;Rathore et al, 1999;Xu et al, 2022; 8a; see also Ghosh et al, 2021;Just et al, 2011;Sivasubramaniam et al, 2019;Vijay Anand et al, 2018). Other 650-1000 Ma ages of monazite grains match with the rocks listed in Kaur et al, 2021) of the ADFBs (Table 5).…”

“…The numbered fields in the ternary Ca‐Fe tot ‐Mg plot represent different rock types: (1) Li‐rich granitoid pegmatites and aplites, (2) Li‐poor granitoids and associated pegmatites and aplites, (3) Ca‐rich metapelites, metapsammites and calc‐silicate rocks, (4) Ca‐poor metapelites, metapsammites and quartz‐tourmaline rocks, (5) Metacarbonates and (6) Metaultramafics. In addition, tourmaline compositions (green field) from Sewariya‐Govindgarh granites (Delhi Supergroup; Sivasubramaniam et al, 2019) and Balda‐Motiya granites (Delhi Supergroup; Ghosh et al, 2021) are shown for comparison, (b) The plot showing variation in rutile trace element concentrations on the source discrimination diagram (Nb vs. Cr; Triebold et al, 2012). As per the plot, detrital rutile grains originate from metapelitic source lithologies.…”

“…The REE pattern of possible source rocks are obtained from published data: (a) Mt. Abu granitoid, Erinpura granite and Marwar sediments: Ashwal et al, 2013; De Wall et al, 2022; George & Ray, 2017; (b) Granites and Sirohi metasediments: Arora et al, 2017; Ray et al, 2015; Sivasubramaniam et al, 2019).…”

Magmatic and Hydrothermal Ore Deposits

“…REE modelling of the Sewariya-Govindgarh pluton indicates partial melting in different crustal level for magma generation. Further, the Rb-Sr mineral isochron for the Govindgarh granite furnished an age of 860±7 Ma (Sivasubramaniam et al, 2019).…”