On Chhoti Khatu volcanics of Rajasthan and its relationship with the Malani magmatism: A geochemical study
Malani Igneous Suite represents the largest felsic volcanic province in India. Despite a number of studies, the origin and the temporal extent of the Malani magmatism remain elusive. Adjacent to the Malani Igneous Suite, there exists a calcareous felsic tuff deposit at Chhoti Khatu within the younger Marwar Supergroup. It is stratigraphically separated from the Malani Igneous Suite by the Sonia Formation, the bottom-most formation of the supergroup, but falls within the temporal range of the Malani magmatism. In order to explore its genetic relationship with the Malani Igneous Suite and decipher its origin, trace element and C–O–Sr–Nd isotopic compositions of the tuff were studied. The results of the study show that the tuff differs geochemically from the MIS, and therefore, could not have been an extension of the Malani magmatism as believed by many earlier workers. On the basis of trace element patterns and Sr–Nd isotopic data, origin of the tuff is ascertained to the partial melting of Banded Gneissic Complex-II, the Archean–Paleoproterozoic basement of the region. The C and O isotopic composition of the carbonates from the tuff and a two-component mixing model reveal that the source (crustal) melt for the tuff had assimilated a significant amount of material from the rocks of the Sirohi Group. Since the timing of deposition of the tuff coincide with the emplacement of late-stage Malani dykes, it is likely that the final phase of Malani magmatism generated the heat for partial melting of the Archean–Paleoproterozoic basement.
$\bullet$ Chhoti Khatu Tuff differs geochemically from the Malani Igneous Suite rocks.
$\bullet$ They were formed by partial melting of the Banded Gneissic Complex-II.
$\bullet$ The source melt had assimilated a significant amount of material from the Sirohi Group rocks.
Volume 130, 2021
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