LITHOSTRATIGRAPHIC, GEOCHRONOLOGICAL AND DEPOSITIONAL FRAMEWORK OF THE MORLI – KHIWANDI PRECAMBRIAN METASEDIMENTS OF SIROHI AND PALI DISTRICT OF RAJASTHAN

Harish Kapasya; Ritesh Purohit; K.K. Sharma

Volume : VII, Issue : VI, June - 2017

LITHOSTRATIGRAPHIC, GEOCHRONOLOGICAL AND DEPOSITIONAL FRAMEWORK OF THE MORLI – KHIWANDI PRECAMBRIAN METASEDIMENTS OF SIROHI AND PALI DISTRICT OF RAJASTHAN

Harish Kapasya, Ritesh Purohit, K. K. Sharma

Abstract :

The Sirohi Group is the youngest of the three Precamian orogenic metasedimentary/metavolcanic sequences in northwestern India, which along with granitoids and granite gneisses constitute the southwestern part of the Aravalli Mountain belt. The Neoproterozoic Sirohi orogeny (850 Ma) marks closure of compressional tectonic regime in the Aravalli craton. The beginning of Neoproterozoic marks one of the most dynamic periods in the history of the earth. The Morli–Khiwandi study area lies in north of Sirohi, Rajasthan and located in the Survey of India Toposheet No. 45C/16, 45G/4 and 45G/3. The study area is situated in eastern and northern part of Sumerpur town. These forms linear outcrop south–west of the Aravalli Mountain Belt. The Morli–Khwandi metasediments are part of Sirohi Group dominantly comprises shale sandstone–carbonate–carbon shale metasediments. Some of these metamorphic rocks were subjected to mylonitization and contact metamorphism. The metasediments form outcrops in the Erinpura granitoid terrain. The metasediments are phyllite, quartzite, calc–silicate and carbon phyllite. Geological evidence suggests evolution of the Sirohi basin developed subsequent to cratonization of the underlying Delhi Supergroup rocks at ca 1450 Ma. (Roy and Das 1985. The Neoproterozoic age of the Sirohi Group is based on reports of younger tectono–thermal events between 1200 and 950 Ma from the region surrounding the Sirohi basins (Deb et al. 1989, 2001; Fareeduddin and Kröner, 1998;; Pandit et al., 2003; Volpe and McDougall, 1990; Purohit et al., 2012). A middle to late Neoproterozoic age for the Sirohi Group is also inferred from the field association of these rocks with ca. 850 Ma old granitoids (Choudhary et al. 1984) and from several isotopic ages in the range of ~780–680 Ma for the Malani volcanics and plutonic felsic activity. The magma resulted in thermal resetting of older granitoids and other Sirohi rocks. This hypothesis is confirmed from Lithostratigraphic & structural evidences. The research study further indicate northwest drifting and an enechelon distribution pattern and last phase of geodynamic resetting in the region.