Geochemical characterization, petrogenesis, and emplacement tectonics of Paleoproterozoic high‐Ti and low‐Ti mafic intrusive rocks from the western Arunachal Himalaya, northeastern India and their possible relation to the ~1.9 Ga LIP event of the Indian shield

Abstract

Paleoproterozoic mafic intrusive rocks from the western Arunachal Himalaya have been studied for understanding their petrogenesis and tectonic environment, in which they were emplaced, with the help of their bulk-rock major, trace, and rare-earth elements (REE) compositions. These mafic intrusive rocks, mostly small bodies of dykes, sills, and lenses, are exposed in the Higher as well as the Lesser Himalaya sequences. Geochemically, 2 suites of rocks are identified and grouped into high-titanium and low-titanium mafic intrusive rocks. High-titanium mafic intrusive (HTMI) samples have comparatively low Mg number (Mg#) and high high-field strength element contents in comparison to low-titanium mafic intrusive (LTMI) rocks. Multielements and REE patterns for these two identified groups are distinct. The LTMI and HTMI were originally spatially separated at the time of their emplacement and believed that probably they have been juxtaposed during the Himalayan orogeny by crustal shortening through development of imbricated thrusts. It is perceived that the HTMI and LTMI have different petrogenetic histories and are derived from two different melts; however, they are postulated to be parts of the same igneous province. Geochemical characteristics do not support any serious effect of crustal contamination; however, interaction with metasomatized lithospheric mantle cannot be discounted. Trace element petrogenetic modelling suggests derivation of the LTMI samples from a parental magma generated in spinel stability field (thin lithosphere) through a~20-25% melting of a lherzolite mantle source, whereas the HTMI samples were derived from~5-10% melting of a similar mantle source but from garnet stability field (thick lithosphere). Widespread Paleoproterozoic mafic events in the Indian shield such as Bastanar dyke swarm in the Bastar and the Hampi dyke swarm (also includes Pulivendla sills in the Cuddapah Basin) in the eastern Dharwar Craton together with mafic intrusive and extrusive rocks in the Himalayan region suggest presence of a large igneous province at~1.9 Ga.

Spatial and Temporal Distribution of Large Igneous Provinces in the Indian Shield – Highlights of Recent Investigations

“…It is suggested that these two distinct geochemical groups of the intrusive rocks were derived from discrete mantle melts; one group from 20-25% melting in the spinel stability field (thinner lithosphere), whereas the other group was derived from ~5-10% melting of a similar mantle source but in garnet stability field (thicker lithosphere). Rashid et al (2019) have also studied metabasic rocks from Lesser Himalayan sequence, western Arunachal Pradesh, for their geochemistry and presented almost similar results as observed by Srivastava and Samal (2019).…”

“…1.80-1.90 Ga mafic intrusive rocks within the Himalayan Mountain Range are also thought to be part of the shared ca. 1.85-1.90 Ga LIP event (Srivastava and Samal, 2019;Samal et al, 2019a,b).…”

“…The bimodal association is due to mantle upwelling which leads to the melting of thin crust. Srivastava and Samal (2019) studied the geochemical characteristics of Paleoproterozoic mafic intrusive rocks from the western Arunachal Himalaya, which is thought to be a part of the ca. 1.85-1.90 Ga LIP, to understand their petrogenesis and tectonic environment.…”

Paleoproterozoic ($$\sim$$1.88–1.89 Ga) ultramafic–mafic sills, Cuddapah basin, India—revisited: Implications for interaction between mantle plume and metasomatized subcontinental lithospheric mantle

“…A number of 1.88-1.89 Ga mafic/ultramafic sills are widely intruded and well-exposed in the lower startigraphic horizons of the Proterozoic Cuddapah intracratonic basin (Anand et al 2003;French et al 2008) (see figure 1). It is suggested that these mafic/ultramafic sills are integral part of a widespread *1.88-1.89 Ga Large Igneous Province (LIP) (Ernst and Srivastava 2008;French et al 2008;Belica et al 2014;Srivastava et al 2014a;Srivastava and Samal 2019), identified as a plume derived Hampi-Bastanar LIP (Samal et al 2019). However, Sheppard et al (2017) have provided a range of emplacement ages (1864AE13 and 1858AE16 Ma) for the felsic tuffs from the upper part of the Tadpatri Formation suggesting a series of magmatic events for *30 Ma and argued for a nonplume origin.…”

Himalayan Magmatic Events

“…1300 Ma. Similarly, Srivastava and Samal (2019) analyzed mafic intrusive bodies from the Lesser and Higher Himalayas between Bomdila and Tawang in western Arunachal Pradesh. They concluded that the mafic magmatism is part of two distinct Paleoproterozoic mafic intrusive rocks occurring as small bodies of dikes, sills, and lenses.…”