Evidence of intraplate magmatism and subduction magmatism during the formation of Nagaland–Manipur Ophiolites, Indo–Myanmar Orogenic Belt, north‐east India

Abstract

Mafic extrusive rocks (basalts) and intrusive rocks (gabbros) from the Nagaland–Manipur Ophiolite (NMO) of the Indo–Myanmar Orogenic Belt (IMOB), north‐east India, are investigated to understand their magmatic evolution in diverse tectonic environments. Basalts are distinguished into two types: basalt‐I and basalt‐II. Basalt‐I type shows the sub‐alkaline character with Nb/Y < 0.50, low Nb/Th (2.36–7.94), and low to moderate La/Sm (1.00–4.12) indicating derivation from a slightly enriched mantle source and also supported by their enriched LREE pattern with flat HREE. They are depleted in HFSEs (Nb and Ti) but enriched in U and Pb, which is indicative of a typical subduction origin derived from an MORB‐type mantle source. Investigated samples of basalt‐II and gabbros have an equal composition with alkaline characteristics. They have Nb/Y > 0.50, high Nb/Th (8.38–13.37), and highly enriched LREE (La/Sm = 4.41–6.35) pattern. They show typical Ocean Island Basalt (OIB) characters of a plume source. The two sets of basalts and gabbros found in this study have no sign of genetic relationship, and therefore, it strongly suggests that they were derived from two different mantle sources of a plume and a subduction zone mantle wedge. Our study supports the theory that the NMO has records of different magmatic episodes produced ranging from plume‐related magmatism, to divergent and convergent plate magmatism that were generated at diverse tectonic settings.

Refertilization of depleted mantle peridotite in the Nagaland–Manipur ophiolite, north‐east India: Constraints from PGE, mineral, and whole‐rock geochemistry

“…The NMO is highly tectonized and dismembered, the westerly convex arcuate belt of ~200 km length extending from north‐east of Chokla in Nagaland to Moreh in Manipur, with an average width of ~15 km (Chattopadhyay, Venkataramana, Roy, Bhattacharyya, & Ghosh, 1983). Ophiolites in the NMO (Figure 1c) have mainly formed in the SSZ setting but contain rocks of varied affinities, such as MORB, OIB, and IAT (Abdullah, Misra, & Ghosh, 2018; Imtisunep et al, 2022; Khogenkumar et al, 2016, 2020; Sengupta et al, 1989; Singh, 2013; Singh et al, 2013; Singh, Nayak, et al, 2017; Zaccarini et al, 2016). These ophiolites have undergone different phases of tectonism, metamorphism, magmatism, and metallogenic events that mimic the Himalayan Orogeny (Ghose, Agrawal, & Chatterjee, 2010).…”

Source characterisation of the residual lherzolite and harzburgite ultramafics of Manipur Ophiolite Belt in the Indo–Myanmar Hill ranges, NE India

“…It is reported that the rocks of the MOMZ formed during forearc‐backarc magmatism in a supra‐subduction zone, probably when the Indian Plate was subducting underneath the Myanmar Plate (Ao & Bhowmik, 2014; Chaubey et al, 2022; Kingson et al, 2019; Singh et al, 2016; Singh et al, 2021; Zaccarini et al, 2016). However, it is also proposed that this ophiolite was formed in a mid‐oceanic ridge spreading center (Ningthoujam et al, 2012; Singh, 2009; Zaccarini et al, 2016), or plume‐ridge interaction as one event and subduction magmatism as another event (Imtisunep et al, 2022; Khogenkumar et al, 2016, 2020). Although many studies have reported the formation age of this ophiolite, there is general agreement that the upper limit age probably extends up to the Eocene, while the lower age limit is probably Upper Jurassic.…”

Stable isotope geochemistry and microfossil assemblages of carbonate rocks in the ophiolite mélange zone of the Indo–Myanmar orogenic Belt, NE India: Implications on age and depositional environment

“…The ophiolite sequences occurring all along the Tuting‐Tidding Suture Zone, which runs east of the Siang Antiform have been considered as the south‐eastern extension of the ITSZ (Dutt, Singh, Oinam, & Srivastava, 2021; Dutt, Singh, Srivastava, & Oinam, 2021; Dutt, Singh, Srivastava, Oinam, & Bikramaditya, 2021; Singh et al, 2021; Singh & Singh, 2011, 2013). The suture zone further extends south to the IMOB and the Andaman‐Nicobar Island Arc (Chaubey et al, 2022; Imtisunep et al, 2022; Khogenkumar et al, 2016, 2021; Premi et al, 2022; Singh, 2009; Singh, 2013; Singh et al, 2012; Singh et al, 2013; Singh, Nayak, et al, 2017).…”