Geochemistry of Late Palaeoproterozoic (1.69 Ga) A‐type Mayong granitoids in Shillong Plateau, north‐east India: Implication for anorogenic magmatism during Columbia Supercontinent cycle

Abstract

The Late Palaeoproterozoic Mayong granitoids of Assam constitute an important component of the continental crust and the Basement Gneissic Complex in the northern extension of the Shillong Plateau, north‐east India. The basement rocks of Shillong Plateau are considered as a continuation of the Central Indian Tectonic Zone. In this study, emphasis is given on the new zircon U–Pb age, Hf isotopic composition, and the tectonic implication of Late Palaeoproterozoic Mayong granitoids. The Mayong granitoids are essentially composed of quartz—K‐feldspar—plagioclase—biotite—hornblende as major minerals and titanite—zircon—allanite—bastnaesite—apatite—ilmenite as the accessory mineral phase. They show typical geochemical characteristics of A‐type granites, such as high silica (average 71.86 wt%), alkalies (average 8.01 wt%), Rb, Zr, Nb, Ga, and rare earth elements (except Eu); high FeOt/MgO and Ga/Al ratios, and low CaO, MgO, Ba, Sr, P, Eu, and Ti concentrations. Laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating indicates that they were emplaced at ~1,687 ± 35 Ma during the large‐scale magmatism of Late Palaeoproterozoic to Early Mesoproterozoic periods. Their zircon Hf model (TDM2) ages (1,833–2,257 Ma) in conjunction with trace elemental characteristics suggest that they were generated by the reworking/recycling of Early Palaeoproterozoic crust in an intraplate extensional tectonic environment. Thus, we conclude that these A‐type Late Palaeoproterozoic Mayong granitoids of the Shillong Plateau probably have a close genetic linkage with the magmatic event of the Columbia Supercontinent cycle during 1,687 ± 35 Ma.

Geochemistry of meta‐mafic and meta‐tonalite‐trondhjemite intrusives from Jaintia and Karbi Anglong hills of Shillong Plateau, North East India: Implications on the evolution of the Proterozoic Shillong Basin

“…The geological architecture of the Shillong Plateau (SP) encompasses the Khasi, Jaintia, and Garo Hills of Meghalaya and Karbi Anglong and Mikir Hills of Assam. It constitutes rocks of Precambrian (Archaean to Late Proterozoic), Early Palaeozoic, Permian, Cretaceous, Tertiary, and Quaternary Eras (Figure 1; Anon, 1974; Bhattcharjee & Rahman, 1985; Doley et al, 2021; Evans, 1964; Gogoi, 1975; Khonglah et al, 2008; Khonglah, Sougrakpam, Imchen, & Baskaran, 2016; Khonglah, Sougrakpam, Rudra, & Datta, 2016; Mazumdar, 1986; Meddlicott, 1869; Nandy, 2001; Oldham, 1858; Pascoe, 1950; Rahman, 1999). The SPGC is considered to be a detached part of the Indian shield (Evans, 1964), an extension of the Chotanagpur Gneissic Complex (Acharyya, 2003; Dwivedi et al, 2010), or the NE extension of the Eastern Ghat Mobile Belt (Bidyananda & Deomurari, 2007; Crawford, 1974; Khonglah et al, 2008, 2010; Khonglah, Sougrakpam, Imchen, & Baskaran, 2016; Khonglah, Sougrakpam, Rudra, & Datta, 2016; Yin et al, 2010).…”

“…The geological architecture of the Shillong Plateau (SP) encompasses the Khasi, Jaintia, and Garo Hills of Meghalaya and Karbi Anglong and Mikir Hills of Assam. It constitutes rocks of Precambrian (Archaean to Late Proterozoic), Early Palaeozoic, Permian, Cretaceous, Tertiary, and Quaternary Eras (Figure 1; Anon, 1974;Bhattcharjee & Rahman, 1985;Doley et al, 2021;Evans, 1964;Gogoi, 1975;Khonglah et al, 2008;Khonglah, Sougrakpam, Imchen, & Baskaran, 2016;Khonglah, Sougrakpam, Rudra, & Datta, 2016;Mazumdar, 1986;Meddlicott, 1869;Nandy, 2001;Oldham, 1858;Pascoe, 1950;Rahman, 1999).…”

Introduction, Part 2—Geodynamic evolution of Eastern Himalaya and Indo‐Myanmar orogenic belts: Advances through interdisciplinary studies

“…The geology of the Shillong Plateau dates back to the Late Archean, when a sag basin was formed due to a plume‐induced thermal upsurge, producing the Basement Gneissic Complex (BGC) as early as 2,670 Ma (Majumdar & Dutta, 2016). It constitutes rocks of Precambrian (Archaean to Late Proterozoic), Early Palaeozoic, Permian, Cretaceous, Tertiary, and Quaternary (Bidyananda & Deomurari, 2007; Doley et al, 2022; Evans, 1964; Ghosh et al, 1991; Kumar et al, 2017; Yin et al, 2010).…”

“…This Special Issue‐ Part 2 is a continuation of earlier Special Issue‐ Part 1 published in vol. 57 (2), of Geological Journal , which contained 26 research articles (Ao & Satyanarayanan, 2022; Baral et al, 2022; Bhowmik et al, 2022; Bora, Borah, et al, 2022; Bora, Mukherjee, et al, 2022; Deb & Ray, 2022; Devi & Singh, 2022; Devrani et al, 2022; Doley et al, 2022; Gogoi et al, 2022; Gupta et al, 2022; Hazarika & Kayal, 2021; Imtisunep et al, 2022; Liu et al, 2022; Luirei et al, 2022; Lukram & Tandon, 2022; Bidyananda et al, 2022; Majumdar, Gogoi, & Ghatak, 2022; Majumdar, Gogoi, Ghatak, Saikia, et al, 2022; Mukherjee et al, 2022; Pebam et al, 2021; Rashid et al, 2022; Saikia et al, 2022; Singh and Kshetrimayum, 2021; Singh, Guruaribam, Singh et al, 2022; Singh, Singh, Singh, et al, 2022; Srivastava, 2021; Srivastava & Kichu, 2021). Figure 2 displays the area of study of 29 papers included in this Special Issue 2.…”

“…This Special Issue-Part 2 is a continuation of earlier Special Issue-Part 1 published in vol. 57 (2), of Geological Journal, which contained 26 research articles (Ao & Satyanarayanan, 2022;Baral et al, 2022;Bhowmik et al, 2022;Bora, Mukherjee, et al, 2022;Deb & Ray, 2022;Devrani et al, 2022;Doley et al, 2022;Gogoi et al, 2022;Gupta et al, 2022;Hazarika & Kayal, 2021;Imtisunep et al, 2022;Liu et al, 2022;Luirei et al, 2022;Lukram & Tandon, 2022;Bidyananda et al, 2022;Majumdar, Gogoi, Ghatak, Saikia, et al, 2022;Mukherjee et al, 2022;Pebam et al, 2021;Rashid et al, 2022;Saikia et al, 2022;Singh and Kshetrimayum, 2021; F I G U R E 1 (a) Tectonic map of the peri-Indian region, showing the current plate boundaries and plate distributions, major continental blocks, suture zones, and salient fault systems. (b) Simplified regional geologic map of the Himalayan Orogen, Indo-Myanmar orogenic belt and adjoining areas (modified after Mitchell et al, 2007;Singh, 2013;Yin, 2006) Singh Srivastava, 2021;Srivastava & Kichu, 2021).…”