August 2023 LIP of the Month

Multiple magma pulses during the main stage of the Greater Kerguelen mantle plume/LIP: evidence from Early Cretaceous mafic dykes of the Chhota Nagpur Gneissic Terrane, eastern Indian Shield

Rajesh K. Srivastava^1*, Fei Wang², Wenbei Shi² and Richard E. Ernst³

¹Centre of Advanced Study in Geology, Institute of Science, Banaras Hindu University, Varanasi 221005, India

²State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, P.R. China

³Department of Earth Sciences, Carleton University, Ottawa, ON K1S5B6, Canada

*Corresponding author’s e-mail: rajeshgeolbhu@gmail.com

Extracted and updated from

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ABSTRACT

A number Early Cretaceous (mostly emplaced between ca. 145 and 100 Ma) magmatic rocks are recorded in south-eastern Tibet, eastern and north-eastern India, western Australia, Eastern Indian Ocean, southern Kerguelen Plateau, and north-eastern Antarctica regions, which are collectively considered to be related with the Kerguelen mantle plume and identified as the Greater Kerguelen Large Igneous Province. Their likely connection with the break-up of East Gondwana is also well-established. Broadly, two major magmatic phases are identifiedfrom ca. 145 to 130 Ma (initial stage), between ca. 124 and 100 Ma (main stage). A third phase (plume tail) is also recorded between ca. 100 Ma and present day.

The Chhota Nagpur Gneissic Terrane (CNGT) of the eastern Indian Shield includes units related to the main stage (ca. 124-100 Ma) of the Greater Kerguelen mantle plume. These include ca. 118-102 Ma Rajmahal tholeiite basaltic flows, ca. 118-109 Ma dolerite dykes, and ca. 114-113 Ma high-potassic dykes. Herein, the genetic aspects of Early Cretaceous NNW- to WNW-trending dolerite dykes, identified as the Raniganj-Koderma swarm, are discussed for their likely connection to the Kerguelen mantle plume. Combining ⁴⁰Ar/³⁹Ar dates and geochemical data on these dykes helped to identify three distinct magma pulses, which are emplaced ca. 118-116 Ma, ca. 112-111 Ma, and ca. 109 Ma. Their geochemical characteristics clearly suggest that these were derived from OIB – E-MORB type mantle melts, which is likely to be generated due to interaction of a plume with a spreading ridge.

Keywords: Early Cretaceous; dolerite dykes; Ar⁴⁰-Ar³⁹ date; Geochemistry, Greater Kerguelen LIP; Eastern India.

Introduction

A number of mantle plume induced intraplate Large Igneous Provinces (LIPs) are identified in the Indian Shield throughout the Earth’s history; mostly derived from mantle melts (e.g., Ernst and Srivastava, 2008; Ernst, 2014; Samal et al., 2019, 2021; Srivastava, 2020a,b, 2022; Srivastava et al., 2022 and references therein). The age of these LIPs range from Precambrian (oldest ca. 3.35-3.34 Ga – Sargur LIP; Samal et al., 2021) to Phanerozoic – mostly Cretaceous (youngest ca. 66.0-65.5 Ma – Deccan LIP; cf. Courtillot et al., 1988; Chenet et al., 2007; Hooper et al., 2010).

Amongst the two notable Cretaceous LIP events recorded in the Indian Shield, i.e., the Early Cretaceous Greater Kerguelen LIP (e.g., Kent et al., 2002; Coffin et al., 2002; Srivastava et al., 2020, 2023; Srivastava, 2022) and the Late Cretaceous (-Paleocene) Deccan LIP (e.g., Courtillot et al., 1988; Chenet et al., 2007; Hooper et al., 2010), the former dominates in the eastern and north-eastern region of the Indian Shield (see Fig. 1). Early Cretaceous magmatic rocks, ranging in composition from ultrapotassic-alkaline-carbonatite to mafic-ultramafic, are well exposed in the Chhota Nagpur Gneissic Terrane (CNGT; the eastern region) and Shillong Plateau (north-eastern region) (Fig. 1; see Table 1 for more details; cf. Srivastava, 2020a, 2022).

These different magmatic units are derived from distinct mantle melts and can be separated in space and time (e.g., Ray and Pande, 2001; Kent et al., 2002; Coffin et al., 2002; Ray et al., 2005; Ghatak and Basu, 2011, 2013; Srivastava et al., 2005, 2014, 2019, 2020, 2022, 2023; Srivastava, 2020a,b, 2022), however all of them are connected, directly or indirectly, with the second (main) phase of Kerguelen plume event (see Srivastava, 2022, Srivastava et al., 2023 for review).

The CNGT encompasses Early Cretaceous basaltic flows and dykes which are thought to be part of the Kerguelen plume activities; these include the ca. 118-103 Ma Rajmahal tholeiite basaltic (RTB) flows (e.g., Kent et al., 2002; Coffin et al., 2002) and the ca. 118-109 Ma NNW- to WNW-trending dolerite dykes (see Fig. 1 and Table 1; Srivastava, 2022; Srivastava et al., 2023). Here we present a detailed discussion on all the available ⁴⁰Ar/³⁹Ar geochronological and geochemical data on the ca. 118-109 Ma NNW- to WNW-trending dolerite dykes to decipher their genetic aspects and connection with the Kerguelen mantle plume and, by inference, the Greater Kerguelen LIP.

Geology of the CNGT

The CNGT is considered to be part of the Singhbhum craton; separated from the Singhbhum Granite Complex (SGC) by the Singhbhum Mobile Belt (SMB) (e.g., Naqvi and Rogers, 1987; Sharma, 2009; Srivastava et al., 2009, 2012, 2014, 2020; see Fig. 1a). The major part of the CNGT comprises Precambrian basement rocks (granite gneisses, migmatites, porphyritic granite and metasedimentary enclaves), Gondwana sedimentary basins, Rajmahal tholeiitic basalts, and mafic dykes of different ages (e.g., Naqvi and Rogers, 1987; Mahadevan, 2002; Kent et al., 2002; Sharma, 2009; Ramakrishnan and Vaidyanadhan, 2010; Srivastava, 2020a,b, Srivastava et al., 2014, 2020 and references therein). There is debate over nature of the CNGT as many thought that it is a Proterozoic mobile belt (e.g., Mukhopadhyay, 1988; Mahadevan, 2002; Ghose and Chatterjee, 2008), and others considered that it was a mobile belt that cratonized by the end of Archean (e.g., Naqvi and Rogers, 1987; Kumar and Ahmad, 2007; Sharma, 2009; Srivastava et al., 2009, 2012, 2020). Based on various lines of geological evidence, which include the presence of komatiite magmatism (Bhattacharya et al., 2010), Cretaceous potassic intrusions (Srivastava et al., 2009; Chalapathi Rao et al., 2014; Srivastava, 2020a), Mesoproterozoic to Cretaceous mafic dykes (Kumar and Ahmad, 2007; Srivastava et al., 2012, 2014, 2020, 2023, Srivastava, 2022), and post-Archean ENE– to E–trending intra-continental rift/shear zones (e.g., Ghose and Chatterjee, 2008), the present authors also believed that the CNGT is an Archean block whose convergence with the Singhbhum craton in the south gave rise to the Singhbhum mobile belt and medium-grade enclaves of meta-sediments and basic rocks.

Mafic dykes of different ages, ranging from Mesoproterzoic (Kumar and Ahmad, 2007; Srivastava et al., 2012) to Late Cretaceous (Srivastava et al., 2014, 2020, 2023), are emplaced within the CNGT (Fig. 1c). The Mesoproterozoic mafic dykes mostly trend in ENE to E and intruded the Precambrian basement gneisses, whereas Early Cretaceous dolerite dykes intrude the Gondwana sedimentary rocks as well as Precambrian basement rocks and trend NNW to WNW (Kent et al., 2002; Srivastava et al., 2014, 2020; 2023). On the other hand, a set of Late Cretaceous (ca. 70-65 Ma) dolerite dykes, which mostly trend in NNE to NE, intrude only the Gondwana sedimentary rocks (cf. Kent et al., 2002; Srivastava et al., 2014). The Early Cretaceous (ca. 118-109 Ma) NNW- to WNW-trending dolerite dykes, identified as the Raniganj-Koderma swarm (Srivastava et al., 2023) are well exposed in and around the Raniganj, Giridih and Koderma regions (Fig. 1c). Although dolerite dykes encountered around the Raniganj region and intrude the Gondwana sedimentary rocks, including coal beds. However an NNW-trending dolerite dyke (>50 km long; identified as the Salma dyke) extends into the Precambrian basement rocks as well. In contrast, dolerite dykes in the Giridih and Koderma areas intrude only Precambrian basement rocks.

A number of studied Early Cretaceous dolerite dykes are traced in length from a kilometre to tens of kilometres (Fig. 1c); the longest one is >50 km long Salma dyke (Kent et al., 2002; Paul, 2005). Srivastava et al. (2023) have named some individual longer dykes; these are – the >20 km long NW-trending Paharpur dyke exposed in the Koderma area, the >15 km long NW-trending Gurha dyke encountered from the Giridih area, the >5 km long WNW-trending Gadikalan exposed in the Koderma area, and the ~5 km long N-S trending Raghunathchak dykes encountered from the Raniganj area. The Raghunathchak dyke is reported to cut the NNW-trending Salma dyke near Raghunathchak, indicating its younger emplacement age. Mostly these dykes are medium- to coarse-grained and possess ophitic/sub-ophitic textures and chiefly consist of subhedral grains of augite/titan augite and plagioclase (An_80-65); ilmenite (up to 10 vol%), orthopyroxene and a few grains of rutile and apatite are present as accessory phases.

Results

⁴⁰Ar/³⁹Ar Dating

Total seven dykes from the Raniganj-Koderma swarm were dated with ⁴⁰Ar/³⁹Ar method (see Table 1; Kent et al., 2002; Srivastava et al., 2020, 2023). Kent et al. (2002) have dated two dolerite dyke samples, one from the Koderma area that yielded plateau date of 115.3 ± 0.4 Ma and other from the Kalidaspur area which yielded plateau date of 112.5 ± 0.5 Ma. Later, Srivastava et al. (2020) dated a dyke sample from the Chinchuria area, a part of the Salma dyke, which yielded plateau date of 116.0 ± 1.4 Ma. Recently, Srivastava et al. (2023) dated four samples from the Raniganj-Koderma swarm; these include (i) a dolerite sample from the WNW-trending Gadikalan dyke, Koderma which yielded plateau date of 118.3 ± 1.3 Ma, (ii) a dolerite sample from the Koderma area collected from the NW-trending Paharpur dyke which yielded a plateau date of 110.9 ± 1.5 Ma, (iii) a dolerite sample from the NW-trending Gurha dyke which yielded a plateau date of 111.8 ± 1.5 Ma, and (iv) a dolerite sample from the N-S dolerite dyke that cuts the NNW-trending Salma dyke near Raghunathchak, in the Raniganj area and which yielded a plateau date of 109.0 ± 1.9 Ma.

Geochemistry

Available geochemical data on dolerite dykes of the Raniganj-Koderma swarm (Srivastava et al., 2014, 2020, 2023); are examined to evaluate their geochemical characteristics. Their sub-alkaline tholeiitic basaltic andesite nature is observed for all the samples (Fig. 2a; Le Maitre, 2002), which is further substantiated on the Jensen’s cation plot where most samples plot in the high-Mg tholeiitic field (Fig. 2b; Jensen, 1976).

Selected high-field strength elements (HFSEs) are examined for their variation against MgO (see Fig. 3). All plotted HFSE increase with increasing MgO contents following a normal trend of crystallization. It is observed that apart from Y and Yb all other HFSEs variation diagrams dyke samples plot in two distinct groups, each having their own course of crystallization. Also, a group of dyke samples (mostly from the dykes in the Raniganj area) have higher contents of HFSEs than the other group (dykes in the Giridih and Koderma areas) with overlapping MgO contents. Similar results are observed on variation of HFSEs (Ti, P, Y, and Nd) plotted with respect to Zr contents (Fig. 4). All the HFSEs have positive correlation and each of the two groups follow its own distinct crystallization path.

⁴⁰Ar/³⁹Ar ages of the dated samples (filled circles) are marked for more clear picture. The correlation between geochemical and age suggest that the WNW- and NNW-trending ca. 118-116 Ma dyke samples have different geochemical characteristics and follow distinct crystallization path from the NW-trending ca. 112-111 Ma dyke samples. Interestingly, the N-S trending ca. 109 Ma dyke sample shows similar chemistry to the ca. 118-116 Ma dyke samples.

On the primordial mantle normalized multi-element (ME) and chondrite normalized rare-earth element (REE) patterns all the studied samples show elemental compositions which are more enriched than primordial mantle and chondrite values (Fig. 5). In general, all samples show noticeable negative Nb-Ta, Th and positive Ba, Sr anomalies on ME diagrams (Fig. 5a-c). A very small negative Ti and no significant anomaly in Zr-Hf is noticed in all samples as well.

The ca. 118-116 Ma (Fig. 5a) and ca. 109 Ma (Fig. 5c) dyke samples have a smaller Nb-Ta trough than the ca. 112-111 Ma samples (Fig. 5b). Also two former groups of samples show a wider variation in the Rb and Sr than the third, youngest group. Inclined REE trends (Fig. 5d-f), (light-REE (LREE) enriched relative to heavy-REE (HREE)) is noticed for all the studied samples, however, the ca. 118-116 Ma and ca. 109 Ma samples show slightly enriched middle REE (MREE) abundances (Fig. 5d, f), which is not observed in the ca. 112-111 Ma samples (Fig. 5e).

Pearce et al. (2021) have used immobile element proxies to characterize LIPs and understand the petrogenetic processes involved. They suggested a LIP printing diagram based on the Th/Nb – Ti/Yb ratio variations in LIP samples (Fig. 6c) that essentially combines the two earlier projections, i.e., Th/Yb – Nb/Yb (Fig. 6a; Pearce, 2008) and TiO₂/Yb – Nb/Yb (Fig. 6b; Pearce, 2008), in order to distinguish different geochemical types of LIPs. All the studied dolerite dyke samples plot close to the Type IIIab array that defines the MORB-OPB-OIB – SZLM characteristics; however, they plot closer to MORB-OPB-OIB rather than to SZLM (see Fig. 6c). The Kerguelen plume derived basalts, which are supposed to be part of the Greater Kerguelen LIP (e.g., Yang et al., 1998; Doucet et al., 2002; Frey et al., 2002), are also shown on this plot (see Fig. 6c); the studied samples show close similarities with these basalts.

Discussion

⁴⁰Ar/³⁹Ar ages and Geochemistry

All the available ⁴⁰Ar/³⁹Ar dates are precise and considered as emplacement ages for the dolerite dykes of the Raniganj-Koderma swarm. The observed ages range from ca. 118 Ma to ca. 109 Ma, and suggest emplacement of dolerite dykes in three pulses (ca. 118-116 Ma, ca. 112-111 Ma, and ca. 109 Ma). The Early Cretaceous Rajmahal tholeiitic basaltic flows are also emplaced during ca. 118-103 Ma (see Table 1) in the CNGT and are thought to be contemporaneous with the Raniganj-Koderma swarm. Based on geochemical characters, the studied Early Cretaceous dolerite dykes (Raniganj-Koderma swarm) are classified into three distinct groups, i.e., ca. 118-116 Ma, ca. 112-111 Ma, and ca. 109 Ma. The ca. 118-116 Ma group consists of ca. 116 Ma Raniganj dolerite dykes and the ca. 118 Ma Gadikalan dyke (of the Koderma area) and they follow the same Geochemical Trend 1 and are considered to represent one pulse with trend WNW-NNW. The other group comprises samples from the ca. 112-111 Ma (mostly from the Giridih and Koderma areas), which follow Geochemical Trend 2 and are considered to represent a second pulse with trend NW. The third group represented by the ca. 109 Ma Raghunathchak dyke, which follows the Geochemical Trend 1, but since it was emplaced later then it is considered as a third pulse with trend N-S (see Fig. 4 for more details).

Most of the studied samples show negative Nb-Ta and positive Sr anomalies (Fig. 5a-c) which indicate a limited role of interaction with crustal components. However, no sample shows any Zr anomaly, and this observation does not support any role of crustal components as crustally contaminated samples should have positive anomalies. Furthermore, crustally contaminated samples should also show enriched LREE and flat HREE patterns (cf. Cullers and Graf, 1984; Hirschmann et al., 1998). However, all the studied samples show inclined REE patterns (Fig. 5d-f), which support crystallization of a rock from a low-percentage partial mantle melt, rather than from any crustal contamination (cf. Cullers and Graf, 1984; Fram and Lesher, 1993; Hirschmann et al., 1998).

Critical trace-element ratios (Th/Yb, Nb/Yb, TiO₂/Yb, and Th/Nb,) are also tested to examine a possible role for contamination by crustal components. The low Th/Yb ratio is not consistent with any significant contribution of crustal components, either through crustal contamination or addition of crustal components from metasomatized lithospheric mantle (cf. Pearce, 2008; Pearce et al., 2021). On the Th/Yb vs Nb/Yb ratios plot (Fig. 6a), the studied samples show closer match with OIB – E-MORB rather than N-MORB. This plot can be used to evaluate the possible role of contamination by crustal components, whether by crustal contamination in crustal magma chambers (e.g., Pearce, 2008; Neumann et al., 2011), and/or by interaction by asthenospheric/plume melts with lithosphere previously metasomatized during a prior subduction event (e.g., Cai et al., 2010; Ernst, 2014; Pearce et al., 2021). Furthermore, on the Nb/Yb – TiO₂/Yb ratio plot (Fig. 6b), studied samples shows an identical nature and plot at the transition of OIB and MORB arrays and indicate involvement of plume-ridge interaction in their genesis. All these characteristics clearly support an association with hotspot or plume and with at most only minor addition of crustal components (e.g., Schilling, 1973; Pearce et al., 2021).

Linkage to the Greater Kerguelen Mantle Plume and Large Igneous Province

The incompatible trace element geochemical characteristics of the Early Cretaceous Raniganj-Koderma dolerite dyke swarm from the CNGT clearly suggest their emplacement in an intraplate setting and association with a mantle plume; they show OIB – E-MORB nature rather than N-MORB.

The Greater Kerguelen LIP covers a huge area consisting of the Eastern Tibetan Tethyan Himalaya, Eastern Indian Lesser Himalaya, Western Australia, Eastern Indian Ocean, Shillong Plateau (NE India), Chota Nagpur Gneissic Terrane (Eastern India), southern Kerguelen Plateau, and north-eastern Antarctica (cf. Zhu et al., 2009; Whittaker et al., 2016; Olierook et al., 2019; Srivastava, 2020, 2022 and references therein). All these magmatic rocks are supposed to be connected to the Kerguelen plume, spanning from ca. 145 Ma and continued until the present day at the Kerguelen Archipelago and Central Kerguelen Plateau in the Indian Ocean (cf. Weis et al., 2002; Patrick and Smellie, 2013; Duncan et al., 2016; Bredow and Steinberger, 2018). Largely, these magmatic activities (of the Kerguelen plume head stage) belong to two major phases – (i) between ca. 145 and 130 Ma, and (ii) between ca. 124 and 100 Ma (cf. Srivastava, 2022; see Table 2). The third phase (plume tail) is between ca. 100 Ma and present day (e.g., Coffin et al., 2002; Duncan, 2002; Bredow and Steinberger, 2018). These three phases of magmatic activities of the Kerguelen plume are further supported by the three distinct parts of the Kerguelen hotspot track (Doubrovine et al., 2012).

The ca. 118-109 Ma Raniganj-Koderma dolerite dyke swarm of the present study belongs to the second major phase (ca. 124 and 100 Ma; Srivastava, 2022). Figure 7 shows comparison of geochemical characteristics of the studied dykes with other second phase magmas and also with other Kerguelen plume derived basaltic rocks, including the Kerguelen plateau basalts (including Naturaliste plateau and Bunbury basalts; Salters et al., 1992; Mahoney et al., 1995; Frey et al., 1996), Rajmahal Group I and Group II tholeiitic basalts (Storey et al., 1992), and earlier studied Early Cretaceous low-Ti dolerite dykes (Srivastava et al., 2014). All the studied dykes of Raniganj-Koderma swarm show a good match with these Kerguelen plume related basaltic rocks. This supports their genetic connection with the Greater Kerguelen plume / LIP and in particular the second plume head stage. More specifically, their transitional nature between OIB and MORB fields with participation of plume-ridge interaction in their genesis is also noticed (Fig. 8c), which indicate only minor contribution of crustal components through interaction with metasomatized lithosphere.

The Greater Kerguelen Mantle Plume and Break-up of East Gondwana

As stated in earlier section, two distinct mega events (rifting?), related to the Greater Kerguelen mantle plume have been identified; one starts ca. 145 Ma and ends ca. 130 Ma and the other begins ca. 124 Ma and was completed ca. 100 Ma. These events played a significant role in the break-up of East Gondwana (cf. Shi et al., 2018). Based on report of ca. 147 Ma andesitic flows in the Kada area in the Eastern Tethyan Himalaya (ETH), which shows plume component, it is suggested that the Kerguelen mantle plume arrived in the region at this time (cf. Shi et al., 2018). However, the major emplacement of earliest basaltic volcanism and dykes were observed during ca. 145–140 Ma in the south-eastern Tibet region (e.g., Zhu et al., 2008; Liu et al., 2015; Huang et al., 2019; Tian et al., 2019; Zeng et al., 2019; Bian et al., 2019). This was followed by ca. 137–135 Ma (OIB)-type basaltic magmatism in the entire ETH (e.g., Bian et al., 2019; Huang et al., 2019; Tian et al., 2019; Zhu et al., 2008 and references therein); these have isotopic compositions similar to the Kerguelen Archipelago (e.g., Shi et al., 2018; Tian et al., 2019; Zhou et al., 2018; Zhu et al., 2008, 2009).

It is believed that during the period between ca. 145 and 135 Ma, the Kerguelen plume head was likely to have been located below northern Greater India (i.e., beneath the ETH and ELH; e.g., Doubrovine et al., 2012; Gibbons et al., 2013; Watson et al., 2016; Whittaker et al., 2013). This is well supported by geochemical signature of magmatic rocks of this region that show plume component in their genesis (Bian et al., 2019; Huang et al., 2019; Singh et al., 2020, 2021; Tian et al., 2019; Zhu et al., 2008 and references therein). This was followed by several magmatic activities recorded during ca. 137–127 Ma in the ETH (e.g., Zhu et al., 2009; Liu et al., 2015; Wei et al., 2017; Wang et al., 2018; Zhou et al., 2018; Bian et al., 2019; Tian et al., 2019), ELS (Singh et al., 2020, 2021), Bunbury (e.g., Coffin et al., 2002; Olierook et al., 2016, 2019), and EIO (e.g., Direen et al., 2017; Olierook et al., 2017). These magmatic activities are likely to indicate break-up of East Gondwana ca. 137 Ma that initiated the separation of Western Australia from Greater India (see Fig. 8a). However, no such magmatic record of this period is known from the Shillong Plateau, CGC, Eastern Antarctica, and Kerguelen Plateau suggesting they were remained united at that time.

The next phase of magmatic activities, i.e., ca. 124–122 Ma, marked separation of Antarctica from Eastern India (Fig. 5b), which was followed by a number of mafic and alkaline (carbonatite) magmatism in the Shillong Plateau (e.g., Coffin et al., 2002; Heaman et al., 2002; Ray et al., 2005; Srivastava et al., 2005, 2019), CNGT (e.g., Baksi, 1995; Coffin et al., 2002; Ghatak and Basu, 2013; Kent et al., 2002; Srivastava, et al., 2020, 2023), Eastern Antarctica (e.g., Coffin et al., 2002; Yaxley et al., 2013), and the Kerguelen Plateau (e.g., Coffin et al., 2002; Duncan, 2002; Ingle et al., 2002) during ca. 119-110 Ma (Fig. 5c).

Conclusions

• Available ⁴⁰Ar/³⁹Ar plateau dates of dolerite dyke samples from the Early Cretaceous N- to WNW-trending Raniganj-Koderma swarm, Chhota Nagpur Gneissic Terrane clearly suggest their emplacement during ca. 118-109 Ma.
• ⁴⁰Ar/³⁹Ar dates and geochemistry of the studied dolerite dyke samples suggest their emplacement at least in three pulses: Pulse 1 – WNW- and NNW-trending ca. 118-116 Ma dykes following geochemical Trend 1; Pulse 2 – NW-trending ca. 112-111 Ma dykes following geochemical Trend 2; and Pulse 3 – N-S trending ca. 109 Ma dykes with geochemical Trend 1.
• Geochemically the studied dyke samples show a close match with the MORB–OIB-OPB array suggesting their mantle nature. The characteristic geochemical nature suggests close similarities with the Type IIIab LIP array on the LIP fingerprinting classification (Pearce et al., 2021).
• The ca. 118-109 Ma Raniganj-Koderma dolerite dyke swarm of the present study belongs to the second plume head phase of the Greater Kerguelen mantle plume / LIP.
• The spatial and temporal distribution of Early Cretaceous (ca. 145– 100 Ma) magmatic rocks exposed within the continental blocks associated to East Gondwana are likely to be connected, directly or indirectly, with the Kerguelen mantle plume and suggest their LIP nature. Their crucial role in the break-up of East Gondwana is also emphasized.

Acknowledgements

RKS thanks the Science and Engineering Research Board (SERB) for financial support through a research project (no. EMR/2016/000169). Authors thanks the head of the Department of Geology, Banaras Hindu University and the Director, State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, for extending all necessary facilities required during this work.

References