Subduction versus non‐subduction origin of <scp>the Nagaland‐Manipur</scp> Ophiolites along the <scp>Indo‐Myanmar</scp> Orogenic Belt, northeast India: Fact and fallacy

Khogenkumar, Shoraisam; Singh, Alka; Kumar, Santosh; Lakhan, Nongmaithem; Chaubey, Monika; Imtisunep, Sashimeren; Dutt, Amrita; Oinam, Govind

doi:10.1002/gj.4030

Cited by 24 publications

(31 citation statements)

References 65 publications

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“…This REE pattern is comparable to the average abyssal peridotite trend afterMoghadam et al (2010) and also falls within the published abyssal peridotite field of spinel lherzolites from NMOC(Khogenkumar et al, 2021;Singh, 2013) (Figure6a). In multielement spidergram plots, spinel lherzolite rocks show enrichment in large-ion F I G U R E 6 Chondrite-normalized rare earth element plot and primitive mantle-normalized spidergram of spinel lherzolite (a, b), dunite (c, d), harzburgite (e, f), and websterite (g, h) samples.…”

supporting

confidence: 87%

“…Sample locations of the studied rocks with their sample numbers are plotted on the map for reference pillow basalts, plagiogranites, cumulate gabbro, and a suite of variously serpentinized ultramafic association of dunite, harzburgite, lherzolite, and pyroxenites (Acharyya, Roy, & Mitra, 1986;Ghose & Singh, 1980;Sengupta, Ray, Acharyya, & De Smith, 1990;Venkataramana, Dutta, & Acharyya, 1986). In the NMOC, the abyssal peridotites and cumulates are represented by spinel lherzolites (Ao et al, 2020;Ghosh et al, 2018;Khogenkumar et al, 2021;Singh, 2013;Singh, Nayak, et al, 2017;Venkataramana et al, 1986), harzburgites (Ghosh et al, 2018;Singh, 2009Singh, , 2013Singh, Nayak, et al, 2017), serpentinites (Ningthoujam et al, 2012), dunites (Khogenkumar et al, 2021), and websterites (Singh, Nayak, et al, 2017). Some of these abyssal peridotites have been subsequently modified by interaction with a hybridized mantle-wedge melts as they got accreted to the overlying mantle wedge during subduction initiation (Ao et al, 2020).…”

Section: Geological Settingmentioning

confidence: 99%

“…Whereas the overlying mantle, also known as the SSZ peridotites and cumulate section, are represented by more refractory serpentinites (Ovung et al, 2017), harzburgite (Kingson et al, 2017), lherzolite (Kingson et al, 2017;Verencar et al, 2021), websterite (Abdullah et al, 2018;Verencar et al, 2021), and dunites (Abdullah et al, 2018) together with chromitite pods (Pal et al, 2014) association. These rocks also show records of interaction with a melt of boninitic-tholeiitic affinity above the subduction zone (Khogenkumar et al, 2021;Pal et al, 2014;Verencar et al, 2021). The age of the ophiolites is variously assigned at Upper Jurassic age based on a study from the radiolarians and whole-rock K-Ar ages of basalts (Baxter, Aitchison, Zyabrev, & Ali, 2011;Sarkar et al, 1996) and an Early Cretaceous age based on U/Pb zircon ages of plagiogranites (Aitchison et al, 2019;Singh, Chung, Bikramaditya, & Lee, 2017).…”

Section: Geological Settingmentioning

confidence: 99%

“…Thus, the geochemical study of mantle peridotites from ophiolite complexes can provide important information on their tectonic origin and melt-mantle interaction in an SSZ setting. Mantle peridotites from the NMOC show geochemical signatures that indicate their formation in both MOR settings (Ao, Bhowmik, & Upadhyay, 2020;Ghosh et al, 2018;Khogenkumar et al, 2021;Ningthoujam, Dubey, Guillot, Fagio, & Shukla, 2012;Singh, 2009Singh, , 2013Singh, Nayak, et al, 2017) and SSZ setting (Abdullah, Misra, & Ghosh, 2018;Kingson, Bhutani, Dash, Sebastian, & Balakrishnan, 2017;Ovung et al, 2017;Pal et al, 2014;Verencar, Saha, Ganguly, & Manikyamba, 2021). However, the detailed geochemical study of mantle peridotites from the northern margin of the NMOC, that falls within the northern tip of the Nagaland Ophiolite Complex (NOC) is lacking at present.…”

mentioning

confidence: 99%

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Petrogenesis of mantle peridotite and cumulate peridotite rocks from the Nagaland Ophiolite Complex, NE India

Satyanarayanan

2021

Geological Journal

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Here, we report new geochemical data from mantle peridotite (spinel lherzolite, dunite, and harzburgite) and cumulate peridotite (websterite) rocks from the northernmost portion of the Nagaland Ophiolite Complex. Based on detailed textural, mineral (major element) chemistry, and whole-rock (major and trace element) chemistry, we reveal the origin of these rocks in different tectonic settings and their modification via the melt-mantle interaction process. The spinel lherzolite rocks with low Cr# (0.16-0.25) chrome spinel are mantle residues formed after low degrees ($10-15%) of partial melting in a mid-oceanic ridge setting, which has been subsequently modified in a subduction zone setting. However, the dunites and harzburgite samples are interpreted to be depleted mantle residue formed in a supra-subduction zone (SSZ) setting. Additionally, the dunites are inferred to be of replacive origin representing former harzburgites. Based on Cr# of chrome spinel, the dunites are classified into low Cr# (0.53-0.57), medium Cr# (0.73-0.79), and high Cr# (0.89-0.90) dunites. High Cr# dunite with low-TiO 2 (0.01-0.06 wt%) possibly formed by interaction with a boninitic melt, whereas low-medium Cr# dunite with high TiO 2 (0.14-0.34 wt%) formed by interaction with a high-Ti melt in an SSZ setting. Harzburgite samples with their highly resorbed orthopyroxene grain boundaries contain chrome spinels (Cr# = 0.84-0.88; TiO 2 = 0.00-0.06 wt%) similar to the high Cr# dunite samples and are also interpreted to be formed by interaction with a boninitic melt. The websterite samples with their low Mg# (0.79) olivine and low Ni (345-413 ppm) content are interpreted to be of cumulate origin formed in an SSZ setting. However, the interstitial chrome spinel blebs with low Mg# (0.18-0.19), high Cr# (0.60-0.61), Fe 3+ (0.20-0.21), and very high TiO 2 (2.03-2.04 wt%) are interpreted to be a result of post-cumulus interaction of interstitial chrome spinel with high-Ti intercumulus melt.These mantle peridotites and cumulates of different tectonic origins were obducted and juxtaposed during the final stages of the India-Asia collision.

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supporting

confidence: 87%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

mentioning

confidence: 99%

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Petrogenesis of mantle peridotite and cumulate peridotite rocks from the Nagaland Ophiolite Complex, NE India

Satyanarayanan

2021

Geological Journal

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“…The Tuting-Tidding Suture Zone (TTSZ) ophiolite exposures in the eastern Himalaya, on the eastern flank of the eastern Himalayan syntaxis, are considered the extension of the ITSZ ophiolites (Choudhuri et al, 2009;Dutt, Singh, Srivastava, Oinam, & Bikramaditya, 2021;Gururajan & Choudhuri, 2003 Singh, 2011). The suture zone further extends south to the Indo-Myanmar Orogenic Belt and the Andaman-Nicobar Island Arc (Khogenkumar et al, 2016(Khogenkumar et al, , 2021Singh, 2013;Singh et al, , 2016Singh, Chung, Bikramaditya, & Lee, 2017;Singh, Khogenkumar, Kumar, Singh, & Thakur, 2021).…”

Section: Geology Of the Areamentioning

confidence: 99%

New constraints on the tectono‐magmatic evolution of the Tidding‐Mayodia ophiolites, eastern Himalaya, northeast India

et al. 2021

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The Tidding‐Mayodia ophiolites (TMO) exposed along the Lohit and Dibang river valleys in eastern Himalaya that have been considered as the extension of the Indus‐Tsangpo Suture Zone ophiolites are revisited to review their petrogenetic‐tectonic origin. The ophiolites consist of depleted harzburgite and dunite with lesser amounts of mafic rocks (gabbro intrusives, mafic dykes) and carbonates. The serpentinized peridotites consist of antigorite, lizardite, olivine, Cr‐spinel, and bastite with minor sulfide minerals. From SEM‐EDS studies, sulfide minerals were observed to be associated mainly with magnetites. The main sulfide mineral is pentlandite with minor millerite that exists as inclusions inside the pentlandite grains. Elemental mapping of these sulfides shows that they are mainly Ni‐(Co‐)‐bearing sulfides. The olivines are highly forsteritic (Fo = 95–96) while the Cr‐spinels show distinct Cr‐magnetite rims with a chromite core (Cr# = ~93). The serpentinized peridotites have whole‐rock compositions of SiO2 <47 wt% and high MgO (>36.37 wt%) and low Al2O3 (<1.21 wt%), CaO (<0.82 wt%), indicating the depleted nature of the parent rocks. Highly fractionated LREEs as compared to HREEs [(La/Yb)N = 2.62–13.22], and REE and Cr spinel chemistry modelling suggests that the studied peridotites have formed from ~22% partial melting of a depleted spinel lherzolite source which later underwent interactions with a high‐temperature silicate melt that caused enrichment in LREE and Cr of spinels. The parental melt compositions of Cr spinel yield their formation during arc tectonism (Al2O3melt = 6.28–7.65 wt%, FeO/MgO = 1.00–1.33). Furthermore, Mn and Zn concentrations in spinels, the occurrence of Cr magnetite rim in Cr‐spinels, presence of secondary olivine with higher Fo (~98), and occurrence of low‐temperature re‐equilibrated sulfide minerals, indicate that the rocks were subject to low‐temperature metamorphism. Based on this evidence, combined with data from previous studies, a tectonic model has been proposed for the genesis of the studied ophiolites. This model shows that the ophiolites have formed from the entrapment of depleted N‐MORB mantle in the mantle wedge of an intra‐oceanic subduction zone. During the nascent forearc regime, this mantle wedge underwent interactions with high‐temperature melts, which caused changes in their chemistry. Moreover, the rocks underwent interactions with low‐temperature fluids in the mature forearc, which caused the formation of sulfides and metamorphozed these rocks.

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Significance of aegirine‐bearing metabasic rocks in the metamorphic evolution of the Nagaland Accretionary Prism, northeast India

et al. 2021

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The ophiolite belt of Nagaland–Manipur states in Northeast India represents a segment of the ocean floor and upper mantle following eastward convergence of the Indian Plate with the Myanmar (Burmese) microplate during the Mesozoic. A variety of high‐pressure metamorphic assemblages have been noted in the metabasics and metacherts from the Phanerozoic ophiolite belt in the central part of the Naga Hills, which constitute the Nagaland Accretionary Prism. The metabasics are represented by very low‐grade assemblages of zeolite, prehnite‐pumpellyite, greenschists, and high‐pressure glaucophane schist and eclogite. We report the occurrence of aegirine‐bearing metabasic rocks, previously not recorded in the region. The metabasics are strongly fractionated and show chemical affinity with low‐K oceanic tholeiite. They are derived from a basic protolith of depleted mantle composition (viz. MORB). Pseudosection modelling reveals that aegirine formed at P–T conditions of c. 1.15 GPa and 490°C in the basic protolith in blueschist facies conditions. Similar P–T conditions have been reported from nearby localities, either as part of retrograde conditions or due to post‐peak cooling changes in the different metamorphic assemblages. However, the P–T observed from our study does not follow the cooling or retrograde path of the reported metabasics. Therefore, we suggest that the aegirine‐bearing metabasics might have formed at an earlier stage in the nascent forearc when temperatures were elevated enough to cause dehydration of the subducting slab to generate Na‐rich fluid fluxes at ambient pressures.

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Subduction versus non‐subduction origin of the Nagaland‐Manipur Ophiolites along the Indo‐Myanmar Orogenic Belt, northeast India: Fact and fallacy

Cited by 24 publications

References 65 publications

Petrogenesis of mantle peridotite and cumulate peridotite rocks from the Nagaland Ophiolite Complex, NE India

Petrogenesis of mantle peridotite and cumulate peridotite rocks from the Nagaland Ophiolite Complex, NE India

New constraints on the tectono‐magmatic evolution of the Tidding‐Mayodia ophiolites, eastern Himalaya, northeast India

Significance of aegirine‐bearing metabasic rocks in the metamorphic evolution of the Nagaland Accretionary Prism, northeast India

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