Origin and serpentinization of ultramafic rocks of Manipur Ophiolite Complex in the Indo-Myanmar subduction zone, Northeast India

Ningthoujam, P. S.; Dubey, C. S.; Guillot, Stéphane; Fagion, A.-S.; Shukla, Dericks Praise

doi:10.1016/j.jseaes.2012.01.004

Cited by 67 publications

(33 citation statements)

References 43 publications

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“…THE Manipur Ophiolite Belt (MOB) which is a part of the Naga-Manipur Ophiolite Belt (NMOB) has been studied by several workers [1][2][3][4][5][6][7][8][9][10][11][12] . It occurs within the NNE-SSW trending Indo-Myanmar Orogenic Belt (IMOB), a remnant of the Tethyan Ophiolite in the Alpine-Himalayan orogenic system [13][14][15][16] .…”

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confidence: 99%

“…However, the tectonic processes involved in this are still controversial. Recent studies have suggested that the peridotites of MOB are the residues remaining after low-degree partial melting of spinel-peridotite mantle at mid-oceanic ridge environment 3,[5][6][7] . The mafic volcanics are also suggested to be derived from a heterogeneous mantle source at a spreading ridge zone 12 .…”

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“…These interactions could be either positive, negative or neutral 4,5 , and may vary with space and time [5][6][7] , largely depending on ecological and historical factors which shape them. The primates mainly interact with their prey, predators, feeding competitors and neutral species, and may display a variety of behaviours towards an interacting species 5 . Most direct interactions such as aggression and submission occur when two species encounter in close proximity 8 .…”

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Mineralogy of the Manipur Ophiolite Belt, North East India:Implications for Mid-Oceanic Ridge and Supra-Subduction Zone Origin

Ovung¹,

Ray²,

Teng³

et al. 2017

Current Science

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Mineralogical studies on the mantle and crustal sections of the Manipur Ophiolite Belt (MOB) lead to important findings pertaining to its genesis and controlling tectonic milieu. The wide compositional gap in the Cr# and Mg# content of spinel in the mantle peridotites of MOB implies upper mantle melting in two different tectonic settings. The tectonic discrimination diagrams based on spinel chemistry indicate a midoceanic ridge (MOR) origin for the high-Al spinel peridotites and a supra-subduction zone origin for the high-Cr spinel peridotites. The pyroxenite mantle dyke, ultramafic cumulate and pillow-basalt record temperature in the range of 600-1030C, 600-800C and 700-1005C respectively. Plotting of clinopyroxene composition of pillow-basalt in the TiO 2 -Na 2 OSiO 2 /100 (wt%) tectonic discrimination diagram, implies a subduction-related origin of the basalts. Experimental studies on the serpentine stability indicate that it was dominantly affected by high temperaturelow deformation setting.

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Mineralogy of the Manipur Ophiolite Belt, North East India:Implications for Mid-Oceanic Ridge and Supra-Subduction Zone Origin

Ovung¹,

Ray²,

Teng³

et al. 2017

Current Science

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“…Mineral compositions in mantle peridotites are considered to be reliable petrogenetic indicators. Although a few studies of the ophiolitic mantle section of Ukhrul district (Manipur side) are available [2][3][4] , studies of its continuation onto the Myanmar side are lacking. In this study, we analysed primary silicate mineral phases within mantle rocks exposed between Tusom village, Manipur, and Shomra village, Myanmar, to elucidate their equilibrium conditions of formation and related intensive parameters.…”

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“…Olivine exhibited forsterite contents of Fo 89.7-90. 3 . MnO varied from 0.11 to 0.21 wt%, and the CaO content was low (<0.04 wt%).…”

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Silicate and Sulphide Mineralogy, and Conditions of Equilibration of Ultramafic Rocks of the Indo-Myanmar Ophiolite Belt between Tusom, Manipur and Shomra Village, Myanmar

2017

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The northeast-India ophiolite complex is exposed in many parts of Nagaland and Manipur, with particularly well-preserved mantle-sequence peridotite present in its southern section in Manipur state. We present the results of an investigation into the petrology and constituent mineral chemistry of this peridotite, which is associated with the Indo-Myanmar ophiolite located between Tusom, Ukhrul District (Manipur) and Shomra village (Myanmar). Mineral compositions indicate that it is an abyssal peridotite that has undergone minimal partial melting (1-5%). Equilibration probably occurred in the upper mantle at a temperature of 1080-1240C, a pressure of 23-24 kbar, and an oxygen fugacity between 0.303 and 0.580 log units above the FMQ buffer. Primary and secondary sulphide phases in the studied peridotites have also been analysed. Pentlandite ((Fe,Ni) 9 S 8 ) was found to be the primary sulphide mineral, which occurred in association with orthopyroxene and awaruite (Ni 3 Fe). Cu-rich alloys and magnetite occur as secondary minerals that developed during later serpentinization.Keywords: Abyssal peridotite, equilibrium temperature, pentlandite, metal alloys, oxygen fugacity, partial melting.THE compositions of phases in ophiolitic, mantle-derived ultramafic rocks depend upon the degree and pressuretemperature conditions of partial melting, and the effects of magma-rock interaction 1 . Mineral compositions in mantle peridotites are considered to be reliable petrogenetic indicators. Although a few studies of the ophiolitic mantle section of Ukhrul district (Manipur side) are available 2-4 , studies of its continuation onto the Myanmar side are lacking. In this study, we analysed primary silicate mineral phases within mantle rocks exposed between Tusom village, Manipur, and Shomra village, Myanmar, to elucidate their equilibrium conditions of formation and related intensive parameters. We also analysed metal sulphides and metallic alloys in the ultramafic rock and present an interpretation of the probable formation of these phases.The Indo-Myanmar Ophiolite belt, approximately 200 km long, extends from Nagaland in the north to Manipur in the south. It is a NNE-SSW trending, westerly convex linear belt and is mostly restricted to the eastern section of Indo-Myanmar Range. The belt has an average width of ~15 km in its northern sector (Nagaland) but gradually narrows to a width of a few metres at its southern end (Manipur). The ophiolite belt consists of lensoid bodies interbedded with Disang flyschoids, which are highly tectonized and dismembered. Despite having undergone varying degrees of serpentinization, relict primary minerals are preserved in some rocks. A traverse map showing the study area is shown in Figure 1. Majorelement compositions of mineral phases were determined by electron probe microanalysis (EPMA) using a Jeol JXA 8900 RL in wavelength dispersive mode. Silicate phases were analysed using an accelerating potential of 20 kV, a beam current of 12 nA, and a spot size of 2 m. Natural minerals and oxides (fo...

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Genesis and tectonic implications of cumulate pyroxenites and tectonite peridotites from the Nagaland–Manipur ophiolites, Northeast India: constraints from mineralogical and geochemical characteristics

et al. 2016

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The Nagaland–Manipur ophiolites (NMO) of Northeast India forms a part of the Tethyan ophiolites and comprises a suite of tectonite peridotites and cumulate mafic–ultramafic sequence with mafic extrusive–intrusive rocks, felsic intrusives and oceanic pelagic sediments along with minor podiform chromitites. However, sheeted dykes, which are considered as a significant component of ophiolites, are absent in the NMO. The tectonite peridotites are distinguished from the cumulate pyroxenites by the presence of pyroxene lineation, deformed bands and strained extinction in olivine, kink twin lamellae in pyroxene. Both the tectonite peridotites and cumulate pyroxenites contain aluminous spinel with Cr number [Cr# = Cr/(Cr + Al)] in the range of 0.14 to 0.29 and 0.27 to 0.48, respectively. Mg number [Mg# = Mg/(Mg + Fe2+)] in Cr‐spinel is higher in tectonite peridotites (0.71–0.76) than cumulate pyroxenites (0.44–0.53). Chondrite‐normalized rare earth elements (REE) patterns of cumulate pyroxenites exhibit depleted at light REEE (LREE) (LaN/SmN = 0.380–0.759) but flat middle REE (MREE) to heavy REE (HREE) (SmN/YbN = 0.622–0.756). However, the tectonite peridotites show gradual decrease in concentrations from HREE to MREE (SmN/YbN = 0.285–0.460) and slight increase in LREE (LaN/SmN = 0.721–2.201). The cumulate pyroxenites show strong enriched PPGE patterns and higher PGE concentrations (∑PGE = 85.8–163.5 ppb) compared with the tectonite peridotites (∑PGE = 34.8–113.0 ppb). The estimated equilibration temperature ranges from 890 to 931 °C for cumulate pyroxenites and 971 to 1156 °C for tectonite peridotites. The olivine–spinel equilibrium along with Cr‐spinel chemistry and PGE data suggests that the tectonite peridotites represent the residual mantle left after limited extraction of basaltic melts by low‐degree partial melting (<15%). Conversely, the presence of highly magnesian orthopyroxene and clinopyroxene in the cumulate pyroxenites in conjunction with their geothermometry suggests that they were formed at high pressure and temperature by magmatic fractionation from the basaltic melt. The geochemical data together with field and petrographical evidences indicate that both the tectonite peridotites and cumulate pyroxenites are essentially spinel‐bearing and devoid of plagioclase, suggesting their derivation in the mantle beyond the stability limit of plagioclase in a mid‐oceanic ridge tectonic setting. We conclude that the ultramafic sequence of the NMO was initially generated at a mid‐oceanic ridge tectonic setting close to the eastern boundary of the Indian passive margin and then thrust over the continental margin of the Indian Plate towards the west during its collisional and subduction process with/beneath the Myanmar Plate. Copyright © 2016 John Wiley & Sons, Ltd.

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Origin and serpentinization of ultramafic rocks of Manipur Ophiolite Complex in the Indo-Myanmar subduction zone, Northeast India

Cited by 67 publications

References 43 publications

Mineralogy of the Manipur Ophiolite Belt, North East India:Implications for Mid-Oceanic Ridge and Supra-Subduction Zone Origin

Mineralogy of the Manipur Ophiolite Belt, North East India:Implications for Mid-Oceanic Ridge and Supra-Subduction Zone Origin

Silicate and Sulphide Mineralogy, and Conditions of Equilibration of Ultramafic Rocks of the Indo-Myanmar Ophiolite Belt between Tusom, Manipur and Shomra Village, Myanmar

Genesis and tectonic implications of cumulate pyroxenites and tectonite peridotites from the Nagaland–Manipur ophiolites, Northeast India: constraints from mineralogical and geochemical characteristics

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