Timing of Formation and Obduction of the Andaman Ophiolite

Bhattacharya, Saurav; Pande, Kanchan; Kumar, Alok; Kingson, Oinam; Ray, Jyotisankar

doi:10.1007/978-3-030-39843-9_2

Cited by 4 publications

(4 citation statements)

References 47 publications

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“…Our two plateau ages of 106.4 ± 2.1 and 105.3 ± 1.6 Ma obtained for the metamorphic sole are certainly older than the age of previously interpreted ophiolititc crust formation based on the available ages of 93-98 Ma (Bhattacharya et al, 2020;Pedersen et al, 2010;Sarma et al, 2010). The cooling ages of the metamorphic sole obtained by the Ar/Ar method are systematically coeval with the crystallization ages of the ophiolite (e.g., Oman, Hacker, 1994;Turkey, see review in van Hinsbergen et al, 2016;Greece, Dimo-Lahite et al, 2001;Liati et al, 2004).…”

Section: Implication Of the Sole Age: Estimating The Duration Of Flipcontrasting

confidence: 45%

“…The Andaman ophiolites are arguably the most complete in the sense that ultramafic and mafic sequences are present (Ghosh et al, 2014(Ghosh et al, , 2017Pal, 2011;Pal et al, 2003), although as described above, these may not, or not entirely, be cogenetic (i.e. gabbro intruding plagiogranite; Bhattacharya et al, 2020). Metamorphic rocks were described from the serpentinite-hosted subophiolitic mélange and were suggested to reflect parts of a dismembered metamorphic sole (Pal & Bhattacharya, 2010), but their precise metamorphic conditions, or the age of formation and/or cooling, are so far unconstrained.…”

Section: Regional Setting Of the Andaman-nicobar Islandsmentioning

confidence: 99%

“…Magmatic rocks in the sequence include in places plagiogranites (trondhjemites) and are overlain by Upper Cretaceous (Campanian) radiolarian cherts (Ling et al, 1996). Whole rock Sm/Nd ages on different component of the ophiolite (basalt, plagiogranite and peridotite) yielded a 98±8.2 Ma isochron (Bhattacharya et al, 2020). Two trondhjemites samples gave zircon U/Pb ages of of 93.6±1.3 Ma (Sarma et al, 2010) and 95±2Ma (Pedersen et al, 2010) that were interpreted to represent the formation of Andaman ophiolite crust above a subduction zone.…”

Section: Introductionmentioning

confidence: 99%

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History of Subduction Polarity Reversal During Arc‐Continent Collision: Constraints From the Andaman Ophiolite and its Metamorphic Sole

et al. 2020

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Subduction polarity reversal during arc-continent collision has been proposed as a key mechanism to initiate new subduction zones. Despite often interpreted, well-exposed geological record that document the reversal is sparse. The ophiolitic lithounits of the Andaman and Nicobar Islands have been proposed to have formed during the initiation of a new subduction zone following the collision of the Woyla Arc of Sumatra with Sundaland (Eurasia). We here present new field, petrological and geochronological data to evaluate the timing of the initiation of Andaman subduction. We targeted the previously inferred but unstudied metamorphic sole of the Andaman ophiolites that witnessed juvenile subduction. Thermodynamic modeling reveals that the exposed amphibolites of the sole formed at around 0.9 GPa and 675°C. We dated two samples of the metamorphic sole using the Ar/Ar method on amphibole, giving cooling ages of 106.4 ± 2.1 and 105.3 ± 1.6 Ma. This is similar to published ages from plagioclase xenocrysts in recent Barren Island volcanics and in zircons from a gabbro sample from the Andaman ophiolite, which we interpret as the age of the original ophiolite formation. The Ar/Ar ages are considerably older than arc magmatic gabbros and plagiogranites of the overlying ophiolite previously dated at 99-93 Ma and thought to reflect the ophiolite age but recently reinterpreted as a volcanic arc built on the ophiolite. Combined with the ages of Woyla-Sundaland collision, we argue that subduction polarity reversal occurred in a transient period of perhaps some 10 Myr, similar to recent settings.

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Section: Implication Of the Sole Age: Estimating The Duration Of Flipcontrasting

confidence: 45%

Section: Regional Setting Of the Andaman-nicobar Islandsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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History of Subduction Polarity Reversal During Arc‐Continent Collision: Constraints From the Andaman Ophiolite and its Metamorphic Sole

et al. 2020

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“…The BoB is the largest deep-sea fan in terms of sedimentary volume and receives a large amount of sediment flux derived from the Himalayan river system (G-B river system and Irrawaddy River) and small rivers from the Indian continent (i.e., the Mahanadi, Godavari, and Krishna Rivers). Subduction along this zone likely started at approximately 98 Ma (Bhattacharya et al, 2020). The BoB was formed during the collision of the Indian subcontinent with the southern margin of Asia.…”

Section: The Bay Of Bengalmentioning

confidence: 99%