Magma genesis at Andaman volcanic arc regime, Northeastern Indian Ocean: Role of slab-mantle interaction

Saha, Abhishek; Mudholkar, Abhay; Raju, and K.A. Kamesh

doi:10.18814/epiiugs/2020/020019

Cited by 4 publications

(2 citation statements)

References 34 publications

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“…The bulk rock geochemical analysis of 18 samples of the Andaman Ophiolite from the South Andaman is presented in Table 1. Sea region of previous studies Bandyopadhyay et al, 2020;Bhattacharya et al, 2013;Ghosh et al, 2014;Jafri et al, 1990;Jafri et al, 2010;Jafri & Sheikh, 2013;Pal, 2011;Pal et al, 2007;Pedersen et al, 2010;Ray et al, 1988;Sachin et al, 2017;Saha et al, 2020;Srivastava et al, 2004) = 57-63 wt% may be either due to the data gap or what is known as the Daly Gap (Daly, 1925). It can be a subject of investigation in future studies.…”

Section: Geochemical Resultsmentioning

confidence: 93%

Role of fractional crystallization and partial melting in the generation of intermediate and acidic magmas of the Andaman Island Ophiolite suite of India

2021

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The Mesozoic-age Andaman Island Ophiolite located in the southeastern fringe of the Indian plate margin is one of the well-preserved supra-subduction-zone oceanic lithospheric slices. It is tectonically associated with the Indonesian arc system and is an extension of the Phanerozoic Indonesian-Myanmar orogenic belt. Thus, it offers a unique opportunity to study oceanic crust formation and specify magma evolution processes in the Tethyan subduction system. The volcanics of the Andaman Islands ophiolite display a wide compositional variation. Rock types vary from basic (basalts) to intermediate (basaltic-trachyandesites, basaltic andesites) to acidic differentiates like dacites and rhyolites. This contribution presents the petrochemistry of the intermediate rock types-basaltic-trachyandesites, trachyandesites and acidic-dacites and rhyodacites of Andaman Island Ophiolite (India). This study examines the role of fractional crystallization and partial melting in the generation of intermediate and acidic magmas of the Andaman Ophiolite suite. Plagioclases and pyroxenes are the major mineral constituents of these rocks on petrographic observation. Plagioclases of the intermediate rocks are of albite composition Ab 98-99. The acidic rocks show compositional variation from albite to oligoclase (Ab 83-99 ). Analysed pyroxenes of intermediate and acidic rocks are augite (Wo 46-49 En 34-41 Fs 13-17 ) . The studied calcalkaline rocks show variable abundance of Large-Ion Lithophile Elements and display strong positive Pb and negative Ti anomalies. The chondrite-normalized Rare Earth Elements display an enriched pattern with varying degrees of enrichment. Clinopyroxene thermobarometry reveals that the intermediate magma and acidic magma becomes saturated with clinopyroxene at 1,062-1,133 C and 1,016-1,079 C, respectively, at 2 kbar and H 2 O = 2 wt%. Petrochemical findings and model calculations using PELE are consistent with a derivation of intermediate rocks from the basaltic melt by fractional crystallization. In contrast, acidic rocks are the product of partial melting of hydrothermally altered oceanic crust. The association of basaltic and intermediate rocks suggests a relatively stable magma chamber to generate differentiated intermediate magmas by fractional crystallization.

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Section: Geochemical Resultsmentioning

confidence: 93%

Role of fractional crystallization and partial melting in the generation of intermediate and acidic magmas of the Andaman Island Ophiolite suite of India

2021

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“…Previous morphological and geochemical studies of the seabed samples of cratered seamount in this region suggest that the seamount has erupted in the recent (past few hundred years) geological past 23 . Rocks from the off Nicobar volcanic arc have shown geochemical characteristics conforming to calc-alkaline melts derived from lower oceanic crust 60 . The occurrence of the hydro-acoustic phase associated with hybrid VLPEs from off Nicobar submarine volcanoes suggests subsurface magma migration from deeper to shallow depths.…”

Section: Discussionmentioning

confidence: 99%

Sub-surface magma movement inferred from low-frequency seismic events in the off-Nicobar region, Andaman Sea

Aswini

Dewangan

Raju

et al. 2020

Sci Rep

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Monitoring volcanic activity along the submarine volcanoes that are usually induced by subsurface magmatism is a challenge. We present fresh set of Ocean Bottom Seismometer (OBS) data that shows geophysical evidence indicative of subsurface magmatism along the submarine volcanoes in the off Nicobar region, Andaman Sea. In this region, we observed for the first time, hybrid very long-period earthquakes documented by passive OBS experiment. These events were initiated by high-frequency (5–10 Hz) with a clear onset of P-phase followed by low-frequency (0.01–0.5 Hz) oscillations in the range of 300–600 s with a prominent high-frequency (10–40 Hz) hydro-acoustic phase. A total of 141 high-frequency events were detected on 21st and 22nd March 2014 out of which 71 were of low-frequency oscillations. These events are distributed in the northwest–southeast direction along the submarine volcanic arc and Seulimeum strand of Great Sumatra fault. Off Nicobar region has been witnessing frequent earthquake swarms since 26th December 2004 tsunamigenic Sumatra earthquake. These swarms occurred in January 2005, March and October 2014, November 2015 and March 2019. The occurrence of low-frequency earthquakes and prominent hydro-acoustic phase are suggestive of sub-surface tectonic and magmatic influence. We propose that upward movement of magma pulses from deeper magma reservoir to the shallow magma chamber activated the strike-slip movement of sliver faults and induced earthquake swarms in the off Nicobar region.

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Gas migration signatures over the volcanic cratered seamount, off the Nicobar Islands in the Andaman Sea

Sriram,

Dewangan,

Yatheesh

et al. 2023

Geo-Mar Lett

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Magma genesis at Andaman volcanic arc regime, Northeastern Indian Ocean: Role of slab-mantle interaction

Cited by 4 publications

References 34 publications

Role of fractional crystallization and partial melting in the generation of intermediate and acidic magmas of the Andaman Island Ophiolite suite of India

Role of fractional crystallization and partial melting in the generation of intermediate and acidic magmas of the Andaman Island Ophiolite suite of India

Sub-surface magma movement inferred from low-frequency seismic events in the off-Nicobar region, Andaman Sea

Gas migration signatures over the volcanic cratered seamount, off the Nicobar Islands in the Andaman Sea

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