Contribution of slab-derived fluid and sedimentary melt in the incipient arc magmas with development of the paleo-arc in the Oman Ophiolite

Kusano, Yuki; Umino, Susumu; Shinjo, Ryuichi; Ikei, Anzu; Adachi, Yoshiko; Miyashita, Sumio; Arai, Shoji

doi:10.1016/j.chemgeo.2016.12.012

Cited by 31 publications

(76 citation statements)

References 58 publications

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“…8A). In comparison to the "less-depleted V1" primary melt composition calculated by Kusano et al (2017), which has a Th-Nb depleted, SW Indian MORB-like character (Fig. 8B), the majority of Geotimes analyses from the Ashar and Hawarim sections are enriched in Th and light rare-earth elements over Nb.…”

Section: Subduction Fingerprintsmentioning

confidence: 82%

“…This Th enrichment is sufficient for Th N /La N ratios to be at or above unity. In comparison to the "depleted V1" (~Lasail) primary melt composition calculated by the addition of 6 wt% olivine to a depleted V1 composition from Wadi Fizh (Kusano et al, 2017), lavas from the Lasail-like lenses have similar compositions, though are marked by higher Th/Nb ratios. One Lasail-like lens sample from Wadi Hawarim (TB3-04B) is markedly more depleted than typical Lasail lavas and is actually boninitic in terms of major elements (SiO 2 = 54 wt%, MgO = 9 wt%, TiO 2 = 0.44 wt%, V/Ti = 0.083), though these Si and Mg values may not be reliable owing to alteration.…”

Section: Subduction Fingerprintsmentioning

confidence: 94%

“…Based on modeling these trends at different water contents, MacLeod et al (2013) deduced that axial spreading was accompanied by hydrous input from a subducting slab along the length of the ophiolite. However, these deductions partly rely on elements susceptible to hydrothermal mobilization, which renders them suspect for some workers (e.g., Kusano et al, 2017), whereas others view the hydrous input as having been derived from deeply circulated seawater (e.g., Rospabé et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Subduction-zone contributions to axial volcanism in the Oman–U.A.E. ophiolite

Belgrano

Diamond

2019

Lithosphere

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Over four decades of research on the Semail ophiolite (Oman-U.A.E.) has greatly influenced our understanding of processes occurring at fast-spreading ocean ridges. While the well-developed sheeted dike complex and comagmatic lower pillow lavas indicate that the early Semail crust formed at a spreading axis, the precise tectonic setting of this axis-whether true mid-ocean ridge, back-arc or "proto"-arcis contentious. This is largely because the tectonic implications of the geochemistry of the main axial volcanic unit (Geotimes/V1) are disputed. We bypass this hurdle by focusing on intercalations of primitive lavas that are depleted relative to mid-ocean-ridge basalt and that are deeply intercalated within the early Geotimes axial volcanostratigraphy throughout the northern ophiolite. Our analyses of these intercalations show a clear trace-element influence from a subducting slab. We interpret the depleted axial melts to have formed by localized, high-degree partial melting assisted by a high-Th/Nb slab fluid. These results confirm a deep subduction influence on the entire axial spreading phase of the world's largest ophiolite. Considered in the context of later hydrous and boninitic Alley volcanism and of insight from modern tectonic environments, our observations support a proto-arc, subduction-initiation setting for the origin of the Semail ophiolite.

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Section: Subduction Fingerprintsmentioning

confidence: 82%

Section: Subduction Fingerprintsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Subduction-zone contributions to axial volcanism in the Oman–U.A.E. ophiolite

Belgrano

Diamond

2019

Lithosphere

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“…Anonymous, 1972 20-30 e.g., Umino et al, 1990;Shervais, 2001;Polat, 2008 -, 2012;Kanke andTakazawa, 2014 Umino et al, 1990;Yamasaki et al, 2006;Tsuchiya et al, 2013;Yamazaki, 2013;Kusano et al, 2014, 2017-Tatsumi et al, 2015 , 2010 1500-1600°C…”

Section: Anonymousmentioning

confidence: 99%

“…Adachi and Umino et al, 2003;Kusano et al, 2012;Umino, 2012 Maruyama andKomiya, 2011;Komiya et al, 1999, 2004Ishikawa et al, 2002, 2005Morishita et al, 2011;Tsuchiya et al, 2013;Kanke and Takazawa, 2014;Kusano et al, 2014, 2017Kaneko et al, 2007Ozawa and Takahashi, 1995Ozawa, 2001, 2005;Sano and Kimura, 2007;Fig. . Locations of ophiolites studied by Japanese researchers during the last quarter-century.…”

Section: Anonymousmentioning

confidence: 99%

An overview of world ophiolite studies by Japanese researchers

Umino

2018

Jour. Geol. Soc. Japan

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The last quarter-century has been a period of worldwide study of ophiolites by Japanese geologists, as described in this paper. The Oman Mountains expose the world largest and best preserved ophiolite that provides insights into crustal and mantle processes below a fast-spreading system and transformation of oceanic lithosphere to subarc crust and mantle. The Mirdita Ophiolite exposes mantle peridotites covered by mid-ocean ridge basalt (MORB) and arc tholeiitic to boninitic lavas, recording the transition from a spreading to a subduction environment. The Luobusa Ophiolite is well-known for its ultrahigh-pressure minerals such as coesite and micro-diamond inclusions in chromite, considered to represent recycling of subducted slab deep into the mantle at > km depth. The -Ma ophiolites in the Timor and Tanimbar Islands are the world s youngest, and are considered to have formed the forearc crust and mantle that collided with and obducted onto the northern edge of the Australian continent. Volcanic rocks have geochemical characteristics that are intermediate between arc tholeiite and MORB, although the mantle peridotites are not cognate with the overlying volcanic rocks. Another young ophiolite ( -Ma) of Taitao, southern Chile, was part of the eastern limb of the Chile Ridge, which was subducted and accreted in an accretionary complex along the western coast of Chile. In spite of their mid-ocean-ridge origin, the lavas and sheeted dikes of ophiolite have geochemical characteristics typical of arc magmas. Isua and Pilbara contain the world s oldest accretionary complexes consisting of superposed slices of oceanic crust that form a duplex structure, indicating the beginning of plate tectonics in the early Archean.

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