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

Belgrano, Thomas M.; Diamond, Larryn W.

doi:10.1130/l1045.1

Cited by 27 publications

(34 citation statements)

References 73 publications

(194 reference statements)

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“…Though the Semail magmatic history can be broadly split into two magmatic phases (Phase 1 and 2; Goodenough et al, 2014), geochemical indicators of subduction-zone input gradually increase upwards through the volcanic stratigraphy. (A'Shaikh et al, 2005;Alabaster et al, 1982;Belgrano and Diamond, 2019;Ernewein et al, 1988;Godard et al, 2003;Kusano et al, 2012Kusano et al, , 2014Kusano et al, , 2017Lippard et al, 1986;Umino et al, 1990).…”

Section: Geology and Petrogenesis Of The Semail Upper Crustal Unitsmentioning

confidence: 99%

“…Semail ophiolite volcanostratigraphy with capping pelagic sediments (Suhaylah Fm.) and Sheeted Dyke Complex (SDC), revised according to field observations in this study after Alabaster et al, (1982), Gilgen et al, (2014) and Belgrano and Diamond (2019).…”

Section: Geology and Petrogenesis Of The Semail Upper Crustal Unitsmentioning

confidence: 99%

“…A growing body of geochemical and geochronological evidence indicates that the crustal sequences of many Tethyan ophiolites-including the Oman-U.A.E. (Semail) example-formed in response to upper-plate extension during the initiation of lower-plate subduction (Belgrano and Diamond, 2019;Dilek et al, 2007;Dilek and Furnes, 2009;Guilmette et al, 2018;Ishikawa et al, 2002;MacLeod et al, 2013;Metcalf and Shervais, 2008;Rollinson, 2009;Rollinson and Adetunji, 2015;Shafaii Moghadam et al, 2013). These findings have led to reinterpretation of many ophiolites as counterparts to difficult-toaccess records of subduction initiation preserved in submarine fore-arcs and rear-arc basement (Stern et al, 2012;Stern and Bloomer, 1992;Whattam and Stern, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Four regionally-extensive, mappable volcanic units have been recognised in the Semail ophiolite (Geotimes, Lasail, Alley and Boninitic Alley), with an increasingly-pronounced subduction influence recorded by each successively erupted unit (Alabaster et al, 1982;Belgrano and Diamond, 2019;Gilgen et al, 2014;Ishikawa et al, 2002;Kusano et al, 2012Kusano et al, , 2014Kusano et al, , 2017). However, as previous regional mapping was carried out prior to the recognition of boninites, and the Lasail unit was either lumped in with Geotimes (e.g., BME, 1987aBME, , 1987bUmino et al, 1990), or Alley (e.g., BRGM, 1993a), these existing regional maps distinguish only two units: the early (V1) and late (V2) extrusives.…”

Section: Introductionmentioning

confidence: 99%

“…the ophiolite's boninites facilitates exploration for the gold-bearing volcanogenic massive sulphide (VMS) ore deposits hosted by these lavas (Gilgen et al, 2014). Finally, a map perspective of the Semail upper crust provides an areally extensive and well-studied comparison to drilled sections from the Izu-Bonin-Mariana (IBM) proto-arc basement (Belgrano and Diamond, 2019;Ishikawa et al, 2002;MacLeod et al, 2013;Pearce et al, 1992;Reagan et al, 2013Reagan et al, , 2017Shervais et al, 2018;Stern et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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A revised map of volcanic units in the Oman ophiolite: insights into the architecture of an oceanic proto-arc volcanic sequence

Belgrano¹,

Diamond²,

Vogt³

et al. 2019

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Abstract. Recent studies have revealed genetic similarities between Tethyan ophiolites and oceanic proto-arc sequences formed above nascent subduction zones. The Semail ophiolite (Oman–U.A.E.) in particular can be viewed as an analogue for this proto-arc crust. Though proto-arc magmatism and the mechanisms of subduction-initiation are of great interest, insight is difficult to gain from drilling and limited surface outcrops in submarine fore-arcs. In contrast, the Semail ophiolite, in which the 3–5 km thick upper-crustal succession is exposed in an oblique cross-section, presents an opportunity to assess the architecture and volumes of different volcanic rocks that form during the protoarc stage. To determine the distribution of the volcanic rocks and to aid exploration for the volcanogenic massive sulphide (VMS) deposits that they host, we have re-mapped the volcanic units of the Semail ophiolite by integrating new field observations, geochemical analyses and geophysical interpretations with pre-existing geological maps. By linking the major element compositions of the volcanic units to rock magnetic properties, we were able to use aeromagnetic data to infer the extension of each outcropping unit below sedimentary cover, resulting in in a new map showing 2100 km2 of upper-crustal bedrock. Whereas earlier maps distinguished two main volcanostratigraphic units, we have distinguished four, recording the progression from early spreading-axis basalts (Geotimes) through to axial to off-axial depleted basalts (Lasail), to post-axial tholeiites (Tholeiitic Alley) and finally boninites (Boninitic Alley). Geotimes (Phase 1) axial dykes and lavas make up ~55 vol% of the Semail upper crust, whereas post-axial (Phase 2) lavas constitute the remaining ~ 45 vol % and ubiquitously cover the underlying axial crust. The Semail boninites occur as discontinuous accumulations up to 2 km thick at the top of the sequence and constitute ~ 15 vol % of the upper crust. The new map provides a basis for targeted exploration of the gold-bearing VMS deposits hosted by these boninites. The thickest boninite accumulations occur in the Fizh block, where magma ascent occurred along crustal-scale faults that are connected to shear zones in the underlying mantle rocks, which in turn are associated with economic chromitite deposits. Locating major boninite feeder zones may thus be an indirect means to explore for chromitites in the underlying mantle.

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