Whole-rock and mineral chemistry of cumulates from the Kizildag (Hatay) ophiolite (Turkey): clues for multiple magma generation during crustal accretion in the southern Neotethyan ocean


Bagci U., Parlak O., Hock V.

MINERALOGICAL MAGAZINE, cilt.69, ss.53-76, 2005 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 69 Konu: 1
  • Basım Tarihi: 2005
  • Doi Numarası: 10.1180/0026461056910234
  • Dergi Adı: MINERALOGICAL MAGAZINE
  • Sayfa Sayısı: ss.53-76

Özet

The late Cretaceous Kizildag ophiolite forms one of the best exposures of oceanic lithospheric remnants of southern Neotethys to the north of the Arabian promontory in Turkey. The ultramafic to mafic cumulate rocks, displaying variable thickness (ranging from 165 to 700 m), are ductiley deformed, possibly in response to syn-magmatic extension during sea-floor spreading and characterized by wehrlite, olivine gabbro, olivine gabbronorite and gabbro. The gabbroic cumulates have an intrusive contact with the wehrlitic cumulates in some places. The crystallization order of the cumulus and intercumulus phases is olivine (Fo(86-77)) +/- chromian spinel, clinopyroxene (Mg#(92-76)), Plagioclase(An(95-83)), orthopyroxene(Mg#(87-79)). The olivine, clinopyroxene, orthopyroxene and plagioclase in ultramafic and mafic cumulate rocks seem to have similar compositional range. This suggests that these rocks cannot represent a simple crystal line of descent. Instead the overlapping ranges in mineral compositions in different rock types suggest multiple magma generation during crustal accretion for the Kizildag ophiolite. The presence of high Mg# of olivine, clinopyroxene, orthopyroxene, and the absence of Ca-rich plagioclase as an early fractionating phase co-precipitating with forsteritic olivine, suggest that the Kizildag plutonic suite is not likely to have originated in a mid-ocean ridge environment. Instead the whole-rock and mineral chemistry of the cumulates indicates their derivation from an island are tholeiitic (IAT) magma. All the evidence indicates that the Kizildag ophiolite formed along a slow-spreading centre in a fore-arc region of a suprasubduction zone tectonic setting.