A record of metasomatism and crustal contamination of the Mediterranean lithosphere in chromitites of the Orhaneli Ophiolite Complex (NW Turkiye)
Por:
Akbulut, Mehmet, Gonzalez-Jimenez, Jose Maria, Belousova, Elena, Gines, Vanessa Colas, de Pablo, Julia Farre, Sola, Nuria Pujol, Proenza, Joaquin A.
Publicada:
15 sep 2022
Resumen:
This study provides the first-ever report of U-Pb isotopic ages of
zircon and rutile from high-Cr chromitites of the Orhaneli Ophiolite
Complex (OOC). The chromites within the OOC chromitites yield Cr-numbers
between 0.77 and 0.86, Mg-numbers between 0.46 and 0.71 and TiO2 < 0.26
wt%. They exhibit V, Ga and Ni depletion and Sc, Ti, Zn, Co and Mn
enrichment relative to MORB spinels, with significant Sc and Ti positive
anomalies. This, and the Al(2)O(3 )and TiO2 compositions of the parental
melts, suggest that the studied chromitites formed from island arc melts
of boninitic affinity, in a supra-subduction environment. In addition to
zircons, chromites host other solid mineral inclusions, including Os-and
Ir-dominant platinum-group minerals (PGM), base-metal sulfides (BMS),
alloys, ubiquitous silicate (some as micron-sized oriented lamellae),
and two poorly defined Fe-Cr-O and Ti-Si-C grains. The zircons show Th/U
ratios typical for magmatic zircons from felsic melts, and present
Middle Devonian to Mesoproterozoic U-Pb isotopic ages. Although the
reworked/resorbed forms of the zircons suggest a xenocrystic origin,
coupling of U-Pb data from some zircons and rutile with the Ti positive
anomaly in the chromites raises the possibility for an earlier
Neoproterozoic metasomatic event affecting the relics now included
within the chromitite bands. The current state of knowledge about the
silicate micro-lamellae within the chromites has prompted reassessment
of their early interpretation as direct evidence of deep mantle
recycling. We currently suggest a more cautious approach on this issue
by seeking additional evidences for an ultrahigh pressure (UHP) history.
Filiaciones:
Akbulut, Mehmet:
Dokuz Eylul Univ, Dept Geol Engn, Tinaztepe Campus,Buca, TR-35390 Izmir, Turkey
Macquarie Univ, Australian Res Council Ctr Excellence Core Crust F, Dept Earth & Planetary Sci, Sydney, NSW 2109, Australia
Gonzalez-Jimenez, Jose Maria:
Consejo Super Invest Cient CS UGR, Inst Andaluz Ciencias Tierra, Armilla, Granada, Spain
Belousova, Elena:
Macquarie Univ, Australian Res Council Ctr Excellence Core Crust F, Dept Earth & Planetary Sci, Sydney, NSW 2109, Australia
Geol Survey Queensland, Dept Resources, Brisbane, Qld 4000, Australia
Gines, Vanessa Colas:
Univ Nacl Autonoma Mexico, Inst Geol, Mexico City, Mexico
de Pablo, Julia Farre:
Univ Barcelona, Dept Mineral Petrol Geol & Aplicada, Barcelona, Spain
Sola, Nuria Pujol:
Univ Barcelona, Dept Mineral Petrol Geol & Aplicada, Barcelona, Spain
Proenza, Joaquin A.:
Univ Barcelona, Dept Mineral Petrol Geol & Aplicada, Barcelona, Spain
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