4.2 Article

Reactive harzburgite and ultimate dunite formation as a result of boninite-like melt interaction: Petrological evidence from the Kirdag ophiolite (Erzurum, NE Turkey)

Journal

JOURNAL OF AFRICAN EARTH SCIENCES
Volume 193, Issue -, Pages -

Publisher

PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jafrearsci.2022.104601

Keywords

Harzburgite; Dunite; Melt interaction; Kirdag ophiolite; Eastern Pontide; Turkey

Funding

  1. Ataturk University Scientific Research Projects Coordination Unit [FBA-2018-6828]

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This study examines the harzburgite-dunite suite in the Kirdag ophiolite in Turkey and provides evidence for mantle processes and geotectonic implications. The textural, mineral and whole-rock geochemical properties reveal melting and melt-peridotite interaction processes, as well as the origin of the suite from a depleted mantle with high-degree partial melting. The study also suggests the occurrence of reaction between boninitic melt and harzburgite in the supra-subduction zone.
In this study, the harzburgite-dunite suite in the mantle section of the Kirdag ophiolite outcropping in the east of the Eastern Pontides (Erzurum, North-eastern Turkey) was examined in textural, mineral and whole-rock geochemical terms to interpret the mantle processes. Besides textural occurrences such as inclusions and exsolution lamellae, mineral and whole-rock geochemical properties provided clear evidence of melting and melt-peridotite interaction processes during harzburgite-dunite generation. The Fo-numbers of olivines and the Cr-numbers of spinels generally increased from the harzburgites to the dunites. In addition, the clinopyroxenes found only in the reactive harzburgite (Cr-number; up to 0.61) displayed depleted characteristics indicated high-degree partial melting and melt-rock interaction processes. The Cr-number, Mg-number, Fe3+-number, Al2O3 and TiO(2 )contents of the chromian spinels suggest that the harzburgite-dunite suite originated from depleted mantle with high-degree partial melting. The Fe3+ cation values of the chromian spinels were significantly higher in the dunites, suggests the alteration effects in oxidizing conditions. Also, the positive correlation between the Cr-numbers and TiO2 contents of the chromian spinels observed in the dunites show that the reaction between boninitic melt and harzburgite occurred in the supra-subduction zone. Although there is evidence from whole-rock major and trace element contents of the studied peridotite samples, some mobile elements were re-stabilized by serpentinization, and the general changes in these elements reflect the extensive characteristic features of mantle-derived peridotites. Considering the data as a whole, it can be said that the textural features, chemical diversity of the major minerals, and whole rock geochemical properties of this harzburgite-dunite assemblage are good examples for the interpretation of petrological processes and geotectonic implications in supra-subduction zones (SSZ).

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