In the Cheshmeh-Bid district of the Khajeh-Jamali ophiolitic massifs (Southern Iran), mantle peridotites are intruded by abundant pyroxenite dykes. A few of these dykes are remarkable for the occurrence of native copper associated with the development of a metasomatic reaction zone. The dykes are progressively reacted, from their margins towards the center, with an amphibole + antigorite selvage, followed by a centimeter-thick clinopyroxene + antigorite assemblage and, finally, by the native copper-bearing zone consisting of clinopyroxene + chlorite + antigorite. Native Cu occurs along cleavages and partially healed fractures in clinopyroxene, and as massive grains intergrown with antigorite. Copper isotope signatures and thermodynamic calculations show that the main driver for reaction zone formation is Ca-metasomatism. Native copper forms at the expense of chalcocite in the reaction zone. Such a reaction can only occur in reducing conditions, in agreement with the analysis of fluid inclusions composition displaying H2 and CH4. Such fluids presumably originated from the hydration of mantle rocks. The observed reaction zone and native copper mineralization are thus interpreted as the result of Ca-metasomatism during hydrothermal alteration of the oceanic lithosphere. This is consistent with U/Pb dating of titanite, suggesting formation during the Albian when the dykes were exposed on the seafloor in a supra-subduction setting. The source for copper mineralization, as revealed by Cu isotopes, is probably mantle-like.

Eslami, A., Malvoisin, B., Grieco, G., Aradi, L., Marchesi, C., Cavallo, A., et al. (2021). Native copper formation associated with serpentinization in the Cheshmeh-Bid ophiolite massif (Southern Iran). LITHOS, 382-383(February 2021) [10.1016/j.lithos.2020.105953].

Native copper formation associated with serpentinization in the Cheshmeh-Bid ophiolite massif (Southern Iran)

Cavallo, Alessandro;
2021

Abstract

In the Cheshmeh-Bid district of the Khajeh-Jamali ophiolitic massifs (Southern Iran), mantle peridotites are intruded by abundant pyroxenite dykes. A few of these dykes are remarkable for the occurrence of native copper associated with the development of a metasomatic reaction zone. The dykes are progressively reacted, from their margins towards the center, with an amphibole + antigorite selvage, followed by a centimeter-thick clinopyroxene + antigorite assemblage and, finally, by the native copper-bearing zone consisting of clinopyroxene + chlorite + antigorite. Native Cu occurs along cleavages and partially healed fractures in clinopyroxene, and as massive grains intergrown with antigorite. Copper isotope signatures and thermodynamic calculations show that the main driver for reaction zone formation is Ca-metasomatism. Native copper forms at the expense of chalcocite in the reaction zone. Such a reaction can only occur in reducing conditions, in agreement with the analysis of fluid inclusions composition displaying H2 and CH4. Such fluids presumably originated from the hydration of mantle rocks. The observed reaction zone and native copper mineralization are thus interpreted as the result of Ca-metasomatism during hydrothermal alteration of the oceanic lithosphere. This is consistent with U/Pb dating of titanite, suggesting formation during the Albian when the dykes were exposed on the seafloor in a supra-subduction setting. The source for copper mineralization, as revealed by Cu isotopes, is probably mantle-like.
Articolo in rivista - Articolo scientifico
Ca-metasomatism; Cheshmeh-Bid ophiolitic massif; Iran; Native copper; Pyroxenite; Serpentinization;
English
27-dic-2020
2021
382-383
February 2021
105935
open
Eslami, A., Malvoisin, B., Grieco, G., Aradi, L., Marchesi, C., Cavallo, A., et al. (2021). Native copper formation associated with serpentinization in the Cheshmeh-Bid ophiolite massif (Southern Iran). LITHOS, 382-383(February 2021) [10.1016/j.lithos.2020.105953].
File in questo prodotto:
File Dimensione Formato  
Lithos_Native copper_2020_pre-print-MR.pdf

accesso aperto

Tipologia di allegato: Submitted Version (Pre-print)
Dimensione 2.26 MB
Formato Adobe PDF
2.26 MB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/298004
Citazioni
  • Scopus 0
  • ???jsp.display-item.citation.isi??? 0
Social impact