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Physico-chemical parameters of Neoarchean syntectonic magmatism: The example of the Muscocho Pluton, Abitibi Subprovince

Mathieu Lucie, Madon Baptiste et Hamilton Michael A.. (2020). Physico-chemical parameters of Neoarchean syntectonic magmatism: The example of the Muscocho Pluton, Abitibi Subprovince. Ore Geology Reviews, 125, p. 103670.

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URL officielle: http://dx.doi.org/doi:10.1016/j.oregeorev.2020.103...

Résumé

The Muscocho Pluton is one of a number of syntectonic Neoarchean granodiorite intrusions formed during the main deformation phase in the Abitibi Subprovince that lead to stabilization of the Superior craton. Such magma locally are associated with magmatic-hydrothermal styles of mineralization, interpreted by some works to reflect intrusion-related gold systems (IRGS). Determining whether magmas can transport enough Au to fertilize the upper crust during this tectonomagmatic interval requires insights into physico-chemical parameters such as pressure, temperature, and oxygen fugacity (ƒO2). The ƒO2 parameter is particularly important because it affects S-speciation and S-solubility, which correlates with Au-solubility in magmas. Retrieving such parameters from the metamorphosed, locally hydrothermally altered, and generally deformed Neoarchean rocks is particularly challenging. As such, this contribution uses fresh to altered granodiorites of the Muscocho Pluton, a 16 km diameter granodiorite intrusion spatially associated with polymetallic mineralization, to evaluate whether physico-chemical parameters can be retrieved from ancient altered rocks based on amphibole, apatite, and zircon chemistry. This study also has implications for the origins of the Muscocho Pluton, which ascended slowly toward the upper crust as a single pulse of evolved magma and became emplaced at about 12 km depth. The magma had an ƒO2 above the Ni/NiO solid oxygen buffer (NNO + 1), which is not considered optimal for Au transportation. The magma also formed a deep intrusion unable to provide magmatic fluids to trigger an efficient hydrothermal system. This study provides the basis for a systematic evaluation of the physico-chemical conditions within which syntectonic magmas evolved in the upper crust. Knowledge of these physico-chemical conditions are necessary to better constrain the IRGS metallogenic model.

Type de document:Article publié dans une revue avec comité d'évaluation
Volume:125
Pages:p. 103670
Version évaluée par les pairs:Oui
Date:Octobre 2020
Sujets:Sciences naturelles et génie > Génie
Sciences naturelles et génie > Sciences appliquées
Sciences naturelles et génie > Sciences naturelles > Sciences de la terre (géologie, géographie)
Département, module, service et unité de recherche:Départements et modules > Département des sciences appliquées > Unité d'enseignement en sciences de la Terre
Mots-clés:Muscocho Pluton, granodiorite; Abitibi Subprovince, syntectonic magmatism, physico-chemical parameters, intrusion-related gold systems (IRGS), Sous-province de l'Abitibi, magmatisme syntectonique, paramètres physico-chimiques, systèmes aurifères liés aux intrusions (IRGS)
Déposé le:05 févr. 2021 00:28
Dernière modification:05 févr. 2021 00:28
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