Formation of lower fast-spread oceanic crust: a structural and geochemical study of troctolites in the Hess Deep Rift (East Pacific Rise) - Université de Montpellier Accéder directement au contenu
Article Dans Une Revue Progress in Earth and Planetary Science Année : 2023

Formation of lower fast-spread oceanic crust: a structural and geochemical study of troctolites in the Hess Deep Rift (East Pacific Rise)

Résumé

Abstract Troctolites were recovered during Integrated Ocean Drilling Program Expedition 345 at the Hess Deep Rift, next to fast-spreading East Pacific Rise. These troctolites are divided into three groups based on textural differences: coarse-grained (1–10 mm in length) troctolite, fine-grained (~ 2 mm in length) troctolite, and skeletal olivine-bearing troctolite. All troctolites exhibit a magmatic fabric. The major-element compositions of olivine, plagioclase, and clinopyroxene in the troctolites are intermediate between those of Hess Deep gabbros and harzburgites. The trace-element compositions of olivine, plagioclase, and clinopyroxene in the troctolites overlap with those of troctolites from slow-spread crust, but they record no petrographic evidence indicating assimilation of mantle peridotite. Thermodynamic calculation for mineral chemistry showed that fractional crystallization of melt is the dominant process responsible for the formation of the troctolites. The fine-grained troctolite was crystallized with high crystallization rate resulting from hot melt injection into colder wall gabbro. In contrast, interactions between the unsolidified troctolite containing interstitial melt and newly injected melt resulted in the formation of the skeletal olivine-bearing troctolite. While our results demonstrate that the troctolites exhibit multiple melt injections and partial dissolution of a troctolite precursor, fractional crystallization is the dominant process for the creation of the lower crust in the Hess Deep Rift.
Fichier principal
Vignette du fichier
Akizawa_PEPS_2023.pdf (5.68 Mo) Télécharger le fichier
Origine Fichiers éditeurs autorisés sur une archive ouverte
Licence

Dates et versions

hal-04152064 , version 1 (05-07-2023)

Licence

Identifiants

Citer

Norikatsu Akizawa, Marguerite Godard, Benoît Ildefonse, Shoji Arai. Formation of lower fast-spread oceanic crust: a structural and geochemical study of troctolites in the Hess Deep Rift (East Pacific Rise). Progress in Earth and Planetary Science, 2023, 10, pp.30. ⟨10.1186/s40645-023-00560-4⟩. ⟨hal-04152064⟩
4 Consultations
13 Téléchargements

Altmetric

Partager

Gmail Mastodon Facebook X LinkedIn More