The Effects of Amphibole- and Sulfide-Producing Melts on Crustal Strength in Gabbros of Lower Oceanic Crust in Oceanic Core Complexes, Mid-Atlantic and Southwest Indian Ridges
type: CreativeWork
description: This study investigates gabbro-cored oceanic core complexes in the slow-spreading Mid-Atlantic Ridge (MAR) and the ultraslow spreading Southwest Indian Ridge (SWIR). Dikelets are a texture found in thin section samples from these systems that form as a result of crystal-plastic deformation. Thin section samples from the Atlantis Massif, MARK Area, and 13˚-15˚ North of the MAR and the Atlantis Bank of the SWIR were observed with petrography to find these dikelets and identify what type of dikelet is present. SEM-EDS is used to identify the mineral assemblages present in the dikelets. LA-ICP-MS is used on amphibole to determine if its origin is igneous or metamorphic. The temperature of formation was calculated for amphibole and estimated for sulfides. Ferro-hornblende is the dominant amphibole observed in dikelets from the MAR. Pyrite is the common Fe sulfide found in dikelets, while chalcopyrite was the Cu-Fe sulfide found in sulfide-rich dikelets, although its presence was quite rare. Temperature calculations for amphibole suggested that amphibole shown is a secondary amphibole (metamorphic), while temperature estimations for sulfides suggest that they formed from a late-stage melt. Trace element data shows both igneous and metamorphic amphibole are observed in Atlantis Massif.
abstract: This study investigates gabbro-cored oceanic core complexes in the slow-spreading Mid-Atlantic Ridge (MAR) and the ultraslow spreading Southwest Indian Ridge (SWIR). Dikelets are a texture found in thin section samples from these systems that form as a result of crystal-plastic deformation. Thin section samples from the Atlantis Massif, MARK Area, and 13˚-15˚ North of the MAR and the Atlantis Bank of the SWIR were observed with petrography to find these dikelets and identify what type of dikelet is present. SEM-EDS is used to identify the mineral assemblages present in the dikelets. LA-ICP-MS is used on amphibole to determine if its origin is igneous or metamorphic. The temperature of formation was calculated for amphibole and estimated for sulfides. Ferro-hornblende is the dominant amphibole observed in dikelets from the MAR. Pyrite is the common Fe sulfide found in dikelets, while chalcopyrite was the Cu-Fe sulfide found in sulfide-rich dikelets, although its presence was quite rare. Temperature calculations for amphibole suggested that amphibole shown is a secondary amphibole (metamorphic), while temperature estimations for sulfides suggest that they formed from a late-stage melt. Trace element data shows both igneous and metamorphic amphibole are observed in Atlantis Massif.
author: Hoffmann, Trevor
keywords: Amphibole, sulfide, dikelet, oceanic core complexes, mid-ocean ridges, oceanic lithosphere, Geochemistry, Geology
date published: 2024-05-01T07:00:00Z
date modified: 2026-07-24T05:45:47Z
provider: University of Southern Mississippi
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Southern Mississippi