Focussed hydrothermal alteration in upper crustal oceanic faults on Macquarie Island ...

• Main Author: Lewis, SJ
• Format: Thesis
• Language: unknown
• Published: University Of Tasmania 2023
• Subjects: Pacific; Southern Ocean; Macquarie Island
• Online Access: https://dx.doi.org/10.25959/23231171; https://figshare.utas.edu.au/articles/thesis/Focussed_hydrothermal_alteration_in_upper_crustal_oceanic_faults_on_Macquarie_Island/23231171

Macquarie Island is an uplifted exposure of oceanic lithosphere lying deep within the Southern Ocean, less than ten kilometres east of the dextral transpressional boundary which separates the Indo-Australian and Pacific plates (54° 30' S, 158° 55' E). The island is a geological oddity; essentially an intra-oceanic ophiolite residing in its primary marine basin. Macquarie Island hosts a diverse spectrum of igneous rock types from all stratigraphic levels of the ocean crust, with pillow basalts and sheeted dolerite dykes most abundant. These upper crustal rocks were formed in the Late Miocene during slow crustal accretion and rifting (spreading rate ~ 20 mm per year) at the relict Proto-Macquarie Spreading Ridge (PMSR). Typical of many slow-spreading (magma-poor) mid-ocean ridges, tectonic activity played a dominant but episodic role in the geological evolution of Macquarie Island. Faults, fractures, and brittle shear zones are widespread across the island, and discrete igneous rock domains commonly ...