The 2018 Hochstetter Lecturer is Emeritus Professor Alan Cooper.
His talk is entitled “Tectonics of the Haast Schists”.
Date: Tuesday, 22 May 2018
Venue: Elim Christian Centre, 625 Main Rd, Stoke, Nelson
Time: 7.30 – 9.00
Gold coin donation please
The Haast Schist of New Zealand, composed predominantly of Otago, Alpine and Marlborough Schist components, is the most deeply buried and strongly metamorphosed part of a broadly eastward younging accretionary complex developed on the subduction margin of Gondwana. The Torlesse Composite terrane protoliths that grade into schist range in age from Carboniferous to Triassic. They were multiply deformed and metamorphosed in the Jurassic. However, extensive areas of Alpine Schist in the west, in part overlying a metamorphosed ophiolitic sequence, and rich in metabasite and metachert, have been shown to have anomalous detrital zircon ages, as young as ~108 Ma. This deposition occurred approximately synchronous with both the cessation of westward-directed subduction in the Eastern Province of New Zealand, and localised covering of the erosion surface in the now contiguous Otago Schist to the east by extensional terrestrial and volcanoclastic sediments. These Mid Cretaceous schist protoliths are interpreted to form the exotic Pounamu terrane accreted and interfolded with the Otago Schist on the western margin of Southeast Zealandia. The accompanying metamorphism on the tectonic margin between SE and NW Zealandia microplates is dated from zircon overgrowths on detrital grains at 69 Ma (although over an extended period, 64 to 98 Ma, regionally). The Haast Schist is therefore a polygenetic unit formed from the two-sided amalgamation of polyphase metamorphic components.
Alan Cooper bibliographic notes:
Educated in Burton-on-Trent and Sheffield, England, I came out to New Zealand in 1966 as a Teaching Fellow to undertake a PhD in the Geology Department, University of Otago, supervised by Professor Douglas Coombs. My thesis area was the Haast River, south Westland where I investigated the structure and progressive metamorphism of greenschists and amphibolites in the Alpine Schist. In 1970, I was appointed to the position of Lecturer at the University of Otago, retiring in 2012 after 46 years service.
I continue to do research work in the Southern Alps, investigating amongst other things, a lamprophyre-carbonatite dyke swarm intruding the schist (first documented by Julius von Haast), the Pounamu Ultramafics and correlative rocks, marine terrace remnants and uplifted Holocene sedimentary sequences, mapping of the Alpine Fault, anatectic pegmatites, and more recently ages of detrital zircons within the Alpine Schists. The lamprophyre–carbonatite interest has taken me to experimental work on carbonate minerals in Toronto, Canada, and mapping of carbonatites in Antarctica, Namibia and Turkey. I have had eight field seasons in Antarctica mainly supervising students, investigating the basement geology of the Transantarctic Mountains and more recently the Neogene to Recent alkaline volcanic rocks of the Erebus Province of the McMurdo Volcanics.