ENGR 470. 670.1001
James L’Angelle
University of Nevada, Reno
M. Eneva, Professor
Spring 2024
Assignment Seven: New Ireland–
Please carefully answer question 1 on p. 203 that refers to the top figure on p. 204.
From the Red X, discuss:
a.) the tectonic setting:
The most prominent tectonic feature through southern New Ireland is the Weitin Fault, a large steep-sided valley running NW-SE from the west coast through to the southeastern coast. It has been suggested (e.g. Taylor, 1979;Mori, 1989) that the Weitin Fault is a major strike-slip fault which is the extension of the BSSL. Hohnen (1978) did not find conclusive evidence of left-lateral transcurrent movement on this fault, although acknowledged that it was most likely.
(BSSL: Bismarck Sea Seismic Lineation)
The Weitin Fault has a history of seismic activity with numerous major earthquakes periodically occurring.
b.) whether the geothermal system is likely magmatic or amagmatic:
Papua New Guinea (PNG) lies within an area with a diverse and very young geological history and complex tectonic evolution that spans most of the Cenozoic (Baldwin et al., 2012). Active tectonics affecting the area include collision and thrusting, subduction and arc magmatism, rifting and backarc extension and large-scale strike-slip faulting. As a result, volcanic activity is widespread, including the rift-related volcanic domains of the Bismarck Sea/Manus Basin, the Papuan Peninsula and in the Woodlark Basin, arc volcanism along the West Bismarck – New Britain – Solomon Arcs, and shoshonitic volcanism in the Tabar-Lihir-Tanga-Feni (TLTF) island chain.
The oldest rocks are the lower to middle (or lower upper) Oligocene Jaulu Volcanics. These consist of lapilli tuff, agglomerate, and subordinate porphyritic pyroxene andesite lava, and are intruded by gabbro, norite, diorite, tonalite, trondhjemite, granodiorite, and leucocratic dyke rocks, which have been named the Lemau Intrusive Complex.
c.) associated local stress regime(s) and likely types of faults:
The Weitin and Sapom Faults are the major structural features on New Ireland. Movement on the Weitin Fault may be left-lateral. New Ireland developed presumably on oceanic crust by seafloor (and possibly subaerial) volcanism in the early and middle Oligocene…Left-lateral faulting and crustal extension (?transform faulting) in the late Miocene may have opened a rift between central and southern New Ireland..
d.) what types of geothermal power plants might be warranted:
“Lihir Island geothermal power plant is a 56 MW operating geothermal power plant in New Ireland, Papua New Guinea.”
Commissioned: 2007; 30MW, Flash-steam single. Last updated July 2023.