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Published in W.A. Hustrulid, G.A. Johnson, Rock Mechanics Contributions and Challenges: Proceedings of the 31st U.S. Symposium, 2020
Among the proposed activities at the WIPP is a series of room-scale in situ waste technology experiments designed to determine the amount and composition of gas generated by degradation and corrosion of the Contact-Handled Transuranic (CH TRU) waste packages emplaced in the rooms (Molecke 1989). Each room is part of a multiroom panel with access provided by entryway drifts on each end, as shown in Figure 1. A study (Argüello 1989) was conducted recently to evaluate the impact of mining the alcoves in which these experiments are to be emplaced. The study included a calculation in which the intersection of a disposal room and a panel entryway drift was modeled. This three-dimensional (3D) calculation constitutes the first such computation of the structural response of an intersection of a disposal room and entryway drift at the WIPP, and it may be the first calculation ever performed to simulate the response of a mined right-angle intersection in any creeping medium. The only other 3D creep analysis of an intersection known to the author is that of a 7.5 degree wedge pillar in salt (Preece 1986). The calculation presented here thus provides an opportunity to advance our understanding of how complicated underground openings, truly 3D in nature, respond in such media. The computed creep response of the intersection reveals several interesting features which may at first appear anomalous to those with a “hard rock” background.
Underground Geologic Repositories
Published in Stephen M. Testa, Geological Aspects of Hazardous Waste Management, 2020
Fracturing, as with other rock types, can be problematic. It is assumed that fractures in granitic bodies can be numerous and water filled near the surface but may diminish in both number and magnitude at depth (i.e., 1000 m), yielding a relatively impermeable rock mass. However, these masses have not been studied intensively due to their relatively low abundance of ore deposits. Thus, it is assumed that, at repository depths, fractures would persist, and that any water that would be present would be free to migrate within this fracture-flow system and eventually be in contact with any emplaced canisters. Economically, DOE estimated that a granite repository may cost up to 2.6 times that of rock salt, reflecting higher excavation costs due to difficulties in excavation and potentially deeper depths of excavation. Another concern is the thermal load induced by the waste, especially in the case of radioactive waste, which could potentially generate artificial fractures. Excavation and construction-related activities may also contribute to artificial fracturing.
Early Proterozoic Magmatism and Geodynamics — Evidence of a Fundamental Change in the Earth’s Evolution
Published in O.A. Bogatikov, R.F. Fursenko, G.V. Lazareva, E.A. Miloradovskaya, A. Ya, R.E. Sorkina, Magmatism and Geodynamics Terrestrial Magmatism Throughout the Earth’s History, 2020
The Lebowa Granite Suite comprises the second main component of the Bushveld Complex. According to Gruenewaldt and Harmer (1992), two main granite types predominate; the Nebo Granite, a major unit of coarse-grained, hypersolvus, mildly alkaline granite; and a more evolved, sometimes aplitic variety, the Klikloof Granite. The Nebo granites exhibit a well-developed and fairly systematic chemical and mineralogical zonation, characterized (from base to top) by a decreasing modal plagioclase concomitant with increasing albite component in the plagioclase; decreasing hornblende and increasing biotite; and increasing quartz. These variations are also reflected in the geochemical trends, i.e. Si, K, Rb increase, and Re, Ti, Ca, P, Ba, Sr and Zr decrease upwards through the sheet. The entire granite mass was probably emplaced as an unusually fluid, very hot (perhaps >900°C), relatively anhydrous (initial content ~2.2%) restite-free magma. The granites exhibit all the classical features of mildly alkalic A-type magmas.
Dating initial crystallisation of some Devonian plutons in central Victoria and geological implications
Published in Australian Journal of Earth Sciences, 2023
J. D. Clemens, G. Stevens, L. M. Coetzer
The geology and petrogenesis of this cordierite-rich, subvolcanic, S-type batholith were most recently described in Phillips and Clemens (2013) and Clemens and Phillips (2014). Phillips et al. (2022) demonstrated that the batholith is a very thin sheet-like body that was emplaced in multiple magma pulses. Several plutons were identified and delineated by Phillips and Clemens (2013), but the main mass is known as the Mount Wombat pluton. In the northeast, this body intrudes and contact metamorphoses the rhyolitic to rhyodacitic ignimbrites of the Violet Town Volcanics. Previous zircon U–Pb SHRIMP dating of the Mount Wombat pluton was carried out by Bierlein et al. (2001) and established an age of 374 ± 2 Ma. That sample was taken from near the town of Euroa, in the main part of the Mount Wombat pluton. For this part of the pluton, a more precise CA-TIMS date of 373.5 ± 0.3 Ma was determined by Tulloch et al. (2012, 2017).
Scientific ocean drilling in the Australasian region: a review
Published in Australian Journal of Earth Sciences, 2022
The huge equatorial Ontong Java volcanic plateau on the Pacific Plate east of New Guinea formed 120 million years ago and has significance in several scientific areas. In terms of global change, degassing of the magma emplaced during plateau formation was likely responsible for rendering the global oceans anoxic at depth. As described previously, the Ontong Java Plateau is a portion of a more extensive LIP, now separated also into the Manihiki and Hikurangi plateaus, the latter currently wedged into the convergent margin of the North Island of New Zealand. Four expeditions have drilled the Ontong Java Plateau (7, 30, 130, 192). A complete record of Late Cretaceous, Paleogene and Neogene ocean history has been recovered, allowing a detailed reconstruction of equatorial paleoceanography and paleoclimate.
Petrogenesis of amphibole megacrysts in lamprophyric intraplate magmatism in southern New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2020
Simon H. Serre, Quinten H. A. van der Meer, Tod E. Waight, James M. Scott, Carsten Münker, Tonny B. Thomsen, Petrus J. le Roux
Four samples originating from a lamprophyre ± minor phonolite dike suite in the WDS were chosen due to the occurrence of megacrystic amphiboles. Samples QH12, KST-2, MOA-16 and HOH-1 were collected in the area around Lake Brunner in the Hohonu Dike Swarm (Figure 1B). Hohonu Dike Swarm host rocks were emplaced in the Late Cretaceous (∼ 88 Ma) (van der Meer et al. 2013). The KST-2 sample was collected from a composite dike composed of both lamprophyre and phonolite (Waight et al. 1998a). Sample QH12 originates from a lamprophyric loose boulder collected near the KST-2 dike. Sample OU79943 was collected in the Bonar Range (Scott et al. 2011), southwest of the Hohonu Dike Swarm and is a lamprophyric dike dated to ∼ 69 Ma (van der Meer et al. 2013) (Figure 1B). WDS samples are characterised as camptonitic and carry amphibole megacrysts, as well as spinel-facies peridotite xenoliths (Tulloch and Nathan 1990; van der Meer et al. 2013; Scott et al. 2016b) (Figure 2).