Meteoritics & Planetary Science, Volume 40, Number 12 (2005)
http://hdl.handle.net/10150/641266
2024-03-29T01:28:57ZBook Review: Meteorite Impact! The Danger from Space and South Africa's Mega-impact, the Vredefort Structure, W. U. Reimold, R. L. Gibson
http://hdl.handle.net/10150/656084
Book Review: Meteorite Impact! The Danger from Space and South Africa's Mega-impact, the Vredefort Structure, W. U. Reimold, R. L. Gibson
King, D. T.
Book Review: Meteorite Impact! The Danger from Space and South Africa's Mega-impact, the Vredefort Structure, W. U. Reimold, R. L. Gibson. Chris van Rensburg Publications (Pty) Ltd., Melville, South Africa (2005).
2005-01-01T00:00:00ZEffects of asteroid and comet impacts on habitats for lithophytic organisms—A synthesis
http://hdl.handle.net/10150/656083
Effects of asteroid and comet impacts on habitats for lithophytic organisms—A synthesis
Cockell, Charles S.; Lee, Pascal; Broady, Paul; Lim, Darlene S. S.; Osinski, Gordon R.; Parnell, John; Koeberl, Christian; Pesonen, Lauri; Salminen, Johanna
Asteroid and comet impacts can have a profound influence on the habitats available for lithophytic microorganisms. Using evidence from the Haughton impact structure, Nunavut, Canadian High Arctic, we describe the role of impacts in influencing the nature of the lithophytic ecological niche. Impact-induced increases in rock porosity and fracturing can result in the formation of cryptoendolithic habitats. In some cases and depending upon the target material, an increase in rock translucence can yield new habitats for photosynthetic cryptoendoliths. Chasmoendolithic habitats are associated with cracks and cavities connected to the surface of the rock and are commonly increased in abundance as a result of impact bulking. Chasmoendolithic habitats require less specific geological conditions than are required for cryptoendolithic habitats, and their formation is likely to be common to most impact events. Impact events are unlikely to have an influence on epilithic and hypolithic habitats except in rare cases, where, for example, the formation of impact glasses might yield new hypolithic habitats. We present a synthetic understanding of the influence of asteroid and comet impacts on the availability and characteristics of rocky habitats for microorganisms.
2005-01-01T00:00:00ZA case study of impact-induced hydrothermal activity: The Haughton impact structure, Devon Island, Canadian High Arctic
http://hdl.handle.net/10150/656080
A case study of impact-induced hydrothermal activity: The Haughton impact structure, Devon Island, Canadian High Arctic
Osinski, Gordon R.; Lee, Pascal; Parnell, John; Spray, John G.; Baron, Martin
The well-preserved state and excellent exposure at the 39 Ma Haughton impact structure, 23 km in diameter, allows a clearer picture to be made of the nature and distribution of hydrothermal deposits within mid-size complex impact craters. A moderate- to low-temperature hydrothermal system was generated at Haughton by the interaction of groundwaters with the hot impact melt breccias that filled the interior of the crater. Four distinct settings and styles of hydrothermal mineralization are recognized at Haughton: a) vugs and veins within the impact melt breccias, with an increase in intensity of alteration towards the base; b) cementation of brecciated lithologies in the interior of the central uplift; degrees C) intense veining around the heavily faulted and fractured outer margin of the central uplift; and d) hydrothermal pipe structures or gossans and mineralization along fault surfaces around the faulted crater rim. Each setting is associated with a different suite of hydrothermal minerals that were deposited at different stages in the development of the hydrothermal system. Minor, early quartz precipitation in the impact melt breccias was followed by the deposition of calcite and marcasite within cavities and fractures, plus minor celestite, barite, and fluorite. This occurred at temperatures of at least 200 degrees C and down to ~100-120 degrees C. Hydrothermal circulation through the faulted crater rim with the deposition of calcite, quartz, marcasite, and pyrite, occurred at similar temperatures. Quartz mineralization within breccias of the interior of the central uplift occurred in two distinct episodes (~250 down to ~90 degrees C, and <60 degrees C). With continued cooling (<90 degrees C), calcite and quartz were precipitated in vugs and veins within the impact melt breccias. Calcite veining around the outer margin of the central uplift occurred at temperatures of ~150 degrees C down to <60 degrees C. Mobilization of hydrocarbons from the country rocks occurred during formation of the higher temperature calcite veins (>80 degrees C). Appreciation of the structural features of impact craters has proven to be key to understanding the distribution of hydrothermal deposits at Haughton.
2005-01-01T00:00:00ZIntra-crater sedimentary deposits at the Haughton impact structure, Devon Island, Canadian High Arctic
http://hdl.handle.net/10150/656082
Intra-crater sedimentary deposits at the Haughton impact structure, Devon Island, Canadian High Arctic
Osinski, Gordon R.; Lee, Pascal
Detailed field mapping has revealed the presence of a series of intra-crater sedimentary deposits within the interior of the Haughton impact structure, Devon Island, Canadian High Arctic. Coarse-grained, well-sorted, pale gray lithic sandstones (reworked impact melt breccias) unconformably overlie pristine impact melt breccias and attest to an episode of erosion, during which time significant quantities of impact melt breccias were removed. The reworked impact melt breccias are, in turn, unconformably overlain by paleolacustrine sediments of the Miocene Haughton Formation. Sediments of the Haughton Formation were clearly derived from pre-impact lower Paleozoic target rocks of the Allen Bay Formation, which form the crater rim in the northern, western, and southern regions of the Haughton structure. Collectively, these field relationships indicate that the Haughton Formation was deposited up to several million years after the formation of the Haughton crater and that they do not, therefore, represent an immediate, post-impact crater lake deposit. This is consistent with new isotopic dating of impactites from Haughton that indicate an Eocene age for the impact event (Sherlock et al. 2005). In addition, isolated deposits of post-Miocene intra-crater glacigenic and fluvioglacial sediments were found lying unconformably over remnants of the Haughton Formation, impact melt breccias, and other pre-impact target rock formations. These deposits provide clear evidence for glaciation at the Haughton crater. The wealth and complexity of geological and climatological information preserved as intra-crater deposits at Haughton suggests that craters on Mars with intra-crater sedimentary records might present us with similar opportunities, but also possibly significant challenges.
2005-01-01T00:00:00Z