LPI Seminar Series
Effective January 1, 2011, LPI seminars will be held on Fridays.
LPI seminars are held from 3:30–4:30 p.m. in the Lecture Hall at USRA, 3600 Bay Area Boulevard, Houston, Texas. Refreshments are served at 4:30 p.m. For more information, please contact Nicolas LeCorvec (phone: 281-486-2118; e-mail: email@example.com) or Paul Byrne (phone: 281-486-2140; e-mail: firstname.lastname@example.org). A map of the Clear Lake area is available here. This schedule is subject to revision.
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- Wednesday, April 15, 2015 - Lecture Hall, 3:30 PM
Barry Shaulis, University of Alberta
Investigating early lunar evolution through U-Pb chronology of the Northwest Africa 773 Clan Meteorites
The Northwest Africa (NWA) 773 clan of meteorites represent some of the youngest lunar igneous rocks discovered so far. We selected four members of the NWA 773 clan of meteorites for U-Pb zircon and baddeleyite age analysis: NWA 773, NWA 3170, NWA 6950, and NWA 7007. These meteorites were selected because: 1) Constraining the timing of igneous activity that produced these lunar rocks is critical to furthering our understanding of the thermal evolution of the Moon and evaluating potential heats sources responsible for igneous activity at least 1.5 Gyrs after lunar accretion; 2) Each of the meteorites is partially or wholly comprised of one or both of the magnesian or ferroan gabbro lithologies. This is crucial to further understanding of the proposed co-magmatic origin of the lithologies. 3) Several members contain merrillite or apatite in either a breccia or gabbro lithology. Merrillite and apatite are important uranium bearing minerals for dating and can therefore be used to establish an impact and/or brecciation history of the NWA 773 clan via U-Th-Pb dating methods. A total of 50 baddeleyite grains were analyzed and yielded weighted average 207Pb-206Pb ages of 3119.4 ± 9.4 Ma for the magnesian gabbro, 3106 ± 22 Ma for the ferroan gabbro, and 3115 ± 14 Ma for the polymict breccia. These data establish a strong chronologic link between the meteorites and indicate that the magnesian and ferroan gabbro lithologies formed at similar times. This implies that they are both temporally and petrogenetically related. A single large zircon grain found in the polymict breccia of NWA 773 yielded a U-Pb concordia age of 3953 ± 16 Ma, indicating a significantly more ancient component within the breccia. A 2718 ± 44 Ma weighted average U-Pb age of apatite from the polymict breccia and magnesian gabbro lithologies is interpreted to date the brecciation event that assembled the NWA 773 clan components on the Moon.
- Friday, April 17, 2015 - Lecture Hall, 3:30 PM
David Leverington, Texas Tech University
Is Early Development of Large Volcanic Channels Typical of all Rocky Planets?
The vestiges of large volcanic channels are preserved at the surfaces of the Moon, Venus, Mercury, Mars, and Io. The largest of these systems have widths of tens of kilometers and lengths of thousands of kilometers. Component channels were incised by voluminous low-viscosity lava flows, and are the surface expressions of magmatic systems that helped to dissipate internal heat accumulated through processes of accretion, differentiation, tidal interactions, and radioactive decay. Most of the more than 200 channels on the Moon are relatively simple systems that developed in the first ~1.5 Ga of solar system history. Lunar channels have widths of up to ~5 kilometers and lengths of up to several hundred kilometers. The more than 200 channels on Venus may have developed during the most recent 1 Ga. Some Venusian systems variously have lengths of thousands of kilometers, widths of tens of kilometers, and channel forms of remarkable complexity. Ten channel systems on Mercury have lengths of up to ~160 km and widths of up to tens of kilometers, and likely developed ~3.7 Ga before present as conduits for flood lavas emplaced across adjacent lowlands. The outflow channels of Mars have lengths of up to thousands of kilometers and widths of up to tens of kilometers, and mainly formed in the first ~1.5 Ga of solar system history. These systems are interpreted by most researchers as products of large aqueous outbursts from aquifers. However, support for aqueous interpretations is weak, and it is increasingly apparent that the characteristics of Martian outflow channels closely match those expected of volcanic systems. Widespread past development of large volcanic channels on rocky bodies beyond Earth suggests the possible formation of analogous systems on the Earth during the Hadean or Archean, a time frame of heightened internal temperatures and eruption of low-viscosity magmas. More generally, the geological record of the inner solar system suggests a predisposition of all rocky planets for early incision of large volcanic channels.