Physical Sciences and Mathematics Commons^™

Shock Effects Recorded By The U-Pb Radiometric System In Zircons Of Apollo 17 Impact Breccias And By Raman Spectroscopy In Enstatite Meteorites, Bidong Zhang

Electronic Thesis and Dissertation Repository

Impact cratering processes and formations are ubiquitous on the rocky planets within the Solar System. The Earth-Moon system was formed by a massive planetary impact, and numerous impacts afterwards significantly reshaped the topography and lithology of the Moon surface. This dissertation focuses on studying some specific geochemical, geochronological, and geophysical signatures of impact processes preserved in lunar rocks and asteroidal meteorites.

The zircon U-Pb radiometric system is one of the most reliable geochronometers in measuring geological time. Recently, unsupported radiogenic Pb enrichment has been reported to compromise the accuracy and precision of zircon U-Pb geochronometer in terrestrial rocks. In Chapter …

Sm-Nd, Lu-Hf, And Mn-Cr Isotope Geochemistry Of Achondrite Meteorites: Implications For The Formation Reservoirs Of Differentiated Planetesimals, Zhiguo Guo

Electronic Thesis and Dissertation Repository

Accretion and differentiation of planetesimals are critical steps of planetary formation. By studying achondrite meteorites, we can bring further geochemical and chronological constraints on the source and composition of materials and their evolution throughout the protoplanetary disk. Major and trace element analyses for mineral and whole-rock compositions and high-precision isotopic compositions for the short- and long-lived radiochronometers ⁵³Mn-⁵³Cr, ^147,146Sm-^143,142Nd and ¹⁷⁶Lu-¹⁷⁶Hf are reported for two eucrites, two diogenites, and three ungrouped achondrites. Of these, NWA 12338 is a newly classified ungrouped achondrite with an anomalously higher Δ¹⁷O than mean …

Ni And Fe Isotope Fractionation During Weathering And The Formation Of Ni Laterite Ore Deposits In The Philippines, Congxi Zhu

Electronic Thesis and Dissertation Repository

Weathering processes on Ni-rich ultramafic rocks in tropical areas produce laterites that become exploitable for Ni mining. To better understand these processes, samples were collected stratigraphically with water samples from several Ni mines in the Philippines and studied for Ni and Fe isotope compositions. This study found that Ni isotope fractionation takes place during the formation of Ni-enriched minerals (goethite), when light Ni isotopes are preferentially incorporated into new minerals formed, leaving heavy Ni isotopes in groundwater. The Δ⁶⁰Ni_{Limonite-Bedrock} is up to -0.19 ± 0.32‰. Even though Fe is partitioned with redox state change during these reactions, …

Impact Cratering Processes On The Earth And Moon: Meteorites, Complex Craters, And The Origin Of The Moon, Patrick Hill

Electronic Thesis and Dissertation Repository

This thesis seeks to understand the mechanism of hypervelocity impacts, lunar origin and geology, and stable isotope techniques and its application to lunar material. Three lunar regolith breccias, Dhofar 1673, Dhofar 1983, and Dhofar 1984, were examined. The petrography, mineralogy, isotope chemistry, and bulk chemistry of these meteorites were quantified to investigate their origin. The chemistry of the impact melt rock and bulk chemical analysis suggests sourcing from either the Feldspathic or Outer Feldspathic Highland Terranes. Given the similarities in the meteorites, and the proximal location of each find (within 500 m), this thesis proposes strong evidence for their pairing. …