APPLICATIONS AND IMPLICATIONS OF RHENIUM-OSMIUM ISOTOPIC SYSTEMATICS AND HIGHLY SIDEROPHILE ELEMENTS ABUNDANCES IN CRUDE OILS AND THE YOUNGER DRYAS SEDIMENTS

The Re-Os isotopic system is a powerful geochronological and tracing method due to their distinct characteristics in different components of the Earth. The Earth’s mantle and extraterrestrial materials broadly to have a near-chondritic 187Os/188Os ratio of 0.12, whereas that of the Earth’s crust increases to > 1. This large difference has enabled the Re-Os isotope system to be applied to igneous and metamorphic rocks, and also organic-rich sedimentary rocks and petroleum products. Highly siderophile element (HSE) abundances due to their affinity to metals relative to silicates are enriched in the core and chondrites relative to silicate Earth. The Earth’s crust has < 0.1 % of HSE abundances compared to extraterrestrial bodies which makes HSE sensitive indicators of a meteoritic contribution delivered in terrestrial settings. Thus, this study has investigated the application of Re-Os isotope system and HSE abundances in two different systems, a petroleum system from Tarim Basin, China and the Younger Dryas sediments from Texas, USA. The two study subjects utilize similar analytical means to constrain the timing of oil generation or alteration in the evolution of Tarim Basin and to trace the origin of the geochemical anomalies at Younger Dryas cooling period. This dissertation firstly presents Re and Os isotope data from whole oils and asphaltene fractions of a suite of crude oil samples from Tarim Basin. An Early Permian age 286.74 ± 2.34 Ma with mean square of weighted deviates (MSWD) = 2000 six oils is consistent with Tarim Flood Basalt age of 291 ± 4 and 272 ± 2 Ma from U–Pb zircon dating. This study indicates that using Re-Os isotope system, the timing and signature of hydrothermal intrusion into Tarim Basin have been recorded. In the second and third chapters, newly discovered 187Os/188Os ratios and HSE abundances from Hall’s Cave, and the Debra L. Friedkin sites, Texas are reported. Between the two sites, unradiogenic Os peaks are identified above, at, and below the Younger Dryas boundary layer. In addition, the HSE abundances at both study sites resemble volcanic gas aerosols instead of previously confirmed impactites. Thus, distant and episodic volcanic eruptions are plausible mechanisms for the geochemical anomalies.