Basin Thermal History Analysis Using (U-Th)/He Thermochronometry
Richard A. Ketcham, 2012. "Basin Thermal History Analysis Using (U-Th)/He Thermochronometry", Analyzing the Thermal History of Sedimentary Basins: Methods and Case Studies, Nicholas B. Harris, Kenneth E. Peters
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The (U-Th)/He technique is based on the accumulation and diffusive loss of helium generated by alpha decay. The temperatures required to drive diffusion vary with mineral type and characteristics and can range from <50° C to >200° C, an ideal range for basin thermal history analysis. Although promising due to its conceptual simplicity and capacity for quick analysis, (U-Th)/He has proven to be quite challenging in practice due to a variety of complications, such as alpha particle ejection and implantation, grain-size effects, and the influence of radiation damage on helium diffusivity. Recent research has begun to quantitatively characterize many of these processes and their effects, allowing the technique to be applied with increasing confidence and robustness. This paper reviews the current state of knowledge of the physics and chemistry underlying the (U-Th)/He system, and the modeling approaches that allow thermal history information to be extracted from various kinds of data. A new approach for simultaneously accounting for grain-shape effects on both diffusion and alpha particle ejection is proposed. Various examples of basin and other field studies employing (U-Th)/He are reviewed and in some cases reinterpreted using up-to-date tools and approaches. As the (U-Th)/He system is further explored and tested in the field and laboratory, it will become an increasingly robust and versatile tool for basin analysis.