The closure temperature concept is only appropriate for uniform and moderate to rapid cooling from temperatures corresponding to complete He diffusive loss to complete He retention. Second, it should lack major compositional zoning and have relatively uniform U and Th concentrations. Performing depth measurements adds another analytical step and partly defeats the purpose of the pairwise dating method. The use of independently dated calibration standards is not a new idea in thermochronology. Campbell, S.
The accuracy of 29 Si beam intensity as a proxy for ablation rate is likely to improve if an eximer laser is used for both stages of the analysis.
Research Methods - Thermochronology
Abstract This paper presents a significantly simplified method for in-situ U-Th-He dating removing the need to know any absolute concentrations or ablation pit volumes. Mattinson, and D. At this point we should note that it is far easier to measure the depth of an ablation pit than it is to measure its volume. A mixed Ar-He flux of 1. Third, some of the excess scatter of the drill rate proxy may be caused by plasma-induced variability of the 29 Si signal. Chemical Geology McDougall and T.