U th he dating
PY - 2005/4Y1 - 2005/4N2 - Geochronology and thermochronology on detrital material provides unique constraints on sedimentary provenance, depositional ages, and orogenic evolution of source terrains.
Important results include the fact that detritus from ancient orogens may dominate sediments thousands of kilometers away, crustal melting and exhumation appear to be spatially-temporally decoupled in at least two orogens, and first-cycle volcanic zircons older than depositional age are surprisingly rare in most settings except in the continental interior.
is specifically designed for high-precision and high-accuracy thermochronometry and is currently under construction at BGC.
The lab will simultaneously and accurately measure nuclide abundances and temperatures during stepwise thermal extraction of noble gases from minerals and glasses over a wide range of temperatures.
The most recently developed dating technique applied to phosphates, described in this chapter, uses the accumulation of α particles from U and Th series decay, (U-Th)/He dating.
While phosphate U-Th-Pb dating is usually used to date high temperature events such as crystallization of igneous rocks and the timing of prograde metamorphism, fission track and (U-Th)/He dating are more commonly used to establish cooling histories through low temperatures, for example, in the range ~110-40°C in the case of apatite. Monazite and xenotime have only recently come under scrutiny for He geochronology (e.g., Pik and Marty 1999), and little is yet known of their potential for routine geo- or thermochronometry.
describe dating based on damage tracks from the spontaneous fission of ^(238)U.18 (U-Th)/He Dating: Techniques, Calibrations, and Applications Kenneth A.Farley Division of Geological and Planetary Sciences California Institute of Technology Pasadena, California 91125 [email protected] The possibility of dating minerals by the accumulation of 4 He from U and Th decay has been recognized for many years (e.g., Strutt 1905), but in the century since the idea was first conceived, the method has rarely been applied successfully. (1996a) found that apatite He ages increase systematically with sample elevation in a mountain range, as expected for exhumation-induced cooling through a low closure temperature. 2000) constraints on He diffusivity, recent attention has focused on applications of apatite He thermochronometry.Dating of minerals using radiogenic He was first explored shortly after the discovery of radioactivity (Strutt 1908) and was investigated extensively in the 1950s and 1960s, mostly on very U- and Th-rich minerals such as zircon and titanite (Hurley 1952, 1954; Damon and Kulp 1957, Damon and Green 1963). Apatite He dating was first investigated by Zeitler et al.