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Mineralogical Society of America , Washington, DC, pp. For example, apatite usually has a few tens of ppm of both U and Th, while monazite and xenotime usually have hundreds of ppm to weight percent levels of these elements. AUTHORS:20121116-075945167 Full text is not posted in this repository. Use this Persistent URL to link to this item: AUTHORS:20121116-075945167The common phosphate minerals, apatite Ca_5(PO_4)_3(F, OH, Cl), monazite (Ce, La, Th)PO_4, and xenotime YPO_4, have found widespread use in geochronology because they incorporate U and Th into their structures.Apatite He dating was first investigated by Zeitler et al. (1987), who studied the diffusion rate of He from apatite and proposed that apatite He dating might provide a useful thermochronometer, recording cooling through about 100°C. 1997, Farley 2000) and in the natural setting (House et al. 2000) have confirmed this idea, and the technique has now been applied to a range of tectonic, geologic and geomorphologic problems (e.g., House et al. Duango Apatite Age Standard (2004) Helix SFT Noble Gas Mass-Spec and Extraction Line for 4He/3He Analysis In 2012, the UT (U-Th)/He laboratory added a Thermo Helix SFT magnetic sector mass-spectrometer with dedicated UHV extraction and purification line.The line will be equipped with a diode laser for laser heating, two light-bulb furnaces for low-temperature step heating, and a Photon Machine Analyte G.2 Excimer Laser Ablation system for laser-ablation He dating development.
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).
describe dating based on damage tracks from the spontaneous fission of ^(238)U.
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.
In contrast, no useful geochronologic information was obtained from relict apatite, because common Pb in these grains overwhelmed radiometrically derived isotope ratios.
In: Phosphates: Geochemical, Geobiological, and Materials Importance. As a consequence, these phosphates can be dated using several fundamentally different isotopic techniques. describe phosphate dating using ingrowth of radiogenic Pb, the final daughter of U and Th series decay, and Gleadow et al.
The quadrupole He mass spectrometry systems consist of the following principle components: 1) One Photonmachine 30W Diode Laser and two Photonmachine 75W Diode lasers and a U. Laser continuous-mode Nd-YAG lasers for total fusion He laser extraction, ideal for single-crystal work (see House et al., 2000), 2) two separate all-metal extraction lines equipped with computer-controlled pneumatic Nupro valves and pumped by a combination of ion, turbo and rough pumps, 3) precise volume aliquot systems for spiking sample gas with 3He for isotope dilution, 4) precise volume aliquot systems for delivering a 4He standard with separate depletion tank systems to monitor 4He tank depletion, 5) gas purification system consisting of two SAES NP10 getters and two Janis cryogenic trap capable of separating He from other gases by variable temperature release at 16-37K, and 6) two Blazers Prisma QMS-200 quadrupole mass spectrometer for measuring 3He/4He ratios.