At the LGC, we measure the isotopic signatures of the uranium fission-track (apatite and zircon), (U-Th)/He (apatite), K/Ar (biotite, muscovite and sanidine) and U-Pb (zircon) systems. This is a unique UK facility established and equipped principally through NERC, SRIF, JREI, EU and industry funding.

Fission Track Chronometry

FT ages are determined by the external detector method with reference to an analyst-specific zeta calibration factor determined by multiple analyses of mineral age standards. For data analysis, the laboratory is equipped with Zeiss Axioplan microscopes with automated Kinetek XY stages, and digitising tablets under computer control. Uranium maps of sample grain mounts are produced by irradiation in the research reactor of the Technical University of Munich, Garching, Germany or by LA-ICPMS using a New Wave NWR 193nm laser ablation system and Agilent 7700x ICP-MS.

U-Th/He Chronometry

Helium is measured using a Patterson Instruments automated system equipped with a Balzers quadrupole mass spectrometer. For extraction the sample is heated using either a resistance furnace or a 25W 808 nm diode laser. Uranium and thorium are measured using by acid digestion and isotope dilution on the Agilent 7700x ICP-MS system.

U-Pb Zircon Chronometry

Zircon U-Pb dating is performed on a New Wave NWR 193nm laser ablation system coupled to an Agilent 7700 quadrupole-based ICP–MS. Real time data is processed using GLITTER against repeated measurement of Temora, GJ-2, 91500 and Plesovice zircon standards to correct for instrumental mass bias and depth-dependent inter-element fractionation of Pb, Th and U.

Noble Gas Geochemistry

We use a Nu Instruments 'Noblesse' sector-field mass spectrometer for a range of applications including in-situ U-Th-He dating of zircon, Ar dating of K-bearing minerals, and cosmogenic 3He and 21Ne analysis of quartz and pyroxene. Three different lasers are used to release noble gases from the samples, with wavelengths of 10.6μm, 808nm, and 213nm, respectively. Gas purification uses a purpose built extraction line using a N2-cooled cold trap filled with ball bearings, one SAES GP50 and two NP10 getters. Calibration is done using an air shot from a custom-made reservoir and pipette system.

Sample Preparation

The geochronology centre also operates facilities for sample comminution and mineral separation.