Geo-Thermo-chronology (U-Th)/He (apatite, hematite, goethite, magnetite and spinel)

(U-Th)/He geo-thermo-chronometry exploits the decay of the isotopes 238U, 235U, 232Th and 147Sm, the production of associated alpha particles (4He) and the temperature-dependent diffusion of 4He through a crystal lattice. The (U-Th)/He method can be applied to geological problems operating over 0.8 to >1000 Ma. At ISTerre, the (U-Th)/He platform focuses on the dating of apatite, hematite, goethite, magnetite and spinel crystals.

Samples are prepared by extraction of datable crystals (crushing and mineral separation, or by micro-drilling), and crystals or grains are packed in Nd and Pt foils or tubes.

The laboratory includes two automatic He lines for laser heating extraction, purification and 4He concentration analysis of apatite, goethite, hematite, magnetite and spinel crystals or grains. Once the aliquot has been degassed, it is dissolved in a clean room and U-Th and Sm concentrations are determined using an ICP-MS, equipment available within ISTerre’s Geochemistry-Mineralogy (GM) platform.

Details and important information are given in the charter (French).

Contacts
Cécile Gautheron,
Email : cecile.gautheron univ-grenoble-alpes.fr
Mélanie Balvay
Email : melanie.balvay univ-grenoble-alpes.fr