Helium chronometry of apatite and titanite using Nd-YAG laser heating

We developed a technique for extracting He-4 from apatite and titanite usin g laser heating that permits measurement of U and Th and, hence, (U-Th)/He ages, on a single sample aliquot. Unlike direct laser heating, quantitative He extraction and U, Th retention can be achieved when samples are indirec tly laser heated to temperatures below their melting point. Resulting He ag es are consistent with those obtained from conventional furnace heating of larger samples. The major advantages of this technique include faster analy sis and far lower, more reproducible He blanks that permit single crystal a nalyses. Single crystal dating opens a variety of new avenues for (U-Th)/He chronometry. (C) 2000 Elsevier Science B.V. All rights reserved.