The U-Pb ages and Sm-Nd isotopic data from the LASS method support the conclusions drawn from previous results that monazite can record timing and information about the source region(s) of hydrothermal fluids.I have been struggling to fit my data with an exponential in matlab - it ends up looking like a flat line, to a curve. The LASS method is then applied to mona-zite from the Birch Creek Pluton in the White Mountains of California as a case study to illustrate the utility of this method for solving geologic problems. The accuracy of the Sm-Nd method is assessed by comparing the LA-MC-ICP-MS results with ID-TIMS determinations on a well-characterized, in-house monazite reference material. The LASS results agree within uncertainty with the isotope dilution thermal ionization mass spectrometry (ID-TIMS) U-Pb dates. Precision and accuracy of the U-Pb method (and the precision of the Sm-Nd method) is demonstrated with results from well-characterized monazite reference materials.
This approach provides age, tracer isotope, and trace element data in the same ablation volume, reducing sampling problems associated with fine-scale zoning in accessory minerals and minimizing the material needed for ablation. In addition to Sm and Nd isotopes, the MC-ICP-MS is configured to also acquire Ce, Nd, Sm, Eu, and Gd elemental abundances. Ablated material is split using a Y-connector and transported simultaneously to both mass spectrometers.
This method uses a laser ablation system coupled to a magnetic-sector inductively coupled plasma mass spectrometer (HR) (ICP-MS) for measuring U-Pb isotopes and a multicollector (MC) ICP-MS for measuring Sm-Nd isotopes. Results are presented for in situ simultaneous determination of U-Pb and Sm-Nd isotopes in monazite using the Laser Ablation Split-Stream (LASS) method.
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