This project involves further development of methods for analyzing nanomole-sized quantities of silicate N by carrier-gas methods, through combination of a high-vacuum extraction line fabricated at Lehigh University and a commercially available continuous-flow, gas chromatography interface. The small-sample capability of the new methods will allow analyses of microgram-sized samples of mineral separates (e.g., micas, ammonium-rich K-feldspars), thus affording higher spatial resolution in some studies and opening up many new avenues of investigation previously impeded by the absence of sufficiently N-rich materials. The research will partly involve incorporation of laser heating in the extractions, production of silicate N-isotope standards for wider distribution to the community, and an attempt to experimentally determine mica-fluid N-isotope fractionations over a temperature range appropriate for study of crustal processes. A common theme in the applications of the new methods over the next five to ten years is the further advancement of N isotope investigation aimed at tracing organic signatures into the crust and mantle.
