| 英文摘要: | Minerals are powerful, but tiny, time capsules of past Earth events and conditions. Unpacking these geochemical time capsules involves two major challenges: 1) precise and accurate measurement of mineral composition at the scale of micrometers, and 2) linking micro scale mineral composition to tectonic-scale geologic events. This research project will use recent advances in analytical technology to investigate oxygen isotopes in individual minerals from a tectonically unique region of the western United States. Measured oxygen isotope patterns will be used to quantify temperature, time, and water composition during tectonic deformation. Oxygen isotope data will thus provide new, highly detailed information about the past movement of heat and fluids, which is necessary to understanding ore formation and deformation of Earth's crust. This research will expand geochemical methodologies, both analytical and computational, for transforming small-scale data from minerals into understanding of big-picture geologic events and processes. This award is co-funded by the Petrology & Geochemistry program and EPSCoR (Experimental Program to Stimulate Competitive Research) and will help enable the research training of two undergraduate and two graduate students at the New Mexico Institute of Mining and Technology. Specifically, advanced students will undertake a project that combines skills in analytical geochemistry and computational modeling that will prepare them for careers that require technological fluency and the ability to perform quantitative data analysis. The proposed project will also help to establish the research program of an early-career female geoscientist.
The spatial variability (zoning) of oxygen-isotope composition within individual mineral grains is, as yet, a largely untapped record of past thermal events and fluid-rock interactions. Many zoning studies have investigated chemical zoning in minerals, but only recently have advances in analytical techniques opened up investigation of isotopic zoning. Oxygen-isotope zoning is particularly useful as a monitor of changing metamorphic conditions and/or fluid-rock interactions over time because the oxygen-isotope composition of minerals is sensitive to temperature and fluid isotopic composition. The Fast Grain Boundary (FGB) conceptual and numerical model aid in linking grain-scale mass transfer to rock microstructure and macrostructure, and then to larger-scale tectonic drivers of mass transfer. Thus, FGB and oxygen-isotope zoning measurements together represent a new approach for developing meaningful, data-constrained interpretations of intragrain compositional heterogeneity. This research will therefore leverage state-of-the-art in situ measurement techniques, in combination with FGB computational tools, to investigate the thermal and fluid histories of several western US metamorphic core complexes as preserved in oxygen-isotope zoning. |