Single-grain, multi-parameter characterization of detrital zircon grains to test for the influence of sample processing and sedimentologic processes

University Of Iowa, Iowa City IA

Investigators

Abstract

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). A cornerstone of modern studies of sedimentary rocks is Uranium-Lead isotopic dating of zircon, a common mineral grain in sandstone. However, there is little understanding of how natural and induced bias can influence the outcome of dates. This project will focus specifically on quantifying: 1) the effect of crushing and grinding rocks prior to analysis, and 2) whether variation in hydraulic conditions during deposition influences zircon populations. The work of this project will lead to greater understanding of potential biases and lead to the development of mitigation strategies. This project will support partnerships between academia and government and engagement of pre-service and in-service teachers through a field experience around the Black Hills area in South Dakota. The objectives of this proposal are to test the influence of 1) standard mineral separation processes for detrital zircon studies on grain size, grain shape, and surface microtextures, 2) hydraulic sorting after negating or accounting for the effects of mineral separation with high-n analyses (n=600). A major outcome of this work will be new protocols for provenance studies that integrates traditional, current, and new techniques to clearly document sediment sources and transport history. Our workplan includes: 1) tandem processing of samples using traditional and newer approaches followed by high throughput particle analysis to comprehensively characterize particle size and shape, and 2) single-grain, multi-parameter characterization of detrital zircons to explore for correlations between age groups, grain size/shape, surface morphology, and sediment transport history in a variety of ancient lithofacies representing different hydraulic conditions. This research will elucidate any inherent biases related to mineral separation and depositional energies in sedimentary systems. Being able to decipher the ‘true’ provenance in sedimentary basins will lead to better paleogeographic and sediment dispersal interpretations and tectonic reconstructions. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.