T381 Petrology Across the Inner Solar System: In Honor of Roebling Medalist Ed Stolper (Posters)

Wednesday, 25 October 2017
9:00 AM - 6:30 PM
Halls 4EF

THE USE OF PORTABLE X-RAY FLUORESCENCE, MAGNETIC SUSCEPTIBILITY, AND THE SCANNING ELECTRON MICROSCOPE TO CLASSIFY, CHARACTERIZE, AND DETERMINE THE REDOX STATE OF GRANITES

Paper number: T381-4
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Utah contains granitic intrusions associated with a range of ore deposits that vary spatially, temporally, and chemically. Utah is a prime location for the study of mineralization associated with granites because it encompasses three unique geologic provinces and offers a wide array of emplacement configurations. Past studies in Utah have focused primarily on major elements with a paucity of analyses of trace elements. Moreover, most studies on granites in Utah have focused on single discrete locations without comparisons across locations. Trace element analysis can be used for classifying granites and for locating potentially mineralized granites. Trace element analysis can also lend insight into magma redox, which is important for ore formation. Trace element and redox analyses are both expensive and time consuming. The objective of this study was to determine redox and trace element distribution using tools that are cost effective and readily available. Portable X-ray Fluorescence (pXRF) offers an affordable solution for the rapid measurement of key trace elements in granites. When the pXRF intensities are not calibrated by whole-rock chemical analyses, the results are called semi-quantitative. These semi-quantitative results can be used to determine relative elemental concentrations among a suite of rocks. In this study, a technique is presented for determining the redox state of granitic rocks using both semi-quantitative pXRF results and magnetic susceptibility, another rapid and inexpensive methodology that is underutilized in the field. In addition, it is shown that mapping of oxides and sulfur-bearing minerals by the Scanning Electron Microscope (SEM) aids in determining the redox state of granites by comparing Fe:Ti ratios and observing the presence or absence of sulfate or sulfide. By utilizing equipment that is readily available and cost effective, we have been able to increase the knowledge base of the redox state and mineralizing potential of a wide range of granites in Utah. These results should be important to workers interested in locating ore deposits or understanding the granitic system.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-303581

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