T101 From Outcrops to the Base of the Crust: Integrated Geophysical and Geological Illumination of Earth’s Tectonic Fabrics to Refine Understanding of Crustal Evolution and Natural Resources (Posters)

Monday, 10 October 2022
9:00 AM - 1:00 PM
Exhibit Hall F

GLOBAL LOWER CRUSTAL DENSITIES FROM CONVERSION OF SEISMIC BODY WAVES

Paper number: T101-13
Program: Technical Sessions
Time: 9:00 AM – 1:00 PM

Authors

Abstract

Crustal characteristics constrain the silicate mantle's temporal evolution and the extraction of the Earth’s crust. We developed a new method for determining lower crustal densities from observations of P-to-S converted phase amplitudes. We constructed 86,987 receiver functions from seismic waves recorded by 16,086 seismic stations globally. Lower crustal and upper mantle body wave velocities - necessary for calculating density - derived from the Litho1.0 global seismic velocity model. We assumed a constant upper mantle density – 3.35 g/cm³, consistent with parameter sensitivity tests we carried out. We thus calculated 5,685 lower crustal density estimates. The mean density is 3.0 ± 0.3 g/cm³, consistent with a mafic lower crustal composition. We divided our lower crustal density estimates into 22 different terrane types according to the global analyses of Hasterok et. al. (2022). Mann-Whitney-Wilcoxon U rank tests of lower crustal densities of these terranes, applied pairwise, allow us to discriminate between the two samples, providing a probability estimate that the lower crustal densities derive from the same parent distribution. Our results show that Atlantic-Indian Ocean hotspots have a different lower crustal density distribution, relative to all the other subterranes, than the Pacific oceanic hotspot distribution. Archean craton lower crustal densities show a clear affinity for those of arc terranes. The lower crust of younger shield areas is more like that of orogenic belts and magmatic provinces.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-380365

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