Quantifying Interseismic Volume Strain from Chemical Mass-Balance Analysis in Tectonic Mélanges

Here, we present element concentrations in scaly fabrics, mudstone protoliths, and mineral veins of six tectonic mélanges units in the Cretaceous Shimanto belt and three mélanges units in the Kodiak accretionary complex measured with LA-ICPMS. We then employed chemical mass-balance analysis utilizing this dataset to quantify the strain related to mass transfer along the plate interface. The ensuing results, presented in this report, reveal a notable distinction in average volumetric strain between individual scaly fabrics of the Lower Mugi and Makimine mélanges, which experienced temperatures near the updip and downdip isotherms bounding the seismogenic zone, respectively. To gain further insights, we combined image analysis techniques to integrate the strain over specific areas of interest. Additionally, we compared the volume loss in scaly fabrics with the volume gain, which was represented by the proportion of mineral veins in those areas. The findings indicate a growing discrepancy between volume loss and volume gain in mélanges with higher paleotemperature records.