Long-lived seamount subduction in ancient orogens: Evidence from the Paleozoic South Tianshan

et al., 2019; Wan et al., 2020), many geological records of plume-subduction interactions should be preserved in orogenic belts. However, because of the absence of a pre-Mesozoic seafloor record, diagnostic features of plumesubduction interactions have not been fully realized yet. As a result, only few examples of such events are described in fossil orogens (Murphy et al., 1999; Li and Li, 2007; Betts et al., 2015; Fletcher and Wyman, 2015; Bonnet et al., 2019). Identifying plume-subduction interaction in the geologic record and understanding its potential influence on tectonics and implications for crustal-mantle dynamics are thus severely limited at present. Along the present-day circum-Pacific subduction girdle, seamount subduction is known to have significant effects on subduction dynamics including on seismicity and arc magmatism. Because seamount subduction should have occurred throughout much of Earth history, its effects on orogenesis in the overriding plate should be identifiable in ancient orogens. In this study, we investigate the Paleozoic South Tianshan orogen of Central Asia, for which abundant evidence of seamount subduction exists, further bolstered by the continuation of a long-lived plume-induced large igneous province on the subsequently accreted Tarim craton. We find that semi-continuous seamount subduction from ca. 400 to 330 Ma temporarily shut down arc magmatism, and once the seamounts were completely subducted, then arc magmatism resumed and eclogites were quickly exhumed. If such an orogenic fingerprint of seamount subduction can be identified in ancient orogens, a much more complete picture of plumesubduction interaction and its influence on both crustal and mantle processes can be developed.

Automated summary

Research shows that ancient orogens may contain evidence of seamount subduction, which can temporarily shut down arc magmatism and quickly exhumed eclogites, influencing both crustal and mantle processes. Identifying these signatures in ancient orogens could provide a more complete picture of plume-subduction interaction and its effects.