Variable Depths of Magma Genesis in the North China Craton and Central Asian Orogenic Belt Inferred From Teleseismic P Wave Attenuation

Eastern Asia is a prime location for the study of intracontinental tectono-magmatic activity. For instance, the origin of widespread intraplate volcanism has been one of the most debated aspects of East Asian geological activity. Measurements of attenuation of teleseismic phases may provide additional constraints on the source regions of volcanism by sampling the upper mantle. This study uses data from three seismic arrays to constrain lateral variations in teleseismic P wave attenuation beneath the Central Asian Orogenic Belt and the North China Craton. We invert relative observations of attenuation for a 2-D map of variations in attenuation along with data and model uncertainties by applying a Hierarchical Bayesian method. As expected, low attenuation is observed beneath the Ordos block. High attenuation is observed beneath most of the volcanoes (e.g., the Middle Gobi volcano, the Bus Obo volcano, and the Datong volcano) in the study area, and estimated asthenospheric Qp values span from 95 to 200. These values are within the range of globally average asthenosphere. We infer that these volcanoes may tap melt from ambient asthenosphere and occur where the lithosphere is thin, which is consistent with previous petrologic studies. More complex mantle drivers of volcanism are not rejected but are not needed to explain eruptions in this area. In contrast, at the Xilinhot-Abaga volcanic site, the observed low attenuation (as low as beneath the Ordos block) excludes a typical shallow melting column. Fluids from the subducted Pacific plate may initiate the deep melting and would be consistent with petrological constraints.

Automated summary

This study investigates the teleseismic P-wave attenuation beneath the Central Asian Orogenic Belt and the North China Craton using seismic data. The results show that high attenuation is observed beneath most of the volcanoes, suggesting that these volcanoes may tap melt from the ambient asthenosphere and occur where the lithosphere is thin. However, at the Xilinhot-Abaga volcanic site, low attenuation is observed, indicating that deep melting may be initiated by fluids from the subducted Pacific plate.