Inherited Lithospheric Structure Controls Cenozoic Intraplate Basaltic Volcanism in Central Mongolia Due To Mantle Upwelling

Abstract

The mechanisms responsible for intracontinental basaltic volcanism are not well understood. The Cenozoic long-lived (∼30 Myr) and diffuse intraplate volcanism in central Mongolia is an ideal natural lab to address this issue. Here we present a high-resolution lithospheric 3-D shear-wave velocity model using ambient noise tomography with data mainly from two dense seismic arrays. Our model shows strong lithospheric heterogeneities beneath central Mongolia, correlating well with the occurrence of Cenozoic basaltic volcanism. Specifically, relatively thick, high-velocity lithospheric mantle is imaged beneath the central Hangai Dome and the Hövsgöl region where Precambrian basements have been suggested to exist, which likely represent relicts of old cratonic lithosphere. Step changes in lithospheric thickness formed at their peripheries due to heterogenous lithospheric thinning or modification likely caused by recent deep mantle upwelling. More interestingly, most basaltic volcanism in central Mongolia is located at or near these strong lateral gradients of lithospheric thickness, suggesting the important role of small-scale convection in their formation due to lithospheric thickness undulations. Taken together, the Cenozoic intraplate volcanism in central Mongolia was likely controlled by inherited lithospheric heterogeneities and mantle upwelling.