Volcanic structure of the Tarim flood basalt revealed through 3-D seismological imaging

Abstract

The detailed structures of the volcanic edifice and plumbing system of the early Permian Tarim flood basalt were investigated by three-dimensional seismic imaging. The images show that the Tarim flood basalt erupted from central volcanoes distributed along major faults. The uppermost magma formed a single lava lobe with a volume of ~0.74km3 and an aspect ratio of 50, implying a sheet flow eruption with a high effusion rate. At the subsurface level, all central volcanoes, irrespective of size, had a separate pipe-like feeder vent. Only thirteen dikes were identified at shallow depths of <100m below the lava surface; deeper dikes were even rarer. The pipe-like plumbing system and the paucity of dilational dikes were different from the typical plumbing system of flood basalt provinces on Earth, which are normally buoyancy-controlled dike–sill networks. A gas-driven vigorous eruption can be inferred from the imaged structure, which means that the Tarim flood basalt may have carried and released a large proportion of volcanic gas, similar to some mafic volcaniclastic deposit-bearing continental flood basalt provinces.