Crustal structure of the Emeishan large igneous province inner zone revealed by deep seismic reflection profile

Emeishan large igneous province (ELIP) is located at the western margin of Yangtze plate, close to Sanjiang tectonic belt. The ELIP has suffered strong destruction and deformation of complex tectonic setting. Due to the lack of high-precision geophysical exploration, the understanding of the fine structure of the crust in this area is insufficient, which greatly affects the understanding of the formation mechanism of large igneous provinces. We implemented a deep seismic reflection profile in Dayao-Yuanmou section, tested a method of collecting deep seismic reflection data based on node seismograph, and obtained a high-resolution structural image of the inner zone of Emeishan large igneous province. The deep seismic reflection data collected by the two types of seismometers show that the data collected by the node seismograph can achieve the effect of the deep reflection data collected by the cable seismograph 428XL, and even perform better in local feature. The results of this test are conducive to the development of low-cost, high-efficiency, and multiple data collection methods. The results of seismic stack profile show that the lower crust is gradually uplifting from west to east. At about TWT (Two-way travel time) 13 s (about 40 km depth) in the west of the profile, with a thickness of about 17.5 km appears. To the east of the profile, the upper interface depth of the dense reflection area corresponds to TWT 11 s, the bottom interface corresponds to TWT 16 s. Based on the results of early geological and geophysical studies, this dense reflection feature is presumed to be caused by iron and magnesium materials invading the crust in the inner belt when Emeishan Large Igneous Province was formed, which corresponds to the active remains of Permian mantle plume.