Crustal velocity structure in the Emeishan large igneous province and evidence of the Permian mantle plume activity

Abstract

The Emeishan large igneous province (ELIP) in SW China is interpreted to be associated with an ancient mantle plume. Most of the constraints on the role of mantle plume in the generation of the Emeishan flood basalts were provided by geological and geochemical methods, but the geophysical investigation is very limited. In order to better understand the deep structure and features of ELIP, we have studied the crustal velocity structure using the data acquired from the Lijiang-Panzhihua-Qingzhen wide-angle seismic profile. This profile crosses the three sub-zones of the ELIP (the inner, intermediate, and outer zones), divided based on the differential erosion and uplift of the Maokou limestone. The results provided by the active source seismic experiment demonstrate: (1) The average depth of the crystalline basement along the profile is about 2 km. (2) The middle crust in the Inner Zone is characterized by high-velocity anomalies, with the average velocity of 6.26.6 km/s, which is about 0.1-0.2 km/s higher than the normal one. The velocity of the lower crust in the inner zone is 6.97.2 km/s, higher than those observed in the intermediate and outer zones (6.77.0 km/s). Relatively low velocity anomalies appear in the upper, middle and lower crusts near the junction of the inner zone and intermediate zone, probably due to the effect of the Xiaojiang fault (XJF). (3) The average velocity of the crust is comparatively low on both sides of XJF, especially on the east side, and the average velocity of the consolidated continental crust is also low there. This may suggest that the XJF extends at least down to 40 km deep, even beyond through the crust. (4) The depth to the Moho discontinuity decrease gradually from 4753 km in the inner zone, via 4250 km in the intermediate zone to 3842 km in the outer zone. In the inner zone, the Moho uplifts locally and the (consolidated) crust is characterized by high-velocity anomalies, which are likely related to intensive magma intrusion and underplating associated with melting of plume head. Overall the crustal velocity structure in the study area recorded the imprint left by the Permian Emeishan mantle plume. Emeishan large igneous province, Permian mantle plume, wide-angle seismic reflection/refraction data, Lijiang-PanzhihuaQingzhen profile, crustal velocity Citation:Xu T, Zhang Z J, Liu B F, et al. 2015. Crustal velocity structure in the Emeishan large igneous province and evidence of the Permian mantle plume activity. Science China: Earth Sciences,

Crustal Structure of Southwest China and Northern Vietnam From Ambient Noise Tomography: Implication for the Large‐Scale Material Transport Model in SE Tibet

“…In addition, the velocity in the inner zone of the Emeishan large igneous province (LIP) is relatively higher than that in the surrounding area, which is also clearly observed by some other tomographic studies (e.g., Bao et al, ; Yao et al, ; Figure ). This high‐velocity anomaly supports the idea of residual basalts in the Permian (Xu et al, , ).…”

“…The center of the southern SYB shows a relatively high velocity. Previous studies have revealed the similar features of this area: high seismic velocity, low attenuation, high Vp/Vs ratios, low heat flow, and high density anomaly (Bao et al, ; Chen et al, , ; Deng et al, , ; Shen et al, ; Wei et al, ; Xu et al, ; Yang et al, ; Yao et al, ; Zhao et al, ; Figure ). These features manifest the strength of the crust in this area, which may result from the generation of the Emeishan basalts and crustal accretion during the upwelling of a mantle plume in the Permian (Chen et al, ; He et al, ).…”

Magmatic underplating and crustal growth in the Emeishan Large Igneous Province, SW China, revealed by a passive seismic experiment

“…At each station of the COMPASS-ELIP array, we first processed the available data set of RFs using the H-stacking method based on the averaged crustal P-wave velocity model (Fig. 5b) derived from the COMWIDE-ELIP experiment (Xu et al, 2015) (Fig. 5d), and estimated the standard errors of H and Vp/Vs ratio by the bootstrap method (Efron and Tibshirani, 1986) for 100 trials.…”

“…However, in this study, we used a modified model that was based on the crustal P-wave velocity ( Fig. 5b) derived from the COMWIDE-ELIP experiment (Xu et al, 2015) and the crustal Vp/Vs ratio ( Fig. 5f) from H- stacking.…”

The lithospheric structure beneath southeast Tibet revealed by P and S receiver functions

“…In the past 30 years, several thousand kilometer sounding profiles have been established in Yunnan region (Kan and Lin, 1986;Zhang et al, 2002Zhang et al, , 2009Xu et al, 2015;Pan et al, 2015). Many other geophysical observations, such as surface wave tomographies (Hu et al, 2008;Yao et al, 2008), receiver functions (Hu et al, 2008;Wu and Zhang, 2011;C.…”