The Mabja Dome Structure in Southern Tibet Revealed by Deep Seismic Reflection Data and Its Tectonic Implications

Abstract

The ongoing India‐Asia collision has led to the formation of the northern Himalayan gneiss domes belt in southern Tibet. The domes are the result of the ongoing convergence and were formed by geological processes that may include crustal thickening, metamorphism, partial melting, and exhumation of middle crustal rocks to the surface. A combination of compressional, extensional, and diapiric processes has been invoked to explain the formation and evolution of these domes. Differentiating among these competing hypotheses requires well‐defined geophysical images of the internal structure of the domes. The Mabja dome is the largest dome within the northern Himalayan gneiss domes belt. A 70‐km long deep seismic reflection profile across Mabja dome was acquired in 2016. The seismic data could provide new information about the structural elements beneath the domes to the depth of 25 Km. We address the structure of the Mabja dome by conducting an integrated analysis of shallow crustal velocity structure and a normal‐incidence seismic reflection image of deeper crust. Our work suggests that the Mabja dome is underlain by shear zones at depths of 10–15 km and two high‐velocity bodies at depths of 3 km possibly representing the eclogitic‐facies rocks or mafic intrusions. We propose that the dome formation may have been controlled by collision‐induced north‐south shortening expressed by thrust stacking of middle crustal rocks, which led to the doming of the upper‐crustal rocks. The proposed mechanism inferred for Mabja dome can be applied to interpret the widespread domes throughout the southern Tibet and other related structures in orogenic mountain belts.

Late Cenozoic cooling and evolution history of the Kangmar dome in southern Tibet: Insights from inverse thermal modeling

“…Liu et al (2006) confirmed that the dip angle of the mid-crustal reflection formed by the Main Himalayan Thrust (MHT) increases progressively with its northward extension and that the MHT continues north of the Kangmar dome. The thrust stacking above the MHT detected by the most recent Frontiers in Earth Science frontiersin.org regional N-S trending seismic profile (Li et al, 2021) between the Mabja dome and Kampa dome was interpreted as the cause of the doming event. However, the GKT was not observed at the corresponding depth in either seismic profile, and the STDS was identified at a depth of 3-3.5 km as a continuous interface overlying the high-velocity body and extending northward for a considerable distance (Figure 10D).…”

“…Note that the detachment of the STDS persisted, and the YGR became active at some approximate later time. (C) Continued fast cooling due to glacier activity; (D) interpretation of the deep seismic reflection profile image byLi et al (2021). R1-R5 are relatively high reflections.…”

Continent‐Continent Collision Between the South and North China Plates Revealed by Seismic Refraction and Reflection at the Southern Segment of the Tanlu Fault Zone

“…In the past few decades, FWI has been successfully applied to active‐source ocean‐bottom and streamer datasets to characterize the oceanic crustal structures (e.g., Górszczyk et al., 2017, 2021; Gray et al., 2019; Kamei et al., 2012; Morgan et al., 2016; Operto et al., 2006; Ravaut et al., 2004), and the land datasets to characterize the continental structures (e.g., Bleibinhaus et al., 2007; Morgan et al., 2011). In particular, FWI has also been applied to deep reflection seismic profiles in the study of the upper‐crustal structures (Adamczyk et al., 2015; Li, Gao, et al., 2021; Smithyman & Clowes, 2013; Zhang et al., 2021). Still, the application of FWI to the field data faces considerable difficulties, as FWI is an inverse problem with strong nonlinearity (e.g., Virieux & Operto, 2009) and prone to suffer from ill‐posedness originating from the crosstalk between different parameters.…”