文章题目：Understanding the Recent and Future Mechanical Evolution of the SongPan Ganzi—Qaidam NE Tibet Moho-Offset
文章摘要：Present-day seismic imaging, reveals crustal thickness varying from about 70 km under SongPan-Ganzi (SG) to about 50 km under Qaidam basin (QB) terranes in NE Tibet. This vertical Moho offset occurs over horizontal spans of less than 20 km, and is somehow confirmed by gravimetric and electromagnetic observations. Paleotectonic and litho-stratigraphic reconstructions suggest that the region amalgamates at least three microcontinents, but current geophysical observations reveal basically two distinct microplates (SG and QB). We conduct 2D Stokes' flow numerical simulations to understand the mechanical evolution of the SG-QB contact, focusing our attention on Moho-offset kinematics. We find that in the absence of tectonic horizontal motions, generic systems with a Moho offset of the sort, are unstable in timescales of about ∼3 Ma, solely due to the effect of vertical driving-forces (gravity-driven relaxation given topographic- or Moho-gradients). Then, an observation-controlled parameter setting (seismically derived densities, locally accepted viscosities and layer thicknesses, and considering a potentially likely QB litho-mantle weakening by SG-derived melts) suggests that added tectonic horizontal convergence (GPS constraints on Tibetan deformations) to the previous scenario, tends to dominate the internal velocity field and deformation. Topography-driven SG-lower-crustal flow may inject a small amount of mass into QB. The Moho-offset changes significantly in timescales of about ∼5–10 Ma; an initially vertical Moho-offset, aside from a reference-frame-dependent translation, differentially deforms (stretches) and rotates (becoming oblique), smoothing-out the terranes' crustal-thickness transition. Through time, accumulated Moho-offset rotation and smoothing are somewhat smaller when there is tectonic horizontal shortening. The left-lateral Kunlun-suture motion might rejuvenate the Moho-offset through time.
引用信息：Orellana-Rovirosa, F., & Shi, Y. (2021). Understanding the recent and future mechanical evolution of the SongPan Ganzi—Qaidam NE Tibet Moho-offset. Journal of Geophysical Research: Solid Earth, 126, e2021JB022128.
