Xin et al. (2019) presented 3D seismic velocity models (VP and VS) of crust and uppermost mantle of continental China using seismic body-wave travel-time tomography, which are referred to as Unified Seismic Tomography Models for Continental China Lithosphere 1.0 (USTClitho1.0). Compared with previous models of continental China, the VP and VS models of USTClitho1.0 have the highest spatial resolution of 0.5°–1.0° in the horizontal direction and are useful for better understanding the complex tectonics of continental China. Although USTClitho1.0 is implicitly constrained by surface-wave data by using the VS model from surface-wave tomography and the converted VP model as initial models for body-wave travel-time tomography, the predicted surface-wave dispersion curves from USTClitho1.0 do not fit the observed data well. Here, we present updated 3D VP and VS models of the continental China lithosphere (USTClitho2.0) by joint inversion of body-wave arrival times and surface-wave dispersion data. Compared with the previous joint inversion scheme of Zhang et al. (2014), similar to Fang et al. (2016), it is further improved by including the sensitivity of surface-wave dispersion data to VP in the new joint inversion system. As a result, the shallow VP structure is also better imaged. In addition, the new joint inversion scheme considers the large topography variations between the eastern and western parts of China. Thus, USTClitho2.0 better resolves the upper-crustal structure of the Tibetan plateau. Compared with USTClitho1.0, USTClitho2.0 fits both body-wave arrival times and surface-wave dispersion data. Thus, the new velocity models are more accurate and can serve as a better reference model for regional-scale tomography and geodynamic studies in continental China.

In order to better understand the petrological characteristics of gasification residues and trace element partitioning during entrained-flow gasification processes, oil-immersion microscopy, X-ray diffraction, scanning electron microscopy combined with an energy dispersive detector, inductively coupled plasma mass spectrometry, a Milestone DMA-80 Hg analyzer, and pyrohydrolysis in conjunction with a fluorine ion-selective electrode were employed to study samples collected from three commercial-scale slagging entrained-flow gasifiers in Ningdong, China. Petrological analysis indicated that dominant organic components in the residues were inertiods, fusinoids, tenuinetworks, and crassisnetworks. In addition, vitroplast and cenosphere were observed in coarse residues produced from water–slurry coal gasification. The main inorganic components were quartz, calcite, spinel, and a large amount of Al–Si glass. After gasification, most trace elements were significantly enriched in the residues. Critical trace elements Li, Be, Sc, V, Cr, Sr, REEs, Th, Nb, Ta, Zr, and Hf were enriched in the coarse residues. Critical trace elements Zn, Sb, Pb, and Bi were enriched in the fine residues, which was in accord with volatilization–condensation mechanism. The partitioning of trace elements was elucidated on the basis of their relative enrichment. Fluorine showed various partitioning behavior in three gasification processes. Mercury was the most volatile element. Generally, trace elements from the GE gasification process were less volatile; elements from the opposed four-burner gasification were more volatile; and the volatile behavior of trace elements from the Gaskombimat Schwarze Pumpe gasifier was intermediate.

This study, via combined analysis of geophysical and geochemical data, reveals a lithospheric architecture characterized by crust-mantle decoupling and vertical heat-flow conduits that control orogenic gold mineralization in the Ailaoshan gold belt on the southeastern margin of Tibet. The mantle seismic tomography indicates that the crust-mantle decoupled deformation, defined from previous seismic anisotropy analysis was formed by upwelling and lateral flow of the asthenosphere driven by deep subduction of the Indian continent. Our MT and seismic images show both a vertical conductor across the Moho and high Vp/Vs anomalies both in the uppermost mantle and lowest crust, suggesting that crust-mantle decoupling promotes ponding of mantle-derived basic melts at the base of the crust via a heat-flow conduit. Noble gas isotope and halogen ratios of gold-related ore minerals indicate a mantle source of ore fluid, and a rapid decrease in Cl/F ratios of lamprophyres under P-T conditions of 1.2 Gpa and 1050 C suggests that the ore fluid was derived from degassing of the basic melts. Similar lithospheric architecture is recognized in other orogenic gold provinces, implying analogous formational controls.

The current lithospheric root of the South China Block has been partly removed, yet what mechanisms modified the lithospheric structure remain highly controversial. Here we use a new joint seismic inversion algorithm to image tabular high-velocity anomalies at depths of ~90–150 km in the asthenosphere beneath the convergent belt between the Yangtze and Cathaysia blocks that remain weakly connected with the stable Yangtze lithosphere. Based on obtained seismic images and available geochemical data, we interpret these detached fast anomalies as partially destabilized lower lithosphere that initially delaminated at 180–170 Ma and has relaminated to their original position after warming up in the mantle by now. We conclude that delamination is the most plausible mechanism for the lithospheric modification and the formation of a Mesozoic Basin and Range-style magmatic province in South China by triggering adiabatic upwelling of the asthenosphere and consequent lithospheric extension and extensive melting of the overlying crust.

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