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Due to the collision and lateral compression of the Indian-Asian plate, the Lancangjiang fault has become one of the most active strike-slip faults in the Qiangtang plate. The Qamdo 2013 Ms 6.1 earthquake was induced from the northern section of the fault (the northern Lancangjiang fault). The destruction of the earthquake seriously endangers human activities and the construction of the Sichuan-Tibet Railway. However, there are few high-resolution geophysical data in this area, which limits the understanding of the deep structure, motion mode and seismic activity of the northern Lancangjiang active fault. In this paper, new gravity data were observed at a scale of 1: 200,000, covering an area of 1500km2. Based on wavelet multiscale decomposition, scratch analysis and 3-D inversion of gravity data methods, we obtained gravity anomalies of different scales, faults distribution and density structure. The results show that the overall crustal density change in Qamdo area is obvious and closely related to the distribution of faults. The Qamdo earthquake occurred at the layered interface with steep density change and the result from scratch analysis shows that the stress is concentrated at this position. We believe that the existence of stratigraphic density difference leads to different ability of strata to withstand regional tectonic stress, which is an important cause of the Qamdo earthquake. We analyzed the differences magnitude of earthquake activity between the northern Lancangjiang fault and Kamaduo-Gangtuo fault and believe that the northern Lancangjiang fault is more conducive to the preparation of large earthquakes. Otherwise, this paper provides geophysical evidence for the hypothesis that the northern Lancangjiang fault thrusts to the Qamdo Basin at a high angle. • Crustal density change in the Qamdo is more complex. • Crustal density characteristics are linked to distribution of faults. • The northern Lancangjiang fault thrusts into the Qamdo Basin at a high angle. • The northern Lancangjiang fault is conducive to the preparation of large earthquakes. • The Qamdo earthquake occurred at the layered interface with steep density change. [ABSTRACT FROM AUTHOR]

Schematic representation of Isostatic balance between source and sink distribution of sediments and tectonics. [Display omitted] • The NSCSM evolved and linked with successive uplifts in SE Tibet Plateau. • Deep and surface parameters isostatically influence sediments and control their geometry. • Strengthening of lithosphere at the continental margin isostatically balanced with inland exhumation. Tectonic processes of the SE Tibet Plateau (SETP) and the northern South China Sea margin (NSCSM) strongly affected the surface drainage system for sediment transportation to deposition. It remains challenging to investigate the dominant mechanisms such as tectonics, deep dynamics, and surface processes. This paper aims to examine the influence of the SETP paleogeography on the NSCSM. Twenty-eight seismic profiles were quantified by flexurally interpolated backstripping and significantly correlated with the published paleogeography. A numerical simulation tool (Badlands) is assigned to study the integrated response of surface processes and deep dynamics. This paper inferred that drastic sedimentation changes in our models were linearly correlated mainly with erosion during the SETP uplifts, dynamic topography, and flexural isostasy. Deep dynamics and tectonic processes control basin architectures for sediment depositions, whereas the surface processes contribute isostatically in response to uplifts in the source region. We inferred that Eocene was the stage of extension, thinning of lithosphere (Te = 10 km) that is linked with the low topography (<2000 m) and erodibility (Є) of 5e-7 in the SETP. However, the increase in cumulative thickness is associated with strengthening the lithosphere (Te = 15 km) and tributary rotation with its rise in SETP topography (≥4000 m) during the Oligocene to Early Miocene. The Middle Miocene doesn't have the source-sink linkage for its high SETP topography with low deposition. But a strong connection with paleogeographic evolution in the later stage due to the rise in SETP topography and Taiwan orogeny. [ABSTRACT FROM AUTHOR]

This paper reviews the spatial-temporal distribution, geological and geochemical features, and geophysical context of diverse types of Cenozoic ore deposits formed during India-Eurasia continental collision in Tibet, in order to shed new light on their genesis and their control by mantle lithosphere. The parental magmas for porphyry-skarn Cu (± Mo ± Au) deposits were derived from metal-rich pre-Cenozoic juvenile crust, and the high magma oxidation state was controlled by involved mantle-derived basic magmas and thickened crust condition; magma emplacement was controlled by structures related both to tears in the subducting continental slab to deep and to mantle-crust decoupling parts at depth. Orogenic Au deposits mostly formed intermittently from hydrothermal fluids formed by devolatilization of earlier-fertilized mantle lithosphere that was triggered by asthenosphere upwelling; they were largely controlled by lithosphere-scale shear systems that reactivated earlier-formed suture zones. Giant MVT Zn Pb deposits, hosted by ancient oil reservoirs, formed during salt diapirism and infiltration of metal-rich basinal brines related to crustal-scale channel flow. The diverse range of ore deposits was derived predominantly through release of metal and fluid components, introduced into the crust and mantle lithosphere that occurred in the earlier oceanic subduction during anomalous lithosphere-scale deformation. The metallogenic history of collisional orogens contrasts with those of accretionary orogens. • Tibetan mineralization system provides an important global insight into metallogenesis during continental collision. • Lithosphere architecture and fertility formed by oceanic subduction control diverse ore deposits in collision setting. • Diverse types of Tibetan ore deposits have different genesis to those from oceanic subduction settings. • Tibetan ore deposits formed in various geodynamic settings of thrusting, shearing, rotation, and rifting. [ABSTRACT FROM AUTHOR]

Exploring magmatic 'flare-up' events can be used to unravel dynamic Earth processes including plate subduction and crustal growth. However, the cause and mechanism of magmatic 'flare-up' remain unresolved. The abundant magmatic records that are preserved in the Lhasa Terrane on the southern Tibetan Plateau make it an important region to study the episodic nature of the secular magmatism. This paper presents geochronological, mineralogical, and geochemical data that describes the Dazhuka diorites in the central-western and Sangri granites in the eastern parts of the southern Lhasa Terrane. Zircon LA–ICP–MS U Pb data indicate that these rocks were generated around ~95–90 Ma. Both are enriched in large ion lithophile elements and depleted in high field strength elements, indicating geochemical affinity with subduction-related magmatic rocks. The Dazhuka diorites have low SiO 2 contents (54.49–56.72 wt%), with moderate Mg# (41.7–42.7) and rare earth element fractionation ((La/Yb) N = 6.9–8.6), and homogeneous whole-rock 87Sr/86Sr i (0.704204–0.704480), ε Nd (t) (+3.5 − +4.1), and zircon ε Hf (t) (+10.2 − +13.3). These features suggest that the Dazhuka diorites originated in the spinel-garnet transition zone within the lithospheric mantle of a mantle wedge environment. The Sangri granites have high SiO 2 (64.36–69.54 wt%), Al 2 O 3 (14.27–15.61 wt%), and (La/Yb) N (4.6–49.6) and Sr/Y (34.7–119.3) ratios, indicating geochemical affinity with adakites. Low MgO (1.3–2.22 wt%) and depleted Sr-Nd-Hf isotopes (whole-rock 87Sr/86Sr i = 0.704099–0.705453, ε Nd (t) = +2.9 − +3.5, zircon ε Hf (t) = +7.1 − +9.3) suggest that the granites were derived from oceanic crust. The types of magmatic rocks that are distributed over the central-western and the eastern parts of the southern Lhasa Terrane differ, with higher magmatic temperatures in the east as compared to the central-west. These results indicate that different areas in the southern Lhasa Terrane may have experienced different geodynamic processes, with oceanic ridge subduction in the eastern part of the southern Lhasa Terrane and normal oceanic plate subduction in the central-western part. These different types of subduction processes are likely to have caused the magmatic 'flare-up' and variation in the magmatism of southern Tibet. [Display omitted] • Both Dazhuka diorites and Sangri granites formed in early Late Cretaceous. • Dazhuka diorites were derived from the lithospheric mantle. • Sangri granites with adakitic affinity were sourced from the oceanic crust. • Multiply Neo-Tethys Ocean plate subduction processes result in magmatic 'flare-up'. [ABSTRACT FROM AUTHOR]

The history of crustal thickening is critical for comprehending the evolution process of the Tibetan plateau. The genetic relationship and spatiotemporal distribution of adakitic rocks with high Sr/Y, (La/Yb) N ratios may impose fundamental constraints on specific geodynamic and crustal thickening processes. The Songka intrusive suite consists of adakitic rocks with high-Mg adakite (monzonites), low-Mg adakitic rocks (quartz monzonites), and gabbroic-diorites. Their geochemical characteristics, petrogenesis, and geodynamic implication is discussed in this paper. Songka high-Mg adakites formed when subducting Neo-Tethyan oceanic slab melts were assimilated by mantle peridotite at elevated temperatures (average Ti-in-zircon temperatures of sample SK1319 are 830 °C). Low-Mg adakitic rocks exhibit markedly different geochemical characteristics than those formed in the juvenile thickened lower crust. The least-squares mass balance and trace element simulations indicate that Songka low-Mg adakitic samples were formed at a degree of 60–65% fractional crystallization of melts resembling Songka high-Mg adakites. Songka gabbroic diorites are formed in the metasomatic mantle wedge. The genetic relationship between these rocks indicates that the crust of the southern Tibet did not appear to thicken obviously during the early stage of late Cretaceous (100–90 Ma). The intensive emplacement of late Cretaceous high-Mg adakites (Mg# > 50) and mafic rocks (SiO 2 < 52%) in the southern Lhasa terrane around 95–90 Ma, together with the slow convergence velocity of the Indian-Asian continent, can be explained by the response of rapid crustal thickening and Neo-Tethyan slab rollback at 95–90 Ma. • High-Mg adakitic rocks were formed from partial melting of Neo-Tethyan slab. • Coeval low-Mg adakitic rocks were produced by fractional crystallization. • Rapid crustal growth and Neo-Tethyan slab rollback occurred at 95–90 Ma. [ABSTRACT FROM AUTHOR]

[Display omitted] • The first identified oceanic core complex in the Bangong-Nujiang suture zone. • The mid-ocean ridge of the Meso-Tethys Ocean moved northward since the Late Triassic. • This ridge was slow spreading during the Early Jurassic. In this paper, we report the first identified oceanic core complex (OCC) in the Saibucuo area of the Bangong-Nujiang suture zone, describe the geology and petrology of this OCC, and present new zircon U-Pb ages and Lu-Hf isotopes, and whole-rock major- and trace-elements and Sr-Nd isotopes for the diabase dikes in this OCC. The Saibucuo OCC consists of serpentinites, serpentinized peridotites, diabase dikes, tectonic breccias, sedimentary breccias, and limestones. The serpentinized peridotites cross-cut by carbonate veins, the sedimentary breccias with simple gravel compositions cut by normal faults, together with the limestones in the cover sequence lead to the conclusion that the Saibucuo OCC is similar to the OCCs of mid-ocean ridge settings. This conclusion is consistent with the E-MORB features of diabase dikes, which are formed by the interaction of the mid-ocean ridge and mantle plume, and the abyssal peridotite features of serpentinized peridotites. Zircon U–Pb ages of the diabase dikes indicate that the Saibucuo OCC was formed at the ca. 190 Ma. Based on these data and regional geological records, the early Mesozoic tectonic evolution of the Meso-Tethys Ocean was restored. The Meso-Tethys Ocean was a broad and mature oceanic basin during the Late Triassic-Early Jurassic. Coeval collision of the Northern and Southern Qiangtang terranes during the Late Triassic initiated the northward subduction of the Meso-Tethys Ocean, and the northward migration of the mid-ocean ridge. Continuous northward subduction of the Meso-Tethys Ocean caused the mid-ocean ridge to gradually approach the northward subduction zone, and eventually to subduct and collide with the northern trench during the Early-Middle Jurassic. The mid-ocean ridge within the Meso-Tethys Ocean was slow spreading during the Early Jurassic. [ABSTRACT FROM AUTHOR]