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2019. American Geophysical Union. All Rights Reserved. The compositions and ages of the sediments within retro or foreland basins that are formed and preserved adjacent to collisional orogens can reflect the nature of colliding tectonic elements. The nonmarine Yaoshuiquan and Huabaoshan formations in the South Qilian belt on the NE Tibetan Plateau deposited within a retro-foreland basin setting during latest Ordovician to Late Silurian time in response to arc-continent collision. Detritus derivation from a Cambro-Ordovician arc-ophiolite complex contains mixed 530-480 Ma oceanic-crust together with contributions from a 479-450 Ma continental-arc early in development of the basin. The Cambrian arc-accretionary system and Central Qilian block united to form the basement of a continental arc at ~450 Ma, and both then contributed sediments to the Lianhuashan-Huabaoshan basin. After the Hualong complex accreted to the north, a broad Andean-type margin developed along the southern margin of the Central Qilian block from 450 to 440 Ma. These processes generated a wider basin that received detritus from both the south and the north. Consumption of the Proto-Tethyan Ocean ended with collision between the Qaidam and Hualong blocks, which led to mass wasting of detritus from the Andean-type igneous rocks and both blocks with the basin from 440 to 420 Ma.

The Lajishan ophiolite complex in the Qilian Orogen is one of several ophiolites situated between the Qaidam and North China blocks that record episodic closure of the Proto-Tethyan Ocean. Detailed field relations and geochemical and geochronological studies are critical to unraveling the tectonic processes responsible for an extensive period of intraoceanic subduction that produced juvenile ophiolite/island arc terranes, which were obducted onto continental margins during ocean closure. The Lajishankou ophiolite complex crops out along the northern margin of the South Qilian belt and was thrust over a Neoproterozoic-Ordovician passive margin sequence that was deposited upon the Proterozoic Central Qilian block. The mafic rocks in Lajishankou ophiolite complex are the most abundant slices and can be categorized into three distinct groups based on petrological, geochemical, and geochronological characteristics: massive island arc tholeiites, 509-Ma back-arc dolerite dykes, and 491-Ma pillow basaltic and dolerite slices that are of seamount origin in a back-arc basin. These results, together with spatial relationships, indicate that the Cambrian island arc rocks, ophiolite complex, and accretionary complex developed between 530 and 480 Ma as a single, intraoceanic arc-basin system as a result of south directed subduction of the Proto-Tethyan Ocean prior to Early Ordovician obduction of this system onto the Central Qilian block. Final continental amalgamation involved continental collision of the Central Qilian block with the Qaidam block during the Late Ordovician. This model solves the long-lasting discussion on the emplacement of the Lajishan ophiolite and contributes to an improved understanding of multiple accretionary and collisional processes in the Qilian Orogen.

The Lajishan ophiolite complex in the Qilian Orogen is one of several ophiolites situated between the Qaidam and North China blocks that record episodic closure of the Proto-Tethyan Ocean. Detailed field relations and geochemical and geochronological studies are critical to unraveling the tectonic processes responsible for an extensive period of intraoceanic subduction that produced juvenile ophiolite/island arc terranes, which were obducted onto continental margins during ocean closure. The Lajishankou ophiolite complex crops out along the northern margin of the South Qilian belt and was thrust over a Neoproterozoic-Ordovician passive margin sequence that was deposited upon the Proterozoic Central Qilian block. The mafic rocks in Lajishankou ophiolite complex are the most abundant slices and can be categorized into three distinct groups based on petrological, geochemical, and geochronological characteristics: massive island arc tholeiites, 509-Ma back-arc dolerite dykes, and 491-Ma pillow basaltic and dolerite slices that are of seamount origin in a back-arc basin. These results, together with spatial relationships, indicate that the Cambrian island arc rocks, ophiolite complex, and accretionary complex developed between 530 and 480 Ma as a single, intraoceanic arc-basin system as a result of south directed subduction of the Proto-Tethyan Ocean prior to Early Ordovician obduction of this system onto the Central Qilian block. Final continental amalgamation involved continental collision of the Central Qilian block with the Qaidam block during the Late Ordovician. This model solves the long-lasting discussion on the emplacement of the Lajishan ophiolite and contributes to an improved understanding of multiple accretionary and collisional processes in the Qilian Orogen.

A combination of published data and preliminary research results are used to describe geological features and the distribution in time and space of important mineral deposits in the Tibetan orogenic belt, as well as their geodynamic settings, mineral environments and key genetic processes. A working model of metallogeny in the orogen is proposed. The Indo-Asian continental collision resulted in three significant tectonic units that controlled the development of ore deposits: the main collisional deformation zone, the south Tibet detachment-thrust zone and the east Tibet tectonic transformation zone. Processes of mineralisation can be divided into three ore-forming supersystems: collision and subduction since the Palaeocene that resulted in Au-Sb-Cu and Sn-rare metal systems; strike-slip and shearing that gave rise to Ag-Pb-Zn-Cu and porphyry Cu-Au systems; and mid-Miocene post-collisional extension that controlled the localisation of Cu-bearing porphyries and formed epithermal and hot-spring Au-Sb deposits., A combination of published data and preliminary research results are used to describe geological features and the distribution in time and space of important mineral deposits in the Tibetan orogenic belt, as well as their geodynamic settings, mineral environments and key genetic processes. A working model of metallogeny in the orogen is proposed. The Indo-Asian continental collision resulted in three significant tectonic units that controlled the development of ore deposits: the main collisional deformation zone, the south Tibet detachment-thrust zone and the east Tibet tectonic transformation zone. Processes of mineralisation can be divided into three ore-forming supersystems: collision and subduction since the Palaeocene that resulted in Au-Sb-Cu and Sn-rare metal systems; strike-slip and shearing that gave rise to Ag-Pb-Zn-Cu and porphyry Cu-Au systems; and mid-Miocene post-collisional extension that controlled the localisation of Cu-bearing porphyries and formed epithermal and hot-spring Au-Sb deposits.