This paper is the result of the mineral exploration engineering.
Objective There are increasing evidences show that the Tethys tectonic domain can be divided into three stages of the ProtoTethys, the Paleo- Tethys and the Neo- Tethys, among which the research on the formation and evolution of the Paleo- Tethys Ocean and related mineralization are relatively weak.
Methods On the basis of the discovery of the Early Devonian Xiarihamu super-large nickel-cobalt sulfide deposit in the East Kunlun, the Late Carboniferous Malkansu large volcanic source sedimentary type manganese-rich deposit in the Pamir and the late Triassic Dahongliutan large pegmatite type lithium-beryllium deposit in the West Kunlun, this study focuses on the formation environment and tectonic evolution as the main line to find out their connection. It is proposed that the three large ore deposits represent the products of the tectonic transformation of Paleo- Tethys break, ocean expansion and ocean closure to continental collision, respectively.
Results It is believed that after the closure of the Proto-Tethys ocean and continental collision, which was contemporaneous with the Paleo-Asian ocean at the end of the Silurian, the modified asthenosphere was partially melted and the northern margin of Gondwana continent breakup due to the mantle plume activity, forming the Xiarihamu super-large magmatic nickel-cobalt sulfide deposit related to the mantle-derived mafic-ultramafic rocks. With the further expansion of the Paleo- Tethys Ocean, the mature ocean was formed in the Early Carboniferous. In the Late Carboniferous, with transformation from rapid expansion to ocean subduction, the Malkansu large rhodochrosite-rich deposit was formed in the carbonate sedimentary of the ocean floor due to the ore forming material provided by the eruption of the mid-ocean ridge. After the closure of the Paleo-Tethys Ocean, it entered the collision orogenic stage in the Middle Triassic. In the Late Triassic post- collisional stage, high temperature hydrothermal fluid of S- type granite formed by the crust remelting, which lead to the formation of Dahongliutan large pegmatite-type lithium-beryllium deposit. The Early Paleozoic and Late Paleozoic alternation was the beginning of the Paleo- Tethys Ocean breakup. At this time the Qinling- Qilian- Kunlun Ocean as the representative of the Proto-Tethys Ocean has closed. Although the Paleo-Asian Ocean as a back-arc basin of the Proto-Tethys has not closed yet, the Xiarihamu nickel-cobalt deposit is the product of the re-cracking of continental crust after the Proto-Tethys orogeny, and it' s not formed in the environment of the Proto - Tethys island arc or post- collision. Manganese is a lithophilic element, which is not enriched in magmatism. However, it enriched in exogenous deposition, which indicates that the new oceanic crust of the Early Carboniferous of Paleo-Tethys is rich in manganese, and the leached manganese ions formed sedimentary manganese carbonate in the alkaline environment of relatively quiet ocean floor in the Late Carboniferous, which represents the transition from a strong magmatism stage to a relatively quiet sedimentary environment. In the Dahongliutan, the distribution of S-type granitic batholith and its large-scale pegmatite-type lithium-beryllium ore deposit reflect the geodynamic background of crust remelting caused by strong collisional orogeny. Therefore, it' s suggested the formation environment is post-orogeny or post-collision extension of the Paleo- Tethys.
Conclusions As far as the existing facts of mineralization concerned, the Kangxiwa- Animaqing Paleo- Tethys suture zone in East Kunlun is of more geological significance than that of the Xijinwulan-Jinshajajiang in the southern Bayankara and the Longmuco-Shuanghu Paleo-Tethys suture zone in the Qiangtang.
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