Early Paleozoic Tethyan evolution and metallogeny in East Asia

Abstract

In order to reconstruct the tectonic and metallogenic evolution of the Proto-Tethys tectonic domain, this study presents a comprehensive review of geological, geochemical, and high-precision geochronological datasets of ophiolites, magmatic rocks, metamorphic rocks and ore deposits from the Cambrian to Early Devonian periods, within various tectonic units influenced by the Proto-Tethys Ocean in East Asia. These units include the South China Block, the Central China Orogenic Belt (CCOB), the Qiangtang Block, and the Sanjiang orogenic belt. Our analysis leads to the following main conclusions. (1) There are differences in the subduction patterns of the Proto-Tethys Ocean. On the northwestern side, dextral-oblique subduction of the Proto-Tethys Ocean led to the collision of ribbon continents (“K-Qubed”) with the North China-Tarim continent. At the same time, on the southeastern side of the Proto-Tethys Ocean, oceanic subduction (locally bidirectional) led to the Northern Qiangtang, Indochina and South China blocks (excluding the East Cathaysia Block) moving towards the Gondwana continent, with localized collisions. (2) Branches of the Proto-Tethys Ocean underwent closure during the Early Paleozoic, while other oceans, such as the ocean to the south of the CCOB and the Longmu Co-Shuanghu-Changning-Menglian Ocean, were continuous into the Late Paleozoic, and are regarded as parts of Paleo-Tethys. (3) In the Proto-Tethys tectonic domain, the source of W-mineralized granitoids was primarily composed of ancient crust rich in W, whereas the magmatic source region of Cu-mineralized granitoids contained a significant amount of juvenile crust rich in Cu. (4) A four-stage paleogeographic and metallogenic evolution model is proposed for the Proto-Tethys tectonic domain in East Asia. From 580 to 530 Ma, continental blocks and slivers were scattered throughout the Proto-Tethys Ocean with limited magmatic activity and localized oceanic subduction. From 530 to 450 Ma, subduction occurred in various branches of the Proto-Tethys Ocean, leading to the formation of numerous VMS (Volcanogenic Massive Sulfide), Sedex (Sedimentary Exhalative), and BIF (Banded Iron Formation) type deposits in island arc or back-arc settings. From 450 and 430 Ma, continental collision and convergence occurred, transitioning from oceanic subduction to continental collision, followed by post-collisional extension, leading to numerous granite-related deposits. From 430 to 380 Ma, the tectonic domain was primarily in a post-collision extensional setting resulting in the formation of an array of granite-related deposits, orogenic gold deposits, MVT-type (Mississippi Valley type) Pb-Zn deposits, VMS-type deposits, and magmatic Ni-Co deposits.