Neoproterozoic tectonic evolution and proto-basin of the Yangtze Block, China

Abstract

The Neoproterozoic assembly and break-up of Rodinia have not only caused reconfiguration of the global tectonic architecture of oceans and continents, but also led to active tectonic processes and basin fillings which consequently effected the Earth's habitability. The Yangtze Block preserves abundant Neoproterozoic magmatic rocks along its edges and sedimentary successions in the inner shield for reconstruction of the tectonic evolution of Rodinia. The Rodinia landmasses were surrounded by the exterior Pan-ocean and separated by the interior oceans during the latest Mesoproterozoic (ca. 1.17–1.02 Ga). The Yangtze Block was situated at the northwestern edge of Rodinia, facing the exterior ocean to the north and west, and evolved into a Neoproterozoic co-evolution of coupling inner basins and three marginal orogens. The Jiangnan Orogen in the east was formed by long-term subduction-collision between the Yangtze and Cathaysia blocks from ca. 1000–820 Ma, and represents an interior orogen corresponding to the assembly of Rodinia. In comparison, the Longmen-Kangdian Orogen was an Andean-type subduction orogen along the western active continental margin from ca. 870–720 Ma, while the South Qinling Orogen was a wide accretionary orogen to the north of the nucleus of the Yangtze Block from ca. 880–720 Ma. Both the Longmen-Kangdian Orogen in the west and the South Qinling Orogen in the north were exterior orogens of Rodinia. The exterior subductions from ca. 880 to 820 Ma were synchronous with the assembly of Rodinia; however, the continuous exterior subductions along the western and northern Yangtze Block (the outer part of Rodinia) during ca. 820–720 Ma might have coincided with the break-up of Rodinia. The different spatiotemporal properties of sedimentary fillings and the evolution of the inner Yangtze basin were controlled by the Neoproterozoic tectonic evolution of the three orogens. From ca. 1000–880 Ma, the exterior ocean was undergoing extension, resulting in passive continental marginal deposition, while the interior Paleo-South China oceanic slab subducted beneath the E-Yangtze Block, leading to an arc-related continental marginal basin. Up to ca. 880–820 Ma, the westward interior subduction-collision generated the closure of the Paleo-South China interior ocean, leading to the collision of the Yangtze and Cathaysia blocks at ca. 820 Ma. The southward and eastward exterior subductions from ca. 820 to 720 Ma led to a wide accretionary continental marginal orogen in the South Qinling Belt and an Andean-type active continental arc along the Longmen-Kangdian Belt. The continuous exterior subduction along the W- and N-Yangtze Block, together with the collapse of Jiangnan Orogen, led to the interior rifting in the inner Yangtze Basin filled with a thick-pile of rift-related successions. From ca. 720–635 Ma, the W-Yangtze Block transmitted to a westward-deepening passive continental margin, while the E-Yangtze Block was still in rift basins. Most areas of the Yangtze Block have evolved into an extensional basin, which accumulated with widespread glacial-interglacial deposits. Afterwards, the whole Yangtze Block evolved into a depressional basin filled with the Ediacaran and Cambrian shallow-marine or bathyal-abyssal facies clastic and carbonate successions.