A new tectonic model, postulating the growth of giant subduction-accretion complexes along a single magmatic arc now found contorted between Siberia and Baltica, shows that Asia grew by 5.3 million square kilometres during the Palaeozoic era. Half of this growth may have occurred by the addition of juvenile crust newly extracted from the mantle, supporting models of considerable continental growth continuing throughout the Phanerozoic eon.

Evolution of the Altaid tectonic collage and Palaeozoic crustal growth in Eurasia

The Central Asian Orogenic Belt ( c . 1000–250 Ma) formed by accretion of island arcs, ophiolites, oceanic islands, seamounts, accretionary wedges, oceanic plateaux and microcontinents in a manner comparable with that of circum-Pacific Mesozoic–Cenozoic accretionary orogens. Palaeomagnetic and palaeofloral data indicate that early accretion (Vendian–Ordovician) took place when Baltica and Siberia were separated by a wide ocean. Island arcs and Precambrian microcontinents accreted to the active margins of the two continents or amalgamated in an oceanic setting (as in Kazakhstan) by roll-back and collision, forming a huge accretionary collage. The Palaeo-Asian Ocean closed in the Permian with formation of the Solonker suture. We evaluate contrasting tectonic models for the evolution of the orogenic belt. Current information provides little support for the main tenets of the one- or three-arc Kipchak model; current data suggest that an archipelago-type (Indonesian) model is more viable. Some diagnostic features of ridge–trench interaction are present in the Central Asian orogen (e.g. granites, adakites, boninites, near-trench magmatism, Alaskan-type mafic–ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, rhyolitic ash-fall tuffs). They offer a promising perspective for future investigations.

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Tectonic models for accretion of the Central Asian Orogenic Belt

Paleozoic multiple accretionary and collisional tectonics of the Chinese Tianshan orogenic collage

http://sourcedb.igg.cas.cn/cn/zjrck/200907/W020101130538853730453.pdf

Middle Cambrian to Permian subduction-related accretionary orogenesis of Northern Xinjiang, NW China: Implications for the tectonic evolution of central Asia

This paper deals with the various tectonic units in the Chinese Eastern Tianshan orogenic collage in the Central Asian Orogenic Belt, and discusses the Paleozoic geological history of the several periods of accretion and collision of archipelago systems lying between the Tarim and southern Angaran continental margins. The Late Ordovician-Silurian to Early Devonian Eastern Tianshan archipelago was characterized by (a) the Harlik-Dananhu subduction system with a S-dipping polarity in the north; (b) a southerly N-dipping subduction system beneath the Central Tianshan arc in the middle; and (c) the South Tianshan ocean against Tarim in the south. During the Devonian to Early Carboniferous, N-dipping subduction led to the Harlik-Dananhu arc and the Kanggurtag forearc basin/accretionary complex. In the Early to Mid-Carboniferous, the magmatic front associated with the N-dipping subduction beneath the Dananhu-Harlik arc migrated southwards, forming the Yamansu arc constructed upon the Kanggurtag accretionary forearc. By the Late Carboniferous the Dananhu-Harlik arc was attached northwards to the Angaran margin, resulting in lateral enlargement of the Angaran continent. In the latest Carboniferous to Early Permian a multiple soft collision left wide suture zones in the south that include the ophiolite-strewn Aqikkuduk-Shaquanzi and Kumishi accretion-collision complexes, which were stitched by Early Permian post-collisional plutons. By re-defining and re-interpreting the various tectonic terranes, this paper presents a new, improved model for the Paleozoic evolution of this part of Central Asia.

Paleozoic accretionary and collisional tectonics of the Eastern Tianshan (China): Implications for the continental growth of Central Asia

The Tien Shan Range in central Asia contains two late Paleozoic sutures. The older, southern suture marks the collision of a passive margin at the north of the Tarim block and an active continental margin; subduction under the latter was to the north. The younger, northern suture separates a northern Carboniferous island arc from an active continental margin developed over a south-dipping subduction zone. The subduction direction under the island arc is unknown. Mesozoic elastics were deposited over the doubly sutured orogen. Rate and energy of sedimentation waned until deposition of Oligocene conglomerates above a regional unconformity-interpreted as marking the onset of deformation induced by the India-Asia collision. Molasse deposition accelerated in Pliocene and Quaternary time, and deposition continues today as active thrusts generate relief. Paleozoic structures control the gross divergence of Cenozoic thrusts across the orogen.

Z. Y. Zhao

Papers

Paleozoic accretion and Cenozoic redeformation of the Chinese Tien Shan Range, central Asia