Evolution Of South China Research Articles

Numerical modeling of the formation of Indo-Sinian peraluminous granitoids in Hunan Province: Basaltic underplating versus tectonic thickening

The genesis of Indo-Sinian granitic plutons with peraluminous and potassium-rich affinities from Hunan Province, China has been investigated by numerical modeling using the numerical code FLAC. On the basis of the regional geological evolution in South China, we employed a realistic numerical model in an attempt to unravel the influences of basaltic underplating and tectonic crustal thickening on the crustal anatexis. Heat production derived from basaltic underplating (e.g. ca. 220 Ma gabbro xenoliths) can result in dehydration melting of fluid-bearing minerals in crustal rocks such as gneisses and metapelites, but its effect is limited in a relatively short time span (5- 15 Ma) and on a small scale. Accordingly, it is very difficult for basaltic underplating to generate the large-scale Indo-Sinian granitic bathliths unless voluminous mafic magmas had been underplated at the lowerlmiddle crust during this period. Alternatively, crustal thickening induced by tectonic compression can also lead to geothermal elevation, during which the temperature at the boundary between lower and middle crusts can be up to or greater than 700°C, triggering dehydration melting of muscovite in gneiss and metapelite. The proportion of melts from muscovite-induced dehydration melting is close to critical melt percentage (220%) once the thickening factor reaches 1.3. These melts can be effectively transferred to the crust-level magma chamber and form large-scale granitic batholiths. In combination with the Indo-Sinian convergent tectonic setting in South China as well as sparse outcrops of contemporary mafic igneous rocks, we consider that tectonic crustal thickening is likely to be the predominant factor controlling the formation of the Indo-Sinian peraluminous and potassium-rich granitoids in Hunan Province.

Main tectonic units and geological evolution in South China and its environs: in the light of Gondwana dispersion and Asian accretion : Geniao Y. Wu, ed I. Metcalfe, (A.A. Balkema), Gondwana dispersion and Asian accretion. IGCP 321 final results volume, ISBN 9054104465, 1999, (315–340)

Main tectonic units and geological evolution in South China and its environs: in the light of Gondwana dispersion and Asian accretion : Geniao Y. Wu, ed I. Metcalfe, (A.A. Balkema), Gondwana dispersion and Asian accretion. IGCP 321 final results volume, ISBN 9054104465, 1999, (315–340)

The pre-Devonian tectonic patterns and evolution of South China

A northwest-dipping subduction zone was located at the southeastern flank of the Jiangnan island arc during the middle to late Proterozoic. The collision of the Northwest Fujian continental terrane with the ancient active continental margin of the Yangtze Plate during the Xuefengian movement led to the eastward jumping of the subduction zone. A newly formed northwest-dipping subduction zone during the Sinian-early Paleozoic time was situated on the Shangyu-Zhenghe-Dapu-Lufeng fractural zone to the southeast of the Northwest Fujian terrane. A volcanic island arc, the Zhejuang-Fujian-Guangdong Sinian-early Paleozoic volcanic island arc, was formed on the basement of the Northwest Fujian terrane. In the vast area between this arc and the remnant Jiangnan arc, a series of complexly distributed remnant arcs, interarc basins and remnant back arc marginal basins were formed. After the middle Ordovician the East Zhejiang terrane collided with the Zhejiang-Fujian-Guangdong island arc causing the development of a melange complex in the northwestward thrusting obduction zone along the fractural zone. By the end of the Silurian a wide fold-fault belt was formed and most back arc basins were closed except for a few of them which remained as Upper Paleozoic inherent basins.

Palaeovegetation and plate tectonics: palaeophytogeography of North China during permian and triassic times

New evidence concerning the palaeovegetation of the upper Permian and lower Triassic Shischienfeng Group in North China reveals two distinctive floras: a Zechstein-type vegetation in the lower part and a Buntsandstein-type flora in the middle and upper parts. The traditional concept that North China is a component of the Cathaysian floral province does not match with the newly confirmed palaeophytostratigraphical sequence from the early Permian Autunian-Saxonian flora passing via the Zechstein and the Buntsandstein vegetations to the late Triassic Keuper flora in North China corresponding to the sequence in Western Europe. The sequence reveals that the former northern Cathaysian Province is thus to be considerably revised, with North China now being assigned to the Euramerican Province rather than to the Cathaysian Province during late Palaeozoic and early Mesozoic times. The Eurasian Arid Province is suggested to comprise a specific scene of the Euramerican Province from the late Permian to the early Triassic. The so-called “Cathaysian floras” in North China represent a mixed association of Euramerican elements with some Cathaysian components, reflecting an origin when the South China Plate drifted north-ward and collided temporarily and repeatedly with the North China Plate during the late Palaeozoci time. The evolution of South China and North China is briefly summarized in the light of the concept of continental drift.