Yangtze Plate
The Yangtze plate, sometimes referred to as the South China plate, is located in Southeast China. It is a part of the Eaurasian Plate and is bounded to the East by the Okinawa, Sunda, Amur, and Philippine plates (see figure 1). The Yangtze plate moves at a relatively slow rate of 13 mm/a to the SSE relative to the Eurasian plate (Euler pole 61.2 o N, 142 o E, 0.206 o /Ma) (Bird, 2003). Currently, most boundaries of the Yangtze are either divergent, convergent, or lateral. There are no subducting plates in contact with the Yangtze. There is a sinistral transform fault between the Amurian that slips 4 mm/a, and another significant sinistral transpressive fault that slips 15 mm/a along the Sunda (Bird, 2003).
The formation of the Yangtze plate dates back to the neoproterozoic (750 million years ago), when it separated from the supercontinent Rodinia (Chenzao et al., 2012). Recent Theory suggests that three different blocks merged together to create the plate we see today, these blocks were the Yangtze block, the Lower Yangtze Block, and the Cathaysia block (He and al., 2013) (see figure 2).
The Blocks were close to equator latitude during the Permian, and reached latitudes of 10o to 30o in the Triassic. This was when the collision with the North China plate formed the Sichuan basin (Enos, et al., 2006), which is a lowland that currently contains a fairly sizeable hydrocarbon gas field due to rock failure (Sun, 1997). More recently, in the Cenozoic, the Indian and the Yangtze plate collaborated in forming several orogenies including that of the Longmen Mountains.
On the Yangtze plate itself seismic events are relatively infrequent. The only area where earthquakes of significance occur is on the convergent boundary touching the Philippine Plate. The largest recorded earthquake in this area was magnitude 7.3 back in 1917. The lack of seismic activity on Yangtze can perhaps be attributed to the rigidity of the underlying craton (Bird, 2003).
Volcanism is also mostly absent. The few volcanoes in the area are all located right off the coast of present day Taiwan; they are there due to the Phillipine Plate subducting under the Okinawa Plate.
An interesting structural observation is that there is a lot of folding in the southern part of the plate, but only weak deformations in the northern area of the plate. This had to do with a contrast in the old crystalline basement of the plate dating back to the mesoproerozoic. This means that the overall structural rigidity of the Yangtze Plate increases towards the north. The structural rigidity of the Yangtze is very similar to that of the Amurian Plate (He and al., 2013).
Although not very seismically active the Yangtze Plate did contribute to the creation of faults in other parts of Eurasia. The Yangtze and Indian plates ploughed into the Eurasian Plate and contributed to Seismicity by opening up many faults, most notably the Longmen Shan fault (on the Eurasian plate), which in 2008 was responsible for the magnitude 8.0 Earthquake in the Sichuan area.
On the Yangtze plate itself seismic events are relatively infrequent. The only area where earthquakes of significance occur is on the convergent boundary touching the Philippine Plate. The largest recorded earthquake in this area was magnitude 7.3 back in 1917. The lack of seismic activity on Yangtze can perhaps be attributed to the rigidity of the underlying craton (Bird, 2003).
Volcanism is also mostly absent. The few volcanoes in the area are all located right off the coast of present day Taiwan; they are there due to the Phillipine Plate subducting under the Okinawa Plate.
An interesting structural observation is that there is a lot of folding in the southern part of the plate, but only weak deformations in the northern area of the plate. This had to do with a contrast in the old crystalline basement of the plate dating back to the mesoproerozoic. This means that the overall structural rigidity of the Yangtze Plate increases towards the north. The structural rigidity of the Yangtze is very similar to that of the Amurian Plate (He and al., 2013).
Although not very seismically active the Yangtze Plate did contribute to the creation of faults in other parts of Eurasia. The Yangtze and Indian plates ploughed into the Eurasian Plate and contributed to Seismicity by opening up many faults, most notably the Longmen Shan fault (on the Eurasian plate), which in 2008 was responsible for the magnitude 8.0 Earthquake in the Sichuan area.
References
Bird, P., An updated digital model of plate boundaries, Geochemistry Geophysics Geosystems, Volume 4 number 3, 2003.
Chenzao, J., Characteristics of Chinese Petroleum Geology, Zhejiang University Press, 2012
Enos, P., Lehrmann, D. J., Wei, J., Yu, Y., et al., Triassic Evolution of the Yangtze Platform in Guizhou Province, People’s Republic of China, The Geological Society of America, special paper 417, 2006.
Z. Sun, T. Wang, D. Ye, and G. Song, Geology and Hydrocarbon Occurrence of Tertiary Striki-Slip Basin in Eastern Tibet and Western Sichuan, Geology of Fossil Fuels-Volume 18 part A, pp.347-350, 30th International Geological Congress, 1997.
W. Tianfeng, The Tectonics of China, Springer, 2010
C. He, S. Dong, M. Santosh, and X. Chen, Seismic Evidence for a Geosuture between the Yangtze and Cathaysia Blocks, South China, article number 2200, Nature, 2013.
Bird, P., An updated digital model of plate boundaries, Geochemistry Geophysics Geosystems, Volume 4 number 3, 2003.
Chenzao, J., Characteristics of Chinese Petroleum Geology, Zhejiang University Press, 2012
Enos, P., Lehrmann, D. J., Wei, J., Yu, Y., et al., Triassic Evolution of the Yangtze Platform in Guizhou Province, People’s Republic of China, The Geological Society of America, special paper 417, 2006.
Z. Sun, T. Wang, D. Ye, and G. Song, Geology and Hydrocarbon Occurrence of Tertiary Striki-Slip Basin in Eastern Tibet and Western Sichuan, Geology of Fossil Fuels-Volume 18 part A, pp.347-350, 30th International Geological Congress, 1997.
W. Tianfeng, The Tectonics of China, Springer, 2010
C. He, S. Dong, M. Santosh, and X. Chen, Seismic Evidence for a Geosuture between the Yangtze and Cathaysia Blocks, South China, article number 2200, Nature, 2013.
Eric G.