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The Geotectonic Character of SE Asia and Cenozoic Tectonic History of South China Sea
512
Acharyya, S.K. (1998a) Break-up of the Greater Indo-Australian continent and accretion of blocks framing South and East Asia. J. Geodynamics, v.26, pp. 149-170. Acharyya, S.K. (199810) Foreland Palaeogene rocks of the Eastern Himalaya: their basin extension, magmatism and tectonics. In: Proc.Workshop, Himalayan foreland basin with special reference to pre-Siwalik Tertiaries, Jammu Univ., Jammu, March 1998, Wadia Inst.Him.Geol., Abstr., pp. 1-2.
Acharyya, S.K.(1999) India-Asia collision and its relation to deep-seated Paleogene magmatism in Himalayan foreland basin, and around the Gongha syntaxis (submitted to Terra
Nova). Chung Sunlin, Lo, C., Wang, I?, Chen, C., Yem, N.T. and Wu, G. (1997) Intraplate extension prior to continental extrusion along the Ailao Shan-Red River shear zone. Geology, v.25, pp.311-314.
Gondiuana Research, V. 2, No. 4, p p . 512-515. 01999 International Association for Gondwana Research, lapan. ISSN: 1342-937X
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Gondwnrza Research
The Geotectonic Character of SE Asia and Cenozoic Tectonic History of South China Sea Yao Bochu Gtiangzhou Marine Geological Survey, Gziangzhou 510075, China
SE Asia area is one of the tectonically complex areas in the world. It consists of several micro-plates derived from the northern margin of Gondwanaland, including many arcs and accretionary prisms, w h c h finally collided and sutured together through a series of tectonic movements from Paleozoic to Cenozoic. The Indochina block is located in the Northwest margin of the South China Sea. Gatinsky and Hutchson (1986) subdivided it into four micro blocks: Sinnburmalaya, Phu Hoat, Indosinia and East Malay. Hagashi (1989)subdivided it as three micro blocks: Shag Thai, Kan Tum, and South China separated by the NE-SW striking Red River fault zone (Song Ma and Song Da suture zones) and NNE-SSW trending Dien Bien Phu fault zone (Uttaradit suture zone) according to Landsat data (Fig. 1).The Shag Thai and Kan Tum blocks have sutured in the Permian and formed the Indochina block (Bunopas and Vella, 1978; Ridd, 1990). In the Triassic, the Indochina block and South China block have collided and sutured together along the Song Ma and Song Da zone (Hutchson, 1975). The Borneo Island is situated in the southern margin of South China Sea. The Lupar fault zone and its continuation has partly broken the island into two areas: southwest Borneo and north Borneo. The basement of southwest Borneo consists of Paleozoic and Mesozoic igneous rocks,
sedimentary rocks and metamorphic rocks. The oldest rock here is the crystalline schist with an age of 320-201 Ma (Hutchson, 1984, 1986). The north Borneo is a Cenozoic accretionary prism (Jacobson,1970; Lee and Mc Cate, 1986). The Rajang formation (late Cretaceous to early Eocene) is distributed in the southern area, and the Crocker formation (Eocene to Oligocene) is distributed in the northern area (Hall, 1997). The oldest rocks of Palawan Island are schist, phyllite, slate and quartzite. In northeast Palawan, these rocks overlie middle Triassic sandstone, tuff and slate (Hutchson, 1973). In Mindoro, the basement is Triassic schist and slate. The southern part of the Ulugan fault in Palawan island exposes an ophiolite arc, consisting of ophiolite and greenschist (Rangin, 1985; Hutchson, 1975; Faure, 1989). Hinz and Schluter (1985) believe that this ophiolite terrane is an allochthon thrusted from southeast to northwest. The Philippine Islands are constituted of ophiolite and Mesozoic and Tertiary arcs. In the eastern part is the Philippine trench, the Philippine sea plate is subducting westward along this trench. The Philippine Islands is a volcanic arc of the subduction zone. In the western part of the islands, the South China Sea plate is subducting eastward along the Manila trench. Paleomagnetic data show that in the Tertiary, the rotation history of the Philippine
513
30"
N
20"
10"
D"
lo"
fl
Australia
\i
\
20" S
~
100'
110"
12U"
1M"
140"
150"
I
' E
Fig. I. Simplified tectonic map of Southeast Asia. A-Zhongsha-Xisha block. B-Luconia block. C-Nansha block. D-Liyuc-Nortlieast Palawan block. E-Sulawcsi block. F-Halmahera island. G-Bird's Head island. 11-Hainan island. J-Java island. L-Luzon island. N- The fault on tlw western margin of south Cluna Sea. P-Palawan island. T- Taiwan island. LU-Lupar fault. Z- Zhongnan-Liyuc fault. 1-Central basin. 2-Northwest sub-basin. 3-Southwest sub-basin. -I-SUIUsea. 5-Celebes sea. 6-Zengmu basin.
Islands are: 35" in 25-5 Ma period; no rotation in 40-25 Ma period; and 50" in 50-40 Ma period (Hall and Ali, 1995). The geological data indicate that the Philippine Islands were a greenstone belt in Precambrian, and became volcanic arc in the Cenozoic. The Sulawesi consists of four principal tectonic belts: the west Sulawesi volcano-plutonic arc, the central Sulawesi metamorphic belt, the east Sulawesi ophiolite belt, and the continental framents of Banggai-Sula, Tukang Besi and Buton. Paleomagnetic data show that the southwest arm and southeast arm of Sulawesi were located in different positions in Jurassic-Cretaceous (Ka tili, 1978). The west Sulawesi was connected with Malay Peninsula and Borneo in Cretaceous (Fuller et al., 1991). The ophiolite of east Sulawesi originated from Indian ocean (Mubroto, 1994). In the late Oligocene this ophiolite was located in the continental margin of west Sulawesi (Parkinson, 1991).Since early Miocene (25Ma) the southwest Sulawesi and east Sulawesi have collided with west Sulawesi, finally forming the Sulawesi island. The Halmahera island is located northeast cf the Sulawesi. In the eastern part of it is the Philippine trench, the Philippine oceanic plate is subducting westward at depths of about 200-300km. In the western part of it is the Malucca oceanic plate, which is subducting westward at depths of about 600km. In the east of the Halmahera is the ophiolite basement, and in the west is the volcanic arc Gondzuana Research, V. 2,No. 4, 1999
basement. Balanced cross-sections indicate at least 60km east-west shortening between east and west Halmahera in the fold-thrust belt and within the east arms (Hall, 1997). The geological history of the Halmahera island is closely linked with the Philippine oceanic plate. The Bird's Head island had broken up with Australia in Mesozoic. It was a single micro-plate in Oligocene. Before 25Ma time, the Sorong fault occurring in the northern part collided with the southern part of Philippine oceanic plate. The S U ~Sea U is a 600km long and 400km wide basin. It includes Northwest Sulu Basin, Cagayan Ridge and Southeast Sulu Basin. The depth of the water column is 1000-2000m in the Northwest Sulu Basin, and more than 5000m in the Southeast Sulu Basin (Hinz, 1991).ODP data show that in the Southeast Sulu Basin the basement is olivine-phyric basaltic rock (Rangin,l990). The oldest sediment encountered above the basement is a radiolariabearing red clay of late early Miocene age. The basement of the Cagayan Ridge is calc-alkaline basaltic andesite, dacite, and rhyolitic tuff (Kudrass, 1990),overlying lapillistone, tuff and basalt flows of late early Miocene to early middle Miocene age (Rangin, 1990).Therefore, the Cagayan Ridge is interpreted as a continental crust overlying volcanic rock. The sediments are nanofossil marl and clay of middle Miocene to Pliocene age according to the ODP data. Based on regional geological and geophysical data, the South China Sea can be subdivided into South China
5 I4
block, Xisha-Zhongsha block, Nansha block, LiyueNortheast Palawanblock and South China Sea block. In the Jurassic to Cretaceous period the Xisha-Zhongsha block, Nansha block a n d Liyue-Northeast block together constituted an island or islands in the Mesozoic South China Sea basin. The Mesozoic South China Sea was subducted northwestward under the South China block during that time. The volcanic arc was located along the recent Taiwan, Dongsha Islands, Zhongsha Islands and Wanan Bank. In the late Cretaceous the island (or islands) collided with the South China block, and Yanshan movement came to a conclusion. During Cenozoic in South China Sea area, there were three tectonic movements and two seafloor spreading events. The first tectonic movement took place in the late Cretaceous to early Tertiary. This is the Shenhu movement. It originated from the delamination of the Yanshan orogenic belt lithosphere. The NE faults and NE grabens and halfgrabens were produced in this period in the South China Sea area. The second tectonic movement occurred in the late Eocene, termed the Nanhai movement. The Xisha-Zhongsha block and Nansha block moved southeastward and brokeup from South China block. Seafloor spreading occurred, and the NW sub-basm, SW sub-basin and Zenmu basin were produced from late Eocene to early Oligocene (Yao, 1995, 1996). This tectonic movement may relate the collision of Indian plate with Asian plate. The collision caused a major plate reorganization effective not only in Indian ocean but also in southern and Pacific ocean. The plate reorganization in the Indian ocean slowed the convergence rates further, and produced a second phase of extension in South China Sea and East Kalimantan areas. In the late Oligocene the Liyue-Northeast Palawan block broke-up with South China block and moved southward. Seafloor spreading occurred, and the Central basin was produced from late Oligocene to early Miocene (Taylor and Hayes, 1980; 1983). In the late middle Miocene at about 13Ma, the Sulawesiblock collided with the Great Sunda block (Silver, 1991).At about llMa, the Liyue-Northeast Palawanblock collided with S L ~block U (Williams, 1992). These caused the tectonic movement in South China Sea area, and in the northern South China sea, termed Donsha movement or the Wanan movement in the south. We therefore believe that in the marginal basins the seafloor spreading was controlled by the movements of the peripheral continental blocks. Because the movements of the peripheral continental blocks occurred several times, the seafloor spreading in the marginal seas was also multi-stage. For this reason, multi-spreading ridges and multiple seafloor spreading are the characters in the marginal seas.
References Bochu Yao (1995) Tectonic evolution on the southern margin of the South China Sea, CCOP Technical Bull., v.25, pp.143-160.
Bochu Yao (1996) Tectonic evolution of the South China Sea in Cenozoic. Marine Geol. and Quaternary Geol., v. 16, pp. 1-13. Bunopas,S. and Vella,P. (1978) Late Paleozoic and Mesozoic structural evolution of Thailand. In: Nutalaya, P. (Ed.) Proceeding 3'd Regional Conference on Geology a n d Mineral Resources of Southeast Asia. Bangkok, Thailand. Asian Inst. of Tech., pp.133-140. Faure, M. (1989) Pre-Eocene synmetamorphic structure in the Mindoro-Romblon-Palawan arc, west Philippines, a n d implications for the history of Southeast Asia. Tectonics, v. 8, pp. 63-979. Fuller, M., Haston, R. a n d Lin, J-1.(1991) Tertiary paleomagnetism of regions around the South China Sea. J. SE Asian Earth Sci., v. 6, pp.161-184. Gastinky, Y. a n d Hutchson, C. S. (1987) Cathaysia, Gondwanaland and the palaeotethys in the evolution of continental Southeast Asia. Geol. Soc. Malaysia Bull., v. 20, pp. 179-199. Hagashi, M. (1989)The hydrocarbon potential and tectonics of Indochina, Geol. SOC.Malasia B~ill.,v. 25, pp.65-78. Hall, R. (1997) Cenozoic plate tectonics reconstructions of SE Asia In: Fraser, A.J. and Matthews, S. J. (Eds.) Pertroleum Geology of Southeast Asia, Geol. Soc. Sp. Publ., No.126, pp.11-23. Hall, R. and Ah, J.R. (1995) Origin and motion history of the Philippine Sea Plate. Tectonophys., v. 251, pp. 229-250. Hinz, K. (1991)Structural elements of the Sul~iSea, Philippines. Geological Jb., A2 1 ,pp .483-506. Hinz, K. and Schluter, H.U. (1985) Geology of the Dangerous Grounds, South China sea and the continental margin off Southwest Palawan: results of SONNE cruises SO23 and 5027, Energy, v. 10, pp.297-315. Hutchson, C.S. (1973) Tectonic evolution of Sundland: a Phanerozoic synthesis, Geol. Soc. Malasia Bull., v. 6, pp.61-68. Hutchson, C.S. (1975) Ophiolite in Southeast Asia, Geol. Soc. Malasia B~ill., v.8,pp.797-805. Hutchson, C.S. (1984) Is there a satisfactory classification for Southeast Asia Tertiary basin? 5"' Offshore Southeast Asia Proc., SEAPEX, Singapore, v. 6, pp.6-76. Hutchson, C.S. (1986) Formation of marginal seas in Southeast Asia by rifting of the Chinese and Australian continental margin and implications for the Borneo region, GEOSEA V Proc., v.2, Geol. Soc. Malasia B~ill.,v. 20, pp. 201-220. Jacobson, G. (1970) Gunung Kinabalu, Sabah,Malasia, Geol. Suru. Malasia Rept., v. 8, p.111. Katili, J.A. (1978)Past and present geotectonic position of Sulawesi, Indonesia, Tectonophys., v. 45, pp.289-322. Kudrass, H.R. (1990) Volcanic rocks and Tertiary carbonates dredges from the Cagayan Ridge and the southeast Sulu Sea, Philippine-Proc. ODP. Init. Repts., v. 124,pp.93-100. Lee, C.S. and Mc Cate, R. (1986)The Banda-Celebes-Sulu basin: a trapped piece of Cretaceous-Eocene oceanic crust? Nature, V. 322, pp.51-53. Parkinson, C.D. (1991) The petrology, structure and geologic history of the metamorphic rocks of central Sulawesi, Indonesia, P$.D. Thesis, University of London. Rangin,C. (1985)Middle Oligocene oceanic crust of South China Sea jammed into Mindore collision zone (Philippines). Geology, v.13, pp.425-428. Gondwana Research, K 2,No. 4, 1999
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Rangin,C. (1990) Proceedings of the Ocean Drilling Program, Init. Repts. ODP, College Station, TX. p.906. Ridd, M.F. (1990) Possible Palaeozoic drift of SE Asia and Triassic collision with China. J. Geol. SOC.London, v.137, pp.635-640. Silver, E.A. (1991) Leg 124 tectonic synthesis, In: Rangin, C. (Ed.) Proceedings of the Ocean Drilling Program, Scientific Results, v.124, pp.3-9. Taylor, B. and Hayes, D.E. (1980)The tectonic evolution of the South China Basin. In: Hayes, D.E. (Ed.) The tectonic and
geologic evolution of Southeast Asian Seas and Islands, American Geophys. Union Monograph, v. 23, p p . 89-104. Taylor, 8. and Hayes, D.E. (1983) Origin and history of the South China Basin. In: Hayes,D.E. (Ed.)The tectonic and geologic Evolution of Southeast Asian Seas and Islands, Part 2, American Geophys. Union Monograph, v. 27, pp.23-56. Williams, H.H. (1992) Geochemistry of Palawan Oils, Phi 1i p p ines : source imp 1ic a t i o ns . Pro c . 9t'' Offshore Southeast Asia Conf., Singapore, pp.1-4.
Gondzuana Research, V. 2, No. 4, pp. 515-518. 01999 International Association for Gondzuana Rescnrch, japan. ISSN: 1342-937X
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Goizdwarza Research
Precambrian Crustal Evolution in the Central Northern Margin of the Yangtze Block Xie Caifu, Fu Jianming, Xiong Chengyun, Zhang Yeming, Hu Ning and Huang Zhaoxian Yichang Institute of Geology and Mineral Resources, CAGS, PO. Box 502, Yichang, Hzibei 443003, China
Meso-and Neoarchean Initial Crust Archean basement rocks in the studied area are found only in the cores of the Huangling Arch of the Yangtze Gorges area, Hubei and in the Zhaochuan dome fold, Shanxi. They are separately called as the Kongling Complex (lower part) and the Zhuanlugou Complex (Fig.1). The original rocks of these comprise a suite of bimodal volcanics dominated by tholeiite and minor dacite, intercalated with small number of siliceous rocks. The metamorphic grade is high amphibolite to partly granulite facies, with strong nuginatization and a number of TTG plutons. The formation age of these rocks was dated between ca. 2600-ca.3460 Ma (FLIet al., 1993; Zhang W. J. et al., 1996; Ma et al., 1997). Among them the age of TTG intrusive rocks varies between 2800-2900 Ma (Ma et al., 1997).This suite is different from the Archean of North China block in age and rock assemblage. The latter is characterized by the presence of continental crustal rocks of 3500- 3800 Ma and a lot of Neoarchean khondalite series and siliceous iron formations.
Moreover, Pb and Nd isotopic compositions and peak values of Nd model ages reflect the basements in the North China block tobe notably different from those of the Yangtze block (Zhang B. R. et al., 1996; Lu et al., 1996). It is inferred, therefore, that the North China block and Yangtze block might be two landmasses, independently grown during the Archean.
Palaeoproterozoic Continental Crust Accretion Palaeoproterozoic continental crustal rocks, exposed in the Huangling Arch, Dadouling-Xiaodouling, ShangzhouZhengping and Xiaomoling areas, are called the Kongling Complex (upper part), Douling "Lithogroup", Qinling "Lithogroup" and Xiaomoling Complex respectively. They were probably formed in the setting similar to active continental margin following weathering and erosion of the initial Archean salic continental crust and composed of a suite of terrigenous clastic (volcanic) formation, dominated by terrigenous clastic rocks interbedded with
Acharyya, S.K. (1998a) Break-up of the Greater Indo-Australian continent and accretion of blocks framing South and East Asia. J. Geodynamics, v.26, pp. 149-170. Acharyya, S.K. (199810) Foreland Palaeogene rocks of the Eastern Himalaya: their basin extension, magmatism and tectonics. In: Proc.Workshop, Himalayan foreland basin with special reference to pre-Siwalik Tertiaries, Jammu Univ., Jammu, March 1998, Wadia Inst.Him.Geol., Abstr., pp. 1-2.
Acharyya, S.K.(1999) India-Asia collision and its relation to deep-seated Paleogene magmatism in Himalayan foreland basin, and around the Gongha syntaxis (submitted to Terra
Nova). Chung Sunlin, Lo, C., Wang, I?, Chen, C., Yem, N.T. and Wu, G. (1997) Intraplate extension prior to continental extrusion along the Ailao Shan-Red River shear zone. Geology, v.25, pp.311-314.
Gondiuana Research, V. 2, No. 4, p p . 512-515. 01999 International Association for Gondwana Research, lapan. ISSN: 1342-937X
GR
Gondwnrza Research
The Geotectonic Character of SE Asia and Cenozoic Tectonic History of South China Sea Yao Bochu Gtiangzhou Marine Geological Survey, Gziangzhou 510075, China
SE Asia area is one of the tectonically complex areas in the world. It consists of several micro-plates derived from the northern margin of Gondwanaland, including many arcs and accretionary prisms, w h c h finally collided and sutured together through a series of tectonic movements from Paleozoic to Cenozoic. The Indochina block is located in the Northwest margin of the South China Sea. Gatinsky and Hutchson (1986) subdivided it into four micro blocks: Sinnburmalaya, Phu Hoat, Indosinia and East Malay. Hagashi (1989)subdivided it as three micro blocks: Shag Thai, Kan Tum, and South China separated by the NE-SW striking Red River fault zone (Song Ma and Song Da suture zones) and NNE-SSW trending Dien Bien Phu fault zone (Uttaradit suture zone) according to Landsat data (Fig. 1).The Shag Thai and Kan Tum blocks have sutured in the Permian and formed the Indochina block (Bunopas and Vella, 1978; Ridd, 1990). In the Triassic, the Indochina block and South China block have collided and sutured together along the Song Ma and Song Da zone (Hutchson, 1975). The Borneo Island is situated in the southern margin of South China Sea. The Lupar fault zone and its continuation has partly broken the island into two areas: southwest Borneo and north Borneo. The basement of southwest Borneo consists of Paleozoic and Mesozoic igneous rocks,
sedimentary rocks and metamorphic rocks. The oldest rock here is the crystalline schist with an age of 320-201 Ma (Hutchson, 1984, 1986). The north Borneo is a Cenozoic accretionary prism (Jacobson,1970; Lee and Mc Cate, 1986). The Rajang formation (late Cretaceous to early Eocene) is distributed in the southern area, and the Crocker formation (Eocene to Oligocene) is distributed in the northern area (Hall, 1997). The oldest rocks of Palawan Island are schist, phyllite, slate and quartzite. In northeast Palawan, these rocks overlie middle Triassic sandstone, tuff and slate (Hutchson, 1973). In Mindoro, the basement is Triassic schist and slate. The southern part of the Ulugan fault in Palawan island exposes an ophiolite arc, consisting of ophiolite and greenschist (Rangin, 1985; Hutchson, 1975; Faure, 1989). Hinz and Schluter (1985) believe that this ophiolite terrane is an allochthon thrusted from southeast to northwest. The Philippine Islands are constituted of ophiolite and Mesozoic and Tertiary arcs. In the eastern part is the Philippine trench, the Philippine sea plate is subducting westward along this trench. The Philippine Islands is a volcanic arc of the subduction zone. In the western part of the islands, the South China Sea plate is subducting eastward along the Manila trench. Paleomagnetic data show that in the Tertiary, the rotation history of the Philippine
513
30"
N
20"
10"
D"
lo"
fl
Australia
\i
\
20" S
~
100'
110"
12U"
1M"
140"
150"
I
' E
Fig. I. Simplified tectonic map of Southeast Asia. A-Zhongsha-Xisha block. B-Luconia block. C-Nansha block. D-Liyuc-Nortlieast Palawan block. E-Sulawcsi block. F-Halmahera island. G-Bird's Head island. 11-Hainan island. J-Java island. L-Luzon island. N- The fault on tlw western margin of south Cluna Sea. P-Palawan island. T- Taiwan island. LU-Lupar fault. Z- Zhongnan-Liyuc fault. 1-Central basin. 2-Northwest sub-basin. 3-Southwest sub-basin. -I-SUIUsea. 5-Celebes sea. 6-Zengmu basin.
Islands are: 35" in 25-5 Ma period; no rotation in 40-25 Ma period; and 50" in 50-40 Ma period (Hall and Ali, 1995). The geological data indicate that the Philippine Islands were a greenstone belt in Precambrian, and became volcanic arc in the Cenozoic. The Sulawesi consists of four principal tectonic belts: the west Sulawesi volcano-plutonic arc, the central Sulawesi metamorphic belt, the east Sulawesi ophiolite belt, and the continental framents of Banggai-Sula, Tukang Besi and Buton. Paleomagnetic data show that the southwest arm and southeast arm of Sulawesi were located in different positions in Jurassic-Cretaceous (Ka tili, 1978). The west Sulawesi was connected with Malay Peninsula and Borneo in Cretaceous (Fuller et al., 1991). The ophiolite of east Sulawesi originated from Indian ocean (Mubroto, 1994). In the late Oligocene this ophiolite was located in the continental margin of west Sulawesi (Parkinson, 1991).Since early Miocene (25Ma) the southwest Sulawesi and east Sulawesi have collided with west Sulawesi, finally forming the Sulawesi island. The Halmahera island is located northeast cf the Sulawesi. In the eastern part of it is the Philippine trench, the Philippine oceanic plate is subducting westward at depths of about 200-300km. In the western part of it is the Malucca oceanic plate, which is subducting westward at depths of about 600km. In the east of the Halmahera is the ophiolite basement, and in the west is the volcanic arc Gondzuana Research, V. 2,No. 4, 1999
basement. Balanced cross-sections indicate at least 60km east-west shortening between east and west Halmahera in the fold-thrust belt and within the east arms (Hall, 1997). The geological history of the Halmahera island is closely linked with the Philippine oceanic plate. The Bird's Head island had broken up with Australia in Mesozoic. It was a single micro-plate in Oligocene. Before 25Ma time, the Sorong fault occurring in the northern part collided with the southern part of Philippine oceanic plate. The S U ~Sea U is a 600km long and 400km wide basin. It includes Northwest Sulu Basin, Cagayan Ridge and Southeast Sulu Basin. The depth of the water column is 1000-2000m in the Northwest Sulu Basin, and more than 5000m in the Southeast Sulu Basin (Hinz, 1991).ODP data show that in the Southeast Sulu Basin the basement is olivine-phyric basaltic rock (Rangin,l990). The oldest sediment encountered above the basement is a radiolariabearing red clay of late early Miocene age. The basement of the Cagayan Ridge is calc-alkaline basaltic andesite, dacite, and rhyolitic tuff (Kudrass, 1990),overlying lapillistone, tuff and basalt flows of late early Miocene to early middle Miocene age (Rangin, 1990).Therefore, the Cagayan Ridge is interpreted as a continental crust overlying volcanic rock. The sediments are nanofossil marl and clay of middle Miocene to Pliocene age according to the ODP data. Based on regional geological and geophysical data, the South China Sea can be subdivided into South China
5 I4
block, Xisha-Zhongsha block, Nansha block, LiyueNortheast Palawanblock and South China Sea block. In the Jurassic to Cretaceous period the Xisha-Zhongsha block, Nansha block a n d Liyue-Northeast block together constituted an island or islands in the Mesozoic South China Sea basin. The Mesozoic South China Sea was subducted northwestward under the South China block during that time. The volcanic arc was located along the recent Taiwan, Dongsha Islands, Zhongsha Islands and Wanan Bank. In the late Cretaceous the island (or islands) collided with the South China block, and Yanshan movement came to a conclusion. During Cenozoic in South China Sea area, there were three tectonic movements and two seafloor spreading events. The first tectonic movement took place in the late Cretaceous to early Tertiary. This is the Shenhu movement. It originated from the delamination of the Yanshan orogenic belt lithosphere. The NE faults and NE grabens and halfgrabens were produced in this period in the South China Sea area. The second tectonic movement occurred in the late Eocene, termed the Nanhai movement. The Xisha-Zhongsha block and Nansha block moved southeastward and brokeup from South China block. Seafloor spreading occurred, and the NW sub-basm, SW sub-basin and Zenmu basin were produced from late Eocene to early Oligocene (Yao, 1995, 1996). This tectonic movement may relate the collision of Indian plate with Asian plate. The collision caused a major plate reorganization effective not only in Indian ocean but also in southern and Pacific ocean. The plate reorganization in the Indian ocean slowed the convergence rates further, and produced a second phase of extension in South China Sea and East Kalimantan areas. In the late Oligocene the Liyue-Northeast Palawan block broke-up with South China block and moved southward. Seafloor spreading occurred, and the Central basin was produced from late Oligocene to early Miocene (Taylor and Hayes, 1980; 1983). In the late middle Miocene at about 13Ma, the Sulawesiblock collided with the Great Sunda block (Silver, 1991).At about llMa, the Liyue-Northeast Palawanblock collided with S L ~block U (Williams, 1992). These caused the tectonic movement in South China Sea area, and in the northern South China sea, termed Donsha movement or the Wanan movement in the south. We therefore believe that in the marginal basins the seafloor spreading was controlled by the movements of the peripheral continental blocks. Because the movements of the peripheral continental blocks occurred several times, the seafloor spreading in the marginal seas was also multi-stage. For this reason, multi-spreading ridges and multiple seafloor spreading are the characters in the marginal seas.
References Bochu Yao (1995) Tectonic evolution on the southern margin of the South China Sea, CCOP Technical Bull., v.25, pp.143-160.
Bochu Yao (1996) Tectonic evolution of the South China Sea in Cenozoic. Marine Geol. and Quaternary Geol., v. 16, pp. 1-13. Bunopas,S. and Vella,P. (1978) Late Paleozoic and Mesozoic structural evolution of Thailand. In: Nutalaya, P. (Ed.) Proceeding 3'd Regional Conference on Geology a n d Mineral Resources of Southeast Asia. Bangkok, Thailand. Asian Inst. of Tech., pp.133-140. Faure, M. (1989) Pre-Eocene synmetamorphic structure in the Mindoro-Romblon-Palawan arc, west Philippines, a n d implications for the history of Southeast Asia. Tectonics, v. 8, pp. 63-979. Fuller, M., Haston, R. a n d Lin, J-1.(1991) Tertiary paleomagnetism of regions around the South China Sea. J. SE Asian Earth Sci., v. 6, pp.161-184. Gastinky, Y. a n d Hutchson, C. S. (1987) Cathaysia, Gondwanaland and the palaeotethys in the evolution of continental Southeast Asia. Geol. Soc. Malaysia Bull., v. 20, pp. 179-199. Hagashi, M. (1989)The hydrocarbon potential and tectonics of Indochina, Geol. SOC.Malasia B~ill.,v. 25, pp.65-78. Hall, R. (1997) Cenozoic plate tectonics reconstructions of SE Asia In: Fraser, A.J. and Matthews, S. J. (Eds.) Pertroleum Geology of Southeast Asia, Geol. Soc. Sp. Publ., No.126, pp.11-23. Hall, R. and Ah, J.R. (1995) Origin and motion history of the Philippine Sea Plate. Tectonophys., v. 251, pp. 229-250. Hinz, K. (1991)Structural elements of the Sul~iSea, Philippines. Geological Jb., A2 1 ,pp .483-506. Hinz, K. and Schluter, H.U. (1985) Geology of the Dangerous Grounds, South China sea and the continental margin off Southwest Palawan: results of SONNE cruises SO23 and 5027, Energy, v. 10, pp.297-315. Hutchson, C.S. (1973) Tectonic evolution of Sundland: a Phanerozoic synthesis, Geol. Soc. Malasia Bull., v. 6, pp.61-68. Hutchson, C.S. (1975) Ophiolite in Southeast Asia, Geol. Soc. Malasia B~ill., v.8,pp.797-805. Hutchson, C.S. (1984) Is there a satisfactory classification for Southeast Asia Tertiary basin? 5"' Offshore Southeast Asia Proc., SEAPEX, Singapore, v. 6, pp.6-76. Hutchson, C.S. (1986) Formation of marginal seas in Southeast Asia by rifting of the Chinese and Australian continental margin and implications for the Borneo region, GEOSEA V Proc., v.2, Geol. Soc. Malasia B~ill.,v. 20, pp. 201-220. Jacobson, G. (1970) Gunung Kinabalu, Sabah,Malasia, Geol. Suru. Malasia Rept., v. 8, p.111. Katili, J.A. (1978)Past and present geotectonic position of Sulawesi, Indonesia, Tectonophys., v. 45, pp.289-322. Kudrass, H.R. (1990) Volcanic rocks and Tertiary carbonates dredges from the Cagayan Ridge and the southeast Sulu Sea, Philippine-Proc. ODP. Init. Repts., v. 124,pp.93-100. Lee, C.S. and Mc Cate, R. (1986)The Banda-Celebes-Sulu basin: a trapped piece of Cretaceous-Eocene oceanic crust? Nature, V. 322, pp.51-53. Parkinson, C.D. (1991) The petrology, structure and geologic history of the metamorphic rocks of central Sulawesi, Indonesia, P$.D. Thesis, University of London. Rangin,C. (1985)Middle Oligocene oceanic crust of South China Sea jammed into Mindore collision zone (Philippines). Geology, v.13, pp.425-428. Gondwana Research, K 2,No. 4, 1999
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geologic evolution of Southeast Asian Seas and Islands, American Geophys. Union Monograph, v. 23, p p . 89-104. Taylor, 8. and Hayes, D.E. (1983) Origin and history of the South China Basin. In: Hayes,D.E. (Ed.)The tectonic and geologic Evolution of Southeast Asian Seas and Islands, Part 2, American Geophys. Union Monograph, v. 27, pp.23-56. Williams, H.H. (1992) Geochemistry of Palawan Oils, Phi 1i p p ines : source imp 1ic a t i o ns . Pro c . 9t'' Offshore Southeast Asia Conf., Singapore, pp.1-4.
Gondzuana Research, V. 2, No. 4, pp. 515-518. 01999 International Association for Gondzuana Rescnrch, japan. ISSN: 1342-937X
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Goizdwarza Research
Precambrian Crustal Evolution in the Central Northern Margin of the Yangtze Block Xie Caifu, Fu Jianming, Xiong Chengyun, Zhang Yeming, Hu Ning and Huang Zhaoxian Yichang Institute of Geology and Mineral Resources, CAGS, PO. Box 502, Yichang, Hzibei 443003, China
Meso-and Neoarchean Initial Crust Archean basement rocks in the studied area are found only in the cores of the Huangling Arch of the Yangtze Gorges area, Hubei and in the Zhaochuan dome fold, Shanxi. They are separately called as the Kongling Complex (lower part) and the Zhuanlugou Complex (Fig.1). The original rocks of these comprise a suite of bimodal volcanics dominated by tholeiite and minor dacite, intercalated with small number of siliceous rocks. The metamorphic grade is high amphibolite to partly granulite facies, with strong nuginatization and a number of TTG plutons. The formation age of these rocks was dated between ca. 2600-ca.3460 Ma (FLIet al., 1993; Zhang W. J. et al., 1996; Ma et al., 1997). Among them the age of TTG intrusive rocks varies between 2800-2900 Ma (Ma et al., 1997).This suite is different from the Archean of North China block in age and rock assemblage. The latter is characterized by the presence of continental crustal rocks of 3500- 3800 Ma and a lot of Neoarchean khondalite series and siliceous iron formations.
Moreover, Pb and Nd isotopic compositions and peak values of Nd model ages reflect the basements in the North China block tobe notably different from those of the Yangtze block (Zhang B. R. et al., 1996; Lu et al., 1996). It is inferred, therefore, that the North China block and Yangtze block might be two landmasses, independently grown during the Archean.
Palaeoproterozoic Continental Crust Accretion Palaeoproterozoic continental crustal rocks, exposed in the Huangling Arch, Dadouling-Xiaodouling, ShangzhouZhengping and Xiaomoling areas, are called the Kongling Complex (upper part), Douling "Lithogroup", Qinling "Lithogroup" and Xiaomoling Complex respectively. They were probably formed in the setting similar to active continental margin following weathering and erosion of the initial Archean salic continental crust and composed of a suite of terrigenous clastic (volcanic) formation, dominated by terrigenous clastic rocks interbedded with