臺灣東部海域花東盆地的地質特征：位于歐亞板塊和太平洋板塊之間的新特提斯洋殘余?

臺灣東部海域花東盆地的地質特征：位于歐亞板塊和太平洋板塊之間的新特提斯洋殘余?

The Huatung Basin (20°30’-23°30’N/121°30’-123°E; maximum water depth: 5500 m) locates east off Taiwan. It is bordered by the Coastal Range of Taiwan and the North Luzon Arc to the west, the West Philippine Sea to the east and the Ryukyu Trench to the north. The Huatung Basin was previously regarded as a part of the Cenozoic Philippine Sea Plate (<50 Ma). However, Ar40/Ar39dating on amphibole in two dredged gabbro samples retrieved from the southern part of the Huatung Basin indicated that the Basin was early Cretaceous in age(115-121 Ma; Deschamps et al., 2000). This age is further supported by an independent micropaleontology study on some red chert xenoliths containing Early Cretaceous radiolarian fossils (115 Ma; Yeh and Cheng, 2001) in the Late Pleistocene volcanic sequences of the Lanyu Volcanic Island of the North Luzon Arc. The North Luzon Volcanic Arc was formed during the eastward subduction of the South China Sea oceanic lithosphere beneath the Huatung Basin since middle Miocene. Accordingly, the Miocene Luzon volcanic arc is sitting on the Cretaceous oceanic crust of the Huatung Basin.

The Huatung Basin separates from the West Philippine Sea Basin along the N-S-trending Gauga Ridge. The origin of this oceanic ridge is still not clear.However, the triangle-shaped Huatung Basin disappears when the NW-SE-trending North Luzon Arc merges with the N-S-trending Gauga Ridge south of 20°N. The latter two geological units furthermore connect southward to the Sierra Madrea (Eocene -Oligocene volcanic sequences east of Cagayan back-arc rifting basin) and the Cretaceous SSZ Isabela ophiolite in NE Luzon Island.

This study raises some fundamental issues that need further study including deep-sea drilling in near future: 1) Does the Huatung Basin represent a relic part of the Neo-Tethys Ocean between the Eurasian Continent and the Pacific Plate? 2) More marine surveys over the Huatung Basin including geophysical investigations and age dating on in situ oceanic crust and mantle rocks of the Huatung Basin and the Gauga Ridge to understand the tectonic relationship between Huatung Basin and the Philippine Sea plate; 3) Was the Proto-South China Sea a part of the Neo-Tethys Ocean? 4) Is there any tectonic continuity between the Sierra Madrea –Isabela ophiolite of the eastern Luzon Island and the Huatung Basin?

E-mail: huangcy@mail.ncku.edu.tw.

Geological Significance of the Huatung Basin East off Taiwan:A Relic Neo-Tethys Ocean between the Eurasian Plate and the Modern Pacific Plate?

Chi-yue HUANG1,2)
1)Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences,Guangzhou, China;
2)Department of earth Sciences, National Cheng Kung University, Tainan, China

Huatung Basin; Neo-Tethys; tectonics

10.3975/cagsb.2012.s1.12