Preface to the Special Issue on Gas Hydrate Research around the South China Sea and Taiwan

Abstract

Gas hydrates are naturally occurring crystalline substances, in which a solid water lattice holds gas molecules in a cage-like structure. They have attracted much attention as an alternative energy resource potential, and may impact the global environment through generating slope instability. Consequently, much research utilizing different approaches has been carried out recently for better understanding the origin and characteristics of gas hydrates. Bottom simulating reflector (BSR) is a strong indicator of gas hydrate presence and extensive BSRs have been clearly observed in many parts of the continental margins around the South China Sea, especially in SW offshore Taiwan. Since 2004, the Central Geological Survey (CGS) of the Ministry of Economic Affairs (MOEA) has launched a 4-year gas hydrate investigation program that includes geological investigation, geochemical exploration, geophysical survey, and data bank establishment. Some important and exciting results have been found during the early stages of this investigation. In order to share the findings and to better develop the gas hydrate investigation program in Taiwan, an international workshop and a cross-Strait conference on gas hydrates were held in Taipei and Tainan in November 2004 and January 2005, respectively. After these successful and fruitful conferences, we invited colleagues to submit their updated results to this journal for a special issue reporting on the most recent progress in gas hydrate studies for the region. A total of twenty-two representative contributions have been included in this special issue after passing through a regular peer review process. They are divided into four groups: (1) the general geology and characteristics of gas hydrates around the South China Sea region; (2) the results of geophysical investigations in the South China Sea and East China Sea; (3) the geochemical investigations in this region; and (4) some important findings regarding physical properties of potential gas hydrate bearing samples. In the first group of six papers, Liu et al. (2006) describe the distribution and characters of gas hydrate offshore of SW Taiwan based on seismic data, and find that intensive BSRs can be recognized in both active and passive margins. They also briefly report on current progress in the integrated project for gas hydrate exploration supported by the CGS. From the newly collected geophysical and geologic data, Yan et al. (2006) demonstrate the occurrences of gas hydrates in the continental margins of the northeastern South China Sea near Dongsha Island. Yu and Huang (2006) discuss sedimentary processes through seismic facies analyses and recognize three intraslope basins in the area off SW Taiwan, which they consider to be the result of interactions between regional contraction tectonics, local mud diapirism and foreland sedimentation. Huang et al. (2006) report the occurrence of pogonophoran tube worms, elongated pyrites and authigenic carbonate nodules in the Kaoping Slope, and evaluate the occurrences of potential cold seeps in the syn-collision accretionary prism off SW Taiwan. They suggest that there are active cold seeps with methane expulsions in the area. Numerous mud volcanoes and gassy sediments have been identified in both the passive and active margins