Composition and exhalation flux of gases from mud volcanoes in Taiwan

Yang, T. F.; Yeh, Gao-Hua; Fu, Ching‐Chou; Wang, Chengchen; Lan, Tefang; Lee, Hsiao-Fen; Chen, Cheng-Hong; Walia, Vivek; Sung, Quo-Cheng

doi:10.1007/s00254-004-1086-0

Cited by 105 publications

(88 citation statements)

References 16 publications

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“…Muddy fluids emitted from active mud diapirs form mud volcanoes on the seafloor Chiu et al 2006). Most of the diapiric ridges trend in NNE-SSW direction, parallel to the structural trend of the folds and thrust faults and mud volcanoes on land Taiwan (Yang et al 2004), and many diapiric ridges connect to anticlinal structures on land SW Taiwan (Huang 1995;Chuang 2006). …”

Section: Structural Charactersmentioning

confidence: 99%

Distribution and Characters of Gas Hydrate Offshore of Southwestern Taiwan

Liu¹,

Schnürle²,

Wang³

et al. 2006

Terr. Atmos. Ocean. Sci.

149

108

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ABSTRACT1 Institute of Oceanography, National Taiwan University, Taipei, Taiwan, ROC 2 Central Geologic Survey, Taipei, Taiwan, ROC 3 Exploration Department, Chinese Petroleum Company, Miaoli, Taiwan, ROC * Corresponding author address: Prof. Char-Shine Liu, Institute of Oceanography, National Taiwan University, Taipei, Taiwan, ROC; E-mail: csliu@ntu.edu.tw Bottom simulating reflector (BSR) is a key indicator for the presence of gas hydrate beneath the sea floor. Widely distributed BSRs have been observed in the area offshore of southwestern Taiwan where the active accretionary complex meets with the passive China continental margin. In order to better understand the distribution and characters of the gas hydrate in the region, closely spaced (1.86-km line spacing) multichannel seismic reflection surveys have been conducted in recent years under the support of the Central Geological Survey, ROC. Over 10000 km of multichannel seismic reflection profiles have been collected that cover an area of about 10000 km 2 offshore of southwestern Taiwan. BSRs can be identified along 50% of the seismic profiles that we collected. A newly compiled BSR distribution map suggests that gas hydrates are distributed both in the passive margin of the China continental slope as well as in the submarine Taiwan accretionary wedge, from water depths of 500 to over 3000 m. Gas hydrates are most concentrated underneath anticlinal ridges in the accretionary wedge, and underneath the slope ridges of the passive continental margin that were formed due to sedimentary processes. Active fluid activities are evident from various features observed on seismic reflection and chirp sonar profiles, such as mud volcanoes, gas plumes and gas charged shallow sedimentary layers. Fluid migration model has been established from a set of pseudo 3D seismic reflection data. The predicted locations of high fluid Terr. Atmos. Ocean. Sci., Vol. 17, No. 4, December 2006 616 flux correlate well with those interpreted from geochemical analyses that show very high methane concentrations and very shallow sulfate-methane interfaces (SMI). This demonstrates the importance of structural control over gas hydrate emplacement. From the observed gas hydrate distribution and characters, the area offshore of southwestern Taiwan provides an ideal place to study and compare the formation and migration of gas hydrates under different tectonic settings.

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Section: Structural Charactersmentioning

confidence: 99%

Distribution and Characters of Gas Hydrate Offshore of Southwestern Taiwan

Liu¹,

Schnürle²,

Wang³

et al. 2006

Terr. Atmos. Ocean. Sci.

149

108

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“…This may explain the presence of submarine mud volcanoes in offshore southwestern Taiwan (e.g., Chou et al 2000;Chiu et al 2006), which have been considered to be related to on-land mud volcanoes (Yang et al 2003(Yang et al , 2004 by Yeh (2003). Moreover, these methane-rich fluids influence the composition of pore water and bottom seawater around these gas-expelling craters.…”

Section: Introductionmentioning

confidence: 99%

Extremely High Methane Concentration in Bottom Water and Cored Sediments from Offshore Southwestern Taiwan

Chuang¹,

Yang²,

Lin³

et al. 2006

Terr. Atmos. Ocean. Sci.

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ABSTRACT1 Department of Geosciences, National Taiwan University, Taipei, Taiwan, ROC 2 Institute of Oceanography, National Taiwan University, Taipei, Taiwan, ROC 3 Central Geological Survey, MOEA, Taipei, Taiwan, ROC * Corresponding author address: Prof. Tsanyao Frank Yang, Department of Geosciences, National Taiwan University, Taipei, Taiwan, ROC; E-mail: tyyang@ntu.edu.tw It has been found that Bottom Simulating Reflections (BSRs), which infer the existence of potential gas hydrates underneath seafloor sediments, are widely distributed in offshore southwestern Taiwan. Fluids and gases derived from dissociation of gas hydrates, which are typically methane enriched, affect the composition of seawater and sediments near venting areas. Hence, methane concentration of seawater and sediments become useful proxies for exploration of potential gas hydrates in a given area. We systematically collected bottom waters and sedimentary core samples for dissolved and pore-space gas analyses through five cruises: ORI-697, ORI-718, ORII-1207, ORII-1230, and ORI-732 from 2003 to 2005 in this study. Some sites with extremely high methane concentrations have been found in offshore southwestern Taiwan, e.g., sites G23 of ORI-697, N8 of ORI-718, and G96 of ORI-732. The methane concentrations of cored sediments display an increasing trend with depth. Furthermore, the down-core profiles of methane and sulfate reveal very shallow depths of sulfate methane interface (SMI) at some sites in this study. It implies sulfate reduction being mainly driven by the process of anaerobic methane oxidation (AMO) in sediments; thus indicating that there is a methane-enriched venting source, which may be the product of dissociation of gas hydrates in this area.

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“…Numerous mud volcanoes and diapiric intrusion have been found along tectonic structures both on-shore and offshore of southwestern Taiwan (e.g., Chow et al 2000;Yang et al 2004;Chiu et al 2006). The gases vented from on-shore mud volcanoes are dominated by methane (Yang et al 2004) and exhibit mainly typical crustal helium isotopic ratios, i.e., lower 3 He/ 4 He ratio ( < 0.2 times of R A , R A is the air ratio; Yang et al 2003b). However, the composition and flux of gases released from the Chung-lun mud pool showed significant variation and are considered to be controlled by tectonic structures (Yang et al 2003b) and related to the changes of local stress and strain .…”

Section: Introductionmentioning

confidence: 99%

“…This collision has propagated progressively southward, thus the northern part of the arc has already been accreted onto the continental margin resulting in the formation of an accretionary prism in southwestern Taiwan (Teng 1990;Huang et al 1997;Liu et al 1997). Numerous mud volcanoes and diapiric intrusion have been found along tectonic structures both on-shore and offshore of southwestern Taiwan (e.g., Chow et al 2000;Yang et al 2004;Chiu et al 2006). The gases vented from on-shore mud volcanoes are dominated by methane (Yang et al 2004) and exhibit mainly typical crustal helium isotopic ratios, i.e., lower 3 He/ 4 He ratio ( < 0.2 times of R A , R A is the air ratio; Yang et al 2003b).…”

Section: Introductionmentioning

confidence: 99%