Exhalation of radon and its carrier gases in SW Taiwan

The concentrations of Hg, Rn, H 2 , He and CO 2 in soil gases at 756 sites were measured in the Tangshan area where M s 7.8 earthquake occurred in 1976 and is characterized by complex tectonic structures and high seismic hazard. The results showed that, spatial variations of the gaseous anomalies, especially hydrogen and helium have spatial congruence along the tectonic lines, which can be attributed to their deep sources and the migration paths formed by the faults. A better congruence of radon and carbon dioxide is highlighted which indicates that carbon dioxide acts as the carrier gas for radon in this area. Two geochemical anomaly zones of soil gas were found in the area wherein all the studied gases exhibited anomalies or high values, related to the faults and earthquakes.

Section: Carrier Gas Of Radonmentioning

confidence: 99%

Spatial Variations of Soil Gas Geochemistry in the Tangshan Area of Northern China

Liu¹,

Du²,

Wang³

et al. 2013

“…The highest helium and methane concentrations, 848 and 115356 nL L -1 , respectively, were obtained near the bottom of site A. The degassing trace gases, like helium and radon, are usually carried by their carrier gases and emitted through fractures/faults and/or by hydrothermal activity from deep sources onto the surface of the Earth (e.g., Yang et al 2003bYang et al , 2005a. In seawater samples taken at greater depths in general contain higher concentrations of dissolved gas, which may simply be due to the higher solubility of gases at lower temperature (e.g., Takahata et al 2004;Sano and Takahata 2005).…”

Section: Methane Venting Sites With High Methane and High Helium Concmentioning

confidence: 99%

“…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%

Methane Venting in Gas Hydrate Potential Area Offshore of SW Taiwan: Evidence of Gas Analysis of Water Column Samples

Yang¹,

Chuang²,

Lin³

et al. 2006

“…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

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.