HR: 0830h
AN: V51H-0389    [PDF]
TI: Source Signature of Sr Isotopes in Fluids Emitting From Mud volcanoes in Taiwan
AU: * Chung, C
EM: l4891101@ccmail.ncku.edu.tw
AF: Dept. of Earth Sciences, National Cheng Cheng Kung University, No.1, Ta-Hsueh Road., Tainan, 701 Taiwan
AU: You, C
EM: cfy20@mail.ncku.edu.tw
AF: Dept. of Earth Sciences, National Cheng Cheng Kung University, No.1, Ta-Hsueh Road., Tainan, 701 Taiwan
AU: Chao, H
EM: Ekman60@yahoo.com.tw
AF: Dept. of Earth Sciences, National Cheng Cheng Kung University, No.1, Ta-Hsueh Road., Tainan, 701 Taiwan
AB: Located at the boundary between the Philippine Sea Plate and the Asia Continental Plate, abundance of mud volcanoes were erupted on land in Taiwan. According to their occurrences and associated tectonic settings, these mud volcanoes were classified into four groupies. The group (I) mud volcanoes are located in the western coastal plane, whereas group (II) and (III) are situated near the Kutinkung anticline axis and the Chishan fault respectively. The group (IV) mud volcanoes are discovered at the Coastal Range. Although there are numerous studies focused on morphology, possible fluid migration paths and sources are poorly understood. We have collected and analyzed major ions and Sr isotopic ratios in fluids separated from various mud volcanoes in Taiwan. Chemical contents of these fluids were measured by IC and the emitted gasses were analyzed by GC. The Sr concentrations in these fluids were determined using AA and the isotopic compositions were analyzed by TIMS. The dominated ions in fluids are Na and Cl which account for 98% of dissolved materials. All fluids show similar Na/Cl ratios(0.7-0.8), slightly higher than seawater but each group has unique Sr isotopic signature. Waters expelled from group I mud volcanoes featured with low salinity and high Sr isotopic ratios ranged from 0.71150 to 0.71175. Groups II and III were outcroped in the Kutinkung formation but show distinctive chemical compositions. Group II fluids have four times Cl concentrations(358-522mM) compared with those of group III(85-162mM). The latter fluids appear to be more radiogenic(0.71012- 0.71075) indicating possible influence due to water-rock interactions. Low $^{87}$Sr/$^{86}$Sr(0.70692-0.70939) is typical characteristic of mud volcano fluids in group IV where large Mg and K depletion were discovered, suggesting effects due to sediment diagenetic processes. The chemical compositions of mud volcano associated gasses show similar distribution pattern. The major gas constituents in mud volcano zones II and III are methane($>$80%), air(1-10%) and carbon dioxide(1-5%). Gases collected from zone IV display significantly higher air content(5-20%) with low carbon dioxide($<$0.2%). These results are useful for gaining a better understanding of mud volcano fluid sources.
DE: 1010 Chemical evolution
DE: 1040 Isotopic composition/chemistry
DE: 1045 Low-temperature geochemistry
DE: 1065 Trace elements (3670)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting