Geochemical characteristics of hot spring water in Bajawa area, central Flores, Indonesia

Takahashi, Masaaki; Urai, Minoru; Yasukawa, Kasumi; Muraoka, Hirofumi; Matsuda, Kōji; Akasako, Hideo; Koseki, Takehiro; Hisatani, Koichi; Kusnadi, Dedi; Sulaeman, Bangbang; Nasution, Asnawir

doi:10.9795/bullgsj.53.183

Cited by 5 publications

(1 citation statement)

References 15 publications

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“…The analytical method of mass spectrometry is similar to that used by Takahashi et al (2002). In the case of oxygen isotope measurement, a certain volume of the brine was added to a glass flask, degassed and equilibrated with CO 2 standard gas provided from a gas cylinder.…”

Section: Methodsmentioning

confidence: 99%

Chemical and isotopic compositions of brines from dissolved-in-water type natural gas fields in Chiba, Japan

2006

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Chemical and isotopic compositions of brines collected from the Minami-Kanto natural gas field in Chiba, central Japan, were measured to investigate their origin and relation to microbial methane formed from the coexisting brines. The isotopic compositions of water in the brines are -3.8 to -1.5‰ and -15 to -1‰ in δ 18 O H2O and δD H2O values, respectively, which are correlated with their chloride concentrations, suggesting that the brines are derived from seawater and that some of them have been mixed with meteoric water. The brines have high concentrations of iodine up to 0.14 g/l which are related to those of dissolved bromine and ammonia. These dissolved chemicals are suggested to have been liberated from marine sediments into pore water through the diagenetic decompositions of organic matter. The hydrogen isotopic compositions of methane (δD CH4 ) in the natural gases are -195 to -146‰. The average isotopic difference between δD CH4 and δD H2O for the samples is about 180‰, suggesting that the methane was formed by microbial activity via a CO 2 -reduction pathway. However, because the data obtained in this study were widely scattered on the δD CH4 -δD H2O plot, it is not possible to confirm that the obtained data follow the linear correlation predicted by Schoell (1980) for methane formation by CO 2 -reduction.

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Section: Methodsmentioning

confidence: 99%

Chemical and isotopic compositions of brines from dissolved-in-water type natural gas fields in Chiba, Japan

2006

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Revealing Geothermal Potential Areas with Remote Sensing Analysis for Surface Temperature and Lineament Density: Case Study in South Bajawa, NTT, Indonesia

Mardiati

Setianto

Harijoko

2020

IOP Conf. Ser.: Earth Environ. Sci.

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The research area is located in the Southern part of Bajawa, Ngada District, East Nusa Tenggara Province. This area has a geothermal potential and unique geological setting where many cinder cones are extending along NNW-SSE. A geothermal area usually indicated by surface manifestations that reach to the surface through geological structures. The initial stage to find out the existence of a geological structure that represented by surface lineament, and surface manifestations can be identified using satellite imagery to facilitate the exploration process in the field. The relationship between them is important to find out the potential geothermal area. Therefore, this study aims to analyze the relationship between geological lineament density and geothermal manifestations at the southern part of Bajawa based on the integration of ASTER imagery, DEM and Satellite Gravity anomalies. ASTER that consist of Visible-Near Infrared (VNIR), Shortwave Infrared (SWIR), Emissivity, and Surface Kinetic Temperature are used to identify surface geothermal manifestations. DEM imagery is used for lineament density analysis. While the satellite gravity anomalies are used to support the interpretation of geological structure in the study area. Field checking is conducted to ensure the results of images interpretation. The result of imagery analysis shows that geothermal manifestations are distributed at Nage and Mataloko areas indicated by surface kinetic temperature anomalies that reached 37.75°C and 37.85°C degrees, and rock alteration includes silicate clay minerals and quartz. High-density anomalies (>3km/km2) of geological lineament also located at Nage and Mataloko areas. Also, the analysis of Second Vertical Derivative (SVD) from satellite gravity anomalies shows that low gravity anomalies range from 0 to 0,5 mGal are found in Nage and Mataloko areas indicate the existence of geological structure in this area. The field check shows the same result where there is surface manifestation such as hot springs, fumarole, boiling mud pools, sulfur deposits, and altered rock are found at Mataloko and Nage area. The results of the interpretation of lineament density and the distribution of surface manifestations at the study area concluded that the relationship between the two is linear.

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Geochemistry and origin of natural gases dissolved in brines from gas fields in southwest Japan

Sakata¹,

Maekawa²,

Igari³

et al. 2012

Geofluids

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Previous geochemical studies indicated that most natural gases dissolved in brines in Japan are of microbial origin, consisting of methane produced via carbonate reduction. However, some of those from gas fields in southwest Japan contain methane relatively enriched in 13C, whose origin remains to be clarified. To address this issue, chemical and isotopic analyses were performed on natural gases and brines from the gas fields in Miyazaki and Shizuoka prefectures, southwest Japan. Methane isotopic signatures (δ13C ≈ −68‰ to −34‰ VPDB; δ2H ≈ −183‰ to −149‰ VSMOW) suggest that these gases are of microbial (formed via carbonate reduction) or of mixed microbial and thermogenic origin. The relatively high δ2H‐CH4 values and their relationship with the δ2H‐H2O values argue against the possibility of their formation via acetate fermentation. The δ13C‐CO2 values (≈−5‰), together with the slope of the correlation between δ2H‐CH4 and δ13C‐CH4 (Δδ2H‐CH4/Δδ13C‐CH4 ≈ 1), contradict the possibility of their formation via carbonate reduction followed by partial oxidation by methanotrophs. The 3He/4He ratios of the gases from Miyazaki (≈0.11–1.3 Ra) and their low correlation with δ13C‐CH4 values do not support an abiogenic origin. It is inferred therefore that the high δ13C‐CH4 values of natural gases dissolved in brines from gas fields in southwest Japan are indications of the contribution of thermogenic hydrocarbons, although whether abiogenic hydrocarbons contribute significantly to the gases from Shizuoka requires further investigation. This study has clarified that, for the future exploration of natural gases in southwest Japan, we should adopt the strategies for conventional thermogenic gas accumulations, such as checking the content, type and maturity of organic matter in the underlying sedimentary rocks.

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Geochemical characteristics of hot spring water in Bajawa area, central Flores, Indonesia

Cited by 5 publications

References 15 publications

Chemical and isotopic compositions of brines from dissolved-in-water type natural gas fields in Chiba, Japan

Chemical and isotopic compositions of brines from dissolved-in-water type natural gas fields in Chiba, Japan

Revealing Geothermal Potential Areas with Remote Sensing Analysis for Surface Temperature and Lineament Density: Case Study in South Bajawa, NTT, Indonesia

Geochemistry and origin of natural gases dissolved in brines from gas fields in southwest Japan

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