Large Gas Reservoir Along the Rift Axis of a Continental Back‐Arc Basin Revealed by Automated Seismic Velocity Analysis in the Okinawa Trough

Mukumoto, Kota; Tsuji, Takeshi; Hendriyana, Andri

doi:10.1029/2019gl083065

Cited by 9 publications

(4 citation statements)

References 33 publications

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“…These ndings indicate that the sediment layer in the subunit of the Neogene period is uid saturated. Similar evidence supporting our observations has been found in the Iheya North Knoll (Mukumoto et al;2019), showing high amplitude re ection and low P-wave velocities (< 1,500 m/s) in the underlying layer. These characteristics are potentially caused by the presence of a gas reservoir.…”

Section: Discussionsupporting

confidence: 92%

Investigating Narcondam offshore using high-resolution seismic reflection data

Srivastav,

Ghosal

2023

Geo-Mar Lett

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The Andaman Sea is a back-arc basin that hosts the active Barren and the dormant Narcondam volcanoes. Despite its geological and geophysical signi cance, there are limited studies conducted over offshore Andaman. Here, a geophysical study of Narcondam offshore is presented to investigate basinal deposits and associated uids and their migration paths using a 30 km long high-resolution 2D seismic re ection. The migrated section reveals a subsurface image highlighting evidence of a bright sea oorparallel re ector with negative polarity at a two-way time (TWT) of 2.78-2.82 s (~2.2-2.3 km) with an interval velocity of 1.56 km/s. Amplitude Versus Angle (AVA) analysis using Aki Richard's two-term equation is further conducted to characterize the reserved uid. The AVA analysis yields an increase in amplitude with angle, providing compelling evidence of uid presence. Additionally, the depth converted migrated seismic section exhibits indications of columnar faults of Neogene period in uencing the migration of uids within the basin.

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Section: Discussionsupporting

confidence: 92%

Investigating Narcondam offshore using high-resolution seismic reflection data

Srivastav,

Ghosal

2023

Geo-Mar Lett

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“…Schematic diagram showing the Yonaguni Knoll IV hydrothermal systems modified from Mukumoto, Tsuji, and Hendriyana (), Humphris and Klein () and Alt (). Seawater percolates down into the crust in widespread recharge zone, reacting with the rock and undergoing continuous chemical modification as it is heated by a shallow volcanic intrusion in the root zone (Alt, ; Mukumoto et al, ). These hot fluids become buoyant and rise rapidly in discharge zone back to the seafloor, where Zn–Pb sulfides are deposited [Colour figure can be viewed at wileyonlinelibrary.com]…”

Section: Discussionmentioning

confidence: 99%

Amphibole perspective to unravel the rhyolite as a potential fertile source for the Yonaguni Knoll IV hydrothermal system in the southwestern Okinawa Trough

Chen

Zeng

et al. 2019

Geological Journal

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Yonaguni Knoll IV is an active seafloor hydrothermal system containing massive Zn-Pb sulfides located in the southwestern OkinawaTrough. Previous research has suggested that the metal elements Zn and Pb were dominantly derived from the local volcanic rocks via water-rock interactions. However, it is not known whether or why the volcanic rocks are rich in these metals. Here, we performed a detailed in situ analysis of the major and trace elements in amphiboles in the rhyolite from the hydrothermal field to decipher the physical-chemical conditions of the silicic magma, including temperature (T), pressure (P), oxygen fugacity (fO 2 ), volatile contents (Cl, H 2 O) and metal contents (Pb, Zn), and investigate the behavior of the metals (Zn and Pb) during melt evolution. Our results show that the amphiboles are euhedral calcic magnesiohornblende and are in equilibrium with the hydrous and oxidized host rhyolitic melt characterized by high H 2 O melt (~5.8-6.5 wt.%), fO 2 (NNO +0.1 to +0.6) and SiO 2 melt (~71.73-72.62 wt.%) values at 761-797°C and 102-137 MPa, corresponding to an approximate depth of 3.9-5.2 km. In addition, the rare earth element (REE) patterns of the melt reconstructed from the amphiboles are analogous to those of cold-wetoxidized rhyolites. Thus, the amphiboles crystallized in a cold-wet-oxidized shallow silicic magma chamber. The high oxygen fugacity is inferred to have favored sulfur and metal enrichment in the melt. The most abundant metal in the amphiboles is Zn (237-294 ppm), and the concentrations of Pb are much lower (0.86-3.32 ppm), suggesting that Zn preferentially entered the amphibole and that Pb was retained in the melt. The Cl content of the amphiboles ranges from 0.11 to 0.25 wt.%, and accordingly, the Cl melt content estimated from the amphiboles varies from 0.15 to 0.28 wt. %. The low (Cl/H 2 O) melt ratios, which are <0.05 (i.e.,~0.02-0.04), suggest that the melt exsolved an H 2 O-rich vapor rather than a hydrosaline fluid with insufficient Cl to transport metals (e.g., Pb and Zn) into the vapor phase during degassing both in the magma chamber and during ascent. The lack of exsolved hydrosaline fluid and the high oxidation conditions resulted in the metal elements Pb and Zn remaining dissolved in the rhyolitic melt and/or partitioning into crystalline minerals upon eruption. Thus, the large volumes of rhyolitic magma that intruded into the upper crust of the Yonaguni Knoll IV hydrothermal field are a potential fertile source of these elements via leaching by heated seawater.

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“…Similar behavior of multi-component mixtures, including phase transitions, has been documented in natural environments. [24][25][26] Thus, investigating natural analogues could provide useful information for modeling the behavior of low-purity CO 2 in geological repositories. We should further consider chemical reactions in the stored reservoir.…”

Section: Future Effortsmentioning

confidence: 99%

Geological storage of CO₂–N₂–O₂ mixtures produced by membrane‐based direct air capture (DAC)

et al. 2021

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Carbon capture and storage has been considered as a realistic approach to reducing atmospheric CO 2 concentrations. However, the cost of capturing high-purity CO 2 typically used for geological storage (e.g., 98%) is high. Direct air capture (DAC), a technology that extracts CO 2 of relatively low-purity from the ambient atmosphere, has been recently proposed as a means to achieve negative CO 2 emissions when the product is sequestered underground. Although the CO 2 produced by DAC is of low-purity, the other gaseous components (mainly nitrogen and oxygen) are not hazardous materials like NO x and SO x that must be typically dealt with by conventional projects in coal-burning plants. Here, we evaluate geological storage of the low-purity CO 2 captured via advanced membrane-based DAC technology. The ubiquity of ambient air is important in reducing transport costs and ensuring social acceptance as the CO 2 product can be both produced and stored at sites in remote areas, such as deserts and offshore platforms. We calculated the density of CO 2 -N 2 -O 2 mixtures via molecular dynamics simulation and evaluated the cost of the low-purity CO 2 storage. Our evaluation suggests that the storage of low-purity CO 2 in geological formations is environmentally acceptable and economically viable.

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Large Gas Reservoir Along the Rift Axis of a Continental Back‐Arc Basin Revealed by Automated Seismic Velocity Analysis in the Okinawa Trough

Cited by 9 publications

References 33 publications

Investigating Narcondam offshore using high-resolution seismic reflection data

Investigating Narcondam offshore using high-resolution seismic reflection data

Amphibole perspective to unravel the rhyolite as a potential fertile source for the Yonaguni Knoll IV hydrothermal system in the southwestern Okinawa Trough

Geological storage of CO₂–N₂–O₂ mixtures produced by membrane‐based direct air capture (DAC)

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Large Gas Reservoir Along the Rift Axis of a Continental Back‐Arc Basin Revealed by Automated Seismic Velocity Analysis in the Okinawa Trough

Cited by 9 publications

References 33 publications

Investigating Narcondam offshore using high-resolution seismic reflection data

Investigating Narcondam offshore using high-resolution seismic reflection data

Amphibole perspective to unravel the rhyolite as a potential fertile source for the Yonaguni Knoll IV hydrothermal system in the southwestern Okinawa Trough

Geological storage of CO2–N2–O2 mixtures produced by membrane‐based direct air capture (DAC)

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Geological storage of CO₂–N₂–O₂ mixtures produced by membrane‐based direct air capture (DAC)