Serpentinite mud volcanism and exhumation of fore arc- and lower plate material in the Mariana convergent margin system (IODP Expedition 366)

Serpentine seamounts located in the forearc region of a subduction zone setting represent an excellent natural laboratory for studying the geochemical processes acting along convergent plate margins and the associated natural hazards as well as the forearc structure and fault patterns. Active serpentinite mud volcanoes are currently restricted only to the Izu-Bonin-Mariana system, where old (presumably Cretaceous) oceanic lithosphere is subducting in the absence of an accretionary prism.IODP Expedition 366 recovered cores from three serpentinite mud volcanoes at increasing distances from the Mariana trench (Yinazao, Fantangis&#241;a and As&#249;t Tesoru). Most of the material consists of serpentinite mud containing lithic clasts from the underlying forearc crust and mantle as well as from the subducting Pacific plate. A thin cover of pelagic sediments and volcanic ash deposits underlying the mud volcanos were also recovered. Recycled materials from the subducted slab are found at all three mud volcanoes and consist of metavolcanics rocks, metamorphosed pelagic sediments including cherty limestone as well as fault rocks.Preliminary investigation of recovered sedimentary clasts from the summit of Fantangis&#241;a Seamount revealed that they contain primary calcite veins, whereas the latest veins are composed of aragonite (CaCO&#8323;) and barite (BaSO&#8324;).Recovered clasts from the flank consist mainly of ultramafic rocks with various degrees of serpentinization. The serpentinite veins consist of lizardite and chrysotile, which suggests rather low temperatures of serpentinization (below 200 &#176;C). Petrological analysis of metabasalt clasts from the same drilling hole shows changes in the mineral composition within the different intervals of the core. The composition of clinopyroxene varies between aegirine-augite and omphacite, but augite is also present. The presence of phengite with Si content of 3.5-3.8 a.p.f.u. indicates minimum pressure of 0.7 GPa at ~250 &#176;C.Furthermore, providing a detailed characterization of the fluids composition and transport would allow the better constraining of the tectonic and metamorphic history as well as the physical properties of the subducting Pacific Plate. Obtaining data on that point is in progress and will be presented additionally.

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Serpentinite Mud Volcanism and Exhumation of Forearc- and Lower Plate Material in the Mariana Convergent Margin System (IODP Expedition 366)

10.5194/egusphere-egu21-4865 ◽

2021 ◽

Author(s):

Irena Miladinova ◽

Walter Kurz ◽

Arianna V. Del Gaudio ◽

Werner Piller

Keyword(s):

Preliminary Investigation ◽

Accretionary Prism ◽

Oceanic Lithosphere ◽

Pacific Plate ◽

Low Grade ◽

Mud Volcanoes ◽

Metamorphic History ◽

The Matrix ◽

Si Content ◽

Recovered Material

Serpentine seamounts located in the forearc region of a subduction zone represent an excellent natural laboratory for studying the geochemical processes acting along convergent plate margins as well as the forearc structure and the related fault patterns. Active serpentinite mud volcanoes are currently restricted only to the Izu-Bonin-Mariana system, where old (presumably Cretaceous) oceanic lithosphere is subducting in the absence of an accretionary prism.IODP Expedition 366 recovered cores from three serpentinite mud volcanoes at increasing distances from the Mariana trench (Yinazao, Fantangis&#241;a and As&#249;t Tesoro). Most of the material consists of serpentinite mud containing lithic clasts from the underlying forearc crust and mantle as well as from the subducting Pacific plate. Pelagic sediments and volcanic ash deposits underlying the mud volcanoes were also recovered. Recycled materials from the subducted slab are found at all three mud volcanoes and consist of metavolcanics, metamorphosed pelagic sediments including cherty limestone as well as fault rocks.Preliminary investigation of lithic clasts from the furthest As&#249;t Tesoro Seamount revealed metavolcanics as well as serpentinized ultramafics with well-preserved primary mineral assemblages containing olivine, orthopyroxene and spinel.Recovered clasts from the summit of the adjacent Fantangis&#241;a Seamount contain mainly sedimentary rocks of probable Pacific plate provenance. These consist of red cherty limestone breccia, red shale and mud-siltstone transected by a network of carbonate veins. In contrast, recovered material from the flank shows a wider variety including ultramafic rocks with various degrees of serpentinization and matrix composed of mesh and bastite textures, mafic metavolcanics as well as low-grade metasediments (cherty limestones). Interestingly, garnet with andradite composition occurs throughout the matrix of the ultramafics, indicating serpentinization temperatures of at least 225 &#176;C.Petrological analysis of metabasalt clasts from the flank of Fantangis&#241;a shows changes in the mineral composition within the different core intervals. The composition of clinopyroxene varies between aegirine-augite and omphacite, but augite and diopside are also present. The presence of phengite with Si content of up to 3.5 a.p.f.u. as well as the Na-content in pyroxene indicate minimum pressure of 0.7 GPa at ~250 &#176;C. Additionaly, this estimation is supported by the presence of prehnite, chlorite and pumpellyite.&#160;Furthermore, providing a detailed characterization of the fluids composition and transport would allow the better constraining of the tectonic and metamorphic history as well as the physical properties of the subducting Pacific Plate. Additional data on that will be presented.

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Characterization of Archaeal and Bacterial Communities Thriving in Methane-seeping on-land Mud Volcanoes, Niigata, Japan.

10.21203/rs.3.rs-1084998/v1 ◽

2021 ◽

Author(s):

Nori Miyake ◽

Ryo Ishimaru ◽

Goro Komatsu ◽

Takafumi Matsui

Keyword(s):

Sequencing Analysis ◽

Mud Volcanoes ◽

Sulfate Reducing ◽

Marine Strata ◽

Mud Volcanism ◽

Rrna Sequencing ◽

Anaerobic Methanotrophs ◽

Reducing Bacteria ◽

First Time

Abstract Submarine mud volcanoes (MVs) have attracted significant interest in the scientific community for obtaining clues on the subsurface biosphere. On-land MVs, which are much less focused in this context, are equally important and they may provide insights also for astrobiology of extraterrestrial mud volcanism. Hereby, we characterized microbial communities of the two active methane-seeping on-land MVs, Murono and Kamou, in central Japan. Metataxonomic 16S rRNA sequencing analysis of those sites recovered the dominant archaeal taxa affiliated with methanogens. Anaerobic methanotrophs (ANME), with the subgroups ANME-1b and ANME-3, were also recovered from the Murono site albeit a greatly reduced abundance compared to typical submarine MVs. ANME-3 was in fact identified for the first time for land-based MVs. The bacterial sequences affiliated to Atribacteria, sulfate-reducing bacteria (SRB), and Fe(III)-reducing bacteria were recovered. SRB and ANME form a syntrophic consortium, which is often found at the sulfate-methane transition zone of submarine MVs where diffused sulfate (SO42-) is constantly enriched from the ocean. Previous investigations speculate that the erupted materials from Murono are originated from the Miocene marine strata, and we hypothesize that the old sea-related juvenile water is the source of additional sulfur-related components for the SRB-ANME consortium at Murono.

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Preliminary investigation of the formation age and chemical characterization of the tropical peat in the middle Sepik Plain, northern Papua New Guinea

Geoscience Letters ◽

10.1186/s40562-015-0021-4 ◽

2015 ◽

Vol 2 (1) ◽

pp. 1 ◽

Cited By ~ 4

Author(s):

Eisuke Ono ◽

Mitsutoshi Umemura ◽

Takuya Ishida ◽

Chisato Takenaka

Keyword(s):

Papua New Guinea ◽

Preliminary Investigation ◽

Chemical Characterization ◽

New Guinea ◽

Tropical Peat

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LA-ICP-MS U-Pb dating and geochemical characterization of oil inclusion-bearing calcite cements: Constraints on primary oil migration in lacustrine mudstone source rocks

Geological Society of America Bulletin ◽

10.1130/b35804.1 ◽

2021 ◽

Author(s):

Ao Su ◽

Honghan Chen ◽

Yue-xing Feng ◽

Jian-xin Zhao

Keyword(s):

Fluid Inclusion ◽

Inductively Coupled Plasma ◽

Homogenization Temperature ◽

Source Rocks ◽

Oil Migration ◽

Carbon And Oxygen Isotope ◽

Fluorescence Characteristics ◽

Calcite Veins ◽

Migration Event

To date, few isotope age constraints on primary oil migration have been reported. Here we present U-Pb dating and characterization of two fracture-filling, oil inclusion-bearing calcite veins hosted in the Paleocene siliciclastic mudstone source rocks in Subei Basin, China. Deposition age of the mudstone formation was estimated to be ca. 60.2−58.0 Ma. The first vein consists of two major phases: a microcrystalline-granular (MG) calcite phase, and a blocky calcite phase, each showing distinctive petrographic features, rare earth element patterns, and carbon and oxygen isotope compositions. The early MG phase resulted from local mobilization of host carbonates, likely associated with disequilibrium compaction over-pressuring or tectonic extension, whereas the late-filling blocky calcite phase was derived from overpressured oil-bearing fluids with enhanced fluid-rock interactions. Vein texture and fluorescence characteristics reveal at least two oil expulsion events, the former represented by multiple bitumen veinlets postdating the MG calcite generation, and the latter marked by blue-fluorescing primary oil inclusions synchronous with the blocky calcite cementation. The MG calcite yields a laser ablation−inductively coupled plasma−mass spectrometry U-Pb age of 55.6 ± 1.4 Ma, constraining the earliest timing of the early oil migration event. The blocky calcite gives a younger U-Pb age of 47.8 ± 2.3 Ma, analytically indistinguishable from the U-Pb age of 46.5 ± 1.7 Ma yielded by the second calcite vein. These two ages define the time of the late oil migration event, agreeing well with the age estimate of 49.7−45.2 Ma inferred from fluid-inclusion homogenization temperature and published burial models. Thermodynamic modeling shows that the oil inclusions were trapped at ∼27.0−40.9 MPa, exceeding corresponding hydrostatic pressures (23.1−26.7 MPa), confirming mild-moderate overpressure created by oil generation-expulsion. This integrated study combining carbonate U-Pb dating and fluid-inclusion characterization provides a new approach for reconstructing pressure-temperature-composition-time points in petroleum systems.

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Data report: a brittle (normal?) shear zone from Hole C0002P: deformation structures and their relationship with calcite veins (IODP Expedition 348, Nankai Trough accretionary prism)

10.2204/iodp.proc.348.205.2017 ◽

2017 ◽

Cited By ~ 1

Author(s):

A. Crespo-Blanc

Keyword(s):

Shear Zone ◽

Nankai Trough ◽

Accretionary Prism ◽

Deformation Structures ◽

Calcite Veins

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Roles of Hydrothermal Circulations on Heat Flow in the Fore-arc, Northeast Japan Subduction Zone, A Numerical Modeling Study.

10.5194/egusphere-egu21-1958 ◽

2021 ◽

Author(s):

Dongwoo Han ◽

Changyeol Lee

Keyword(s):

Heat Transfer ◽

Heat Flow ◽

Oceanic Crust ◽

Numerical Models ◽

Accretionary Prism ◽

High Heat ◽

Pacific Plate ◽

Model Calculations ◽

The Pacific ◽

Japan Subduction Zone

Heat flow in the fore-arc, Northeast Japan shows characteristic highs and lows in the seaward and landward regions of the trench axis, respectively, compared to 50 mW/m2 that is constrained from the corresponding half-space cooling model (135 Ma). For example, the high average of 70 mW/m2 at the 150-km seaward region from the trench was observed while the low average of 30 mW/m2 at the 50-km landward region was. To explain the differences between the constraints and observations of the heat flow, previous studies suggested that the high heat flow in the seaward region results from the reactivated hydrothermal circulations in the oceanic crust of the Pacific plate along the developed fractures by the flexural bending prior to subduction. The low heat flow is thought to result from thermal blanket effect of the accretionary prism that overlies the cooled subducting slab by the hydrothermal circulations. To understand heat transfer in the landward region of the trench, a series of two-dimensional numerical models are constructed by considering hydrothermal circulations in the kinematically thickening accretionary prism that overlies the converging oceanic crust of the Pacific plate where hydrothermal circulations developed prior to subduction. The model calculations demonstrate no meaningful hydrothermal circulations when the reasonable bulk permeability of the accretionary prism(<10-14m2) is used; the thermal blanket effect significantly hinders the heat transfer, yielding only the heat flow of 10 mW/m2 in the landward region, much lower than the average of 30 mW/m2. This indicates that other mechanisms such as the expelled pore fluid by compaction of the accretionary prism play important roles in the heat transfer across the accretionary prism.

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