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Large amounts of gas hydrate are present in marine sediments offshore Taitao Peninsula, near the Chile Triple Junction. Here, marine sediments on the forearc contain carbon that is converted to methane in a regime of very high heat flow and intense rock deformation above the downgoing oceanic spreading ridge separating the Nazca and Antarctic plate...
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... divided the area containing free gas into five sub-areas to better assess the in-situ geothermal and pressure conditions and variations of the volume expansion ratios. Table 1 shows the free gas volume at in-situ and STP conditions. The rate of free gas volume expansion was calculated to estimate the volume of free gas content at STP conditions. ...Similar publications
Large amounts of gas hydrate are present in marine sediments offshore Taitao Peninsula, near the Chile Triple Junction. Here, marine sediments on the forearc contain carbon that is converted to methane in a regime of very high heat flow and intense rock deformation above the downgoing oceanic spreading ridge separating the Nazca and Antarctic plate...
Citations
... The velocity field obtained from seismic data or laboratory analysis can be translated in terms of concentrations of gas hydrate and free gas in the pore space by using the theory that describes the elastic velocities versus gas hydrate and free gas concentration [2,3]. The theoretical model and this approach was successfully validated in the previous works by using both well, laboratory and seismic data [50,51]. Positive velocity anomalies (i.e., positive difference between seismic velocity and theoretical velocity for water saturated sediments) are considered as an indication for the presence of gas hydrates, while negative velocity anomalies (i.e., negative difference between seismic velocity and theoretical velocity for water saturated sediments) are considered as caused by free gas. ...
... Several geophysical cruises have been carried out along the Chilean margin over the past few decades with the aim of studying the complex geological structures of the area. Seismic marine data in particular has allowed for the characterization of the gas hydrates identified in many places along this margin (Bangs et al. 1993;Brown et al. 1996;Grevemeyer et al. 2006;Loreto et al. 2007;Polonia et al. 1999;Vargas-Cordero et al. 2010a, b, 2011, 2017, 2018aVillar-Muñoz et al. 2014;2019). Gas hydrate occurrence has been confirmed by the presence of cold seeps emitting methane at the seafloor (e.g., Coffin et al. 2007;Geersen et al. 2016;Jessen et al. 2011;Sellanes et al. 2004Sellanes et al. , 2008Sellanes and Krylova 2005). ...
The Chilean continental margin has been extensively investigated over the last few decades to better characterize the complex geological setting through geophysical data and seismic reflection profiles. The analysis of this seismic reflection data has assisted in identifying the location of gas hydrates and free gas in many places along the margin, mainly through the identification of a bottom simulating reflector. While this gas hydrate reservoir could serve as a strategic energy reservoir for Chile, the possible dissociation of gas hydrates due to climate change is a potential challenge. Moreover, this region is affected by large and mega-scale earthquakes that may contribute to gas hydrate dissociation and the initiation of submarine landslides. In this context, the Chilean margin is a natural laboratory for the study of hydrate system evolution under multiple geological and environmental stressors.
... The subduction of the CR leaves distinctive features in the geological records of the overriding South American plate, such as: (a) regional metamorphism and high thermal gradient [3][4][5][6][7] ; (b) a hiatus in arc magmatism 8,9 ; (c) near trench magmatism [10][11][12][13][14][15][16][17][18] ; (d) subduction erosion process 1,14,19 ; (e) hydrothermal circulation 7,20,21 ; (f) continuous tectonic uplift of the Andes 14,22 ; (g) wedge shortening 23 ; (h) slab window 2,24-26 ; (i) ophiolite obduction 10,[27][28][29][30][31] ; and (l) a distinct continuous, shallow and strong bottom-simulating reflector (BSR) 6 . The latter marks the base of the gas hydrate stability zone, and exhibits a significant decrease in gas hydrate concentration (10% of the total volume) in the vicinity of the CTJ 32 . ...
... The subduction of the CR leaves distinctive features in the geological records of the overriding South American plate, such as: (a) regional metamorphism and high thermal gradient [3][4][5][6][7] ; (b) a hiatus in arc magmatism 8,9 ; (c) near trench magmatism [10][11][12][13][14][15][16][17][18] ; (d) subduction erosion process 1,14,19 ; (e) hydrothermal circulation 7,20,21 ; (f) continuous tectonic uplift of the Andes 14,22 ; (g) wedge shortening 23 ; (h) slab window 2,24-26 ; (i) ophiolite obduction 10,[27][28][29][30][31] ; and (l) a distinct continuous, shallow and strong bottom-simulating reflector (BSR) 6 . The latter marks the base of the gas hydrate stability zone, and exhibits a significant decrease in gas hydrate concentration (10% of the total volume) in the vicinity of the CTJ 32 . ...
... In the CTJ area, the CR subducts with a low dip beneath a continental margin containing large amounts of methane trapped in hydrate form. In this peculiar subduction zone, a key role in earthquake nucleation and rupture propagation is played by fluids 51 and they are the main agent of advection heat transfer from depth to the Earth's surface, such as during vigorous fluid advection in the toe of the accretionary prism that can promote hydrate formation at shallow depths on the seabed 6,7,52 . ...
The Chile Triple Junction, where the hot active spreading centre of the Chile Rise system subducts beneath the South American plate, offers a unique opportunity to understand the influence of the anomalous thermal regime on an otherwise cold continental margin. Integrated analysis of various geophysical and geological datasets, such as bathymetry, heat flow measured directly by thermal probes and calculated from gas hydrate distribution limits, thermal conductivities, and piston cores, have improved the knowledge about the hydrogeological system. In addition, rock dredging has evidenced the volcanism associated with ridge subduction. Here, we argue that the localized high heat flow over the toe of the accretionary prism results from fluid advection promoted by pressure-driven discharge (i.e., dewatering/discharge caused by horizontal compression of accreted sediments) as reported previously. However, by computing the new heat flow values with legacy data in the study area, we raise the assumption that these anomalous heat flow values are also promoted by the eastern flank of the currently subducting Chile Rise. Part of the rift axis is located just below the toe of the wedge, where active deformation and vigorous fluid advection are most intense, enhanced by the proximity of the young volcanic chain. Our results provide valuable information to current and future studies related to hydrothermal circulation, seismicity, volcanism, gas hydrate stability, and fluid venting in this natural laboratory.
... Linked to this analysis is the common approach to convert the depth of the BSR to surface heat flow assuming that the BSR is an isotherm and marks the current base of the GHSZ [33,34]. Combining thermal modeling, BSR-depth constraints, and heat flow values from probe-measurements and/or drilling has been successfully applied at many convergent margins (e.g., Nankai [35][36][37], Makran [38], Costa-Rica [39], Cascadia [40][41][42][43][44], Chile [45]) and passive continental margins (e.g., Taiwan [46], South China Sea [47,48], East coast of India [49,50]). Required parameters for such a conversion include the geochemical conditions of pore water salinity, types of hydrocarbon occurrences, sediment thermal conductivity, and P-wave velocity for time-depth conversion. ...
Seafloor heat flow measurements are utilized to determine the geothermal regime of the Danube deep-sea fan in the western Black Sea and are presented in the larger context of regional gas hydrate occurrences. Heat flow data were collected across paleo-channels in water depths of 550–1460 m. Heat flow across levees ranges from 25 to 30 mW m−2 but is up to 65 mW m−2 on channel floors. Gravity coring reveals sediment layers typical of the western Black Sea, consisting of three late Pleistocene to Holocene units, notably red clay within the lowermost unit cored. Heat flow derived from the bottom-simulating reflector (BSR), assumed to represent the base of the gas hydrate stability zone (GHSZ), deviates from seafloor measurements. These discrepancies are linked either to fast sedimentation or slumping and associated variations in sediment physical properties. Topographic effects account of up to 50% of heat flow deviations from average values. Combined with climate-induced variations in seafloor temperature and sea-level since the last glacial maximum large uncertainties in the prediction of the base of the GHSZ remain. A regional representative heat flow value is ~30 mW m−2 for the study region but deviations from this value may be up to 100%.
... In recent decades, the Chilean margin has been extensively investigated to better characterize the complex geological setting through the acquisition of geophysical data and, in particular, seismic lines. The analysis of seismic lines allowed us to identify the occurrence of gas hydrates in many places along the Chilean margin [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Moreover, the gas hydrate presence has been confirmed by the presence of cold seeps emitting methane at the seafloor in both active and passive margins [18][19][20][21][22][23][24]. ...
In recent decades, the Chilean margin has been extensively investigated to better characterize the complex geological setting through the geophysical data. The analysis of seismic lines allowed us to identify the occurrence of gas hydrates and free gas in many places along the margin and the change of the pore fluid due to the potential hydrate dissociation. The porosity reduction due to the hydrate presence is linked to the slope to identify the area more sensitive in case of natural phenomena or induced by human activities that could determine gas hydrate dissociations and/or leakage of the free gas trapped below the gas-hydrate stability zone. Clearly, the gas hydrate reservoir could be a strategic energy reserve for Chile. The steady-state modelling pointed out that the climate change could determine gas hydrate dissociation, triggering slope failure. This hypothesis is supported by the presence of high concentrations of gas hydrate in correspondence of important seafloor slope. The dissociation of gas hydrate could change the petrophysical characteristics of the subsoil triggering slopes, which already occurred in the past. Consequently, it is required to improve knowledge about the behavior of the gas hydrate system in a function of complex natural phenomena before the exploitation of this important resource.
... In last decades, the Chilean margin has been extensively investigated to better characterize the complex geological setting through the acquisition of geophysical data and, in particular, seismic lines. The analysis of seismic lines allowed identifying the occurrence of gas hydrates in many places along the Chilean margin [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Moreover, their occurrence has also been confirmed by the presence of cold seeps emitting methane at the seafloor (e.g., [18][19][20][21][22][23]). ...
In last decades, the Chilean margin has been extensively investigated to better characterize the complex geological setting through the acquisition of geophysical data and, in particular, seismic lines. The analysis of seismic lines allowed identifying the occurrence of gas hydrates and free gas in many places along the margin. Clearly, the gas hydrate reservoir could be a strategic energy reserve for Chile, but, on the other hand, the dissociated of gas hydrate due to climate change could be an issue to face. Moreover, this region is characterized by large and mega-scale earthquakes that may contribute to gas hydrate dissociation and consequent submarine slides triggering. In this context, Chilean margin should be considered a natural laboratory to study the hydrate system evolution.
... In the last decade, the studies about gas hydrate presence along the Chilean Margin are increased rapidly, furnishing information about distribution and quantification of gas hydrate and free gas from seismic data analysis in several zones of the Chilean Margin, i.e., [42,43]. Here, Reference [44] presented an analysis of the spatial distribution, concentration, estimate of gas-phases (gas hydrate and free gas) and geothermal gradients in the accretionary prism, and forearc sediments offshore Taitao at the Chile Triple Junction. Seismic data analysis indicated high gas hydrate concentration and extremely high geothermal gradients. ...
This Special Issue reports research spanning from the analysis of indirect data, modelling, laboratory and geological data confirming the intrinsic multidisciplinarity of the gas hydrate studies. The study areas are (1) Arctic, (2) Brazil, (3) Chile and (4) the Mediterranean region. The results furnished an important tessera of the knowledge about the relationship of a gas hydrate system with other complex natural phenomena such as climate change, slope stability and earthquakes, and human activities.
This paper has investigated the mass transfer process of methane (CH 4) in aqueous solution under the effect of temperature gradient using quantitative Raman spectroscopy. At 20 MPa and 473.15 K, it was observed that CH 4 diffuses from low concentration position to high driven by temperature gradient, indicating that thermodynamic factors play a dominant role. According to the assumption that the saturated concentration of CH 4 is treated as steady concentration profile, Soret and thermal diffusion coefficients of dissolved CH 4 in the range of 1 ∼ 200 MPa and 273.15 ∼ 600 K are calculated. Based on the temperature gradient distribution calculated by thermal model in the Ashizuri section of the Nankai Trough, this paper estimates the CH 4 solubility distribution in this section and provides a new perspective to reveal a possible formation mechanism of CH 4 accumulation, leakage and related geological disasters in the geological body.
The active structures of the Iranian Makran, especially the presence of normal faults, vary laterally in the upper plate of the subduction zone, and their relationship with the deep duplexes and seamounts at depth remains unknown due to poor coverage of data onshore. In this paper, we investigate the relationship between deep structures and the topographic slope using thermo-mechanical simulations. The initial and boundary conditions of the models, including basal heat flux and convergence rate, are calibrated using the depth of the seafloor, bottom seafloor reflectors and the few available well temperature. We specifically test the influence of seamount subduction and thermally controlled changes in rock strength and décollement on the relationship between topography and deep tectonic structures. The inclusion of the brittle-ductile transition and dehydration reactions like the smectite-illite transition produce the three slope segments observed in the Makran accretionary prism. The three segments correspond to a regular accretionary prism, a flat segment that marks the smectite-illite transition, and a rise in topography located above the zone where the tegument reaches its temperature-controlled brittle-ductile transition causing underplating. Nevertheless, the models show that neither the decrease in friction associated with dehydration nor the onset of underplating is sufficient for the observed normal faults to arise in a self-consistent manner from the simulations. Crustal-scale normal faults only emerge in simulations that include subduction of a large seamount. These simulations also produce a large-thrust-slice that is the scar of former subducting seamount and serves as a buttress for the formation of a new imbricated zone. Using offshore seismic reflection data, the published onshore tomographic profiles, and our thermo-mechanical simulations, we propose two onshore-offshore cross-sections of the Iranian Makran accretionary prism.
