| Titre | A long-term geothermal observatory across subseafloor gas hydrates, IODP hole U1364A, cascadia accretionary prism |
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| Auteur | Becker, K; Davis, E E ; Heesemann, M; Collins, J A; McGuire, J J |
| Source | Frontiers in Earth Science vol. 8, 568566, 2020 p. 1-10, https://doi.org/10.3389/feart.2020.568566  Accès ouvert |
| Image |  |
| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200638 |
| Éditeur | Frontiers Media S.A. |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.3389/feart.2020.568566 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Colombie-Britannique |
| Lat/Long OENS | -126.9389 -126.8167 48.7333 48.6500 |
| Sujets | gradient géothermique; hydrates de gaz; Sciences et technologie |
| Illustrations | cartes de localisation; diagrammes; images sismiques; graphiques |
| Diffusé | 2020 12 21 |
| Résumé | (disponible en anglais seulement)
We report 4 years of temperature profiles collected from May 2014 to May 2018 in Integrated Ocean Drilling Program Hole U1364A in the frontal accretionary prism
of the Cascadia subduction zone. The temperature data extend to depths of nearly 300 m below seafloor (mbsf), spanning the gas hydrate stability zone at the location and a clear bottom-simulating reflector (BSR) at ~230 mbsf. When the hole was
drilled in 2010, a pressure-monitoring Advanced CORK (ACORK) observatory was installed, sealed at the bottom by a bridge plug and cement below 302 mbsf. In May 2014, a temperature profile was collected by lowering a probe down the hole from the ROV
ROPOS. From July 2016 through May 2018, temperature data were collected during a nearly two-year deployment of a 24-thermistor cable installed to 268 m below seafloor (mbsf). The cable and a seismic-tilt instrument package also deployed in 2016 were
connected to the Ocean Networks Canada (ONC) NEPTUNE cabled observatory in June of 2017, after which the thermistor temperatures were logged by Ocean Networks Canada at one-minute intervals until failure of the main ethernet switch in the integrated
seafloor control unit in May 2018. The thermistor array had been designed with concentrated vertical spacing around the bottom-simulating reflector and two pressure-monitoring screens at 203 and 244 mbsf, with wider thermistor spacing elsewhere to
document the geothermal state up to seafloor. The 4 years of data show a generally linear temperature gradient of 0.055°C/m consistent with a heat flux of 61–64 mW/m2. The data show no indications of thermal transients. A slight departure from a
linear gradient provides an approximate limit of ~10-10 m/s for any possible slow upward advection of pore fluids. In-situ temperatures are ~15.8°C at the BSR position, consistent with methane hydrate stability at that depth and pressure. |
| GEOSCAN ID | 327909 |
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