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  • 2020-2022  (1)
  • 2010-2014  (1)
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  • 1
    Publication Date: 2019-09-23
    Description: Several known gas seep sites along the Hikurangi Margin off the east coast of New Zealand were surveyed by marine controlled source electromagnetic (CSEM) experiments. A bottom-towed electric dipole–dipole system was used to reveal the occurrence of gas hydrate and methane related to the seeps. The experiments were part of the international multidisciplinary research program “New Vents” carried out on German R/V Sonne in 2007 (cruise SO191) to study key parameters controlling the release and transformation of methane from marine cold vents and shallow gas hydrate deposits. Two CSEM lines have been surveyed over known seep sites on Opouawe Bank in the Wairarapa region off the SE corner of the North Island. The data have been inverted to sub-seafloor apparent resistivity profiles and one-dimensional layered models. Clearly anomalous resistivities are coincident with the location of two gas seep sites, North Tower and South Tower on Opouawe Bank. A layer of concentrated gas hydrate within the uppermost 100 m below the seafloor is likely to cause the anomalous resistivities, but free gas and thick carbonate crusts may also play a role. Seismic data show evidence of fault related venting which may also indicate the distribution of gas hydrates and/or authigenic carbonate. Geochemical profiles indicate an increase of methane flux and the formation of gas hydrate in the shallow sediment section around the seep sites. Takahe is another seep site in the area where active venting, higher heat flow, shallow gas hydrate recovered from cores, and seismic fault planes, but only moderately elevated resistivities have been observed. The reasons could be a) the gas hydrate concentration is too low, even though methane venting is evident, b) strong temporal or spatial variation of the seep activity, and c) the thermal anomaly indicates rather temperature driven fluid expulsion that hampers the formation of gas hydrate beneath the vent.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2021-09-01
    Description: This data publication contains the compilation of global heat-flow data by the International Heat Flow Commission (IHFC; http://www.ihfc-iugg.org/) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI). The presented data release 2021 contains data generated between 1939 and 2021 and constitutes an updated and extended version of the 2012 IHFC database release (IHFC 2012; later re-published as PANGAEA release: Global Heat Flow Compilation Group, 2013). The 2021 release contains 74,548 heat-flow data from 1,403 publications. 55% of the reported heat-flow values are from the continental domain (n ~ 40,870), while the remaining 45% are located in the oceanic domain (n ~ 33,678). The data are provided in csv and Excel formats. Compared to earlier compilations, which followed the structure defined by Jessop et al. (1976), the new data release was transformed to the recently redefined structure for reporting and storing heat-flow data in the Global Heat Flow Database (Fuchs et al., 2021). Therefore, the notation and structure of the database was adopted, transforming the database field entries defined after Jessop et al. (1976) to the new field structure. Old code notations are not continued and the dataset was cleaned for entries without reporting any heat-flow value. Although successfully transformed, this release marks an intermediate step as the majority of the newly defined database fields have not been filled yet. Filling these fields, checking the existing entries and assessing the quality of each entry are the aim of the upcoming Global Heat Flow Data Assessment Project, for which this data set provides the basis. Consequently, we kindly ask the user to take notice that the current release still suffers similar problems as previously published compilations in terms of data heterogeneity, documentation and quality.
    Type: Other , NonPeerReviewed
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