Natural gas hydrates in the Rio Grande Cone (Brazil): A new province in the western South Atlantic

作者：Miller Dennis J; Ketzer Joao Marcelo^*; Viana Adriano R; Kowsmann Renato O; Freire Antonio Fernando M; Oreiro Sergio G; Augustin Adolpho H; Lourega Rogerio V; Rodrigues Luiz F; Heemann Roberto; Preissler Adriane G; Machado Claudia X; Sbrissa Gesiane F

来源：Marine and Petroleum Geology, 2015, 67: 187-196.

DOI：10.1016/j.marpetgeo.2015.05.012

• Gas hydrate
• South Atlantic
• Pelotas Basin
• Pockmarks

The Rio Grande Cone is a large-scale fanlike feature in the continental slope of the Pelotas Basin, Southern Brazil, where ubiquitous world-class bottom simulating reflectors (BSRs) are readily observed in seismic records. With the purpose of searching for natural gas hydrate deposits in the Cone area, four oceanographic cruises were carried out between May 2011 and July 2013, leading to the discovery of two pockmark fields, active faults and gas hydrates in shallow sediments. Multichannel seismic, multibeam echo sounder, side scan sonar and sub-bottom profiler records were used to map the shallow section and select sites for piston core sampling. Gas hydrates were recovered in several piston cores within muddy sediments collected inside pockmarks displaying high backscatter in the multibeam and side scan sonar data. We present two representative piston cores where numerous levels of gas hydrates occur, along with degassing features, authigenic carbonate and soupy sediments. Gas dissociated from gas hydrate samples is dominantly methane (>99.78%) with minor quantities of ethane. The chemical and isotopic compositions of the gas strongly suggest a biogenic origin for the analyzed samples. These new findings are regarded as strong enough evidence to consider the Rio Grande Cone as a new gas hydrate province.

• 出版日期2015-11