The geostatistics of the metal concentrations in sediments from the eastern Brazilian continental shelf in areas of gas and oil production |
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| Institution: | 1. Ocean Sciences Institute, Labomar, Federal University of Ceará, Laboratory of Coastal Biogeochemistry, Avenida da Abolição 3207, CEP: 60 165-081, Meireles, Fortaleza, Ceará, Brazil;2. Laboratory of Cell and Tissue Biology, Darcy Ribeiro Norte Fluminense State University, Campos dos Goytacazes, Rio de Janeiro, Brazil;1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, PR China;2. College of Geosciences, China University of Petroleum, Beijing 102249, PR China;3. Shengli Oilfield Company, Sinopec, Dongying 257001, PR China;1. Department of Geoscience, Aarhus University, 8000 Aarhus C, Denmark;2. Maersk Oil Copenhagen, Denmark;3. dGB Earth Sciences, Houston, USA;1. Service d’urologie, hôpital Archet 2, 151, route Saint-Antoine-de-Ginestière, 06200 Nice, France;2. Service de radiologie, hôpital Pasteur, 30, avenue de la Voie-Romaine, 06000 Nice, France;3. Service d’anatomopathologie, hôpital Pasteur, 30, avenue de la Voie-Romaine, 06000 Nice, France;4. Hopital CIMIEZ, 4, avenue Victoria, 06003 Nice cedex 1, France;1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploration, Southwest Petroleum University, Chengdu, 610500, PR China;2. Southwest Petroleum University, Division of Key Laboratory of Carbonate Reservoirs, CNPC, Chengdu, 610500, PR China;3. China National Offshore Oil Corporation Research Institute Ltd., Beijing, 100028, PR China;4. MOE Key Laboratory of Surficial Geochemistry, School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu, 210023, PR China |
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| Abstract: | Geostatistical techniques were used to evaluate the differences in the geochemistry of metals in the marine sediments along the Eastern Brazilian continental margin along the states of Ceará and Rio Grande do Norte (Northeastern sector) and Espírito Santo (Southeastern sector). The concentrations of Al, Fe, Mn, Ba, Cd, Cu, Cr, Ni, Pb, V, Hg, and Zn were obtained from acid digestion and quantified using flame atomic absorption spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The metals showed a similar order of concentration: Al > Fe > Ba > Mn > V > Ni > Pb > Cr > Zn > Cu, in both the Ceará; and Rio Grande do Norte shelf regions but different in the Espírito Santo shelf (Fe > Al > Mn > Ba > Zn > V > Cr > Ni > Pb > Cu. The concentrations of Hg and Cd were below the detection limit in all areas. A multivariate analysis revealed that the metals of siliciclastic origin on the continental shelf of Ceará are carried by Al. In addition, a large portion of metal deposits is connected to the iron and manganese oxides on the continental margin of Rio Grande do Norte. The metals from the continental supply on the coast of Espírito Santo (Cu, Ni, Ba, and Mn) are associated with Al; whereas Cr, Pb, V, and Zn are associated with iron in this southern area. Geochemical evaluations are needed to distinguish the origin and mineralogical differences of marine sediments within the regions. Scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) applied to the sediments from the coast of Ceará showed the morphological diversity of sediment grains: biological fragments, multifaceted particles, aggregates, and crystals occurred in the three regions analyzed. Among these grains, calcite, Mg-calcite, and aragonite were predominant in the northeastern sector, whereas silicates and other minerals were predominant the southeastern sector. Mg, K, Ti, and Zr as well as the lanthanides La and Ce were identified using SEM/EDS and added to the geochemical analysis of the data. |
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| Keywords: | Geochemistry Metals Marine sediments Scanning electron microscopy |
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