Mineralogical and geochemical characterization of hydrocarbon seep sediments from the Gulf of Mexico

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• 作者：Carles Canet ; Rosa Marí ; a Prol-Ledesma ; Elva Escobar-Briones ; Carlos Mortera-Gutié ; rrez ; Rufino Lozano-Santa Cruz ; Carlos Linares ; Edith Cienfuegos and Pedro Morales-Puente
• 关键词：Cold seeps ; Carbonates ; Barite ; Stable isotopes
• 刊名：Marine and Petroleum Geology
• 出版年：2006
• 出版时间：June 2006
• 年：2006
• 卷：23
• 期：5
• 页码：605-619
• 全文大小：1243 K

文摘

A common characteristic of the Gulf of Mexico (GOM) seafloor, hydrocarbon seepage produces asphalt volcanism, brine pools, gas hydrates and authigenic carbonates. We studied authigenic carbonates from two areas: Green Canyon (Louisiana slope, 1000 mbsl) and the Chapopote diapir (abyssal plain, southwestern GOM, 2900 mbsl). Carbonates consist of oily, matrix-supported limestones with variable porosity and a fine-grained matrix of calcite. They occur in Green Canyon as both concretions formed below the seafloor and as slabs of seabed pavements. In each case, the carbonates are mudstones with a mud matrix consisting of high-Mg calcite, disseminated pyrite and detrital quartz. The carbonate slabs have vug microporosity and contain barite that occurs as vug lining. The precipitation of barite results from a reaction between barium-rich and sulfate-free seep fluids and downwards-diffusing seawater. The carbonates in Chapopote occur in relation to tar flows and form crusts of wackestones with bivalve shells. The matrix is composed by low-Mg calcite with disseminated pyrite and detrital quartz. The carbonate mud shows depletion in ¹³C, with δ¹³C between −36.9‰ and −23.0‰. Carbonates precipitate as a consequence of anaerobic methane oxidation coupled with seawater sulfate reduction. δ¹⁸O values (3.4–4.4‰) suggest precipitation at temperatures between 5 and 9 °C.