Composition of Eocene claystones of ODP Hole 105-647A

Authigenic carbonates were recovered in lower to middle Eocene claystones at Ocean Drilling Program Site 647 in the Labrador Sea. Detailed chemical, petrographic, and X-ray investigations reveal that these diagenetic carbonates have a complex mineralogical composition. At least five different carbonate phases are identified: calcium-rich rhodochrosite, rhodochrosite, manganosiderite, siderite, and calcite. Manganese carbonates are the dominant carbonate phases formed throughout the section. Textural analyses show two major generations of carbonate formation. Early cementation of micritic carbonate in burrow structures was followed by carbonate cementation forming microsparry to sparry crystals. […]

在拉布拉多海的大洋钻探计划（Ocean Drilling Program）647站位，研究人员于始新世早-中期泥岩地层中采获了自生碳酸盐（Authigenic carbonates）。通过详尽的化学、岩石学及X射线（X-ray）分析，研究表明此类成岩碳酸盐（diagenetic carbonates）具有复杂的矿物组成。本次研究共识别出至少5种不同的碳酸盐矿物相：富钙菱锰矿（calcium-rich rhodochrosite）、菱锰矿（rhodochrosite）、锰菱铁矿（manganosiderite）、菱铁矿（siderite）与方解石（calcite）。整个地层剖面中，锰碳酸盐为优势碳酸盐矿物相。结构分析显示，碳酸盐的形成存在两期主要世代：早期在生物潜穴构造内发生的泥晶碳酸盐（micritic carbonate）胶结作用，随后发育了形成微亮晶至亮晶级晶体的碳酸盐胶结作用。[...]