Mineral diagenesis in a carbonate-rich mudstone: The Lower Carboniferous Hodder Shale, UK

Timothy M. Ohiara, Kevin G. Taylor, Patrick J. Dowey

Research output: Contribution to journalArticlepeer-review


Mineral authigenesis in mudstones respond differently across the compositional spectrum of fine-grained rocks resulting in a complex array of possible rock fabrics that affect the mechanical capacity of mudstones. Within carbonate-rich mudstones, geochemical controls on silicate and carbonate mineral reactions are variable and poorly understood. Here we analyse the diagenetic minerals of the carbonate-rich Hodder Mudstone from the Carboniferous Bowland Basin, UK, using SEM petrography combined with X-ray-based inorganic geochemical data. Our findings show that up to 90% of quartz cement in the samples are diagenetic in origin, originating mainly from biogenic silica dissolution, and clay mineral reactions. It is also evident that due to the varying diagenetic silica-yielding reactions, authigenic silica overgrowths and isolated authigenic quartz crystals are localised in argillaceous samples while calcareous samples are characterized by silica replacement textures and quartz/calcite intergrowths. Moreover, euhedral dolomite crystals are concentrated within argillaceous units in comparison with calcareous units which are characterised by anhedral dolomite precipitation and replacement textures. These finding presents a case for facies28 selective cementation as both early and burial diagenetic alterations were observed to be controlled by primary depositional components of biogenic debris and extrabasinal silicate detritus that resulted in complex and variable precipitation of authigenic minerals.
Original languageEnglish
JournalGeological Society Special Publication
Publication statusAccepted/In press - 20 Jan 2022


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