Dolomite early overgrowths

Early ferroan dolomite occurs in an 18m thick fine-grained unit of the Hibernia Sandstone in well B-27, where in thin zones (<1 m thick) it occluded all available pore space and replaced detrital quartz. The early diagenetic nature of this cement (crystal size 30-200 pm, average 50 pm) is indicated by a high minus-cement porosity (>30%) and the lack of quartz overgrowths or other cements. 

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