Controls on mineralisation in the Cadeby formation (lower magnesian linestone)

Harwood, Gillian Margaret (1983). Controls on mineralisation in the Cadeby formation (lower magnesian linestone). PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000de27

Abstract

Several distinct low grade assemblages of baryte and/or base metal sulphides are present within the Cadeby Formation at outcrop', each assemblage being restricted to a certain geographical area and, s betimes, one stratigraphic horizon. Although some occurrences are fault controlled, the majority have a stratigraphic control related to both carbonate facies and diagenetic history. High energy carbonate facies and bryozoan patch reefs are devoid of mineralization, whereas lower energy facies may host stratiform sulphides and baryte. Mineralization is also related to former displacive evaporites, either by direct replacement or by precipitation in voids resultant from evaporite dissolution. Diagenesis is complex with different mechanisms of dolomitization, evaporite replacement and dedolomitization; mineralization is related to early diagenesis at some localities. The spatial occurrences of mineralized localities suggests an underlying structural control linked with basement tectonics. Although isotope determinations indicate most sulphur has derived from interbedded evaporites, metals may have been introduced through basement fractures, be derived from within the formation or related to Kupferschiefer/Marl Slate mineralization. No common origin for the Permian mineral occurrences therefore exists.

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