Sulphide mineralisation of the continental Devonian sediments of Orkney (Scotland)

Sulphide mineralisation in the Middle Old Red Sandstone fluviatile and lacustrine sediments of Orkney is ascribed to depositional and early diagenetic events. The cations involved are considered to have been introduced in the suspended load of the rivers. Deposition of aragonite led to co-precipitation and concentration of lead. Degradation of algal material produced the organometallic complexes which enabled transport of lead, zinc, and copper. Expulsion of pore water during compaction of the sediments is regarded as the main cause of fluid migration. Deposition of sulphides occurred in the presence of sulphate-reducing bacteria when the organic complexes became unstable.Herrn Prof. Dr.-Ing. habil. Hermann Borchert zum 70. Geburtstag am 2. Februar 1975 gewidmet