Dolomitization Caused by Water Circulation Near the Mixing Zone: An Example from the Lower Visof the Campine Basin (Northern Belgium)
- Bruce Purser,
- Maurice Tucker and
- Donald Zenger
Published Online: 14 APR 2009
Copyright © 1994 The International Association of Sedimentologists
Dolomites: A Volume in Honour of Dolomieu
How to Cite
Muchez, P. and Viaene, W. (1994) Dolomitization Caused by Water Circulation Near the Mixing Zone: An Example from the Lower Visof the Campine Basin (Northern Belgium), in Dolomites: A Volume in Honour of Dolomieu (eds B. Purser, M. Tucker and D. Zenger), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304077.ch10
- Published Online: 14 APR 2009
- Published Print: 25 MAY 1994
Print ISBN: 9780632037872
Online ISBN: 9781444304077
- dolomitization by water circulation near mixing zone - from Lower Visean of Campine Basin (northern Belgium);
- massive lower Visean dolomites - present in subsurface of Campine Basin (northern Belgium);
- sedimentological and palaeogeographical setting;
- petrography and paragenetic sequence;
- mixing-zone dolomitization, lower carboniferous;
- thick massive dolomites occurring in Lower Visean of Campine Basin
Massive Lower Viséan dolomites are present in the subsurface of the Campine Basin (northern Belgium) and border the palaeocontinental margin of the Brabant–Wales Massif. Their occurrence is restricted to sediments below the top of the regressive trend that has been recognized within the Lower Viséan. Evaporites or their relics are absent from the Lower Viséan strata of the Campine Basin. The paragenetic sequence in the Lower Viséan is very characteristic: the formation of uniform orange-luminescent dolomites is followed by a period of calcite dissolution and the precipitation of zoned dolomite cement. After this cementation, dolomite crystals were partly dissolved and a calcite cement filled primary and secondary pores.
The palaeogeography, sedimentological setting and paragenetic sequence are interpreted to be indicative of a dolomitization related to fluid circulation near the coastal mixing zone. The uniform orange-luminescent dolomites were formed by the migration of seawater near this mixing zone. Subsequent calcite dissolution and dolomite cementation occurred in the mixing zone, which was formed in response to the lowering of relative sea level. Dolomite dissolution and calcite cementation took place in the meteoric phreatic environment in the final stage of this lowering.
Stable oxygen isotope measurements of the uniform luminescent dolomites (–6‰ to –12‰ PDB) do not support a shallow-marine origin, but represent re-equilibration of the dolomite during further burial. The calculated δ18O composition of the zoned dolomite cement (+0.8‰ PDB) is comparable with that of Viséan dolomites with a seawater origin (ca. +1‰ PDB). This strongly suggests that the mixing zone in which dolomite cementation took place was dominated by a marine fluid.