--> Development of Dissolution Vugs in the Middle Devonian Carbonate Reservoirs in the Presqu'ile Barrier: Meteoric or Hydrothermal?, by H. Qing; #90986 (1994).

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Abstract: Development of Dissolution Vugs in the Middle Devonian Carbonate Reservoirs in the Presqu'ile Barrier: Meteoric or Hydrothermal?

Hairuo Qing

Dissolution vugs and breccias in the Presqu'ile barrier were previously interpreted to be related to meteoric water during Middle Devonian sub-Watt Mountain exposure. Studies of open pits at Pine Point and core samples from the subsurface revealed that these dissolution vugs were caused by two different processes, meteoric and hydrothermal. The meteoric dissolution during the Watt Mountain emergence was minor, and the resulting vugs and breccias are: (1) commonly infilled with green shale, and locally with pendant calcite cements; (2) restricted to the strata immediately beneath the unconformity; and (3) formed prior to stylolitization, dolomitization, and mineralization.

The diagnostic meteoric karst features, such as rundkarren, dolina, calcrete, terra rossa, and speleothems are not observed. The limited influence of meteoric water during sub-Watt Mountain exposure is possibly due to a arid climate and relatively short periods of exposure.

In contrast, hydrothermal dissolution vugs and breccias: (1) are filled with laminated dolomites, saddle dolomites, sulphide minerals, late-stage calcite and pyrobitumen that are associated with hydrothermal fluids; (2) occur only in the dolomites that are interpreted to be associated with hydrothermal fluids; and (3) occur both above and below the Watt Mountain unconformity; and (4) postdate stylolites. Thus majority of dissolution vugs and breccias were formed much later, during burial by hydrothermal fluids that invaded the Presqu'ile barrier.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994