Burial and Hydrothermal Diagenesis of Ordovician Carbonates from the Michigan Basin, Ontario, Canada

  1. Bruce Purser,
  2. Maurice Tucker and
  3. Donald Zenger
  1. M. Coniglio1,
  2. R. Sherlock1,
  3. A. E. Williams-Jones2,
  4. K. Middleton1 and
  5. S. K. Frape1

Published Online: 14 APR 2009

DOI: 10.1002/9781444304077.ch14

Dolomites: A Volume in Honour of Dolomieu

Dolomites: A Volume in Honour of Dolomieu

How to Cite

Coniglio, M., Sherlock, R., Williams-Jones, A. E., Middleton, K. and Frape, S. K. (1994) Burial and Hydrothermal Diagenesis of Ordovician Carbonates from the Michigan Basin, Ontario, Canada, 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.ch14

Author Information

  1. 1

    Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada

  2. 2

    Department of Earth and Planetary Sciences, McGill University, Montreal, Quebec, H3A 9Z9, Canada

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 25 MAY 1994

ISBN Information

Print ISBN: 9780632037872

Online ISBN: 9781444304077

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Keywords:

  • burial and hydrothermal diagenesis of Ordovician carbonates from Michigan Basin, Ontario, Canada;
  • hydrocarbon reservoirs hosted by Middle Ordovician carbonates - exploration targets in Michigan Basin;
  • Palaeozoic reservoirs in southwestern Ontario - within Chatham Sag;
  • replacive dolomite;
  • predolomitization diagenetic history;
  • dolomites of Manitoulin Island area - fossils and sedimentary structures visible on weathered outcrop surfaces;
  • postdolomitization diagenetic history;
  • pressure dissolution and fracturing;
  • fluid inclusions investigated in cleavage fragments of calcite;
  • mechanism for fracture-related dolomitization

Summary

Ordovician carbonates in the subsurface of southwestern Ontario and exposed in the Manitoulin Island area are located on the margins of the Michigan Basin. In the subsurface, a widespread ferroan ‘cap dolomite’ at the top of the Trenton sequence most likely formed from fluids generated from compaction of the overlying shales of the Blue Mountain Formation (Utica Shale equivalent). Other dolomite in the sequence, both in the subsurface and in outcrop, is interpreted to be controlled by tectonic fractures which were intermittently active throughout the Palaeozoic. Saddle dolomite cement occurs in secondary and primary intraparticle pores. Pervasive replacive dolomite and selectively dolomitized beds, fossils and burrows also occur. In the subsurface, fracture-related dolomite is responsible for generating hydrocarbon reservoirs in otherwise impermeable and non-porous limestones.

Based on field, petrographic and oxygen isotopic data, the lithification of these Ordovician carbonates was protracted and can be largely explained as having occurred during burial, probably to depths of 1500–2000 m. Fluid inclusions, however, indicate that these carbonates experienced temperatures that were considerably higher than those attributable to burial alone. In general, fluid inclusions in early calcite cement (predolomitization), dolomite and late calcite cement (postdolomitization) homogenize at temperatures ranging from approximately 100 to 200°C. Dolomitizing fluids were generated through compaction flow from the more central parts of the basin, reflux from the overlying Silurian strata or invasion of younger fluids. Dolomitizing fluids travelled along fractures in the Ordovician sequence, pervasively altering permeable limestones in the immediate vicinity of fractures. Further away from the fractures, or along less permeable limestones, individual beds, fossils and burrows were selectively dolomitized. The fluid-inclusion temperatures can be explained in the context of a burial diagenetic system in which hydrothermal effects were important, although the heat source is uncertain.