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HYDROTHERMAL DOLOSTONES IN LOWER SILURIAN CARBONATES OF THE GASPÉ BELT: RELATIVE TIMING AND HYDROCARBON CHARGE. DENIS LAVOIE Natural Resources Canada and CLAUDE MORIN Hydro-Quebec Oil and Gas exploration. Gaspé Ss Gr. Dev. Upper Gaspé Ls + Fortin Grs. Sil.- Dev. Chaleurs Gr.
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HYDROTHERMAL DOLOSTONES IN LOWER SILURIAN CARBONATES OF THE GASPÉ BELT: RELATIVE TIMING AND HYDROCARBON CHARGE DENIS LAVOIE Natural Resources Canada and CLAUDE MORIN Hydro-Quebec Oil and Gas exploration
Gaspé Ss Gr. Dev. Upper Gaspé Ls + Fortin Grs. Sil.- Dev. Chaleurs Gr. Ord.-Sil. Matapédia Gr. SIMPLIFIED GEOLOGICAL MAP OF GASPÉ AND LOCATION OF STUDIED SECTIONS St-Lawrence Gulf Lac Matapedia Syncline St-Lawrence R. Isabelle Creek Humber Zone Chaleurs Bay Miramichi Terrane Bourque et al. (2000)
Upper Gaspé Lst DISTURBANCE SALINIC Stratigraphy of the Gaspé Belt Ma Pragian DEV. 400 Transgression 2 Lochkov. West Point Pridolian Regressive phase 2 Ludlovian 420 SILURIAN Transgression 1 Wenlock. Sayabec Llandov. Regressive phase 1 440 Ashgill. Source rocks Reservoirs Production
PALEOGEOGRAPHIC MODEL OF THE SAYABEC CARBONATE RAMP Synsedimentary collapse Taconian unconformity Cambrian-Ordovician
FIELD OCCURRENCE OF MASSIVE DOLOSTONES Lac Matapédia Syncline Massive dolostone breccia
Paragenesis Early dolomite replacement Fracturing – hydrothermal fluids Leaching – secondary Po Saddle dolomite HYDROCARBON MIGRATION Burial calcite Sub-aerial exposure Meteoric calcite PETROGRAPHY OF SAYABEC DOLOSTONES
Sea- water 4 STABLE ISOTOPES Matrix dolomite 2 -18 -14 -12 -6 -4 -2 -2 HTD Meteoric calcite -4 -6
FLUID INCLUSIONS 30 HTD 20 Salinity wt % NaCl Other calcite cements 10 Meteoric calcite 0 50 100 150 200 Homogenization Temperatures (Lavoie and Chi, 2001)
HTD Model and Hydrocarbon charge St-Léon SAYABEC 300 m Val-Brillant UM HTD 25 m 1 cm VUG Hydrocarbon charge Meteoric calcite cement
CONCLUSIONS • The Lower Silurian Sayavbec Formation is the oldest • shallow marine carbonates in the Gaspé Belt • Massive dolostones and breccias are currently known • at two localities in northern Gaspé • Field occurrence, petrography, stable isotope • geochemistry and fluid inclusions point to • fault-controlled pulses of Mg+2, saline and high • temperature fluids for dolomitization Hydrothermal dolomitization of the Sayabec limestone facies is currently an under-evaluated play in the Gaspé belt