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
St-Lawrence R. St-Lawrence Gulf Chaleurs Bay Miramichi Terrane Humber Zone Chaleurs Gr. Gaspé Ss Gr. Upper Gaspé Ls + Fortin Grs. Sil.- Dev. Dev. Matapédia Gr.Ord.-Sil. Bourque et al. (2000) SIMPLIFIED GEOLOGICAL MAP OF GASPÉ AND LOCATION OF STUDIED SECTIONS Isabelle Creek Lac Matapedia Syncline
Pridolian Ludlovian Wenlock. Llandov. Lochkov. Pragian Ashgill. SILURIAN DEV Ma SALINIC DISTURBANCE Regressive phase 1 Regressive phase 1 Regressive phase 2 Regressive phase 2 Transgression 2 Transgression 1 Upper Gaspé Lst West Point Sayabec Source rocks Reservoirs Stratigraphy of the Gaspé Belt Production
Cambrian-Ordovician Taconianunconformity PALEOGEOGRAPHIC MODEL OF THE SAYABEC CARBONATE RAMP Synsedimentary collapse
FIELD OCCURRENCE OF MASSIVE DOLOSTONES Lac Matapédia Syncline Massive dolostone breccia
PETROGRAPHY OF SAYABEC DOLOSTONES Paragenesis Early dolomite replacement Fracturing – hydrothermal fluids Leaching – secondary Po Saddle dolomite HYDROCARBON MIGRATION Burial calcite Sub-aerial exposure Meteoric calcite
HTD Meteoric calcite Matrix dolomite Sea- water STABLE ISOTOPES
FLUID INCLUSIONS Homogenization Temperatures Salinity wt % NaCl (Lavoie and Chi, 2001) Meteoric calcite HTD Other calcite cements
HTD Model and Hydrocarbon charge 300 m 25 m 1 cm St-Léon SAYABEC Val-Brillant UM HTD Hydrocarbon chargeMeteoric calcite cement VUG
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