Bedrock Mapping in the Jolly Lake Area: A New Look at the >3.0 Ga Basement Granites and Their Relationships to the Central Slave Cover Group and the Northern-Most Beaulieu River Volcanic BeltWednesday, November 21, 2018 - 11:00 to 11:19 Theatre 1
In 2018 the Northwest Territories Geological Survey conducted the first year of a multi-year bedrock mapping initiative in the Jolly, Mohawk, and “Dragon” lakes area. The study area is approximately 230 km north-northeast of Yellowknife and west of Courageous Lake. Previously mapped at 1:250 000 scale, this area has been revisited as it sits adjacent to the proposed all-season Slave Geological Province access corridor. Mapping within the northern-most Beaulieu River Volcanic Belt was conducted at 1:10 000: the surrounding granitoid complex warranting mapping at 1:50 000 scale.
The objectives of the project were to: 1) increase the detail of mapping of an area of granites comprising Central Slave Basement Complex rocks and post-tectonic granitic plutons to establish their relative age, 2) to study the relationships of the pre-, syn-, and, post-volcanic belt aged plutonic bodies with the 2.9-2.8 Ga Central Slave Cover Group and the ca. 2.7 Ga volcanic rocks of the Beaulieu River Volcanic Belt, 3) elucidate the nature and timing of thermotectonic events both prior to and subsequent to volcanic belt deposition, 4) provide a more detailed understanding of the architecture of the Slave craton with which to place regional Au and VMS mineralizing events, 5) and to gain a better understanding of the geological history and crustal architecture of this area in advance of the proposed All-Season Slave Geological Province access corridor.
Local geology in the Jolly Lake area is dominated by granitoid rocks of various ages, both as part of the Central Slave Basement Complex and of younger supracrustal origin. The oldest rocks are a mix of polydeformed granitic to tonalitic plutons that are gneissic and/or migmatitic. In the southwest part of the map area basement granites are overlain by the ca. 2.9 Ga Central Slave Cover Group and ca. 2.7 Ga volcanic rocks of the northern-most Beaulieu River Volcanic Belt. These volcanic rocks are dominated by massive and pillowed basaltic flows with minor amounts of rhyolite, basaltic pillow breccia, and mafic and felsic volcanoclastic deposits. In addition, the area has been intruded by post-volcanic belt granites and mafic Lac de Gras (?) dykes. The nature and timing of thermotectonic events both prior and subsequent to volcanic belt deposition was studied. A protracted history of regional folding and shearing along the N-S Beniah Fault Zone is preserved in the various aged rock in the study area.