|Cover, Abstract and Table of Contents (PDF document, 1328 Kb)
Chapter One: Introduction (PDF document, 2597 Kb)
Chapter Two: Lithologic Units
Part A (PDF document, 9188 Kb)
Part B (PDF document, 7485 Kb)
Part C (PDF document, 9662 Kb)
Chapter Three: Structure (PDF document, 6108 Kb)
Chapter Four: Metamorphism (PDF document, 3733 Kb)
Chapter Five: Economic Geology (PDF document, 6865 Kb)
References and Appendix (PDF document, 381 Kb)
Bulletin 107 notes that the Kechika Trough represents a Lower Paleozoic basin developed between the MacDonald Platform to the east and the Cassiar Platform to the west. This basin was well established by Late Cambrian time and ceased to be a depositional entity at the beginning of the Late Devonian. Mapping along the western part of the trough, between the Gataga River and the 60th parallel, encountered layered rocks of Proterozoic to Cenozoic age. These include: Late Proterozoic siliciclastics, carbonates and volcanics; siliciclastics and carbonates of Cambrian age; Late Cambrian to Early Ordovician calcareous argillites and argillites of the Kechika Group; slate, siltstone and minor limestone of the Middle Ordovician to Middle Devonian Road River Group; Late Devonian to Early Mississippian argillite, chert and minor limestone of the Earn Group; chert, tentatively assigned to the Mississippian to Permian Mount Christie Formation; conglomerate and sandstone of possible Tertiary age; and Tertiary to Quaternary mafic volcanics assigned to the Tuya Formation.
Intrusive rocks represent a very minor component of the map area and consist of Early Paleozoic sills and dikes of gabbroic composition, feldspar porphyry dikes of Cretaceous or Tertiary age, and small Early Cretaceous stocks, dikes and sills of broadly granitic composition.
Periodic extensional tectonism during the Paleozoic, which led to the formation and subsequent modification of the Kechika Trough, was followed by intense, easterly directed, compressional tectonics and associated metamorphism of Mesozoic age, resulting in the present structural configuration. Rocks of the trough belong to the Rocky Mountain structural province and structures are dominated by easterly verging folds and thrusts. Thrust faulting predominates in the southern part of the map area where lithologies are dominated by thick, competent Cambrian carbonate and quartzite units. Their disappearance to the north results in a structural style dominated by folding and penetrative cleavage.
Sedimentary exhalative mineralization (sedex) represents the most important mineral deposit type found within the Kechika Trough, ranking it, and the more northerly Selwyn Basin, as one of the most important metallotects of the Canadian Cordillera. These stratiform Zn-Pb-Ag-Ba deposits are found at several stratigraphic levels: Cambrian, Middle Ordovician, Lower Silurian and Upper Devonian. Upper Devonian deposits are by far the most numerous and economically important within the map area, and throughout the Kechika and Selwyn basins. The large Cambrian and Early Silurian deposits found in the Anvil and Howards Pass districts, respectively, highlight the potential that all these horizons have for hosting economically significant sedex deposits. Tungsten-molybdenum porphyry/skarn mineralization related to Early Cretaceous intrusions is the next most important mineral deposit type. Minor lead, zinc and copper-bearing veins are scattered throughout the map area.
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