Bulletin 107:
Geology and Mineral Deposits of the Northern Kechika Trough
Between Gataga River and the 60th Parallel
by Filippo Ferri, Chris Rees, JoAnne Nelson and Andrew Legun
Table of Contents
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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)
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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. |
Last Updated
June 05, 2007 |
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