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Ministry of Energy Mines and Responsible for Core Review

Bulletin 54: Geology of the Queen Charlotte Islands British Columbia

by A. Sutherland Brown 

Table of Contents

Cover, Summary, Table of Contents (PDF document, 391 Kb)
Chapter One: Introduction
(PDF document, 506 Kb)
Chapter Two: Physiography and Glacial and Recent Geology (PDF document, 764 Kb)
Chapter Three: General Geology
     Pages 37-73 (PDF document, 2.1 Mb)
     Pages 74-112 (PDF document, 2.2 Mb)
     Pages 113-146 (PDF document, 1.9 Mb)
Chapter Four: Structural Geology (PDF document, 886 Kb)
Chapter Five: Mineral Resources
     Pages 165-194 (PDF document, 2.0 Mb)
     Pages 195-220 (PDF document, 1.8 Mb)
Appendix and index (PDF document, 280 Kb)
Photos (PDF document, 1.9 Mb)
Black and white maps and tables (PDF document, 1.6 Mb)
Map Sheet A (PDF document, 5.3 Mb)
Map Sheet B (PDF document, 9.0 Mb)
Map Sheet C (PDF document, 8.8 Mb)

Cross-Sections (PDF document, 681 Kb)

Bulletin 54 discusses the geology and mineral deposits and considers the exploration potential of the Queen Charlotte Islands, which are at the western edge of the continental shelf seaward of central British Columbia.  The islands have a land area of about 3,840 square miles, which is divided into three main physiographic units: the Queen Charlotte Ranges on the southwest, Skidegate Plateau in the centre, and Queen Charlotte Lowlands on the northeast.  In the Pleistocene the islands were intensively glaciated.

The fundamental structural unit of the Queen Charlotte Islands is a thick (15,000+ feet) pillowed basalt of Late Triassic age.  The basalts are separated by a flysch-like sequence of Latest Triassic and Early Jurassic age from an explosive porphyritic andesite of Middle Jurassic age and largely marine deposition.  Two Cretaceous sedimentary units, the first flysch-like and the second mollasse-like, were deposited and are successively less involved in deformation.  A final Early Tertiary period, largely of subaerial volcanism, deposited some 18,000 feet of intercalated columnar alkali basalt floods and sodic rhyolite ash flows.  These are gently warped, eroded, and overlain by up to 6,000 feet of Mio-Pliocene sands and shales.  Large lineal bodies of hornblende diorite to quartz diorite were emplaced in the Mid to Late Jurassic and a more varied sequence of quartz diorite to soda granite in the Early Tertiary, mostly along major lineal faults.

Crustal fracturing has been the dominant mechanism of deformation, controlling volcanism, sedimentation, intrusion, and secondary folding. Major north westerly lineal faults form a pattern related to the Queen Charlotte fault.  The trace of the latter is along the continental slope.  The major northwesterly faults have been active since at least the Early Cretaceous, and generally they combine right-hand wrench movement with normal east-block-down displacement.

The mineral resources of the islands are extensive.  At present pyrometasomatic iron-copper deposits are the most important by several orders of magnitude but the potential for gold mineralization is high.  Mineable reserves have a gross value of about $200 million.  Production has come from two main properties-Tasu and Jedway.

 

All printed publications of the BC Geological Survey are available digitally, free of charge, from this website.

 

For questions or more information on geology and minerals in British Columbia contact BCGS Mailbox or call toll free (BC Residents only).