Granitic rocks of the Topley intrusives underlying 100
square miles, centered around Endako, north central British
Columbia, form part of a composite body which lies in a northwest
trending belt of granitic plutons extending from Babine Lake to
Quesnel, a distance of 180 miles.
Rocks of the Topley complex in the Endako area have intruded
volcanic rocks of the Takla Group (Upper Triassic to Jurassic) and
are unconformably overlain by flat-lying Tertiary volcanic flows.
These intrusions are probably of Lower Jurassic to Lower Cretaceous
age. The granitic rocks, ranging from diorite to alaskite form six
large separately emplaced and sharply bounded intrusive bodies.
The development of the Topley complex can be divided chronologically,
from oldest to youngest, into five major stages: (I) the Simon Bay
(diorite) complex; (II) the Endako quartz monzonite which is the host
rock of the Endako molybdenum deposit, and the Franco is granite;
(III) the Glennanan complex; (IV) the Casey quartz monzonite-alaskite;
and (V) the Stellako quartz monzonite. The Glennanan complex, which is the best exposed and most
intensely studied intrusive, consists of two large asymmetrically
zoned bodies and a small stock of porphyritic quartz monzonite. The
larger zoned body near the town of Endako has: (1) a western zone
of porphyritic granite; (2) an intermediate zone of porphyritic quartz
monzonite; and (3) an eastern zone of porphyritic granodiorite.
A granodiorite zone is absent in the asymmetrically zoned Nithi
Mountain intrusive body. All internal contact are gradational and
all rock zones contain large rectangular perthite megacrysts which
enclose oriented crystals of plagioclase and other minerals. The
development of the rock zones can be accounted for by differentiation
of a hornblende-biotite granodiorite magma at depth and successive
intrusion of first granite, then quartz monzonite and finally granodiorite.
Topley stages II to V represent a continuous period of epizonal
intrusion following the emplacement of the more deep seated
(mesozonal?) Simon Bay complex. Northwesterly and northeasterly
trending fracture zones controlled the structural evolution of the
Topley complex in the map area. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/41714 |
| Date | January 1967 |
| Creators | Bright, Edward Gordon |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
Page generated in 0.0021 seconds