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Bulletin 93:
Geology and Platinum-Group-Element Mineralization of Alaskan-Type Ultramafic-Mafic Complexes in British Columbia
By G. T. Nixon
J. L. Hammack, C. A. Ash, L. J. Cabri, G. Case, J. N. Connelly, L. M.
Heaman, J. H. G. Laflamme, C. Nuttall, W. P. E. Paterson and R. H. Wong
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| Alaskan-type ultramafic-mafic complexes are potentially one of
the most important hosts for economic concentrations of platinum-group
elements (PGE) in the Cordillera. Bulletin 93 summarizes the geology and
noble metal geochemistry for most of the major Alaskan-type intrusions in
British Columbia, including the Tulameen, Polaris, Lunar, Wrede, Johanson,
Menard, Gnat Lakes and Hickman bodies. New U-Pb zircon dates and
analytical data for the PGE are presented in addition to revised
geological maps (1:10 000-1:20 000 scale, in colour) for the Tulameen,
Polaris, Lunar and Wrede complexes. A case study of the
platinum-group-element mineralogy and associated oxide and silicate
minerals forming PGE-chromitite occurrences in the core of the Tulameen
complex, and impure platinum nuggets in nearby placers, establishes a
first-order genetic link despite fundamental differences in the speciation
of the PGE. The geochemical signature of PGE derived from Alaskan-type
intrusions is distinctive and sufficiently robust to serve as a valuable
exploration tool, and should encourage the careful analysis of panned
concentrates in prospecting for PGE. |
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Table of Contents:
Maps: |
Cover
and Table of Contents (PDF document, 2.1 Mb)
Note: This PDF file also contains the document title page, CIP
information and Table of Contents.
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Chapter
1 - Introduction
(PDF document, 1.1 Mb)
Alaskan-Type
Complexes; General Nature and Tectonic Setting; Acknowledgments.
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Chapter
2 - Hickman Complex
(PDF document, 1.6 Mb)
Regional Geology and Geochronometry; Country Rocks; Stuhini Group; Hickman Pluton; Hickman
Complex: Ultramafic-Mafic Rocks; Dunite; Olivine Clinopyroxenite and Clinopyronenite; Gabbroic Rocks; Contact Relationships; Dikes; Structure
and Metamorphism; Mineralization; Geochemistry; Summary.
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Chapter
3 - Gnat Lakes Complex
(PDF document, 2.0 Mb)
Regional Geology and Geochronometry; Country Rocks; Stuhini Group; Cake Hill Pluton (Stikine
Plutonic Suite); Three Sisters Pluton (Three Sisters Plutonic Suite);
Gnat Lakes Complex:; Mafic-Ultramafic Rocks; Petrography and Mineral
Chemistry; Contact Relationships; Structure and Metamorphism;
Geochemistry; Summary.
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Chapter
4 - Lunar Creek Complex
(PDF document, 5.6 Mb)
Regional Geology and K-Ar
Geochronometry; Country Rocks; Takla Group; Asitka Group; Lunar Creek
Complex:; Mafic-Ultramafic Rocks; Dunite; Chromitite; Olivine
Clinopyroxenite and Clinopyroxenite; Mixed Ultramafic Lithologies;
Layered Mixed Units; Chaotic Mixed Zones; Replacement Dunite; Gabbroic-Dioritic
Rocks; Folialed Gabbro-Diorite; Massive Gabbro-Diorite; Quartz-Feldspar
Veins; Granitoid Rocks of the Pitman Batholith; Plagioclase Porphyry
dikes; Hornblende Microdiorite Dikes; U-Geochronometry; Structure;
Mineralization; Geochemistry; Summary.
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Chapter
5 - Menard Creek Complex
(PDF document, 1.1 Mb)
Regional Geology;
Country Rocks: Takla Group; Menard Creek Complex:; Mafic-Ultramafic
Rocks; Clinopyroxenite; Gabbroic Rocks; Mafic Dikes; Contact
Relationships; Structure and Metamorphism; Mineralization and
Geochemistry; Summary.
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Chapter
6 - Wrede Creek Complex
(PDF document, 3.1 Mb)
Regional Geology and Geochronometry; Country Rocks: Takla Group; Wrede Creek Complex:
Ultramafic-Mafic Rocks; Dunite; Chromitite; Clinopyroxenite; Olivine
Clinopyroxenite and Clinopyroxenite; Hornblende Clinopyroxenite and
Olivine-Hornblende Clinopyroxenite; Homblendite and Hornblende Gabbro-Diorite;
Minor Intrusions; Ultramafic Dikes; Pegmatite Dikes; Contact Aureole;
Granitoid Intrusions; Structure and Metamorphism; Mineralization; Chromite
and Platinum; Sulphides; Noble Metal Geochemistry; Summary.
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Chapter
7 - Johanson Lake Complex
(PDF document, 3.3 Mb)
Regional Geology and Geochronometry; Country Rocks: Takla Group; Johanson Lake Complex:;
Mafic-Ultramafic Rocks; Clinopyroxenite; Hornblende Clinopyroxenite and
Clinopyroxene Homblendite; Gabbroic to Dioritic Rocks;
Hornblende-Plagioclase Porphyry; Minor Intrusive Rocks; Granitoid Rocks;
Structure and Metamorphism; Noble Metal Geochemistry and Mineral
Potential; Summary.
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Chapter
8 - Polaris Complex
(PDF document, 6.3 Mb)
Regional Geology and Geochronometry; Country Rocks: Lay Range Assemblage; Polariscomplex:
Ultramafic-Mafic Rocks; Dunite; Chromitite; Olivine Wehrlite and Wehrlite; Olivine Clinopyroxenite
and Clinopyroxenite; Mixed
Wehrlitic-Pyroxenitic Units; Hornblende Clinopyroxenite and Homblendite;
Gabbroic to Dioritic Rocks; Dikes and Veins; Contact Relations and
Intrusion Geometry; Internal Stratigraphy; Mechanism of Emplacement;
Contact Aureole; Minor Intrusions; U-Pb Geochronometry; Structure and
Metamorphism; Alteration and Mineralization; Geochemistry; Summary.
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Chapter
9 - Tulameen Complex
(PDF document, 6.1 Mb)
Regional Geology and Geochronometry; Country Rocks; Nicola Group; Princeton Group; Mount
Lytton - Eagle Plutonic Complex; Tulameen Complex: Mafic-Ultramafic
Rocks; Dunite; Chromitite; Olivine Clinopyroxenite; Hornblende
Clinopyroxenite; Minor Ultramafic Lithologies; Gabbroic to Dioritic
Rocks; Magmatic Stratigraphy: Tulameen River Section; Olivine
Clinopyroxenite; Gabbro-Diorite; Contact Relationships; Nicola -
Ultramafic Rocks; Gabbroic Ultramafic Rocks; Dunite - Olivine
Clinopyroxenite; Olivine Clinopyroxenite Hornblende; Clinopyroxenite;
Summary of Contact Relationships; Structure; Regional Foliation; Chromitite Schlieren; Brittle
and Ductile Faults; Mineralization and
Geochemistry; Summary: Structural and Emplacement history.
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Chapter
10 - Platinum Group-Element Mineralization
(PDF document, 9.9 Mb)
Noble Metal Geochemistry of Alaskan-Type Complexes
; Platinum-Group Minerals in the Tulameen
Complex and Associated Placers -A Case Study; Chromitite Specimens;
Placer Nuggets; Petrography and Mineralogy of Chromitites;
Platinum-Group Minerals; Base Metal Minerals; Petrography and Mineralogy
of Placer Nuggets; Holland Nugget; Lincoln Nugget.; M12410 Nuggets;
Platinum-Group Minerals in Bedrock Versus Placers; Chemistry of Chromite
and Silicate Minerals; Chromite; Olivine; Silicate Inclusions in
Nuggets; Origin of Platinum Nuggets: the Chromitite Connection;
Significance of Primary Silicate; Inclusions; Paragenesis of the
Platinum-Group; Minerals; Sulphides; Summary of PGE Mineralization in
the Tulameen Complex; Economic Potential of Alaskan-Type Complexes -PGE
as an Exploration Tool; PGE Mineralization in Alaskan-Type Versus; Stratiform
and Ophiolitic Complexes.
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Chapter
11 - Magmatic and Tectonic Setting of Alaskan-Type Complexes
(PDF document, 2.5 Mb)
The Longevity of Mesozoic Arc Magmatism in Quesnellia
and Stikinia; Timing of Early Mesozoic Deformation and Terrane
Accretion; Tectonic Setting of the Tumagain Complex and Strike-Slip Displacements
in Central British
Columbia.
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References
(PDF document, 2.6 Mb)
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Appendices
(PDF document, 1.3 Mb)
A. Interim Reports On
Alaskan-Type Complexes; B. U-Pb Analytical Techniques; C. Location of Geochemical Sample Sites, Tulameen;
Complex; D. Sample Preparation and Microbeam Techniques.
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