The Pine, Fin, and Mex porphyry Au-Cu ± Mo systems are all located within a 10 km² area in the
Toodoggone district, along the eastern margin of the Stikine terrane in British Columbia. Multiple
episodes of porphyry-style mineralization are associated with these three magmatic centres. The Fin
monzogranite is the oldest dated pluton in the district, with a U-Pb zircon emplacement age of 217.8 ± 0.6
Ma. A cross-cutting main-stage quartz-pyrite-chalcopyrite ± molybdenite ± sphalerite vein gives an older
Re-Os molybdenite mineralization age of 221.0 ± 1.4 Ma. Hence the vein probably cross-cuts a slightly
older, undated magmatic phase. Lead isotope values for sulphide minerals from main-stage veins indicate
that magmatic-derived fluids interacted with country rocks and possibly other fluids.
The Pine quartz monzonite (U-Pb zircon emplacement age of 197.6 ± 0.5 Ma) intrudes, alters,
and locally mineralizes Toodoggone Formation Duncan Member andesite tuff (U-Pb zircon age of 200.9
± 0.4 Ma). High-grade (0.57 g/t Au and 0.15% Cu) mineralization occurs in main-stage quartz-magnetite
chalcopyrite-pyrite veins and disseminated throughout the potassic alteration zone in the Pine quartz
monzonite stock. Late-stage anhydrite-pyrite ± specular hematite ± chalcopyrite, quartz-pyrite ±
chalcopyrite, and pyrite ± chalcopyrite veins and related phyllic alteration cross-cut earlier veins.
Propylitic alteration occurs distal to the potassic core of Pine in the Fin monzogranite and Duncan
Member andesite. Limited fluid inclusion data, in combination with S and Pb isotope values for veins and
host rocks, suggest that the main-stage fluid was magmatic-derived and deposited metals at 430 to 550 °C
and depths of about 5.5 km. Late-stage fluids were also probably derived from the Pine quartz monzonite
but interacted with Takla Group country rock prior to metal deposition. Metals were deposited at
temperatures of 330 to 430 °C and depths of about 5.0 to 5.5 km.
The final mineralization phase of the Pine porphyry system is temporally constrained by the
emplacement of weakly mineralized syenite dykes (U-Pb zircon age of 193.8 ± 0.5 Ma). The final stage
of magmatism in the Pine-Fin-Mex area is defined by the emplacement of rhyolite dykes (U-Pb zircon
age of 193.6±0.4 Ma).
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/3959 |
| Date | 05 1900 |
| Creators | Dickinson, Jenni Michelle |
| Publisher | University of British Columbia |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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