MINERAL POTENTIAL IN THE THUYA BATHOLITH; ASSESSMENT OF MULTIPLE GEOSCIENCE DATASETS

The composite, Early and Middle Jurassic Thuya Batholith, prospective for base and precious metals, occurs in the southern Quesnel Trough (Quesnellia terrane), between well-known Late Triassic porphyry districts at Highland Valley (Cu-Mo) and Afton-Ajax (Cu-Au) to the south and Gibraltar (Cu-Mo) and Mt. Polley (Cu-Au) to the north.

Assessing the mineral potential of the batholith is challenging due to limited exposure, and shallow burial beneath Tertiary volcanic and Quaternary glacial deposits. Multiple approaches are therefore required to evaluate the batholith's mineral potential, including: bedrock and surficial mapping; physical volcanology; high resolution geophysics; till geochemistry; and biogeochemical studies of pine and spruce.

Bedrock mapping indicates a complex multi-episodic intrusion of plutonic phases into locally mineralized, Upper Triassic Nicola Group volcaniclastic and sedimentary rocks. Mafic, intermediate, felsic, syenitic and ultramafic phases are identified. Diorite, syenite and ultramafic phases, dated between 200-195 Ma, host most of the Cu and Au mineralization.

Miocene Chilcotin Group basalt flow rocks cover the mineralized basement rocks but improved models of landscape control on lava facies distribution, and assessment of existing and new geological and geophysical survey data help minimize their well-known impediments to mineral exploration.

High resolution aeromagnetic and radiometric maps refine distribution of host and cover volcanic and granitoid rocks which locally have a strong correlation with aeromagnetic patterns. Other derivative magnetic maps identify cryptic faults.

Surficial mapping and mineralogical and geochemical analyses of till samples indicate that two glacial ice movements resulted in dispersal of gold and base metal minerals and geochemical anomalies to the west and south of their source areas.

More than 500 chemical analyses of outer bark samples from spruce and pine help discern compositionally-distinct bedrock substrate, provide focus for follow up work in areas yielding anomalous levels of metals absorbed by the trees and possibly identify concealed mineralization.

These studies combine to suggest a focus for base and precious metal exploration along the northern and western lobes of the Thuya Batholith.