The magmatic-hydrothermal evolution of the Camp Creek porphyry deposit, northwestern British Columbia

Camp Creek is a Late Cretaceous porphyry Cu-Mo-(Au-Ag) deposit in the Stikine island-arc terrane in northern British Columbia. Late Triassic sedimentary and volcanic rocks of the Stuhini Group host hornblende-quartz-biotite-plagioclase porphyritic phases of the Thorn Stock, which are difficult to distinguish in the field due to limited cross-cutting relationships and intense hydrothermal alteration. Integration of field observations, drill core relogging, and petrography, supported by whole-rock geochemistry and high precision U-Pb zircon geochronology (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) has defined the Thorn Stock as three compositionally near-identical porphyritic phases. These include pre-mineral diorite PY (~86.9 Ma), syn-mineral quartz diorite PX (~86.3 Ma, contemporaneous with Re-Os molybdenite dated to 86.60 ± 0.36 Ma), and late-mineral quartz diorite PZ (~86.2 Ma), establishing Camp Creek as a multiphase magmatic system that was rapidly emplaced over ~726 kyr. New laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb geochronology constrains two post-porphyry dyke episodes at ~83-85 Ma (late-mineral PV1 and PV2) and at ~52-75 Ma (post-mineral DKFL, DKIN, and DKMF). The integrated comparison of four-acid digestion (4AD), portable X-ray fluorescence (pXRF) and lithium borate fusion (LBF) datasets demonstrates that 4AD systematically under-reports the high field strength elements (HFSE; Hf, Zr, Nb, and Ta) and Ti relative to the more complete LBF and pXRF methods. This discrepancy is mineralogically controlled by refractory magmatic (e.g., zircon) and alteration-derived (e.g., rutile and titanite) mineral phases. Hydrothermal alteration and mineralization are zoned from a near-surface advanced argillic lithocap (pyrophyllite ± diaspore ± dickite), which transitions downward through white, pale-green, and green muscovite, to a deep K-silicate core correlating with Cu-Mo mineralization, PX, and the Stuhini Group. Vectors demonstrated to effectively track this zoning include alteration intensity, vein type, vein density (enargite-tennantite-pyrite, pyrite, and quartz veins), white mica composition (paragonitic to phengitic), white mica crystallinity, and pathfinder elements (distal Bi, Mn, Te, Pb, Zn, Tl, As to proximal Cu, Mo, and W). The short-lived, fertile magmatism at Late Cretaceous Camp Creek expands the known metallogenic prospectivity of the northern Stikine terrane, and the vectoring tools used here can be applied to wider porphyry exploration in British Columbia.