Mid-Cretaceous and Paleocene magmatism and porphyry mineralization in the Llewellyn fault corridor, northwestern British Columbia

Establishing the timing and duration of magmatism, mineralization, and deformation leading to the development of porphyry systems is key to identifying prospective regions within orogenic belts. The Blue Property in the Atlin Lake area in northwestern British Columbia is characterized by Mo–Cu porphyry, skarn, and carbonate replacement mineralization (“Laverdiere”, “Sulphide City”, and “Jackie” occurrences). This ore deposit system is hosted in the polymetamorphic Florence Range and Boundary Ranges metamorphic suites and felsic intrusive rocks. In this contribution, we combine detailed field mapping and igneous petrography with U–Pb zircon and titanite petrochronology to elucidate the magmatic history of these mineralized systems. Results indicate two distinct periods of magmatic and mineralizing activity at ca. 103–102 Ma and ca. 60–56 Ma and reflect the potential longevity and overprinting nature of mineralization related to the Coast Plutonic Complex in this region. Trace element signatures from analyzed zircons are similar to those from porphyry indicator zircons in large Andean porphyry deposits. Magmatic events are compared to similar porphyry systems occurring in northwestern British Columbia and southern Yukon within the Dawson Range batholith, and Ruby Range and Sloko-Hyder intrusive suites. Therefore, in this region, new age constraints illustrate the prospectivity of the Atlin Lake area and link the deposits at the Blue Property to a broader trend of mid-Cretaceous and Paleocene–Eocene porphyry-style mineralization.