Geochronology of mid-Cretaceous to Eocene magmatism, Babine porphyry copper district, central British Columbia

摘要: New U/Pb and 40 Ar/ 39 Ar isotopic dating in the Babine porphyry copper district of central British Columbia documents three distinct magmatic events at 107-104, 85-78, 54-50 Ma. The earliest event involved emplacement rhyolite domes into submarine volcanic rocks Rocky Ridge Formation. related dacitic to basaltic gave a U-Pb age 107.9 ± 0.2 Ma an 104.8 1.2 rhyolites, which were previously mapped as Eocene, are reinterpreted be part unrecognized mid-Cretaceous cauldron subsidence complex. regionally extensive Late Cretaceous is also recognized represented by ages 85.2 2.8 78.3 0.8 on two Bulkley intrusions, one has associated mineralization. final most widespread intrusions formation numerous deposits including Bell Granisle past producers. Twenty-one new for these coeval andesites Newman Formation have narrow range from 53.6 0.9 49.9 0.6 Ma, whereas previous K-Ar had possible 15 mid-Cretaceous, Cretaceous, Eocene suites dis- trict interpreted long-lived volcano-plutonic complex that was site periodic magmatism mineralization over 60 time period. This may evolved within zone extension (pull-apart basins) situated between dextral strike-slip faults active during periods rapid oblique plate con- vergence.