U-Pb Ages of Intrusive Rocks and Ar/Ar Plateau Ages of Copper-Gold- Silver Mineralization Associated with Alkaline Intrusive Centres at Mount Polley and the Iron Mask Batholith, Southern and Central British Columbia

Por phyry de pos its in Brit ish Co lum bia have pro duced more than $27 bil lion worth of cop per and gold. They formed dur ing two dis tinct pe ri ods in the de vel op ment of the Cor dil lera: the first in the Late Tri as sic to Early Ju ras sic and the sec ond in the Cre ta ceous to Eocene. Most por phyry pro duc tion has come from the south ern part of Quesnel Terrane, where two cy cles of calcalkaline through al ka line magmatism are rec og nized in the Late Tri as sic and Early Ju ras sic. The rea son for the ca. 10 Ma cy cle of early calcalkaline and later al ka line vol ca nism, plutonism and min er al iza tion is not fully re solved, but the same pat tern re peated in the cen tral and north ern parts of the terrane sug gest a feature fundamental to the Quesnel Arc genesis.