New U-Pb age constraints at Freegold Mountain: Evidence for multiple phases of polymetallic mid- to Late Cretaceous mineralization

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Abstract

In this contribution, we present new U-Pb age data for ten intrusive units that bracket the timing of polymetallic mineralization occurring within the Northern Freegold Resources Ltd. (NFR), Freegold Mountain project area. Polymetallic mineralization occurring in the Tinta zone predates trachytic dykes (~109 Ma) and represents the earliest phase of mineralization recognized on the Freegold
Mountain property thus far. Feldspar porphyry dykes that intrude the Revenue zone are correlative to the Nucleus zone feldspar porphyry dykes, and yield ages of ~105-104 Ma, indicating that the structural corridor in which Au mineralization occurred was active from at least this time. Furthermore, monzodiorite was emplaced at ~107 Ma within the Revenue zone. An ~97 Ma aplitic dyke that intrudes porphyritic granite of the Stoddart intrusion predates ~94 Ma Mo-Cu-W mineralization. Andesitic dykes (~77 Ma) that crosscut the Stoddart porphyry and rhyolitic dykes (~75 Ma) intruding the Revenue zone, represent Carmacks-age volcanism in the region. These new age data indicate that economically important mineralizing events took place over a period of at
least 40 Ma
Original languageEnglish
JournalYukon Exploration and Geology 2009
Publication statusPublished - 2010

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