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A Comparative Study Of The Badger Pass Igneous Intrusion And The Foreland Volcanic Rocks Of The Mcdowell Springs Area, Beaverhead County, Montana: Implications For The Local Late Cretaceous Sequence Of Events, Brookie Jean Gallagher
A Comparative Study Of The Badger Pass Igneous Intrusion And The Foreland Volcanic Rocks Of The Mcdowell Springs Area, Beaverhead County, Montana: Implications For The Local Late Cretaceous Sequence Of Events, Brookie Jean Gallagher
Geosciences Theses
Intermediate igneous rocks exposed in the Badger Pass area and 3.5 km away in the McDowell Springs area of Beaverhead County, Montana, previously mapped as Cretaceous intrusive (Ki), and Cretaceous undifferentiated volcanics (Kvu) respectively, exhibit little geochemical variation. Trace element, and lead isotope analyses provide strong evidence allowing for a single source. REE patterns, obtained through ID-ICP-MS, are essentially identical. Mineral/melt Eu analyses reveal that Eu behaved predominantly as a divalent cation, refuting an earlier study asserting that trivalent Eu dominated. Data suggest rocks were formed under low oxygen activity conditions, not oxidizing conditions as previously reported. Geochemical data combined …