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Geologic Framework - Southwest Alaska

Regional Geologic, Geochemical, Geophysical, and Mineral Deposit Data for Economic Development in Alaska in the 21st Century

Photo of outcrop in Taylor Mountains quadrangle

The Taylor Mountains quadrangle has long been recognized as a gap in the geologic framework of southwest Alaska. Information gleaned from the better-known areas around it suggests that this quadrangle holds key information for unraveling the tectonic evolution of the region. Contained within the quadrangle is the complex juncture between the Togiak arc (and related oceanic assemblages) and the Farewell terrane (a continental fragment). Partly obscuring this suture zone (and possibly other sutures as well) are extensive Cretaceous flysch sequences. Intruding and overlying both the amalgamated terranes and the overlapping flysch are volcanic-plutonic complexes. Unravelling and understanding these geologic sequences are vital components for assessing the undiscovered resource potential.

One aspect of the research will be to obtain, analyze, and interpret major, minor, and trace element whole-rock geochemical data from the intrusive and volcanic rocks that crop out in the Taylor Mountains quadrangle. Data will be compared with previous and newly acquired geochemical data for similar rocks in the Sleetmute quadrangle to the north. Elemental ratios will be used to determine the chemical variability and tectonic affinity of latest Cretaceous and early Tertiary magmatism. The geochemistry samples also could be used for geochronology (U-Pb), radiogenic isotope determinations (Nd), and petrophysical measurements (magnetic susceptibility and density).

Experience in Iditarod and Sleetmute quadrangles to the north shows that despite mediocre outcrop, the geology is tractable, and that reconnaissance mapping can yield extremely important findings (such as the discovery of Proterozoic crust and the definition of the Tertiary and older strike-slip history of the Denali Fault). Like the quadrangles to the north, the Taylor Mountains quadrangle is also expected to contain additional undiscovered gold, tin, and mercury resources similar to the known properties at Taylor Mountains, Sleitat, and Cinnabar Creek.

New regional aeromagnetic geophysical data for the Taylor Mountains Quadrangle has significantly enhanced the geologic mapping effort by highlighting known and unknown regional structures. In-situ measurements of magnetic susceptibility will help in interpreting the aeromagnetic anomalies and possibly assist in outlining geologic units that are difficult to distinguish in the field.

Geologic features in the Taylor Mountains quadrangle

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Last Modified: 21 April 2017