The Alaskan mineral resource assessment program; background information to accompany folio of geologic and mineral resource maps of the Nabesna Quadrangle, Alaska

Abstract

Mineral production and exploration __________________________ 2 Acknowledgments _________________________________ 2 Geologic investigations ________________________________ 3 Previous geologic and mineral resource investigations ______ 3 Present study ._____________________________________ 3 Geology of the Tanacross quadrangle ________________ 4 Potassium-argon ages from the Tanacross quadrangle _________________-__ 5 Description of component maps of the Tanacross quadrangle folio _________-_-__ 7 Geology (Map 1-593) ______________._________________________ 7 Felsic volcanic rocks ____________________ _________ ____ 7 Mafic volcanic rocks _ _____ __ ____ ___ ______ 10 Syenite of Mount Fairplay _____ ___________ _________________ 13 Geophysics _______________________________________________ 13 Aeromagnetic map and interpretation (Map MF-767A, 2 sheets) _ 13 Gravity map (Map MF-767B) ________________________________ 13 Interpretation of Landsat imagery (Map MF-767C, 3 sheets) ______________ 13 Land status (Map MF-767D) _________ .________ _________________ 15 Mineral resources (Map MF-767E) ________________________________ 15 Reconnaissance geochemistry (Maps MF-767F-O) ______ _____________ 17 Collection of samples-__________________________ 17 Description of sample media ___ ___ _ ___ _____ _______ _ ______ 17 Preparation and analysis of samples__ ___ _________ _____________ 18 Results _____________________________________________ 19 References_____________________________________________ 20 ILLUSTRATIONS FIGURE 1. Index map showing location of Tanacross quadrangle, Alaska _____ _ ________ ______-_ 2. Map showing physiographic provinces of the Tanacross quadrangle and its location in relation to major faults ____________________________________________________________ 3. Map showing potassium-argon ages of rocks from the Tanacross and southern Eagle quadrangles 4. Index map showing localities where revisions are made to the Reconnaissance Geologic Map of the Tanacross quadrangle, Alaska (Foster, 1970) _________________________________________ 5-12. Maps showing: 5.