Metallogenesis and tectonics of porphyry copper and molybdenum (gold, silver) and granitoid-hosted gold deposits of Alaska

Special Volume, Vol. SV 46, No. 1995, 1995
Porphyry copper-gold, porphyry molybdenum, granitoid-hosted gold, and associated lode deposits occur in several metallogenic belts throughout Alaska. Generally, the older metallogenic belts occur to the north, in interior and northern Alaska, whereas the younger belts occur to the south or west, closer to the Pacific Ocean margin of Alaska. Five older, pre-accretionary metallogenic belts, that formed before tectonic juxtaposition of hasting tectonostratigraphic terranes, occur in Alaska: (1) The middle Paleozoic Brooks Range metallogenic belt occurs along the southern flank of the Brooks Range in northern Alaska, contains porphyry copper and molybdenum (gold, silver) occurrences (Geroe Creek, Victor, Venus, Evelyn, Lee, Ebo), and is interpreted as having formed in a continental margin arc tectonic setting. (2) The early to middle Paleozoic Prince of Wales Island metallogenic belt occurs in southern southeastern Alaska and contains major porphyry copper-molybdenum and associated deposits at McLean Arm, Klakas Inlet, and Kasson Peninsula, and is interpreted as having formed in an island arc tectonic setting in the early history of the Alexander terrane. (3) The late Paleozoic Alaska Range-Wrangell Mountains metallogenic belt occurs in interior Alaska, contains porphyry copper occurrences (Chistochina, Slate Creek), and is interpreted as having formed in an island arc tectonic setting as part of the Skolai arc. (4) The eastern-southern Alaska metallogenic belt contains major porphyry copper and molybdenum, and granitoid-hasted gold deposits (Baultoff, Bond Creek, Carl Creek, Horsfeld, Orange Hill). (5) The western-southeastern Alaska metallogenic belt contains a porphyry molybdenum deposit (Baker Island). The eastern-southern Alaska and western-southeastern Alaska metallogenic belts are interpreted as having formed in the Late Jurassic and Early Cretaceous Gravina island arc.
Several post-accretionary metallogenic belts, that formed after tectonic juxtaposition of terranes to the North American continental margin, occur in southern and southeastern Alaska. They contain porphyry copper and molybdenum (gold, silver), granitoid-hosted gold, and associated lode deposits. (1) The westcentral Alaska (Hodatza) metallogenic belt contains major porphyry copper-gold deposits at Indian Mountain, Purcell Mountain, and Zane Hill. (2) The southwestern Kuskokwim Mountains, east-central Alaska, and southern Alaska metallogenic belts occur in southwestern, east-central Alaska, and southern Alaska, respectively. These metallogenic belts contain major porphyry copper-gold, gold, and copper-molybdenum, and granitoid-hosted gold deposits at Beaver Mountains, Chicken Mountain, Democrat, Donlin Creek, Fort Knox, Fox Hills, Golden Zone, Independence Mine, Kijik River, McLean, McLeod, Molybdenum Mountain, Pebble Copper, Taurus, Vinesale Mountain, Von Frank Mountain. The westcentral, southwestern Kuskokwim Mountains, east-central Alaska, and southern Alaska metallogenic belts are interpreted as having formed in the tectonically-dismembered, Late Cretaceous and early Tertiary Kluane continental margin arc that formed along the southern margin of proto-Alaska. (3) The Alaska Peninsula and Aleutian Islands metallogenic belt contains a major porphyry copper deposit at Pyramid, and a porphyry molybdenum occurrence at Mike, and is interpreted as having formed in the middle Tertiary through Holocene continental margin Aleutian arc. (4) The central-southeastern Alaska metallogenic belt contains major porphyry copper and molybdenum deposits (Nunatak, Margerie Glacier, Quartz Hill), and is interpreted as having formed in a middle to late Tertiary continental margin arc setting as part of the Glacier Bay magmatic belt and Tkope-Portland Peninsula volcanic-plutonic belt.
Keywords: Porphyry copper-gold deposits, Porphyry molybdenum deposits, Granitoid-hosted
gold deposits, Associated lode deposits
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