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Geology and Magmatic-Hydrothermal Evolution of the Giant Pebble Porphyry Copper-Gold-Molybdenum Deposit, Southwest Alaska
| Content Provider | CiteSeerX |
|---|---|
| Abstract | The Pebble deposit is located ~320 km southwest of Anchorage, Alaska. It is one of the largest porphyry deposits known with a total resource of 10.78 billion tons (Bt). It comprises the East and West zones, which are approximately equal in size, with slightly lower grade mineralization in the center of the deposit where the peripheries of the two zones merge. The West zone was discovered by Cominco America in 1989 and the East zone was discovered by Northern Dynasty Minerals in 2005. The oldest rock in the Pebble district is the Jurassic-Cretaceous Kahiltna flysch unit, which contains basinal turbidites, interbedded basalt flows, and associated gabbro intrusions. These rocks were intruded between 99 and 96 Ma by coeval granodiorite and diorite sills, followed shortly thereafter by alkalic monzonite intrusions and related breccias. Subalkalic hornblende granodiorite porphyry plutons of the Kaskanak batholith were emplaced at ~90 Ma. Similar, smaller granodiorite plutons were emplaced around the margins of the batholith and are related to Cu-Au-Mo mineralization. Re-Os dates on molybdenite are between 89.7 and 90.4 Ma. A Late Cretaceous volcanic and sedimentary ”cover sequence ” completely conceals the East zone, whereas the West zone is overlain only by glacial sediments and is exposed in one small outcrop. Eocene volcanic rocks and subvolcanic intrusions occur east and southeast of the Pebble deposit and unconsolidated glacial sediments are |
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| Content Type | Text |
