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Early Tertiary Slab Window in Alaska and its Resource Implications

Between 61 and 50 million years ago, an oceanic spreading center was subducted beneath Alaska causing a plutonic and metamorphic event that swept from west to east along a 2100-km-long portion of Alaska's Pacific margin.

Principal Investigators:
Bradley, Dwight C.

Project Contacts:
Bradley, Dwight C., dbradley@usgs.gov, 907-786-7434


Status: completed
Start Year: 2001
End Year: 2005

Location:

USGS Mission Area and Program:
Energy and MineralsMineral Resources

Web Links:
Alaska Mineral Resources

Keywords:
Solid Earth > Natural Resources > Metals
Solid Earth > Tectonics > Plate Tectonics

Abstract


Between 61 and 50 million years ago, an oceanic spreading center was subducted beneath Alaska. "Ridge subduction" is now recognized as the cause of a plutonic and metamorphic event that swept from west to east along a 2100-km-long portion of Alaska's Pacific margin. This project is investigating the broader geologic corollaries of ridge subduction. We are testing the idea that a "slab window" (a gap between two subducted but still diverging plates) had widespread geologic effects as far as 1000 km inland: volcanism, plutonism, deformation, metamorphism, mineralization, basin subsidence, uplift of mountain belts, and hydrocarbon genesis. The slab window was analogous to a moving blowtorch, heating the earth's crust from below. Ridge subduction is inevitable on a world covered with plates: there are six present-day examples and probably hundreds of past instances related to former plate configurations. Before this project, little was known about the far-field effects of ridge subduction and attendant slab windows, or the implications for genesis of mineral and energy resources. Thus the project has the potential to aid in resource assessment worldwide.

Project metadata record

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