Basement Tectonic Framework of the U.S.: Role of Cratonization of Juvenile Crust and Structural Modification in Forming Metallogenic Provinces

Science Center Objects

Project objectives were to publish a map of the nation's geologic basement. The map portrayed these pieces (domains) from the most ancient to recent, by the events that influenced their composition, starting with their origin. 

US basement domain map

Figure 1. Basement domains of conterminous United States and Alaska, from USGS Data Series 898.

(Public domain.)

Scientific Issue and Relevance

Large regional (national) resource evaluations can be based on near-surface geology and geologic history and/or on affinity and architecture of the underlying crust. The nature and history of underlying basement is most applicable to evaluating metallogenic provinces (geographic area characterized by a particular assemblage of mineral deposits) and the regional-scale mineralizing processes that operate at lithospheric scales (crust and upper mantle), notably iron oxide-copper-gold (IOGC) and rift-related systems. There are no existing maps of basement affinity and architecture for the entire U.S., so crustal characteristics were generally unavailable for use in previous USGS Mineral Resources Program national mineral resource assessments.

Research Activities

The project's first objective was the development of a U.S. basement terrane map based on basement tectonic processes, the first of its kind for the U.S. The second objective was to investigate 1.7 and 1.4-Ga A-type granites (formed unrelated to collisional tectonics and/or under anhydrous conditions) in relation to the process by which cratons (stable part of continent, typically forms central mass) are formed from juvenile crust and mineralization events.

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