Geologic History Of The Wyoming Province, One of the Oldest Fragments of Crust in the World

Date & time

1–2pm 25 October 2018

Location

J1 Seminar Room

Speakers

Ronald Frost - University of Wyoming

Event series

Contacts

 Kial Stewart

The Wyoming province consists of Precambrian rocks that are exposed in the Laramide uplifts in the Rocky Mountains of Wyoming.  The province records a long history with rocks dating back to 3.4 billion years ago (Ga) and xenocrystic zircon grains dating to ca. 3.9 Ga.  Lu/Hf ratios on some of the xenocrystic zircons indicate an ancestry that goes back into the Hadean.  The earliest granitic rocks at 3.4 Ga are tonalitic.  Potassium-rich plutons, indicative of granites derived from crustal melting, were emplaced 3.3 Ga, indicating that evolved continental crust in the Wyoming province had formed at that time.  The majority of the province is composed of variably deformed granitic plutons that were emplaced 2.85 Ga, 2.7 Ga., and 2.62 Ga.  Like Phanerozoic continental arc magmas, these plutons contain contributions from both continental and juvenile components.  The formation of early continental crust in Wyoming province may explain why it records the earliest Himalayan-type orogeny on Earth at 2.7 Ga.  It is possible that the Wyoming province and the Slave province, which is now located in northern Canada, formed from the same Hadean-Paleoarchean craton that was rifted apart around 2.86 Ga, but correlation with other Archean provinces that contain Hadean roots is more speculative.

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