Archean crustal growth by lateral accretion of juvenile supracrustal belts in the south-central Wyoming Province

2006 ◽  
Vol 43 (10) ◽  
pp. 1533-1555 ◽  
Author(s):  
Carol D Frost ◽  
Benjamin L Fruchey ◽  
Kevin R Chamberlain ◽  
B Ronald Frost
Keyword(s):  
Plate Tectonics ◽  
Crustal Growth ◽  
Klamath Mountains ◽  
The South ◽  
Wind River Range ◽  
South Central ◽  
Metavolcanic Rocks ◽  
Wyoming Province ◽  
Terrane Accretion ◽  
Geologic Processes

Neoarchean supracrustal sequences in the south-central Wyoming Province are exposed as relatively small belts in Laramide uplifts. Some sequences are composed of materials derived mainly from pre-existing Wyoming province crust, but others are dominated by juvenile components. The latter include the Miners Delight Formation in the Wind River Range, the Rattlesnake Hills Group in the Granite Mountains, and the Bradley Peak succession in the Seminoe Mountains. U–Pb zircon dates from interbedded metavolcanic rocks suggest that these supracrustal belts are of at least two different ages: ca. 2.67 and ca. 2.72 Ga. We identify a time of contractional deformation and accretion of some of these supracrustal packages to the southern Wyoming Province at ~2.65–2.63 Ga. Magmatism is nearly synchronous with deformation. Some granitoids intrude the Wyoming Province basement, as well as the juvenile rocks thrust onto this basement; these have Nd isotopic compositions indicating that these plutons assimilated some old continental basement during ascent. Plutons intruding the supracrustal rocks located farther from the margin do not show this continental influence. The time scale and geologic processes of deposition, contractional deformation, and plutonism appear analogous to Phanerozoic examples of oceanic terrane accretion, such as formed the Klamath Mountains Province of California and Oregon. We conclude that a major episode of Neoarchean crustal growth involved both the lateral accretion of juvenile terranes and the intrusion of arc magmas formed from mantle-derived and (or) juvenile crustal sources and was driven by geologic processes very similar to modern plate tectonics.

The Teton – Wind River domain: a 2.68–2.67 Ga active margin in the western Wyoming Province

2006 ◽  
Vol 43 (10) ◽  
pp. 1489-1510 ◽  
Author(s):  
B Ronald Frost ◽  
Carol D Frost ◽  
Mary Cornia ◽  
Kevin R Chamberlain ◽  
Robert Kirkwood
Keyword(s):  
Plate Tectonics ◽  
Accretionary Prism ◽  
Granulite Facies ◽  
Isotopic Data ◽  
Active Margin ◽  
Magmatic Arc ◽  
Wind River Range ◽  
Teton Range ◽  
Wyoming Province ◽  
Back Arc

The Archean rocks in western Wyoming, including the Teton Range, the northern Wind River Range, and the western Owl Creek Mountains, preserve a record of a 2.68–2.67 Ga orogenic belt that has many of the hallmarks of modern plate tectonics. A 2683 Ma tholeiitic dike swarm is undeformed and unmetamorphosed in the western Owl Creek Mountains. In the Wind River Range, these dikes have been deformed and metamorphosed during thrusting along the west- to southwest-directed Mount Helen structural belt, which was active at the time that the 2.67 Ga Bridger batholith was emplaced. In the northern Teton Range, the Moose Basin gneiss, which contains relict granulite-facies assemblages, appears to have been thrust upon the amphibolite-grade layered gneiss. The syntectonic Webb Canyon orthogneiss was intruded into the thrust at or before 2673 Ma. We interpret these relations, along with isotopic data indicating that the layered gneiss in the Teton Range consists of juvenile components, to indicate that the western Wyoming Province was the site of active margin tectonics at 2.68–2.67 Ga. This involved a magmatic arc in the present Wind River Range and back-arc spreading in the Owl Creek Mountains. The immature, juvenile layered gneiss in the Teton Range probably represents an accretionary prism or fore-arc basin onto which high-pressure rocks containing a mature sedimentary sequence were thrust at 2.67 Ga. Although it may be questioned as to when modern-style plate tectonics began in other cratons, it was certainly operating in the Wyoming Province by 2.67 Ga.

Structure, Metamorphism, and Plutonism in the South-Central Klamath Mountains, California

1965 ◽  
Vol 76 (8) ◽  
pp. 933 ◽  
Author(s):  
GREGORY A. DAVIS ◽  
M. J. HOLDAWAY ◽  
PETER W. LIPMAN ◽  
W. D. ROMEY
Keyword(s):  
Klamath Mountains ◽  
The South ◽  
South Central

scholarly journals Precambrian Geological Evolution of the Teton Range, Western Wyoming

1999 ◽  
Vol 23 ◽  
pp. 85-87
Author(s):  
Kevin Chamberlain ◽  
B. Frost ◽  
Carol Frost
Keyword(s):  
National Park ◽  
Plate Tectonics ◽  
Crustal Growth ◽  
Ongoing Research ◽  
Grand Teton National Park ◽  
Basement Rocks ◽  
First Case ◽  
Peraluminous Granites ◽  
Teton Range ◽  
Wyoming Province

The crystalline rocks that form the core of the Teton Range are part of the Wyoming Province, which is one of the oldest portions of North America. Study of the basement of the Tetons, coupled with the results of ongoing research in similar-aged rocks exposed elsewhere in Wyoming, will provide information on how the crust evolved in the early Earth in general and in the Wyoming province in particular. In 1999 the project involved two weeks of fieldwork in Grand Teton National Park and regions to the east, including the Gros Ventre Range, deep canyons of the Buffalo Fork River near Togwotee Pass, and outcrops of basement near Dubois, Wyoming. The main goals of the fieldwork were to complete the sampling of key units in Grand Teton National Park, and to determine whether or not the next nearest outcrops of basement (Gros Ventre, Togwotee Pass and Dubois regions) share the early geologic history preserved in the rocks of Teton National Park. This field work involved four faculty members from UW and a graduate student, who is doing the study as part of her MS thesis. Several months of laboratory analysis at UW have characterized the rocks through thin section, stained slabs, and whole rock geochemical and Nd, Sr, and Ph isotopic methods and produced preliminary U-Pb dates. The principal results from this year 's efforts are that the Teton basement rocks consist of large proportions of juvenile crust, the majority of the rocks formed over a relatively narrow time span from ~2.74 to 2.68 Ga, they were deformed at about 2.67 Ga, and that rocks exposed in the Buffalo Fork River to the east are shallow level equivalents to the deep rocks exposed in the Tetons. Based on these observations and measurements, we hypothesize that the basement rocks of the Tetons formed in an off­shore, island arc setting between 2.74-2.68 Ga, and they were accreted to the Wyoming province at about 2.67 Ga. Post-tectonic intrusion of distinctive peraluminous granites in both the Teton's (Mt. Owens quartz monzonite) and elsewhere in the Wyoming province at 2.55 Ga strengthens our interpretation of a shared history after 2.67 Ga. If this model for the basement rocks in the Teton's holds up, it will be the first case of crustal growth by lateral accretion for the Archean Wyoming province, and one of the earliest examples of plate tectonics style crustal growth documented from anywhere in the world. Plate tectonic growth has dominated the Earth 's evolution from ~2.5 Ga to the present, but it is unclear whether or not analogous processes operated before 2.5 Ga.

The Wyoming Province: a distinctive Archean craton in Laurentian North America

2006 ◽  
Vol 43 (10) ◽  
pp. 1391-1397 ◽  
Author(s):  
P A Mueller ◽  
C D Frost
Keyword(s):  
Detrital Zircon ◽  
Isotopic Signature ◽  
Crustal Growth ◽  
Continental Arc ◽  
Accreted Terranes ◽  
Wyoming Province ◽  
Detrital Zircon Ages ◽  
Terrane Accretion ◽  
Mafic Lower Crust ◽  
Continental Arc Magmatism

The Wyoming Province is a distinctive Archean craton in the northwestern United States that can be subdivided into three subprovinces, namely, from oldest to youngest, the Montana metasedimentary province, the Beartooth–Bighorn magmatic zone, and the Southern accreted terranes. Archean rocks of the Montana metasedimentary province and the Beartooth–Bighorn magmatic zone are characterized by (1) their antiquity (rock ages to 3.5 Ga, detrital zircon ages up to 4.0 Ga, and Nd model ages exceeding 4.0 Ga); (2) a distinctly enriched 207Pb/204Pb isotopic signature, which suggests that this part of the province was not produced by the amalgamation of exotic terranes; and (3) a distinctively thick (15–20 km), mafic lower crust. The Montana metasedimentary province and Beartooth–Bighorn magmatic zone were cratonized by about 3.0–2.8 Ga. Crustal growth occurred via continental-arc magmatism and terrane accretion in the Southern accreted terranes along the southern margin of the province at 2.68–2.50 Ga. By the end of the Archean, the three subprovinces were joined as part of what is now the Wyoming Province. Subsequent to amalgamation of the Wyoming crust to Laurentia at ca. 1.8–1.9 Ga, Paleoproterozoic crust (1.7–2.4 Ga) was juxtaposed along the southern and western boundaries of the province. Subsequent tectonism and magmatism in the Wyoming region are concentrated in the areas underlain by these Proterozoic mobile belts.

Tectonic histories of the Paleo- to Mesoarchean Sacawee block and Neoarchean Oregon Trail structural belt of the south-central Wyoming Province

2006 ◽  
Vol 43 (10) ◽  
pp. 1445-1466 ◽  
Author(s):  
Rashmi LB Grace ◽  
Kevin R Chamberlain ◽  
B Ronald Frost ◽  
Carol D Frost
Keyword(s):  
Plate Tectonics ◽  
High Strain ◽  
Shear Zones ◽  
Magmatic Zircon ◽  
Lake Area ◽  
Oregon Trail ◽  
South Central ◽  
Wyoming Province ◽  
Narrow Belt ◽  
East West

The Sacawee block is a narrow belt of Paleo- to Mesoarchean crust that extends for ~70 km across the northern Granite Mountains. It is composed of the ~3.3 Ga Sacawee orthogneiss, additional calc-alkalic and tonalitic orthogneisses, and the ~2.86 Ga Barlow Gap Group. The Sacawee block basement is characterized by negative εNd values and Paleoarchean Nd crustal residence model ages. A broad east–west-trending zone of Neoarchean high strain, which is part of the Oregon Trail structural belt, transects the Sacawee block and was studied at two locations, the Beulah Belle Lake area and West Sage Hen Rocks. U–Pb analyses of magmatic zircon from a sheared amphibolite within the high-strain zone of the Beulah Belle Lake area constrain the age of the Neoarchean deformation to be later than 2688 ± 5 Ma. At West Sage Hen Rocks, metamorphic zircons in a sheared amphibolite provide a direct date on the shear zone of 2649 ± 2.8 Ma. These data, combined with similar ages of deformation from two other shear zones, are interpreted to suggest that the Neoarchean Oregon Trail structural belt is a pervasive feature of the Sacawee block and may represent a deformation front related to accretion. Multiple east–west-trending shear zones within the Sacawee block are evidence for tectonic modification of the crust between ~2.65 and 2.63 Ga and horizontal convergence analogous to modern plate tectonics processes. The Sacawee block is either a rare exposure of ancient basement typical of that which originally underlay much of the Wyoming Province or it is an exotic block that was accreted to the core of the Wyoming Province in Neoarchean time.

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