Early Archean to Mesoproterozoic evolution of the Wyoming Province: Archean origins to modern lithospheric architecture

2003 ◽  
Vol 40 (10) ◽  
pp. 1357-1374 ◽  
Author(s):  
Kevin R Chamberlain ◽  
Carol D Frost ◽  
B Ronald Frost
Keyword(s):  
Black Hills ◽  
Arc Magmatism ◽  
Crustal Growth ◽  
Crustal Layer ◽  
Oregon Trail ◽  
Sierra Madre ◽  
Cumulative Processes ◽  
Wyoming Province ◽  
Lower Crustal ◽  
East West

Local preservation of 3.6–3.0 Ga gneisses and widespread isotopic evidence for crust of this age incorporated into younger plutons indicates that the Wyoming Province was a [Formula: see text] 100 000 km2 middle Archean craton, which was modified by late Archean magmatism and tectonism and Proterozoic extension and rifting. On the basis of differences in late Archean histories, the Wyoming Province is subdivided into five subprovinces: three in the Archean core, (1) the Montana metasedimentary province, (2) the Bighorn subprovince, and (3) the Sweetwater subprovince, and two Archean terrains that may be allochthonous to the 3.0 Ga craton, (4) the Sierra Madre – Medicine Bow block, and (5) the Black Hills – Hartville block. A thick, fast lower crustal layer, imaged by Deep Probe, corresponds geographically with the Bighorn subprovince and may be an underplate associated with ca. 2.70 Ga mafic magmatism. The Sweetwater subprovince is characterized by an east–west tectonic grain that was established by three or more temporally related, late Archean, pulses of basin development, shortening, and arc magmatism. This tectonic grain, including the 2.62 Ga Oregon Trail structure, controlled the locations and orientations of Proterozoic rifting and Laramide uplifts. The present-day lithospheric architecture of the Wyoming Province is the result of cumulative processes of crustal growth and tectonic modification; lithospheric contrasts have apparently persisted for billions of years. If there has been any net crustal growth of the Wyoming Province since 3.0 Ga, it has involved a combination of mafic underplating and arc magmatism.

In suspect terrane? Provenance of the late Archean Phantom Lake metamorphic suite, Sierra Madre, Wyoming

2006 ◽  
Vol 43 (10) ◽  
pp. 1557-1577 ◽  
Author(s):  
A Kate Souders ◽  
Carol D Frost
Keyword(s):  
Crustal Growth ◽  
Important Process ◽  
Light Rare Earth ◽  
Nd Isotope ◽  
Eu Anomaly ◽  
Sierra Madre ◽  
Wyoming Province ◽  
Metaigneous Rocks ◽  
Ree Patterns ◽  
Rattlesnake Hills

The 2.68 Ga Phantom Lake metamorphic suite of the Sierra Madre is a volcanogenic, volcaniclastic, and siliciclastic sequence that may have been deposited on or near the margin of the Wyoming Province or, alternatively, it may represent part of an exotic block accreted onto the southern margin of the Wyoming Province. The metamorphosed supracrustal rocks of the Phantom Lake metamorphic suite, along with quartzofeldspathic gneisses and granitoids of similar age, have light rare-earth element (LREE) – enriched REE patterns with little to no Eu-anomaly. These patterns are comparable to those of modern oceanic arc rocks and sediments. Both supracrustal and metaigneous rocks have radiogenic initial εNd from +4.5 to –2.5 and Nd crustal residence ages between 2.7 and 3.0 Ga. It is proposed that these juvenile rocks were part of an intra-oceanic arc system formed beyond the influence of detritus from the Wyoming Province and subsequently were accreted onto the southern Wyoming Province following intrusion of granitic gneisses in the Sierra Madre at ca. 2.64 Ga. The younger 2.43 Ga Baggot Rocks granite has less radiogenic εNd of –3.9 suggesting that the rocks of the Sierra Madre had accreted to the Wyoming Province by 2.43 Ga. The supracrustal sequences at South Pass, Bradley Peak, and the Rattlesnake Hills have similar, radiogenic initial Nd isotope compositions. Together with the Phantom Lake metamorphic suite, they represent juvenile additions to existing continental crust and provide evidence that lateral accretion of oceanic terranes was an important process of late Archean crustal growth in the Wyoming Province.

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.

Overview of regional geophysical studies in Manitoba and northwestern Ontario

1982 ◽  
Vol 19 (11) ◽  
pp. 2049-2059 ◽  
Author(s):  
D. H. Hall ◽  
W. C. Brisbin
Keyword(s):  
Greenstone Belt ◽  
Seismic Velocities ◽  
Crustal Layer ◽  
Northwestern Ontario ◽  
Reflection And Refraction ◽  
Gravity And Magnetic ◽  
Winnipeg River ◽  
Lower Crustal ◽  
Gravity And Magnetic Anomaly

This paper presents an overview of six geophysical projects (seismic reflection and refraction, gravity and magnetic anomaly interpretation, specific gravity and magnetic property measurements) carried out in an area in Manitoba and northwestern Ontario bounded by 93 and 96°W longitude, and 49 and 51°N latitude.The purpose of the surveys was to define crustal structure in the Kenora–Wabigoon greenstone belt, the Winnipeg River batholithic belt, the Ear Falls – Manigotagan gneiss belt, and the Uchi greenstone belt. The following conclusions emerge.In all of the belts, a major discontinuity divides the crust into the commonly found upper and lower crustal sections. At the top of the lower crust, a seismically distinct layer (the mid-crustal layer) occurs. Seismic velocities in this layer suggest either intermediate to basic igneous rocks or metamorphic rocks of the amphibolite facies.Crustal geophysical characteristics vary sufficiently among the four belts to justify the classification of all four as distinct subprovinces of the Superior Province.Cet article présente une vue générale sur six projets de géophysique (réflexion et réfraction sismique, interprétation d'anomalies de gravité et magnétiques, déterminations de densité et de propriétés magnétiques) réalisés dans une région du Manitoba et du nord-ouest de l'Ontario encadrée par les longitudes 93 et 96°O et les latitudes 49 et 51°N.

Crustal velocity structure from SAREX, the Southern Alberta Refraction Experiment

2002 ◽  
Vol 39 (3) ◽  
pp. 351-373 ◽  
Author(s):  
Ron M Clowes ◽  
Michael JA Burianyk ◽  
Andrew R Gorman ◽  
Ernest R Kanasewich
Keyword(s):  
Velocity Structure ◽  
Data Interpretation ◽  
Crustal Thickening ◽  
Tectonic Zone ◽  
Crustal Layer ◽  
Crustal Velocity ◽  
Crustal Velocity Structure ◽  
Southern Alberta ◽  
Magmatic Underplating ◽  
Lower Crustal

Lithoprobe's Southern Alberta Refraction Experiment, SAREX, extends 800 km from east-central Alberta to central Montana. It was designed to investigate crustal velocity structure of the Archean domains underlying the Western Canada Sedimentary Basin. From north to south, SAREX crosses the Loverna domain of the Hearne Province, the Vulcan structure, the Medicine Hat block (previously considered part of the Hearne Province), the Great Falls tectonic zone, and the northern Wyoming Province. Ten shot points along the profile in Canada were recorded on 521 seismographs deployed at 1 km intervals. To extend the line, an additional 140 seismographs were deployed at intervals of 1.25–2.50 km in Montana. Data interpretation used an iterative application of damped least-squares inversion of traveltime picks and forward modeling. Results show different velocity structures for the major blocks (Loverna, Medicine Hat, and Wyoming), indicating that each is distinct. Wavy undulations in the velocity structure of the Loverna block may be associated with internal crustal deformation. The most prominent feature of the model is a thick (10–25 km) lower crustal layer with high velocities (7.5–7.9 km/s) underlying the Medicine Hat and Wyoming blocks. Based on data from lower crustal xenoliths in the region, this layer is interpreted to be the result of Paleoproterozoic magmatic underplating. Crustal thickness varies from 40 km in the north to almost 60 km in the south, where the high-velocity layer is thickest. Uppermost mantle velocities range from 8.05 to 8.2 km/s, with the higher values below the thicker crust. Results from SAREX and other recent studies are synthesized to develop a schematic representation of Archean to Paleoproterozoic tectonic development for the region encompassing the profile. Tectonic processes associated with this development include collisions of continental blocks, subduction, crustal thickening, and magmatic underplating.

scholarly journals Interplay of Cretaceous transpressional deformation and continental arc magmatism in a long-lived crustal boundary, central Fiordland, New Zealand

Geosphere ◽  
2020 ◽  
Vol 16 (5) ◽  
pp. 1225-1248
Author(s):  
Hannah J. Blatchford ◽  
Keith A. Klepeis ◽  
Joshua J. Schwartz ◽  
Richard Jongens ◽  
Rose E. Turnbull ◽  
...  
Keyword(s):  
New Zealand ◽  
Thermal Structure ◽  
Shear Zones ◽  
Arc Magmatism ◽  
Magmatic Arc ◽  
Continental Arcs ◽  
Metasedimentary Rocks ◽  
Spatio Temporal ◽  
Continental Magmatic Arc ◽  
Lower Crustal

Abstract Recovering the time-evolving relationship between arc magmatism and deformation, and the influence of anisotropies (inherited foliations, crustal-scale features, and thermal gradients), is critical for interpreting the location, timing, and geometry of transpressional structures in continental arcs. We investigated these themes of magma-deformation interactions and preexisting anisotropies within a middle- and lower-crustal section of Cretaceous arc crust coinciding with a Paleozoic boundary in central Fiordland, New Zealand. We present new structural mapping and results of Zr-in-titanite thermometry and U-Pb zircon and titanite geochronology from an Early Cretaceous batholith and its host rock. The data reveal how the expression of transpression in the middle and lower crust of a continental magmatic arc evolved during emplacement and crystallization of the ∼2300 km2 lower-crustal Western Fiordland Orthogneiss (WFO) batholith. Two structures within Fiordland’s architecture of transpressional shear zones are identified. The gently dipping Misty shear zone records syn-magmatic oblique-sinistral thrust motion between ca. 123 and ca. 118 Ma, along the lower-crustal WFO Misty Pluton margin. The subhorizontal South Adams Burn thrust records mid-crustal arc-normal shortening between ca. 114 and ca. 111 Ma. Both structures are localized within and reactivate a recently described >10 km-wide Paleozoic crustal boundary, and show that deformation migrated upwards between ca. 118 and ca. 114 Ma. WFO emplacement and crystallization (mainly 118–115 Ma) coincided with elevated (>750 °C) middle- and lower-crustal Zr-in-titanite temperatures and the onset of mid-crustal cooling at 5.9 ± 2.0 °C Ma−1 between ca. 118 and ca. 95 Ma. We suggest that reduced strength contrasts across lower-crustal pluton margins during crystallization caused deformation to migrate upwards into thermally weakened rocks of the mid-crust. The migration was accompanied by partitioning of deformation into domains of arc-normal shortening in Paleozoic metasedimentary rocks and domains that combined shortening and strike-slip deformation in crustal-scale subvertical, transpressional shear zones previously documented in Fiordland. U-Pb titanite dates indicate Carboniferous–Cretaceous (re)crystallization, consistent with reactivation of the inherited boundary. Our results show that spatio-temporal patterns of transpression are influenced by magma emplacement and crystallization and by the thermal structure of a reactivated boundary.

scholarly journals The fate of fluids released from subducting slab in northern Cascadia

2011 ◽  
Vol 3 (2) ◽  
pp. 943-962 ◽  
Author(s):  
K. Ramachandran ◽  
R. D. Hyndman
Keyword(s):  
Poisson’S Ratio ◽  
Subduction Zones ◽  
Poisson's Ratio ◽  
Crustal Layer ◽  
Collision Tectonics ◽  
Significant Addition ◽  
Increasing Temperature ◽  
Lower Crustal ◽  
Forearc Region ◽  
Forearc Mantle

Abstract. Large amounts of water carried down in subduction zones are driven upward into the overlying forearc upper mantle and crust as increasing temperature and pressure dehydrate the subducting crust. Through seismic tomography velocities we show that, (a) the overlying forearc mantle in Northern Cascadia is hydrated to serpentinite, and (b) the low Poisson's ratio at the base of the forearc lower crust that may represent silica deposited from the rising fluids. From the velocities observed in the forearc mantle, the volume of serpentinite estimated is ~30 %. This mechanically weak hydrated forearc region has important consequences in limits to great earthquakes and to collision tectonics. An approximately 10 km thick lower crustal layer of low Poisson's ratio (σ = 0.22) in the forearc is estimated to represent a maximum addition of ~14 % by volume of quartz (σ = 0.09). If this quartz is removed from rising silica-saturated fluids over long times it represents a significant addition of silica to the continental crust and an important contributor to its average composition.

Geochemistry and origin of Archean granites from the Black Hills, South Dakota

1990 ◽  
Vol 27 (1) ◽  
pp. 57-71 ◽  
Author(s):  
D. C. Gosselin ◽  
J. J. Papike ◽  
C. K. Shearer ◽  
Z. E. Peterman ◽  
J. C. Laul
Keyword(s):  
Rare Earth ◽  
South Dakota ◽  
Partial Melting ◽  
Residence Time ◽  
Earth Element ◽  
Black Hills ◽  
Isotopic Data ◽  
Tectonic Environment ◽  
Sedimentary Source ◽  
Wyoming Province

The Little Elk Granite (2549 Ma) and granite at Bear Mountain (BMG) (~2.5 Ga) of the Black Hills formed as a result of a collisional event along the eastern margin of the Wyoming Province during the late Archean. Geochemical modelling and Nd isotopic data indicate that the Little Elk Granite was generated by the partial melting of a slightly enriched (εNd = −1.07 to −3.69) granodioritic source that had a crustal residence time of at least 190 Ma. The medium-grained to pegmatitic, peraluminous, leucocratic BMG was produced by melting a long-lived (>600 Ma), compositionally variable, enriched (εNd = −7.6 to −12.3) crustal source. This produced a volatile-rich, rare-earth-element-poor magma that experienced crystal–melt–volatile fractionation, which resulted in a lithologically complex granite.The production of volatile-rich granites, such as the BMG and the younger Harney Peak Granite (1715 Ma), is a function of the depositional and post-depositional tectonic environment of the sedimentary source rock. These environments control protolith composition and the occurrence of dehydration and melting reactions that are necessary for the generation of these volatile-rich leucocratic granites. These types of granites are commonly related to former continental–continental accretionary boundaries, and therefore their occurrence may be used as signatures of ancient continental suture zones.

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