U-Pb geochronology and geochemistry of intrusive rocks from the Cougar Creek Complex, Wallowa arc terrane, Blue Mountains Province, Oregon-Idaho

Kurz, Gene A.; Schmitz, Mark D.; Northrup, C.J.M.; Vallier, T.L.

doi:10.1130/b30452.1

Cited by 26 publications

(50 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A ~162 Ma: Subduction-related, low-Sr/Y magmatism and hornblende metagabbros of the Wallowa island arc (Taubeneck 1957(Taubeneck , 1995. Metagabbros are Triassic (241-225 Ma: Walker, 1995;Schwartz et al, 2010) and similar to rocks reported from other areas of the Wallowa terrane (Kurz et al, 2012). Pervasive, regional, greenschist facies metamorphism affected both Elkhorn Ridge Argillite and metaigneous units prior to batholith emplacement (Ferns and Brooks, 1995;Schwartz et al, 2010).…”

Section: Nasupporting

confidence: 65%

Time scales and processes of Cordilleran batholith construction and high-Sr/Y magmatic pulses: Evidence from the Bald Mountain batholith, northeastern Oregon

et al. 2014

View full text Add to dashboard Cite

Cordilleran granitic batholiths (sensu lato) preserve information about time scales and processes of upper crustal magmatic arc construction during Mesozoic subduction and mountain building. The Bald Mountain batholith in northeastern Oregon (USA) is a classic example of a composite, incrementally constructed batholith that formed during terrane amalgamation outboard of the western U.S. Cordillera. Whole-rock geochemistry and zircon trace element, U-Pb, Lu-Hf, and O isotopic data reveal that batholith construction occurred over ~15 Ma, commencing with the syncollisional emplacement of small, low-Sr/Y (<40) norite-granite plutons from 157 to 155 Ma. The next phase of magmatism was postcollisional and dominated by high-Sr/Y (>40) tonalite-granodiorite mag matism that produced the main mass of the batholith, including the granodiorite of Anthony Lake (147 Ma) and the tonalite of Bald Mountain (145-141 Ma). Zircons from the norite-granite suite display a narrow range in initial εHf of 7.2-7.7 and elevated δ 18 O (Zrn) ranging from 8.2‰ to 10.0‰ (excluding one outlier). Zircons from the later granodiorite-tonalite suite show a similar range of initial εHf values (6.3-8.9) and δ 18 O (7.1‰-10.0‰), indicating a similar history of interaction with evolved crustal material. Modeling of whole-rock and zircon geochemistry indicates that both the low-and high-Sr/Y magmas composing the main phase of the batholith were generated by dehydration-partial melting of mafi c arc crust (e.g., amphibolite), leaving behind a plagioclase-poor restite, which was garnet granulite in the case of the high-Sr/Y magmas. Final magma compositions in both suites were affected by assimilation of supracrustal material either at depth or during ascent. We suggest that high-Sr/Y magmas in the Bald Mountain batholith were generated by partial melting of thickened arc crust ~10 m.y. after arc-arc collision began at 159-154 Ma. Heat to drive lower crustal melting was conveyed by an increase in mantle power input as a result of renewed subduction-related magmatism. Mixing and homogenization in the lower crust involving mantle-derived basalts and crustally derived partial melts can account for the geochemical variation we observe in tonalites and granodiorites in the Bald Mountain batholith.

show abstract

Section: Nasupporting

confidence: 65%

Time scales and processes of Cordilleran batholith construction and high-Sr/Y magmatic pulses: Evidence from the Bald Mountain batholith, northeastern Oregon

et al. 2014

View full text Add to dashboard Cite

show abstract

“…4; Table 1), although 479 and 1451 Ma ages were also identified. Early Mesozoic ages are unknown from this immediate portion of autochthonous western Laurentia but are common in the Wallowa terrane of northeast Oregon (e.g., Schwartz et al 2010Schwartz et al , 2011Kurz et al 2011). Early Ordovician ages (ca.…”

Section: Discussion and Tectonic Implicationsmentioning

confidence: 99%

Age and structure of the Crevice pluton: overlapping orogens in west-central Idaho?

et al. 2012

View full text Add to dashboard Cite

New U-Pb zircon geochronology from the Riggins region of west-central Idaho refines the timing of contractional deformation across the Salmon River suture zone (SRSZ), a broad north-to northeast-striking belt (>25 km wide) of high strain recording Jura-Cretaceous island-arc-continent collision. Laser ablation -inductively coupled plasma -mass spectrometry (LA-ICP-MS) yields mid-Cretaceous crystallization ages on formerly undated plutonic rocks sampled from the Salmon River canyon. In the Crevice pluton (∼105 Ma), the development of steep to moderate northerly striking gneissic foliation (S1) was followed by tops-to-the-west slip on shallow mylonitic shear zones (S2) and brittle overprinting via systematic joints (Jn) of regional extent. Together, these structures form the pluton's internal architecture. Subvertical gneissic foliation in the adjacent Looking Glass pluton (∼92 Ma) indicates ductile deformation was ongoing in the Late Cretaceous. Prior to this investigation, penetrative fabrics in local arc volcanogenic, plutonic, and continental rocks have been unequivocally linked to post-collisional dextral transpression on the narrow (<10 km wide) western Idaho shear zone (WISZ). As an alternative to this model which requires spatially overlapping but temporally distinct orogenic belts (WISZ-SRSZ), we consider a protracted history whereby regional synmetamorphic structures accumulated over a pre-118 Ma to post-92 Ma interval without an overprinting orogen-scale ductile shear zone. In our view, a progressive deformation history more accurately accounts for the time-transgressive nature and structural continuity of fabrics observed across the arc-continent transition. This tectonic history proposed for western Idaho may be analogous to other long-lived accretionary margins in the North American Cordillera (e.g., Omineca Belt of southeastern British Columbia).Résumé : Une nouvelle géochronologie par U-Pb sur zircon pour la région Riggins du centre-ouest de l'Idaho précise le moment de la déformation par contraction à travers la zone de suture de Salmon River (SRSZ), une large ceinture (>25 km) de direction nord à nord-est de grandes contraintes enregistrant des collisions au Jurassique-Crétacé entre des îles d'arcs et le continent. La spectrométrie de masse à source plasma à couplage inductif avec ablation laser (LA-ICP-MS) a donné des âges de cristallisation au Crétacé moyen à partir de roches plutoniques prélevées dans le canyon de la rivière Salmon non datées antérieurement. Dans le pluton Crevice (∼105 Ma), le développement de foliation gneissique (S1) à direction nord et à pendage fort à modéré a été suivi par un décrochement « sommet vers l'ouest » sur des zones de cisaillement mylonitiques à faible profondeur (S2) et une surimpression cassante par des joints (Jn) systématiques d'étendue régionale. Ensemble, ces structures forment l'architecture interne du pluton. Une foliation subverticale des gneiss dans le pluton adjacent de Looking Glass (∼92 Ma) indique qu'une déformation ductile était en cours au Crétac...

show abstract

“…Exposed basement rocks from both of these arc terranes offer criti cal information pertaining to their magmatic his tories and paleogeography. Kurz et al (2012) provided a detailed geologic framework of the www.gsapubs.org | Volume 9 | Number 2 | LITHOSPHERE magmatic and deformational history of the Cou gar Creek complex (CCC), one of several base ment complexes that manifest the midcrustal levels of the WA (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Isotopic compositions of intrusive rocks from the Wallowa and Olds Ferry arc terranes of northeastern Oregon and western Idaho: Implications for Cordilleran evolution, lithospheric structure, and Miocene magmatism

et al. 2016

View full text Add to dashboard Cite

Late Paleozoic and Mesozoic intrusive rocks from the Wallowa and Olds Ferry arc terranes of the Blue Mountains Province, Oregon-Idaho, provide constraints on the paleogeographic and tectonic setting of magmatism preserved in both arcs. Sr, Nd, and Pb isotopic data show that the Wallowa terrane represents an isotopically depleted, juvenile intra-oceanic island arc. By contrast, isotopic data for intrusive rocks of the Olds Ferry arc are more isotopically enriched, and thereby establish a clear distinction between the two arcs. This distinction strengthens paleogeographic interpretation of the Olds Ferry terrane as a fringing continental arc, and it provides a basis for correlation to other inboard Cordilleran arc terranes including Quesnellia and Stikinia. The Wallowa terrane is by contrast more similar geologically and isotopically to the outboard Insular terranes. These isotopic data also constrain interpretations of regional lithospheric architecture. Isotopic profiles generated orthogonal to the inferred Wallowa-Olds Ferry terrane boundary and the western Idaho shear zone show abrupt increases in initial 87 Sr/ 86 Sr that mark the transitions between three geochemically distinct lithospheric columns. West-to-east spatial variability in the isotopic compositions of Neogene volcanic rocks is explained by the partial melting of these three geochemically distinct mantle reservoirs coupled to their respective crustal columns since the early Mesozoic, rather than alternative models of lithosphere-scale décollement offset during Sevier shortening. The inherited arcrelated mantle of the Olds Ferry arc may also have played a primary role in the petrogenesis of distinctive Neogene low-K, high-alumina olivine tholeiites of the High Lava Plains.

show abstract

U-Pb geochronology and geochemistry of intrusive rocks from the Cougar Creek Complex, Wallowa arc terrane, Blue Mountains Province, Oregon-Idaho

Cited by 26 publications

References 69 publications

Time scales and processes of Cordilleran batholith construction and high-Sr/Y magmatic pulses: Evidence from the Bald Mountain batholith, northeastern Oregon

Time scales and processes of Cordilleran batholith construction and high-Sr/Y magmatic pulses: Evidence from the Bald Mountain batholith, northeastern Oregon

Age and structure of the Crevice pluton: overlapping orogens in west-central Idaho?

Isotopic compositions of intrusive rocks from the Wallowa and Olds Ferry arc terranes of northeastern Oregon and western Idaho: Implications for Cordilleran evolution, lithospheric structure, and Miocene magmatism

Contact Info

Product

Resources

About