Lu–Hf systematics of magmatic zircons reveal a Proterozoic crustal boundary under the Cretaceous Pioneer batholith, Montana

Foster, David A.; Mueller, Paul A.; Heatherington, Ann L.; Gifford, Jennifer N.; Kalakay, Thomas J.

doi:10.1016/j.lithos.2012.03.005

Cited by 31 publications

(34 citation statements)

References 75 publications

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“…However, the continuity of the data sets for most samples suggests that the observed 5-10 unit range in ε Hf (T) refl ects real isotopic variation in magmatic zircons. Similar ranges of initial ε Hf have been observed in both Proterozoic and Phanerozoic magmatic zircons (Andersen et al, 2002;Kemp et al, 2007;Shaw and Flood, 2009;Foster et al, 2012).…”

Section: Paleoproterozoic Basement Rockssupporting

confidence: 74%

Crustal growth and tectonic evolution of the Mojave crustal province: Insights from hafnium isotope systematics in zircons

2013

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Section: Paleoproterozoic Basement Rockssupporting

confidence: 74%

Crustal growth and tectonic evolution of the Mojave crustal province: Insights from hafnium isotope systematics in zircons

2013

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“…Thin-skinned thrust faults in the frontal fold-thrust belt locally modified the edges of preexisting foreland basement uplifts Ruppel & Lopez, 1984). The basement rocks that form the Laramide uplifts were structurally elevated along roughly north trending foreland arches in the hanging walls of west and southwest dipping thrust faults and in the hanging walls of northwest striking, northeast dipping, highangle reverse faults of Precambrian ancestry ( Figure 2; DeCelles et al, 1987;Garihan et al, 1983;Schmidt & Hendrix, 1981;Schmidt & O'Neill, 1982;Schmidt et al, , 1993 Harlan, 1998;Lund et al, 2002;Foster et al, 2002Foster et al, , 2012; magmatism continued to the east until ca. 55 Ma (Constenius et al, 2003, and references therein).…”

Section: Geologic Setting Of Southwest Montana Laramide Upliftsmentioning

confidence: 99%

Early Inception of the Laramide Orogeny in Southwestern Montana and Northern Wyoming: Implications for Models of Flat‐Slab Subduction

2019

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Timing and distribution of magmatism, deformation, exhumation, and basin development have been used to reconstruct the history of Laramide flat‐slab subduction under North America during Late Cretaceous‐early Cenozoic time. Existing geodynamic models, however, ignore a large (~40,000‐km2) sector of the Laramide foreland in southwestern Montana. The Montana Laramide ranges consist of Archean basement arches (fault‐propagation folds) that were elevated by thrust and reverse faults. We present new thermochronological and geochronological data from six Laramide ranges in southwestern Montana (the Beartooth, Gravelly, Ruby and Madison Ranges, and the Tobacco Root and Highland Mountains) that show significant cooling and exhumation during the Early to mid‐Cretaceous, much earlier than the record of Laramide exhumation in Wyoming. These data suggest that Laramide‐style deformation‐driven exhumation slightly predates the eastward sweep of magmatism in western Montana, consistent with geodynamic models involving initial strain propagation into North American cratonic rocks due to stresses associated with a northeastward expanding region of flat‐slab subduction. Our results also indicate various degrees of Cenozoic heating and cooling possibly associated with westward rollback of the subducting Farallon slab, followed by Basin‐and‐Range extension.

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“…In addition, this crust is generally not zircon-bearing by nature and will not widely be represented in the global detrital zircon U-Pb age record because of the mafic composition and the relatively high density; emplacement in the lower crust means little will be exhumed and eroded. Older Lu-Hf isotopic model ages in younger zircons will reflect the presence of extensive mafic lower crust, but only if partially melted hundreds of millions of years later without mixing with juvenile or continental components [147][148][149][150][151][152]. Partial melting of the oceanic lower crustal layer some tens of millions of years later will likely not be revealed by detrital zircon Hf isotopic composition because these data will be similar to the signature of juvenile crust.…”

Section: Discussionmentioning

confidence: 99%

Continental Growth and Recycling in Convergent Orogens with Large Turbidite Fans on Oceanic Crust

Foster

Goscombe²

2013

Geosciences

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Convergent plate margins where large turbidite fans with slivers of oceanic basement are accreted to continents represent important sites of continental crustal growth and recycling. Crust accreted in these settings is dominated by an upper layer of recycled crustal and arc detritus (turbidites) underlain by a layer of tectonically imbricated upper oceanic crust and/or thinned continental crust. When oceanic crust is converted to lower continental crust it represents a juvenile addition to the continental growth budget. This two-tiered accreted crust is often the same thickness as average continental crustal and is isostatically balanced near sea level. The Paleozoic Lachlan Orogen of eastern Australia is the archetypical example of a tubidite-dominated accretionary orogeny. The Neoproterozoic-Cambrian Damaran Orogen of SW Africa is similar to the Lachlan Orogen except that it was incorporated into Gondwana via a continent-continent collision. The Mesozoic Rangitatan Orogen of New Zealand illustrates the transition of convergent margin from a Lachlan-type to more typical accretionary wedge type orogen. The spatial and temporal variations in deformation, metamorphism, and magmatism across these orogens illustrate how large volumes of turbidite and their relict oceanic basement eventually become stable continental crust. The timing of deformation and metamorphism recorded in these rocks reflects the crustal thickening phase, whereas post-tectonic magmatism constrains the timing of chemical maturation and cratonization. Cratonization of continental crust is fostered because turbidites represent fertile sources for felsic magmatism. Recognition of similar orogens in the Proterozoic and Archean is important for the evaluation of crustal growth models, particularly for those based on detrital zircon age patterns, because crustal growth by accretion of upper oceanic crust or mafic underplating does not readily result in the addition of voluminous zircon-bearing magmas at the time of accretion. This crust only produces significant zircon when and if it partially melts, which may occur long after accretion

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Lu–Hf systematics of magmatic zircons reveal a Proterozoic crustal boundary under the Cretaceous Pioneer batholith, Montana

Cited by 31 publications

References 75 publications

Crustal growth and tectonic evolution of the Mojave crustal province: Insights from hafnium isotope systematics in zircons

Crustal growth and tectonic evolution of the Mojave crustal province: Insights from hafnium isotope systematics in zircons

Early Inception of the Laramide Orogeny in Southwestern Montana and Northern Wyoming: Implications for Models of Flat‐Slab Subduction

Continental Growth and Recycling in Convergent Orogens with Large Turbidite Fans on Oceanic Crust

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