Correlation among lower to upper crustal components in an island arc: the Jurassic Bonanza arc, Vancouver Island, Canada

DeBari, S. M.; Anderson, Robert; Mortensen, James K.

doi:10.1139/cjes-36-8-1371

Cited by 21 publications

(33 citation statements)

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“…103 Ma. The two older concordant grains give ages typical for the Island Intrusions and Westcoast Crystalline Complex of Wrangellia on Vancouver Island (DeBari et al, 1999), and the younger two concordant grains have interpreted ages common in the southern Coast Plutonic Complex (Friedman and Armstrong, 1995). However, igneous rocks of these ages are known along the length of the Cordillera and are thus not latitudinally signifi cant.…”

Section: Detrital Zircons From the Leech River Schistmentioning

confidence: 99%

Magmatic and tectonic history of the Leech River Complex, Vancouver Island, British Columbia: Evidence for ridge-trench intersection and accretion of the Crescent Terrane

Groome

Thorkelson²,

Friedman³

et al. 2003

Geology of a Transpressional Orogen Developed During Ridge-Trench Interaction Along the North Pacific Margin

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The Leech River Complex, part of the Pacifi c Rim Terrane, is a Cretaceous metasedimentary and metaigneous assemblage on southern Vancouver Island. The Leech River Complex is fault-bounded between the Eocene Metchosin Igneous Complex to the south (part of the Crescent Terrane) and the Paleozoic to Jurassic Wrangel Terrane to the north and provides critical information on the evolution of the central part of the western North American forearc in Cretaceous through Eocene time. Single detrital zircons from the metasedimentary component, known as the Leech River Schist, give U-Pb interpreted ages that range from Precambrian to ca. 103 Ma, indicating a varied source region and a probable Early Cretaceous depositional age. U-Pb geochronology and fi eld investigations indicate at least two magmatic-metamorphic events in the Leech River Complex: one during the Late Cretaceous, and the other during the early Middle Eocene. The peraluminous Jordan River metagranodiorite, a fi ne-grained biotitic stock and related dikes intruded the Leech River Complex at ca. 88 Ma, during the older magmatic event. Metamorphic pressure-temperature conditions of 525-550 °C and 2-3 kbar are recorded in the contact aureole. The later event occurred during emplacement of the Walker Creek intrusions, a suite of peraluminous tonalite, trondjhemite, and granodiorite dikes that intruded the Complex at ca. 51 Ma and produced a similar metamorphic aureole. Both intrusive suites have

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Section: Detrital Zircons From the Leech River Schistmentioning

confidence: 99%

Magmatic and tectonic history of the Leech River Complex, Vancouver Island, British Columbia: Evidence for ridge-trench intersection and accretion of the Crescent Terrane

Groome

Thorkelson²,

Friedman³

et al. 2003

Geology of a Transpressional Orogen Developed During Ridge-Trench Interaction Along the North Pacific Margin

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“…The Wrangellia terrane extends from southern Alaska to Vancouver Island, British Columbia. The southern portion is intruded by the Jurassic Bonanza arc, which some authors have argued represents a southern extension of Talkeetna arc magmatism [Plafker et al, 1989;DeBari et al, 1999], though this relationship is debated. Overlap assemblages suggest that the two terranes formed as a single tectonic block or were juxtaposed prior to accretion onto the continental margin [Plafker et al, 1989;Nokleberg et al, 1994].…”

Section: Geologic Settingmentioning

confidence: 99%

Intermediate to felsic middle crust in the accreted Talkeetna arc, the Alaska Peninsula and Kodiak Island, Alaska: An analogue for low‐velocity middle crust in modern arcs

et al. 2010

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Seismic profiles of several modern arcs have identified thick, low‐velocity midcrustal layers (Vp = 6.0–6.5 km/s) that are interpreted to represent intermediate to felsic plutonic crust. The presence of this silicic crust is surprising given the mafic composition of most primitive mantle melts and could have important implications for the chemical evolution and bulk composition of arcs. However, direct studies of the middle crust are limited by the restricted plutonic exposures in modern arcs. The accreted Talkeetna arc, south central Alaska, exposes a faulted crustal section from residual subarc mantle to subaerial volcanic rocks of a Jurassic intraoceanic arc and is an ideal place to study the intrusive middle crust. Previous research on the arc, which has provided insight into a range of arc processes, has principally focused on western exposures of the arc in the Chugach Mountains. We present new U‐Pb zircon dates, radiogenic isotope data, and whole‐rock geochemical analyses that provide the first high‐precision data on large intermediate to felsic plutonic exposures on Kodiak Island and the Alaska Peninsula. A single chemical abrasion–thermal ionization mass spectrometry analysis from the Afognak pluton yielded an age of 212.87 ± 0.19 Ma, indicating that the plutonic exposures on Kodiak Island represent the earliest preserved record of Talkeetna arc magmatism. Nine new dates from the extensive Jurassic batholith on the Alaska Peninsula range from 183.5 to 164.1 Ma and require a northward shift in the Talkeetna arc magmatic axis following initial emplacement of the Kodiak plutons, paralleling the development of arc magmatism in the Chugach and Talkeetna mountains. Radiogenic isotope data from the Alaska Peninsula and the Kodiak archipelago range from ɛNd(t) = 5.2 to 9.0 and 87Sr/86Srint = 0.703515 to 0.703947 and are similar to age‐corrected data from modern intraoceanic arcs, suggesting that the evolved Alaska Peninsula plutons formed by extensive differentiation of arc basalts with little or no involvement of preexisting crustal material. The whole‐rock geochemical data and calculated seismic velocities suggest that the Alaska Peninsula represents an analogue for the low‐velocity middle crust observed in modern arcs. The continuous temporal record and extensive exposure of intermediate to felsic plutonic rocks in the Talkeetna arc indicate that evolved magmas are generated by repetitive or steady state processes and play a fundamental role in the growth and evolution of intraoceanic arcs.

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“…The authors interpreted these rocks as transformed gabbroic relicts in latemagmatic conditions under high water pressure. Accounts from the Canadian Cordillera Westcoast Crystalline Complex (DeBari et al, 1999;Larocque and Canil, 2010) report a continuous range of rocktypes from mid-crustal ultramafic cumulates to shallower hornblende gabbro and granodiorite. In a recent reappraisal on the appinite problem (based on outcrops resembling those of Fig.…”

Section: Hornblenditementioning

confidence: 99%

“…6a: Pe-Piper et al, 2010), the chemistry of the appinites was shown not to characterize a definite tectonic setting, but rather and only a peculiar magmatic process leading to hydrated mafic rocks. Field evidence of transitional facies between deep-seated mafic cumulates and calc-alkaline, shallower plutons resembling the Cogne diorite, were described in the Western Canadian coastal ranges (DeBari et al, 1999), with a continuous array between hornblende gabbro, hornblendite and hornblende granodiorite.…”

Section: Hornblenditementioning

confidence: 99%

Early Variscan I-type pluton in the pre-Alpine basement of the Western Alps: The ca. 360Ma Cogne diorite (NW-Italy)

Guillot¹,

Bertrand²,

Bussy

et al. 2012

Lithos

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Correlation among lower to upper crustal components in an island arc: the Jurassic Bonanza arc, Vancouver Island, Canada

Cited by 21 publications

References 0 publications

Magmatic and tectonic history of the Leech River Complex, Vancouver Island, British Columbia: Evidence for ridge-trench intersection and accretion of the Crescent Terrane

Magmatic and tectonic history of the Leech River Complex, Vancouver Island, British Columbia: Evidence for ridge-trench intersection and accretion of the Crescent Terrane

Intermediate to felsic middle crust in the accreted Talkeetna arc, the Alaska Peninsula and Kodiak Island, Alaska: An analogue for low‐velocity middle crust in modern arcs

Early Variscan I-type pluton in the pre-Alpine basement of the Western Alps: The ca. 360Ma Cogne diorite (NW-Italy)

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