Time scale for the development of thickened crust in the Cretaceous North Cascades magmatic arc, Washington, and relationship to Cretaceous flare-up magmatism

Shea, Erin K.; Miller, Jonathan S.; Miller, Robert B.; Chan, Christine F.; Kent, Adam J.R.; Hanchar, John M.; Dustin, Kelly; Elkins, Scott

doi:10.1130/l1001.1

Cited by 2 publications

(1 citation statement)

References 77 publications

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“…Periodic crustal thickening in the southern Coast Mountains batholith could result from relamination of subducted buoyant material (Hacker et al, 2011), shortening and imbrication of the forearc (Pearson et al, 2017;Sauer et al, 2017), or magmatism and intra-arc shortening, as documented in several Cordilleran arc systems (e.g. Umhoefer and Miller, 1996;Cao and Paterson, 2016;Shea et al, 2018). As previously discussed, it likely does not result from underthrusting of old, supracrustal materials from the retroarc.…”

Section: Drivers Of Flare-ups In the Southern Coast Mountains Batholithmentioning

confidence: 91%

Mantle control on magmatic flare-ups in the southern Coast Mountains batholith, British Columbia

et al. 2021

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The southern Coast Mountain batholith was episodically active from Jurassic to Eocene time and experienced four distinct high magmatic flux events during that period. Similar episodicity has been recognized in arcs worldwide, yet the mechanism(s) driving such punctuated magmatic behavior are debated. This study uses zircon Hf and O isotopes, with whole-rock and mineral geochemistry, to track spatiotemporal changes in southern Coast Mountains batholith melt sources and to evaluate models of flare-up behavior and crust formation in Cordilleran arc systems. Zircon Hf isotope analysis yielded consistently primitive values, with all zircon grains recording initial εHf between +6 and +16. The majority (97%) of zircons analyzed yielded δ18O values between 4.2‰ and 6.5‰, and only five grains recorded values of up to 8.3‰. These isotopic results are interpreted to reflect magmatism dominated by mantle melting during all time periods and across all areas of the southern batholith, which argues against the periodic input of more melt-fertile crustal materials as the driver of episodic arc magmatism. They also indicate that limited crustal recycling is needed to produce the large volumes of continental crust generated in the batholith. Although the isotopic character of intrusions is relatively invariant through time, magmas emplaced during flare-ups record higher Sr/Y and La/Yb(N) and lower zircon Ti and Yb concentrations, which is consistent with melting in thickened crust with garnet present as a fractionating phase. Flare-ups are also temporally associated with periods when the southern Coast Mountains batholith both widens and advances inboard. We suggest that the landward shift of the arc into more fertile lithospheric mantle domains triggers voluminous magmatism and is accompanied by magmatic and/or tectonic thickening. Overall, these results demonstrate that the magmatic growth of Cordilleran arcs can be spatially and temporally complex without requiring variability in the contributions of crust and/or mantle to the batholith.

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Section: Drivers Of Flare-ups In the Southern Coast Mountains Batholithmentioning

confidence: 91%

Mantle control on magmatic flare-ups in the southern Coast Mountains batholith, British Columbia

et al. 2021

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Stratigraphy, age, and provenance of the Eocene Chumstick basin, Washington Cascades; implications for paleogeography, regional tectonics, and development of strike-slip basins

et al. 2021

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Strike-slip faults form in a wide variety of tectonic settings and are a first-order control on the geometry and sediment accumulation patterns in adjacent sedimentary basins. Although the structural and depositional architecture of strike-slip basins is well documented, few studies of strike-slip basins have integrated depositional age, lithofacies, and provenance control within this context. The Chumstick basin formed in central Washington during a regional phase of dextral, strike-slip faulting and episodic magmatism associated with Paleogene ridge-trench interaction along the North America margin. The basin is bounded and subdivided by major strike-slip faults that were active during deposition of the intra-basinal, non-marine Chumstick Formation. We build on the existing stratigraphy and present new, detailed lithofacies mapping, conglomerate clast counts (N = 16; n = 1429), and sandstone detrital zircon analyses (N = 16; n = 1360) from the Chumstick Formation to document changes in sediment provenance, routing, and deposition. These data allow us to reconstruct regional Eocene paleo-drainage systems of Washington and Oregon and suggest that drainage within the Chumstick basin fed a regional river system that flowed to a forearc or marginal basin on the newly accreted Siletzia terrane. More generally, excellent age control from five interbedded tuffs and high sediment accumulation rates allow us to track the evolving sedimentary system over the Formation’s ca. 4−5 m.y. depositional history. This is the first time lithofacies and provenance variations can be constrained at high temporal resolution (0.5−1.5 m.y. scale) for an ancient strike-slip basin and permits a detailed reconstruction of sediment routing pathways and depositional environments. As a result, we can assess how varying sediment supply and accommodation space affects the depositional architecture during strike-slip basin evolution.

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Time scale for the development of thickened crust in the Cretaceous North Cascades magmatic arc, Washington, and relationship to Cretaceous flare-up magmatism

Cited by 2 publications

References 77 publications

Mantle control on magmatic flare-ups in the southern Coast Mountains batholith, British Columbia

Mantle control on magmatic flare-ups in the southern Coast Mountains batholith, British Columbia

Stratigraphy, age, and provenance of the Eocene Chumstick basin, Washington Cascades; implications for paleogeography, regional tectonics, and development of strike-slip basins

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