Formation of a sheeted intrusive complex within the deep-crustal Tenpeak pluton, North Cascades, Washington

Chan, Christine F.; Shea, Erin K.; Kent, Adam J.R.; Miller, Robert B.; Miller, Jonathan S.; Bowring, Samuel A.

doi:10.1130/ges01323.1

Cited by 7 publications

(11 citation statements)

References 77 publications

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“…Geochemical and isotopic work by Dawes (1993), DeBari et al (1998), Matzel et al (2008), Chan et al (2017), and Miller et al (2018) suggests that rocks in the Tenpeak pluton were derived from mixing between mantle-derived mafic magma and crustally derived felsic magma (Miller et al, 2018). Noncumulate rocks of the Tenpeak pluton span a range of compositions from 51 to 66 wt% SiO 2 and 2-8 wt% MgO (Miller et al, 2018).…”

Section: Geology Of the Tenpeak Plutonmentioning

confidence: 99%

“…The ca. 92-89 Ma Tenpeak pluton (Cater, 1982;Miller and Paterson, 1999;Matzel et al, 2006;Chan et al, 2017;Miller et al, 2018) is an irregularly shaped, elongate body that also intrudes the Napeequa unit ( Figs. 1 and 2C).…”

Section: Geology Of the Tenpeak Plutonmentioning

confidence: 99%

“…90.6 Ma), the Interlayered zone (undated), and the Indian Creek tonalite (ca. 89.7 Ma; Miller and Paterson, 1999;Matzel et al, 2006;Shea, 2014;Chan et al, 2017;Miller et al, 2018). Overall, the Tenpeak pluton is dominated by tonalite, but the Mafic complex is a discontinuous heterogeneous zone of mingled and sheeted gabbro, tonalite, and hornblendite (Fig.…”

Section: Geology Of the Tenpeak Plutonmentioning

confidence: 99%

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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

Shea

Miller

et al. 2018

Lithosphere

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Heavy rare earth element (HREE)-depleted trace-element patterns are a relatively common feature of granitoids within mature Cordilleran continental margin arcs (e.g., Sierra Nevada batholith, Coast Mountains batholith, North Cascades, Peninsular Ranges batholith). This depletion is commonly interpreted to indicate the presence of garnet during granitoid melt formation, which requires thick arc crust (>40 km) to achieve the necessary pressure conditions to stabilize garnet in the lower crust. This work focused on understanding the evolution of thickened crust in an ancient continental arc using whole-rock geochemical data, high-precision chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb zircon geochronology, and in situ zircon Hf and O isotopic data from three contemporaneous Cretaceous plutons in the North Cascades of Washington State, USA. New data show that, over time, magmas from three North Cascades plutons became more felsic and more HREE-depleted but lacked a significant change in zircon δ 18 O. The gradual depletion in HREEs through time is interpreted as evidence for a progressively thickening crust in the North Cascades arc that only became thick enough to stabilize garnet between 90 Ma and 87 Ma. This time frame also coincides with the end of a major period of contraction and plutonism in the region, suggesting a link between thick crust and the end of a major magmatic flare-up. The absence of appreciable change in zircon δ 18 O values during this time suggests that thickening may have been the result of crustal shortening within the arc, causing migration of the magma source region to below the garnet stability threshold.

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Section: Geology Of the Tenpeak Plutonmentioning

confidence: 99%

Section: Geology Of the Tenpeak Plutonmentioning

confidence: 99%

Section: Geology Of the Tenpeak Plutonmentioning

confidence: 99%

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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

Shea

Miller

et al. 2018

Lithosphere

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“…The Schaefer Lake rocks in the White Mountain lobe are separated from the rest of the unit by map-scale, NW-trending Napeequa inclusions and a tongue of Napeequa unit on the east. The southern part of the tonalite, adjacent to the White River shear zone, is mapped separately as the sheeted complex (Miller and Paterson, 1999;Chan et al, 2017) (Fig. 2).…”

Section: Schaefer Lake Tonalitementioning

confidence: 99%

“…In this paper, we integrate a variety of structural, petrological, and geochemical data sets with previously published geochronologic data to analyze the processes that operated during construction and emplacement of the Tenpeak pluton and to a lesser extent the nearby, smaller Dirtyface pluton. Our work builds on mapping by the U.S. Geological Survey (Crowder et al, 1966;Cater and Crowder, 1967;Tabor et al, 1987), descriptive studies of Cater (1982), petrogenetic analysis of Dawes (1993) and Chan et al (2017), and the geochronological work of Matzel et al (2006). In particular, we address magma sources, shapes and orientations of magmatic increments, sizes of magma chambers, changes in magma compositions, construction processes and host rock displacement mechanisms with time, and potential relationships of the Tenpeak and Dirtyface plutons to coeval shallower-level intrusions.…”

Section: Introductionmentioning

confidence: 99%

Construction, emplacement, and geochemical evolution of deep-crustal intrusions: Tenpeak and Dirtyface plutons, North Cascades, western North America

2018

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Deep plutonic systems represent an important link between lowercrustal melt-generation sites and higher-level regions of magma accumulation, but models for these systems are limited by the relative scarcity of exposed weakly deformed, deep-crustal plutons. Exceptions include the ca. 92.3-89.7 Ma, dominantly tonalitic Tenpeak pluton and the smaller, nearby ca. 91 Ma Dirtyface pluton of the North Cascades (western North America), which represent deeply exposed crustal levels (~25-35 km) of a Cordilleran arc. Initial subduction-driven magmatism in the Tenpeak pluton was marked by co-magmatic hydrous mafic and felsic magmas, which formed gabbro, diorite, tonalite, and hornblendite within a heterogeneous mafic complex. High-MgO, Ni and Cr tonalitic magmas (Schaefer Lake subtype) with (e Nd) 0 of +4.8 to +5.8 accompanied or shortly followed this magmatism, and typify the Dirtyface intrusion. This early magmatism formed moderately to steeply dipping sheets, which are best developed in the southwestern margin of the Tenpeak pluton and in an internal zone with host rock rafts. As the system evolved, a different source was tapped to produce typical calc-alkaline magmas (Indian Creek subtype) that are more isotopically evolved (initial e Nd = +3.0 to +4.0). Magmas of this subtype formed bodies that are elliptical in map view and that truncated internal magmatic contacts and more strongly deformed tonalite, compatible with removal of older solidified and magmatic materials. The Schaefer Lake subtype terminated or was overwhelmed by the Indian Creek subtype in the youngest, high-volume magmas of the Tenpeak pluton. Both plutons have moderately to steeply dipping contacts that define the shape of an elongate asymmetric funnel to wedge. During sheet emplacement, magma wedging isolated and rotated rafts and blocks of host meta-supracrustal rock. Vertical, mostly downward transport of host rock GEOSPHERE

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Sheeted intrusion of granitic magmas in the upper crust – Emplacement and thermal evolution of the Guandacolinos pluton, NW Argentina

et al. 2021

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Formation of a sheeted intrusive complex within the deep-crustal Tenpeak pluton, North Cascades, Washington

Cited by 7 publications

References 77 publications

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

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

Construction, emplacement, and geochemical evolution of deep-crustal intrusions: Tenpeak and Dirtyface plutons, North Cascades, western North America

Sheeted intrusion of granitic magmas in the upper crust – Emplacement and thermal evolution of the Guandacolinos pluton, NW Argentina

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