Consequences of varied slab age and thermal structure on enrichment processes in the sub-arc mantle of the northern Cascadia subduction system

Green, Nathan L.; Sinha, A. K.

doi:10.1016/j.jvolgeores.2004.07.017

Cited by 30 publications

(28 citation statements)

References 54 publications

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“…For the entire 990 km arc length, this flux gives a total output of 7.7 × 10 9 mols CO 2 /yr, an observation that could be explained by cooler geothermal conditions. Nevertheless, our prediction that slab devolatilization occurs primarily in the fore arc is in good agreement with observations of the chemistry of erupted arc lavas [ Rose et al , 2001; Leeman et al , 2005; Green and Sinha , 2005]. For this scenario, a source for volcanic CO 2 in Cascadia would be contamination from the lithosphere below the volcanic arc.…”

Section: Discussionmentioning

confidence: 99%

Modeling open system metamorphic decarbonation of subducting slabs

Gorman

Kerrick

Connolly

2006

Geochem Geophys Geosyst

258

231

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[1] Fluids derived from the devolatilization of subducting slabs play a critical role in the melting of the mantle wedge and global geochemical cycles. However, in spite of evidence for the existence and mobility of an aqueous fluid phase during subduction metamorphism, the effect of this fluid on decarbonation reactions in subducting lithologies remains largely unquantified. In this study we present results from thermodynamic modeling of metamorphic devolatilization of subducted lithologies for pressures up to 6 GPa using an approach which considers fluid fractionation from source lithologies and infiltration from subjacent lithologies. This open system approach in which fluid flow is an intrinsic component of the chemical model offers an alternative to closed system models of subduction zone decarbonation. In general, our models simulating pervasive fluid flow in subducting lithologies predict CO 2 fluxes measured from volcanic arcs more closely than models which assume purely channelized flow. Despite the enhanced effect of H 2 O-rich fluid infiltration on subduction decarbonation, our results support the hypothesis that CO 2 is returned to the deep mantle at convergent margins, particularly in cool and intermediate subduction zones. Our results demonstrate that for most subduction zones, a significant proportion of the CO 2 derived from the slab is lost beneath the fore arc, and therefore CO 2 flux estimates based on measurements within the volcanic arc alone may significantly underestimate the slab-derived CO 2 flux for individual margins. Nevertheless, our predicted global slab-derived CO 2 flux from convergent margins of 0.35-3.12 Â 10 12 mols CO 2 /yr is in good agreement with previous estimates of global arc volcanic flux. Because our predicted global slab-derived CO 2 flux is significantly less than atmospheric CO 2 drawdown by chemical weathering, significant CO 2 emission from other geologic regimes (e.g., hot spots) would be required to balance the global carbon cycle.

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Section: Discussionmentioning

confidence: 99%

Modeling open system metamorphic decarbonation of subducting slabs

Gorman

Kerrick

Connolly

2006

Geochem Geophys Geosyst

258

231

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“…Ni and Cr contents range from 301 to 25 ppm and 373 to 24 ppm, respectively (Table S1). Petrographic details are discussed further in Green (2006), Green and Sinha (2005), Mullen and McCallum (2014), and Mullen and Weis (2013). Stratigraphic relationships and 40 Ar/ 39 Ar and K-Ar ages indicate all analyzed samples are less than 1 Myr old (details in Green, 2006 andMcCallum, 2014).…”

Section: Samples Analyzedmentioning

confidence: 99%

“…Meager) include previously published data from Mullen and McCallum (2014) and Mullen and Weis (2013) and are indicated as such in Table S1. We utilized splits of the same GVB basalt sample powders previously analyzed by Green (2006), Green and Sinha (2005), and Mullen and McCallum (2014), supplemented by one additional sample from Bridge River (THEC1) and one from Glacier Peak (GP11-01). Samples obviously affected by crustal contamination, as indicated by xenocrysts and/or xenoliths, were omitted from this study and are discussed further in Mullen and Weis (2013).…”

Section: Samples Analyzedmentioning

confidence: 99%

Evidence for trench-parallel mantle flow in the northern Cascade Arc from basalt geochemistry

Mullen

Weis

2015

Earth and Planetary Science Letters

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“…In general, modern Cascade arc magmas are thought to include only a small slab-derived fl uid component due to the young age of the subducting plate (Green and Sinha, 2005 …”

Section: Sediments In the Mantle Wedgementioning

confidence: 99%

“…States when compared to surrounding volcanic provinces such as the modern Cascade arc (e.g., Borg et al, 2002;Strong and Wolff, 2003;Leeman et al, 2004;Green and Sinha, 2005), Yellowstone and the Snake River Plain (e.g., Camp, 1995;Christiansen et al, 2002b;Jordan et al, 2004), the Western Great Basin (e.g., Fitton et al, 1988;Ormerod et al, 1988;Rogers et al, 1995;Cousens, 1996), the Mojave Desert and Basin and Range (e.g., Glazner et al, 1991;Perry et al, 1993;Farmer et al, 1995;Yogodzinski et al, 1996), and the San Andreas fault and offshore California (e.g., Cole and Basu, 1995;Davis et al, 1995;Dickinson, 1997).…”

Section: Introductionmentioning

confidence: 99%

Geology, geochronology, and geochemistry of the Miocene–Pliocene Ancestral Cascades arc, northern Sierra Nevada, California and Nevada: The roles of the upper mantle, subducting slab, and the Sierra Nevada lithosphere

et al. 2008

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The assemblage of ca. 28-3 Ma volcanic rocks exposed in the Lake Tahoe-Reno region of the northern Sierra Nevada, United States, is interpreted to be part of the Ancestral Cascades volcanic arc. The volcanic rocks are commonly highly porphyritic, including abundant plagioclase with clinopyroxene, amphibole, and rare biotite, and range from basaltic andesite to dacite in composition. Less common are poorly phyric, olivine-and clinopyroxene-bearing basalts and basaltic andesites. Porphyritic lavas dominate composite volcanic centers, whereas the poorly phyric lavas form isolated cinder cone and lava fl ow complexes. Tahoe-Reno arc lavas are calc-alkaline, enriched in the large ion lithophile elements but depleted in Nb and Ta relative to the light rare earth elements, and have highly variable radiogenic isotopic compositions. Compared to the modern south Cascade arc, Tahoe-Reno region basalts are enriched in the light rare earth and large ion lithophile elements and have higher 87 Sr/ 86 Sr and lower 143 Nd/ 144 Nd that are consistent with an old, subduction-modifi ed lithospheric mantle source, such as that proposed for lavas of the Western Great Basin. Melting of the lithospheric mantle may be enhanced by fl uid fl ux from the subducting slab if the Juan de Fuca slab dip is shallow. Andesites and dacites evolved from basaltic magmas by a combination of fractional crystallization and assimilation of lower crustal melts. Available geochronological data indicate that the westward sweep of Cenozoic volcanism through Nevada was associated with steepening of the slab dip, but the dip angle was lower during Miocene-Pliocene arc volcanism than it is today beneath the modern south Cascades.

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Consequences of varied slab age and thermal structure on enrichment processes in the sub-arc mantle of the northern Cascadia subduction system

Cited by 30 publications

References 54 publications

Modeling open system metamorphic decarbonation of subducting slabs

Modeling open system metamorphic decarbonation of subducting slabs

Evidence for trench-parallel mantle flow in the northern Cascade Arc from basalt geochemistry

Geology, geochronology, and geochemistry of the Miocene–Pliocene Ancestral Cascades arc, northern Sierra Nevada, California and Nevada: The roles of the upper mantle, subducting slab, and the Sierra Nevada lithosphere

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