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These hypotheses, used either explicitly or implicitly, have been in place for decades, but there remains little clear consensus about the relative contribution of the crust and mantle in producing volcanic diversity.
Decades of study on volcanic arcs have provided insight into the overarching processes that control magmatism, and how these processes manifest at individual volcanoes.
However, the causes of ubiquitous and dramatic intra-arc variations in volcanic flux and composition remain largely unresolved.
The map and the accompanying histograms illustrate the available Quaternary Cascade volcanic rock compositions from separated into three categories according to Si OIntra-arc volcanic diversity also contrasts with the modern concept of subduction as a continuous or quasi-continuous process, with progressive devolatilization in the descending slab continuously producing magma with the mantle wedge.
Likewise, the subduction parameters (slab age, slab dip, convergence rate and obliquity, and crustal thickness) that ultimately control the thermal state of a subduction zone typically change gradually along strike.
Helens and Soufrière Hills, can be ported to other parts of the systems that are less well known.
Moreover, geochemical sampling of arc volcanics is strongly biased by these locations of intense interest, such as well exposed or recently active volcanoes, and geochemical sampling programs are almost never designed to produce ergodic or representative datasets of erupted compositions through space and time.Investigating such arc-scale issues requires greater quantitative comparison of geophysical and geochemical data, linked through sets of common intensive variables.To work towards these goals, we use observed lava compositions to estimate the heat budget associated with Quaternary volcanism in the Cascades Arc and compare this to the heat required to produce the observed geophysical properties of the crust.Right, archetypical upper crust-focused subduction volcano cartoon, with a “disembodied volcano”, disconnected from the deeper magma source region Here, we propose a multidisciplinary approach that strives to transcend some of these limitations.We use this approach to address the causes of intra-arc volcanic diversity in the Cascades, but we believe that the method can also be applied to other frontier questions in subduction zone science.This diversity is expressed as, among other things, large variations in erupted compositions, erupted volumes, edifice numbers, eruption style, and morphology between individual volcanoes and subarc segments—and even between volcanoes that lie in close spatial association.In the Cascades Arc, for example, erupted volumes differ by a factor of two between the southern and northern portions of the arc, and there are major changes in the partitioning of volcanism between intermediate and silicic-dominated central volcanic edifices and fields of more mafic and dispersed monogenetic centers (Fig. Similarly, there are large variations in the geophysical state of the crust observed along strike in many arcs, including crustal and upper mantle seismic velocities and measured heat flow Map of Cascades Arc showing locations of geochemical samples and selected summaries of the existing datasets.This is exemplified by the summary cartoon figures that classically accompany papers from the relevant scientific communities (including those we have written ourselves), with “disembodied volcanoes” missing the lower half of the magmatic system in the volcanology literature, or oversized “emoji volcanoes” that only allude to a shallower magmatic system in mantle-oriented petrologic studies (Fig. Representative figures from different communities studying volcanoes.Left, archetypical mantle-focused subduction cartoon with an “emoji volcano” that only alludes to a shallower magmatic system.The approach utilizes our basic understanding of the physical processes involved in volcanic arc formation to find intensive variables, such as specific heat and density, which can be used to quantitatively link and compare large-scale datasets from different disciplines.We also incorporate statistical techniques to minimize the effects of nonrepresentative geochemical sampling.