Rhyolites—Hard to produce, but easy to recycle and sequester: Integrating microgeochemical observations and numerical models

摘要: Recent discoveries of isotopically diverse minerals, i.e., zircons, quartz, and feldspars, in large-volume ignimbrites smaller lavas from the Snake River Plain (SRP; Idaho, USA), Iceland, Kamchatka Peninsula, other environments suggest that this phenomenon characterizes many silicic units studied by situ methods. This observation leads to need for new models magma petrogenesis involve double or triple recycling zircon-saturated rocks. Initial partial melts are produced small quantities which zircons minerals undergo solution reprecipitation inherit isotopic signatures immediate environment host batch. Next, polythermal batches with inherited crystals merge together into larger volume bodies, where they mix then erupt. Concave-up polymodal crystal size distributions quartz observed may be explained two three episodes reprecipitation. Hafnium isotope diversity demonstrates variable mixing crustal mantle-derived differentiates. The low δ 18 O values magmas O-diverse indicate generation happens remelting variably hydrothermally altered, thus O, protoliths batch, minute voluminous, low-δ values. also indicates processes generate zircon happen at shallow depths a few kilometers, meteoric water can circulate large water/rock ratios imprint on protolith. We further review newly emerging evidence their appearance end magmatic evolution long-lived centers SRP elsewhere, indicating genesis rhyolites sometimes altered subsolidus predecessors common evolutionary trend worldwide, especially hotspot rift high heat fluxes. we use thermomechanical finite element modeling rhyolite explain (1) formation stress fields dike capture deflection as function underpressurization overpressurization, respectively; (2) merging neighboring via four related mechanisms: melting through screen rock melt zone expansion, brittle failure separating rocks, buoyant magmas, explosive an overpressurized interstitial fluid phase (heated water); (3) time scales efficacies extended horizontal scales, expressed marker method particle tracking. envisioned advective mechanisms segregation upper crust characterize periods increased basaltic output mantle, leading production, but serve analogues chambers made dispersed batches. Although not focus work, stable long term, coalescence creates ephemeral, short-lived eruptable bodies erupt nearly completely.