Progress in Volcanology

Progress in Volcanology includes nine chapters in three sections. The first section is the “Introduction” while the other two sections speak on “Applied Volcanology” and “Volcanic Sedimentology, Geochemistry and Petrology.” The chapters address volcanology in several areas around the world, including Italy, Indonesia, Ethiopia, Argentina, India, and others

Rhyolite generation prior to a Yellowstone supereruption: insights from the Island Park-Mount Jackson rhyolite series

The Yellowstone volcanic field is one of the largest and best-studied centres of rhyolitic volcanism on Earth, yet it still contains little-studied periods of activity. Such an example is the Island Park–Mount Jackson series, which erupted between the Mesa Falls and Lava Creek caldera-forming events as a series of rhyolitic domes and lavas. Here we present the first detailed characterisation of these lavas and use our findings to provide a framework for rhyolite generation in Yellowstone between 1·3 and 0·6 Ma, as well as to assess whether magmatic evolution hints at a forthcoming super-eruption. These porphyritic (15–40% crystals) lavas contain mostly sanidine and quartz with lesser amounts of plagioclase (consistent with equilibrium magmatic modelling via rhyolite-MELTS) and a complex assemblage of mafic minerals. Mineral compositions vary significantly between crystals in each unit, with larger ranges than expected from a single homogeneous population in equilibrium with its host melt. Oxygen isotopes in quartz and sanidine indicate slight depletions (δ18Omagma of 5·0–6·1‰), suggesting some contribution by localised remelting of hydrothermally altered material in the area of the previous Mesa Falls Tuff-related caldera collapse. The preservation of variable O isotopic compositions in quartz requires crystal entrainment less than a few thousand years prior to eruption. Late entrainment of rhyolitic material is supported by the occurrence of subtly older sanidines dated by single-grain 40Ar/39Ar geochronology. The eruption ages of the lavas show discrete clusters illustrating that extended quiescence (>100 kyr) in magmatic activity may be a recurring feature in Yellowstone volcanism. Ubiquitous crystal aggregates, dominated by plagioclase, pyroxene and Fe–Ti oxides, are interpreted as cumulates co-erupted with their extracted liquid. Identical crystal aggregates are found in both normal-δ18O and low-δ18O rocks from Yellowstone, indicating that common petrogenetic processes characterise both volcanic suites, including the late-stage extraction of melt from an incrementally built upper crustal mush zone

Geochemistry and petrology of a suite of ten Yamato HED meteorites

We have performed petrological characterization and geochemical studies by instrumental neutron activation analysis of a suite of ten Yamato HED samples : Y-74013,Y-74097 and Y-74136 (Type A diogenites); Y-75032 and Y-791199 (Type B diogenites); Y-791195 (cumulate eucrite); Y-793164 and Y-82066 (eucrites); and Y-791192 and Y-82049 (polymict eucrites). The Type A diogenites are essentially identical in composition except for slight differences in Cr, Co, Se and La, which are likely due to inhomogeneous distribution of the minor phases chromite, metal and troilite, and trapped interstitial melt, respectively. The petrology and REE patterns for Type B diogenites show that they are not adcumulate rocks, but rather, contain substantial, perhaps 15%, interstitial liquid trapped in the samples. Y-791195 is a cumulate eucrite intermediate in REE content between Serra de Mage and Moore County, but is more ferroan. Eucrite Y-82066 is similar in composition to trace element-poor main-group eucrites such as Sioux County, and may be a primitive partial melt of the HED parent body. Y-793164 is intermediate in composition between main-group eucrites and Nuevo Laredo in Fe, Cr, Sc and REE, and is an intermediate member of the Nuevo Laredo trend eucrites. Y-793164 is a residual liquid from perhaps 25-30% crystallization of a primitive main-group eucrite like Sioux County or Y-82066. Y-791192 and Y-82049 are classified as polymict eucrites, but major and trace element concentrations indicate that these meteorites contain about 36% and 48% diogenitic material, respectively. These samples are howardites based on our analyses. Y-82049 contains a wide range of pyroxene compositions, from magnesian orthopyroxene similar to Type A diogenite pyroxenes, to ferroan pigeonite similar to basaltic eucrite pyroxenes. Large pyroxene clasts in Y-791192 are dominantly similar to Type B diogenite pyroxenes