Timescales of Quartz Crystallization and the Longevity of the Bishop Giant Magma Body

Supereruptions violently transfer huge amounts (100 s–1000 s km3) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted ∼760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of <10,000 years, more typically within 500–3,000 years before eruption. We conclude that large-volume, crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency–Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

The volcanogenetic significance of garnet-bearing minor intrusions within the Borrowdale Volcanic Group Eskdale area, Cumbria

AbstractA number of garnetiferous minor intrusions have been mapped within the Borrowdale Volcanic Group. They underlie garnetiferous extrusive volcanic rocks which occur toward the top of a sequence of ignimbrite and lava – the Airy's Bridge Formation – which is the product of a major caldera-forming eruptive episode. Garnet and whole-rock geochemistry indicate that most of the intrusions are indistinguishable from garnetiferous dacite forming the final eruptive unit of the Airy's Bridge Formation: a co-magmatic link is therefore postulated. One of the intrusions, which intrudes the Airy's Bridge Formation, is distinct and may be related to the later Eskdale pluton.It is suggested that following the emplacement of ignimbrites forming the basal half of the Airy's Bridge Formation, caldera collapse partially sealed a fissure-conduit system and degassed, garnet-bearing magma was intruded as dykes and sills and locally extruded as a post-explosive lava dome. It is also postulated that garnet crystallized in a high-level magma chamber (P &lt; 3 kb) and that reverse chemical zoning was due to growth while sinking through compositionally stratified magma.</jats:p

Geochemical, mineralogical, and isotopic data relating to the origin and tectonic setting of the Rossland volcanic rocks, southern British Columbia

Bulk-rock and mineral chemical and isotopic analyses of Rossland volcanic rocks are used to infer the nature of the magma extruded in the Nelson–Rossland area of southern British Columbia during the Early Jurassic. Metamorphism of the volcanic rocks to subgreenschist and greenschist facies precludes use of mobile major and trace elements (e.g., Na, K, and Rb) as petrogenetic indicators. Data on immobile elements (Ti, Zr, and Y) and pyroxene compositions indicate that the volcanic rocks formed in a destructive-margin plate tectonic environment. Present-day 87Sr/86Sr ratios range from 0.70372 to 0.70480 but do not define an isochron. Corrected to Jurassic time, the initial ratios range from 0.70328 to 0.70404. Whole-rock δO18 values range from 7.9 to 11.6%, correlating inversely with metamorphic grade. Clinopyroxene δO18 of 4.8–6.5 is comparable with fresh clinopyroxenes from mafic rocks of mantle origin. In view of the preponderance of basaltic rather than andesitic rock types, and because of the nature of the lithologies within the volcanic rocks and associated sediments, an island-arc setting is indicated. The appearance of primary amphibole in basaltic members of the Rossland suite, and the occurrence of ankaramitic rocks, are thought to indicate a mildly alkalic rather than a subalkalic parent magma. Comparison of the Rossland volcanic rocks with those of recent island arcs, and consideration of the Upper Triassic – Lower Jurassic paleogeography in the Cordillera, suggest the rocks may be related to a localized oceanic basin, their extrusion being associated with faults bounding its western edge. </jats:p