Geochemical and petrological investigation into the magmatic system at Soufrière Hills Volcano, Montserrat.

Andesite lavas from the current eruption of the Soufrière Hills Volcano, Montserrat exhibit evidence for magma mingling, related to the intrusion of mafic magma at depth. The processes of mass transfer and flux of material involved in the interaction between mafic and silicic magmas are crucial for understanding eruption dynamics. Detailed textural, petrological and geochemical analyses coupled with field observations are used to define a classification scheme for mafic enclave types in erupted andesite from phase V (2009–2010). Type A are closest to a mafic end-member, whereas type B are significantly hybridised. Type A quench crystallisation is driven by rapid thermal equilibration during injection into the andesite. Type B enclaves form from a slower cooling vesiculating hybridised melt layer. Type C, are a composite of types A and types B, representing an interface between the types. Geochemical modelling shows that since the start of the current eruption that the dominant control on the range of enclave bulk compositions has changed from fractional crystallisation to mixing of the mafic end-member and host andesite. A change in selected elements concentrations in the mafic end-member is observed from phases I to III, halting in phase V. Volatile flux from the mafic to andesite magmas plays a vital role in eruption dynamics, but evidence for vapour transport in the erupted lavas is rarely preserved. Geochemical and petrological evidence is presented for the segregation and transport of metal-bearing vapour in shear fractures generated in the shallow conduit or dome during magma ascent. Elevated metal concentrations (Cu, Au, Ag, Pb, Zn) indicate magmatic vapours transport. Volatiles were resorbed into the partial melt generated during frictional heating (>1000 °C) at the slip surface as a peraluminous partial melt recrystallised. The shear zones provide evidence for degassing and an insight into controls on eruption style

Spotlight on deep carbon research.

Professor Marie Edmonds is a volcanologist at the University of Cambridge. She is interested in the role of magmatic volatiles in magma genesis, volcanic eruptions, and volatile geochemical cycling. Dr. Robert Hazen is a geologist at Carnegie Science and executive director of the Deep Carbon Observatory. His latest research has focused on the co-evolution of the geospheres and biospheres, and mineral diversity and distribution. Marie and Robert apply their research to help understand the chemical and biological roles of carbon in Earth

Caught in the act: Implications for the increasing abundance of mafic enclaves during the eruption of the Soufriere Hills Volcano, Montserrat

An exceptional opportunity to sample several large blocks sourced from the same region of the growing Soufrière Hills lava dome has documented a significant increase in the presence of mafic enclaves in the host andesite during the course of a long-lived eruptive episode with several phases. In 1997 (Phase I) mafic inclusions comprised ~1 volume percent of erupted material; in 2007 (Phase III) deposits their volumetric abundance increased to 5–7 percent. A broader range of geochemically distinctive types occurs amongst the 2007 enclaves. Crystal-poor enclaves generally have the least evolved (basaltic) compositions; porphyritic enclaves represent compositions intermediate between basaltic and andesitic compositions. The absence of porphyritic enclaves prior to Phase III magmatism at Soufrière Hills Volcano suggests that a mixing event occurred during the course of the current eruptive episode, providing direct evidence consistent with geophysical observations that the system is continuously re-invigorated from depth

Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans

Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in 25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16 regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP, while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium (LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region. Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa, an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent signals within the same regio