Bismuth‐melt trails trapped in cassiterite–quartz veins

Native bismuth in the form of metallic melt has been considered instrumental to the formation of some metallic ore deposits via a mechanism dubbed the “Liquid Bismuth Collector Model.” Here, we provide petrographical documentation of trail‐forming, μm‐sized blebs of native bismuth in cassiterite–quartz veins from the Santa Bárbara greisen Sn deposit in the Rondônia tin province of northern Brazil. These inclusions suggest the trapping of a Bi melt that took place during vein formation, in a mechanism similar to the entrapment of fluid inclusions.     

Metals discharged during different flow conditions from a mixed agricultural‐forest catchment (NW Spain)

Metal loads were determined from water samples collected under different streamflow conditions (baseflow and storm events) in a rural catchment (NW Spain) during 4 years. A study at annual, seasonal and storm‐event scales was carried out. In all analysed scales, the export order was Fe > Al > Mn > Zn > Cu. A high inter‐annual, seasonal and storm‐event scale variability of metal load was observed. The total metal loads in stream were higher during baseflow conditions than during storm events, which only represented 4% of the duration of the study period and 25% of streamflow. During storm events, both Al and Fe loads accounted 45% of the total load of the study period, whereas Mn, Cu and Zn loads represented 42%, 33% and 24%, respectively. This highlights the role of high flows on metal export. Only four big events exported around 30% of load of each metal transported in events. At all time scales, a prevalence of export of particulate metals over dissolved metals was observed, more pronounced for Al, Fe and Mn than for Cu and Zn. The export of metals in the Corbeira catchment is influenced by runoff and, to a lesser extent, by the rainfall amount. Copyright © 2014 John Wiley & Sons, Ltd.     

Exploring lava‐flow hazards at Pico Island,Azores Archipelago (Portugal)

Pico, the youngest island of the Azores Archipelago (Portugal), is characterized by a central volcano and a 30‐km‐long fissure zone. Its eruption rate is the highest of the Azores islands, with more than 35 eruptions in the last 2000 years. Here, we estimate the lava‐flow hazard for Pico Island by combining the vent opening probability derived from the spatial distribution of eruptive fissures, the classes of expected eruptions inferred from the physical and chemical characteristics of historical eruptions, and the lava‐flow paths simulated by the MAGFLOW model. The most likely area to host new eruptions is along a WNW–ESE trend centred on the central volcano, with the highest hazard affecting the two main residential zones of Lajes do Pico and Madalena. Our analysis is the first attempt to assess the lava‐flow hazard for Pico Island, and may have important implications for decision‐making in territorial management and future land‐use planning.     

Detecting the stepwise propagation of the Eastern Sicily thrust belt (Italy): insight from thermal and thermochronological constraints

An extensive dataset of vitrinite reflectance, FTIR parameters on organic matter, illite content in mixed layers illite‐smectite, apatite fission tracks and U‐Th/He dating has been used to reconstruct the stepwise propagation of the Eastern Sicily fold‐and‐thrust belt during Late Palaeogene and Neogene times. The results indicate that the fold‐and‐thrust belt is divisible into two levels of thermal maturity. These levels consist of a less evolved level of thermal maturity that records limited sedimentary burial and minor heating, and a more evolved level of thermal maturity that indicates tectonic burial and exhumation at different times. Deformation and exhumation of shallowly buried units are linked to wedge forward propagation by low‐angle thrusts, whereas the evolution of deeply buried units is associated with tectonic imbrications by duplex formation and steep thrusts. The two tectonic styles alternate during evolution of the fold‐and‐thrust belt under low erosion rates.     

In situ high-temperature X-ray diffraction and spectroscopic study of fibroferrite,FeOH(SO<Subscript>4</Subscript>)·5H<Subscript>2</Subscript>O

The thermal dehydration process of fibroferrite, FeOH(SO₄)·5H₂O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature synchrotron X-ray powder diffraction (HT-XRPD), in situ high-temperature Fourier transform infrared spectroscopy (HT-FTIR) and thermal analysis (TGA-DTA) combined with evolved gas mass spectrometry. The data analysis allowed the determination of the stability fields and the reaction paths for this mineral as well as characterization of its high-temperature products. Five main endothermic peaks are observed in the DTA curve collected from room T up to 800 °C. Mass spectrometry of gases evolved during thermogravimetric analysis confirms that the first four mass loss steps are due to water emission, while the fifth is due to a dehydroxylation process; the final step is due to the decomposition of the remaining sulfate ion. The temperature behavior of the different phases occurring during the heating process was analyzed, and the induced structural changes are discussed. In particular, the crystal structure of a new phase, FeOH(SO₄)·4H₂O, appearing at about 80 °C due to release of one interstitial H₂O molecule, was solved by ab initio real-space and reciprocal-space methods. This study contributes to further understanding of the dehydration mechanism and thermal stability of secondary sulfate minerals.