Pre- and syn-eruptive degassing and crystallisation processes of the 2010 and 2006 eruptions of Merapi volcano,Indonesia     

Katie?PreeceEmail author  Ralf?Gertisser  Jenni?Barclay  Kim?Berlo  Richard?A.?Herd  Edinburgh Ion Microprobe Facility 《Contributions to Mineralogy and Petrology》2014,168(4):1061

The 2010 eruption of Merapi (VEI 4) was the volcano’s largest since 1872. In contrast to the prolonged and effusive dome-forming eruptions typical of Merapi’s recent activity, the 2010 eruption began explosively, before a new dome was rapidly emplaced. This new dome was subsequently destroyed by explosions, generating pyroclastic density currents (PDCs), predominantly consisting of dark coloured, dense blocks of basaltic andesite dome lava. A shift towards open-vent conditions in the later stages of the eruption culminated in multiple explosions and the generation of PDCs with conspicuous grey scoria and white pumice clasts resulting from sub-plinian convective column collapse. This paper presents geochemical data for melt inclusions and their clinopyroxene hosts extracted from dense dome lava, grey scoria and white pumice generated during the peak of the 2010 eruption. These are compared with clinopyroxene-hosted melt inclusions from scoriaceous dome fragments from the prolonged dome-forming 2006 eruption, to elucidate any relationship between pre-eruptive degassing and crystallisation processes and eruptive style. Secondary ion mass spectrometry analysis of volatiles (H₂O, CO₂) and light lithophile elements (Li, B, Be) is augmented by electron microprobe analysis of major elements and volatiles (Cl, S, F) in melt inclusions and groundmass glass. Geobarometric analysis shows that the clinopyroxene phenocrysts crystallised at depths of up to 20 km, with the greatest calculated depths associated with phenocrysts from the white pumice. Based on their volatile contents, melt inclusions have re-equilibrated during shallower storage and/or ascent, at depths of ~0.6–9.7 km, where the Merapi magma system is interpreted to be highly interconnected and not formed of discrete magma reservoirs. Melt inclusions enriched in Li show uniform “buffered” Cl concentrations, indicating the presence of an exsolved brine phase. Boron-enriched inclusions also support the presence of a brine phase, which helped to stabilise B in the melt. Calculations based on S concentrations in melt inclusions and groundmass glass require a degassing melt volume of 0.36 km³ in order to produce the mass of SO₂ emitted during the 2010 eruption. This volume is approximately an order of magnitude higher than the erupted magma (DRE) volume. The transition between the contrasting eruptive styles in 2010 and 2006 is linked to changes in magmatic flux and changes in degassing style, with the explosive activity in 2010 driven by an influx of deep magma, which overwhelmed the shallower magma system and ascended rapidly, accompanied by closed-system degassing.  相似文献   

Titanium- and water-rich metamorphic olivine in high-pressure serpentinites from the Voltri Massif (Ligurian Alps,Italy): evidence for deep subduction of high-field strength and fluid-mobile elements     

Jan?C.?M.?De HoogEmail author  Keiko?Hattori  Haemyeong?Jung 《Contributions to Mineralogy and Petrology》2014,167(3):990

Titanium- and water-rich metamorphic olivine (Fo 86–88) is reported from partially dehydrated serpentinites from the Voltri complex, Ligurian Alps. The rocks are composed of mostly antigorite and olivine in addition to magnetite, chlorite, clinopyroxene and Ti-clinohumite. In situ secondary ion mass spectrometry (SIMS) data show that metamorphic olivine has very high and strongly correlated H₂O (up to 0.7 wt%) and TiO₂ contents (up to 0.85 wt%). Ti-rich olivine shows colourless to yellow pleochroism. Olivine associated with Ti-clinohumite contains low Ti, suggesting that Ti-rich olivine is not the breakdown product of Ti-clinohumite. Fourier transform infrared spectroscopy (FTIR) absorption spectra show peaks of serpentine, Ti-clinohumite and OH-related Si vacancies. Combining FTIR and SIMS data, we suggest the presence of clustered planar defects or nanoscale exsolutions of Ti-clinohumite in olivine. These defects or exsolutions contain more H₂O (x ~ 0.1 in the formula 4Mg₂SiO₄·(1?x)Mg(OH,F)₂·xTiO₂) than Ti-clinohumite in the sample matrix (x = 0.34–0.46). In addition to TiO₂ and H₂O, secondary olivine contains significant Li (2–60 ppm), B (10–20 ppm), F (10–130 ppm) and Zr (0.9–2.1 ppm). It is enriched in ¹¹B (δ¹¹B = +17 to +23 ‰). Our data indicate that secondary olivine may play a significant role in transporting water, high-field strength and fluid-mobile elements into the deeper mantle as well as introduce significant B isotope anomalies. Release of hydrogen from H₂O-rich olivine subducted into the deep mantle may result in strongly reduced mantle domains.  相似文献   

Temporal evolution and compositional signatures of two supervolcanic systems recorded in zircons from Mangakino volcanic centre,New Zealand     

George?F.?CooperEmail author  Colin?J.?N.?Wilson  Bruce?L.?A.?Charlier  Joseph?L.?Wooden  Trevor?R.?Ireland 《Contributions to Mineralogy and Petrology》2014,167(6):1018

Mangakino, the oldest rhyolitic caldera centre delineated in the Taupo Volcanic Zone of New Zealand, generated two very large (super-sized) ignimbrite eruptions, the 1.21 ± 0.04 Ma >500 km³ Ongatiti and ~1.0 Ma ~1,200 km³ Kidnappers events, the latter of which was followed after a short period of erosion by the ~200 km³ Rocky Hill eruption. We present U/Pb ages and trace-element analyses on zircons from pumice clasts from these three eruptions by Secondary Ion Mass Spectrometry (SIMS) using SHRIMP-RG instruments to illustrate the evolution of the respective magmatic systems. U–Pb age spectra from the Ongatiti imply growth of the magmatic system over ~250 kyr, with a peak of crystallisation around 1.32 Ma, ~100 kyr prior to eruption. The zircons are inferred to have then remained stable in a mush with little crystallisation and/or dissolution before later rejuvenation of the system at the lead-in to eruption. The paired Kidnappers and Rocky Hill eruptions have U–Pb zircon ages and geochemical signatures that suggest they were products of a common system grown over ~200 kyr. The Kidnappers and Rocky Hill samples show similar weakly bimodal age spectra, with peaks at 1.1 and 1.0 Ma, suggesting that an inherited antecrystic population was augmented by crystals grown at ages within uncertainty of the eruption age. In the Kidnappers, this younger age peak is dominantly seen in needle-shaped low U grains with aspect ratios of up to 18. In all three deposits, zircon cores show larger ranges and higher absolute concentrations of trace elements than zircon rims, consistent with zircon crystallisation from evolving melts undergoing crystal fractionation involving plagioclase and amphibole. Abundances and ratios of many trace elements frequently show variations between different sectors within single grains, even where there is no visible sector zoning in cathodoluminescence (CL) imaging. Substitution mechanisms, as reflected in the molar (Sc + Y + REE³⁺)/P ratio, differ in the same growth zone between the sides (along a-axis and b-axis: values approaching 1.0) and tips (c-axis: values between 1.5 and 5.0) of single crystals. These observations have implications for the use of zircons for tracking magmatic processes, particularly in techniques where CL zonation within crystals is not assessed and small analytical spot sizes cannot be achieved. These observations also limit applicability of the widely used Ti-in-zircon thermometer. The age spectra for the Ongatiti and Kidnappers/Rocky Hill samples indicate that both magmatic systems were newly built in the time-breaks after respective previous large eruptions from Mangakino. Trace element variations defining three-component mixing suggest that zircons, sourced from multiple melts, contributed to the population in each system.  相似文献   

A contribution to regional stratigraphic correlations of the Afro-Brazilian depression – The Dom João Stage (Brotas Group and equivalent units – Late Jurassic) in Northeastern Brazilian sedimentary basins     

Juliano Kuchle  Claiton Marlon dos Santos Scherer  Christian Correa Born  Renata dos Santos Alvarenga  Felipe Adegas 《Journal of South American Earth Sciences》2011,31(4):358-371

The Dom João Stage comprises an interval with variable thickness between 100 and 1200 m, composed of fluvial, eolian and lacustrine deposits of Late Jurassic age, based mainly on the lacustrine ostracod fauna (although the top deposits may extend into the Early Cretaceous). These deposits comprise the so-called Afro-Brazilian Depression, initially characterized as containing the Brotas Group of the Recôncavo Basin (which includes the Aliança and the Sergi Formations) and subsequently extended into the Tucano, Jatobá, Camamu, Almada, Sergipe, Alagoas and Araripe Basins in northeastern Brazil, encompassing the study area of this paper. The large occurrence area of the Dom João Stage gives rise to discussions about the depositional connectivity between the basins, and the real extension of sedimentation. In the first studies of this stratigraphic interval, the Dom João Stage was strictly associated with the rift phase, as an initial stage (decades of 1960–70), but subsequent analyses considered the Dom João as an intracratonic basin or pre-rift phase – without any relation to the active mechanics of a tectonic syn-rift phase (decades of 1980–2000). The present work developed an evolutionary stratigraphic and tectonic model, based on the characterization of depositional sequences, internal flooding surfaces, depositional systems arrangement and paleoflow directions. Several outcrops on the onshore basins were used to build composite sections of each basin, comprising facies, architectural elements, depositional systems, stratigraphic and lithostratigraphic frameworks, and paleocurrents. In addition to that, over a hundred onshore and offshore exploration wells were used (only 21 of which are showed) to map the depositional sequences and generate correlation sections. These show the characteristics and relations of the Dom João Stage in each studied basin, and they were also extended to the Gabon Basin. The results indicate that there were two main phases during the Dom João Stage, in which distinctive sedimentary environments were developed, reflecting depositional system arrangements, paleoflow directions were diverse, and continuous or compartmented basins were developed.  相似文献   

Long-Term Correlation Between the Nao and Solar Activity     

Renata Lukianova  Genrich Alekseev 《Solar physics》2004,224(1-2):445-454

We extend the correlation analysis of solar signals and the North Atlantic Oscillation (NAO) back in time by using the aa index (since 1868) and the PC index (since 1948) as a proxy of the solar wind energy imparted to the magnetosphere. Prior to the 1940s the records of the NAO and the aa index were not closely connected, while after the 1940s their rhythms matched. We compare two distinctive periods with recent results on the long-scale reconstruction of solar activity. The shift in the NAO–aa interconnection can provide the explanation of a significant increase of solar activity after the 1940s. A strengthening of the interplanetary magnetic field leads to more intensive variations of the high-latitude ionospheric electric field that influences the atmospheric circulation.  相似文献   

A rational method for determining the swelling pressure of expansive soils: Paired swell test (PS-test)     

Selçuk  Levent 《Acta Geotechnica》2022,17(8):3161-3180

Acta Geotechnica - Experimental investigations on the expansion behavior of clayey soils are of great importance to correctly understand the response of the soil–foundation. In this context,...  相似文献   

Colloidal Stability and Toxicity of Gold Nanoparticles and Gold Chloride on <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>     

Renata Behra  Bettina Wagner  Linn Sgier  David Kistler 《Aquatic Geochemistry》2015,21(2-4):331-342

Here we have examined interactions of gold nanoparticles differing in primary particle size and coating with the green algae Chlamydomonas reinhardtii as function of the colloidal stability of the particles in the experimental media used for toxicity studies. Interactions of dissolved Au³⁺ ions with algae were also examined. Included endpoints were photosynthetic yield and algal growth. Morphological and structural effects were examined microscopically and by flow cytometry. The results indicate no significant toxicity of gold nanoparticles to C. reinhardtii. Analysis of published data suggests toxicity of gold nanoparticles on algal growth to relate rather to particular coatings than to the gold core.  相似文献   

Combined low-thrust propulsion and invariant manifold trajectories to capture NEOs in the Sun–Earth circular restricted three-body problem     

G.?MingottiEmail author  J.?P.?Sánchez  C.?R.?McInnes 《Celestial Mechanics and Dynamical Astronomy》2014,120(3):309-336

In this paper, a method to capture near-Earth objects (NEOs) incorporating low-thrust propulsion into the invariant manifolds technique is investigated. Assuming that a tugboat-spacecraft is in a rendez-vous condition with the candidate asteroid, the aim is to take the joint spacecraft-asteroid system to a selected periodic orbit of the Sun–Earth restricted three-body system: the orbit can be either a libration point periodic orbit (LPO) or a distant prograde periodic orbit (DPO) around the Earth. In detail, low-thrust propulsion is used to bring the joint spacecraft-asteroid system from the initial condition to a point belonging to the stable manifold associated to the final periodic orbit: from here onward, thanks to the intrinsic dynamics of the physical model adopted, the flight is purely ballistic. Dedicated guided and capture sets are introduced to exploit the combined use of low-thrust propulsion with stable manifolds trajectories, aiming at defining feasible first guess solutions. Then, an optimal control problem is formulated to refine and improve them. This approach enables a new class of missions, whose solutions are not obtainable neither through the patched-conics method nor through the classic invariant manifolds technique.  相似文献   

The adsorption and interaction of long-chain fatty acids and heavy metals at the mercury electrode/sodium chloride solution interface     

Damir Krznarić  Boẑena Ćosović  Zlata Kozarac 《Marine Chemistry》1983,14(1):17-29

The reduction of heavy metals (cadmium, lead and zinc) in the presence of long-chain fatty acids (lauric, oleic and linoleic) in 0.55 mol dm^?3 NaCl and 0.03 mol dm^?3 NaHCO₃ at pH 8.7 has been studied by differential pulse polarography. The increase of the peak height of investigated metals by up to tenfold the value obtained in electrolyte without fatty acid is due to adsorption of metal ions at the electrode surface. The accumulation of metal increases with the increase of adsorption time (at potentials more positive than the reduction potential of the particular metal) and with increase of salinity. The heavy-metal adsorption depends on the concentrations of both metal ions and fatty acids. The interaction of heavy metals with the unsaturated fatty acids in the bulk and/or in the adsorbed layer at different natural interfaces could be of considerable importance in an understanding of the fate and distribution of heavy metals in the natural aquatic environment.  相似文献   

Laboratory Measurement and Correction of Thermal Properties for Application to the Rock Mass     

D.?A.?GunnEmail author  L.?D.?Jones  M.?G.?Raines  D.?C.?Entwisle  P.?R.?N.?Hobbs 《Geotechnical and Geological Engineering》2005,23(6):773-791

The requirement for quantitative thermal property data in assessing the performance of an engineered repository is identified. Experimental methods for the measurement of thermal conductivity, thermal expansivity and heat capacity are outlined and typical test results are presented for two rock-types of interest in relation to the Sellafield site. The controls on the thermal properties are discussed and a series of corrections from the rock material to the rock mass properties are presented. Finally, a correction scheme that accounts for the effect of scale is followed.  相似文献