Differentiation in Sheared Granular Magma

2020 ◽  
Author(s):  
Nick Petford ◽  
John Clemens ◽  
Curt Koenders
Keyword(s):  
Magma Mixing ◽  
Shear Zones ◽  
Mineral Chemistry ◽  
Quantitative Model ◽  
Chemical Components ◽  
High Definition ◽  
Volume Increase ◽  
Recent Developments ◽  
Dilatancy Effect ◽  
Reverse Zoning

<p>Recent developments in high definition mineral chemistry at the grain scale are shedding new light on the processes and rates of magma storage, differentiation and eruption. However, the complementary physics and fluid dynamics of magma as a granular material are still based on viscous compaction theory, which may not be relevant in sub-volcanic settings where magma is being deformed by external shear. We present a quantitative model for shear deformation of a crystallised dense magma (>70% solid) with poro-elastic properties where the critical link between the mechanics and associated compositional changes in the melt are governed by dilation (volume increase) of the granular skeleton. Key material parameters governing the dilatancy effect include magma permeability, mush strength, the shear modulus and the contact mechanics and geometry of the granular assemblage. Calculations show that dilation reduces the interstitial fluid (melt) pressure to produce a ‘suction’ effect. At shear strain rates in excess of the tectonic background, deformation-induced melt flow can redistribute chemical components and heat between regions of crystallising magma with contrasting rheological properties, at velocities far in excess of diffusion or buoyancy forces, the latter of course the driving force behind fractional crystallisation and compaction. Unlike static magmas, there is no ‘lock-up’ state above which the interstitial melt cannot percolate. Co-mingling of hotter, indigenous melt has the potential to interrupt (or locally reverse) fractionation trends and produce reverse zoning or resorbtion of crystals, mimicking some of the textural effects attributed to magma mixing. Post-failure instabilities include hydraulic rupture of the mush along shear zones with potential for larger scale extraction and redistribution of evolved melt. A novel feature of congested, sub-volcanic granular magma is that the eruption itself helps drive rapid melt extraction, negating the requirement to first segregate large volumes of evolved melt as a precursor. </p>

scholarly journals The Application of Catalytic Processes on the Production of Algae-based Biofuels: A Review

2020 ◽  
Author(s):  
Antonio Zuorro ◽  
Janet B. García-Martínez ◽  
Andrés F. Barajas-Solano
Keyword(s):  
Fossil Fuels ◽  
Operating Conditions ◽  
Thermochemical Conversion ◽  
Chemical Components ◽  
High Carbon ◽  
Microalgal Biomass ◽  
Microalgae Biomass ◽  
End Products ◽  
Recent Developments ◽  
Thermochemical Processes

Over the last decades, microalgal biomass has gained a significant role in the development of different high-end (nutraceuticals, colorants, food supplements, and pharmaceuticals) and low-end products (biodiesel, bioethanol, and biogas) due to rapid growth and high carbon fixing efficiency. Therefore, microalgae are considered a useful and sustainable resource to attain energy security while reducing our current reliance on fossil fuels. From the technologies available for obtaining biofuels using microalgae biomass, thermochemical processes (pyrolysis, HTL, gasification) have proven to be processed with higher viability, because they use all biomass. However, the biocrudes obtained from direct thermochemical conversion have substantial quantities of heteroatoms (oxygen, nitrogen, and sulfur) due to the complexity of the biomass's content of chemical components (lipids, carbohydrates, and proteins). As a solution, catalyst-based processes have emerged as a sustainable solution for the increase in biocrude production. This paper's objective is to present a comprehensive review of recent developments on catalyst mediated conversion of algal biomass. Special attention will be given to operating conditions, strains evaluated, and challenges for the optimal yield of algal-based biofuels through pyrolysis and HTL.

scholarly journals Mineral Chemistry Studies and Evidences For Magma Mixing of Bala Zard Basic- Intermediate Volcanic Rocks, Lut Block, Iran

2015 ◽  
Vol 10 (Special-Issue1) ◽  
pp. 1194-1205 ◽  
Author(s):  
Omid Namin ◽  
Afshin Ardalan ◽  
Mohammad Razavi ◽  
Arash Gourabjeripour ◽  
Abdollah Yazdi
Keyword(s):  
Magma Mixing ◽  
Volcanic Rocks ◽  
Mineral Chemistry ◽  
Lut Block

Mineral chemistry and geothermobarometry of the Balıkesir Volcanites (NW Anatolia, Turkey) 

2021 ◽  
Author(s):  
Alp Ünal ◽  
Şafak Altunkaynak
Keyword(s):  
Mineral Composition ◽  
Magma Chamber ◽  
Magma Mixing ◽  
Textural Properties ◽  
Mineral Chemistry ◽  
Oscillatory Zoning ◽  
Magma Chamber Processes ◽  
Crystallization Conditions ◽  
Compositional Variations ◽  
Opaque Minerals

<p>Balıkesir Volcanites (BV) are included into the Balıkesir Volcanic Province and contain various products of Oligo-Miocene volcanic activity in NW Anatolia. BV are formed from trachyandesite, andesite and dacite lavas with associated pyroclastic rocks. In this study, we report the petrographical investigations, mineral chemistry results and geothermobarometry calculations of the Balıkesir Volcanites in order to deduce the magma chamber processes and crystallization conditions. Andesites present a mineral composition of plagioclase (An35–50) + amphibole (edenitic hornblende) +biotite ± quartz and opaque minerals. The major phenocryst phases in dacite lavas are plagioclase (An39–53), quartz, amphibole (magnesio-hornblende), biotite, sanidine and opaque minerals. The mineral composition of the trachyandesites, on the other hand, is represented by plagioclase (An38–57) + amphibole (pargasitic hornblende) + biotite + clinopyroxene (endiopside- augite) ± sanidine ± quartz ± opaque minerals. Balıkesir Volcanites present distinct textural properties such as rounded plagioclase phenocrysts with reaction rims, oscillatory zoning, honeycomb and sieve textures in plagioclase, reverse mantled biotite and hornblende crystals. The plagioclase- amphibole geothermobarometry calculations of Balıkesir volcanites indicate that, andesite and dacite lavas present similar crystallization temperature and pressures conditions of 798- 813°C and 1,98- 2.17 kbar. Oppositely, trachyandesites were crystallized under 857°C and 3,72 kbar temperature and pressure conditions. These results show that the andesite and dacite lavas were originated from the same magma chamber with the depth of 7km whereas trachyandesites were evolved in a deeper magma chamber with 13 km depth. Combined mineral chemistry, petrography and geothermobarometry studies indicate that the open system processes such as magma mixing/mingling and/or assimilation fractional crystallization (AFC) were responsible for the textural and compositional variations of the Balıkesir Volcanites.</p>

The Tertiary Kærven Syenite Complex, Kangerdlugssuaq, East Greenland: Mineral Chemistry and Geochemistry

1988 ◽  
Vol 52 (367) ◽  
pp. 435-450 ◽  
Author(s):  
Paul Martin Holm ◽  
Niels-Ole Prægel
Keyword(s):  
Magma Mixing ◽  
Crustal Contamination ◽  
Outer Part ◽  
Alkali Feldspar ◽  
Mineral Chemistry ◽  
Crystal Fractionation ◽  
Maximum Pressure ◽  
General Sequence ◽  
East Greenland ◽  
Rock Suite

AbstractThe Kærven syenite complex, which reflects the hitherto earliest recorded stages in the Tertiary of East Greenland, outcrops in the middle reaches of the Kangerdlugssuaq Fjord as a peripheral intrusion to the Kangerdlugssuaq intrusion. The rocks of the Kærven complex range from syenite through alkali feldspar quartz-syenite to alkali feldspar granite. The general sequence of crystallization of the Kærven magmas was: alkali feldspar ± olivine(Fa96−99) ± plagioclase(An41−11), clinopyroxene (augite, ferrosalite, ferrohedenbergite), quartz and amphibole. Whole-rock major and trace-element data show coherent geochemical trends which suggest comagmatism. The data reveal that the Kærven rocks are distinct from the rocks from the adjacent Kangerdlugssuaq intrusion (e.g. higher TiO2, FeOT in low-SiO2 samples, lower Na2O, approx. constant Zr/Nb). The mineral chemistry supports this conclusion, as the Kærven samples typically have calcic amphiboles and clinopyroxenes with a very limited Na-enrichment in contrast to the sodic trends of the Kangerdlugssuaq intrusion. Normative feldspar compositions plot near to the Ab-Or cotectic in the Q-Ab-Or system and a maximum pressure of crystallization of 3–5 kbar with moderate to low PH2O is indicated.Trace elements preferently incorporated in plagioclase and alkali feldspar, i.e. Sr, Ba and Rb, show systematics which are not compatible with an evolution of the rock suite by crystal fractionation of these phases, though possibly alkali feldspar may be partially accumulated in a few very evolved rocks. Numerical calculations do not suggest a magmatic evolution by fractional crystallization of the observed phases. The variation of Sr, Ba and Rb as well as of the incompatible elements Nb, Zr and Th support a derivation of the rock suite mainly by mixing two components, a syenitic and a granitic end-member. It is concluded that magma mixing was the most significant process in the formation of the Kærven rock suite accompanied by some crystal fractionation. Evidence for crustal contamination is detected in a few samples from the outer part of the intrusion but has not affected the main suite of rocks.

Primitive intratransform volcanism at Garrett Transform Fault (East Pacific Rise)

1997 ◽  
Vol 34 (8) ◽  
pp. 1101-1117 ◽  
Author(s):  
R. Hébert ◽  
R. Hekinian ◽  
D. Bideau
Keyword(s):  
Magma Mixing ◽  
East Pacific Rise ◽  
Source Region ◽  
Mineral Chemistry ◽  
Oscillatory Zoning ◽  
Chromian Spinel ◽  
Transform Fault ◽  
East Pacific ◽  
Simply Connected ◽  
Ocean Ridge

The paper presents the results of a petrological study of samples collected by submersible from volcanic features that floor the intratransform domain of the Garrett Transform Fault. Most intratransform volcanics are typically highly porphyritic and primitive mid-ocean ridge basalt (MORB) (glasses have Mg# higher than 0.65), whereas most volcanics close to the East Pacific Rise – transform intersection zone are nearly aphyric evolved MORB (glasses have Mg# lower than 0.54). In the intratransform volcanics, phenocrysts and megacrysts are plagioclase and olivine and accessory spinel microphenocrysts in the magnesian lavas, and clinopyroxene and plagioclase in ferrobasalts. Variable mineral chemistry of plagioclase and spinel, chemical disequilibria between these phases and surrounding glass, and resorption features and oscillatory zoning in plagioclase suggest that limited magma mixing occurred during genesis of intratransform MORB. Aluminous- to chromian-spinel compositions are in agreement with melt interactions in small magma pockets. These processes are superimposed on complex partial melting events of a heterogeneous source region underlying the intratransform domain. Generation of most ferrobasalts can be explained by crystal fractionation of primitive MORB. Some ferrobasalts appear to derive from discrete magma bodies, since they are not simply connected to the magnesian tholeiites through fractional crystallization processes.

scholarly journals MAGMA GENERATION AND MIXING IN THE EARLIEST VOLCANIC CENTRE OF SANTORINI (AKROTIRI PENINSULA). MINERAL CHEMISTRY EVIDENCE FROM THE AKROTIRI PYROCLASTICS

2017 ◽  
Vol 43 (5) ◽  
pp. 2625
Author(s):  
K. Kitsopoulos
Keyword(s):  
Magma Mixing ◽  
Mineral Chemistry ◽  
Silicic Magma ◽  
High Alumina ◽  
Primitive Mantle ◽  
Volcanic Centre ◽  
Magma Generation ◽  
High Alumina Basalt ◽  
Ti Oxides

Santorini is a dominant expression of magma generation and subsequent volcanism in the Meditereanean area, where a calk-alkaline, high-alumina, basalt-andesite-dacite type of volcanism was expressed from eight centres. The volcanics of the Akrotiri peninsula are considered to be the products of the earliest (Pliocene Pleistocene) volcanic centre. The present study has investigated the mineral chemistry of some major pyrogenic phenocrysts, such as plagioclase and Fe-Ti oxides, of the Akrotiri pyroclatics unit, which have undergone a notable zeolitization procedure. The results are compatible with magma mixing mechanism of a primitive mantle derived, saturated, of mafic composition component with silicic magma in shallow crustal depths.

Evolution to broadband via optical ISDN

1989 ◽  
Vol 329 (1603) ◽  
pp. 57-60
Keyword(s):  
Wavelength Division Multiplexing ◽  
Access Network ◽  
Single Mode ◽  
Cost Effective ◽  
Distributed Networks ◽  
High Definition ◽  
Wavelength Division ◽  
High Definition Television ◽  
Local Access ◽  
Recent Developments

A comprehensive broadband information network has been the goal of many Telecom operators worldwide. It is likely that such target networks will be single mode and will use time- and wavelength-division multiplexing and eventually coherent technologies to carry all services (including high-definition television). At issue is whether fibring of the local-access network can proceed by direct installation of such comprehensive target systems in the 1990s, or whether fibre solutions could first become cost-effective for current narrowband services and then gracefully evolve to broadband services. Regarding the technologies, there is more familiarity with star networks involving one or two fibres to each customer. In this paper, recent developments in the use of passive distributed networks are described, and optoelectronic issues affecting the adoption of star and distributed technologies are considered against the means of achieving future broadband infrastructures.

Microstructural shear bands in mylonites dated using muscovite sub-spectra from high-definition ultra-high-vacuum (UHV) argon diffusion experiments with phengitic white mica

2020 ◽  
Author(s):  
Marnie Forster ◽  
Ruoran Nie ◽  
Sonia Yeung ◽  
Gordon Lister
Keyword(s):  
High Vacuum ◽  
Microstructural Analysis ◽  
Shear Bands ◽  
Shear Zones ◽  
White Mica ◽  
Ultra High Vacuum ◽  
High Definition ◽  
Thin Sections ◽  
History Of ◽  
Ar Geochronology

<p>With excellent outcrop, the eclogite-blueschist belt exposed in the Cycladic archipelago in the Aegean Sea, Greece, offers a spectacular natural laboratory in which to decipher the structural geology of a highly extended orogenic belt and to ascertain the history of the different fabrics and microstructures that can be observed. Using phengitic white mica we demonstrate a robust correlation of age with microstructure, once again dispelling the myth that <sup>40</sup>Ar/<sup>39</sup>Ar geochronology using this mineral, produces cooling ages alone.</p><p>Further, we show that high-definition ultra-high-vacuum (UHV) <sup>39</sup>Ar diffusion experiments using phengitic white mica routinely allow the extraction of muscovite sub-spectra in the first 10-30% of <sup>39</sup>Ar gas release during <sup>40</sup>Ar/<sup>39</sup>Ar geochronology. The muscovite sub-spectrum is distinct and separate to the main spectrum which is dominated by mixing of gas released from phengite as well as muscovite. The muscovite sub-spectra allow consistent estimates of the timing of the formation of microstructural shear bands in various mylonites, as well as allowing quantitative estimates of temperature variation with time during the cooling history of the eclogite-blueschist belt. Our new data reveals hitherto unsuspected variation in the timing of exhumation of individual slices of the eclogite-blueschist belt, caused by Eocene and Miocene detachment-related shear zones.</p><p>This study thus illustrates a new method for the quantitative determination of the timing of movement in mylonites and/or in strongly stretched metamorphic tectonites. Shear bands formed in such structures are rarely coarsely crystalline enough to allow mineral grains that can be individually dated using laser spot analysis. Where phengitic white mica is involved, interlaying is usually so fine as to preclude the application of laser methods. In any case, laser methods do not have the capability of extracting exact and detailed age-temperature spectra, and can never achieve the definition of the multitudinous steps of the age spectrum evident from our high-definition UHV diffusion experiments.</p><p>Previous work in the Cycladic eclogite-blueschist belt has incorrectly assumed that the diffusion parameters for phengitic white mica were the same as for muscovite. Arrhenius data suggest this is not the case, and that phengitic white mica is considerably more retentive of argon than muscovite. Previous workers have also erred in dismissing microstructural variation in age as an artefact, supposedly as the result of the incorporation of excess argon. This has led to inconsistencies in interpretation, because phengite is able to retain argon at temperatures that exceed those estimated using metamorphic mineral parageneses. In consequence, we discover a robust correlation between microstructure and age, even down to the detail present in complex tectonic sequence diagrams produced during fabric and microstructural analysis of individual thin-sections.</p><p>A critical factor is that the recognition of muscovite sub-spectra requires Arrhenius data in order to recognise the steps dominated by release of <sup>39</sup>Ar from muscovite. In turn this requires precise measurement of temperature during each heating step. To apply percentage-release formula for the estimation of diffusivity, there must be a sharp rise to the temperature in question, then that temperature must be maintained at a constant value, then dropped sharply to relatively low values.</p>

The eccentric cones Monte De Fiore, Monti Rossi, Monte Spagnolo and the 2002/2003 eruption, Mt. Etna: evidence for magma mixing

2020 ◽  
Author(s):  
Moritz Bauer ◽  
Theodoros Ntaflos ◽  
Rainer Abart ◽  
Pier-Paolo Giacomoni ◽  
Carmelo Ferlito ◽  
...  
Keyword(s):  
Lava Flow ◽  
Melt Inclusions ◽  
Magma Mixing ◽  
Active Volcano ◽  
Mineral Chemistry ◽  
Geodynamic Setting ◽  
Plumbing System ◽  
Rock Composition ◽  
Mt Etna ◽  
Normal Zoning

<p>Mt. Etna is one of the most protrusive features of the eastern coastline of Sicily, Italy. As Europe’s most active volcano it has been studied extensively to reveal its geodynamic setting, plumbing system and due to the constant monitoring of the volcano edifice the prediction of the risk future events is sophisticated at Mt. Etna.</p><p>The eruptive activity has been divided according to the age into 6 stages: (1) “Tholeiitic Stage”, was active between 600-320 ka ago, (2) the “Timpe Stage” between 220 and 110 ka ago, (3) the “Ancient Alcaline Volcanism”  between 110 and 65 ka ago and (4) the “Ellittico Stage” between 57 and 15 ka ago (5) the “Mongibello Stage” from 15 ka ago until 1971 and (6) the “post -1971 Stage” active since 1971 (Casetta et al., 2019).</p><p>The lava propagating through the Etnean plumbing system generated a complex network consisting of sills and dykes responsible for the formation of the summit craters and a plethora of eccentric cones that cover the flanks of the volcano.</p><p>We studied whole rock and mineral chemistry of the lavas from three eccentric cones (Monte Spagnolo, Monte Fiori and Monte Rossi) and the 2002/2003 southern flank lava flow. All lavas are characterized by trachytic texture with variable modal composition of olivine, clinopyroxene and plagioclase phenocrysts. Euhedral and skeletal olivine phenocrysts can be distinguished into three main groups; a) normal zoning, b) inverse zoning, and c) patchy appearance with melt inclusions of andesitic and trachytic composition. The Monte Spagnolo whole rock composition has an Mg# ranging between 52-54 and 10.7 wt% CaO , being are the most primitive lavas among the sampled outcrops whereas the Monte De Fiore lavas are the most evolved since the Mg# ranges from 48.6 to 49.2 and the CaO content from 11 to 11.2 wt%. Both, Monti Rossi and the  2002/2003 lava flow are more evolved than the Monte Spagnolo since they have Mg# ~ 50 and 49-49.3 respectively. The CaO concentration in both outcrops is relatively constant ranging around 10.5 wt%.</p><p>The olivine compositions follow the same trend as their whole rocks. The most MgO-rich olivine (Fo=88.9 %) was found in the Monte Spagnolo lavas. This olivine is of magmatic origin and cannot be considered as mantle derived xenocryst since the NiO content is low (NiO=0.17 – 0.2 wt%) and the CaO-content high (CaO=0.24 – 0.26 wt%). The most evolved lavas from Monte De Fiore have the lowest Fo-content (Fo=75 - 78 %). Olivine from all samples has a characteristic inverse zonation with, at Monti Rossi and 2002/2003 lava flow, Fo-content in the core ranging from 69% to 75% and in the rim from 77% to 80% respectively.</p><p>In conclusion, the studied eccentric cones show extensive magma mixing as can be inferred from the olivine inverse zoning. Monte Spagnolo lavas represent the most primitive magma formed at high temperatures (olivine skeletal growing) and the Monte De Fiore lavas the most evolved magma.</p><p> </p><p>Casetta et al., 2019. International Geology Review, DOI: 10.1080/00206814.2019.1610979</p>

scholarly journals Evolution of the Lower Permian Rochlitz volcanic system, Eastern Germany: reconstruction of an intra-continental supereruption

2021 ◽  
Author(s):  
Marcel Hübner ◽  
Christoph Breitkreuz ◽  
Alexander Repstock ◽  
Bernhard Schulz ◽  
Anna Pietranik ◽  
...  
Keyword(s):  
Magma Mixing ◽  
Wide Spectrum ◽  
Crustal Contamination ◽  
Lacustrine Sediments ◽  
Mineral Chemistry ◽  
Lower Permian ◽  
Volcanic Complex ◽  
Volcanic System ◽  
Geochemical Composition ◽  
Eastern Germany

AbstractExtensional tectonics in the Late Paleozoic Central Europe was accompanied by rift magmatism that triggered voluminous intracontinental caldera-forming eruptions. Among these, the Lower Permian Rochlitz Volcanic System (RVS) in the North Saxon Volcanic Complex (Eastern Germany, Saxony) represents a supereruption (VEI 8, estimated volume of 1056 km3) of monotonous rhyolites followed by monotonous intermediates. Mapping, petrography, whole-rock geochemistry along with mineral chemistry and oxygen isotopes in zircon display its complex eruption history and magma evolution. Crystal-rich (> 35 vol%), rhyolitic Rochlitz-α Ignimbrite with strong to moderate welding compaction erupted in the climactic stage after reheating of the magma by basaltic injections. Due to magma mixing, low-volume trachydacitic-to-rhyolitic Rochlitz-β Ignimbrite succeeded, characterized by high Ti and Zr-values and zircon with mantle δ18O. Randomly oriented, sub-horizontally bedded fiamme, and NW–SE striking subvolcanic bodies and faults suggest pyroclastic fountaining along NW–SE-oriented fissures as the dominant eruption style. Intrusion of the Leisnig and the Grimma Laccoliths caused resurgence of the Rochlitz caldera forming several peripheral subbasins. In the post-climactic stage, these were filled with lava complexes, ignimbrites and alluvial to lacustrine sediments. Significant Nb and Ta anomalies and high Nb/Ta ratios (11.8–17.9) display a high degree of crustal contamination for the melts of the RVS. Based on homogenous petrographic and geochemical composition along with a narrow range of δ18O in zircon Rochlitz-α Ignimbrite were classified as monotonous rhyolites. For the Rochlitz-β Ignimbrites, underplating and mixing with basic melts are indicated by Mg-rich annite–siderophyllite and δ18O < 6.0 in zircon. The wide spectrum of δ18O on zircon suggests an incomplete mixing process during the formation of monotonous intermediates in the RVS.

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