The Mechanics of Multiphase Magmas: A Perspective from the Scale of Crystals and Bubbles to Magma Reservoirs

The phase separation of lipid bilayers, composed of mixtures of saturated and unsaturated lipids and cholesterol, is a topic of fundamental importance in membrane biophysics and cell biology. The formation of lipid domains, including liquid-disordered domains enriched in unsaturated lipids and liquid-ordered domains enriched in saturated lipids and cholesterol, is believed to be essential to the function of many membrane proteins. Experiment, theory, and simulation have been used to develop a general understanding of the thermodynamic driving forces underlying phase separation in ternary and quaternary lipid mixtures. However, the kinetics of early events in lipid phase separation in the presence of transmembrane proteins remain relatively understudied. Using large-scale all-atom and coarse-grained simulations, we explore the kinetics and phase separation of ternary lipid mixtures of saturated lipid, unsaturated lipid, and cholesterol in the presence of transmembrane proteins. Order parameters employed in the Cahn-Hilliard theory provide insight into the kinetics and mechanism of lipid phase separation. We observe three distinct time regimes in the phase separation process: a shorter exponential time phase, followed by a power-law phase, and then a longer plateau phase. Comparison of lipid, protein, and lipid-protein dynamics between all-atom and coarse-grained models identifies both quantitative and qualitative differences and similarities in the phase separation kinetics. Moreover, timescaling of the dynamics of the AA and CG simulations yields a similar kinetic mechanism of phase separation. The findings of this study elucidate fundamental aspects of membrane biophysics and contribute to ongoing efforts to define the role of lipid rafts in the structure and function of the cellular membrane.

The phase separation of lipid bilayers, composed of mixtures of saturated and unsaturated lipids and cholesterol, is a topic of fundamental importance in membrane biophysics and cell biology. The formation of lipid domains, including liquid-disordered domains enriched in unsaturated lipids and liquid-ordered domains enriched in saturated lipids and cholesterol is believed to be essential to the function of many membrane proteins. Experiment, theory, and simulation have been used to develop a general understanding of the thermodynamic driving forces underlying phase separation in ternary and quaternary lipid mixtures. However, the kinetics of early events in lipid phase separation in the presence of transmembrane proteins remain relatively understudied. Using large-scale all-atom and coarse-grained simulations, we explore the kinetics and phase separation of ternary lipid mixtures of saturated lipid, unsaturated lipid, and cholesterol. Order parameters employed in the Cahn-Hilliard theory provide insight into the kinetics and mechanism of lipid phase separation. We observe three distinct time regimes in the phase separation process: a shorter time exponential phase followed by a power law phase followed by a longer time plateau phase. Comparison of lipid, protein and lipid-protein dynamics between all-atom and coarse-grained models identifies both quantitative and qualitative differences and similarities in the phase separation kinetics. Moreover, timescaling of dynamics of AA and CG simulation yields a similar kinetic mechanism of phase separation. The findings of this study elucidate fundamental aspects of membrane biophysics and the ongoing efforts to define the role of lipid rafts in the structure and function of cellular membrane.

Oriented fibrous poly (butylene adipate-co-terephthalate) matrices with nanotopographic features: Production and characterization

PMMA or PEO in THF/H 2O mixture: phase diagram, separation mechanism and application

The formation, storage and chemical differentiation of magma in the Earth's crust is of fundamental importance in igneous geology and volcanology. Recent data are challenging the high-melt-fraction 'magma chamber' paradigm that has underpinned models of crustal magmatism for over a century, suggesting instead that magma is normally stored in low-melt-fraction 'mush reservoirs'1-9. A mush reservoir comprises a porous and permeable framework of closely packed crystals with melt present in the pore space1,10. However, many common features of crustal magmatism have not yet been explained by either the 'chamber' or 'mush reservoir' concepts1,11. Here we show that reactive melt flow is a critical, but hitherto neglected, process in crustal mush reservoirs, caused by buoyant melt percolating upwards through, and reacting with, the crystals10. Reactive melt flow in mush reservoirs produces the low-crystallinity, chemically differentiated (silicic) magmas that ascend to form shallower intrusions or erupt to the surface11-13. These magmas can host much older crystals, stored at low and even sub-solidus temperatures, consistent with crystal chemistry data6-9. Changes in local bulk composition caused by reactive melt flow, rather than large increases in temperature, produce the rapid increase in melt fraction that remobilizes these cool- or cold-stored crystals. Reactive flow can also produce bimodality in magma compositions sourced from mid- to lower-crustal reservoirs14,15. Trace-element profiles generated by reactive flow are similar to those observed in a well studied reservoir now exposed at the surface16. We propose that magma storage and differentiation primarily occurs by reactive melt flow in long-lived mush reservoirs, rather than by the commonly invoked process of fractional crystallization in magma chambers14.

Volcanism is the surface expression of extensive magmatic systems, with their intrusive counterpart representing ~80% of the total magma budget. Our knowledge of igneous processes therefore largely relies on our understanding of deep plutonic processes. In continental or oceanic environments, most of the intrusive igneous rocks bear geochemical cumulate signatures (e.g. depletion in incompatible elements and enrichment in compatible ones) that are commonly explained by mineral-melt segregation during differentiation. Deformation-assisted compaction aided by melt buoyancy is usually referred to as the main process involved in melt extraction. However, buoyancy alone is not sufficient, and a number of cumulative rocks are lacking any compaction evidence, opening the potential for the involvement of other processes. In addition, our view of magmatic systems has shifted in the last decades from large melt-rich bodies to crystal-rich magma reservoirs. This paradigm shift challenges some of the long-established first-order igneous concepts like the idea that melt differentiation at depth is mainly governed by (fractional) crystallization; alternatively, the presence of mush potentially favors additional processes such as melt-mush reactions. We propose a novel igneous process for the formation of igneous cumulates, consistent with the mushy nature of oceanic igneous reservoirs, their continuous/cyclic replenishment by primitive melts, and the widespread occurrence of reactive porous flow (RPF) during magma differentiation identified in a growing number of magmatic systems. The melt flush process relies on melt-mush reactions between the primitive recharge melt(s) and crystal mush. Replacement of the more evolved interstitial melt by the primitive recharge melt leading to reactions (dissolution+crystallization) and concomitant extraction of the more evolved melt from the cumulate by buoyancy participate in the acquisition of the final cumulate signature. This process relying on oceanic igneous systems considers for the first time melt inputs and not only melt extraction and matches the petrographic (e.g. mineral dissolution evidence) and geochemical constraints (trace element signatures) brought by natural oceanic samples. We tested various melt-mush reactions likely involved in the early stages of the melt flush process during RPF to investigate their thermodynamic feasibility with the Magma Chamber Simulator. First-order results show that one-step equilibration of primitive melts with primitive to moderately differentiated mush crystals triggers mineral assimilation. Together with the constraints established from the natural rock record, it strengthens the idea that RPF is a potential key process for magma differentiation in magma reservoirs at different evolution stages. The proposed melt flush process eventually adds to other processes involved in cumulate formation like magma compaction or crystal settling and is likely to apply to any other magmatic system from various settings sharing similar reservoir characteristics.

Carbonatite magmatism is a highly efficient transport mechanism from Earth’s mantle to the crust, thus providing insights into the chemistry and dynamics of the Earth’s mantle. One evolving and promising tool for tracing magma interaction are stable iron isotopes, particularly because iron isotope fractionation is controlled by oxidation state and bonding environment. Meanwhile, a large data set on iron isotope fractionation in igneous rocks exists comprising bulk rock compositions and fractionation between mineral groups. Iron isotope data from natural carbonatite rocks are extremely light and of remarkably high variability. This resembles iron isotope data from mantle xenoliths, which are characterized by a variability in δ56Fe spanning three times the range found in basalts, and by the extremely light values of some whole rock samples, reaching δ56Fe as low as -0.69 ‰ in a spinel lherzolite. Cause to this large range of variations may be metasomatic processes, involving metasomatic agents like volatile bearing high-alkaline silicate melts or carbonate melts. The expected effects of metasomatism on iron isotope fractionation vary with parameters like melt/rock-ratio, reaction time, and the nature of metasomatic agents and mineral reactions involved. An alternative or additional way to enrich light isotopes in the mantle could be multiple phases of melt extraction. To interpret the existing data sets more knowledge on iron isotope fractionation factors is needed. To investigate the behavior of iron isotopes in the carbonatite systems, kinetic and equilibration experiments in natro-carbonatite systems between immiscible silicate and carbonate melts were performed in an internally heated gas pressure vessel at intrinsic redox conditions at temperatures between 900 and 1200 °C and pressures of 0.5 and 0.7 GPa. The iron isotope compositions of coexisting silicate melt and carbonate melt were analyzed by solution MC-ICP-MS. The kinetic experiments employing a Fe-58 spiked starting material show that isotopic equilibrium is obtained after 48 hours. The experimental studies of equilibrium iron isotope fractionation between immiscible silicate and carbonate melts have shown that light isotopes are enriched in the carbonatite melt. The highest Δ56Fesil.m.-carb.melt (mean) of 0.13 ‰ was determined in a system with a strongly peralkaline silicate melt composition (ASI ≥ 0.21, Na/Al ≤ 2.7). In three systems with extremely peralkaline silicate melt compositions (ASI between 0.11 and 0.14) iron isotope fractionation could analytically not be resolved. The lowest Δ56Fesil.m.-carb.melt (mean) of 0.02 ‰ was determined in a system with an extremely peralkaline silicate melt composition (ASI ≤ 0.11 , Na/Al ≥ 6.1). The observed iron isotope fractionation is most likely governed by the redox conditions of the system. Yet, in the systems, where no fractionation occurred, structural changes induced by compositional changes possibly overrule the influence of redox conditions. This interpretation implicates, that the iron isotope system holds the potential to be useful not only for exploring redox conditions in magmatic systems, but also for discovering structural changes in a melt. In situ iron isotope analyses by femtosecond laser ablation coupled to MC-ICP-MS on magnetite and olivine grains were performed to reveal variations in iron isotope composition on the micro scale. The investigated sample is a melilitite bomb from the Salt Lake Crater group at Honolulu (Oahu, Hawaii), showing strong evidence for interaction with a carbonatite melt. While magnetite grains are rather homogeneous in their iron isotope compositions, olivine grains span a far larger range in iron isotope ratios. The variability of δ56Fe in magnetite is limited from - 0.17 ‰ (± 0.11 ‰, 2SE) to +0.08 ‰ (± 0.09 ‰, 2SE). δ56Fe in olivine range from -0.66‰ (± 0.11 ‰, 2SE) to +0.10 ‰ (± 0.13 ‰, 2SE). Olivine and magnetite grains hold different informations regarding kinetic and equilibrium fractionation due to their different Fe diffusion coefficients. The observations made in the experiments and in the in situ iron isotope analyses suggest that the extremely light iron isotope signatures found in carbonatites are generated by several steps of isotope fractionation during carbonatite genesis. These may involve equilibrium and kinetic fractionation. Since iron isotopic signatures in natural systems are generated by a combination of multiple factors (pressure, temperature, redox conditions, phase composition and structure, time scale), multi tracer approaches are needed to explain signatures found in natural rocks.

The separation of melt from crystals is a fundamental process driving the chemical differentiation of magmas and can lead to the formation of pockets of potentially eruptible magmas in highly crystallised magma reservoirs. While geochemical and geophysical evidence exists for the presence of such isolated pockets of eruptible melt, the processes that control their volume and spatial arrangement remain unclear. The Muroto sill in Japan provides an excellent opportunity to study these processes as it is perfectly exposed and shows clear evidence for melt segregation. We collected geochemical and structural data across the sill and performed thermal modelling to quantify extraction timescales and to constrain the range of crystallinity at which melt extraction occurred. Our data and calculations show that the middle–lower portion of the sill experienced melt extraction at crystal fractions between 0.65 and 0.8 over 100–150 years, until magma was too crystalline for further segregation to occur. We propose a new approach that can be used to invert measured geochemical profiles and identify the range of crystallinity at which melt extraction takes place. With this approach, the results we obtain for the Muroto sill can be generalised to magma reservoirs of different sizes and chemistries. Our calculations, and the comparison with natural magmatic systems, show that the volume of melt-rich pockets in a magma reservoir is proportional to the reservoir volume, while their spatial arrangement depends on the physiochemical properties of magmas. The results of this study increase our understanding of the factors controlling the distribution and volume of pockets of eruptible magmas in large magma reservoirs. Our calculations show that eruptible magma in dacitic and rhyolitic magma reservoirs, which are responsible for some of the largest eruptions on Earth, tend to be distributed in lenses of small volume within highly crystallised magma. Such architecture diminishes our capacity of identifying eruptible magma in large magma reservoirs such as Yellowstone using geophysical methods, and jeopardises our capacity of assessing the potential of a reservoir to feed a large eruption.

The role of H2O on the extraction of melt from crystallising magmas

Phase separation in metallic glasses

Segregative phase separation of protein/polysaccharide mixed systems: Phase separation mechanisms, characterization technologies, influencing factors, and food applications-a review.

The aim of this study was to increase understanding of the mechanism and dominant drivers influencing phase separation during ram extrusion of calcium phosphate (CaP) paste for orthopaedic applications. The liquid content of extrudate was determined, and the flow of liquid and powder phases within the syringe barrel during extrusion were observed, subject to various extrusion parameters. Increasing the initial liquid-to-powder mass ratio, LPR, (0.4–0.45), plunger rate (5–20 mm/min), and tapering the barrel exit (45°–90°) significantly reduced the extent of phase separation. Phase separation values ranged from (6.22 ± 0.69 to 18.94 ± 0.69 %). However altering needle geometry had no significant effect on phase separation. From powder tracing and liquid content determination, static zones of powder and a non-uniform liquid distribution was observed within the barrel. Measurements of extrudate and paste LPR within the barrel indicated that extrudate LPR remained constant during extrusion, while LPR of paste within the barrel decreased steadily. These observations indicate the mechanism of phase separation was located within the syringe barrel. Therefore phase separation can be attributed to either; (1) the liquid being forced downstream by an increase in pore pressure as a result of powder consolidation due to the pressure exerted by the plunger or (2) the liquid being drawn from paste within the barrel, due to suction, driven by dilation of the solids matrix at the barrel exit. Differentiating between these two mechanisms is difficult; however results obtained suggest that suction is the dominant phase separation mechanism occurring during extrusion of CaP paste.Graphical

Melt and fluid evolution in an upper-crustal magma reservoir, preserved by inclusions in juvenile clasts from the Kos Plateau Tuff, Aegean Arc, Greece

Liquid-liquid phase separation (LLPS) is a complex and subtle phenomenon whose formation and regulation take essential roles in cancer initiation, growth, progression, invasion, and metastasis. This domain holds a wealth of underutilized unstructured data that needs further excavation for potentially valuable information. Therefore, we retrospectively analyzed the global scientific knowledge in the field over the last decade by using informatics methods (such as hierarchical clustering, regression statistics, hotspot burst, and Walktrap algorithm analysis). Over the past decade, this area enjoyed a favorable development trend (Annual Growth Rate: 34.98%) and global collaboration (International Co-authorship: 27.31%). Through unsupervised hierarchical clustering based on machine learning, the global research hotspots were divided into five dominant research clusters: Cluster 1 (Effects and Mechanisms of Phase Separation in Drug Delivery), Cluster 2 (Phase Separation in Gene Expression Regulation), Cluster 3 (Phase Separation in RNA-Protein Interaction), Cluster 4 (Reference Value of Phase Separation in Neurodegenerative Diseases for Cancer Research), and Cluster 5 (Roles and Mechanisms of Phase Separation). And further time-series analysis revealed that Cluster 5 is the emerging research cluster. In addition, results from the regression curve and hotspot burst analysis point in unison to super-enhancer (a=0.5515, R2=0.6586, p=0.0044) and stress granule (a=0.8000, R2=0.6000, p=0.0085) as the most potential star molecule in this field. More interestingly, the Random-Walk-Strategy-based Walktrap algorithm further revealed that "phase separation, cancer, transcription, super-enhancer, epigenetics"(Relevance Percentage[RP]=100%, Development Percentage[DP]=29.2%), "stress granule, immunotherapy, tumor microenvironment, RNA binding protein"(RP=79.2%, DP=33.3%) and "nanoparticle, apoptosis"(RP=70.8%, DP=25.0%) are closely associated with this field, but are still under-developed and worthy of further exploration. In conclusion, this study profiled the global scientific landscape, discovered a crucial emerging research cluster, identified several pivotal research molecules, and predicted several crucial but still under-developed directions that deserve further research, providing an important reference value for subsequent basic and clinical research of phase separation in cancer.

Message in a bottle: Spontaneous phase separation of hydrous Vesuvius melt even at low decompression rates