Mushy Layer Research Articles

Pore-scale mushy layer modelling

Equations describing mushy systems, in which solid and liquid are described as a single continuum, have been extensively studied. Most studies of mushy layers have assumed them to be ‘ideal’, such that the liquid and solid were in perfect thermodynamic equilibrium. It has become possible to simulate flows of passive porous media at the pore scale, where liquid and solid are treated as separate continua. In this contribution, we study the simplest possible mushy layers at the pore scale, modelling a single straight cylindrical pore surrounded by a cylindrical annulus representing the solid matrix. Heat and solute can be exchanged at the solid–liquid boundary. We consider harmonic temperature and concentration perturbations and examine their transport rates due to advection and diffusion and the melting and solidification driven by this transport. We compare the results of this numerical model with those of a one-dimensional ideal mushy layer and with analytical solutions valid for ideal mushy layers for small temperature variations. We demonstrate that for small values of an appropriately defined Péclet number, the results of the pore-scale model agree well with ideal mushy layer theory for both transport rates and melting. As this Péclet number increases, the temperature and concentration profiles with radius within the pore differ significantly from constant, and the behaviour of the pore-scale model differs significantly from that of an ideal mushy layer. Some effects of mechanical dispersion arise naturally in our pore-scale model and are shown to be important at high Péclet number.

The impact of convection on morphological instability of a planar crystallization front

A linear morphological stability analysis of a planar solid-liquid phase interface describing the solidification processes of a binary melt with convection is carried out. The developed theory includes conductive and convective heat and mass transfer mechanisms near the phase interface and generalizes previously known theories of morphological stability. The amplification rate as a function of wavenumber of perturbations and neutral stability curve that divides the stability/instability parametric domains are obtained. It is shown that these domains are highly dependent of convection intensity, which represents a stabilizing factor for solidification processes. A criterion of concentration supercooling in the steady-state solidification conditions with convection is found. The obtained dispersion relation and neutral stability curve define various crystallization scenarios such as (i) morphological instability and concentration supercooling appearing to the formation of a two-phase mushy layer, (ii) morphological stability and concentration supercooling leading to the existence of a slurry layer, (iii) morphological stability without concentration supercooling when the planar solidification front is stable, and (iv) morphological instability without concentration supercooling forming the mesoscopically rough phase interface.

Directional Crystallization in the Presence of a Mushy Layer with Applications to the Earth’s Inner Core Boundary

We formulate the mathematical model of directional crystallization of a binary melt with a mushy layer (region) between purely solid and liquid phases. This model is complicated by melt convection and pressure-dependent phase transition temperature. Approximate analytical solutions to this nonlinear moving-boundary problem are constructed. Namely, the concentration of impurity, fraction of solid phase, mushy region thickness, average fluid velocity, primary interdendritic spacing, mean radius of a chimney, and a characteristic distance between chimneys in a mushy region are found. Using this analytical solution, we describe the mushy region structure near the inner core boundary of the Earth, which is consistent with computer simulations and estimates existing in recent literature. A scheme illustrating the mushy region arrangement with chimneys at the inner core boundary of the Earth is presented. This arrangement based on the developed theory represents the novelty and importance of our study.

Morphological/Dynamic Instability of Directional Crystallization in a Finite Domain with Intense Convection

This study is devoted to the morphological/dynamic instability analysis of directional crystallization processes in finite domains with allowance for melt convection. At first, a linear instability theory for steady-state crystallization with a planar solid/liquid interface in the presence of convection was developed. We derived and analyzed a dispersion relation showing the existence of morphological instability over a wide range of wavenumbers. This instability results from perturbations arriving at the solid/liquid interface from the cooled wall through the solid phase. Also, we showed that a planar solid/liquid interface can be unstable when it comes to dynamic perturbations with a zero wavenumber (perturbations in its steady-state velocity). A branch of stable solutions for dynamic perturbations is available too. The crystallizing system can choose one of these branches (unstable or stable) depending of the action of convection. The result of morphological and dynamic instabilities is the appearance of a two-phase (mushy) layer ahead of the planar solid/liquid interface. Therefore, our next step was to analyze the dynamic instability of steady-state crystallization with a mushy layer, which was replaced by a discontinuity interface between the purely solid and liquid phases. This analysis showed the existence of dynamic instability over a wide range of crystallization velocities. This instability appears in the solid material at the cooled wall and propagates to the discontinuity interface, mimicking the properties of a mushy layer. As this takes place, at a certain crystallization velocity, a bifurcation of solutions occurs, leading to the existence of unstable and stable crystallization branches simultaneously. In this case, the system chooses one of them depending of the effect of the convection as before. In general, the crystallizing system may be morphologically/dynamically unstable when it comes to small perturbations arriving at the phase interface due to fluctuations in the heat and mass exchange equipment (e.g., fluctuations in the freezer temperature).

A Mush-Facilitated Magma Mixing Process Revealed by Complex Zoning of Plagioclase in Mafic Magmatic Enclaves of the Early Cretaceous Sanguliu Granitic Pluton, East China

Abstract Mafic magmatic enclaves (MMEs) hosted in granitic plutons are ideal to investigate the role of mushes on magma mixing processes in crustal magma chambers. However, the petrographic evidence for mixing of magmas through infiltration and percolation in coexisting mushes and magmas is desired. Here, we describe complex zoning patterns of plagioclase in the MMEs hosted in the monzogranite of the Early Cretaceous Sanguliu pluton in East China to reveal a mush-facilitated magma mixing process. The MMEs appear as round to oval nodules about 10 to 20 cm in size and show diverse disequilibrium textures. Plagioclase in the MMEs can be identified as three populations (Plag1, Plag2, and Plag3) with distinct zoning patterns, anorthite contents (XAn) and initial Sr isotopic ratios (87Sr/86Sri). Plag1 is antecryst displaying normal zoning with An42–67 in the core and An20–36 in the mantle. The core of Plag1 shows coarse sieve texture with high-frequency oscillation in the margin, and the mantle displays resorption surface and patchy zoning. Plag2 is also antecryst with An23–66 in the core and An21–35 in the mantle. However, its core can be further recognized as Core I inside and Core II outside with distinctly different An23–43 and An44–66, respectively, showing reverse zoning. In addition, Core I contains aligned biotite inclusions and Core II shows sieve texture, resorption surface and patchy zoning. Amphibole inclusions are sporadically enclosed within Core I of Plag2 (Amp1) and mantles of Plag1 and Plag2 (Amp2), but rarely observed in Core II of Plag2. Plag3 is anhedral grain in the matrix and shows core-rim texture with An20–37 in the core. The three plagioclase populations all exhibit angular rims with resembling An9–22. Plag1 core and Plag2 Core II have (87Sr/86Sr)i (0.70920 to 0.71092) similar to the bulk (87Sr/86Sr)i of the mafic dykes intruding the Sanguliu pluton, and likely crystallized from basaltic andesitic magmas. In contrast, the rims of Plag1, Plag2, and Plag3 overall have (87Sr/86Sr)i (0.71391 to 0.71583) nearly identical to the (87Sr/86Sr)i of host monzogranite and the plagioclase in the monzogranite, likely crystallized from granitic magmas. The mantles of Plag1 and Plag2 and the core of Plag3 have (87Sr/86Sr)i (0.71141 to 0.71390) overlapping the (87Sr/86Sr)i of the MMEs, and may have crystallized from mixed melts. Calculation results based on amphibole thermobarometers show that Amp1 crystallized at ~775 °C and ~ 16 km depth, whereas Amp2 and the amphibole in the matrix of the MMEs and monzogranite crystallized at 730 to 744 °C and 8 to 9 km depth. We thus propose that the chemical and textural complexity of the three plagioclase populations in the MMEs can be attributed to that the MMEs may have come from a mushy hybrid layer that was developed through a molten granitic body being recharged by upwelling basaltic andesitic magma. Core I of Plag2 may have nucleated and grown from andesitic magma that was evolved from the basaltic andesitic magma from which the core of Plag1 and Core II of Plag2 crystallized. The two types of antecrystic plagioclase then may have experienced resorption and disequilibrium growth in the hybrid layer, and finally rimmed with ambient, evolved interstitial melt within mushy MMEs. This study shows that complex zoning patterns and compositions of plagioclase populations in the MMEs hosted in granitic plutons have important bearings on mush-facilitated magma mixing processes.

Steady-state crystallization with a mushy layer: a test of theory with experiments

Steady-state crystallization with a mushy layer: a test of theory with experiments

Towards the theory of how a constitutional supercooling layer appears ahead of the planar crystallization front

This study, the effect of constitutional supercooling appearing ahead of the crystallization front and leading to the mushy layer origination is considered. An approximate analytical theory determining the time of mushy layer initiation is constructed. Theoretical predictions are in good agreement with numerical simulations carried out in previous studies.

Precaldera Mafic Magmatism at Long Valley, California: Magma-Tectonic Siting and Incubation of the Great Rhyolite System

The iconic volcanic center at Long Valley has released ∼820 km3 of rhyolite in at least 110 eruptions. From 2.2 Ma until 0.23 Ma, products were exclusively rhyolitic, and ∼ 700 km3 were high-silica rhyolite severely depleted in Sr, Ba, and Eu. The rhyolitic interval was preceded by an interval from 3.9 to 2.6 Ma with numerous basalt-andesite-dacite eruptions accompanied by no rhyolite at all. We have now mapped the circumcaldera products of this interval, defined 107 eruptive units, characterized them all chemically and petrographically, and dated many by 40Ar/39Ar. Here we display and describe them by sector around the caldera, interpret the nature of the transcrustal magma system that eventuated in the 35-km-wide Long Valley granite-rhyolite pluton, and analyze regional tectonic factors that did or did not contribute to siting the system.Nine Miocene (12–6 Ma) eruptive units close to Long Valley were followed by a Pliocene flare-up that released >300 mafic eruptions in a SW–NE swath 170 km long, centered across the later site of Long Valley. The basalts and their fractionates are intraplate alkalic products dominated by a continental lithosphere that had long been fluxed by Mesozoic subduction. Tertiary arc volcanism had not impinged on the area of Long Valley. Volumes estimated for the 107 Neogene precaldera eruptive units (only 40 of which exceeded 0.1 km3) total ∼ 27 km3 ± 50%—only ∼3% of the subsequent volume of rhyolite erupted. Such a volume of high-silica rhyolite with ultra-low Sr and Eu is not a product of partial melting but requires as proximate parent a leucogranitic crystal mush that is itself the upper level of a long-lived plutonic reservoir that extends to the lower crust. The 27 km3 of Neogene magma that erupted was a small contingent of the mantle-derived basaltic flux needed to energize (and contribute its fractionated melt to) a 30-km-deep compositionally graded crustal column, which culminated in ∼10,000 km3 of granitoid mush from which 820 km3 of Quaternary high-silica rhyolitic melt escaped and erupted.Pliocene basaltic eruptions ceased at ∼2.6 Ma, probably because the basaltic flux intensified sufficiently to render the mushy upper crust impenetrable. The 2.6–2.2 Ma quiescent interval represented culmination of thermal activation of the plutonic column and refinement of its leucogranitic mushy upper layer, from which extreme melts escaped for the next 2 Myr. The Pliocene mafic swath crosses the Sierran rangefront fault zone coincident with a left-stepping extensional reentrant that also began developing at ∼3 Ma. Moreover, Long Valley overlies a dextral offset in the initial Sr-isotope 0.706 line, which may reflect the rifted or attenuated edge of Proterozoic crust and mantle lithosphere. Concatenation of these three influences may account for siting of intensified edge-focused magmatism that produced the great Quaternary pluton.

The role of incoming flow on crystallization of undercooled liquids with a two-phase layer

Motivated by important applications of crystallization phenomena, we consider a directional solidification process for a binary melt with a two-phase (mushy) layer in the presence of weak melt flow. We consider the steady-state solidification scenario, so that the two-phase layer filled with solid and liquid material keeps its thickness. In addition, we consider that the melt flows onto the two-phase layer slowly in the opposite direction to directional crystallization and solidifies there. A complete analytical solution to non-linear two-phase layer equations is constructed in a parametric form, where the solid phase fraction represents a decision variable. The temperature and solute concentration distributions, mushy layer permeability and average interdendritic spacing as well as solidification velocity and mushy layer thickness are analytically determined. We show that incoming melt flow plays a decisive role on mushy layer parameters and internal structures. The solid phase fraction within the two-phase layer and its thickness essentially grow while the mushy layer permeability and average interdendritic spacing decrease with increasing intensity of incoming melt flow.

Exact analytical solutions of a steady-state mushy layer model containing heat exchange with the environment

Exact analytical solutions of a steady-state mushy layer model containing heat exchange with the environment

A Hybrid Mechanism for Enhanced Core‐Mantle Boundary Chemical Interaction

AbstractDetection of chemical signatures from the core‐mantle boundary (CMB) could provide an unprecedented glimpse into our planet's deep interior and ancient past. Several isotopic and elemental anomalies in ocean island basalts (OIBs) have been proposed as core tracers. However, the process(es) by which particular chemical signatures from the core are conveyed into the mantle remain uncertain. Here, we propose a hybrid mechanism that results from a collaborative feedback between dynamic topography, porous infiltration of liquid metal into submerged rock, gravitational collapse of weakened metal‐silicate mush, and draw‐down of additional rocks from above in the induced small‐scale mantle circulation. Using a mantle convection model coupled to gravitational spreading of a thin layer, we show that induced mantle circulation due to the gravitational collapse of the layer becomes comparable to buoyancy‐driven mantle flow when the viscosity of the mushy layer is reduced to values ∼105 times smaller than the overlying mantle.

Mathematical modeling of bulk and directional crystallization with the moving phase transition layer

This paper is devoted to the mathematical modeling of a combined effect of directional and bulk crystallization in a phase transition layer with allowance for nucleation and evolution of newly born particles. We consider two models with and without fluctuations in crystal growth velocities, which are analytically solved using the saddle‐point technique. The particle‐size distribution function, solid‐phase fraction in a supercooled two‐phase layer, its thickness and permeability, solidification velocity, and desupercooling kinetics are defined. This solution enables us to characterize the mushy layer composition. We show that the region adjacent to the liquid phase is almost free of crystals and has a constant temperature gradient. Crystals undergo intense growth leading to fast mushy layer desupercooling in the middle of a two‐phase region. The mushy region adjacent to the solid material is filled with the growing solid‐phase structures and is almost desupercooled.

Верифікація математичної моделі для розв’язання задачі Стефана в рамках методу “mushy layer”

The use of solar energy has limitations due to its periodic availability: solar plants do not operate at night and are ineffective in dull weather. The solution of this problem involves the introduction of energy storage and duplication systems into the conversion loop. Among the energy storage systems, solid–liquid phase transition modules have significant energy, ecologic, and cost advantages. Physical processes in modules of this type are described by a system of non-stationary nonlinear partial differential equations with specific boundary conditions at the phase interface. The verification of a method for solving the Stefan problem for a heat-storage material is presented in this paper. The use of the mushy layer method made it possible to simplify the classical mathematical model of the Stefan problem by reducing it to a nonstationary heat conduction problem with an implicit heat source that takes into account the latent heat of transition. The phase transition is considered to occur in an intermediate zone determined by the solidus and liquidus temperatures rather than in in infinite region. To develop a Python code, use was made of an implicit computational scheme in which the solidus and liquidus temperatures remain constant and are determined in the course of numerical experiments. The physical model chosen for computer simulation and algorithm verification is the process of ice layer formation on a water surface at a constant ambient temperature. The numerical results obtained allow one to determine the temperature fields in the solid and the liquid phase and the position of the phase interface and calculate its advance speed. The algorithm developed was verified by analyzing the classical analytical solution of the Stefan problem for the one-dimensional case at a constant advance speed of the phase interface. The value of the verification coefficient was determined from a numerical solution of a nonlinear equation with the use of special built-in Python functions. Substituting the data for the physical model under consideration into the analytical solution and comparing them with the numerical simulation data obtained with the use of the mushy layer method shows that the results are in close agreement, thus demonstrating the correctness of the computer algorithm developed. These studies will allow one to adapt the Python code developed on the basis of the mushy layer method to the calculation of heat storage systems with a solid-liquid phase transition with account for the features of their geometry, the temperature level, and actual boundary conditions.

Convection in a mushy layer along a vertical heated wall

Motivated by the mushy zones of sea ice, volcanoes and icy moons of the outer solar system, we perform a theoretical and numerical study of boundary-layer convection along a vertical heated wall in a bounded ideal mushy region. The mush is comprised of a porous and reactive binary alloy with a mixture of saline liquid in a solid matrix, and is studied in the near-eutectic approximation. Here, we demonstrate the existence of four regions and study their behaviour asymptotically. Starting from the bottom of the wall, the four regions are (i) an isotropic corner region; (ii) a buoyancy dominated vertical boundary layer; (iii) an isotropic connection region; and (iv) a horizontal boundary layer at the top boundary with strong gradients of pressure and buoyancy. Scalings from numerical simulations are consistent with the theoretical predictions. Close to the heated wall, the convection in the mushy layer is similar to a rising buoyant plume abruptly stopped at the top, leading to increased pressure and temperature in the upper region, whose impact is discussed as an efficient melting mechanism.

The Stabilization of Waste Funnel Glass of CRT by SiO2 Film Coating Technique

The funnel glass of the CRT monitor contains about 22–28% of lead oxide, of which lead is a highly toxic species and hazardous to the environment. This study proposes a process to form a protective layer of SiO2 film coating on the funnel glass to reduce the hazardous effect of lead leaching to the environment. The film coating benefits from the advantages of the sol–gel method. There are two key procedures of the stabilization technique, including the alkaline treatment and the formation of SiO2 coating from TEOS. The results show that the funnel glass powder treated with 10 M NaOH can produce a mushy layer on the surface. The mushy layer, which comprises OH− and water, can promote the formation of the SiO2 film layer on the surface of funnel glass powder. The conditions of the SiO2 film coating proposed in this study are: alkaline treatment by 10 M NaOH, the addition ratio of TEOS and funnel glass powder 2: 1, reaction temperature 40 °C, and reaction time 1.3 h. The EDS and ESCA results show that the Pb peak intensity on the surface of funnel glass decreases with the film coating. In the TCLP test, the leaching amount for Pb of the SiO2 film coated funnel glass powders is 0.7 mg/L, which is far lower than the standard in Taiwan EPA. Based on the experimental results, the formation mechanism of the SiO2 film layer on the surface of waste funnel glass powder is proposed. This study demonstrates that the SiO2 film coating is a potentially effective method to solve the problem of the waste funnel glass.

Timescales of crystal mush mobilization in the Bárðarbunga-Veiðivötn volcanic system based on olivine diffusion chronometry

AbstractThe timescales of magmatic processes within a volcanic system may be variable over a volcano’s geological history. Crystals reflect environmental perturbations under which they grew, and compositional gradients quenched inside crystals on eruption can be exploited to extract timescales of magmatic processes. Here, we use multi-element diffusion chronometry in olivine macrocrysts to recover their residence time in a melt that ultimately erupted at the surface. The macrocrysts were mobilized by the carrier melt from mushy layers in the magma reservoir, and diffusion timescales likely reflect the time interval between mush disaggregation, ascent, and eruption. To unravel the evolution of mush disaggregation timescales with time, we target early-Holocene, middle-Holocene, and historical magmatic units erupted in the Bárðarbunga-Veiðivötn volcanic system in Iceland’s Eastern Volcanic Zone. Macrocryst contents vary between samples; early-Holocene samples are highly phyric (10–45 vol% macrocrysts) and contain gabbroic nodules, whereas middle-Holocene (5–15 vol%) and historical units (5–10 vol%) tend to be generally less phyric. Early-Holocene olivine macrocrysts have core compositions in the range Fo84–87, while middle-Holocene and historical samples record a wider range in core compositions from Fo80 to Fo86.5. Olivine rims are in chemical equilibrium with their carrier liquid and are slightly more evolved in early-Holocene units (Fo76–81) compared to middle-Holocene (Fo78–80) and historical (Fo81–83) units. Diffusion chronometry reveals that the timescale between mush dis-aggregation and eruption has changed over time, with timescales getting shorter approaching recent times. Early-Holocene olivine macrocrysts dominantly record Fe-Mg diffusion timescales between 200–400 days, while middle-Holocene and historical units typically record timescales of about 70 and 60 days, respectively. Barometric studies suggest that melts and crystals are likely stored and gradually transferred throughout an interconnected multi-tiered system that ultimately culminates in a mid-crustal reservoir(s) at about 6.8–7.5 ± 2.5 km depth, where final disaggregation by the carrier liquid took place. We argue that, as a result of extensional processes enhanced by rifting events, well-mixed melts got drawn into mid-crustal reservoir(s), causing crystal mush loosening and mobilization. In addition, we propose that more energy in the form of heat and/or melt supply was required in the early-Holocene to break up the dense mush fabric and convert it into an eruptible magma. Conversely, as evidenced by the diverse macrocryst content of the historical units and by the lack of gabbroic nodules, the system has become characterized by a less compact mush fabric since at least the middle-Holocene, such that fresh injection of melt would easily loosen and mobilize the mush, resulting in an eruption within a couple of months. This study provides evidence that along axial rift settings, rifting-related processes can help to “pull the mush apart” with no requirement for primitive magma injection as an eruption trigger. Furthermore, we provide evidence that in the Bárðarbunga-Veiðivötn volcanic system specifically, the time between mush disaggregation and eruption has decreased considerably with time, indicating shorter warning times before imminent eruptions.

Dynamics of a Solidifying Icy Satellite Shell

AbstractOcean worlds have been identified as high‐priority astrobiology targets due to the link between life and liquid water. Young surface terrain on many icy bodies indicates that they support active geophysical cycles that may facilitate ocean‐surface transport that could provide observables for upcoming missions. Accurately interpreting spacecraft observations requires constraining the relationship between ice shell characteristics and interior dynamics. On Earth, the composition, physical characteristics, and bioburden of ocean‐derived ices are related to their formation history and parent fluid composition. In such systems, the ice–ocean interface, which exists as a multiphase mushy layer, dictates the overlying ice’s properties and evolution. Inclusion of the physics governing these boundaries is a novel strategy in modeling planetary ices and thus far has been limited to 1D approaches. Here, we present results from 2D simulations of an archetypal ice–ocean world. We track the evolution of temperature, salinity, porosity, and brine velocity within a thickening ice shell enabling us to place improved constraints on ice–ocean world properties, including the composition of planetary ice shells, the thickness and hydraulic connectivity of ice–ocean interfaces, and heterogeneous dynamics/structures in the interfacial mushy layer. We show that stable eutectic horizons are likely a common feature of ice–ocean worlds and that ocean composition plays an important role in governing the structure and dynamics of the interface, including the formation of chemical gradient‐rich regions within the mushy layer. We discuss the geophysical and astrobiological implications of our results and highlight how they can be validated by instrument‐specific measurements.

Insights into the kinetic processes of solute migration by unidirectional freezing in porous media with micromodel visualization at the pore-scale

Field investigations have proved that frozen soil does not act as a completely impermeable barrier for contaminants in cold regions. However, the subsurface behaviors of solutes in freezing and frozen porous media are still unclear. To unveil their nature, the pore-scale behavior of potassium permanganate in saturated porous media subjected to the unidirectional freezing was investigated using micromodel visualizations. An optical microscope was applied to obtain the pore-scale kinetics of solute redistribution in a two-dimensional micromodel using a calibration curve between the color intensity and concentration. We found that (1) the solute migration was not only limited to the ice-water interface but also occurred in the freezing area; (2) the redistribution of solutes had a significant hysteresis effect relative to the freezing front movement during the freezing of the porous media. By combining these results with the theory of sea ice, we suggested that the formation and re-motion of solute-rich inclusions in the mushy layer appear to be vital processes responsible for these phenomena. It was believed that the major mechanism for the re-motion of liquid inclusions was brine diffusion and expulsion in this experiment. The results of this study provide a better understanding of the physics of contaminant migration and their complex kinetics at the pore scale, which has important implications for the assessment and remediation of contaminated soils in seasonal frozen soils and permafrost.

Colloidal mushy layers

Abstract

Binary alloy solidification and freckle formation: Effect of shrinkage induced flow on solutal instability and macro-segregation

Freckle formation during directional solidification of binary alloy is a well-researched subject area. However, the influence of shrinkage induced flow (SIF) on freckling phenomena is barely reported. The focus of this work is to investigate this effect during bottom-up solidification of binary alloys. A fixed grid-based numerical scheme involving volume averaging of conserved parameters is proposed. The solidification geometry under consideration is a two-dimensional mold cavity with a central riser allowing continuous melt flow into the cavity. Model validation is obtained against existing numerical results involving directional solidification of Al-4.1 wt. % Cu alloy. However, heavier solute (Cu) rejection in the melt during solidification renders the validation case study devoid of freckling phenomena. The postvalidation investigations involve bottom up solidification of Al-30 wt. % Mg alloy with lighter solute (Mg) rejection, leading to solutal instability and freckle formation. The effect of SIF on solutal instability, channel formation, and overall macro-segregation is investigated. The intensity of SIF hinges on both cooling condition and opening size. The penetration depth of SIF into the solidification domain gives rise to either early or late onset of solutal instability. SIF penetration depth till the melt domain adjacent to the mushy layer promotes early onset of solutal instability. However, SIF penetration into the mushy layer itself triggers redistribution of solute-rich melt inside this layer, leading to delayed onset of solutal instability. Since the macro-segregation is a direct consequence of advection of solute inside and adjacent to the mushy region, the influence of SIF is manifested by unprecedented macro-segregation pattern.