Saswata Hier-Majumder

Saswata Hier-Majumder
Royal Holloway, University of London | RHUL · Department of Earth Sciences

PhD

About

79
Publications
6,629
Reads
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1,016
Citations
Additional affiliations
October 2013 - present
Royal Holloway, University of London
Position
  • Professor (Associate)
July 2006 - June 2014
University of Maryland, College Park
Position
  • Professor (Assistant)
September 2004 - May 2006
Yale University
Position
  • PostDoc Position

Publications

Publications (79)
Article
Full-text available
A seismic low velocity layer (LVL) above the mantle transition zone (MTZ), often thought to be caused by volatile-induced melting, can significantly modulate planetary volatile cycles. In this work, we show that an LVL observed beneath northeast Asia is characterized by small, 0.8{plus minus}0.5 vol%, average degrees of partial melting. Seismically...
Conference Paper
Full-text available
Today’s energy challenges often require geologists from operators and/or regulators to revisit legacy core to use as analogues for new sites or new processes, for example subsurface storage. Compared with the cost of drilling boreholes to acquire new core, the cost of new analysis on these cores is small. Technological developments also allow for t...
Article
Full-text available
The growing importance of subsurface carbon storage for tackling anthropogenic carbon emissions requires new ideas to improve the rate and cost of carbon capture and storage (CCS) project development and implementation. We assess sandstones from the UK Geoenergy Observatories (UKGEOS) site in Glasgow, UK and the Wilmslow Sandstone Formation (WSF) i...
Article
Full-text available
We study carbon capture and sequestration (CCS) over time scales of 2000 years by implementing a numerical model of reactive infiltration instability (RII) caused by reactive porous flow. Our model focuses on the mineralization of CO2 dissolved in the pore water---the geological carbon sequestration (GCS) phase of a CCS operation---starting 10--100...
Article
Full-text available
Early in the history of the solar system, planetesimals were differentiated into metallic cores. In some planetesimals, this differentiation took place by percolation of the denser core forming liquid through a lighter solid silicate matrix. A key factor in core formation by percolation is the establishment of a connection threshold of the melt. In...
Article
Full-text available
In this work, we apply digital rock physics (DRP) to characterize the pore networks of the Brae Formation sandstones from two different wells in the Miller field area (North Sea, UK). Using X-ray micro-CT scans, we calculate the porosity and permeability and generate pore network models to assess pore shape characteristics. The porous samples are m...
Article
Full-text available
During deposition and subsequent diagenesis, reservoir rocks develop sediment texture and cement phases are formed during the precipitation of secondary minerals such as microcrystalline quartz, calcite and clay fibrous over-growths that contain secondary porosity. The grain size distribution and presence of secondary microporous material can influ...
Article
In this article, we propose a new inversion scheme to calculate the melt volume fractions from observed seismic anomalies in a low-velocity layer (LVL) located atop the mantle transition zone. Our method identifies the trade-offs in the seismic signature caused by temperature, solid composition, melt volume fraction, and dihedral angle at the solid...
Poster
Full-text available
Geological carbon storage (GCS) has been identified as a crucial process in tackling rising anthropogenic CO2 emissions. We examine 4 sandstone cores from the Scottish Middle Coal Measures Formation at the UK Geoenergy Observatories (UKGEOS) site in Glasgow using X-ray micro computed tomographic images to assess the carbon storage capacity. Each 3D...
Poster
Core imaging and classification is an important step for generating a digital database for subsurface geology. The British Geological Survey collection contains cores from over 15,000 onshore and 8,000 offshore boreholes. Many cores are photographed at high-resolution creating an archive of over 100,000 core tray images containing between 1 m and 3...
Poster
Full-text available
Carbon capture and storage (CCS) has been identified as an area of research interest due to its potential for reducing the global greenhouse effect. CCS typically involves injection of supercritical CO2 into abandoned oil and gas reservoirs or saline aquifers with sufficient porosity and permeability. CO2 is trapped by a number of mechanisms which...
Conference Paper
Full-text available
Carbon capture and storage (CCS) has been identified as an area of research interest due to its potential for reducing the global greenhouse effect. CCS typically involves injection of supercritical CO2 into abandoned oil and gas reservoirs or saline aquifers with sufficient porosity and permeability. CO2 is trapped by a number of mechanisms which...
Conference Paper
Core imaging and classification is an important step for generating a digital database for subsurface geology. The British Geological Survey collection contains cores from over 15,000 onshore and 8,000 offshore boreholes. Many cores are photographed at high-resolution creating an archive of over 100,000 core tray images containing between 1 m and 3...
Article
Full-text available
We present a theoretical model of the stability and migration of carbonate-rich melts to test whether they can explain seismic low-velocity layers (LVLs) observed above stalled slabs in several convergent tectonic settings. The LVLs, located atop the mantle transition zone, contain small (∼1 vol%) amounts of partial melt, possibly derived from melt...
Article
Full-text available
We investigate the pore network geometry and permeability of six natural sandstones and carbonate rocks. Using 3D microtomographic images, we segment each rock sample into three phases: Solid matrix of grains, macropores containing void spaces, and a third microporous phase containing nanometer-sized pores beyond the resolution of the image. In the...
Article
This article presents a framework for building analytical solutions for coupled flow in two interacting multiphase domains. The coupled system consists of a multiphase sphere embedded in a multiphase substrate. Each of these domains consists of an interconnected, load-bearing, creeping matrix phase and an inviscid, interstitial fluid phase. This ar...
Article
Full-text available
We report the results of pore-network analysis of high resolution synchrotron microtomographic images of Fontainebleau and Berea Sandstones. We segment the gray-scale images of the rocks into constituent phases, and analyze the geometry of the pore network. The network consists of pores situated at the corner of grains and serve as the junction bet...
Conference Paper
Full-text available
We propose a new methodology based on Ps receiver functions to constrain anelasticity in thin seismically attenuating layers. At low incidence angle and due to partitioning of seismic energy, the effect of anelasticity is to increase the amplitude of the seismic pulse converted at the top of the attenuating layer, and to decrease the amplitude of t...
Code
This publication contains a maple script and Python codes for visualization of analytical solutions for coupled two-phase flow within a sphere embedded in a substrate.
Code
MuMaP_fwd is a python library for forward modeling elastic properties of partially molten rocks. The current version includes a physical properties of a number of different MORB and peridotite melts and several different models of melt geometry. Use the wiki pages on Git Hub (https://github.com/sashgeophysics/MuMap_fwd-1.0/wiki) for quick start gui...
Code
What is this repository for? This repository contains scilab files and data for a numerical modelof magma ocean crystallization How do I get set up? To run the simulations, you will need scilab installed in your computer. The file hmh.sce is the central file for creating data. It’s major dependency is on module.sce. To generate figures, run post_pr...
Article
The Earth's deep interior contains significant reservoirs of volatiles such as H, C, and N. Due to the incompatible nature of these volatile species, it has been difficult to reconcile their storage in the residual mantle immediately following crystallization of the terrestrial magma ocean (MO). As the magma ocean freezes, it is commonly assumed, v...
Article
We report from converted seismic waves, a pervasive seismically anomalous layer above the transition zone beneath the western US. The layer, characterized by an average shear wave speed reduction of 1.6%, spans over an area of ∼1.8×106 km2∼1.8×106 km2 with thicknesses varying between 25 and 70 km. The location of the layer correlates with the prese...
Article
Seismic observations reveal a patchwork of thin and dense structures, named UltraLow Velocity Zones (ULVZs) atop the Earth's core mantle boundary. The high width to height ratio of the ULVZs, their spatial correlation with the edges of Large Low Shear Velocity Provinces (LLSVPs), and their preservation as distinct structures in the convecting mantl...
Article
In this article, we calculate the seismic anisotropy resulting from melt redistribution during pure and simple shear deformation. Deformation strongly modifies the geometry of melts initially occupying three grain junctions. The initially isotropic fractional area of intergranular contact, contiguity, becomes anisotropic due to deformation. Consequ...
Article
The microstructure of partially molten rocks strongly influences the macroscopic physical properties. Contiguity, a geometric parameter, is a tensorial quantity that describes the area fraction of intergranular contact in a partially molten aggregate. It is also a key parameter that controls the effective elastic strength of the grain network. As t...
Article
Full-text available
The low-viscosity layer in the upper mantle, the asthenosphere, is a requirement for plate tectonics. The seismic low velocities and the high electrical conductivities of the asthenosphere are attributed either to subsolidus, water-related defects in olivine minerals or to a few volume per cent of partial melt, but these two interpretations have tw...
Article
We develop a dynamic model of the effect of incomplete melt/crystal separation on the partitioning of volatiles between magma oceans and overlying atmospheres.
Article
[1] We report a new technique to describe seismic velocity and impedance anomalies atop a seismic Low Velocity Layer (LVL) at 350 km depth. We model shear wave speed reductions detected with Ps conversions beneath the Hawaiian Islands and negative impedance contrasts detected with ScS reverberations beneath the Coral Sea in the South Pacific, by va...
Article
We investigates the melt distribution and resultant seismic signature within UltraLow Velocity Zones (ULVZs) forced by pulsed compaction at the mantle-ULVZ interface. Transient flow in the ambient mantle causes periodic compaction in the ULVZ matrix. For a neutrally buoyant melt, an initially uniform melt distribution is modified by the formation o...
Article
We present a study of coupled thermal and structural evolution of Neptune's moon, Triton, driven by tidal dissipation and radiogenic heating. Triton's orbital history likely involves capture from a binary system by Neptune, followed by a period of circularization. This work investigates Triton's evolution past its circularization. We examine the ra...
Article
Full-text available
This article presents a three-dimensional microgeodynamic model of grain-melt geometry in partially molten rocks. The isotropic unit cell of the partially molten rock is characterized by a face-centered-cubic symmetry, consisting of rhombic dodecahedral grains. The variation of surface tension between grain-grain and grain-melt contacts excites a c...
Article
Earth's early history is marked by a giant impact with a Mars-sized object which lead to the formation of the moon. This impact event likely led to a substantial amount of melting of the Earth's interior. Subsequent cooling of the Earth involved extensive crystallization in this "magma ocean" over a relatively short period of time. While chemical e...
Article
We discuss the efficiency of buoyancy-driven melt extraction in relation to the low velocity layer (LVL), atop the transition zone, and the ultralow velocity zones (ULVZ), atop the core mantle boundary. The LVL is characterized by a relatively large thickness, globally varying on the order of 30-90 km. It is inferred that the LVL is characterized b...
Article
This article explores the combined effect of thermal, chemical, and melting anomalies of seismic velocities above the transition zone. While thermal and chemical effects influence the seismic velocities at subsolidus temperatures, the velocity structures are greatly modified in the presence of partial melting. We model the impedance contrast atop a...
Article
Static annealing experiments were conducted on fine-grained samples of a partially molten, olivine-rich rock to explore the role of interfacial tension driven flow in redistributing melt within the sample. A sample of fine-grained olivine +20% chromite was prepared with an initially homogeneously distributed melt fraction of 0.04. When this sample...
Article
This paper investigates the development of anisotropic frictional resistance and mobility as a function of an applied stress in a partially molten aggregate. Shapes of initially spherical melt pockets and cylindrical melt tubules are calculated as a function of the applied stress using a perturbation analysis. The applied stress excites a local flo...
Article
The microstructure of a partially molten aggregate, determined by melt volume fraction and contiguity, the fractional area of intergranular contact, influences various physical properties of a grain-melt system ( such as the effective elastic moduli and seismic velocities). Interaction with neighboring grains perturb the shape of the grain, affecti...
Article
This article reports on the way dihedral angle and the deformation of grains in partially molten rocks impact contiguity. Dihedral angles can vary based on composition of melt. Deformation of grains can arise due to the stresses associated with motion due to tectonics or mantle convection. The results of our numerical experiments indicate that an i...
Article
Seismic body waves provide a wealth of information on the internal structure of the Earth. On their path from the source to receiver, the waves encounter a variety of environmental features, such as variation temperature, rocks of different composition, and melting. While the influence of each of these parameters on the seismic wave have been studi...
Article
The topography of Ultralow-Velocity Zones (ULVZ), located on the mantle side of the core-mantle boundary, varies between 5 and 40km. This variation in topography is influenced by multiple factors, such as density contrast between the ULVZ and mantle and micro-scale grain interaction (capillary tension) within the layer. Convection in the overlying...
Article
Earth is unique among the terrestrial planets in our solar system because it has plate tectonics and abundant surface water. It has long been suggested that these two salient features are intimately related. New constraints on water concentrations in the Earth’s interior and on mechanisms for mantle degassing and regassing have improved our knowled...
Article
Earth's core–mantle boundary is home to a patchwork collection of thin ultralow-velocity zones (ULVZ) on the mantle side of the boundary. Core-diffracted and reflected seismic waves indicate that ULVZ patches display a strong topographic variability. We model the circulation within the ULVZ, excited by sweeping motion in the lower mantle. Our resul...
Article
This article reports the influence of dihedral angle in a partially molten aggregate on its effective elastic properties using theoretical techniques. For a given mineral assemblage, dihedral angles can vary widely depending on the composition of the melt. Our results indicate that wetting melts with low dihedral angles have a lower fraction of int...
Article
Full-text available
1] Li isotopes may be useful tracers of fluid flow in a number of geological environments and case studies of contact aureoles have highlighted the very large Li isotopic fractionation that can be generated in these settings. However, the amount of isotopic fractionation and the distance that Li travels into the country rocks vary greatly from plac...
Article
Effective elastic moduli of partially molten rocks depend strongly on the melt geometry. The fractional area of intergranular contact, contiguity, determines the load-bearing strength of the structure and controls the effective elastic moduli. Contiguity of a partially molten aggregate, in turn, is sensitive to a number of parameters. Traditionally...
Article
Given the incredible resolution of upper mantle velocity structure enabled by the Earthscope transportable array, it becomes worthwhile to examine what it means in terms of mantle temperature, composition, and degree of melting. To do so, we will add complimentary data such as surface heat flow measurements to consider how observed velocities vary...
Article
This work explores the coupled structural, thermal, and orbital evolution of Neptune's icy satellite, Triton. Recent geyser activity, ridge formation, and volatile transport, observed on Triton's surface, indicate possible activity within Triton's interior [1,2]. Triton is hypothesized to have been captured from an initially heliocentric orbit. Dur...
Article
We present an extended formulation for the interfacial tension driven melt migration by taking into account dissolution/precipitation and diffusive matter transport through the liquid phase. Our results indicate that the melt migration is caused by two mechanisms. In the first mechanism, a change in melt fraction is accommodated by compaction/decom...
Article
Full-text available
1] The microstructure of partially molten rocks plays a key role in determining their physical properties. The area fraction of intergranular contact, contiguity, governs the establishment of a skeletal framework of solid grains and controls the effective elastic moduli of the aggregate. This work presents a theoretical calculation of steady state...
Article
This presentation outlines a Boundary Integral Method (BIM) to calculate particle shapes and boundary velocities in an aggregate of viscous particles concentrated in a melt of a different viscosity. Interaction among the particles is controlled by midrange forces and the velocity fields of the neighboring particles. The calculated grain shapes are...
Article
The ULVZ at the core-mantle boundary is characterized by a complex, three dimensional structure. ScP wave data from events near the Tonga-Fiji region displays a laterally variable topography of the ULVZ corresponding to shear and P wave velocity reductions of 10-30% and and 0-10%, respectively. A laterally varying density structure, leading up to a...
Article
During magma migration, both interfacial tension and mass exchange between the matrix and the melt play an important role in controlling the efficiency and rate of melt extraction and the chemical signature of the magma. In this work, we develop a new formulation governing the dynamics of a two-phase aggregate coupling effects of interfacial tensio...
Article
Physical properties of partially molten aggregates depend strongly on the volume fraction and geometry of the melt. At melt fractions higher than the `disaggregation melt fraction', intergranular contact between matrix grains vanishes, resulting in orders of magnitude changes in transport properties such as viscosity. At melt fractions less than th...
Article
We employ a continuous theory of two-phase flow to investigate the influence of grain boundary tension on distribution and migration of melts through a viscous matrix. The ‘disaggregation melt fraction’, the volume fraction of partial melt at which grain boundaries are completely wetted, is crucial in determining the total interfacial force per uni...
Article
Full-text available
1] We report the influence of shear deformation on the microstructure of water-saturated olivine and clinopyroxene aggregates. Prior to deformation, the aqueous fluid was isolated in pockets along grain corners in the olivine-water aggregates, while it was interconnected by a network of grain-edge tubules in the clinopyroxene-water aggregate. Durin...
Article
Full-text available
We employ the theory of two-phase flow to investigate the influence of grain boundary wetting during segregation of magma in a partially molten aggregate. In partially molten aggregates the `disaggregation melt fraction', the volume fraction of partial melt at which grain boundaries are completely wetted, is crucial in determining the total interfa...
Article
We employ the theory of two-phase flow to investigate the influence of grain boundary wetting during segregation of magma in a partially molten aggregate. In partially molten aggregates the `disaggregation melt fraction', the volume fraction of partial melt at which grain boundaries are completely wetted, is crucial in determining the total interfa...
Article
Full-text available
The texture development in experimentally sheared aggregates of olivine was monitored as a function of increased water content and added melt. In dry samples, an alignment of {010} with the shear plane and < 100 > and < 001 > with the shear direction, respectively, was observed, consistent with intracrystalline glide on the (010)[100] and (010)[001...
Article
Full-text available
We performed triaxial compressive creep tests to study water weakening of clinopyroxenite in the diffusion creep regime. All tests were carried out on fine-grained samples at confining pressures between 100 and 300 MPa at temperatures of 1321 to 1421 K for water-saturated and 1398 to 1508 K for anhydrous conditions. Samples were prepared by hot-pre...
Article
Full-text available
1] We report the experimental measurement of Fe-Mg interdiffusivity in olivine along the [001] crystallographic direction in a water-saturated environment at pressures of 0.1 to 6 GPa and temperatures between 1373 and 1450 K. The concentration of water-derived protons in olivine was controlled by varying the water fugacity. The oxygen fugacity was...
Article
Following the previous paper on the evolution of melt distribution in deforming partially molten rocks, here we present olivine crystallographic preferred orientation (CPO) data from the same set of experimental samples. CPO data provide relatively direct information on the mechanisms of deformation in the sample, temporally and spatially averaged....
Article
In this presentation, we review experimental determinations of the influence of oxygen environment on the physical properties of olivine. Kinetic properties of solids such as electrical conductivity and viscosity that are often functions of ionic diffusivity depend on the oxygen fugacity. Ionic diffusivity in solids can be expressed as the product...
Article
We use numerical experiments to analyze the kinetics of grain boundary wetting in polycrystalline aggregates under the influence of an external applied shear stress. Grain boundary wetting is driven by the stress concentration at the tip of the fluid front. The extent of wetting of favorably oriented grain boundaries depends on the fluid mobility n...
Article
Full-text available
Appendices: leaves 84-126. Thesis (Ph. D.)--University of Minnesota, 2004. Includes bibliographical references (leaves 127-135).
Article
We investigated water weakening of clinopyroxene aggregates, prepared by hot pressing ground powder of natural Sleaford Bay clinopyroxenite consisting of Fe bearing diopside of composition Ca0.97Mg0.78Fe0.26Si1.99O6. Wet and dry aggregates were deformed at a confining pressure of 300 MPa at temperatures between 1323-1423 K and 1398-1503 K, respecti...
Article
Deformation of fluid bearing rocks affects the distribution of pore fluids. In a large number of geologically important solid-fluid systems the fluid forms an isotropic network of tubules along grain edges at low fluid fractions. When such rocks are deformed in the laboratory at high pressures and temperatures, the fluid becomes distributed along g...
Article
In this presentation, we describe the results of deformation at high temperature and pressure on the distribution of initially isolated pockets of pore fluid in rocks of mantle compositions. Deformation of the solid matrix in a low-porosity, solid-fluid aggregate alters the distribution of the pore fluid from that stable under a hydrostatic state o...
Article
The tools to computationally model crystals settling in a magma ocean are currently not readily available. Being able to model such behavior may provide clues into the history of early Earth. New numerical simulations could lead to a better understanding of the settling. The equations that describe this settling are well understood, however, no sui...
Article
The influence of water on the creep behavior of diopside aggregates was investigated with a series of high-temperature deformation experiments. Experiments were conducted on fine-grained samples encapsulated in nickel capsules, using a Paterson gas-medium apparatus at a confining pressure of 300 MPa and temperatures of 1273 - 1473 K. Experiments we...
Article
Full-text available
This presentation reviews the mechanisms associated with efficiency of gravitational settling or rising of partial melts in the Earth's deep interior. Two specific regions of interest are the low velocity layer (LVL), atop the transition zone, and the ultralow velocity zones (ULVZ), atop the core mantle boundary. The LVL is characterized by a relat...

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Projects

Projects (4)
Archived project
Small amounts of melting in the silicate part of the Earth's deep interior exert a disproportionate influence on the physical and chemical properties of rocks. Melt is often distributed in tubes, disks, or pockets, whose dimensions are as small as the fraction of the width of a human hair. Relative abundance of these different shapes of melt units depend on both the dynamic environment of melting and chemical composition of the melts. The signature of melt geometry, an averaged description of melt distribution in these various units, is sampled by earthquake waves passing through these regions. Deciphering the signals of these earthquake waves, one can find out about the processes associated with melting in the deep Earth. In this project, we continue to develop a new theoretical toolbox, `microgeodynamics', to address the issues of detection of partial melting in the Earth?s interior and dynamics of melt storage and segregation. We will study the influence of melt volume fraction, wetting behavior, and deformation on the physical properties such as elastic moduli and melt mobility using a SemiAnalytical Model (SAM) and a Boundary Elements Model (BEM). The output of these models, dynamic melt geometry, will be processed to explain observed anomalies in various physical properties in the Earth's deep interior.
Project
Earth's continents have been assembled via amalgamation of land masses over geologic time, eventually forming stable continental interiors, with associated tectonic activity and deformation typically isolated to the periphery of the continent. Over time, successive episodes of deformation in the form of extension, compression, magmatism, accretion, and rifting have left the sub-continental upper mantle with a complex signature of thermal and chemical variability. Many ancient continental areas have been modified by relatively recent dynamic processes, for example active volcanism, rifting, and subduction at continental edges contribute to a complex sub-continental mantle. Of particular interest is the history and influence of melting, melt production, melt migration, and melt storage in sub-continental upper mantle, as it provides a window into past and present dynamical processes, including the formation of continents. This multi-disciplinary project will provide a systematic and geographically-detailed investigation of the dynamical, chemical, and thermal processes at work within the sub-continental upper mantle and their relationships to past and present melting within the Earth. The research team links a primarily undergraduate institution with a research institution and will include training of a postdoctoral researcher, undergraduate researchers through online and face-to-face research collaborations. These connections will be strengthened through long-term cross-institutional research experiences and the inclusion of a pre-service teacher working with the researchers to develop curricular activities describing Earth structure for high school and undergraduate classrooms.
Project
This project focuses on numerical modeling of the ultralow velocity zones observed at the Earth's core-mantle boundary.