Subjects -> MINES AND MINING INDUSTRY (Total: 82 journals)
 Showing 1 - 42 of 42 Journals sorted alphabetically American Mineralogist       (Followers: 16) Applied Earth Science : Transactions of the Institutions of Mining and Metallurgy       (Followers: 4) Archives of Mining Sciences       (Followers: 3) AusiMM Bulletin       (Followers: 1) BHM Berg- und Hüttenmännische Monatshefte       (Followers: 2) Canadian Mineralogist       (Followers: 7) CIM Journal       (Followers: 1) Clay Minerals       (Followers: 9) Clays and Clay Minerals       (Followers: 5) Coal Science and Technology       (Followers: 3) Contributions to Mineralogy and Petrology       (Followers: 14) Environmental Geochemistry and Health       (Followers: 3) European Journal of Mineralogy       (Followers: 14) Exploration and Mining Geology       (Followers: 3) Extractive Industries and Society       (Followers: 2) Gems & Gemology       (Followers: 2) Geology of Ore Deposits       (Followers: 5) Geomaterials       (Followers: 3) Geotechnical and Geological Engineering       (Followers: 9) Ghana Mining Journal       (Followers: 3) Gold Bulletin       (Followers: 2) Inside Mining International Journal of Coal Geology       (Followers: 4) International Journal of Coal Preparation and Utilization       (Followers: 2) International Journal of Coal Science & Technology       (Followers: 1) International Journal of Hospitality & Tourism Administration       (Followers: 16) International Journal of Mineral Processing       (Followers: 8) International Journal of Minerals, Metallurgy, and Materials       (Followers: 12) International Journal of Mining and Geo-Engineering       (Followers: 4) International Journal of Mining and Mineral Engineering       (Followers: 8) International Journal of Mining Engineering and Mineral Processing       (Followers: 6) International Journal of Mining Science and Technology       (Followers: 4) International Journal of Mining, Reclamation and Environment       (Followers: 6) International Journal of Rock Mechanics and Mining Sciences       (Followers: 9) Journal of Analytical and Numerical Methods in Mining Engineering       (Followers: 1) Journal of Applied Geophysics       (Followers: 18) Journal of Central South University       (Followers: 1) Journal of China Coal Society Journal of China University of Mining and Technology       (Followers: 1) Journal of Convention & Event Tourism       (Followers: 6) Journal of Geology and Mining Research       (Followers: 10) Journal of Human Resources in Hospitality & Tourism       (Followers: 9) Journal of Materials Research and Technology       (Followers: 2) Journal of Metamorphic Geology       (Followers: 17) Journal of Mining Institute Journal of Mining Science       (Followers: 5) Journal of Quality Assurance in Hospitality & Tourism       (Followers: 6) Journal of Sustainable Mining       (Followers: 3) Journal of the Southern African Institute of Mining and Metallurgy       (Followers: 6) Lithology and Mineral Resources       (Followers: 4) Lithos       (Followers: 11) Mine Water and the Environment       (Followers: 6) Mineral Economics       (Followers: 2) Mineral Processing and Extractive Metallurgy : Transactions of the Institutions of Mining and Metallurgy       (Followers: 14) Mineral Processing and Extractive Metallurgy Review       (Followers: 5) Mineralium Deposita       (Followers: 4) Mineralogia       (Followers: 2) Mineralogical Magazine       (Followers: 1) Mineralogy and Petrology       (Followers: 5) Minerals       (Followers: 2) Minerals & Energy - Raw Materials Report       (Followers: 1) Minerals Engineering       (Followers: 14) Mining Engineering       (Followers: 7) Mining Journal       (Followers: 4) Mining Report       (Followers: 3) Mining Technology : Transactions of the Institutions of Mining and Metallurgy       (Followers: 4) Mining, Metallurgy & Exploration Natural Resources & Engineering Natural Resources Research       (Followers: 5) Neues Jahrbuch für Mineralogie - Abhandlungen       (Followers: 1) Physics and Chemistry of Minerals       (Followers: 4) Podzemni Radovi Rangeland Journal       (Followers: 4) Réalités industrielles Rem : Revista Escola de Minas Resources Policy       (Followers: 4) Reviews in Mineralogy and Geochemistry       (Followers: 5) Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica Rock Mechanics and Rock Engineering       (Followers: 9) Rocks & Minerals       (Followers: 5) Rudarsko-geološko-naftni Zbornik Transactions of Nonferrous Metals Society of China       (Followers: 9)
Similar Journals
 Physics and Chemistry of MineralsJournal Prestige (SJR): 0.702 Citation Impact (citeScore): 2Number of Followers: 4      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1432-2021 - ISSN (Online) 0342-1791 Published by Springer-Verlag  [2653 journals]
• Structural iron in smectites with different charge locations
• Abstract: The versatile structure of smectites can exhibit large variations in chemical compositions and cationic substitutions in different crystallographic sites, resulting in various locations of layer charge. Natural smectites can contain various amounts of structural iron, the chemical form of which can influence the reactivity of these minerals. The variety of Fe crystal chemistry in smectite was explored for eight natural smectites of distinct chemical compositions and charge locations, together with two synthetic ferric saponites used as reference compounds for tetrahedral Fe(III). All samples were identified as dioctahedral or trioctahedral smectite by X-ray diffraction and Fourier-transform infrared spectroscopy. The extent of [4]Al for [4]Si substitution was determined by 27Al and 29Si magic angle spinning nuclear magnetic resonance spectroscopy. The Fe local chemical environment was probed by polarized X-ray absorption spectroscopy. Only Fe(III) could be detected in all samples, with no evidence of cluster formation. The O shell at 1.86 Å in synthetic saponites suggests Fe insertion in tetrahedral sites, and the absence of detected octahedral Fe implies quantitative substitution of [4]Fe3+ for [4]Si4+. In natural smectites, Fe(III) is bound to six O atoms at ~ 2.00 Å, suggesting insertion in octahedral sites. This inference is also supported by the detection of in-plane Mg/Al/Fe atoms at ~ 3.05 Å and out-of-plane Si/Al atoms at ~ 3.25 Å. In one Fe-rich nontronite, the detection of an O subshell at ~ 1.88 Å suggests a concomitant insertion of Fe(III) in tetrahedral sites. Low numbers of octahedral neighbors were detected in natural saponite and hectorite, presumably because of the presence of vacancies and/or Li(I) in adjacent octahedral sites balancing the local charge excess originating from the substitution of Fe(III) for Mg(II). The substitution of [4]Fe3+ for [4]Si4+ can be readily obtained under defined conditions in the laboratory, but seems more rare in natural samples, or present in amounts below the detection limit of spectroscopic methods used in this study.
PubDate: 2019-03-13
DOI: 10.1007/s00269-019-01028-y

• Thermal expansion of the Al 2 SiO 5 polymorphs, kyanite, andalusite and
sillimanite, between 10 and 1573 K determined using time-of-flight
neutron powder diffraction
• Abstract: Powder and single-crystal diffraction data measured from the three geologically important Al2SiO5 polymorphs, kyanite, andalusite and sillimanite, over the last six decades have given varying accounts of each polymorph’s thermal expansion, the scatter between and even within experimental datasets often being quite large. Furthermore, there are no lattice parameter determinations below 273 K, where the thermodynamic functions vary substantially, and few measurements above 1200 K. Accurate and precise lattice parameters of natural kyanite, andalusite and sillimanite have therefore been obtained in the range 10–1573 K using the high-resolution powder diffractometer (HRPD) at the ISIS neutron spallation source. Accuracy is ensured by the use of an internal standard (NIST silicon SRM640c) and use of a bulk probe (neutrons) to avoid the specimen-displacement corrections required by typical back-reflection X-ray diffraction methods. Precision is ensured by use of the time-of-flight method on one of the longest primary neutron flightpath instruments in the world. For kyanite, the improved precision reveals the true temperature dependence of the three inter-axial angles for the first time, permitting derivation of accurate thermal expansion tensor coefficients. For both andalusite and sillimanite, the measurements reveal hitherto unknown regions of substantial negative linear expansivity below room temperature, along the c-axis in andalusite and along the a-axis in sillimanite. Above 1200 K, sillimanite exhibits an anomalous increase in thermal expansion that may be due to a change in the Al/Si tetrahedral site ordering.
PubDate: 2019-03-11
DOI: 10.1007/s00269-019-01031-3

• Theoretical study of lithium diffusion and fractionation in forsterite and
its high-pressure phases
• Abstract: As a geochemical tracer in mantle studies, lithium isotopes play an important role in diffusion and fractionation in major mantle minerals. Olivine and its high-pressure phases, wadsleyite and ringwoodite, are considered to predominate in the upper mantle and transition zone on the earth. We carried out simulations of lithium isotopes’ diffusion and fractionation in Mg end member olivine and its high-pressure phases to learn the details of the signatures of lithium isotopes preserved in mantle materials. In this work, the diffusion and fractionation mechanisms between different lattice sites of lithium isotopes in forsterite (Mg2SiO4), wadsleyite (β-Mg2SiO4) and ringwoodite (γ-Mg2SiO4) at the atomic level are studied using empirical atomistic simulation techniques. It is found that Li can pass through the high-pressure phases (wadsleyite and ringwoodite) energetically much easier due to the low migration energy barriers via either substitutional or interstitial mechanism. The activation energy is high for Li diffusion along the interstitial path in the forsterite and decreases drastically with the assist of Mg vacancies. The temperature-dependent fractionation for two Li isotopes between two different lattice sites is calculated at the temperatures from 300 to 2500 K. This behavior generates the lighter Li storage in the near-surface mantle-derived rocks and provides insights into zoning and composition of lithium isotopes in olivine and its high-pressure phases.
PubDate: 2019-03-04
DOI: 10.1007/s00269-019-01029-x

• An infrared and Raman spectroscopic study of PbSO 4 -anglesite at high
pressures
• Abstract: Infrared and Raman spectra of the ABX4 compound anglesite (PbSO4) were collected to 43 GPa at 300 K in three separate pressure media. A major transition in the spectra initiates at 23 GPa that is characterized by shifting and/or splitting of most of the fundamental vibrations of the sulfate group. On decompression, PbSO4 reverts to the ambient anglesite (barite) structure. This transition is kinetically impeded within more hydrostatic pressure media and does not proceed to completion within a neon medium even at pressures as high as 43 GPa. The previously observed spectral shift at 13 GPa occurs in less hydrostatic media (such as 4:1 methanol:ethanol), and involves subtle splitting of a few modes, particularly the (SO4)2− tetrahedral stretching and bending-derived Raman and infrared modes. Another possible shift occurs near 33 GPa, and primarily involves the appearance of new sulfate antisymmetric bending modes in the infrared spectrum and the onset of new sulfate antisymmetric stretching modes in the Raman spectrum. It is likely that PbSO4 begins to convert sluggishly to the P212121 ABX4 structure starting at 23 GPa, with a possible additional crystallographic distortion or shift in compression mechanism occurring near 33 GPa. The spectral shift at 13 GPa in non-hydrostatic media may be a differential stress-induced structural distortion, or a subtle transition that is not accessible within more hydrostatic media. Our results emphasize that apparently equilibrium transitions such as that at 23 GPa may be notably suppressed within more hydrostatic media.
PubDate: 2019-02-22
DOI: 10.1007/s00269-019-01027-z

• Defining an aristotype crystal structure and crystallographic distortions
in leucite/pollucite-structured phases with space group $$Ia\overline {3} d$$ I a 3 ¯ d
• Abstract: A universal aristotype crystal structure for leucite/pollucite-structured phases (A2B2IIIC4IVO12, A2BIIC5IVO12) with space group $$Ia\overline {3} d$$ has been determined by a non-linear optimisation of the fractional coordinates. The resultant T-site tetrahedron exhibits close to perfect $$\overline {4} 3m$$ point group symmetry (quadratic elongation 1.0000124, tetrahedral angle variance 1.53 × 10−5 degrees2). For any distorted leucite/pollucite crystal structure, an associated aristotype phase can be derived from the optimised fractional coordinates, with the aristotype phase lattice parameter calculated from the volume of the hettotype T-site tetrahedron. Assuming the aristotype T-site tetrahedron to be ideal, the distortion of the hettotype tetrahedron from that of the aristotype is described as the linear sum of the amplitudes of an appropriate set of symmetry-adapted basis-vectors of the effective regular TO4 molecule consistent with the observed point group symmetry within the crystal structure. The methodology is illustrated by reference to the disordered T-site, leucite-structured phase K2MgSi5O12.
PubDate: 2019-02-18
DOI: 10.1007/s00269-019-01025-1

• Phase transition and thermoelastic behavior of barite-group minerals at
high-pressure and high-temperature conditions
• Abstract: Experimental studies on the phase transition and thermoelastic behavior of barite-group minerals are crucial to understand the recycle of sulfur in Earth’s interior. Here, we present a high-pressure and high-temperature (high P–T) study on two barite-group minerals—barite (BaSO4) and celestite (SrSO4) up to ~ 59.5 GPa 700 K and ~ 22.2 GPa, 700 K, respectively, using in situ synchrotron-based X-ray diffraction (XRD) combined with diamond anvil cells (DACs). Our results show that BaSO4 undergoes a pressure-induced phase transition from Pbnm to P212121 at ~ 20.3 GPa, which is different from the previous results. Upon decompression, the high-pressure phase of BaSO4 transforms back into its initial structure, which indicates a reversible phase transition. However, no phase transitions have been detected in SrSO4 over the experimental P–T range. In addition, fitting a third-order Birch–Murnaghan equation of state to the pressure–volume data yields the bulk moduli and their pressure derivatives of BaSO4 and SrSO4. Simultaneously, the thermal expansion coefficients of BaSO4 and SrSO4 are also obtained, by fitting the temperature-volume data to the Fei-type thermal equation of state. Furthermore, the compositional effects on the phase transformation and thermoelastic behavior of barite-group minerals are also discussed, and the results suggest that the bond length of < M–O > (M=Ba, Sr, Pb) is an important factor that causes the phase transition pressure of SrSO4 to be the largest, PbSO4 is the second, and BaSO4 is the lowest.
PubDate: 2019-02-09
DOI: 10.1007/s00269-019-01026-0

• Pressure-enforced Cr substitution in Cr 1+x Al 1−x O(SiO 4 ),
synthetic analogues of kyanite
• Abstract: Cr3+ can substitute for Al3+ in the crystal structure of kyanite, Al2O(SiO4). Cr3+-rich solid solutions along the binary Al2O(SiO4)–Cr2O(SiO4) joint were synthesized under distinct high-pressure conditions. Sample crystals of Cr1+xAl1−xO(SiO4) with x = 0.025(12) and 0.188(8) have been synthesized at pressures of 7 GPa and temperatures up to 1200 °C. Unit-cell dimensions and single-crystal X-ray diffraction of the new Cr3+-rich kyanite-type phases show a linear increase of lattice parameters a, b and c with increasing Cr3+ content. Cr3+ replaces Al3+ on the octahedrally coordinated M-sites with Cr3+ preferentially occupying large [MO6]-octahedra. Cr3+ substitution for Al3+ is highest on the M3 site in a sequence of Cr3+(M3) > Cr3+(M2) > Cr3+(M1) > Cr3+(M4) following the polyhedral volumes V(M3O6) > V(M2O6) > V(M1O6) > V(M4O6). The compressibility of Cr1.19Al0.81O(SiO4) has been determined via precise lattice parameters up to 6.00(4) GPa. The pressure–volume data fitted to the third-order Birch–Murnaghan equation of state yielded an isothermal bulk modulus (KT0) of 196(16) GPa and a pressure derivative K′T0 of 2(4) at V0 = 310.3(1) Å3. The value of KT0 is in accordance to the Anderson–Anderson relation but it is slightly smaller than the respective value for natural Cr3+-free kyanite.
PubDate: 2019-02-07
DOI: 10.1007/s00269-019-01024-2

• Structural investigations of neodymium incorporation in calcium stannate
perovskite CaSnO 3
• Abstract: Samples of calcium stannate perovskite (CaSnO3) doped with a variable Nd content were synthesized by solid-state reaction in the system (1 − x)CaSnO3 − xNd2O3. The synthesized compounds were characterized by means of electron microprobe, powder X-ray diffraction, single-crystal X-ray diffraction and µ-Raman spectroscopy. The incorporation of Nd in the CaSnO3Pbnm structure leads to the formation of a complex (Ca1 − 2x Nd2x)(Sn1 − xCax)O3 perovskite. The A sublattice contains a random distribution of Ca and Nd in the whole range of composition of this system. For x < 0.28, the structure is Pbnm with Ca and Sn randomly distributed in the B sublattice. For x > 0.28 a symmetry change occurs; the structure turns into rock salt type P21/n. In this latter case half of the octahedral sites are fully occupied by Sn and the other half is randomly occupied by Sn and Ca. For x = 0.28, both structures are present in the sample. The presence of a Raman two modes behavior of A1g symmetry located near 700 cm− 1 coupled with the continuous linear evolution of the lattice parameters with Nd incorporation supports the proposed substitution mechanism.
PubDate: 2019-02-01
DOI: 10.1007/s00269-018-0993-7

• Equation of state and second-order elastic constants of portlandite Ca(OH)
2 and brucite Mg(OH) 2
• Abstract: Hydroxide minerals brucite Mg(OH)2 and portlandite Ca(OH)2 (space group $$P\bar {3}m1$$ ) are very important phases for several geological and industrial applications which often require the knowledge of the mechanical properties. In the present work, the equation of state (EoS) and the second-order elastic constants of the two minerals were calculated by ab initio quantum mechanical methods. The aims are extending the knowledge of their important applicative mechanical properties and providing a consistent relative dataset. In addition, the simple crystal-chemical composition and structure of Ca(OH)2 and Mg(OH)2 is ideal to simulate and characterize the effect of the proton disorder on the elastic properties, which could be useful for the comprehension of more complex hydrous minerals and synthetic phases. The third-order Birch–Murnaghan EoS parameters obtained in the present study were V0 = 39.59(1) Å3, K0 = 48.0(9) GPa and K′ = 9.1(3), and V0 = 54.0(7) Å3, K0 = 30.1(9) GPa and K′ = 8.5(4) for Mg(OH)2 and Ca(OH)2, respectively. Axial compressibilities were found to be in ratio β(a):β(c) = 1.000:3.600 for brucite, and 1.000:3.777 for portlandite. The theoretical results agree with the general trend experimentally observed in the available literature, and further extend the knowledge of the mechanical properties of the two phases. The results could be very helpful for petro-geological investigations and for the synthesis and use of concrete nanocomposites and layered double hydroxides with tailored mechanical properties.
PubDate: 2019-02-01
DOI: 10.1007/s00269-018-0989-3

• Polarized Raman spectroscopy and lattice dynamics of
potassic-magnesio-arfvedsonite
• Abstract: We report polarized Raman spectra from potassic-magnesio-arfvedsonite in all informative scattering configurations. On the basis of the polarization selection rules, several Ag vibrational modes have been identified. The Bg modes, however, are below the detection limits of the Raman spectrometer. The OH stretching band is situated between 3630 and 3750 cm−1, and its spectral shape is typical of amphiboles with high occupancy of the A site. It is composed of seven overlapping but resolvable subbands, which stem from occupied A-site configurations M(1)M(1)M(3)–OH–A(K/Na)–WOH and M(1)M(1)M(3)–OH–A(K/Na)–WF, as well as from vacant A-site configurations M(1)M(1)M(3)–OH–A□–WOH, with different Mg and Fe occupancy of the M(1) and M(3) sites. The experimental Raman spectra are compared with the results of theoretical calculations based on a shell-model force-field and a bond polarizability model. The simulated partial Raman spectra allowed us to assign many low-frequency Raman bands to stretching vibrations involving specific cation-oxygen bonds, as well as the higher-frequency modes of the Si–O skeleton. On the basis of our calculations we hypothesize that the Raman bands at 467, 540 and 589 cm−1 are related to a superposition of M(2)Fe3+–O bond stretching and Si–O–Si bending vibrations.
PubDate: 2019-02-01
DOI: 10.1007/s00269-018-0996-4

• Crystal-chemistry and vibrational spectroscopy of ferrinatrite, Na 3
[Fe(SO 4 ) 3 ]·3H 2 O, and its high-temperature decomposition
• Abstract: The crystal structure of ferrinatrite, Na3[Fe(SO4)3]·3H2O, was refined based on a new single-crystal X-ray diffraction experiment on a sample from the type locality Sierra Gorda, Chile. The data allowed H to be successfully located and the H-bonding system to be defined. Infrared and Raman spectra are presented and discussed for this compound on the basis of the crystal structure. The Oacceptor···H–Odonor bond distances determined from the structure refinement agree well with the geometric correlation obtained from spectroscopic data. The thermal stability and dehydration process of ferrinatrite was investigated by in situ high temperature (HT) synchrotron X-ray powder diffraction, Raman and Fourier transform infrared spectroscopies.
PubDate: 2019-02-01
DOI: 10.1007/s00269-018-0991-9

• Crystal chemistry of Eu-bearing tuite synthesized at high-pressure and
high-temperature conditions
• Abstract: Tuite, γ-Ca3(PO4)2, is a potential host for rare-earth elements in the deep mantle. Eu-bearing tuite single crystals with chemical formulas of Ca2.93Eu0.04(PO4)2 and Ca2.88Eu0.07Na0.06(PO4)2 were synthesized at 16 GPa and 1600 °C, and their structures were investigated at room temperature with single-crystal X-ray diffraction. The structure refinements of Eu-bearing tuite indicate the preference of Eu3+ for the smaller 6-coordinated Ca1 site with a coupled vacancy due to the substitution of 2Eu3+ + □ → 3 Ca2+. In NaEu-bearing tuite, both Eu3+ and Na+ occupy the smaller 6-coordinated Ca1 site according to the coupled substitution of Eu3+ + Na+ → 2 Ca2+. The presence of Na results in more Eu2O3 in NaEu-bearing tuite, because the coupled substitution is energetically more favorable. REE-bearing tuite could be found on the Moon and the deep Earth’s mantle as a consequence of REE-bearing apatite or/and merrillite transformation under high-pressure and high-temperature conditions.
PubDate: 2019-02-01
DOI: 10.1007/s00269-018-0994-6

• Equations of state of Co 2 TiO 4 -Sp, Co 2 TiO 4 -CM, and Co 2 TiO 4 -CT,
and their phase transitions: an experimental and theoretical study
• Abstract: Co2TiO4 spinel (Co2TiO4-Sp) was synthesized at 1573 K and room P by heating in an argon atmosphere for 72 h, and quasi-hydrostatically compressed to ~ 24 GPa using a diamond-anvil cell in conjunction with a synchrotron X-ray radiation (ambient T). We found that the Co2TiO4-Sp was stable up to ~ 21 GPa and transformed to a new phase at higher P. With some theoretical simulations, we revealed that this new phase adopted the CaMn2O4-type structure (Co2TiO4-CM), which might further transform to the CaTi2O4-type structure (Co2TiO4-CT) at ~ 35 GPa. The isothermal bulk modulus (KT) was experimentally obtained as 175.5(36) GPa for the Co2TiO4-Sp and 161(7) GPa for the Co2TiO4-CM, with its first pressure derivative $$K_{{\text{T}}}^{'}$$ as 2.8(5) and 7.3(8), respectively. Furthermore, the KT was theoretically constrained (the GGA method) as 138(3) GPa for the Co2TiO4-CM and 196.8(14) GPa for the Co2TiO4-CT, with the $$K_{{\text{T}}}^{'}$$ as 7.6(3) and 5.0(1), respectively. Consequently, the Co2TiO4-CM is ~ 12.3% denser than the Co2TiO4-Sp at ~ 21 GPa, whereas the Co2TiO4-CT is just ~ 0.8% denser than the Co2TiO4-CM at ~ 35 GPa. The spinel and post-spinel phase assemblages for the Co2TiO4 composition at some high T have been tentatively deduced as Co2TiO4-Sp, CoO-B1 (NaCl-type structure) + CoTiO3-Ilm (ilmenite-type structure), 2CoO-B1 + TiO2-α-PbO2 (α-PbO2-type structure), Co2TiO4-CM and Co2TiO4-CT, as P increases.
PubDate: 2019-02-01
DOI: 10.1007/s00269-019-01023-3

• Calcite–magnesite solid solutions: using genetic algorithms to
understand non-ideality
• Abstract: We show how a genetic algorithm (GA) generates efficiently the energy landscape of the equimolar calcite–magnesite (CaCO3—MgCO3) solid solution. Starting from a random configuration of cations and a supercell containing 480 atoms, the lowest energy form of ordered dolomite was found in all runs, in 94% of which it was located with less than 20,000 fitness evaluations. Practical implementation and operation of the GA are discussed in detail. The method can also generate both low-lying and high-lying excited states. Detailed analysis of the energy-minimised structures of the different configurations reveals that low energies are associated with reduction of strain associated with rotation of the carbonate groups, a mechanism possible only when a carbonate layer lies between a layer of just Ca and a layer of just Mg. Such strain relief is not possible in the equimolar MgO–CaO solid solution despite the similarity of the crystal structures of these binary oxides to calcite–magnesite, and therefore, the enthalpy of mixing is very high. Implications for thermodynamic configurational averaging over the minima in the energy landscape are briefly considered. Overall, the genetic algorithm is shown to be a powerful tool in probing non-ideality in solid solutions and revealing the ordering patterns that give rise to such behaviour.
PubDate: 2019-02-01
DOI: 10.1007/s00269-018-0997-3

• Iron distribution in Fe-rich bustamite-type minerals
• Abstract: The crystal chemical role of iron in Fe-rich pyroxenoids with bustamite-type structure was studied on five samples containing from 6.0 to 10.3 wt% FeO using electron microprobe, XRD crystal structure refinement and Mössbauer spectroscopy. The crystal chemical formulae are (Z = 1): M1(Mn0.85Fe2+0.15)2M2(Ca0.8Mn0.2)2M3(Fe2 +0.5Mn0.4(Mg,Al,Zn)0.1)M4Ca[Si3O9]2 (Broken Hill, New South Wales, Australia), M1(Mn0.8Fe2+0.2)2M2(Mn0.55Са0.45)2M3(Fe2 +0.60Mn0.40)M4Ca[Si3O9]2 (Olginskoe, Primorskiy Kray, Russia), M1(Mn0.8Fe2+0.2)2M2(Ca0.5Mn0.5)2M3(Mn0.50Fe2+0.35Mg0.15)M4(Ca0.7Mn0.3)[Si3O9]2 (Broken Hill), M1Ca2M2Ca2M3Fe2+M4Ca[Si3O9]2 (Tyrnyauz, North Caucasus, Russia), M1Ca2M2Ca2M3(Fe2 +0.6Mn0.4)M4Ca[Si3O9]2 (Dalnegorsk, Primorskiy Kray, Russia). Iron in bustamite-type compounds concentrates at the M1 and M3 sites which are characterized by the shortest ⟨M–O⟩ distances. In general, the distribution of Fe and Mn in bustamite-type minerals is rather similar. Iron only slightly prefer the smallest in volume M3O6 octahedron rather than M1O6. Unlike related pyroxenoids of the rhodonite group, significant Mn:Fe ordering in bustamite-type minerals was not observed.
PubDate: 2019-02-01
DOI: 10.1007/s00269-018-0992-8

• Thermodynamic properties of CaCO 3 –SrCO 3 –BaCO 3 liquids: a
molecular dynamics study using new empirical atomic potentials for
alkaline earth carbonates
• Abstract: Thermodynamic modeling offers a powerful framework for studying melting reactions of carbonated mantle systems across a wide range of compositions, pressures, and temperatures. Such modeling requires knowledge of the standard state thermodynamic properties of the pure alkaline earth carbonate liquid components, which are difficult to determine experimentally due to their instability at 1 bar. Atomistic simulations offer a solution to these experimental difficulties by providing access to metastable states and supplying constraints on thermodynamic properties. We developed an empirically-derived potential model for the simulation of alkaline earth carbonates (MgCO3, CaCO3, SrCO3 and BaCO3), emphasizing the accurate simulation of the standard state thermodynamic properties of carbonate liquids. Molecular dynamics (MD) simulations of liquids in the CaCO3–SrCO3–BaCO3 system are performed over a geologically relevant temperature–pressure range (1100–3400 K and 0–43 GPa). Simulation data for each of these three components (up to a maximum of 2300 K and 30 GPa) are fitted to a temperature-dependent third-order Birch–Murnaghan equation-of-state to estimate their standard state thermodynamic properties. With a few exceptions, calculated properties agree well with available estimates from experiments and/or first-principles MD simulations. Exploration of binary mixtures supports ideal mixing of volumes, heat capacities, and compressibilities, reflecting the common liquid structure and pressure–temperature evolution for these three components. The success of this new model for CaCO3–SrCO3–BaCO3 liquids suggests that it can accurately predict the properties of MgCO3-bearing liquids, where experimental data are unavailable.
PubDate: 2019-02-01
DOI: 10.1007/s00269-018-0995-5

• Natural bentorite—Cr 3+ derivate of ettringite: determination of
crystal structure
• Abstract: Bentorite, a Cr3+-substituted analogue of ettringite (Ca6Cr2(SO4)3(OH)12·26H2O), has been found as veinlet filling at its holotype locality in the Hatrurim Basin (Negev Desert). Quite abundant massive bentorite with Cr/(Cr + Al) ratios up to 0.95–0.99 coexists with sporadic portlandite, gypsum, afwillite, truscottite, fluorapatite, tobermorite, calcite, and vaterite. It occurs as almost monomineralic clots composed of fibrous grains. The crystal structure of bentorite has been determined and refined for the first time by XRD powder diffraction coupled with high-accuracy synchrotron low-temperature measurements at 100, 250 K and 295 K. Bentorite is isostructural with ettringite, space group P31c. The analysed bentorite sample has a trigonal unit cell with the parameters a = 11.16150(5), c = 21.63017(19) Å, V = 2333.650(19) Å3 at 100 K; a = 11.17790(5), c = 21.7375(2) Å, and V = 2352.12(2) Å3 at 250 K, and a = 11.2110(2), c = 21.7654(7) Å, and V = 2369.10(7) Å3 at 295 K. The bentorite structure includes only (SO4)2−-groups, three anions per formula unit, as in ettringite. Unlike ettringite, bentorite has Cr3+ instead of Al3+ cations, this being the only difference in chemistry. The obtained structure confirms the existence of a continuous series of ettringite $$\normalsize {\text{C}}{{\text{a}}_6}{\text{Al}}_{2}^{{\text{M}}}\left[ {{\text{S}}{{\text{O}}_4}} \right]_{3}^{\text{R}}{({\text{OH}})_{12}} \cdot 26{{\text{H}}_{\text{2}}}{\text{O}}$$ –bentorite $${\text{C}}{{\text{a}}_6}{\text{Cr}}_{2}^{{\text{M}}}\left[ {{\text{S}}{{\text{O}}_4}} \right]_{3}^{{\text{R}}}{({\text{OH}})_{12}} \cdot 26{{\text{H}}_{\text{2}}}{\text{O}}$$ solid solutions over the whole range 0 ≤ Cr3+/(Al + Cr3+) ≤ 1.
PubDate: 2019-01-28
DOI: 10.1007/s00269-019-01022-4

• Thermophysical properties and phase diagrams in the system MgO–SiO 2
–FeO at upper mantle and transition zone conditions derived from a
multiple-Einstein method
• Abstract: We applied a lattice vibrational technique, based on representing the vibrational density of states with multiple-Einstein frequencies, to determine consistency of data on thermophysical properties and phase diagrams in the system MgO–FeO–SiO2. We present analyses of these data in the temperature range between 0 and 2000 K and pressure range between 0 and 20 GPa. The result is a database containing phases relevant to the Earth upper mantle and transition zone. We show that consistency of different datasets associated with the dissociation of the ringwoodite form of Fe2SiO4 depends on the crucible material that has been used to perform partitioning experiments between ringwoodite and ferropericlase, and that this results in different phase diagrams for FeSiO3 and the post-spinel part of Mg2SiO4–Fe2SiO4. We show that the existence of a phase field coesite + ringwoodite in the phase diagram of FeSiO3 is possible and that it might be used to fine-tune pressure scales. We demonstrate that the phase boundary between coesite and quartz is very sensitive to the low-temperature heat capacity of coesite and that heat capacity data of β-quartz are too large to be reconciled with the phase boundary between β-quartz and coesite. We compare our results with seismic data associated with the 410 km seismic discontinuity.
PubDate: 2019-01-19
DOI: 10.1007/s00269-018-01020-y

• Thermodynamics, structure, and transport properties of the MgO–Al 2
O 3 liquid system
• Abstract: Seven liquids along the MgO–Al2O3 join were simulated at zero pressure in temperature (T) range 2000–6000 K using the first-principles molecular dynamics method. The simulation results show continuous changes in various physical properties with composition (molar fraction of alumina, X). They suggest that the binary mixing tends to be nearly ideal with no immiscibility along the entire join. The calculated mean coordination numbers of MgO and AlO polyhedra gradually increase with increasing X, for example, their respective values are 4.6 and 4.3 at/near the MgO end, 5.2 and 4.6 for MgAl2O4 spinel composition, and 5.5 and 4.8 at/near the alumina end. The mean O–O coordination number remains almost unchanged along the join at ≥ 12 implying a closely packed arrangement. In contrast, all other coordination types including O–Mg and O–Al change dramatically along the join. The calculated self-diffusion and viscosity coefficients vary much less with composition (by a factor of 4 or less along the entire join) than with temperature (by two orders of magnitudes over the T range considered). Their T–X variations can be well described by the respective Arrhenius equations with composition-dependent activation energies and pre-exponential parameters. While the alumina and silica components are considered to play a similar role with regard to the structural polymerization of amorphous aluminosilicates, our results show that they influence the melt transport properties very differently. Therefore, the general notion that these two oxide components play an equivalent role in multicomponent magmatic melts is not unambiguous.
PubDate: 2019-01-14
DOI: 10.1007/s00269-018-01019-5

• Simultaneous measurements of electrical conductivity and seismic wave
velocity of partially molten geological materials: effect of evolving melt
texture
• Abstract: Comparison between geophysical observations and laboratory measurements yields contradicting estimations of the melt fraction for the partially molten regions of the Earth, highlighting potential disagreements between laboratory-based electrical conductivity and seismic wave velocity measurement techniques. In this study, we performed simultaneous acoustic wave velocity and electrical conductivity measurements on a simplified partial melt analogue (olivine + mid oceanic ridge basalt, MORB) at 2.5 GPa and up to 1650 K. We aim to investigate the effect of ongoing textural modification of partially molten peridotite analog on both electrical conductivity and sound wave velocity. Acoustic wave velocity (Vp and Vs) and EC are measured on an identical sample presenting the same melt texture, temperature gradient, stress field and chemical impurities. We observe a sharp decrease of acoustic wave velocities and increase of electrical conductivity in response to melting of MORB component. At constant temperature of 1650 K, electrical conductivity gradually increases, whereas acoustic velocities remain relatively constant. While the total MORB components melt instantaneously above the melting temperature, the melt interconnectivity and the melt distribution should evolve with time, affecting the electrical conduction. Consequently, our experimental observations suggest that acoustic velocities respond spontaneously to the melt volume fraction for melt with high wetting properties, whereas electrical conduction is significantly affected by subsequent melt texture modifications. We find that acoustic velocity measurements are thus better suited to the determination of the melt fraction of a partially molten sample at the laboratory time scale (~ h). Based on our estimations, the reduced Vs velocity in the major part of the low velocity zone away from spreading ridges can be explained by 0.3–0.8 vol% volatile-bearing melt and the high Vp/Vs ratio obtained for these melt fractions (1.82–1.87) are compatible with geophysical observations.
PubDate: 2019-01-11
DOI: 10.1007/s00269-019-01021-5

JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762