The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Andrea Giuliani - One of the best experts on this subject based on the ideXlab platform.

  • contrasting types of micaceous kimberlite lamproite magmatism from the man craton west africa new insights from petrography and mineral chemistry
    Lithos, 2020
    Co-Authors: Geoffrey H Howarth, Andrea Giuliani
    Abstract:

    Abstract Diamondiferous rock types worldwide are broadly divided into kimberlite and lamproite, the latter of which have unique characteristics in different regions and include carbonate-rich varieties (formerly orangeites/Group II kimberlites). Diamondiferous rocks in West Africa are typically micaceous and share petrographic, mineralogical, and geochemical characteristics with both kimberlites and lamproites. To further constrain the classification and petrogenesis of diamondiferous rocks worldwide and their variability between different cratonic regions, in this study we combine detailed petrographic observations with olivine, Phlogopite, and spinel chemistry for hypabyssal samples from the Jurassic Tongo dike (Sierra Leone) and the Neoproterozoic Weasua cluster (Liberia). The Tongo dike contains macrocrysts of olivine and Phlogopite in a groundmass of olivine, abundant Phlogopite, spinel, perovskite, and apatite with a base of calcite, dolomite, and lesser serpentine. The Phlogopite is characterised by concurrent FeO and Al2O3 enrichment, which is typical of kimberlites and unlike lamproites. These features and the kimberlite-like spinel compositions allow us to classify the Tongo samples as micaceous kimberlites. The Weasua rocks comprise macrocrysts of olivine in a groundmass of olivine, Phlogopite, diopside (zoned towards aegirine-rich rims), spinel, perovskite, and apatite with a base of serpentine and less common calcite. The composition of Weasua Phlogopite trends to significant FeO enrichment and Al2O3 depletion, i.e. towards tetraferriPhlogopite. The enrichment in mica, Phlogopite chemistry and presence of magmatic diopside indicates that these rocks are olivine lamproites. The populations of olivine macrocrysts and microcrysts at Tongo and Weasua are similar and characterised by distinct core and rim zones. Two distinct olivine core populations are observed. 1) forsterite-rich (Fo > 90) olivine interpreted to reflect xenocrysts from typical mantle peridotites. Al-in-olivine thermometry suggests that these cores have P-T equilibration within diamond stability at Weasua and Tongo. 2) Al-, Ca- and Na- rich cores with P-T formation conditions extending beyond the mantle adiabat. These cores are interpreted to reflect metasomatic and thermal perturbation linked with the infiltration of kimberlite/lamproite melts in the deep lithosphere shortly before entrainment in the ascending magma. The olivine rims at Tongo and Weasua show limited variations in Fo contents at similar values of 88.9 ± 0.8 for Tongo and 89.6 ± 1.2 for Weasua, as well as similar minor and trace element concentrations. Thus, whereas the Tongo and Weasua rock types are classified as kimberlite and olivine lamproite, respectively, the olivine chemistry suggests a similar petrogenetic evolution.

  • thallium isotopic composition of Phlogopite in kimberlite hosted marid and pic mantle xenoliths
    Chemical Geology, 2020
    Co-Authors: Angus Fitzpayne, Andrea Giuliani, Julie Prytulak, Janet M Hergt
    Abstract:

    Abstract MARID (Mica-Amphibole-Rutile-Ilmenite-Diopside) and PIC (Phlogopite-Ilmenite-Clinopyroxene) rocks are rare mantle xenoliths entrained by kimberlites. Their high Phlogopite modes (15 to ∼100 vol.%) and consequent enrichments in alkali metals and H2O suggest a metasomatic origin. Phlogopite also has high concentrations (>0.2 μg/g) of thallium (Tl) relative to mantle abundances ( The e205Tl values of Phlogopite in both PIC (–2.7 ± 0.8; 2 s.d., n = 4) and MARID samples (–2.5 ± 1.3; 2 s.d., n = 21) overlap with the estimated mantle composition (–2.0 ± 1.0). PIC Phlogopite Tl contents (∼0.4 μg/g) are suggestive of equilibrium with kimberlite melts (0.1–0.6 μg/g Tl), based on partitioning experiments in other silica-undersaturated melts. Kimberlite Tl-e205Tl systematics suggest their genesis does not require a recycled contribution: however, high temperature-altered oceanic crust cannot be ruled out as a component of the Kimberley kimberlites’ source. Mantle-like e205Tl values in MARID samples also seem to contradict previous suggestions of a recycled contribution towards their genesis. Recycled components with isotopic compositions close to mantle values (e.g., high temperature-altered oceanic crust) are still permitted. Moreover, mass balance mixing models indicate that incorporation into the primitive mantle of 1–30% of a low temperature-altered oceanic crust + continental crust recycled component or 1–50% of continental crust alone could be accommodated by the Tl–e205Tl systematics of the MARID parental melt. This scenario is consistent with experimental evidence and existing isotopic data. One PIC Phlogopite separate has an extremely light Tl isotopic composition of –9.9, interpreted to result from kinetic isotopic fractionation. Overall, Phlogopite is the main host mineral for Tl in metasomatised mantle and shows a very restricted range in Tl isotopic composition, which overlaps with estimates of the mantle composition. These results strongly suggest that negligible high temperature equilibrium Tl isotopic fractionation occurs during metasomatism and reinforces previous estimates of the mantle’s Tl isotopic composition.

  • constraints on kimberlite ascent mechanisms revealed by Phlogopite compositions in kimberlites and mantle xenoliths
    Lithos, 2016
    Co-Authors: Andrea Giuliani, David Phillips, Vadim S Kamenetsky, K Goemann
    Abstract:

    Abstract Kimberlite magmas are of economic and scientific importance because they represent the major host to diamonds and are probably the deepest magmas from continental regions. In addition, kimberlite magmas transport abundant mantle and crustal xenoliths, thus providing fundamental information on the composition of the sub-continental lithosphere. Despite their importance, the composition and ascent mechanism(s) of kimberlite melts remain poorly constrained. Phlogopite is one of the few minerals that preserves a history of fluid migration and magmatism in the mantle and crust and is therefore an invaluable petrogenetic indicator of kimberlite magma evolution. Here we present major and trace element compositional data for Phlogopite from the Bultfontein kimberlite (Kimberley, South Africa; i.e. the kimberlite type-locality) and from entrained mantle xenoliths. Phlogopite macrocrysts (~ > 0.3–0.5 mm) and microcrysts (between ~ 0.1 and 0.3 mm) in the Bultfontein kimberlite display concentric compositional zoning patterns. The cores of these Phlogopite grains exhibit compositions typical of Phlogopite contained in peridotite mantle xenoliths. However, the rims of some grains show compositions analogous to kimberlite groundmass Phlogopite (i.e. high Ti, Al and Ba; low Cr), whereas other rims and intermediate zones (between cores and rims) exhibit unusually elevated Cr and lower Al and Ba concentrations. The latter compositions are indistinguishable from matrix Phlogopite in polymict breccia xenoliths (considered to represent failed kimberlite intrusions) and from Ti-rich overgrowth rims on Phlogopite in other mantle xenoliths. Consequently, it is likely that these Phlogopite grains crystallized from kimberlite melts and that the high Ti-Cr zones originated from earlier kimberlite melts at mantle depths. We postulate that successive pulses of ascending kimberlite magma progressively metasomatised the conduit along which later kimberlite pulses ascended, producing progressively decreasing interaction with the surrounding mantle rocks. In our view, these processes represent the fundamental mechanism of kimberlite magma ascent. Our study also indicates that, in addition to xenoliths/xenocrysts and magmatic phases, kimberlite rocks incorporate material crystallized at various mantle depths by previous kimberlite intrusions (mantle-derived ‘antecrysts’).

L V Sazonova - One of the best experts on this subject based on the ideXlab platform.

  • Phlogopite in mantle xenoliths and kimberlite from the grib pipe arkhangelsk province russia evidence for multi stage mantle metasomatism and origin of Phlogopite in kimberlite
    Geoscience frontiers, 2019
    Co-Authors: A V Kargin, L V Sazonova, A A Nosova, N M Lebedeva, V V Tretyachenko, Yu A Kostitsyn, E V Kovalchuk, Ya S Tikhomirova
    Abstract:

    Abstract We present petrography and mineral chemistry for both Phlogopite, from mantle-derived xenoliths (garnet peridotite, eclogite and clinopyroxene–Phlogopite rocks) and for megacryst, macrocryst and groundmass flakes from the Grib kimberlite in the Arkhangelsk diamond province of Russia to provide new insights into multi-stage metasomatism in the subcratonic lithospheric mantle (SCLM) and the origin of Phlogopite in kimberlite. Based on the analysed xenoliths, Phlogopite is characterized by several generations. The first generation (Phl1) occurs as coarse, discrete grains within garnet peridotite and eclogite xenoliths and as a rock-forming mineral within clinopyroxene–Phlogopite xenoliths. The second Phlogopite generation (Phl2) occurs as rims and outer zones that surround the Phl1 grains and as fine flakes within kimberlite-related veinlets filled with carbonate, serpentine, chlorite and spinel. In garnet peridotite xenoliths, Phlogopite occurs as overgrowths surrounding garnet porphyroblasts, within which Phlogopite is associated with Cr-spinel and minor carbonate. In eclogite xenoliths, Phlogopite occasionally associates with carbonate bearing veinlet networks. Phlogopite, from the kimberlite, occurs as megacrysts, macrocrysts, microcrysts and fine flakes in the groundmass and matrix of kimberlitic pyroclasts. Most Phlogopite grains within the kimberlite are characterised by signs of deformation and form partly fragmented grains, which indicates that they are the disintegrated fragments of previously larger grains. Phl1, within the garnet peridotite and clinopyroxene–Phlogopite xenoliths, is characterised by low Ti and Cr contents (TiO2   92) typical of primary peridotite Phlogopite in mantle peridotite xenoliths from global kimberlite occurrences. They formed during SCLM metasomatism that led to a transformation from garnet peridotite to clinopyroxene–Phlogopite rocks and the crystallisation of Phlogopite and high-Cr clinopyroxene megacrysts before the generation of host-kimberlite magmas. One of the possible processes to generate low-Ti-Cr Phlogopite is via the replacement of garnet during its interaction with a metasomatic agent enriched in K and H2O. Rb–Sr isotopic data indicates that the metasomatic agent had a contribution of more radiogenic source than the host-kimberlite magma. Compared with peridotite xenoliths, eclogite xenoliths feature low-Ti Phlogopites that are depleted in Cr2O3 despite a wider range of TiO2 concentrations. The presence of Phlogopite in eclogite xenoliths indicates that metasomatic processes affected peridotite as well as eclogite within the SCLM beneath the Grib kimberlite. Phl2 has high Ti and Cr concentrations (TiO2 > 2 wt.%, Cr2O3 > 1 wt.% and Mg# = 100 × Mg/(Mg + Fe)

  • cr rich clinopyroxene megacrysts from the grib kimberlite arkhangelsk province russia relation to clinopyroxene Phlogopite xenoliths and evidence for mantle metasomatism by kimberlite melts
    Lithos, 2017
    Co-Authors: A V Kargin, L V Sazonova, A A Nosova, N M Lebedeva, V V Tretyachenko, Adam Abersteiner
    Abstract:

    Abstract To provide new insights into the origin of megacrysts and metasomatism of the subcontinental lithospheric mantle (SCLM), we present a detailed petrographic and geochemical investigation of clinopyroxene-Phlogopite xenoliths and clinopyroxene megacrysts from the Grib kimberlite (Arkhangelsk diamond province, Russia). Clinopyroxene megacrysts and clinopyroxene from clinopyroxene-Phlogopite xenoliths have similar petrography, major and trace element compositions, and are therefore classified as Cr-rich megacrysts. Geothermobarometry suggests that Cr-rich clinopyroxenes originate from within the SCLM (3.6–4.7 GPa and 764–922 °C). Phlogopite from clinopyroxene-Phlogopite xenoliths have low-Ti and -Cr compositions that overlaps with Phlogopite megacrysts from the Grib kimberlite. The clinopyroxene-Phlogopite rocks within the SCLM are the main source for Cr-rich clinopyroxene and low-Ti Phlogopite megacrysts in the Grib kimberlite matrix. Trace element compositions of studied Cr-rich clinopyroxenes have similar geochemical features to clinopyroxenes megacrysts occurrences worldwide and overlap with clinopyroxenes from Phlogopite-garnet peridotite xenoliths from the Grib kimberlite. The strong depletion in Ti, Nb, Ta and to a lesser extent in Zr and Hf in clinopyroxene reflects equilibrium with Ti-oxides, such as ilmenite. The clinopyroxene-Phlogopite xenoliths could be the final product of metasomatism of garnet peridotites within the SCLM beneath the Grib kimberlite. The calculated equilibrium of clinopyroxene melt compositions suggests that the metasomatic agents were derived from silicate-bearing kimberlite melts. The presence of veinlets infilled with kimberlitic mineral assemblages in clinopyroxene grains suggests that the clinopyroxene-Phlogopite rocks experienced intense interactions with kimberlite melt after their formation, but before their entrainment into the host kimberlite magma. This interaction resulted in the formation of high-Ti and -Cr Phlogopite and high-Ti clinopyroxene rims, zones and grains with spongy textures. Finally, we propose the sequence of metasomatic events that occurred in the SCLM and the subsequent formation of the Grib kimberlite.

  • kimberlite age in the arkhangelsk province russia isotopic geochronologic rb sr and 40ar 39ar and mineralogical data on Phlogopite
    Petrology, 2016
    Co-Authors: Yu O Larionova, L V Sazonova, A A Nosova, N M Lebedeva, V V Tretyachenko, A V Travin
    Abstract:

    The paper reports detailed data on Phlogopite from kimberlite of three facies types in the Arkhangelsk Diamondiferous Province (ADP): (i) massive magmatic kimberlite (Ermakovskaya-7 Pipe), (ii) transitional type between massive volcaniclastic and magmatic kimberlite (Grib Pipe), and (iii) volcanic kimberlite (Karpinskii-1 and Karpinskii-2 pipes). Kimberlite from the Ermakovskaya-7 Pipe contains only groundmass Phlogopite. Kimberlite from the Grib Pipe contains a number of Phlogopite populations: megacrysts, macrocrysts, matrix Phlogopite, and this mineral in xenoliths. Phlogopite macrocrysts and matrix Phlogopite define a single compositional trend reflecting the evolution of the kimberlite melt. The composition points of Phlogopite from the xenoliths lie on a single crystallization trend, i.e., the mineral also crystallized from kimberlite melt, which likely actively metasomatized the host rocks from which the xenoliths were captured. Phlogopite from volcaniclastic kimberlite from the Karpinskii-1 and Karpinskii-2 pipes does not show either any clearly distinct petrographic setting or compositional differentiation. The kimberlite was dated by the Rb–Sr technique on Phlogopite and additionally by the 40Ar/39Ar method. Because it is highly probable that Phlogopite from all pipes crystallized from kimberlite melt, the crystallization age of the kimberlite can be defined as 376 ± 3 Ma for the Grib Pipe, 380 ± 2 Ma for the Karpinskii-1 pipe, 375 ± 2 Ma for the Karpinskii-2 Pipe, and 377 ± 0.4 Ma for the Ermakovskaya-7 Pipe. The age of the pipes coincides within the error and suggests that the melts of the pipes were emplaced almost simultaneously. Our geochronologic data on kimberlite emplacement in ADP lie within the range of 380 ± 2 to 375 ± Ma and coincide with most age values for Devonian alkaline–ultramafic complexes in the Kola Province: 379 ± 5 Ma; Arzamastsev and Wu, 2014). These data indicate that the kimberlite was formed during the early evolution of the Kola Province, when alkaline–ultramafic complexes (including those with carbonatite) were emplaced.

N M Lebedeva - One of the best experts on this subject based on the ideXlab platform.

  • Phlogopite in mantle xenoliths and kimberlite from the grib pipe arkhangelsk province russia evidence for multi stage mantle metasomatism and origin of Phlogopite in kimberlite
    Geoscience frontiers, 2019
    Co-Authors: A V Kargin, L V Sazonova, A A Nosova, N M Lebedeva, V V Tretyachenko, Yu A Kostitsyn, E V Kovalchuk, Ya S Tikhomirova
    Abstract:

    Abstract We present petrography and mineral chemistry for both Phlogopite, from mantle-derived xenoliths (garnet peridotite, eclogite and clinopyroxene–Phlogopite rocks) and for megacryst, macrocryst and groundmass flakes from the Grib kimberlite in the Arkhangelsk diamond province of Russia to provide new insights into multi-stage metasomatism in the subcratonic lithospheric mantle (SCLM) and the origin of Phlogopite in kimberlite. Based on the analysed xenoliths, Phlogopite is characterized by several generations. The first generation (Phl1) occurs as coarse, discrete grains within garnet peridotite and eclogite xenoliths and as a rock-forming mineral within clinopyroxene–Phlogopite xenoliths. The second Phlogopite generation (Phl2) occurs as rims and outer zones that surround the Phl1 grains and as fine flakes within kimberlite-related veinlets filled with carbonate, serpentine, chlorite and spinel. In garnet peridotite xenoliths, Phlogopite occurs as overgrowths surrounding garnet porphyroblasts, within which Phlogopite is associated with Cr-spinel and minor carbonate. In eclogite xenoliths, Phlogopite occasionally associates with carbonate bearing veinlet networks. Phlogopite, from the kimberlite, occurs as megacrysts, macrocrysts, microcrysts and fine flakes in the groundmass and matrix of kimberlitic pyroclasts. Most Phlogopite grains within the kimberlite are characterised by signs of deformation and form partly fragmented grains, which indicates that they are the disintegrated fragments of previously larger grains. Phl1, within the garnet peridotite and clinopyroxene–Phlogopite xenoliths, is characterised by low Ti and Cr contents (TiO2   92) typical of primary peridotite Phlogopite in mantle peridotite xenoliths from global kimberlite occurrences. They formed during SCLM metasomatism that led to a transformation from garnet peridotite to clinopyroxene–Phlogopite rocks and the crystallisation of Phlogopite and high-Cr clinopyroxene megacrysts before the generation of host-kimberlite magmas. One of the possible processes to generate low-Ti-Cr Phlogopite is via the replacement of garnet during its interaction with a metasomatic agent enriched in K and H2O. Rb–Sr isotopic data indicates that the metasomatic agent had a contribution of more radiogenic source than the host-kimberlite magma. Compared with peridotite xenoliths, eclogite xenoliths feature low-Ti Phlogopites that are depleted in Cr2O3 despite a wider range of TiO2 concentrations. The presence of Phlogopite in eclogite xenoliths indicates that metasomatic processes affected peridotite as well as eclogite within the SCLM beneath the Grib kimberlite. Phl2 has high Ti and Cr concentrations (TiO2 > 2 wt.%, Cr2O3 > 1 wt.% and Mg# = 100 × Mg/(Mg + Fe)

  • cr rich clinopyroxene megacrysts from the grib kimberlite arkhangelsk province russia relation to clinopyroxene Phlogopite xenoliths and evidence for mantle metasomatism by kimberlite melts
    Lithos, 2017
    Co-Authors: A V Kargin, L V Sazonova, A A Nosova, N M Lebedeva, V V Tretyachenko, Adam Abersteiner
    Abstract:

    Abstract To provide new insights into the origin of megacrysts and metasomatism of the subcontinental lithospheric mantle (SCLM), we present a detailed petrographic and geochemical investigation of clinopyroxene-Phlogopite xenoliths and clinopyroxene megacrysts from the Grib kimberlite (Arkhangelsk diamond province, Russia). Clinopyroxene megacrysts and clinopyroxene from clinopyroxene-Phlogopite xenoliths have similar petrography, major and trace element compositions, and are therefore classified as Cr-rich megacrysts. Geothermobarometry suggests that Cr-rich clinopyroxenes originate from within the SCLM (3.6–4.7 GPa and 764–922 °C). Phlogopite from clinopyroxene-Phlogopite xenoliths have low-Ti and -Cr compositions that overlaps with Phlogopite megacrysts from the Grib kimberlite. The clinopyroxene-Phlogopite rocks within the SCLM are the main source for Cr-rich clinopyroxene and low-Ti Phlogopite megacrysts in the Grib kimberlite matrix. Trace element compositions of studied Cr-rich clinopyroxenes have similar geochemical features to clinopyroxenes megacrysts occurrences worldwide and overlap with clinopyroxenes from Phlogopite-garnet peridotite xenoliths from the Grib kimberlite. The strong depletion in Ti, Nb, Ta and to a lesser extent in Zr and Hf in clinopyroxene reflects equilibrium with Ti-oxides, such as ilmenite. The clinopyroxene-Phlogopite xenoliths could be the final product of metasomatism of garnet peridotites within the SCLM beneath the Grib kimberlite. The calculated equilibrium of clinopyroxene melt compositions suggests that the metasomatic agents were derived from silicate-bearing kimberlite melts. The presence of veinlets infilled with kimberlitic mineral assemblages in clinopyroxene grains suggests that the clinopyroxene-Phlogopite rocks experienced intense interactions with kimberlite melt after their formation, but before their entrainment into the host kimberlite magma. This interaction resulted in the formation of high-Ti and -Cr Phlogopite and high-Ti clinopyroxene rims, zones and grains with spongy textures. Finally, we propose the sequence of metasomatic events that occurred in the SCLM and the subsequent formation of the Grib kimberlite.

  • kimberlite age in the arkhangelsk province russia isotopic geochronologic rb sr and 40ar 39ar and mineralogical data on Phlogopite
    Petrology, 2016
    Co-Authors: Yu O Larionova, L V Sazonova, A A Nosova, N M Lebedeva, V V Tretyachenko, A V Travin
    Abstract:

    The paper reports detailed data on Phlogopite from kimberlite of three facies types in the Arkhangelsk Diamondiferous Province (ADP): (i) massive magmatic kimberlite (Ermakovskaya-7 Pipe), (ii) transitional type between massive volcaniclastic and magmatic kimberlite (Grib Pipe), and (iii) volcanic kimberlite (Karpinskii-1 and Karpinskii-2 pipes). Kimberlite from the Ermakovskaya-7 Pipe contains only groundmass Phlogopite. Kimberlite from the Grib Pipe contains a number of Phlogopite populations: megacrysts, macrocrysts, matrix Phlogopite, and this mineral in xenoliths. Phlogopite macrocrysts and matrix Phlogopite define a single compositional trend reflecting the evolution of the kimberlite melt. The composition points of Phlogopite from the xenoliths lie on a single crystallization trend, i.e., the mineral also crystallized from kimberlite melt, which likely actively metasomatized the host rocks from which the xenoliths were captured. Phlogopite from volcaniclastic kimberlite from the Karpinskii-1 and Karpinskii-2 pipes does not show either any clearly distinct petrographic setting or compositional differentiation. The kimberlite was dated by the Rb–Sr technique on Phlogopite and additionally by the 40Ar/39Ar method. Because it is highly probable that Phlogopite from all pipes crystallized from kimberlite melt, the crystallization age of the kimberlite can be defined as 376 ± 3 Ma for the Grib Pipe, 380 ± 2 Ma for the Karpinskii-1 pipe, 375 ± 2 Ma for the Karpinskii-2 Pipe, and 377 ± 0.4 Ma for the Ermakovskaya-7 Pipe. The age of the pipes coincides within the error and suggests that the melts of the pipes were emplaced almost simultaneously. Our geochronologic data on kimberlite emplacement in ADP lie within the range of 380 ± 2 to 375 ± Ma and coincide with most age values for Devonian alkaline–ultramafic complexes in the Kola Province: 379 ± 5 Ma; Arzamastsev and Wu, 2014). These data indicate that the kimberlite was formed during the early evolution of the Kola Province, when alkaline–ultramafic complexes (including those with carbonatite) were emplaced.

Young-shin Jun - One of the best experts on this subject based on the ideXlab platform.

  • supercritical co2 brine induced dissolution swelling and secondary mineral formation on Phlogopite surfaces at 75 95 c and 75 atm
    Energy and Environmental Science, 2012
    Co-Authors: Daniel J Garcia, Hongbo Shao, Jessica R. Ray, Young-shin Jun
    Abstract:

    To safely implement geologic carbon sequestration (GCS), a better understanding of geochemical reactions at supercritical CO2 (scCO2)–brine–clay mineral interfaces is necessary. This work investigated Phlogopite dissolution and secondary mineral formation after freshly cleaved (001) surfaces were exposed to scCO2–brine systems. Phlogopite was used as a model clay mineral, and scCO2–1 M NaCl–Phlogopite systems at 75 °C and 75 atm were chosen to mimic CO2 storage conditions in deep saline aquifers. Additional experiments were also performed at 95 °C to explore the effect of temperature on Phlogopite dissolution. The dissolution activation energies for each element were calculated to be 64.2 kJ mol−1 for Si, 53.6 kJ mol−1 for Mg, and 78.4 kJ mol−1 for Al. Over 43 h of reaction time, the activation energy for K dissolution was calculated to be 35.9 kJ mol−1. A whole-mineral activation energy for Phlogopite, 62.5 kJ mol−1, was estimated from the weighted mean values of the activation energies of the framework elements (Al, Si, and Mg). Swelling of the Phlogopite outer layers, dissolution pit formation, and precipitation of both illite and amorphous silica were dominant at both temperatures. At 75 °C, normalized volumetric surface coverage (μm3/μm2) was 0.34 ± 0.74 for illite and 0.05 ± 0.90 for amorphous silica nanoparticles.

  • Effects of organic ligands on supercritical CO2-induced Phlogopite dissolution and secondary mineral formation
    Chemical Geology, 2011
    Co-Authors: Hongbo Shao, Jessica R. Ray, Young-shin Jun
    Abstract:

    Abstract To evaluate the long-term and short-term risks associated with geologic CO 2 sequestration (GCS), we need to understand both the reactions at supercritical CO 2 (scCO 2 )–saline water–rock interfaces, and the environmental factors affecting these interactions. This research investigated the effects of four organic ligands—oxalate, malonate, acetate, and propionate—on the dissolution and surface morphological changes of Phlogopite [KMg 2.87 Si 3.07 Al 1.23 O 10 (F,OH) 2 ] under GCS conditions (95 °C and 102 atm). Phlogopite was chosen as a model clay mineral in potential GCS sites. After CO 2 injection, the dissolution of CO 2 should cause a decrease in saline water pH, increasing Phlogopite dissolution. This effect can be lessened by the buffering capacity of organic ligands. However, in this study, the ligands that formed strong complexes with surface metals (i.e., oxalate) caused Phlogopite dissolution rates to increase via ligand-promoted dissolution, although the pH increased. The experimentally observed dissolution rates of Phlogopite were in the order of: oxalate > malonate > acetate ≈ propionate. In addition, based on results from ion chromatography, oxalate and malonate concentrations were stable in our reaction systems; however, aqueous acetate and propionate concentrations continuously decreased due to solvent extraction of acetic acid and propionic acid by scCO 2 at 95 °C and 102 atm. After 159 h, all of the acetate and propionate were removed from aqueous solutions. Although the aqueous species in the bulk solution were not supersaturated with respect to potential secondary mineral phases, interestingly, in the presence of oxalate, nanoscale precipitation of amorphous silica and fibrous illite was observed at the Phlogopite surface only 3 h after CO 2 injection. At this early reaction time, illite fibers formed a connected, hexagonal framework on Phlogopite basal surfaces, but at a later reaction time, these structures detached from the surface and triggered the formation of dissolution channels. In addition, kaolinite, boehmite, diaspore, and gibbsite were identified as secondary mineral phases. These results provide new information towards understanding organic species' interactions at scCO 2 –saline water–rock interfaces in deep saline aquifers.

  • Effects of Salinity and the Extent of Water on Supercritical CO2-Induced Phlogopite Dissolution and Secondary Mineral Formation
    Environmental science & technology, 2011
    Co-Authors: Hongbo Shao, Jessica R. Ray, Young-shin Jun
    Abstract:

    To ensure the viability of geologic CO2 sequestration (GCS), we need a holistic understanding of reactions at supercritical CO2 (scCO2)−saline water−rock interfaces and the environmental factors affecting these interactions. This research investigated the effects of salinity and the extent of water on the dissolution and surface morphological changes of Phlogopite [KMg2.87Si3.07Al1.23O10(F,OH)2], a model clay mineral in potential GCS sites. Salinity enhanced the dissolution of Phlogopite and affected the location, shape, size, and phase of secondary minerals. In low salinity solutions, nanoscale particles of secondary minerals formed much faster, and there were more nanoparticles than in high salinity solutions. The effect of water extent was investigated by comparing scCO2−H2O(g)−Phlogopite and scCO2−H2O(l)−Phlogopite interactions. Experimental results suggested that the presence of a thin water film adsorbed on the Phlogopite surface caused the formation of dissolution pits and a surface coating of seco...

Kamal L. Pruseth - One of the best experts on this subject based on the ideXlab platform.

  • mineralogy of the tk1 and tk4 kimberlites in the timmasamudram cluster wajrakarur kimberlite field india implications for lamproite magmatism in a field of kimberlites and ultramafic lamprophyres
    Chemical Geology, 2017
    Co-Authors: Azhar M. Shaikh, Duryadhan Behera, S C Patel, S. Ravi, Kamal L. Pruseth
    Abstract:

    Abstract A mineralogical study of the hypabyssal facies, late Cretaceous macrocrystic pulse of TK1 intrusion and the Mesoproterozoic aphanitic pulse of TK4 intrusion in the Wajrakarur Kimberlite Field of southern India shows that the rocks contain macrocrysts of forsteritic olivine, phenocrysts and microphenocrysts of Al–Na-poor diopside and Phlogopite set in a groundmass mainly of Al–Na-poor diopside and Phlogopite. Other groundmass minerals are spinel, perovskite and fluorapatite in TK1, and spinel, titanite, chlorite, calcite and gittinsite in TK4. K-richterite and perovskite occur only as inclusions in Phlogopite and titanite, respectively in TK4. Late-stage deuteric phases include pyrite and barite in TK1, and strontianite, chalcopyrite, galena and pentlandite in TK4. Diopside microphenocrysts in TK4 exhibit oscillatory zoning with characteristics of diffusion controlled magmatic growth. TK1 spinels show magmatic trend 2 that evolves from magnesiochromite and culminates in titaniferous magnetite, whereas TK4 spinels are less evolved with magnesiochromite composition only. TK1 Phlogopites show a simple compositional trend that is typical of lamproite micas, while four distinct growth zones are observed in TK4 Phlogopites with the following compositional characteristics: zone I: high Cr 2 O 3 and TiO 2 and low BaO; zone II: low Cr 2 O 3 ; zone III: low TiO 2 and high BaO; zone IV: low BaO. Forsterite contents and trace element concentrations reveal two xenocrystic core populations and one magmatic rim population for TK1 olivines. Mineralogically, both TK1 and TK4 are classified as diopside–Phlogopite lamproites rather than archetypal kimberlites. The two lamproites are considered to have formed from the same parent magma but crystallised under distinct oxygen fugacity conditions. With elevated content of Fe 3 + in Phlogopite, spinel and perovskite, TK1 appears to have crystallised in a relatively high oxygen fugacity environment. Multiple growth generations of Phlogopite, spinel and fluorapatite in TK4 indicate a complex evolutionary history of the magma. Close spatial and temporal associations of Mesoproterozoic kimberlites and lamproites in southern India can possibly be explained by a unifying model which accounts for the generation of diverse magmas from a range of geochemical resevoirs in a continental rift setting.

  • Mineralogy of the TK1 and TK4 'kimberlites' in the Timmasamudram cluster, Wajrakarur Kimberlite Field, India: Implications for lamproite magmatism in a field of kimberlites and ultramafic lamprophyres
    'Elsevier BV', 2017
    Co-Authors: Am Shaikh, S C Patel, Ravi S, Behera D, Kamal L. Pruseth
    Abstract:

    A mineralogical study of the hypabyssal fades, late Cretaceous macrocrystic pulse of TK1 intrusion and the Mesoproterozoic aphanitic pulse of TK4 intrusion in the Wajrakarur Kimberlite Field of southern India shows that the rocks contain macrocrysts of forsteritic olivine, phenocrysts and microphenocrysts of Al-Na-poor diopside and Phlogopite set in a groundmass mainly of Al-Na-poor diopside and Phlogopite. Other groundmass minerals are spinel, perovskite and fluorapatite in TK1, and spinel, titanite, chlorite, calcite and gittinsite in TK4. K-richterite and perovskite occur only as inclusions in Phlogopite and titanite, respectively in TK4. Late-stage deuteric phases include pyrite and barite in TK1, and strontianite, chalcopyrite, galena and pentlanditein TK4. Diopside microphenocrysts in TK4 exhibit oscillatory zoning with characteristics of diffusion controlled magmatic growth. TK1 spinels show magmatic trend 2 that evolves from magnesiochromite and culminates in titaniferous magnetite, whereas TK4 spinels are less evolved with magnesiochromite composition only. TK1 Phlogopites show a simple compositional trend that is typical of lamproite micas, while four distinct growth zones are observed in TK4 Phlogopites with the following compositional characteristics: zone I: high Cr2O3 and TiO2 and low BaO; zone II: low Cr2O3; zone III: low TiO2 and high BaO; zone IV: low BaO. Forsterite contents and trace element concentrations reveal two xenocrystic core populations and one magmatic rim population for TK1 olivines. Mineralogically, both TK1 and TK4 are classified as diopside-Phlogopite lamproites rather than archetypal kimberlites. The two lamproites are considered to have formed from the same parent magma but crystallised under distinct oxygen fugacity conditions. With elevated content of Fe3+ in Phlogopite, spinel and perovskite, TK1 appears to have crystallised in a relatively high oxygen fugacity environment. Multiple growth generations of Phlogopite, spinel and fluorapatite in TK4 indicate a complex evolutionary history of the magma. Close spatial and temporal associations of Mesoproterozoic kimberlites and lamproites in southern India can possibly be explained by a unifying model which accounts for the generation of diverse magmas from a range of geochemical resevoirs in a continental rift setting. (C) 2016 Elsevier B.V. All rights reserved