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Mickey E Gunter - One of the best experts on this subject based on the ideXlab platform.
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Amphibole asbestos soil contamination in the u s a a matter of definition
American Mineralogist, 2011Co-Authors: Brittani D Thompson, Mickey E Gunter, Michael A WilsonAbstract:Recent concerns surrounding asbestos exposure have extended from occupational settings into natural settings. These developments have caused us to examine the distribution of Amphiboles, which are potential asbestiform minerals, within the soils of the U.S.A. Evaluation of mineralogical data from selected sand and/or silt fraction of soils from the USDA-NRCS National Cooperative Soil Survey database shows that soils in all states (except for Rhode Island) contain Amphiboles. In 41 of the 50 states, 10% or more sampled pedons contain Amphiboles. Overall, 4396 pedons out of the 34 326 pedons (about 13%) sampled in the U.S.A. contained Amphiboles. Pedons containing Amphiboles ranged from less than 1 to 49% of the pedons among all states. While Amphibole asbestos deposits occur in mafic and ultramafic provinces, soil Amphiboles occur evenly distributed across the U.S.A. The majority of the Amphiboles found in the soils would likely not meet the mineralogical definition of asbestos (i.e., they would not have been derived from asbestiform Amphiboles); however, the majority would likely meet a commonly used regulatory definition of a fiber (i.e., are over 5 μm in length with a greater than 3 to 1 aspect ratio). Based on the regulatory definition, 13% of soil pedons and 5% of soil horizons in the U.S.A. are “naturally contaminated.”
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a review of scientific literature examining the mining history geology mineralogy and Amphibole asbestos health effects of the rainy creek igneous complex libby montana usa
Inhalation Toxicology, 2006Co-Authors: Bryan R Bandli, Mickey E GunterAbstract:This article reviews the past 90 yr of scientific research directed on multiple aspects of the unique geology and environmental health issues surrounding the vermiculite deposit found at Libby, MT. Hydrothermal alteration and extensive weathering of the ultramafic units resulted in the formation of a rich deposit of vermiculite that was mined for 67 yr and used in numerous consumer products in its expanded form. Later intrusions of alkaline units caused hydrothermal alteration of the pyroxenes, resulting in formation of Amphiboles. Some of these Amphiboles occur in the asbestiform habit and have been associated with pulmonary disease in former miners and mill workers. Identification of these Amphibole asbestos minerals has received little attention in the past, but recent work shows that the majority of the Amphibole mineral species present may not be any of the Amphibole species currently regulated by government agencies. Epidemiological studies on former miners have, nevertheless, shown that the Amphibole asbestos from the Rainy Creek igneous complex is harmful; also, a recent study by the Agency for Toxic Substances and Disease Registry shows that residents of Libby who had not been employed in the vermiculite mining or milling operations also appear to have developed asbestos-related pulmonary diseases at a higher rate than the general public elsewhere. Since November 1999, the U.S. Environmental Protection Agency has been involved in the cleanup of asbestos-contaminated sites in and around Libby associated with the mining and processing of vermiculite.
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a review of scientific literature examining the mining history geology mineralogy and Amphibole asbestos health effects of the rainy creek igneous complex libby montana usa
Inhalation Toxicology, 2006Co-Authors: Bryan R Bandli, Mickey E GunterAbstract:This article reviews the past 90 yr of scientific research directed on multiple aspects of the unique geology and environmental health issues surrounding the vermiculite deposit found at Libby, MT. Hydrothermal alteration and extensive weathering of the ultramafic units resulted in the formation of a rich deposit of vermiculite that was mined for 67 yr and used in numerous consumer products in its expanded form. Later intrusions of alkaline units caused hydrothermal alteration of the pyroxenes, resulting in formation of Amphiboles. Some of these Amphiboles occur in the asbestiform habit and have been associated with pulmonary disease in former miners and mill workers. Identification of these Amphibole asbestos minerals has received little attention in the past, but recent work shows that the majority of the Amphibole mineral species present may not be any of the Amphibole species currently regulated by government agencies. Epidemiological studies on former miners have, nevertheless, shown that the amphibo...
Bryan R Bandli - One of the best experts on this subject based on the ideXlab platform.
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a review of scientific literature examining the mining history geology mineralogy and Amphibole asbestos health effects of the rainy creek igneous complex libby montana usa
Inhalation Toxicology, 2006Co-Authors: Bryan R Bandli, Mickey E GunterAbstract:This article reviews the past 90 yr of scientific research directed on multiple aspects of the unique geology and environmental health issues surrounding the vermiculite deposit found at Libby, MT. Hydrothermal alteration and extensive weathering of the ultramafic units resulted in the formation of a rich deposit of vermiculite that was mined for 67 yr and used in numerous consumer products in its expanded form. Later intrusions of alkaline units caused hydrothermal alteration of the pyroxenes, resulting in formation of Amphiboles. Some of these Amphiboles occur in the asbestiform habit and have been associated with pulmonary disease in former miners and mill workers. Identification of these Amphibole asbestos minerals has received little attention in the past, but recent work shows that the majority of the Amphibole mineral species present may not be any of the Amphibole species currently regulated by government agencies. Epidemiological studies on former miners have, nevertheless, shown that the Amphibole asbestos from the Rainy Creek igneous complex is harmful; also, a recent study by the Agency for Toxic Substances and Disease Registry shows that residents of Libby who had not been employed in the vermiculite mining or milling operations also appear to have developed asbestos-related pulmonary diseases at a higher rate than the general public elsewhere. Since November 1999, the U.S. Environmental Protection Agency has been involved in the cleanup of asbestos-contaminated sites in and around Libby associated with the mining and processing of vermiculite.
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a review of scientific literature examining the mining history geology mineralogy and Amphibole asbestos health effects of the rainy creek igneous complex libby montana usa
Inhalation Toxicology, 2006Co-Authors: Bryan R Bandli, Mickey E GunterAbstract:This article reviews the past 90 yr of scientific research directed on multiple aspects of the unique geology and environmental health issues surrounding the vermiculite deposit found at Libby, MT. Hydrothermal alteration and extensive weathering of the ultramafic units resulted in the formation of a rich deposit of vermiculite that was mined for 67 yr and used in numerous consumer products in its expanded form. Later intrusions of alkaline units caused hydrothermal alteration of the pyroxenes, resulting in formation of Amphiboles. Some of these Amphiboles occur in the asbestiform habit and have been associated with pulmonary disease in former miners and mill workers. Identification of these Amphibole asbestos minerals has received little attention in the past, but recent work shows that the majority of the Amphibole mineral species present may not be any of the Amphibole species currently regulated by government agencies. Epidemiological studies on former miners have, nevertheless, shown that the amphibo...
Natsumi Hokanishi - One of the best experts on this subject based on the ideXlab platform.
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evidence for a third endmember of the unzen 1991 1995 eruption from Amphibole thermometry and crystal clots
Journal of Volcanology and Geothermal Research, 2020Co-Authors: Kurumi Iwahashi, Hidemi Ishibashi, Atsushi Yasuda, Natsumi HokanishiAbstract:Abstract Amphibole phenocrysts and crystal clots composed of Amphibole, plagioclase, and interstitial glass were observed in dacitic products of the Unzen 1991–1995 eruption and analyzed in order to understand pre-eruptive magmatic processes. Amphibole phenocrysts in the samples erupted at different times are classified by composition as either magnesiohornblendes or tschermakites. Temperatures of 770–830 °C are estimated from magnesiohornblende phenocrysts and Amphiboles in the crystal clots, which are consistent with the proposed temperature of the silicic endmember magma. The average approximate composition of the interstitial melt is 67–73 wt% SiO2, ~0.25 wt% TiO2, ~12 wt% Al2O3, ~1.1 wt% FeO, 0.14 wt% MgO, 0.80 wt% CaO, 3.0 wt% Na2O, and 4.0 wt% K2O. The SiO2 plus H2O content (~8.8 wt%) of the melt estimated from these Amphiboles (SiO2melt = 71–72 wt%) is consistent with the compositions of interstitial melts observed in the crystal clots. The H2O saturation depth estimated for the interstitial melt and plagioclase compositions is consistent with that of the magma chamber where the silicic endmember magma was likely stored (11–15 km). These results suggest that interstitial melts in crystal clots represent the silicic endmember melt. Temperatures estimated from tschermakite phenocrysts are 870–950 °C, which is lower than the proposed temperature of the mafic endmember magma. In addition, a temperature gap is observed between the tschermakites and magnesiohornblendes. These results suggest the contribution of a previously unrecognized third endmember magma to the 1991–1995 magma, which we term the mid-temperature magma (MT magma).
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Amphibole melt disequilibrium in silicic melt of the aso 4 caldera forming eruption at aso volcano sw japan
Earth Planets and Space, 2018Co-Authors: Hidemi Ishibashi, Yukiko Suwa, Atsushi Yasuda, Masaya Miyoshi, Natsumi HokanishiAbstract:The most recent and largest caldera-forming eruption occurred at ~ 90 ka at Aso Volcano, SW Japan, and is known as the “Aso-4 eruption.” We performed chemical analyses of Amphibole phenocrysts from Aso-4 pyroclasts collected from the initial and largest pyroclastic unit (4I-1) of the eruption to infer the composition–temperature–pressure conditions of the melt that crystallized Amphibole phenocrysts. Each Amphibole phenocryst is largely chemically homogeneous, but inter-grain chemical variation is observed. Geothermometry, geobarometry, and melt–SiO2 relationships based on Amphibole single-phase compositions reveal that most Amphibole phenocrysts were in equilibrium with hydrous melt comprising ~ 63–69 wt% SiO2 ( $${\text{SiO}}_{2}^{\text{melt}}$$ ) at 910–950 °C, although several grains were crystallized from more mafic and higher-temperature melts (~ 57–60.5 wt% SiO2 and 965–980 °C). The Amphibole temperatures are comparable with those previously estimated from two-pyroxene geothermometry, but are much higher than temperatures previously estimated from Fe–Ti oxide geothermometry. The estimated $${\text{SiO}}_{2}^{\text{melt}}$$ contents are lower than that of the host melt in the 4I-1 pyroclasts. Chemical and thermal disequilibrium between the Amphibole rims and the host melt, as well as intra-grain homogeneity and inter-grain heterogeneity of Amphibole compositions, suggests that these Amphiboles were incorporated into the host melt immediately prior to the caldera-forming eruption. Our results suggest that the Amphibole phenocrysts, and perhaps some of the pyroxene and plagioclase phenocrysts, were derived from a chemically and thermally zoned crystal mush layer that had accumulated beneath the chamber of the host 4I-I melt. Amphibole geobarometry indicates a crystallization depth of ~ 13.9 ± 3.5 km, which is consistent with the present-day magma chamber depth beneath the volcano as inferred from geophysical observations. The results suggest that the depth of the post-caldera magma plumbing system is strongly influenced by a relic magma reservoir related to a previous caldera-forming eruption.
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Amphibole–melt disequilibrium in silicic melt of the Aso-4 caldera-forming eruption at Aso Volcano, SW Japan
'Springer Science and Business Media LLC', 2018Co-Authors: Hidemi Ishibashi, Yukiko Suwa, Atsushi Yasuda, Masaya Miyoshi, Natsumi HokanishiAbstract:Abstract The most recent and largest caldera-forming eruption occurred at ~ 90 ka at Aso Volcano, SW Japan, and is known as the “Aso-4 eruption.” We performed chemical analyses of Amphibole phenocrysts from Aso-4 pyroclasts collected from the initial and largest pyroclastic unit (4I-1) of the eruption to infer the composition–temperature–pressure conditions of the melt that crystallized Amphibole phenocrysts. Each Amphibole phenocryst is largely chemically homogeneous, but inter-grain chemical variation is observed. Geothermometry, geobarometry, and melt–SiO2 relationships based on Amphibole single-phase compositions reveal that most Amphibole phenocrysts were in equilibrium with hydrous melt comprising ~ 63–69 wt% SiO2 ($${\text{SiO}}_{2}^{\text{melt}}$$ SiO2melt ) at 910–950 °C, although several grains were crystallized from more mafic and higher-temperature melts (~ 57–60.5 wt% SiO2 and 965–980 °C). The Amphibole temperatures are comparable with those previously estimated from two-pyroxene geothermometry, but are much higher than temperatures previously estimated from Fe–Ti oxide geothermometry. The estimated $${\text{SiO}}_{2}^{\text{melt}}$$ SiO2melt contents are lower than that of the host melt in the 4I-1 pyroclasts. Chemical and thermal disequilibrium between the Amphibole rims and the host melt, as well as intra-grain homogeneity and inter-grain heterogeneity of Amphibole compositions, suggests that these Amphiboles were incorporated into the host melt immediately prior to the caldera-forming eruption. Our results suggest that the Amphibole phenocrysts, and perhaps some of the pyroxene and plagioclase phenocrysts, were derived from a chemically and thermally zoned crystal mush layer that had accumulated beneath the chamber of the host 4I-I melt. Amphibole geobarometry indicates a crystallization depth of ~ 13.9 ± 3.5 km, which is consistent with the present-day magma chamber depth beneath the volcano as inferred from geophysical observations. The results suggest that the depth of the post-caldera magma plumbing system is strongly influenced by a relic magma reservoir related to a previous caldera-forming eruption
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magma reservoir conditions beneath tsurumi volcano sw japan evidence from Amphibole thermobarometry and seismicity
Lithos, 2017Co-Authors: Shiho Nagasaki, Hidemi Ishibashi, Yukiko Suwa, Atsushi Yasuda, Natsumi Hokanishi, Takahiro Ohkura, Keiji TakemuraAbstract:Abstract Calcic Amphibole phenocrysts in the Tsurumidake summit (TS) lava, which was produced during the most recent eruption at Tsurumi Volcano (SW Japan) at around 7.5–10.5 ka, have been analyzed to determine the pre-eruptive conditions, such as temperature (T), pressure (P), oxygen fugacity (fO2), SiO2 content (SiO2melt), and FeO*/MgO ratio (FeO*/MgOmelt), of coexisting silicate melts in the magma reservoir beneath the volcano. Although most of the Amphibole phenocrysts have been completely decomposed to a fine-grained opaque symplectite, ~ 6% of the grains remain intact. The degree of Amphibole breakdown (DAB), defined as the ratio of the area of symplectite to the area of symplectite plus relict Amphibole in each phenocryst, varies from ~ 20% to 100%. Compositional zoning was not observed in the Amphibole grains, however, two distinct groups of Amphibole phenocrysts have been identified based on their chemical compositions: group-I Amphiboles, which are relatively Si-poor, and [6]Al-rich, and have a relatively high Mg# [100Mg/(Mg + Fe2 +)]; and group-II Amphiboles, which are Si-rich, and [6]Al-poor, and have a relatively low Mg#. Empirical equations for geothermobarometry, oxygen barometry and chemometry that exclusively rely on the Amphibole composition were applied to estimate the T–P–fO2–SiO2melt–FeO*/MgOmelt conditions of the silicate melts with which the Amphibole crystals equilibrated. The results show that group-I and group-II Amphiboles equilibrated with andesitic melts (group-I melts) and dacitic–rhyolitic melts (group-II melts), respectively. The T–P–fO2 conditions of group-I melts were estimated as ~ 374–483 MPa (~ 13.9–17.9 km depth), ~ 950 °C, and NNO + 1.3, respectively, and those of group-II melts were ~ 93–242 MPa (~ 3.4–9.0 km depth), 824–913 °C, and NNO + 0.6–1.7, respectively. The estimated T–P–fO2–SiO2melt–FeO*/MgOmelt conditions were almost constant for group-I melts, whereas the T, ΔNNO, and FeO*/MgOmelt values of group-II melts decreased with increasing SiO2melt. The DAB decreased as the temperature increased; low-DAB grains are absent in group-II Amphiboles. Our results suggest that (1) a deeper reservoir (at a depth of ~ 16 km) stored an andesitic melt coexisting with group-I Amphiboles at ~ 950 °C; (2) a chemically zoned reservoir at shallower depth (~ 6.4 km) was filled with dacitic–rhyolitic melts that coexisted with group-II Amphiboles at ~ 824–913 °C; (3) the TS lava was the product of magma mixing of at least three components, including the andesitic melt derived from the deeper reservoir, the dacitic and rhyolitic melts from the shallower reservoir and a mafic magma derived from the lower crust and/or upper mantle; and (4) the TS lava eruption occurred within a month or less of the magma mixing.
Mark A Kendrick - One of the best experts on this subject based on the ideXlab platform.
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halogens in altered ocean crust from the east pacific rise odp iodp hole 1256d
Geochimica et Cosmochimica Acta, 2019Co-Authors: Mark A KendrickAbstract:Abstract The halogens (F, Cl, Br and I), H2O and CO2 were investigated in eighteen representative lavas, dykes and a gabbro spanning depths 750–1450 mbsf in the International Ocean Discovery Project (IODP) Hole 1256D. Whole rock analyses of halogens, H2O and CO2, and in situ F and Cl electron microprobe analyses were combined to provide new information about hydrothermal alteration of the ocean crust and the mineral controls on the abundances of all four halogens in altered ocean crust that is subducted into the mantle. Whole rock concentrations of halogens, H2O and CO2 are heterogeneous at all crustal levels with maxima in highly altered zones of fluid infiltration. Nonetheless, Cl and Br show a general increase down the hole from minima of 130 ppm Cl and 330 ppb Br in the lavas, with dominant saponite-chlorite alteration, to maxima of 1620 ppm Cl and 2720 ppb Br in amphibolite facies granoblastic dykes and the gabbros near the base of the hole. In contrast, H2O concentrations of 1.5–2 wt% were common in clay-rich (saponite) alteration with lower values in the deeper Amphibole-rich samples. The concentrations of F (130–300 ppm), I (6–25 ppb) and CO2 (0.13–0.43 wt.%) do not show any obvious relationship to depth. The altered lavas, dykes and gabbros are enriched in Cl, Br, I and H2O by ∼2–20 times, but have F concentrations similar to uncontaminated fresh N-MORB glasses from the East Pacific Rise. The majority of Amphiboles analysed in this and previous studies have low F/Cl ratios that are typical of hydrothermal Amphiboles formed from F-poor seawater-derived fluids. The most Cl-rich Amphiboles in the deepest gabbro typically contain ∼2000–4000 ppm Cl, but a patch of Amphibole with 1.6 wt.% Cl was found close to a chlorapatite. Together the Cl-rich Amphibole and hydrothermal chlorapatite, with up to 5.4 wt.% Cl, provide evidence for high salinity seawater-derived brines (∼50 wt.% salts) at the base of the hole. In addition a population of F-rich Amphiboles (>1000 ppm F) with elevated F/Cl ratios (F/Cl ∼ 6–8) provide evidence for the passage of F-rich magmatic fluids in the granoblastic dykes and gabbros. Hydrous silicates including saponite-chlorite at the top of the hole and Amphibole below 1300 mbsf, typically accommodate most of the F and Cl (e.g. 20–60%) in whole rock samples. Apatite accommodates a further
Stephen F Foley - One of the best experts on this subject based on the ideXlab platform.
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trace element partitioning between Amphibole and silicate melt
Reviews in Mineralogy & Geochemistry, 2007Co-Authors: Massimo Tiepolo, Roberta Oberti, Alberto Zanetti, R Vannucci, Stephen F FoleyAbstract:Knowledge of the partitioning behavior of trace elements between solid and liquid is a prerequisite for modern igneous and mantle petrology. Most of the mathematical models simulating melt generation, migration and evolution within the mantle and/or the crust require the availability of reliable solid/liquid partition coefficients for the mineral phases involved in the process. Calcic Amphiboles are extremely important for the understanding of lithospheric processes because of both their common occurrence in a variety of igneous and metamorphic rocks types and their capability of hosting a large number of geochemically important trace elements. A series of studies on the partitioning behavior of trace elements between calcic Amphibole and silicate melt have therefore been carried out at different pressures, temperatures and system compositions during the last 15 years. However, due to the complex crystal chemistry of Amphiboles, only few studies focused on the role of crystal structure and composition on Amphibole-liquid partition coefficients (Amph/LD). In this chapter, present knowledge of the solid/ liquid trace element partitioning between calcic Amphiboles and silicate melt is summarized and the role played by the crystal structure and melt composition on Amph/LD variations is highlighted in addition to the effects of pressure and temperature. The dataset used in this chapter includes only the results of experimental studies performed under well constrained P - T conditions for which trace element determinations were carried out with highly sensitive in situ microanalytical techniques. The available dataset considered in this work are listed in Table 1⇓. Although far less common than the calcic Amphiboles, potassic-richterites are potentially important in the generation of potassic magmatic rocks and in re-enrichment processes occurring in the subcontinental mantle lithosphere sampled as xenoliths in kimberlites. A comprehensive experimental study of trace element partitioning between synthetic potassic richterites and silicate melts has …
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partitioning of rare earth elements y th u and pb between pargasite kaersutite and basanite to trachyte melts implications for percolated and veined mantle
Geochemistry Geophysics Geosystems, 2000Co-Authors: Massimo Tiepolo, Roberta Oberti, Alberto Zanetti, Riccardo Vannucci, P Bottazzi, Stephen F FoleyAbstract:[1] A new set of partitioning data for rare earth elements (REE: La, Ce, Nd, Sm, Eu, Gd, Dy, Er, and Yb), Y, Th, U, and Pb has been obtained for 25 calcic Amphiboles (pargasites and kaersutites) crystallized from alkali-basaltic and basanitic bulk rock compositions at pressure P = 1.4 GPa, and temperature T between 950° and 1075°C. The variations of Amphibole/liquid partition coefficients and of their ratios relevant to petrogenetic studies are discussed with reference to the major element composition of the Amphiboles and of the coexisting melt, and to the crystal chemical mechanisms for trace element incorporation. Our results support the conclusions that REE and actinides are incorporated into the M4 cavity in calcic Amphiboles and distributed between the two available sites within that cavity and that Pb is incorporated into the A site. In our sample population, REE patterns are systematically enriched in heavy REE (HREE), as expected from the presence of significant cummingtonite component. No significant fractionation is observed between Th and U. The major factor controlling the amount of trace element incorporation is the SiO2 content of the melt. The major implication of this study is that HREE can become compatible in Amphibole in systems with SiO2 content greater than ∼50 wt %, whereas LREE always remain incompatible. We use the new DREEamph/l values to calculate the effects of Amphibole crystallization during melt migration in the upper mantle by reactive porous flow as well as fractional crystallization of Amphibole during melt migration in veined systems. We show that both processes will lead to residual liquids and solids with extremely variable LaN/YbN ratios.
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nb and ta incorporation and fractionation in titanian pargasite and kaersutite crystal chemical constraints and implications for natural systems
Earth and Planetary Science Letters, 2000Co-Authors: Massimo Tiepolo, Roberta Oberti, Stephen F Foley, Riccardo Vannucci, P Bottazzi, Alberto ZanettiAbstract:New partition coefficients between liquid and pargasitic/kaersutitic Amphiboles (Amph/LDNb,Ta) experimentally determined for Nb and Ta at upper-mantle conditions, combined with single-crystal structure refinement of the synthesised Amphiboles, show that Amph/LDNb,Ta are strongly dependent on the structure and composition of both Amphibole and melt. The correlation of the Amph/LDNb,Ta with the Amphibole oxy-component is explained by the ordering of Nb and Ta at the M1 site, contributing with the fraction of Ti at M1 to locally balance the O3O2−↔O3(OH)− substitution. In our set of dehydrogenated Amphiboles, variations in the SiO2 content of the melt from 41.5 to 54.6 correspond to a six-fold increase of the Amph/LDNb,Ta, in which Amph/LDNb varies from 0.14 to 0.71 and Amph/LDTa from 0.11 to 0.54. Partition coefficients for Nb and Ta abruptly increase in Ti-depleted compositions (Amph/LDNb up to 1.63 and Amph/LDTa to 1.00). The ratio of DNb to DTa (Amph/LDNb/Ta) varies from 0.71 to 1.63, and is a function of the M1 site dimension, which in turn depends on its Fe, Mg and Ti contents. The observed variations can be explained by assuming that the ionic radius of Nb is (∼0.01–0.02 A) larger than that of Ta, contrary to the common assumption that they are both equal to 0.64 A. We calibrated a simplified model for the prediction of Amph/LDNb/Ta values shown to be negatively related mainly to mg# [Mg/(Mg+Fe)] and to Ti content. High-mg# Amphiboles have Amph/LDNb/Ta close to unity, so the low Nb/Ta found in convergent margin volcanics and in the continental crust cannot be explained by the involvement of Amphibole in the mantle wedge. Amphibole in the subducting slab may have lower mg# and consequently high Nb/Ta values, and thus may give rise to subchondritic Nb/Ta values in coexisting melts. Nb/La is also negatively correlated with mg#, and strongly increases in Ti-depleted compositions.