Amphibole Minerals Research Articles

Presentation of the Mineralogical Society of America Roebling medal for 2004 to Frances R. "Joe" Boyd

Mr. President, Margo and family, distinguished guests, and fellow mineralogists: It is indeed a great honor to be the Roebling Medal citationist, but it is also with great sadness that Joe Boyd, the recipient, is not among us to celebrate the occasion and to personally receive MSA’s most prestigious award. In nominating Joe, I was joined by a distinguished group of scientists that included Doug Smith (Texas), Dean Presnall (Texas), Peter Nixon (Leeds), Nick Sobolev (Novosibersk), and jointly by Rick Carlson, Steve Shirey, and Yingwei Fei (Carnegie), all of whom had close associations with Joe, and all of whom commented at depth on Joe’s illustrious career. Joe’s excursion into the geosciences began at Harvard (1949–1953), with rugged fieldwork on the Yellowstone pyroclastics, and experimental studies in the equally rugged environment of George Kennedy’s laboratory. Fieldwork and tightly coupled petrochemistry, backed by experiment, were hallmarks of Joe’s career, and as recognizable as his distinctive handwriting, these were signatures to each of his creative contributions. Joe’s work with George Morey at the Geophysical Laboratory in the 1950s produced the first P-T stability curve for tremolite, and solid solutions among members of the amphibole mineral group were also explored. His experimental inventiveness are marvels to behold: He was possibly the first, in 1954, to couple a heating stage to an X-ray diffractometer to record mineral transformations in action; the Boyd and England high pressure (5 GPa), and high temperature (1750°C) press, in which diamond was synthesized in 1960, can still be seen, some now modified, in many laboratories around the world. This press has advanced both the science and the careers of many a noteworthy experimentalist; Joe was the driving force in automating electron …

Petrogenesis of a Late Jurassic Peraluminous Volcanic Complex and its High-Mg, Potassic, Quenched Enclaves at Xiangshan, Southeast China

A late Mesozoic belt of volcanic–intrusive complexes occurs in SE China. Volcanic activity at Xiangshan in the NW of the belt took place mainly in the Late Jurassic (158–135Ma). The volcanic rocks from the Xiangshan volcanic complex include rhyolitic crystal tuffs, welded tuffs, rhyolite lavas, porphyritic lavas, and associated subvolcanic rocks. Mineral assemblages in these magmatic rocks include K-feldspar, plagioclase, quartz, Fe-rich biotite and minor amphibole, orthopyroxene and almandine. Mineral geothermometry indicates a high crystallization temperature (>850 C) for the Xiangshan magmas. The volcanic rocks are generally peraluminous; SiO2 contents are between 65 4% and 76 8% and the samples have high alkalis, rare earth elements (REE), high field strength elements and Ga contents and high Ga/Al ratios, but are depleted in Ba, Sr and transition metals. Trace element geochemistry and Sr–Nd–O isotope systematics imply that the Xiangshan magmas were probably derived from partial melting of Middle Proterozoic metamorphic lower-crustal rocks that had been dehydrated during an earlier thermal event. These features suggest an A-type affinity. Quenched mafic enclaves, hosted by the subvolcanic rocks, consist mainly of alkali feldspar, plagioclase, clinopyroxene, phlogopite and amphibole. Geothermometry calculations indicate that the primary magmas that chilled to form the quenched enclaves had anomalously high temperatures (>1200 C). The quenched enclaves have boninitic affinities; for example, intermediate SiO2 contents, high MgO and low TiO2 contents, high Mg-numbers and high concentrations of Sc, Ni, Co and V. However, they also have shoshonitic characteristics, e.g. enrichment in alkalis, high K2O contents with high K2O/Na2O ratios, high light REE and large ion lithophile element contents, low initial eNd values ( 4 2) and high initial Sr/Sr ratios (0 7081). We suggest a phlogopite-bearing spinel harzburgitic lithospheric mantle source for these high-Mg potassic magmas. Underplating of such anomalously high-temperature magmas could have induced granulite-facies lower-crustal rocks to partially melt and generate the Xiangshan A-type volcanic suite. A back-arc extensional setting, related to subduction of the Palaeo-Pacific plate, is favoured to explain the petrogenesis of the Xiangshan volcanic complex and quenched enclaves.

Comparison of Calidria Chrysotile Asbestos to Pure Tremolite: Final Results of the Inhalation Biopersistence and Histopathology Examination Following Short-Term Exposure

Calidria chrysotile asbestos, which is a serpentine mineral, has been shown to be considerably less biopersistent than the durable amphibole mineral tremolite asbestos, which persists once deposited in the lung. The initial results of this inhalation biopersistence study in rats that demonstrates this difference were reported in . This article presents the full results through 1 yr after cessation of the 5-day exposure. This study was based upon the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers (). In addition, the histopathological response in the lung was evaluated following exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial-grade chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and that of a long-fiber tremolite were studied. For synthetic vitreous fibers, the biopersistence of the fibers longer than 20 μm has been found to be directly related to their potential to cause disease. This study was designed to determine lung clearance (biopersistence) and the histopathological response. As the long fibers have been shown to have the greatest potential for pathogenicity, the aerosol generation technique was designed to maximize the number of long respirable fibers. The chrysotile samples were specifically chosen to have 200 fibers/cm3 longer than 20 μm in length present in the exposure aerosol. These longer fibers were found to be largely composed of multiple shorter fibrils. The tremolite samples were chosen to have 100 fibers/cm3 longer than 20 μm in length present in the exposure aerosol. Calidria chrysotile has been found to be one of the most rapidly cleared mineral fibers from the lung. The fibers longer than 20 μm in length are cleared with a half-time of 7 h. By 2 days postexposure all long fibers have dissolved/disintegrated into shorter pieces. The fibers between 5 and 20μm in length were cleared with a half-time of 7 days. This length range represents a transition zone between those fibers that can be fully phagocytosed and cleared as particles and the longer fibers that cannot be fully engulfed by the macrophage. The fibers/objects shorter than 5 μm in length were cleared with a half-time of 64 days, which is faster than that reported for insoluble nuisance dusts such as TiO2. By 12 months postexposure, 99.92% of all the remaining chrysotile was less than 5 μm in length. Following the 5 days of repeated exposure to more than 48,000 chrysotile fibers/cm3 (190 fibers L > 20 μm), histopathological examination revealed no evidence of any inflammatory reaction either after the cessation of the last exposure or at any time during the subsequent 12-mo period. This is in marked contrast to the amphibole tremolite, which was also investigated using the same inhalation biopersistence protocol. The long tremolite fibers, once deposited in the lung, remain over the rat's lifetime with essentially an infinite half-time. Even the shorter fibers, following early clearance, also remain with no dissolution or further removal. At 365 days postexposure, there was a mean lung burden was of 0.5 million fibers L > 20 μm and 7 million fibers 5–20 μm in length with a total mean lung burden of 19.6 million fibers. The tremolite exposed rats, even with exposure to 16 times fewer total fibers than chrysotile, showed a pronounced inflammatory response with the rapid development of granulomas as seen at day 1 postexposure, followed by the development of fibrosis characterized by collagen deposition within these granulomas and by 90 days even mild interstitial fibrosis. With the short exposure, this study was not designed specifically to evaluate pathological response; however, it is quite interesting that even so there was such a marked response with tremolite. These findings provide an important basis for substantiating both kinetically and pathologically the differences between chrysotile and the amphibole tremolite. As Calidria chrysotile has been certified to have no tremolite fiber, the results of the current study together with the results from toxicological and epidemiological studies indicate that this fiber is not associated with lung disease.

The Biology of Cleavage Fragments: A Brief Synthesis and Analysis of Current Knowledge

Asbestos is a commercial term referring to 6 fibrous minerals from 2 mineralogical classes: serpentine and amphibole. Chrysotile, or white asbestos, is the only serpentine mineral. The asbestiform habit of amphibole asbestos is far more toxic than chrysotile. However, most amphibole minerals are found in the “non-asbestiform” state that pose few, if any, health risks. Comminution, whether deliberate during crushing or grinding, or incidental in usage may produce structures known as “cleavage fragments” from a wide variety of sources. A considerable body of evidence, gathered over the last 30 years, demonstrates that amphibole cleavage fragments do not show the same toxicity as their asbestiform analogues. Since there still continues to be confusion and controversy on this point, this review is aimed at resolving a major portion of this controversy. It has done so by bringing together the supporting mineralogical, animal and human evidence from many sources. These observations demonstrate that cleavage fragments and amphibole asbestos fibres have fundamentally different properties and these differences are biologically relevant. Indeed, the toxicity of respirable cleavage fragments is so much less than that of the fibrous amphiboles that by any reasonable measure they are not biologically harmful.

Coalinga Chrysotile: A Short Fibre, Amphibole Free, Chrysotile: Part V - Lack of Amphibole Asbestos Contamination

Exposure to asbestos in the indoor built environment has been a concern for many years. The most common exposures in that setting are to short ultra-thin, naturally defibrillated form of fibrous asbestiform chrysotile and possibly trace amounts of short, non-asbestiform amphibole. Coalinga chrysotile is a short fibre mineral that was mined from a large ore body in California. It has been investigated in considerable detail since, although it is widely believed to be amphibole free, evidence for this has not hitherto been summarised. Analytical results from investigations that directly searched for amphiboles and geological studies from which the presence or absence of amphibole can be inferred, have indicated that Coalinga chrysotile is free of amphibole asbestos. Indeed, numerous investigations, performed over almost half a century, using a variety of techniques including the most sensitive methods, and studying many thousands of samples have failed to find any amphibole asbestos in Coalinga chrysotile. Only very rarely have non-asbestiform, “non-friable” amphibole (so-called cleavage fragment) minerals been found in the New Idria serpentine body but away from the ore zone. A large body of animal and human evidence indicates such cleavage fragments lack biological potential.

Environmental impact and geochemistry of old tailing pile from the Sanggok mine creek, Republic of Korea

This study evaluates the pollution load on a creek based on the physicochemical and mineralogical properties of old tailings. The Sanggok mine is one of the largest lead–zinc producers in the Hwanggangri mining district, Republic of Korea. The vertical profile of the old tailings in the mine area can be divided into three units based on color change, and mineralogical and textural variations, as well as physical and chemical properties. Unit I (surface accumulation and oxidized heterogeneous tailing soil) has lower pH and higher Eh than unit II (originally unoxidized dumped tailing soil) and unit III (pebble-bearing bottom soil). The conductivity data indicates that unit I and II have very high values compared to unit III and basement. The mine area consists mainly of carbonate rocks; however, mineral constituents of tailing soil and sediments near the mine were mainly composed of quartz, mica, feldspar, amphibole, calcite, dolomite, magnesite, and clay minerals. Units I and II are characterized by high abundances of siderite, locally pyrite, and dolomite. Precipitates in the mining drainage mainly included: smectite, illite, berthierine, quartz, siderite, hexahydrite, and Ca-ferrate. Among the separated metallic minerals, tailing soils and sediments of highly concentrated toxic metals are found: some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, malachite, goethite, various hydroxide, and uncertain secondary minerals. Units I and II are characterized by relatively high concentrations of Ca, Fe, Mn and low contents of Al, Mg, K, Na, Ti, rare earth elements (REEs) that correlated with the proportion of secondary minerals. Potentially toxic elements such as Ag, As, Cd, Cu, Pb, Sb, and Zn are highly enriched in the upper two units. This metal concentration can be influenced by changes in the depth because of oxic and suboxic zonal distribution. The removal zone (unit I) has probably migrated below the elevation of the maximum enrichment layer due to deepening of the oxic/suboxic boundary. In most of the materials, the enrichment index is higher than 3.62. The highest value of 42.55 is found in the oxidation surface soils of the tailing pile. An average enrichment index of the profiles and precipitates are 27.62 and 22.62, respectively. Rocky basement soils have an average enrichment index of 6.63, which is influenced by overlying the tailing pile. The water quality and habitat of the Sanggok creek are severely polluted. Polluted surface water may also negatively impact the agricultural soil and groundwater.

Mapping talc mineralisation and associated alteration using airborne and satellite-borne spectrometry: A case study at Mt Fitton, South Australia

The Mount Fitton talc deposit and associated alteration, located in the northern Adelaide Geosyncline, has been observed to have characteristic spectral signatures in the short-wave infrared and thermal infrared wavelength regions. In particular, reflectance and emissivity spectral measurements of field samples collected in the area have been shown to contain spectral absorption features diagnostic of talc, muscovite/white mica, chlorite, and amphibole minerals. Such minerals are products of the hydrothermal alteration associated with the formation of talc mineralisation. Spectral measurements of field samples also identified other minerals related to the host-rock composition, such as quartz, dolomite, calcite, magnesite and mica/illite. The distinct, and often unique, nature of these spectral signatures indicates the potential for mapping alteration and lithological units at Mount Fitton. Several airborne sensors and recently launched satellite-borne systems have acquired data in the Mount Fitton area, and these data have been processed to evaluate their ability to map the outcropping geology. In particular, the Mount Fitton test site has been used to test various remote-sensing systems with different spectral and spatial resolutions, wavelength ranges and viewing platforms, for their ability to provide useful exploration information, including the location and nature of hydrothermal alteration. Although airborne and satellite-borne multi-spectral systems successfully discriminated geological units and mineral groups, identification of talc and other alteration minerals without a priori information required hyperspectral sensors. It was also found that higher signal-to-noise, spectral resolution and access to different wavelength regions improved the mapping of talc and associated alteration. Spectrally derived mineral maps were found to provide useful supplementary information, which complements traditional airborne geophysical datasets, such as radiometrics or magnetics.

Provenance of Oligocene synorogenic sediments of the Ligurian Alps (NW Italy): inferences on belt age and cooling history

Mineral chemistry, 40Ar/39Ar geochronology on white micas and Apatite Fission Track Thermochronology (AFTT), are applied here to study the provenance of the synorogenic Molare Formation (lowermost unit of the Tertiary Piedmont Basin clastic sequence). The Molare Formation was deposited during transgression onto the Ligurian Alps nappe stack in the Early Oligocene. Depositional facies show that clastic distribution remained transversal, with local sources located just landward from the coastline. Phengite mineral chemistry together with 40Ar/39Ar data clearly shows two distinctive source areas, each one mirroring the composition of the basement directly beneath the clastic sequence. Amphibole mineral chemistry allows second order provenance distinctions within each sector, reflecting heterogeneous metamorphic evolution of the bedrock complexes. Integrated 40Ar/39Ar dating and AFTT suggest that, following a fast cooling/exhumation episode of the Ligurian Alps during the Oligocene, very little net uplift has since occurred. This is due to a period of general subsidence from the Oligocene–Late Miocene followed by comparable uplift from Late Miocene–Pliocene to the present. In general our data provide an image of the Ligurian Alps during the Oligocene, which is very similar to the present-day one.

40Ar/39Ar geochronology of the Eocene Green River Formation, Wyoming

The deposits of Eocene Lake Gosiute that constitute the Green River Formation of Wyoming contain numerous tuff beds that represent isochronous, correlatable stratigraphic markers. Tuff beds selected for 40Ar/39Ar analysis occur within laminated mudstone, are matrix supported, and lack evidence of reworking. These tuffs contain 2%–15% euhedral phenocrysts of quartz, plagioclase, sanidine, biotite, and minor amphibole, pyroxene, and zircon, encased in a matrix of altered glassy ash. Air abrasion and handpicking under refractive- index oils were required to obtain clean, unaltered phenocrysts of sanidine. 40Ar/39Ar age determinations from single-crystal and <1 mg multigrain aliquots of sanidine and biotite allowed the identification and exclusion of xenocrystic contamination. Laser-fusion experiments on phenocrysts from the Rife, Firehole, C Bed, Grey, Main, Sixth, and Analcite tuff beds from the Tipton, Wilkins Peak, and Laney Members yielded weighted-mean ages (±2σ analytical uncertainties) of 51.25 ± 0.31 Ma, 50.70 ± 0.14 Ma, 50.56 ± 0.26 Ma, 50.39 ± 0.13 Ma, 49.96 ± 0.08 Ma, 49.70 ± 0.10 Ma, and 48.94 ± 0.12 Ma, respectively. Ages for sanidine and biotite from the Main tuff are indistinguishable when presumably xenocrystic contaminants are excluded from the age calculation. Moreover, the 40Ar/39Ar ages are consistent with the stratigraphic order of the tuff beds and with provenance in the Absaroka and Challis volcanic fields. Our 40Ar/39Ar-based age model indicates that sediment accumulated three times more rapidly (327 ± 86 μm/yr) during the evaporative Wilkins Peak phase than the freshwater to saline Tipton (88 ± 34 μm/yr) and Laney (104 ± 18 μm/yr) phases. The much lower accumulation rates for the Tipton and Laney Members are permissive of an annual origin for <1-mm-thick laminae and precessional forcing of 1–3-m-thick depositional cycles in these units. However, previously described cycles in the Wilkins Peak Member have average durations that are significantly shorter than the 19–23 k.y. precessional modes. The Green River Formation encompasses an ∼5 m.y. period between ca. 53.5 and 48.5 Ma, spanning magnetic chrons 24n through 21r. The Green River Formation was therefore deposited during the warmest period of the Cenozoic corresponding to the early Eocene climatic optimum as defined by the global marine O isotope record. Deposition of bedded evaporites (trona) of the Wilkins Peak Member began at ca. 51 Ma, or ∼2 m.y. after the onset of the highest inferred temperatures of the climatic optimum. The Bridgerian–Wasatchian faunal turnover occurred subsequently during Wilkins Peak time, at ca. 50.6 Ma. Thus, our 40Ar/39Ar ages strongly suggest that Wilkins Peak evaporite deposition and the turnover from Wasatchian to Bridgerian fauna were not directly caused by the initiation of maximum greenhouse conditions.

Proterozoic blueschist-bearing mélange in the Anti-Atlas Mountains, Morocco

Blueschists from the Bou Azzer inlier provide compelling evidence for Late Proterozoic subduction in the Anti-Atlas Mountains of Morocco. High-pressure/low-temperature metabasites containing blue amphibole minerals crossite and magnesioriebeckite record pressures in excess of 5 kbar. Together with regional relationships, the geologic setting of the blueschists constrains the polarity of Pan African subduction in this region, which occurred from ∼750 to 600 Ma. Blueschist facies rocks crop out in a heterogeneous assemblage of variably deformed and metamorphosed tectonic slices of ophiolitic fragments enclosed in a schistose serpentinite matrix. The mélange belt containing the blueschist facies rocks is intruded by a number of diorite plutons, one of which has yielded a U/Pb radiometric age of 650 Ma. Together with Transaharan Belt to the southeast, the Anti-Atlas suture zone exposed within the Bou Azzer inlier contains among the oldest known blueschist-bearing, ophiolitic mélanges in the world.

Quantitative texture analysis of glaucophanite deformed under eclogite facies conditions (Sesia-Lanzo Zone, Western Alps): comparison between X-ray and neutron diffraction analysis

Abstract X-ray and neutron diffraction techniques have been applied to quantitative texture analysis of a glaucophanite from the Sesia-Lanzo Zone (Western Italian Alps), naturally deformed under eclogite facies conditions. The comparison has been carried out in order to reveal the limits and problems of texture analysis related to strongly deformed polymineralic. Different methods of measuring and computing the orientation distribution function from diffraction data have been tested, in particular X-rays, direct peak integration, and neutron diffraction using Rietveld-texture analysis. Due to grain-size problems and heterogeneity of individual amphibole minerals, neutron radiation is shown to be the best probe for characterizing the whole rock: being more penetrative than conventional X-rays, a larger volume of the mineral aggregate is sampled, giving better statistics. However, results obtained by summing the corresponding individual spectra of at least three X-ray diffraction experiments on parallel slabs of the same specimen also give statistically valid, semiquantitative results that reproduce the overall textures. The quantitative texture analysis shows the strong texture of the two generations of amphiboles (AmpI and AmpII), which are mainly characterized by [001]*-directions at an angle of about 10° to the mineral lineation and by ( hk0 ) planes describing girdles around the lineation. The texture is comparable to those described in the literature for amphibole deformed under different temperature and pressure conditions, and the pronounced asymmetry of the [001]* directions with respect to the mineral lineation is consistent with a non-coaxial component that occurs during the deformation.

The effects of temperature, pressure, and alteration on seismic properties of diabase dike rocks from DSDP/ODP Hole 504B

A 0.4 to 0.5 s−1 in situ vertical velocity gradient in the diabase dike section of DSDP/ODP Hole 504B has been attributed to the effects of increasing pressure and downhole changes of mineralogy caused by hydrothermal alteration. An analysis of velocities measured in diabase samples as a function of pressure shows that increasing pressure accounts for a gradient of at most 0.1 s−1. Neither laboratory data nor a Voigt‐Reuss‐Hill average velocity model in which Vp pyx &gt; Vp amph shows a significant variation of velocity with depth; composition and pressure combined account for a gradient not greater than 0.2 s−1. These results indicate that either the elastic moduli of the amphibole minerals in these rocks are higher than those of the pyroxene phase (Vp amph &gt; Vp pyx,) or the seismic properties of the dikes are affected by a network of thin, large‐scale cracks.

40Ar-39Ar and U-Pb ages of metadiorite from the East Kunlun Orogenic Belt: Evidence for Early-Paleozoic magmatic zone and excess argon in amphibole minerals

Single-grain zircon U-Pb and amphibole40Ar-39Ar dating have been conducted on a deformed and metamorphosed diorite in the East Kunlun Orogenic Belt, which intruded into the middle Proterozoic Kuhai Group exposed in the south of Xiangride region, Dulan County, NW Qinghai Province. The zircon gives a concordant U-Pb age of (446.5±9.1) Ma. The amphibole yields Ar plateau age of (488.0±1.2) Ma and an isochronal age of (488.9±5.6) Ma. Age results of both stepwise released Ar and conventional K-Ar analysis are remarkably higher than that of zircon U-Pb, suggesting that the amphibole contains excess argon and the amphibole plateau age cannot be taken as the timing of metamorphism or deformation. The zircon age is interpreted to be crystallization age of the diorite pluton, which suggests that an Early-Paleozoic magmatic zone indeed existed in the East Kunlun Orogenic Belt stretching along the region south to the Golmud, Normuhong and Xiangride.

Blue amphibole, Arthur Metamorphic Complex, Tasmania: Composition and regional tectonic setting

Blue amphibole minerals, including glaucophane, were formed in the Arthur Metamorphic Complex of northwest Tasmania during the early part (514–510 Ma) of the Tyennan Orogeny (514–490 Ma ∼ Delamerian Orogeny). These blue amphiboles are now a rare relict phase in the predominantly greenschist facies Bowry Formation. The hosts range from an essentially prograde metadolerite to a substantially retrograde, mafic schist. Chemical parameters of the glaucophane indicate that it formed under minimum conditions of 350°C and 700 MPa, reflecting burial in a subducted wedge. Extrusion of the Bowry Formation from the wedge, with associated re‐equilibration and deformation, commenced at 510 Ma (Early Cambrian). The formation was initially emplaced at a high crustal level, where it may have formed part of a ductile zone at the base of westward moving, upper crustal nappe of relatively unmetamorphosed Neoproterozoic to Lower Cambrian sedimentary, basaltic and ultramafic rocks. The Bowry Formation now occurs in the eastern boundary zone (Arthur Metamorphic Complex) of the Rocky Cape cratonic fragment. Other high‐pressure metamorphic rocks of approximately the same age, but of deeper crustal origin, were emplaced at middle to upper crustal levels in the Tyennan and Forth regions, to the east of the Arthur Metamorphic Complex. These rocks were exposed by middle Middle Cambrian times (506 Ma) in domes that, along with the Rocky Cape craton, controlled the arcuate form of Middle to Late Cambrian sedimentary troughs.

Hydrochemical Monitoring and Heavy Metal Contaminations at the Narim Mine Creek in the Sulcheon District, Republic of Korea

The Narim gold mine is located approximately 200 km southeast of Seoul within the Sulcheon mineralised district in the Yeongnam massif, Korea. In this study, environmental geochemical analyses were undertaken for soil, sediment and water samples collected in April, September and November in 1998 from the Narim mine creek. The mine area consists mainly of granitic gneiss; however, mineral constituents of soil and sediment near the mine were mainly composed of quartz, feldspar, mica, amphibole, some pyrite and clay minerals. Also were found some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, malachite, goethite, various hydroxide and unidentified secondary minerals. Generally, high concentrations of heavy metals in the soil and sediment are correlated with a high proportion of secondary minerals. Hydrochemical compositions of water samples are characterised by relative significant enrichment of Na+ + K+ and alkali metals in the ground water, whereas the surface and mine waters are relatively enriched in Ca2+ + Mg2+ and heavy metals. Anion contents of the ground waters are typically enriched in HCO3−, NO3− and Cl−, whereas the surface and mine waters are highly enriched in HCO3− and SO42−. The pH and EC values of the surface water from the non-mine creek are relatively lower compared with those of the surface water around the mine and waste dump. The range of δD and δ18O values (d parameters) of the water samples are shown in distinct two groups for the April waters of 10.1–13.1, and for the November waters of 5.8–7.9, respectively. This range variation indicates that two group water were composed of distinct waters because of seasonal difference. Geochemical modelling showed that mostly heavy toxic metals may exist largely in the form of free metal (M2+) and metal-sulphate (MSO42−), and SO42− concentration influenced the speciation of heavy metals in the mine water. These metals in the ground water could be formed of CO3− and OH− complex ions. Using a computer program, saturation indices of albite, calcite, dolomite in mostly surface water show undersaturated and progressively evolved toward the saturation state, however, ground and mine waters are nearly saturated. The gibbsite, kaolinite and smectite are supersaturated in the surface and ground water, respectively. Calculated water-mineral reaction and stabilities suggest that the weathering of silicate minerals may be stable kaolinite. The clay minerals of K-illite and Na-smectite will be transformed to more stable kaolinite owing to the continuous reaction.

Free radical activity of natural and heat treated amphibole asbestos

The amphibole minerals amosite and crocidolite were subjected to calcination and to hydrothermal treatment in order to study the effect of these heat treatments on the ability of the minerals to trigger formation of free radicals, which is known to be a main factor causing asbestosis and other asbestos-induced diseases. Free radical activity of the natural and heat treated minerals was studied by using supercoiled DNA (pUC18 plasmid) as a target molecule, and also by means of EPR spectroscopy. It was shown that after calcination of the natural minerals at 1073 K their free radical activity was strongly decreased These results, which may have relevant consequences for asbestos technology, were correlated with concomitant alteration of the structure and surface chemistry of the minerals during calcination.

Erosion of lithospheric mantle beneath the East African Rift system: geochemical evidence from the Kivu volcanic province

This study presents new major and trace element and Sr–Nd isotopic results for a suite of Miocene–Recent mafic lavas from the Kivu volcanic province in the western branch of the East African Rift. These lavas exhibit a very wide range in chemical and isotopic characteristics, due to a lithospheric mantle source region that is heterogeneous on a small scale, probably <1 km. The chemical and isotopic variations are mostly geographically controlled: lavas from Tshibinda volcano, which lies on a rift border fault on the northwestern margin of the province, have higher values of 87 Sr/ 86 Sr , (La/Sm) n , Ba/Nb, and Zr/Hf than the majority of Kivu (Bukavu) samples. The range of 87 Sr/ 86 Sr at Tshibinda (0.70511–0.70514) overlaps some compositions found in the neighboring Virunga province, while Bukavu group lavas include the lowest 87 Sr/ 86 Sr (0.70314) and highest ε Nd (+7.6) yet measured in western rift lavas. The Tshibinda compositions trend towards a convergence for Sr–Nd–Pb isotopic values among western rift lavas. Among Kivu lavas, variations in 143 Nd/ 144 Nd correlate with those for certain incompatible trace element ratios (e.g., Th/Nb, Zr/Hf, La/Nb, Ba/Rb), with Tshibinda samples defining one compositional extreme. There are covariations of isotopic and trace element ratios in mafic lavas of the East African Rift system that vary systematically with geographic location. The lavas represent a magmatic sampling of variations in the underlying continental lithospheric mantle, and it appears that a common lithospheric mantle (CLM) source is present beneath much of the East African Rift system. This source contains minor amphibole and phlogopite, probably due to widespread metasomatic events between 500 and 1000 Ma. Lava suites which do not show a strong component of the CLM source, and for which the chemical constraints also suggest the shallowest magma formation depths, are the Bukavu group lavas from Kivu and basanites from Huri Hills, Kenya. The inferred extent of lithospheric erosion therefore appears to be significant only beneath these two areas, which is generally consistent with lithospheric thickness variations estimated from gravity and seismic studies.

Free radical activity of mineral fibres containing adsorbed ferritin: Detection using supercoiled DNA

Mammalian ferritin was found to adsorb strongly, from aqueous solutions, onto the amphibole group minerals amosite and crocidolite. The mineral fibres containing adsorbed ferritin were found to show high free-radical activity leading to radical damage to DNA, which was quantified by electrophoretic assays with the pCSI2 plasmid. The results are discussed in terms of possible implications in the pathogenicity of asbestos bodies which are formed in vivo after inhaling mineral fibres, and which often contain endogenous ferritin in their coatings.

Geochemical and Nd isotopic compositions of the metasedimentary rocks in the La Ronge Domain, Trans-Hudson Orogen, Canada: implications for evolution of the domain

Metasedimentary rocks of greenschist to amphibolite facies occur in various belts in the Paleoproterozoic La Ronge Domain of the Trans-Hudson Orogen. Metasedimentary rocks in the Central Metavolcanic greenstone belt are low to intermediate in SiO 2 contents, have ϵ Nd values of +2.3 to +4.5, with two rare earth element (REE) patterns of (La/Yb) n <4 and >8.5, respectively. The predominant component, meta-arkoses, of the overlying McLennan Lake belt, have distinctly high K 2O and SiO 2 contents, high (La/Yb) n ratios (11–46), large negative Eu anomalies (Eu/Eu*=0.1–0.58) and uniformly low ϵ Nd values (−0.8 to +0.2). The MacLean Lake belt is comprised of a variety of metasedimentary gneisses. The volumetrically minor amphibole- and diopside-rich gneisses have high ferromagnesian element (Sc and Co) concentrations, high ϵ Nd values of +4.1 to +5.7, and flat REE patterns with no Eu anomalies. The predominant lithological unit in the MacLean Lake belt, the psammitic gneisses, is geochemically more variable. The mafic psammitic gneiss samples in the MacLean Lake belt and the metasedimentary rocks in the Central Metavolcanic belt are similar in trace and major element geochemistry and Nd isotope composition, whereas those more felsic psammitic gneisses are similar to the McLennan Lake meta-arkoses. Geochemical data, combined with lithological and geochronological evidence, indicate that sediments in the Central Metavolcanic belt were derived mainly from contiguous volcanic debris, with minor addition of felsic components from exotic sources. In contrast, the McLennan Lake meta-arkoses were derived from a distinct felsic source, whereas the psammitic gneisses in the MacLean Lake belt are mixtures of volcanic materials in the Central Metavolcanic belt and meta-arkoses-like felsic components. Nd isotopic data and ages of detrital zircon suggest that Proterozoic juvenile materials were dominant sources for metasedimentary rocks in the La Ronge Domain. Comparison of geochemical signatures of the metasedimentary rocks with those of the felsic plutonic rocks in the Central Metavolcanic belt suggests that the felsic materials in the McLennan Lake and MacLean Lake belts could not have been derived predominantly from the plutonic rocks, implying more distal sources. Topographic changes during collision may have resulted in a shift from mixing of both local and distal sources for the rocks in the MacLean Lake belt, to the dominance of a more distal source for the McLennan Lake meta-arkoses.

Multiphase Melt Inclusions in the Jinchuan Complex, China: Implications for Petrogenic and Metallogenic Physico-Chemical Conditions

Three types of melt inclusions were identified in pyroxenes, olivine, and chromite from the Jinchuan intrusion–sulfide inclusions (I), crystallized polyphase inclusions (II), and fluid inclusions (III). Sulfide inclusions in chromite are spherical and occur parallel to chromite growth planes. Polyphase inclusions are found in olivine and consist of olivine, orthopyroxene, chrome-spinel, amphibole, and sulfide daughter minerals. Primary fluid inclusions are usually found in olivine and pyroxene with spherical to tubular shapes. Laser Raman analyses were used to identify daughter minerals and fluid phases in the inclusions. The result shows that fluids consist mainly of CO2, with minor amounts of SO2, H2S, and CH4. This indicates that the parental magma of the Jinchuan intrusion contains abundant volatiles. Microthermometry shows that Type-II inclusions in dunite and sulfide-rich lherzolite have higher trapping temperatures (1000° to 1050°C), whereas trapping temperatures in sulfide-poor lherzolite are lower (900° to 950°C). The result of low-temperature microthermomentry indicates that the CO2 homogenization temperatures of +10° to +15°C correspond to depths of 12.9 to 15 km (deep-level magma chamber) and the homogenization temperatures of +26° to +29°C correspond to depths of 6.9 to 9.3 km (upper magma chamber). The immiscible sulfide in the inclusions demonstrates that segregation of the sulfide melt occurs at an early stage during magmatic differentiation.