Ian M. Steele

A mesothelioma epidemic in Cappadocia: scientific developments and unexpected social outcomes

In Cappadocia, Turkey, an unprecedented mesothelioma epidemic causes 50% of all deaths in three small villages. Initially linked solely to the exposure to a fibrous mineral, erionite, recent studies by scientists from Turkey and the United States have shown that erionite causes mesothelioma mostly in families that are genetically predisposed to mineral fibre carcinogenesis. This manuscript reports, through the eyes of one of the researchers, the resulting scientific advances that have come from these studies and the social improvements that were brought about by both the scientists and members of the Turkish Government.

Amoeboid olivine aggregates in the Allende meteorite

Greyish-brown, irregularly-shaped aggregates composed predominantly of olivine make up ~2% of the Allende meteorite by volume. Many of the aggregates are constructed of subspherical lumps of micron-sized crystals of olivine, pyroxene, nepheline and sodalite surrounded by coarsergrained olivine. Rarely, anorthite, spinel and perovskite are also present. The olivine ranges in composition from Fo64 to Fo99. Pyroxenes range from aluminous diopside to hedenbergite to very Al-rich and Ti-Al-rich varieties. The nepheline contains 1.6–2.4% K2O and 1.6–5.2% CaO but the sodalite is significantly poorer in these elements. The spinel contains 2.1–13.4% FeO. Textural information and oxygen isotopic data suggest that the aggregates are composed of primary, solid condensates from the solar nebula. The perovskite. spinel and Ti-Al-rich pyroxenes are the remains of high-temperature condensates but the olivine compositions and the presence of feldspathoids indicate that some of the grains continued to react with the solar nebular vapor in the temperature range 500–900°K.

Erionite exposure in North Dakota and Turkish villages with mesothelioma

Exposure to erionite, an asbestos-like mineral, causes unprecedented rates of malignant mesothelioma (MM) mortality in some Turkish villages. Erionite deposits are present in at least 12 US states. We investigated whether increased urban development has led to erionite exposure in the United States and after preliminary exploration, focused our studies on Dunn County, North Dakota (ND). In Dunn County, ND, we discovered that over the past three decades, more than 300 miles of roads were surfaced with erionite-containing gravel. To determine potential health implications, we compared erionite from the Turkish villages to that from ND. Our study evaluated airborne point exposure concentrations, examined the physical and chemical properties of erionite, and examined the hallmarks of mesothelial cell transformation in vitro and in vivo. Airborne erionite concentrations measured in ND along roadsides, indoors, and inside vehicles, including school buses, equaled or exceeded concentrations in Boyali, where 6.25% of all deaths are caused by MM. With the exception of outdoor samples along roadsides, ND concentrations were lower than those measured in Turkish villages with MM mortality ranging from 20 to 50%. The physical and chemical properties of erionite from Turkey and ND are very similar and they showed identical biological activities. Considering the known 30- to 60-y latency for MM development, there is reason for concern for increased risk in ND in the future. Our findings indicate that implementation of novel preventive and early detection programs in ND and other erionite-rich areas of the United States, similar to efforts currently being undertaken in Turkey, is warranted.

Microanalysis of oxygen isotopes in insulators by secondary ion mass spectrometry

Microanalyses for oxygen isotopes of insulating samples in polished thin sections have been achieved using a commercially available secondary ion mass spectrometer equipped with an auxiliary high voltage electron flood gun and modified to allow the detection of secondary ions sputtered with initial kinetic energies up to 4500eV. A Cs+ primary ion beam enhanced the negative secondary ion signal. Sample charging was controlled by use of the electron gun (impact energy ≈ 3.4 keV). Secondary ions with > 300 eV initial energy sputtered from a range of silicate minerals do not show detectable variations in instrumental fractionation over a range of tens of electronvolts, providing immunity to variations in sample charging. In addition, the interference of 16OH− on 17O− is effectively eliminated from the mass spectrum at these energies, allowing the measurement of all three oxygen isotopes at low mass resolution. Analytical precision is limited by counting statistics and the depth of the sputtered crater to ≈ ±1% (1σ) for 18/16 ratios. If 17/16 ratios are also desired, it is possible to select count times to achieve ≈ ±2% precision for both.

Compositions and textures of relic forsterite in carbonaceous and unequilibrated ordinary chondrites

Several percent of the olivine in the C2, C3 and unequilibrated ordinary chondrites (UOC) can be distinguished by blue cathodoluminescence (CL) and an unusual composition for forsterite. This olivine has the following textural features: 1. (1) forms cores in single olivine grains; 2. (2) shows subhedral to euhedral boundaries against rim olivine; 3. (3) rarely contains inclusions; 4. (4) has embayments containing olivine like that of the rim; 5. (5) occurs within chondrules especially in UOC meteorites. The blue olivine is always Fe-poor (0.25 < FeO < 1.0%) and shows the following average and maximum values (%): Al2O3 (0.25, 0.5), TiO2 (0.05, 0.09), CaO (0.5, 0.8), Cr2O3 (0.15, 0.5), and MnO (0.02, 0.15); vanadium is present. Within a single olivine and within all blue olivines Al, Ca and Ti are strongly positively correlated as are Mn, Fe, and Cr in olivine surrounding the blue. The blue cores are not zoned but each element shows a marked change at the boundary of the blue with Al showing the most rapid change. These are interpreted as diffusion profiles between rim and core olivine. Textures suggest initial free growth probably from a gas and later addition of olivine by liquid crystallization to form single crystals or chondrules. The unusual olivine composition indicates high temperature growth from a refractory-rich reservoir with Al entering olivine in tetrahedral coordination. Vapor growth is suggested as the process allowing the high minor element levels. The occurrence of blue olivine in all primitive meteorites indicates that it is relic material which was widespread prior to chondrule and hence meteorite formation. Similarities in composition exist between this relic olivine and olivine of cosmic dust and Deep Sea Particles pointing to this olivine being a common component in all primitive extraterrestrial material.

Zoned quartz phenocrysts from the rhyolitic Bishop Tuff

Abstract Cathodoluminescence (CL) reveals growth zones in quartz phenocrysts from the rhyolitic Bishop Tuff. Melt inclusions occur in various zones and record the evolving melt composition during zonal growth. The zones form an oscillatory pattern between bright and dark CL quartz. There are three recognizable patterns of CL zoning in these crystals: (1) weakly zoned cores and bright CL rims; (2) weakly zoned cores and dark CL rims; and (3) no CL intensity difference from core to rim. Dark CL quartz generally occurs at crystal edges, contains most of the melt inclusions and is interpreted as fast-growing. Zones that occur along recognizable crystal edges (edge zones) are thicker than the same zone on adjacent faces, consistent with relatively fast growth of these zones. In each successive zone, these edge zones decrease in size toward the rim, while the zones along the crystal faces increase. Some of the melt inclusions have bright CL quartz locally associated with them. This is interpreted as the postentrapment crystallization of slow-growing quartz in the melt inclusions. Many crystals display zone discordance from the weakly zoned interiors to the rims. Most of the discordant surfaces are rational and probably are primary growth features. Pumice clasts from the southern vents are largely compositionally and texturally distinct from those from the northern vents, and this distinction is also evident in the quartz CL. The crystals that have bright CL rims are all associated with the late-erupted northern part of the Bishop Tuff. Melt inclusion compositions and CL zoning patterns suggest a common origin for early and middle-erupted quartz and the interior zones of late-erupted quartz; however, the bright CL rim on the late-erupted quartz indicates an additional stage of crystallization in late-erupted magma. Melt inclusions in individual early erupted crystals have small variations in Ba whereas inclusions in late-erupted crystals markedly increase in Ba toward the rim, which is opposite to the normal zoning of sequentially trapped melts expected during closed system crystallization differentiation. The quartz zoning features are consistent with the hypothesis of crystal settling in evolving magma that erupted late from northern vents.

Supramolecular recognition: On the kinetic lability of thermodynamically stable host–guest association complexes

A molecular receptor consisting of a spacer bearing two cofacially disposed terpyridyl–palladium–ligand (terpy-Pd-L) units rigidly separated by about 7 Å has been investigated for molecular recognition of planar aromatic molecules. It is found that although the receptor forms stable 1:2 host–guest association complexes with 9-methylanthracene (9-MA), the guest undergoes very rapid site exchange within the receptor and with external free 9-MA. A crystal structure of the 2:1 adduct shows one 9-MA in the molecular cleft defined by the two terpy-Pd-L units and the other resides on an outside face of one terpy-Pd-L unit. To establish the site residency time of the guests, a number of tethered molecules were prepared. These involve an anthracene molecule tethered to a pyridine ligand bound to the palladium atoms to form intramolecular host–guest adducts. Rotating-frame Overhauser effects were used to infer the site residency of the anthracene guests in the receptor. Variable-temperature 1H NMR spectroscopy of the intramolecular host–guest complexes has revealed that the site residency time of the anthracene guests is 1.6 × 10−5 sec at 20°C and 1.3 sec at −90°C in acetone solution. Whereas the guests are thermodynamically stable, they are kinetically very labile. A crystal structure of one of the tethered host–guest adducts reveals the expected structure which is the same as that determined in solution by 1H rotating-frame Overhauser enhancement spectroscopy experiments.

Fertile and barren AlCr-spinel harzburgites from the upper mantle: Ion and electron probe analyses of trace elements in olivine and orthopyroxene: Relation to lherzolites

Ion and electron microprobe analyses of twenty-one CrAl-spinel harzburgite xenoliths from southern African kimberlites show two chemical groups. Orthopyroxenes from “fertile” harzburgites have higher CaO (mean of 11, 0.95 wt.%), Al2O3 (3.05 wt.%), Cr2O3 (0.85 wt.%) and Li (0.8 ppmw) than those from “barren” harzburgites (mean of 10, CaO 0.24 wt.%, Al2O3 1.10 wt.%, Cr2O3 0.35 wt.%, Li 0.3 ppmw). Olivines from all harzburgites have similar chemistry except that mean values of Li and Na are higher for barren than fertile harzburgites (Li 0.9 vs. 0.4 ppmw; Na2O 16 vs. 7 ppmw). Orthopyroxenes from fertile harzburgites are chemically distinct from those in garne lherzolites from southern Africa and spinel lherzolites from southwest U.S.A., but orthopyroxenes from barren harzburgites are indistinguishable from those in many coarse garnet lherzolites. Chromium, Ca, Ni, Na and Li in coexisting olivines and orthopyroxenes from the above rock types show complex patterns, which for Ca, Cr and Ni can be related to pressure and temperature. Temperatures from an empirically calibrated thermometer based on Ni-Mg exchange between olivine and orthopyroxene, measured modes of harzburgites (fertile, mean of 10: ol 68, opx 31, spinel-silicate intergrowth <0.5; barren, mean of 8: ol 76, opx 23, spinel and spinel-silicate intergrowth 1), and high-pressure experimental studies suggest (a) that harzburgites are residues of partial melting, (b) that barren harzburgites were melted to a greater extent at a higher temperature (though probably at a similar depth) than fertile harzburgites, and (c) that incomplete reequilibration during retrograde metamorphism has led to development of complex inter- and intragranular textures, probably in the range ∼700–900°C.

Oxygen isotopic composition of individual olivine grains from the Allende meteorite

Abstract The oxygen isotopic compositions of individual olivine grains from the Allende meteorite were determined by ion microprobe techniques. A variety of olivine grains were analysed: refractory forsterite grains ( 26 wt%) rims, and twenty-eight individual matrix olivine grains (21–41 wt% FeO). In an oxygen three-isotope plot refractory forsterite grains (δ17O ≈ −11%.; δ 18 O ≈ −8‰ ) fall on the Allende mixing line but are significantly less enriched in 16O than spinel and pyroxene from Ca,Al-rich inclusions (CAIs), possibly indicating a later formation of forsteritic olivine. Cores of isolated olivine grains with somewhat higher FeO contents (IOGs) have oxygen isotopic compositions similar to those of the refractory forsterites( δ 17 O ≈ −12‰ and δ 18 O ≈ − 9‰ ). Both types of olivine grains have oxygen isotopic compositions significantly different from those of chondrules. This clearly demonstrates that these olivine grains are not the result of crystallization of chondrule melts. Fayalite-rich rims of the IOGs are less enriched in 16O ( δ 17 O ≈ −3‰ ; δ 18 O ≈ 0‰ ) than the forsteritic cores. Arguments are presented that this supports a condensation origin of the rims from a gas phase less enriched in 16O than the gas phase from which the forsteritic cores had formed. Matrix olivines have oxygen isotopic compositions similar to fayalite-rich rims. However, there are variations in the oxygen isotopic composition of matrix olivines that exceed analytical uncertainties, suggesting a more complex origin.

Minor and trace element chemistry of carbonates, apatites and magnetites in some African carbonatites

Abstract In calcites and dolomites in seven African carbonatites, SrO, FeO and MnO occur in concentrations from I to 2 wt.%, whereas Ce, Y, Cu and Zn occur only at the ppm level. Sr, Ce and Y partition preferentially into calcite relative to co-existing dolomite, whereas Fe and Mn favour dolomite. Sr partitions preferentially into calcite relative to co-exisiting apatite, but the light rare-earth elements partition into apatite. Magnetite from Kerimasi contains up to 13 wt.% MgO and 6 wt.% MnO, extending the known ranges in composition of magnetites from carbonatites.