High Fe2O3 Content Research Articles

Origin of Baotoudong syenites in North China Craton: Petrological, mineralogical and geochemical evidence

Baotoudong syenite pluton is located to the east of Baotou City, Inner Mongolia, the westernmost part of the Triassic alkaline magmatic belt along the northern margin of the North China Craton (NCC). Zircon U-Pb age, petrological, mineralogical and geochemical data of the pluton were obtained in this paper, to constrain its origin and mantle source characteristics. The pluton is composed of nepheline-clinopyroxene syenite and alkali-feldspar syenite, with zircon U-Pb age of 214.7±1.1 Ma. Diopside (cores)-aegirine-augite (rims), biotite, orthoclase and nepheline are the major minerals. The Baotoudong syenites have high contents of rare earth elements (REE), and are characterized by enrichment in light rare earth elements (LREE) and large ion lithophile elements (LILE; e.g., Rb, Ba, Sr), depletion in heavy rare earth elements (HREE) and high field strength elements (HFSE). They show enriched Sr-Nd isotopic compositions with initial 87Sr/86Sr ranging from 0.7061 to 0.7067 and e Nd( t ) values from –9.0 to –11.2. Mineralogy, petrology and geochemical studies show that the parental magma of the syenites is SiO2-undersaturated potassic-ultrapotassic, and is characterized by high contents of CaO, Fe2O3, K2O, Na2O and fluid compositions (H2O), and by high temperature and high oxygen fugacity. The syenites were originated from a phlogopite-rich, enriched lithospheric mantle source in garnet-stable area (>80 km). The occurrence of the Baotoudong syenites, together with many other ultrapotassic, alkaline complexes of similar ages on the northern margin of the NCC in Late Triassic implies that the lithospheric mantle beneath the northern margin of the NCC was previously metasomatized by melts/fluids from the subducted, altered paleo-Mongolian oceanic crust, and the northern margin of the craton has entered into an extensively extensional regime as a destructive continental margin in Late Triassic.

Compositional variability of glauconites within the Upper Cretaceous Karai Shale Formation, Cauvery Basin, India: Implications for evaluation of stratigraphic condensation

A detailed mineral chemical investigation of glauconite within the condensed section deposits of the Cretaceous Karai Shale Formation, Cauvery Basin, India reflects a wide spectrum in chemical composition related to origin and evolution in different substrates, stratigraphic condensation, and post-depositional alteration. Fe- and Mg-rich glauconite, comprising up to 60% of the sedimentary rocks, occurs as replaced forms of fecal pellets, as infillings within pores and chambers of bioclasts including those of foraminifera, ostracoda, bryozoa, and algae, and as altered forms of mica exhibiting vermiforms. Authigenic precipitation of K- and Fe-poor glauconite, followed by addition of Fe and K into the lattice and concomitant release of Al and Si explains the origin of glauconite pellets and infillings; the origin of glauconite vermiforms in partly degraded mica involves only the second stage of Fe and K addition. Glauconite pellets and vermiforms exhibit sharply defined alteration zones along peripheries to form rims, and in proximity to cracks or cleavages with reduced K2O and Fe2O3 (total) and enhanced Al2O3 and SiO2, related to late-stage meteoric water actions. Cores of glauconite pellets and unaltered zones of vermiforms reflect ‘evolved’ characteristics with >6% K2O, typical of a condensed section, while other glauconite varieties occurring at the same stratigraphic level exhibit ‘slightly evolved’ nature, not consonant with stratigraphic condensation. Increasing abundance of glauconite pellets from the bottom to the top of the transgressive systems tract, accompanied by slight increase in K2O within their cores, reflects the effect of stratigraphic condensation on the evolution of glauconite. High Fe2O3 (total) content of glauconite in the Karai Shale Formation may be related to upwelling, although the Fe may be contributed partly by the biotite substrate. Mössbauer spectroscopy of glauconites reveals significant total Fe substitution in both tetrahedral and octahedral sites. Detailed mineral chemical analysis enables us to distinguish stratigraphically significant glauconite within the Karai Shale Formation from the rest of the glauconite notwithstanding its wide compositional range.

Trace element partitioning into sulfide: How lithophile elements become chalcophile and vice versa

Sulfides, although modally of low abundance in most igneous rocks, have strong influences on the geochemical behavior of many elements including Pb, Cu, Ni, and the PGEs. In a recent paper, we demonstrated a simple relationship between the sulfide-silicate partition coefficients D M sulf/sil of such elements and the FeO content of the coexisting silicate melt (Kiseeva and Wood 2013). ![Formula][1] where n is the valency of element M , [FeO] is the concentration of FeO in the silicate in wt%, and A is a constant that depends on temperature and pressure. Elements that closely obey the simple model are Pb, In, Sb, Cd, Co, Zn, and Cr. We show here, however, that the fitted slope n depends not only on the valency of element M , but also on how M interacts with oxygen, the dissolution of which as FeO in the sulfide increases as the FeO content of the silicate melt increases. To take account of interactions of trace element M with FeO dissolved in the sulfide we introduce an additional parameter ɛMSn/2FeOsulf (Wagner 1962), which represents the difference between the lithophile and chalcophile properties of M and those of Fe. If ɛMSn/2FeOsulf is positive, then element M is more chalcophile than Fe and if negative more lithophile. We performed experiments to investigate partitioning of lithophile Nb, Ta, Ce, and Ti between sulfide and simplified basaltic melt and find that they all exhibit, as expected, concave upward behavior on a plot of log D vs. log[FeO]. New experiments on Cu at low FeO contents confirm that it is more chalcophile than Fe, yielding a concave-downward curve of log D vs. log[FeO]. The combined results mean that nominally lithophile elements may partition more strongly into sulfide than nominally chalcophile elements at either very low or very high FeO contents of the silicate melt. For example, as the FeO content of the silicate melt declines below about 1 wt%, the partition coefficient of Cu, D Cusulf/sil declines to an unusually low value ( D Cusulf/sil ~80), whereas those for Nb ( D Nbsulf/sil ~600), and rare earths (REE’s) increase strongly. Under these conditions, Nb is, therefore, substantially more “chalcophile” than Cu in that it partitions much more strongly into sulfide. The implications of these observations for the Earth are that under a wide range of conditions one would expect significant partitioning of REE, Nb, Ta, Ti, and other lithophile elements into sulfides. Wohlers and Wood (2015) have, for example, shown that the partitioning of U and the REE into sulfides at low FeO content of the silicate is sufficiently pronounced that addition of a reduced sulfur-rich body to the accreting Earth could generate observable fractionation of Nd from Sm and, together with S, transfer sufficient U to the core to provide a significant energy source for the geodynamo. [1]: /embed/mml-math-1.gif

Magnesium isotope evidence for a recycled origin of cratonic eclogites

The Mg isotopic compositions of garnet and clinopyroxene mineral separates and whole rocks from 21 xenolithic eclogites (11 low-MgO eclogites and 10 high-MgO eclogites) from the Koidu kimberlite complex, erupted within the Archean Man Shield, Sierra Leone, West Africa, provide new evidence bearing on the origin of cratonic eclogites. Garnet and clinopyroxene in both low-MgO and high-MgO eclogites generally record equilibrium inter-mineral Mg isotope partitioning, with δ 26 Mg varying from –2.15‰ to –0.46‰ in garnets and from –0.49‰ to +0.35‰ in clinopyroxenes. Bulk δ 26 Mg values (–1.38‰ to +0.05‰), constructed from garnet and clinopyroxene data, are similar to results from rock powders (–1.60‰ to +0.17‰), suggesting that kimberlite infiltration has had negligible influence on the Mg isotopic compositions of the xenoliths. The δ 26 Mg values of low-MgO eclogites (–0.80‰ to +0.05‰) exceed the range of mantle peridotite xenoliths (–0.25‰ ± 0.04‰), consistent with the eclogite9s derivation from recycled altered oceanic crust. Similarly variable δ 26 Mg values in high-MgO eclogites (–0.95‰ to –0.13‰), together with their high MgO and low FeO contents, suggest that high-MgO eclogites were produced by Mg-Fe exchange between partially molten low-MgO eclogites and surrounding peridotites. Our study shows that cratonic xenolithic eclogites preserve a record of Mg isotopic compositions produced by low-pressure, surficial isotope fractionations. The recycling of oceanic crust therefore increases the Mg isotope heterogeneity of the mantle.

Distinctive compositional characteristics and evolutionary trend of Precambrian glaucony: Example from Bhalukona Formation, Chhattisgarh basin, India

Up to 20% of framework quartz and feldspar grains in wave-reworked sandstones in the Precambrian Bhalukona Formation, central India are replaced by glaucony, which is characterized by high K2O, Al2O3, MgO and low total Fe2O3 content. Textural evidence indicates that incipient glaucony within cleavages and fractures of detrital grains evolved to pellets. K2O content of glaucony remains high (av. >8%), despite its low total Fe2O3 content. Glaucony evolved with addition of total Fe2O3 at a constant K2O. During the course of maturation Al2O3 was released while total Fe2O3, MgO and SiO2 were added to the glaucony structure. Glaucony originated in a high aK+ and high aSi+ pore water environment by pseudomorphic replacement of grains. Continental weathering-related supply of Fe, Mg, K and Si facilitated glaucony formation in shallow marine sediments. The origin, evolution and geochemistry of shallow marine-originated Precambrian glaucony completely differ from those of their Phanerozoic counterpart.

Geotechnical and Geoacoustic Properties of Volcanic Soil in Ulleung Island, East Sea of Korea

The unique material properties of volcanic soils may cause stability problems within the soil. However, few studies have examined the composition and engineering characteristics of volcanic soils below sea level. The objective of this study is to investigate the engineering properties of volcanic soils sampled from Ulleung Island. For the volcanic soils, the index properties, particle geometry, and mineralogy are analyzed in the laboratory. An oedometer cell incorporated with bender elements is used to measure the small-strain stiffness and compressibility of the volcanic soils. To obtain the large strain strength parameter and hydraulic conductivity of the volcanic soils, direct shear tests, and constant head permeability tests are performed. The experimental results show that the basic index properties of volcanic soils sampled from Ulleung Island are very similar to the values of previously published reference data: poorly graded with a median grain size, very low fine fraction, and slightly high specific gravity. In addition, the particle surface texture features and elementary analysis indicates a dark grain color, small pits or holes in the grain, and relatively low SiO2 and high Fe2O3 contents. The friction angle of the volcanic soils depends on the relative density, and the hydraulic conductivity varies according to e3/(1 + e) and D102. The characterization of the electrical properties in Ulleung Island needs to be conducted with caution due to the high Fe2O3 content in the volcanic soils.

Geochemistry, zircon U–Pb ages and Sr–Nd–Hf isotopes of an Ordovician appinitic pluton in the East Kunlun orogen: New evidence for Proto-Tethyan subduction

Appinite is commonly derived from a mantle source in subduction zones and thus holds a key to constrain the tectonic evolution of ancient orogens. This study presents chronological, mineralogical and geochemical data for one appinitic pluton from the south Tethyan suture zone in the East Kunlun orogen, Northern Tibetan Plateau. The pluton is predominantly composed of hornblende-rich mafic appinites, with minor amounts of granodiorite. Zircon U–Pb age of the granodiorite (466Ma) is identical to the mafic appinites (447–450Ma). The mafic appinites are commonly hornblende diorites, which comprise large amounts of magnesio-hornblende [Mg/(Fe+Mg)=0.61–0.68] and andesine (An43–54). The hornblende diorites have low contents of SiO2 (48.62–54.95wt.%), high contents of total FeO (7.90–12.84wt.%) and MgO (4.32–11.89wt.%) and moderate values of Mg# [Mg#=molar 100∗Mg/(Mg+Fe); 49–69]. Their geochemistry displays: slight enrichment of light rare earth elements ((La/Yb)N=1.89–6.84) and flat heavy rare earth elements ((Ga/Yb)N=1.49–2.22); enrichment in large ion lithophile elements and depletion in high field strength elements; less-enriched isotopic compositions with initial 87Sr/86Sr ratios of 0.70536–0.70617, εNd(t) of 0.79–3.02 and zircon εHf(t) of 8.73–12.82. The associated granodiorites comprise plagioclase (45–50vol.%, An=26–39), quartz (15–20vol.%), K-feldspar (5–10vol.%), ferrohornblende [2–5vol.%, (Mg/(Fe+Mg)=0.45–0.49] and epidote (1–5vol.%). The epidotes have pistacite components ranging from 23 to 28. The granodiorites exhibit calc-alkaline character, and have rare earth and trace element patterns similar to the hornblende diorites. The geochemical compositions and simulations suggest that the parental magma of the mafic appinites was generated by partial melting of one depleted mantle source which was metasomatised by subducted sediment-derived felsic melts (ca. 20–25%). Fractional crystallization of clinopyroxene, hornblende, magnetite and titanite has driven the appinitic magma to cogenetic granodiorite. The Late Ordovician mafic appinites indicate that there did exist Proto-Tethyan subduction along the South Kunlun suture zone, and the subduction would add significant volumes of sediment-derived melts into the depleted mantle wedge, resulting into metasomatism and melting with the formation of appinitic magma.

Preparation and characteristics of lightweight sludge ceramics by dehydrated sludge from dye intermediate processing wastewater treatment

Lightweight sludge ceramics (LSC) manufactured by two kinds of clay and dehydrated sludge from 4,4′-diaminostilbene-2,2′-disulfonic acid (DSD acid) processing wastewater treatment (DSD sludge) were studied for the sludge treatment. The raw pellets were preheated at 400°C for 15.0 min and sintered at 1,150°C for 8.0 min, which was beneficial to produce LSC. The optimum DSD sludge addition rate was determined by the physical properties (bulk density, water absorption, grain density, and expansion ratio), and then toxic metal leaching properties and microstructure properties were characterized. The results indicated that clay with high content of Fe2O3 might be more suitable for ceramics preparation, lower bulk (627.00 kg m−3), and grain density (1,280.00 kg m−3), and higher expansion ratio (18.80 v/v%) could be obtained with the optimum DSD sludge addition rate of approximately 50.0 wt%. Toxic metal leaching test showed that LSC was nontoxic and would not cause secondary pollution to water environment when applied as fillers, and the sintered ceramics had rough surface and porous interior according to microstructure analysis. Therefore, LSC prepared in this study might be utilized as biological media in wastewater treatment, which could turn hazardous solid waste (DSD sludge) into useful materials.

Mineraloška in geokemična karakterizacija rimske žlindre z arheološkega najdišča pri Mošnjah (Slovenija)

Roman slag from the archaeological site near Mosnje (NW Slovenia) was studied with respect to its mineralogical and geochemical characteristics. Samples were analysed with light microscopy, X-ray powder diffraction (XRD), scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS) and Raman microspectroscopy. A chemical investigation was carried out using inductively coupled plasma-atomic emission spectroscopy (ICP-ES) to determine the major elements. The investigated slags are recognized as iron slags, grouped into two main classes according to their chemical and mineralogical compositions. The first group is characterized by high Fe2O3 and low SiO2 contents and the second by high CaO and SiO2 and low Fe2O3 contents. The phase occurrence obviously depends on the chemical composition as the first group mainly consists of fayalite, wustite and magnetite, and the second one of augite, leucite, hedenbergite, monticellite and kirschsteinite.

Petrographic and chemical characterization of Bronze Age pottery from the settlement of Mount San Paolillo (Catania, Italy)

The excavations at Mount San Paolillo (Catania, Italy) led to the discovery of a Prehistoric site that still represents the most important evidence of Middle and Late Bronze Age settlement in this area. During the excavations, archeologists located a hut, a store for ceramic storage vessels, and a pottery workshop, all of which provided a large quantity of heterogeneous ceramics with apparent typological parallels in other areas of Sicily, such as Syracuse, Augusta, and Messina. A large number of specimens were selected in order to cover all the macroscopic types and the main classes. The results identified four petrographic fabrics. Most of the ceramics are characterized by abundant tempers consisting of volcanic rock fragments and occasionally of grog. Only a few samples contained common fine-grained quartz. The groundmass ranges from non-micaceous to very micaceous. In some cases, there is evidence of mixed clays. Analysis of the chemical composition of the ceramics revealed the existence of two groups with low and high CaO contents. The high Fe2O3 content (more than 8.7 wt%) is probably due to the use of temper from altered pyroclastic rocks which are of local provenance as SEM-EDX data suggest, even if petrographic and chemical results suggest that different raw materials may have been used. The data provided by these archeometric analyses have made a significant contribution to the study of Middle and Late Bronze Age pottery from the Catania area, by offering insights into the methods, production processes, and high technical level of the prehistoric craftsmen.

Nature and Origin of the Amphibolites in the Precambrian Basement Complex of Iseyin and Ilesha Schist Belts, Southwestern Nigeria

Petrographic and geochemical studies of amphibolites from Wonu-Apomu area in Iseyin-Oyan schist belt and Ife-Ilesa area in Ilesha schist belt, southwestern Nigeria, were carried out with a view to unravel their nature and petrogenesis. The amphibolites in Wonu-Apomu are associated with quartzite, quartz schist, talc-schist, granite and pegmatites, while those of Ife-Ilesha area are associated with anthophyllite schist, talc tremolite and talc chlorite schists. Chemical data of the amphibolites showed high Al2O3 (>14%), Fe2O3 (>12.40%), CaO (>8.10), Na2O (>3.10%) and K2O (>5.0%) contents. Trace element data showed that the amphibolites are enriched in Ba (>137ppm), Sr (>122ppm), Rb (>33ppm), Zr (55pm) and Y (>37ppm), but impoverished in Cr (<62ppm), Ni (<57ppm) and Zn (<83ppm). Petrogenetic indices and discriminant plots of Na2O + K2O vs SiO2, Ga vs Y, Zr/Y vs Zr, Cr vs Ni, Fe2O3 –Na2O + K2O – MgO, indicated tholeiitic basalt affinity of the amphibolites and emplacements of the precursor basaltic rocks within continental crust.

Depositional environment of cherts of the Sikhote-Alin region (Russia far east): Evidence from major, trace and rare earth elements geochemistry

The first data of geochemical study of the Benevka Section cherty rocks belonging to the Taukha terrane of the Sikhote-Alin Late Jurassic-Early Cretaceous accretionary prism, Russia Far East are presented. These data demonstrate essential distinctions of major, trace and rare earth element concentrations in different parts of the measured stratigraphic section. The lower chert horizons exhibit high Fe2O3 and MnO contents, low concentrations of Al2O3 and TiO2, relatively high V/Y ratio, and extremely low value of negative Ce anomaly. In contrast the upper horizons composed of clayey cherts and siliceous mudstones are characterized by high Al2O3, TiO2 and K2O contents, low Fe2O3 and MnO values, low V/Y ratio, and slightly negative Ce anomaly. In the middle part of the Benevka Section, in which cherts gradually changed to clayey cherts, intermediate geochemical characteristics are present. Based on these data obtained the depositional environments correspond to proximal to the spreding ridge, open-ocean and near continental margin regimes were successfully reconstructed from bottom to top of the Benevka Section, that indicate that significant horizontal movement took place of the sea-floor, on which the cherts were deposited.

The effect of chemical modification on the physico-chemical characteristics of halloysite: FTIR, XRF, and XRD studies

The effect of chemical modification of halloysite from a Polish strip mine “Dunino” on the chemical composition and structure of this clay mineral was studied using infrared spectroscopy (ATR FT-IR), wavelength dispersive X-ray fluorescence (WDXRF), and X-ray powder diffraction (XRPD) methods. The results obtained by the WDXRF technique confirm that the content of silica and alumina was the highest for bleached halloysite samples and the lowest for acid-treated halloysite. A higher content of Fe2O3 in comparison to halloysite samples coming from other countries was observed for raw halloysite samples. XRPD diffraction pattern obtained for raw halloysite confirmed the presence of halloysite, kaolinite, hematite, and calcite minerals in the sample. Bleaching the halloysite removes (or significantly reduces) the content of other minerals present in the raw halloysite. The FT-IR spectra of the studied halloysite samples show in the 3700–3600cm−1 region well-defined hydroxyl stretching bands characteristic for the kaolin-group minerals and bands associated with the vibrations of the aluminium–silicon skeleton in the 1400–1000cm−1 region. Modifying halloysite with 4-chloro-aniline causes successive incorporation of amine into the BH sample.

Bentonite protects neural crest stem cells from death caused by aflatoxin B1

Bentonites, which have been shown to be good mycotoxin adsorbents, have a wide range of biochemical and industrial uses. Although many in vitro studies have shown the effects of bentonite on a variety of cell types, there is no comparable information regarding its effects on neural crest (NC) stem cells. The NC is a collection of multipotent and oligopotent progenitors endowed with both neural and mesenchymal potentials. NC cells originated at trunk level can become peripheral nervous system cells, melanocytes and smooth muscle cells. For this reason, the NC is considered an ideal model for studying the role of different substances on cell differentiation, survival and growth. We have recently shown that aflatoxin B1 (AFB1) decreases the viability and reduces the population of NC cells. In the present work, we have characterized bentonite extracted from the South of Brazil and investigated its effects on NC differentiation and survival, when challenged with AFB1. The results have highlighted the high content of SiO2, Fe2O3 and K2O present in bentonite, with content of MnO, MgO, CaO, Na2O, TiO2 and P2O5 lower than 1%. These results have also shown that bentonite at 0.6mg/mL is not toxic to NC cells in culture. Furthermore, bentonite increased the viability of NC cells previously treated with AFB1 without affecting cell differentiation. The evidence suggests that AFB1 interacted with bentonite by occupying the interlayer spaces, which might have contributed to a reduction of AFB1 availability and, consequently, a reduction in NC damage and an increase in the total number of cells. Our study contributes to a better understanding of the effects of clay minerals on the NC and may help to create new, more effective pharmacological applications to reduce or eliminate the toxic effects of AFB1.

MINERALOGICAL, GEOCHEMICAL AND ENVIRONMENTAL DEPOSITION OF CLAY IN ESNA SHALE AT EL-BURUK – EL-HASSANA AND EL-HIMMAH – BAGHDAD AREAS NORTH SINAI, EGYPT.

This paper deals with the study of the Mineralogical, Geochemical and Environmental deposition of Clays in Esna Shale at El-Buruk- El-Hassana and El- Himmah Baghdad areas, North Central Sinai, Egypt. The present work is based on the field and laboratory work carried out by present authors. sixty stratigraphic sections representing Esna shale unit in the study area were studied, measured and sampled. The laboratory work comprise 17 samples for XRD analysis to study the mineral constituents of the clay and argillaceous rocks and 36 samples for chemical analysis using XRF method to detect the major oxides SiO2, Al2O3, Fe2O3, CaO, MgO, TiO2, MnO, Na2O, K2O, SO3--, Cl-, P2O5 and L.O.I. and ten samples for the trace constituents, F, Ba, Cr, Cu, Li, Ni, Zn, As, B, Ga, Se, Y, V, Co, Rb, Sr, Nb, Mo, Sn, Sb, La, Yb, Hf, Ta, Pb, Zr and Ce. Montmorillonite and kaolinite are the main constituents of clays. The other associated minerals are quartz, gypsum, halite and dolomite. Geochemical speaking, SiO2, Al2O3, K2O and Na2O are controlled by the amount of montmorillonite, kaolinite and illite while CaO and MgO contents are controlled by calcite and dolomite which occur as minor constituents. The high and low contents of Fe2O3 and MnO respectively are attributed to the low oxidation potential that prevailed during the deposition of clay causing precipitation of Fe+2 keeping Mn+2 in soluble state. Esna Shale of the study areas are deposited in deposition environments changes from very shallow inner neritic zone to outer neritic zone.

Characterization of genotoxic response to 15 multiwalled carbon nanotubes with variable physicochemical properties including surface functionalizations in the FE1-Muta(TM) mouse lung epithelial cell line.

Carbon nanotubes vary greatly in physicochemical properties. We compared cytotoxic and genotoxic response to 15 multiwalled carbon nanotubes (MWCNT) with varying physicochemical properties to identify drivers of toxic responses. The studied MWCNT included OECD Working Party on Manufactured Nanomaterials (WPMN) (NM-401, NM-402, and NM-403), materials (NRCWE-026 and MWCNT-XNRI-7), and three sets of surface-modified MWCNT grouped by physical characteristics (thin, thick, and short I-III, respectively). Each Groups I-III included pristine, hydroxylated and carboxylated MWCNT. Group III also included an amino-functionalized MWCNT. The level of surface functionalization of the MWCNT was low. The level and type of elemental impurities of the MWCNT varied by <2% of the weight, with exceptions. Based on dynamic light scattering data, the MWCNT were well-dispersed in stock dispersion of nanopure water with 2% serum, but agglomerated and sedimented during exposure. FE1-Muta(TM) Mouse lung epithelial cells were exposed for 24 hr. The levels of DNA strand breaks (SB) were evaluated using the comet assay, a screening assay suitable for genotoxicity testing of nanomaterials. Exposure to MWCNT (12.5-200 µg/ml) did not induce significant cytotoxicity (viability above 92%). Cell proliferation was reduced in highest doses of some MWCNT after 24 hr, and was associated with generation of reactive oxygen species and high surface area. Increased levels of DNA SB were only observed for Group II consisting of MWCNT with large diameters and high Fe2 O3 and Ni content. Significantly, increased levels of SB were only observed at 200 µg/ml of MWCNT-042. Overall, the MWCNT were not cytotoxic and weakly genotoxic after 24 hr exposure to doses up to 200 µg/ml.

Composition, origin and industrial suitability of the Aswan ball clays, Egypt

Although Aswan ball clays occur in relatively large reserves, information on their geochemistry and source is still lacking. This paper presents detailed petrographic, mineralogical, and geochemical investigations on these clays to examine their source as well as their possible use as raw materials for ceramic and refractory industries.Aswan ball clays occur as gray, yellowish gray, reddish to brownish gray, massive to faint laminated, and moderately hard clays. Grain-size distributions indicate the dominance of clay fractions (45–57wt.%). Low-ordered kaolinite is the main constituent (39–60wt.%) along with quartz (24–46wt.%) and low crystalline illite (10–19wt.%). Fine-grained anatase is reported as a minor constituent (~2wt.%). Aswan clays are typically ball clays (SiO2/Al2O3=2.3–4.1) with relatively high Fe2O3 and TiO2 contents. The trace elements occur in two assemblages. Elements associated with the Fe-bearing phases include Cu, Ni, Co, Zn, V, and Pb as indicated from the positive correlations with the Fe2O3 contents. Elements occur as silicate minerals but not in clay minerals such as Nb, Zr, Y, Hf, Ta, and U as revealed from the positive correlations of these elements with the SiO2 and the negative correlations with the Al2O3 contents. The sum of rare earth elements (REEs) ranges from 291 to 335ppm with negative correlations with the Al2O3 and positive correlations with the SiO2 suggesting the occurrence of REE as silicates but not in clay minerals. Chondrite-normalized REE patterns exhibit light rare earth element enrichment relative to heavy rare earth elements ((La/Yb)N=9.2–11.7) and slightly negative Eu anomalies (Eu/Eu*=0.74–0.83) without Ce anomalies (Ce/Ce*=0.96–1.03).Major, trace, and rare earth elements geochemistry of the clay fractions indicates a mixture of more than rock types as a source of the Aswan ball clays. The high Zr and Y contents and La/Yb ratios suggest a contribution of granitic rock, while the relatively high contents of TiO2 and Ti are suggestive for a contribution of mafic source rock. Plot of the study clays in the Rb-K2O and Hf–La/Th binary plots supports mixed felsic and mafic source rocks of the study clays. In addition, high Nb contents indicate a contribution of alkaline source rock. Plot of the study clays in the phyllite and schist field in the Co–Th binary diagram also indicates contribution of metamorphic source rock to the source of the clays.The abundance of clay size fractions (<2μm), low-order kaolinite and illite, absence of I/S minerals, low fluxing agents such as alkali oxides (Na2O and K2O) and alkaline earth oxides (CaO and MgO), low S and Cl contents, and low contents of toxic elements (As, Cd, Hg, and Pb) reveal the suitability of the Aswan ball clays as a good quality and environment-friendly raw material for ceramic and refractory industries.

Geochronology and geochemistry of Late Ordovician–Early Devonian gneissic granites in the Kumishi area, northern margin of the South Tianshan Belt: Constraints on subduction process of the South Tianshan Ocean

The South Tianshan Belt has recorded the evolution of the south branches of the Paleo-Asian Ocean and is pivotal for understanding the formation of the southernmost part of the Central Asian Orogenic Belt. In order to place constraints on the tectonic evolution of the South Tianshan Ocean, three highly deformed granitic plutons (monzonitic granites, biotite K-feldspar granites and two-mica granites) exposed in the Kumishi area were collected for geochronological and geochemical studies. Zircon LA-ICP-MS U–Pb dating of the gneissic granites from the three plutons yielded crystallization ages at 446.2±2.2Ma, 431.0±2.8Ma and 407.3±3.1Ma. All of these gneissic granites have geochemical characteristics of calc-alkaline igneous rocks. The biotite monzonitic granites (446Ma) are slightly peraluminous, LREE-enriched and show relatively flat HREE patterns mostly with negative Eu anomalies. The rocks have positive Pb and negative Nb, Ta, Ti anomalies. In combination with their negative εHf(t) values (−7.9 to −11.6) and the corresponding old TDMc ages (1.93–2.16Ga), we suggest that the monzonitic granites were mainly derived from partial melting of the middle-lower crust dominated by Precambrian basement rocks. The biotite K-feldspar granites (431Ma) are characterized by high K2O, low Fe2O3 and MgO contents. They show REE patterns similar to the monzonitic granites, as well as the Nb, Ta, Ti depletions, but have more enrichment in U, Pb, Zr, and Hf. Their depleted εHf(t) values (+0.7 to +5.4) and young TDMc ages (1.07–1.37Ga) imply significant input of mantle-derived juvenile materials, and thus suggest that the K-feldspar granites were possibly derived from a K-enriched crustal source mixed significantly with mantle-derived juvenile materials. The two-mica granites (407Ma) show a typical S-type granite affinity with high Al2O3/TiO2, low CaO/Na2O and K2O/Al2O3 ratios, suggesting a pelitic source. These characteristics, together with their positive εHf(t) values (−0.2 to +3.1) and relatively young TDMc ages (1.20–1.41Ga), indicate that the two-mica granites were most likely generated by partial melting of a pelitic source with less input of juvenile materials. All of the samples from the three plutons show same geochemical characteristics of felsic magmatic rocks formed in an arc-related tectonic setting. Together with the northward thrusting tectonics and the arc magmatic rocks exposed along the South Nalati–Kawablak Fault, a northward subduction of the South Tianshan Ocean is suggested to interpret the formation of the three granitic plutons. Taking into account the distinct tectonic polarity and distribution of magmatic rocks in the western and eastern South Tianshan Belt, we suggest that the South Tianshan Ocean probably underwent different subduction processes in its western and eastern parts. A single northward subduction and a divergent bidirectional subduction are further proposed to interpret the formation of the western and eastern South Tianshan Belt, respectively.

A mafic intrusion of “arc affinity” in a post-orogenic extensional setting: A case study from Ganluogou gabbro in the northern Yidun Arc Belt, eastern Tibetan Plateau

Generally, arc-related or subduction-related mafic magmas are formed during or slightly postdate subduction, and characterized by depletion in high field strength elements (HFSEs) relative to the large ion lithophile elements (LILEs) and light rare-earth elements (LREEs). Combining with mineral chemistry and Sr–Nd isotopes, these geochemical characteristics were usually used to define an arc setting, especially for some ancient arcs that had been strongly modified by later tectonic activities. However, we report an exceptional case from the northern part of the Triassic Yidun Arc Belt, eastern Tibetan Plateau. The Ganluogou gabbro (∼152Ma) occurs as several intrusive bodies. Its mineral assemblage is olivine (chrysolite), plagioclase (anorthite), clinopyroxene (diopside), amphibole (edenite and pargasite) and phlogopite. Whole rock geochemistry shows low SiO2 (42.87–46.99wt.%), total rear earth elements (ΣREE=22.8–28.4ppm), Na2O+K2O (0.92–1.34wt.%), and high Al2O3, MgO and FeO contents. It has small variations of initial 87Sr/86Sr ((87Sr/86Sr)i=0.7053–0.7055) and εNd(t) values (−4.8 to −1.8). All the samples exhibit enrichment in LILEs including Th and U, but strongly depleted in HFSEs, including Nb, Ta, Zr and Hf. For the mineral chemistry, there are two type amphiboles. Amp(I) show higher V, Sc, Cr, Sr, Nb and Zr contents, but lower Th and U contents than those of Amp(II). Their REE patterns range from convex shape without Eu anomaly to LREE-enriched pattern with weak positive Eu anomaly. We suggest that Amp(I) was crystallized from a liquid that was mainly buffered by olivine, clinopyroxene and plagioclase, while Amp(II) crystallized from later melt that was mainly buffered by olivine. Based on clinopyroxene chemistry, compositions of coexisting olivine and plagioclase, and whole rock Sr–Nd isotopes, the parental magma of the Ganluogou gabbro is interpreted as a tholeiitic arc-affinity magma, which might be derived from an N-MORB mantle that had been metasomatised by slab-derived melts in the late Triassic (237–206Ma). Thus, the Ganluogou gabbro provides an example that magmas exhibiting arc-affinity could in fact be formed in a post-orogenic extensional setting.

Compositional Variation in Magma through Early Neogene in the Northeast Indian Ocean: A Testimony from Glass Shards

Abstract: We report unusual occurrence of glass shards with diverse morphologies and compositions in the volcanic ash associated with the early Neogene marine stratigraphic succession (early Miocene to early middle Miocene) of Andaman-Nicobar Islands, Northeast Indian Ocean. These small, ash-size (200 to 800 µm) broken pieces of glass shards when viewed under Scanning Electron Microscope (SEM), represent distinctive - platy, sickle, bicuspate, concentric, angular, horn shape and slivers with broken angular bubble wall - morphologies. Glass shards are colourless. But, a few are grey or reddish-brown, indicate high Fe content. Chilled, juvenile, angular and blocky shards show fragments of highly viscous, silicic magma. Spindle and ribbon-shape shards form from a low viscosity basalt and rhyolite. Electron Probe Micro Analyzer (EPMA) was used to measure low concentration variations of major oxides within individual amorphous silicate solid glass shards whose disordered atomic structure is that of a liquid derived from a silicate melt. Major elemental chemistry of early Miocene glass shards from Colebrook island show low silica, alkalis, high FeO(T) MgO and CaO, whereas, early middle Miocene glass shards from Inglis island show high silica, alkalis, low FeO(T), MgO and CaO contents. These data-sets when plotted on ternary Total Alkali-Silica and Na2O+K2O-MgO-FeO (T) diagrams show that their data plots lie within the basaltic-andesite, tephri-phonolite, rhyolite and trachyte fields. These glass shards which were present in the provenance, formed by explosive eruption of lavas, ranging in composition from basalt to rhyolite with andesite/ basalt-andesite being the most common magma types erupted sub-areally, implying island arc type of tectono-magmatic setting for the formation of these lavas. However, more evolutionary variant rhyolite was most likely formed by crystal fractionation.