Isotopic and trace element analysis of zircons can provide reliable and robust estimates of age, compositions of coexisting minerals and melts, and constraints on the genesis and protoliths of host rocks. Recent technological developments facilitate analysis of oxygen isotope ratios in zircon with high accuracy and precision by laser heating/gas-source mass-spectrometry and in situ from thin sections or grain mounts by ion microprobe/secondary ion mass-spectrometer. A large number of studies have shown that non-metamict zircons preserve their δ18O value from the time of crystallization; hence oxygen isotope ratio can be correlated with age (U-Pb) or trace element composition. The zircon δ18O record is generally preserved despite other minerals that have been reset by high-grade metamorphism or intense hydrothermal alteration. Thus the refractory nature and robust inheritance of zircon offers a potential means to sort out magmatic equilibration and reequilibration, and post-magmatic alteration, an eternal problem for igneous rocks. New processes and interpretations for igneous events have been proposed when the effects of post-magmatic exchange are fully recognized. Crustal recycling can be recognized from magmatic values of δ18O(zircon), and if source rocks are igneous and young at the time of melting, δ18O will often be the best geochemical signature.

Microanalytical techniques are increasingly useful for stable isotope analysis of silicates. Both the laser fluorination/mass-spectrometer and the ion microprobe/secondary ion mass-spectrometer offer significant advantages over conventional techniques for analysis of zircon.

### Laser fluorination

Accurate analysis of δ18O in refractory minerals such as zircon is optimized by use of a CO2 laser (λ = 10.6 μm). The best precision has been obtained when zircons are powdered before analysis. Accuracy and precision of ±0.05 to ±0.1‰ (1 standard deviation = 1sd) are reported for homogeneous samples of ~2 mg (~0.5 mm3) (Valley et al. 1994, …

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Oxygen Isotopes in Zircon

Trace and minor elements in sphalerite: A LA-ICPMS study

Soil contamination with cadmium, consequences and remediation using organic amendments

hydrocarbons, carbon dioxide and nitrogen have been determined in Chromites forming giant orebodies in the southern part of the Early inclusion-rich samples. (3) In the northern and western part of the Palaeozoic ophiolite sequence of the Kempirsai Massif (Kazakhstan, Kempirsai massif, complex silicate–oxide assemblages formed in Urals) contain a large number of inclusions, i.e. silicates, sulphides, small orebodies of orbicular Al-rich chrome spinel. Chlorite, amalloys, arsenides, and fluids. The chromite orebodies are surrounded phibole, hydrogarnet, sphene, manganoan ilmenite and Ca–Ti oxide by dunite envelopes of variable thickness, which show transitional are documented in addition to Ni sulphides and rare PGM. The boundaries to harzburgite host rocks. The composition of ore-forming formation of chromitite in the Kempirsai Massif is explained in chromites in depleted mantle rocks of the southern part of the massif terms of a multi-stage process involving mantle fluids. Low-Cr, (Main Ore Field) is rather uniform, showing high cr-number high-Al spinel present in small orebodies in the northern and western [100Cr/(Cr+Al), 78–84] and mg-number [100Mg/ part of the massif formed from mid-ocean ridge basalt (MORB)(Mg+Fe), 51–85] values. Smaller bodies of Al-rich spinel in type melts extracted from fertile mantle in an extensional tectonic the northern and western part of the massif (Batamshinsk) have setting. The large orebodies and the amphibole–chromite veins in variable cr-number (38–60) and mg-number (50–88) values. the southern part formed later from interaction of hydrous, secondThree textural types of inclusions in chromite are distinguished: (1) stage high-Mg melts and fluids with depleted mantle in a convergent In Main Ore Field chromites, primary silicate inclusions generally tectonic setting. Metasomatic alteration of the mantle wedge above have high mg-number (>95), Cr and Ni, and are dominated by subducted crust by fluids played an important role in generating pargasitic amphibole, forsterite, diopside, enstatite and Na-phlosecond-stage melts and in releasing metals. gopite. Chromite formed over a temperature range from ~1200° to <1000°C at oxygen fugacities 1–2 log units above the fayalite– magnetite–quartz (FMQ) buffer. A diversity of primary and secondary platinum-group minerals (PGM) is described from the chromitites, including alloys, sulphides, sulpharsenides and arsenides

Petrogenesis of the Ophiolitic Giant Chromite Deposits of Kempirsai, Kazakhstan: a Study of Solid and Fluid Inclusions in Chromite

Approximately 275 mineral species have been identified in meteorites, reflecting diverse redox environments, and, in some cases, unusual nebular formation conditions. Anhydrous ordinary, carbonaceous and R chondrites contain major olivine, pyroxene and plagioclase; major opaque phases include metallic Fe-Ni, troilite and chromite. Primitive achondrites are mineralogically similar. The highly reduced enstatite chondrites and achondrites contain major enstatite, plagioclase, free silica and kamacite as well as nitrides, a silicide and Ca-, Mg-, Mn-, Na-, Cr-, K- and Ti-rich sulfides. Aqueously altered carbonaceous chondrites contain major amounts of hydrous phyllosilicates, complex organic compounds, magnetite, various sulfates and sulfides, and carbonates. In addition to kamacite and taenite, iron meteorites contain carbides, elemental C, nitrides, phosphates, phosphides, chromite and sulfides. Silicate inclusions in IAB/IIICD and lIE iron meteorites consist of mafic silicates, plagioclase and various sulfides, oxides and phosphates. Eucrites, howardites and diogenites have basaltic to orthopyroxenitic compositions and consist of major pyroxene and calcic plagioclase and several accessory oxides. Ureilttes .are made up mainly of calcic, chromian olivine and low-Ca clinopyroxene embedded in a carbonaceous matrix; accessory phases include the C polymorphs graphite, diamond, lonsdaleite and chaoite as well as metallic Fe-Ni, troilite and halides. Angrites are achondrites rich in fassaitic pyroxene (i.e. , AI-Ti diopside); minor olivine with included magnesian kirschsteinite is also present. Martian meteorites comprise basalts, Iherzolites, a dunite and an orthopyroxenite. Major phases include various pyroxenes and olivine; minor to accessory phases include various sulfides, magnetite, chromite and Ca-phosphates. Lunar meteorites comprise mare basalts with major augite and calcic plagioclase and anorthositic breccias with major calcic plagioclase. Several meteoritic phases were formed by shock metamorphism. Martensite (a2-fe,Ni) has a distorted body-centered-cubic structure and formed by a shear transformation from taenite during shock reheating and rapid cooling. The C polymorphs diamond, lonsdaleite and chaoite formed by shock from graphite. Suessite formed in the North Haig ureilite by reduction of Fe and Si (possibly from olivine) via reaction with carbonaceous matrix material. Ringwoodite, the spinel form of (Mg,Fe)2Si04, and majorite, a polymorph of (Mg,Fe)Si03 with the garnet structure, formed inside shock veins in highly shocked ordinary chondrites. Secondary minerals in meteorite finds that formed during terrestrial weathering include oxides and hy-. droxides formed directly from metallic Fe-Ni by oxidation, phosphates formed by the alteration of schreibersite, and sulfates formed by alteration of troilite.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.1997.tb01262.x

Mineralogy of meteorite groups

Cadmium and associated metals in soils and sediments of wetlands across the Northern Plains, USA.

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Virtual Worlds in Large Enrollment Science Classes Significantly Improve Authentic Learning

http://www.cs.ndsu.nodak.edu/~slator/docs/papers/jnca-proofs.pdf

Virtual environments for education

The Tres Marias carbonate-hosted Zn–Ge deposit in Chihuahua, Mexico contains sphalerite with the highest average Ge (960 ppm) and willemite with the highest reported Ge contents of Mississippi-Valley-type (MVT) deposits worldwide. This has prompted current exploration efforts to focus on the deposit as a high-grade source of germanium. The sulfide-rich ore type (>125,000 t at 20% Zn and 250 g/t Ge) contains Fe-rich botryoidal sphalerite (type I) associated with solid hydrocarbons. This type exhibits distinctive intimately intergrown lamellar texture of high-Fe sphalerite (average 9.9 wt.% Fe and 800 ppm Ge) and a somewhat less Fe-rich sphalerite phase (average 5.5 wt.% Fe and 470 ppm Ge). Reddish-brown banded sphalerite (type II, average 5.7 wt.% Fe and 1,320 ppm Ge) is subordinately followed by galena and pyrite. The sulfide-poor “oxidized” zinc ore (up to 50 wt.% Zn; 250 to 300 ppm Ge) is a fine-grained, often friable, alteration product of the sulfide ore and associated limestone and breccia host. While some areas are dominated by carbonates and sulfates, others are enriched in silicates such as hemimorphite and willemite. The gangue assemblage includes goethite, hematite, and amorphous silica or quartz. Minor wulfenite, greenockite, cinnabar, and descloizite also occur. Willemite occurs as interstitial replacement of sphalerite and fracture fillings in the oxidized ore and can be unusually rich in Pb (up to 2.0 wt.%) and Ge (up to 4,000 ppm). Oscillatory zonation reflects trace element incorporation into willemite from the oxidation of primary Ge-bearing sphalerite and galena by siliceous aqueous fluids. The Tres Marias deposit has hybrid characteristics consisting of a primary low-temperature MVT Ge-rich Zn–Pb sulfide ore body, overprinted by Ge-rich hemimorphite, willemite, and Fe oxide mineralization.

Bernhardt Saini-Eidukat

Papers

Trace and minor elements in sphalerite: A LA-ICPMS study

Cadmium and associated metals in soils and sediments of wetlands across the Northern Plains, USA.

Virtual Worlds in Large Enrollment Science Classes Significantly Improve Authentic Learning

Virtual environments for education

Zinc–germanium ores of the Tres Marias Mine, Chihuahua, Mexico