The solar abundance of tungsten

Recent measurements of Wi oscillator strengths (Obbarius and Kock, 1982) lead to a solar photospheric abundance of tungsten, log _W = 1.06 ± 0.15 on the scale log _H = 12. The solar W/Si abundance ratio, 0.32 W atoms/10⁶ Si, coincides with that found in carbonaceous chrondrites. Implications for solar-system r-processes abundances are pointed out.     

Calcmylonites and solution transfer in a Devonian reef at Warstein,Germany

Massive limestone complexes of Late Palaeozoic age are scattered across the allochthonous foreland of the Hercynides in Germany. One of these complexes is situated at Warstein. Stratigraphic facies studies have represented the Warstein complex as a reef in a coastal shelf. Our study emphasizes that at least part of the reef consists of a pile of calcmylonites.The calcmylonites have a strong foliation (S_m) and lineation (L_m) and a structural asymmetry indicating non-coaxial deformation. X-ray textures and calcite microstructures show that the mylonitization involved intracrystalline deformation and dynamic recrystallization. These processes competed with solution transfer, as the mylonites are corroded at S_m-parallel stylolites and contain carbonate veins. Cathodoluminescopy shows that some veins are parallel to S_m and have been recrystallized, whereas others are normal to S_m and retain a fibrous crackseal microstructure. The latter type created limestones showing a pair of preferred grain boundary orientations; one normal to S_m, one in S_m. This orthogonal boundary fabric is distinct from crystalplastic fabrics: the latter show only one preferred grain boundary orientation (in S_m).

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Zusammenfassung Massenkalkkomplexe spätpaläozoischen Alters liegen verstreut über das allochthone Vorland des Variszischen Gebirges in Deutschland. Einer dieser Komplexe liegt bei Warstein. Stratigraphische Faziesstudien haben den Warsteiner Komplex als ein Riff in einem küstennahen Schelf dargestellt. Die vorliegende Arbeit betont, daß wenigstens ein Teil des Riffes aus einer Stapelung von Kalkmyloniten besteht.Die Kalkmylonite haben eine starke Foliation (S_m) und Lineation (L_m), und eine strukturelle Asymmetrie die auf nicht-koaxiale Verformung hinweist. Röntgentexturen und Calcitmikrostrukturen zeigen, daß die Mylonitisierung intrakristalline Verformung und dynamische Rekristallisation beinhaltet. Diese Prozesse müssen mit Lösungstransport konkurriert haben, da die Mylonite an S_m-parallelen Styloliten korrodiert sind und Karbonatgänge erhalten. Kathodolumineskopie zeigt, daß einige Gänge (parallel zu S_m) rekristallisiert sind, während andere (senkrecht zu S_m) eine faserige crack-seal Mikro-Struktur enthalten. Der letzte Typ ist verbunden mit Konformgefügen. Diese unterscheiden sich von kristallplastischen Kornformgefügen, da sie eine zweite bevorzugte Korngrenzorientierung aufweisen, die senkrecht zur ersten (in S_m) einfällt.

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Résumé Les complexes de calcaires massifs de l'Âge paléozoîque supérieure sont repandus sur l'avantpays allochthone des Hercynides en Allemagne. Un de ces complexes est situé à Warstein. Les Études de faciès stratigraphiques ont répresenté le complexe à Warstein comme un Récif littoral. Notre étude montre que au moins partie de ce «Récif» consiste en un empilement des calcmylonites.Les calcmylonites ont une foliation (S_m) et linéation (L_m) fort, et une asymmetrie structurale indiquant de la déformation non-coaxiale. Les textures röntgenographiques et les microstructures calcitiques montrent que la mylonitization était incluse de déformation intracristalline et récristallisation dynamique. Ces processus auront été en compétition avec dissolution-cristallization («solution transfer»), car les mylonites sont corrodées aux stylolites parallel à S_m et contient des veines carbonatiques. La cathodoluminescopie montre que quelques veines (parallel à S_m) sont récristallisées, pendant que les autres (perpendiculaire à S_m) ont retenu une microstructure fibreuse («crack-seal»). Le dernier type est lié avec des fabriques de forme des grains. Ils se sont distingués des fabriques de plasticité cristalline par la présence d'une deuxième orientation préférentielle des bordures des grains, perpendiculaire à la première (dans S_m).

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. Warstein'a. , . , , , »« . (S_m) (L_m), , . , - , . , .. , S_m, . , , S_m, , , S_m, = »crack-seal«. : , S_m.

     

On the climate response to zero ozone

Although ozone appears in the Earth’s atmosphere in a small abundance, it plays a key role in the energy balance of the planet through its involvement in radiative processes. Its absorption of solar radiation leads to the temperature increase with height defining the tropopause and the stratosphere. Moreover, excluding water vapor, O₃ is the third most important contributor (after CO₂ and CH₄) to the greenhouse radiative forcing. Thus, the total removal of O₃ content in an Earth-like atmosphere may cause interesting response of the climate system that deserves further investigation. The present paper addresses this issue by means of a global climate model where the atmosphere is coupled with a passive ocean of a given depth. The model, after reaching the statistical equilibrium under present climate conditions, is perturbed by a sudden switch off of the O₃ content. Results obtained for the new equilibrium suggest that the model gets in a colder state mainly because of the water vapor content decrease. Most of the cooling occurs in the Southern Hemisphere while in the Northern Hemisphere the ice cap melts quite consistently. This process appears to be governed by the northward cross-equatorial heat transports induced by changes in the general circulation.     

The transition from porphyry- to epithermal-style gold mineralization at Ladolam, Lihir Island, Papua New Guinea: a reconnaissance study

The exceptionally large gold resource at Ladolam (>1,300 metric tons of gold), Lihir Island, resulted from the transition of an early-stage, low-grade porphyry gold system to a low-sulfidation epithermal gold event. This transition was probably triggered by rapid decompression during the partial slope failure of Luise stratovolcano and accompanied by the ingress of seawater. The original porphyry stage is indicated by remnant hydrothermal breccia clasts of strongly biotite-magnetite altered monzodiorite with disseminated pyrite - chalcopyrite and poorly developed pyrite - quartz stockwork veins. The breccias are overprinted by biotite-magnetite alteration and their matrix is strongly mineralized with disseminated auriferous pyrite. The breccias are cut by late-stage epithermal quartz-chalcedony-illite-adularia-pyrite veins and associated illite-adularia alteration that locally contain bonanza gold grades of up to 120 g/t. Isotope data suggest a magmatic source of sulfur in the gold-bearing fluids at Ladolam. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00126-001-0230-y     

A stochastic inversion workflow for monitoring the distribution of CO<Subscript>2</Subscript> injected into deep saline aquifers

We present a two-step stochastic inversion approach for monitoring the distribution of CO₂ injected into deep saline aquifers for the typical scenario of one single injection well and a database comprising a common suite of well logs as well as time-lapse vertical seismic profiling (VSP) data. In the first step, we compute several sets of stochastic models of the elastic properties using conventional sequential Gaussian co-simulations (SGCS) representing the considered reservoir before CO₂ injection. All realizations within a set of models are then iteratively combined using a modified gradual deformation algorithm aiming at reducing the mismatch between the observed and simulated VSP data. In the second step, these optimal static models then serve as input for a history matching approach using the same modified gradual deformation algorithm for minimizing the mismatch between the observed and simulated VSP data following the injection of CO₂. At each gradual deformation step, the injection and migration of CO₂ is simulated and the corresponding seismic traces are computed and compared with the observed ones. The proposed stochastic inversion approach has been tested for a realistic, and arguably particularly challenging, synthetic case study mimicking the geological environment of a potential CO₂ injection site in the Cambrian-Ordivician sedimentary sequence of the St. Lawrence platform in Southern Québec. The results demonstrate that the proposed two-step reservoir characterization approach is capable of adequately resolving and monitoring the distribution of the injected CO₂. This finds its expression in optimized models of P- and S-wave velocities, density, and porosity, which, compared to conventional stochastic reservoir models, exhibit a significantly improved structural similarity with regard to the corresponding reference models. The proposed approach is therefore expected to allow for an optimal injection forecast by using a quantitative assimilation of all available data from the appraisal stage of a CO₂ injection site.     

CGSG系列标准物质元素分馏效应及主量微量元素单元内均匀性探究

探究CGSG系列标准物质(CGSG-1、CGSG-2、CGSG-4、CGSG-5)的元素分馏效应及均匀性问题有助于开展其质量评估和应用推广。本文采用电子探针(EMPA)和激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)研究了CGSG标准物质中的元素分馏效应、主量和微量元素单元内均匀性,并报道了主量和微量元素分析数据。结果表明,在50μm激光束斑下,CGSG系列标准物质的元素分馏效应可忽略不计。EMPA均匀性指数结果显示,CGSG标准物质主量元素的单元内均匀性满足要求;以MPI-DING标准物质为参照,LA-ICP-MS测试CGSG标准物质中的大多数微量元素的单元内均匀性良好。与已报道的数据相比,本文报道的EMPA主量元素数据偏差在2%以内;LA-ICP-MS主量元素数据偏差在5%以内,微量元素数据基本匹配,少数元素由于分析不确定度较大等原因,如Cr、Ge、Cd、As、Tl等与已报道数据偏差较大。总体上,本文报道的分析数据可为CGSG定值数据库提供进一步的补充。     

Pyroxenes in Serra de Magé: cooling history in comparison with Moama and Moore County

Single-crystal X-ray, optical, and microprobe study of pyroxenes in the Serra de Magéfeldspar cumulate eucrite indicate complex exsolution features from a slow cooling history. Two pyroxenes now exist: “low” orthohypersthene ( P2₁ca) as host ( ～82 vol.%) and augite ( C2/c) in four distinct habits. This pyroxene pair yields an apparent “equilibration” temperature of ～900°. These relations are typical for orthopyroxene of both the Stillwater and Kintoki-San types, indicating an original pigeonite pyroxene with a bulk composition En₅₁Fs₃₉Wo₁₀. Variations in augite-hypersthene textural relationships suggest variable initial compositions from about Wo₈ to Wo₁₁. The bulk composition is intermediate to those of initial pigeonites in Moama and Moore County but the augite-hypersthene tie line is longer suggesting a slower cooling history. Our examinations of all three meteorites show that Serra de Magéaugite lamellae are as thick or thicker than those in the other meteorites, contrary to the measurement of Miyamoto and Takeda. The compositional data, textural relations, and existence of P2₁ca hypersthene suggest at least a comparable if not slower cooling history for Serra de Magé.     

High-Precision Trace Element Data for the USGS Reference Materials BCR-1, BCR-2, BHVO-1, BHVO-2, AGV-1, AGV-2, DTS-1, DTS-2, GSP-1 and GSP-2 by ID-TIMS and MIC-SSMS

Different batches of the new US Geological Survey (USGS) reference materials (RMs) BCR-2, BHVO-2, AGV-2, DTS-2 and GSP-2 and the original USGS RMs BCR-1, BHVO-1, AGV-1, DTS-1 and GSP-1 have been analysed by isotope dilution using thermal ionisation mass spectrometry (ID-TIMS) and by multi-ion counting spark source mass spectrometry (MIC-SSMS). The concentrations of K, Rb, Sr, Ba and the rare earth elements were determined with overall analytical uncertainties of better than 1% (ID-TIMS) and 3% (MIC-SSMS). The analyses of different aliquots and batches of BCR-2, BHVO-2, AGV-2 and GSP-2, respectively, agree within 1%, i.e. approximately the analytical uncertainties of the data. This indicates an homogeneous distribution of the trace elements in these RMs. Differences in element concentrations of up to 17% in different aliquots of the depleted RM DTS-2 are outside the analytical uncertainty of our data. They may be attributed to a slightly heterogeneous distribution of trace elements in this dunite sample. Our trace element data for BCR-2, BHVO-2, AGV-2 and GSP-2 agree within about 3% with preliminary reference values published by the USGS. They also agree within 1-6% with those of the original RMs BCR-1, BHVO-1, AGV-1 and GSP-1. Large compositional differences are found between DTS-2 and DTS-1, where the concentrations of K, Rb, Sr and the light REE differ by factors of 2 to 24.     

Calibration of high-resolution geophysical data with tracer test measurements to improve hydrological predictions

Relationships between porosity and hydraulic conductivity tend to be strongly scale- and site-dependent and are thus very difficult to establish. As a result, hydraulic conductivity distributions inferred from geophysically derived porosity models must be calibrated using some measurement of aquifer response. This type of calibration is potentially very valuable as it may allow for transport predictions within the considered hydrological unit at locations where only geophysical measurements are available, thus reducing the number of well tests required and thereby the costs of management and remediation. Here, we explore this concept through a series of numerical experiments. Considering the case of porosity characterization in saturated heterogeneous aquifers using crosshole ground-penetrating radar and borehole porosity log data, we use tracer test measurements to calibrate a relationship between porosity and hydraulic conductivity that allows the best prediction of the observed hydrological behavior. To examine the validity and effectiveness of the obtained relationship, we examine its performance at alternate locations not used in the calibration procedure. Our results indicate that this methodology allows us to obtain remarkably reliable hydrological predictions throughout the considered hydrological unit based on the geophysical data only. This was also found to be the case when significant uncertainty was considered in the underlying relationship between porosity and hydraulic conductivity.     

U–Pb zircon and monazite age constraints on granulite-facies metamorphism and deformation in the Strangways Metamorphic Complex (central Australia)

The age of Proterozoic granulite facies metamorphism and deformation in the Strangways Metamorphic Complex (SMC) of central Australia is determined on zircon grown in syn-metamorphic and syn-deformational orthopyroxene-bearing, enderbitic, veins. SHRIMP zircon studies suggest that M ₁–M ₂ and the correlated periods of intense deformation (D ₁–D ₂) are part of a single tectonothermal event between 1,717±2 and 1,732±7 Ma. It is considered unlikely that the two metamorphic phases (M ₁, M ₂) suggested by earlier work represent separate events occurring within 10–25 Ma of each other. Previous higher estimates for the age of M ₁ granulite metamorphism in the SMC (Early Strangways event at ca. 1,770 Ma) based on U–Pb zircon dating of granitic, intrusive rocks, are not believed to relate to the metamorphism, but to represent pre-metamorphic intrusion ages. Conventional multi-grain U–Pb monazite analyses on high-grade metasediments from three widely spaced localities in the western SMC yield ²⁰⁷Pb/ ²³⁵U ages between 1,728±11 and 1,712±2 Ma. The age range of the monazites corresponds to the SHRIMP zircon ages in the granulitic veins and is interpreted to record monazite growth (prograde in the metasedimentary rocks). The data imply a maximum time-span of 30 Ma for high-grade metamorphism and deformation in the SMC. There is, thus, no evidence for an extremely long period of continuous high-temperature conditions from 1,770 to ca. 1,720 Ma as previously proposed. The results firmly establish that the SMC has a very different high-grade metamorphic history than the neighbouring Harts Range, where upper amphibolite facies metamorphism in the Palaeozoic caused widespread growth or recrystallization of monazite.