Hornblenden aus Eklogiten und Amphiboliten der südlichen Koralpe

Inhalt Hornblenden aus Eklogiten und Amphiboliten der südlichen Koralpe werden chemisch und optisch untersucht; außerdem sind die Gitterkonstanten der Hornblenden bestimmt worden.Herrn Prof. Dr.K. H. Scheumann in Verehrung zum 80. Geburtstag gewidmet.     

A survey to determine levels of chlorinated pesticides and PCBs in mussels and seawater from the Mid-Black Sea Coast of Turkey

A mussel and seawater monitoring survey was conducted at six sampling points between Yalikoy (Ordu) and Sinop in 1999-2000 along the Mid-Black Sea Coast of Turkey in order to assess concentrations of organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs). Chlorinated pesticides and PCBs were measured in the mussel Mytilus Galloprovincialis and in seawater. In the mussel samples, the most common pollutants in terms of average concentration per g of wet weight (ww), were DDT (max. 1800 pg/gww, min. 240 pg/gww) and its metabolites DDD (max. 5400 pg/gww, min. 240 pg/gww) and DDE (max. 2800 pg/gww, min. 70 pg/gww). Also, dieldrin, heptachlor and HCB were notable contaminants in the mussel samples. PCBs were determined in none of the biota or seawater samples. The concentrations of the OCs and PCBs in mussels were higher in coastal areas receiving river discharges and close to the largest city of the region, Samsun (especially in sampling points in the harbour area). The well-known long persistence of DDTs and other chlorinated compounds was confirmed by residues of these pollutants measured in mussels. On the other hand, even though the usage of such kind of persistent compounds in Turkey was banned, there may still be illegal usage and it is not certain whether the application of these compounds did end in the region.     

Carbonates and Sulfates in CI Chondrites: Formation by Aqueous Activity on the Parent Body

Abstract— Compositions and morphologies of dolomites, breunnerites, Ca-carbonates, Ca-sulfates and Mg, Ni, Na-sulfates, and their petrologic interrelations, in four CI chondrites are consistent with their having been formed by aqueous activity on the CI parent body. Radiochronometric data indicate that this activity took place very early in Solar-System history. No evidence for original (“primitive”) condensates seems to be present. However, alteration apparently took place without change in bulk meteorite composition.     

Re-evaluation of the petrogenesis of the Proterozoic Jabiluka unconformity-related uranium deposit, Northern Territory, Australia

The world class Jabiluka unconformity-related uranium deposit in the Alligator Rivers Uranium Field, Australia, contains >163,000 tons of contained U₃O₈. Mineralization is hosted by shallow-to-steeply dipping basement rocks comprising graphitic units of chlorite–biotite–muscovite schist. These rocks are overlain by flat-lying coarse-grained sandstones belonging to the Kombolgie Subgroup. The deposit was discovered in 1971, but has never been mined. The construction of an 1,150 m decline into the upper eastern sector of the Jabiluka II deposit combined with closely spaced underground drilling in 1998 and 1999 allowed mapping and sampling from underground for the first time. Structural mapping, drill core logging and petrographic studies on polished thin sections established a detailed paragenesis that provided the framework for subsequent electron microprobe and X-ray diffraction, fluid inclusion, and O–H, U–Pb and ⁴⁰Ar/³⁹Ar isotope analysis. Uranium mineralization is structurally controlled within semi-brittle shears that are sub-conformable to the basement stratigraphy, and breccias that are developed within the hinge zone of fault-related folds adjacent to the shears. Uraninite is intimately associated with chlorite, sericite, hematite ± quartz. Electron microprobe and X-ray diffraction analysis of syn-ore illite and chlorite indicates a mineralization temperature of 200°C. Pre- and syn-ore minerals extracted from the Kombolgie Subgroup overlying the deposit and syn-ore alteration minerals in the Cahill Formation have δ¹⁸O_fluid and δD _fluid values of 4.0±3.7 and −27±17‰, respectively. These values are indistinguishable from illite separates extracted from diagenetic aquifers in the Kombolgie Subgroup up to 70 km to the south and east of the deposit and believed to be the source of the uraniferous fluid. New fluid inclusion microthermometry data reveal that the mineralising brine was saline, but not saturated. U–Pb and ²⁰⁷Pb/²⁰⁶Pb ratios of uraninite by laser-ablation ICP-MS suggest that massive uraninite first precipitated at ca. 1,680 Ma, which is coincident with the timing of brine migration out from the Kombolgie Subgroup as indicated by ⁴⁰Ar/³⁹Ar ages of 1,683±11 Ma from sandstone-hosted illite. Unmineralized breccias cemeted by chlorite, quartz and sericite cross-cut the mineralized breccias and are in turn cut by straight-sided, high-angle veins of drusy quartz, sulphide and dolomite. U–Pb and ²⁰⁷Pb/²⁰⁶Pb ratios combined with fluid inclusion and stable isotope data indicate that these post-ore minerals formed when mixing between two fluids occurred sometime between ca. 1,450 and 550 Ma. Distinct ²⁰⁷Pb/²⁰⁶Pb age populations occur at ca. 1,302±37, 1,191±27 and 802±57 Ma, which respectively correlate with the intrusion of the Maningkorrirr/Mudginberri phonolitic dykes and the Derim Derim Dolerite between 1,370 and 1,316 Ma, the amalgamation of Australia and Laurentia during the Grenville Orogen at ca. 1,140 Ma, and the break-up of Rodinia between 1,000 and 750 Ma.     

Retrieval of P–T information from shear zones: thermobarometric consequences of changes in plagioclase deformation mechanisms

Changes in deformation mechanism coupled with spatial and temporal variations in reaction rates can result in preservation of disequilibrium mineral compositions in rocks affected by synmetamorphic shearing. Thermobarometric calculations on such rocks may thus yield meaningless results. We use Garbenschiefer samples from a shear zone in the Eastern Alps to study the effects of different deformational processes on calculated pressures and temperatures in samples that experienced the same overall PTt history. We focus on plagioclase, which accommodates strain by a variety of deformation mechanisms and is a key mineral in many thermobarometers. Plagioclase that deformed largely via dislocation creep mechanisms shows concentric chemical zoning, whereas plagioclase that experienced dissolution-precipitation creep preserves complex zoning. Rim compositions in the latter domains are not necessarily the youngest compositions, nor did they typically equilibrate with other phases in the assemblage. The timing of hornblende breakdown reactions relative to changes in plagioclase deformation mechanism also affected chemical zoning. Samples that escaped shear strain while near the thermal maximum yield internally consistent thermobarometric results, whereas samples that experienced shearing near the thermal maximum yield scattered results. Some of the variability in the results likely represents real differences in the P–T conditions at which equilibration occurred during deformation. However, much of the variability represents spurious results obtained by pairing mineral compositions that were never in equilibrium with one another. Extraction of useful P–T information from samples that experienced synmetamorphic deformation requires careful documentation of the relationships between deformation mechanisms and chemical zoning in order to select appropriate mineral compositions for thermobarometric calculations.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Mouvements actuels des blocs tectoniques dans l’arc Bético-Rifain à partir des mesures GPS entre 1999 et 2005

GPS velocities and seismicity across the Betic–Rif Arc structural domains (Morocco and Iberia) provide a basis to evaluate present-day seismotectonic processes between different deformation belts. The results show asymmetric movements in the complex Alboran system accommodating the convergence between the African (Nubian) and Eurasian plates. While the Betic Mountains are attached to Iberia, moving toward the southeast with respect to Africa, the Rif is divided into three blocks with distinct displacements relative to Nubia: (1) the Tangier block moving southeastward, (2) the Central Rif block moving SSW, and (3) the Oriental Rif block undergoing clockwise rotation. GPS-derived motions decrease in rate from the Rif nappes complex to the foreland.