Petrogenesis of Basanitic to Tholeiitic Volcanic Rocks from the Miocene Vogelsberg, Central Germany

The Miocene Vogelsberg volcano in Central Germany produced maficmagmas ranging in composition from basanite to quartz tholeiiteand limited amounts of evolved magmas. Trace element and Nd,Sr and Pb isotopic compositions reveal the presence of threedistinct mantle sources: (1) a trace element enriched, asthenosphericplume-type source, similar to the European Asthenospheric Reservoircomposition inferred for many other Tertiary volcanic provincesin Central Europe; (2) a depleted mantle source, located inthe lithospheric mantle or uppermost asthenosphere; (3) a veinedlithospheric mantle source. The oldest basanites of the Vogelsbergvolcano have distinctly higher Ti, Al, Sc and V contents thanyounger basanites. These high-Ti basanites may have been producedby partial melting of a veined lithospheric mantle source, formedduring the earliest stages of uplift of the Rhenish Shield,     

Clay Minerals in Basalt Sills from the Sediment Cover,East Pacific Rise

Clay minerals in basalt sills from the northern East Pacific Rise, covered by Upper Pleistocene clayey–sandy–silty sediments (turbidites, hemipelagites, and diatom oozes) sampled from DSDP Holes 477, 478, and 481A, were studied by X-ray methods based on the modeling of diffraction patterns. Trioctahedral smectites formed in thin (0.1–0.5 and 1.8–4 m) fissured sills that are well permeable for water delivered from the water-saturated host sediments heated by the sills. Smectites in basalts are found in the interstices (20–40 vol % in the rock and up to 50–80 vol % in hyalobasalts). They replace olivine and fill cracks and vesicles. Plagioclase and clinopyroxene are generally unaltered. The structure of smectites is characterized by different height of layers depending on the composition of cations in the interlayers and the degree of their hydration. The different-height layers either make up individual smectite phases or alternate in different proportions and with a high degree of segregation in the mixed-layer structures. Under conditions of a prolonged cooling, thick (43 m) sills are distinguished from the thin varieties by the formation of trioctahedral minerals (smectite–chlorite, chlorite, defective chlorite, and talc). They are found mainly in the interstices that make up 3–7 vol % of the rock.     

Petrology of garnet-, spinel-, and sillimanite-bearing granites from the bavarian forest,West Germany

Mineralogy and Petrology - Samples from 17 small granitic intrusions of late-Variscan age have been investigated for their chemical compositions and petrographic characteristics. All of them...     

Comprehensive Chemical and Isotopic Analyses of Basalt and Sediment Reference Materials

Geochemical studies of geological samples require the precise determination of their major and trace element contents and, when measured, of their isotopic compositions. It is now commonly accepted that the accuracy and precision of geochemical analyses are best estimated by the concomitant analysis of international reference materials run as unknown samples. Although the composition of a wide selection of basalts is relatively well constrained, this is far from being the case for sedimentary materials. We present here a comprehensive set of major and trace element data as well as Nd, Hf, Sr and Pb isotopic compositions for thirteen commonly used international reference materials – eight magmatic rocks (BHVO‐2, BR, BE‐N, BR 24, AGV‐1, BIR‐1, UB‐N, RGM‐1) and five sediments (JLk‐1, JSd‐1, JSd‐2, JSd‐3, LKSD‐1). We determined the concentrations of over forty elements in the magmatic rocks together with Sr, Nd, Hf and Pb isotopic compositions. Our trace element results were both accurate (difference ≤ 3%) and precise (reproducibility at 1s ≤ 3%) and the isotopic results were very similar to other published values. In contrast, we observed a significant chemical and isotopic variability in the sedimentary materials, which we attribute to mineral heterogeneities in the powders. Despite the limitation imposed by this heterogeneity, our work presents a complete set of data determined with a precision not yet achieved in the literature for sedimentary material. We also provide the first Nd, Hf and Pb isotopic measurements for the five sediments, which are commonly used by the geochemical community. Our study of both basalt and sediment reference materials represents a comprehensive and self‐consistent set of geochemical data and can therefore be considered as a reference database for the community.     

Os isotopes in mantle xenoliths from the Eifel volcanic field and the Vogelsberg (Germany): age constraints on the lithospheric mantle

The effects of mantle metasomatism on the sulfide phase in mantle xenoliths in general, and on the Os isotopic system in particular, have received increased attention in recent years. Here, we report on Os isotopic systematics of metasomatized mantle xenoliths from the late Quaternary Eifel (Dreiser Weiher and Meerfelder Maar) and neighboring Vogelsberg volcanic fields, which provide insight into the effects of melt extraction and metasomatism on Os isotopes and place constraints on the evolution of the lithospheric mantle component beneath central Europe. Sixteen harzburgite, lherzolite, and pyroxenite xenoliths from the Eifel and two lherzolite xenoliths from the Vogelsberg were analyzed for Os isotopes. Samples from the anhydrous peridotite suite (Ib) are highly variable in their Os isotopes, ranging from subchondritic values (¹⁸⁷Os/¹⁸⁸Os=0.1236) to suprachondritic values (¹⁸⁷Os/¹⁸⁸Os=0.1420), indicating that some of these samples have been overprinted by the addition of radiogenic Os and have lost the primary mantle Os that was presumably present. The suprachondritic values suggest a source for this Os in a reservoir with a time-integrated Re/Os ratio greater than that of the bulk Earth. Eifel samples with Os contents >1.5 ng/g from the hydrous suite (Ia) have relatively unradiogenic Os isotope compositions (¹⁸⁷Os/¹⁸⁸Os=0.1208-0.1237) and Al₂O₃-Os isotopic systematics consistent with ancient melt depletion and isolation from the convecting asthenospheric mantle for time periods similar to the age of the overlying crust (~1.5 Ga) as well with results from peridotite massifs in the European region. The LREE-metasomatism and the enrichment of Os (up to 6.47 ng/g) and As (sulfide metasomatism?) in the hydrous suite is strongly inversely correlated with the Os isotope ratios, demonstrating that mantle processes such as metasomatism can significantly modify the Os isotope chemistry of mantle xenoliths.     

Petrology and genesis of Upper Carboniferous seams from the Ruhr region,West Germany

The petrology of 21 seam profiles of Upper Carboniferous age (Westphalian C and B) has been studied in order to determine their depositional environments and diagenetic history. The youngest profile was drilled at a depth of 790 m and is mainly overlain by Cretaceous sediments. The oldest seam was reached at a depth of 1470 m. The seam thicknesses vary from 0.4 to 2.5 m.The main petrographic compounds are vitrinite, intertinite, liptinite, and minerals. The last group occurs as clay bands with illite, kaolinite, minor chlorite, and minor quartz contents, or as crack- or pore-filling calcite, Fe-dolomite, siderite, pyrite, or marcasite, or as syngenetic siderite concretions and pyrite crystals. The percentages of the different macerals and minerals vary mainly because of different depositional environments. Diagenetic loss or genesis of compounds is a less important factor in their distribution.Three types of profiles are distinguished by their different petrologies. Type I is most abundant, and contains much vitrinite, many clay bands, and syngenetic iron sulfides, whereas type III is rich in inertinite and certain characteristic spores. Type II is intermediate but generally contains only low percentages of minerals. Generally, this type is vitrinite-rich in the lower, and inertinite-rich in the central and upper parts of the profiles. Spores and other liptinites are much better preserved in all the seams than in clay partings or in siltstones and sandstones above and below the seams.The seams are interpreted to be former autochthonous peats. Type I profiles are probably derived from swamps which were sometimes inundated and covered by overbank deposits. Type II and III seams represent former peats which were not inundated by rivers, and partly grew under the influence of more oxidizing conditions. Therefore, they contain more inertinite and less sulfide and clay bands. They can be interpreted as former raised bogs.Diagenetic changes are expressed as increases of vitrinite reflectances (from 0.65% to 1.0%), and of liptinite reflectances; a red shift of fluorescence of liptinites was found; increasing amounts of exudatinite (and micrinite) and decreasing amounts of fluorinite and resinite were found. Minerals seem to be less affected by diagenesis; illite crystallinity, for example, remains poor.     

Geochemistry and mineralogy of two spinel peridotite suites from Dreiser Weiher,West Germany

Among the spinel peridotite nodules from Dreiser Weiher. West Germany which represent fragments of the earth's upper mantle two series may be distinguished. One group (Ib) is anhydrous while the second one (Ia) is characterized by the presence of amphibole and/or breakdown-products of amphibole. Both suites display a wide range in modal composition. Pyroxene geothermometry yields equilibration temperatures of ~ 1150°C for group Ib and ~950°C for group Ia.Rare earth element (REE) patterns reveal marked differences between both groups: nearly unfractionated, light REE depleted or slightly light REE enriched chondrite normalized patterns in nodules from group Ib, but a high relative light REE enrichment in the amphibole containing suite Ia. An inverse correlation between the clinopyroxene content (or CaO) and relative light REE enrichment is observed in group Ia only. Two sources of light REE enrichment of the nodules can be distinguished: The first is a contaminant on mineral surfaces and can be removed by acid leaching. The second is an integral part of the constituent minerals of the nodules. Trace element abundances and modelling show that nodules of group Ib cannot be derived from upper mantle pyrolite by a one-stage partial melting process. Nodules of type Ia are interpreted as being the result of a reaction between Ib-type mantle and a fluid or liquid which provides H₂O and incompatible elements. At Dreiser Weiher this ‘open system’ upper mantle metasomatism may be related to the young uplift of the Rhenish Shield in a similar way as previously proposed by Lloyd and Bailey (1975).A model for the lithospheric mantle below the Westeifel is different from the San Carlos model proposed by Frey and Prinz (1978) and more complex.     

Imnaha Basalt, Columbia River Basalt Group

The Columbia River volcanic episode began with the eruptionof the coarsely porphyritic Imnaha Basalt between 17.0 and 16.5m.y. B.P. Lava poured from NNW trending vertical fissures andlocal vents north and south of the Seven Devils-Wallowa Mountainsdivide, covering a deeply dissected topographic surface of morethan 30, 000 km², with an estimated volume of 6000 km³. A minimumof 26 flows or flow units are represented in 14 or 15 members.These include 11 chemical types and are exposed in sectionsranging to 577 m in thickness. All flows have normal polaritywith the exception of the youngest and oldest whose polarityis either reversed or transitional. The petrologic and majorelement chemical features of the Imnaha Basalt have much incommon with those of the Picture Gorge Basalt exposed in theJohn Day Basin of north-central Oregon, but the latter is younger,equivalent in age to part of the Grande Ronde Basalt formation. Using major and trace elements, the flows of Imnaha Basalt areclearly distinguished from those of all other formations ofthe Columbia River Basalt Group. Imnaha Basalt has lower SiO₂,K₂O, Ba and Rb than does Grande Ronde Basalt and differs frommost Wanapum and Saddle Mountains Basalt flows in its lowerTiO₂ and P₂O₅ contents. The 11 Imnaha chemical types fall into two subgroups, the AmericanBar (AB) and Rock Creek (RC) subgroups, which differ in thecoarseness of their groundmass, the abundance of olivine, theirphenocryst assemblages, their SiO₂ contents, CaO/Al₂O₃ ratio,and in their Sc, V, Sr, and Ni contents. Flows of the two subgroupsinterdigitate, but AB flows are predominant at the base of thesequence and RC flows at the top. One flow is a hybrid of thetwo magma types. Neither subgroup displays a significant variation in SiO₂ content,but each does show systematic variation in K₂O, P₂O₅, TiO₂,Ba, Zr, Rb, and the REE, all of which vary inversely with MgO/(MgO+ FeO + Fe₂O₃). AB flows show a systematic increase in contentsof the incompatible elements upward in the succession, whileRC flows show a less obvious decrease upwards. Modelling of major and trace elements indicates that the chemicalvariations within each subgroup can be explained by simultaneouscrystal fractionation and assimilation of lower crustal material,in which the mass assimilated is only slightly less than thatlost by crystal fractionation; the mass fractionated varyingup to 50 per cent and the mass assimilated up to 42 per centof the original magma mass. These processes alone cannot explainthe relationships between the two Imnaha subgroups, nor thatbetween either subgroup and the overlying aphyric Grande Rondebasalt. The value of more complex quantitative models, in whichrecharge by more primitive magma, a variable composition forthe lower crustal contaminant, and the partial melting of aheterogeneous source, is limited by lack of data. Some suchprocess, or combination of processes in addition to a combinationof crystal fractionation and lower crustal assimilation, wouldseem to be required to account for the diversity in the earliestColumbia River basalts.     

Carbonatite in the tuffs of the West Eifel,Germany

Newly-discovered carbonatitic fragments from the West Eifel are described in terms of their petrography and trace-element content.     

Sediment dispersal and quantitative stratigraphic architecture across an ancient shelf

Two large (200 to 300 km), near‐continuous outcrop transects and extensive well‐log data (ca 2800 wells) allow analysis of sedimentological characteristics and stratigraphic architecture across a large area (ca 60 000 km²) of the latest Santonian to middle Campanian shelf along the western margin of the Western Interior Seaway in eastern Utah and western Colorado, USA. Genetically linked depositional systems are mapped at high chronostratigraphic resolution (ca 0·1 to 0·5 Ma) within their sequence stratigraphic context. In the lower part of the studied interval, sediment was dispersed via wave‐dominated deltaic systems with a ‘compound clinoform’ geomorphology in which an inner, wave‐dominated shoreface clinoform was separated by a muddy subaqueous topset from an outer clinoform containing sand‐poor, gravity‐flow deposits. These strata are characterized by relatively steep, net‐regressive shoreline trajectories (>0·1°) with concave‐landward geometries, narrow nearshore belts of storm‐reworked sandstones (2 to 22 km), wide offshore mudstone belts (>250 km) and relatively high sediment accumulation rates (ca 0·27 mm year^?1). The middle and upper parts of the studied interval also contain wave‐dominated shorefaces, but coeval offshore mudstones enclose abundant ‘isolated’ tide‐influenced sandstones that were transported sub‐parallel to the regional palaeoshoreline by basinal hydrodynamic (tidal?) circulation. These strata are characterized by relatively shallow, net‐regressive shoreline trajectories (<0·1°) with straight to concave‐seaward geometries, wide nearshore belts of storm‐reworked sandstones (19 to 70 km), offshore mudstone belts of variable width (130 to >190 km) and relatively low sediment accumulation rates (ca ≤0·11 mm year^?1). The change in shelfal sediment dispersal and stratigraphic architecture, from: (i) ‘compound clinoform’ deltas characterized by across‐shelf sediment transport; to (ii) wave‐dominated shorelines with ‘isolated’ tide‐influenced sandbodies characterized by along‐shelf sediment transport, is interpreted as reflecting increased interaction with the hydrodynamic regime in the seaway as successive shelfal depositional systems advanced out of a sheltered embayment (‘Utah Bight’). This advance was driven by a decreasing tectonic subsidence rate, which also suppressed autogenic controls on stratigraphic architecture.     

Ice-marginal debris-flow deposits in western Allgau, southern West Germany

Ice-marginal debris-flow deposits (comparable to deposits elsewhere described as flow tills) are described from glacier-proximal sediments in an Alpine foreland area. Debris-flow deposits are characteristically interstratified with subaeric or subaquatie meltwater deposits, and occur in a wide variety of geomorpho-logical settings. The granulomctric composition of debris-flow deposits is more variable than that of subglacial tills. Within-flow variability may occur as a result of the formation of graded bedding, lateral as well as vertical. Clast fabrics show both random and preferred orientations; unequivocal interpretation of these is not possible. Debris-flow deposits are composed of material derived from various sources: sources from subglaeially-derived debris as well as from previously deposited tills and walerlain sediments can be demonstrated.     

Granulite facies lower crustal xenoliths from the Eifel,West Germany: petrological and geochemical aspects

Petrographic, petrological and geochemical data for 16 mafic meta-igneous, granulite facies lower crustal xenoliths from the East Eifel were collected in order to develop a model for the lower crustal history for this region. The xenoliths consist of plagioclase±amphibole±clinopyroxene±garnet±orthopyroxene±scapolite + opaque minerals±apatite±rutile±zircon. Garnet has reacted to a variable extent with plagioclase and clinopyroxene to form a corona of plagioclase_II+ amphibole + orthopyroxene_II. Pyroxenes and plagioclases show complex zoning patterns with regard to Al and Ca which can be interpreted in terms of P, T history. Decreasing temperature and pressure conditions are recorded by decreasing Al in clinopyroxene rims coexisting with increasing anorthite contents in plagioclase rims and the breakdown of garnet. In addition, a young heating event that affected the granulites to different degrees is inferred from the complementary Ca-zoning patterns in clino- and orthopyroxenes. Rare earth element (REE) patterns of whole rocks together with the trends displayed and fractionated liquids. REE analyses of the mineral separates display equilibrium partitioning patterns for amphibole and clinopyroxene, although isotopic data show that amphibole contains externally-derived Sr and Nd components not recognized in other minerals. At least a 4-stage history for the granulites is recorded: (1) intrusion and crystal fractionation of basaltic magmas in the lower crust, probably accompanied by crustal assimilation, (2) granulite facies metamorphism, (3) a decrease in temperature and pressure, and (4) a later heating event. The complicated thermal history is reflected in Sm–Nd mineral isochron ages which range from about 170 Ma down to about 100 Ma and cannot be assigned to distinct geological events. These ages correlate with inferred temperatures; the low ages are measured for xenoliths with the highest temperatures. In some cases the young heating event is likely to be responsible for partial resetting of the mineral isochrons.     

Sediment dispersal and accumulation in tectonic accommodation across the Gaoping Slope,offshore Southwestern Taiwan

Distribution and architecture of slope basins across a continental slope vary as a consequence of accommodation forming, sediment dispersal rates, canyon cutting, sediment filling and different sediment transporting mechanisms. The area offshore Southwestern Taiwan is generally recognized as having active tectonics and high sediment deposition rates. In the Gaoping Slope, slope basins are formed by the developments of folds, faults and diapiric intrusions. Portions of the sediments discharged from the Taiwan mountain belt have been trapped in these basins in the Gaoping Shelf and Gaoping Slope. The rest of the sediments were transported to deep sea areas through submarine canyons. This complex system of folds, faults, diapirs, slope basins, submarine canyons, and sediment deposits has also readjusted the morphology of the Gaoping Slope. This study examines the linkage between accommodation spaces of tectonic and sedimentary processes in the Gaoping Slope through seismic facies analysis. Four seismic facies which include convergent-symmetrical facies, convergent-baselapping facies, chaotic facies, and parallel and drape facies, and different deposition patterns have been recognized in the Gaoping Slope basins. The thick mud layers which are regarded as the source of diapiric intrusions are first observed beneath the basin. Strata records show that the accommodation spaces in various slope basins have increased or decreased during different stages of basin evolution. Because of the competition between regional tectonism (accommodation space variations) and sediment routing distance from provenance to depository (sediment input variations), most under-filled basins lie in the lower slope domain in the Gaoping Slope, but also in the upper slope domain east of the Gaoping Submarine Canyon. This observation suggests that in the inner Gaoping Slope west of the Gaoping Submarine Canyon, sediment deposition rate is higher than the basin subsidence rate, the topography of the upper slope domain there is “healed”, and most sediments are overfilled in the slope basins now. Besides the sequential steps of sedimentary disposal in the filling-and-spilling model, we have also observed evidences which indicate that mass movements and submarine canyons in the area have significantly changed the sediment dispersal patterns in the slope basins of the Gaoping Slope. We suggest that although filling-and-spilling is a key sedimentary process in the Gaoping Slope, tectonic activities, mass wasting events and canyon feeding processes have diversified sediment transporting mechanisms from the inner to outer slopes in the area offshore Southwest Taiwan.     

Origin of glass in upper mantle xenoliths from the quaternary volcanics of Gees,West Eifel,Germany

Glasses have been analysed from six mantle-derived xenoliths (5 orthopyroxene and/or olivine-rich, 1 clinopyroxene-rich) from the Quaternary volcanics S.E. of Gees, West Eifel, Germany. The glasses in these xenoliths occur as pools surrounding and embaying spinels, as inclusions in spinels, as veins and stringers within phlogopiterich veins, and as jackets partially surrounding some of the xenoliths. Glasses analysed are felsic and characterised by low to intermediate SiO₂ (40–62 wt.%), variable CaO (1–11 wt.%) and MgO (1–4 wt.%), high Al₂O₃ (14–21 wt.%), and up to 11 wt.% Na₂O + K₂O. The jacket glasses have the lowest SiO₂, highest CaO and MgO. Variations in all of the glass compositions are similar and imply a unifying factor or process in their formation. Glass as pools and stringers within veins of phlogopite forms part of the same trends shown by all the glasses when plotted on bivariate (oxide vs SiO₂) diagrams but can be distinguished from glass surrounding and enclosed by spinels. Glasses occurring as jackets are similar in composition to those in pools and veinlets associated with phlogopite but are of quite different composition to the glasses found within the xenoliths that they partially enclose. The occurrence and chemistry of the glasses do not support such glasses as representing original or differentiated magma trapped during formation of the xenolithic assemblages. The chemistry of the glasses also makes it unlikely that they were produced by dissociation of phlogopite during ascent of the xenoliths. The most likely origin for the glasses is that they represent volatile-rich melts which migrated through upper mantle material. These melts are likely to be responsible for the heterogeneous nature of the mantle underlying this part of the West Eifel region.     

Temperature History of Sheared Mantle Xenoliths from the West Eifel, West Germany: Evidence for Mantle Diapirism Beneath the Rhenish Massif

Mantle xenoliths from the West Eifel, West Germany revealingdistinct disequilibrium textures were formed by strong sheardeformation from coarse grained, high temperature spinel peridotites.Foliated structures are caused by the roughly parallel alignmentof elongated orthopyToxenc porphyroclasts up to 8 ? 2 mm insize and streched patches of clinopyroxene and spinel in a matrixof recrystallized olivine, orthopyroxene, clinopyroxene, andspinel. Bulk chemical disequilibrium finds its expression in a highdegree of chemical heterogeneity which is most evident in orthopyroxene.In orthopyroxene porphyroclasts, unmixed lamellae of clinopyroxeneand chromium-aluminium spinel are confined to the grain cores,because concentration gradients of Al, Cr, and Ca existed atthe time of their exsolution. Orthopyroxene neoblasts also revealdiffusion controlled concentration gradients of Al, Cr, andCa, which decrease from core to rim. The temperature historydetermining the orthopyroxene chemistries was derived from Al-solubilitiesin orthopyroxene using an empirical geothermometer. From thetextural relationships, in conjunction with the temperaturehistory, it is inferred that the shear process causing the deformationof the porphyroclastic xenoliths was associated with a temperaturedecrease from at least 1100 to about 800?C. The observed linkage of deformation and cooling in the xenolithsis related to the diapiric uplift of hot mantle material intoa cooler uppermost mantle beneath the West Eifel. It rules outa deformation due to secular mantle flow or movements along‘cold’ shear zones.     

Stress orientations found in north-east Germany differ from the West European trend

Knowledge about the acting stresses is of crucial importance for understanding the tectonics of a region. Data about the stress field in north-eastern Germany used to be very rare. In general, it was assumed that the orientation of the larger horizontal principal stress (S_H) is similar to that found for western Germany and central West-Europe, i.e. NW–SE. To check this, several borehole logs of the late 1980s were analysed for information on the principal horizontal stress orientations: they include Four-Arm-Dipmeter and borehole televiewer data from 15 boreholes. The depth range of our stress results reaches from 1500 to 6700 m. They were compared to a few other data, especially from hydraulic fracturing, and to recent findings on the stresses in the Northwest German basin. In contrast to expectation, S_H derived from breakout orientations below the salt layers displayed N to NE orientation. The latter was found at 10 locations spread over the NE-German basin from Berlin to the Baltic sea, from the Polish border to the former border between East and West Germany. Moreover, this stress rotation in the subsaline formations seems to be the continuation of a trend found in the NW German basin.     

Anthropogenic effects on sedimentary facies in Lake Baldeney,West Germany

Analysis of well logs of Lake Baldeney, a reservoir of the Ruhr River, yields four facies factors that reflect the effect of anthropogenic processes on the sediment. First, the sedimentation rate is directly related to the subsidence caused by mining. The extent of the subsidence was such that the sediment load of the river could not compensate for the sinking of the lake bottom. Discharged sediment filled about one-fifth of the basin within 40 years. In certain areas of the basin the sedimentation rate reached up to 10 cm per year. Second, the grain-size distribution of the sediment was influenced by long-term and short-term events. During the subsidence, grain-size distribution remained relatively constant. The destruction of the Möhne River dam during World War II resulted in the presence of an extremely large grain size as evidenced by the so-calledMöhnelage. The filling of the lake after 1961 was accompanied by a continual increase in medium grain size. Third, until 1975, the mode of the lake sediment reflects the effect of mining in the vicinity of the lake. High coal content can be traced to its origin. The introduction of modern production processes, modernization of coal dressing, and hydraulic hauling is documented in the sediment. Finally, the heavy metal content of the sediment corresponds to the industrial development in the drainage area the Ruhr River. The accumulation of Cd reached an extreme concentration, exceeding the natural content by a thousand times. Variation in concentration reflects an increase in industrial production, as well as measures undertaken to restore water quality.     

Granulite-facies metabasite ejecta in the Laacher See area,Eifel, West Germany

Near the village of Engeln, Laacher See area, garnet-bearing pyriclasite and pyribolite ejecta were recognized as constituents of alkaline basaltic tuffs; they are interpreted as fragments of the lowermost crust. During the first main stage of granulite facies metamorphism, assemblages with garnet (Alm₄₇Pyr₃₄Spess₂Gross + Andr₁₇), clinopyroxene (Wo₃₇En₃₅Fs₁₅Ts_8.5Jd_4.5), orthopyroxene I (En₃₄Fs₃₈Ts₄Jd₂), and plagioclase I (An₄₀-An₆₀) were formed in a temperature range of 730–850°C and rock pressures somewhere between 6.5 and 12 kb, $\text{P}{}_{\mathrm{tot}}\text{>}\text{P}{}_{\mathrm{<mtext>H</mtext>}}{}_2\text{O}\text{> 0}$. The rare sulfate-rich meionite, and at least a part of the ubiquitous brown hornblende were presumably also formed during this stage. A retrograde metamorphic event under slightly lower pressures and temperatures led to the breakdown of the assemblage garnet + clinopyroxene thereby forming coronas of plagioclase II $\text{(}\text{An}{}_{75}\text{) +}\text{orthopyroxene}\text{II +}\text{Ti-magnetite}\text{±}\text{brown hornblende}$.     

Sediment dispersal and palaeohydraulics of Oligocene rivers in the eastern Ebro Basin

Mapping of heavy mineral associations and diagnostic accessories in Oligocene sediments of the eastern Ebro Basin has revealed two major provinces and several sub-provinces. The Pyrenean Province is characterized by an apatite-tourmaline-garnet association with diagnostic staurolite in the west (western Pyrenean Sub-Province) and micaceous composite grains plus chloritoid in the east (eastern Pyrenean Sub-Province). The Catalanides Province is characterized by an ultrastable angular brown tourmaline-staurolite association with kyanite in the south-west (Montsant Sub-Province), faceted garnets and rounded tourmalines in an intermediate position (St Miquel del Montclar Sub-Province) and in the north-east rounded and green tourmalines admixed with clinopyroxene, apatite and micas derived from the Pyrenees (Montserrat Sub-Province). Palaeodischarges have been estimated from 30 channels distributed throughout both major provinces. A gradual decrease in river discharge through Oligocene times is indicated for the rivers of Catalanides parentage, although the discharges of high-sinuosity streams alone remain uniform. This decrease through time of Catalanides drainage competitiveness is reflected in the greater areal extent of the Pyrenean petrological province together with a progressive displacement south or south-eastwards of basinal lacustrine facies. The increasing dominance of Pyrenean drainage during the Oligocene may be due to more prolonged tectonic activity in the Pyrenees compared to the more quiescent Catalanides.