Limnological response to the Laacher See eruption (LSE) in an annually laminated Allerød sediment sequence from the Nahe palaeolake,northern Germany

This paper presents evidence for a limnological response to the Laacher See eruption (LSE) as detected in lake sediments from Nahe, northern Germany. The sediment section of the Allerød period dating to between 13 422 and 12 708 cal. a BP is preserved in annual laminations. Within this section, the LSE was identified as a cryptotephra layer (12 944±44 cal. a BP). Microfacies analysis, continuous high-resolution geochemical measurements and pollen analyses enabled a high-resolution reconstruction of environmental change. The older part of the Allerød (c. 13 422 to 12 943 cal. a BP) was characterized by relatively stable sedimentation conditions. Evidence for windier conditions dating to c. 13 160 to 13 080 cal. a BP probably reflects the Gerzensee oscillation. Pronounced changes of the lake sedimentation followed the LSE. Four unusually thick varves with increased amounts of allochthonous material indicate serious disturbance of the local environment immediately after the LSE, related to increased storminess and/or the occurrence of high intensity rainfall events. A pronounced reduction of biogenic silica accumulation for c. 60 years after the LSE could reflect a period of acidification. Indications of a simultaneous lake level increase until c. 60 years after the LSE are in line with the supposed reduced evapotranspiration associated with cooler conditions. About 120 years after the LSE, increased oxygen access at the lake bottom, allochthonous input and Cl fluxes point to an onset of increasingly stronger westerly winds, probably as a long-term response to the LSE. This supports the idea of a southward shift of the mid-latitude westerlies wind system within the interval between the LSE and the beginning of the Younger Dryas. The pace of the southwards shift of this wind system decreased from 10 km a⁻¹ in the initial phase (40–120 years after LSE) to 6 km a⁻¹ in the later phase (120–200 years after LSE).     

Gold in vegetation and soil — three case studies from the goldfields of southern Western Australia

Biogeochemistry has not been widely used as an exploration technique for Au in Western Australia because (1) sampling of soils and other surficial materials have been reasonably effective in finding new mineral deposits, and (2) it has been difficult to identify a consistent and regionally typical vegetation sample type. The potential of the technique has been tested at three sites in the goldfields of southern Western Australia. Vegetation and soil were analysed for Au from the Bounty (Mt Hope), Panglo and Zuleika Au deposits in the southern Yilgarn Craton. Gold concentrations in vegetation were generally lower at Panglo and Zuleika compared with Bounty, and probably reflect the depth to mineralization which is considerably greater at Panglo (40 m) and Zuleika (20 m) than at Bounty, where it is close to the surface. At Bounty, Au concentrations in dried vegetation varied from < 0.5 ppb in background areas to a maximum of 11 ppb (the highest for any area) over mineralization. In general, the association between Au concentrations in vegetation and mineralization is only weak although, at Zuleika, Maireana (bluebush) seemed a slightly better sample medium than soil for predicting the location of underlying mineralization.As the emphasis in exploration changes to more difficult terrains, the suitability of biogeochemistry needs to be re-examined. These preliminary results from Western Australia suggest that biogeochemistry may have some role to play in the search for deeply buried mineral deposits.     

The Composition of Melt Inclusions in Minerals from Tephra of the Soil–Pyroclastic Cover of Simushir Island (Central Kuril Islands)

The compositions of approximately 70 naturally quenched melt inclusions in olivine, clinopyroxene, orthopyroxene, and plagioclase phenocrysts from tephra of the soil–pyroclastic cover of Simushir Island (Central Kuril Islands) were studied. The concentrations of the major rock-forming components, H₂O, S, and Cl were analyzed in inclusions. The reconstructed melts contain 48.6–78.4 wt % SiO₂, 0.3–8.26 wt % MgO, and 0.12–1.72 wt % K₂O. The concentration of S and Cl in the melts changes regularly with increasing SiO₂ content: from 0.14 to ~0.02 wt % S and from ~0.05 to ~0.28 wt % Cl. The content of H2O in parental melts is 4.2–4.5 wt %.     

Relationship of polycyclic aromatic sulfur compounds and gold enrichment in the Kupferschiefer from Poland and Germany

1INTRODUCTION ORGANICALLY BOUNDSULFURCOMPOUNDSWEREPREVI OUSLYDETECTEDINTHEKUPFERSCHIEFER(P櫣TTMANNAND GO EL,1990;ROSPONDEKETAL.,1994).P櫣TTMANN ANDGO EL(1990)INVESTIGATEDTHEEXTRACTABLEORGANIC MATTERINTHEKUPFERSCHIEFERFROMTHENORTH SUDETIC SYNCLINEANDPROPOS…     

Thermohaline structure and circulation in the upper layers of the southern Bay of Bengal during BOBMEX-Pilot (October–November 1998)

Hydrographic data collected on board ORV Sagar Kanya in the southern Bay of Bengal during the BOBMEX-Pilot programme (October–November 1998) have been used to describe the thermohaline structure and circulation in the upper 200 m water column of the study region. The presence of seasonal Inter-Tropical Convergence Zone (ITCZ) over the study area, typically characterized with enhanced cloudiness and flanked by the respective east/northeast winds on its northern part and west/southwest winds on its southern part, has led to net surface heat loss of about 55 W/m². The sea surface dynamic topography relative to 500 db shows that the upper layer circulation is characterised by a cyclonic gyre encompassing the study area. The eastward flowing Indian Monsoon Current (IMC) between 5‡N and 7‡N in the south and its northward branching along 87‡E up to 13‡N appear to feed the cyclonic gyre. The Vessel-Mounted Acoustic Doppler Current Profiler (VM-ADCP) measured currents confirm the presence of the cyclonic gyre in the southern Bay of Bengal during the withdrawing phase of the southwest monsoon from the northern/central parts of the Bay of Bengal.     

Polymetamorphism of the Variscan Basement of the Moldanubian Black Forest （Germany） Documented in Zircon and Garnet Minerals from Gneisses

High-grade metamorphic Variscan basement is exposed in the Moldanubian zone of the Black Forest (BF), being the internal zone of the European Variscan belt. Zircon grains from K-rich felsic orthogneisses and an anatectic paragneiss in the Moldanubian Black Forest demonstrate a multi-stage crystallization at ～ 600 Ma, ～ 480 Ma, ～ 400 - 380 Ma, and ～350 Ma. The last three stages of crystallization probably represent metamorphic overprint during pre-Variscan and Variscan metamorphism.Using stepwise leaching procedures, garnet minerals from felsic orthogneisses as well as paragneisses in the Moldanubian Black Forest yielded Early Carboniferous Sm-Nd ages (～ 330- 340 Ma), which are consistent with the well-constrained Variscan HT metamorphic event,and Early Palaeozoic ( ～480 Ma) to Devonian ( ～400 - 370 Ma) Pb-Pb ages. The coincidence of growth time for zircon and garnet minerals at Early Palaeozoic is interpreted as dating a metamorphic event. These garnet data demonstrate that the Moldanubian BF basement underwent at least two metamorphic events during the Early Palaeozoic and Early Carboniferous.During the Variscan HT metamorphism, the Sm-Nd system of garnet was disturbed, but not the U-Pb system, implying the peak metamorphic temperature was lower than ～800℃.     

The first data on breithauptite in chromitite from the northern part of the Voykar–Synya ultramafic massif (Polar Urals)

Doklady Earth Sciences - This work presents the results of studying the mineral composition of chromite ores of the Khoila area. For the first time, nickel antimonide (breithauptite), including an...     

Major and trace element compositions (including REE) of mineral,thermal, mine and surface waters in SW Germany and implications for water–rock interaction

The near-surface water cycle in a geologically complex area comprises very different sources including meteoric, metamorphic and magmatic ones. Fluids from these sources can react with sedimentary, magmatic and/or metamorphic rocks at various depths. The current study reports a large number of major, minor and trace element analyses of meteoric, mineral, thermal and mine waters from a geologically well-known and variable area of about 200 × 150 km in SW Germany. The geology of this area comprises a Variscan granitic and gneissic basement overlain in parts by Triassic and Jurassic shales, sandstones and limestones. In both the basement and the sedimentary rocks, hydrothermal mineralization occurs (including Pb, Cu, As, Zn, U, Co and many others) which were mined in former times. Mineral waters, thermal waters and meteoric waters flowing through abandoned mines (mine waters) are distributed throughout the area, although the mine waters concentrate in and around the Schwarzwald.The present analyses show, that the major element composition of a particular water is determined by the type of surrounding rock (e.g., crystalline or sedimentary rocks) and the depth from which the water originates. For waters from crystalline rocks it is the origin of the water that determines whether the sample is Na–Cl dominant (deeper origin) or Ca–HCO₃ dominant (shallow origin). In contrast, compositions of waters from sedimentary rocks are determined by the availability of easily soluble minerals like calcite (Ca–HCO₃ dominant), halite (Na–Cl dominant) or gypsum (Ca–SO₄ dominant). Major element data alone cannot, therefore, be used to trace the origin of a water. However, the combination of major element composition with trace element data can provide further information with respect to flow paths and fluid–rock interaction processes. Accordingly, trace element analyses showed, that:

• −Ce anomalies can be used as an indicator for the origin of a water. Whereas surface waters have negative or strongly negative Ce anomalies, waters originating from greater depths show no or only weak negative Ce anomalies.
• −Eu anomalies can be used to differentiate between host rocks. Waters from gneisses display positive Eu anomalies, whereas waters from granites have negative ones. Waters from sedimentary rocks do not display any Eu anomalies.
• −Rb and Cs can also be indicators for the rock with which the fluid interacted: Rb and Cs correlate positively in most waters with Rb/Cs ratios of ∼2, which suggests that these waters are in equilibrium with the clay minerals in the rocks. Rb/Cs ratios >5 indicate reaction of a water with existing clay minerals, whereas Rb/Cs ratios <2 are probably related to host rock alteration and clay mineral formation.

The chemical compositions of carbonate precipitates from thermal waters indicate that rare earth elements (REEs), Rb and Cs concentrations in the minerals are controlled by the incorporation of clay particles that adsorb these elements.     

Kaolinization — a tool to unravel the formation and unroofing of the Pleystein pegmatite–aplite system (SE Germany)

The Hagendorf–Pleystein Pegmatite Province, SE Germany, is known for the largest feldspar–quartz pegmatite in Central Europe and renowned for its rare elements, e.g., Li, Nb, and Ta, giving rise to a spate of exotic minerals, mainly phosphates. Argillaceous rocks are scarce and eclipsed by the numerous mineralogical investigations on rare phosphates. These phosphate pegmatites are for the first time subjected to a clay mineralogical study, rendered possible by the newly discovered strongly kaolinized aplite near the Kreuzberg Quartz Pegmatite at Pleystein. The supergene kaolin akin to the residual kaolin deposit at Tirschenreuth, SE Germany, was analyzed for its major and minor elements by XRF and micro-chemically by EMPA. Mineralogical investigations involved XRD, IR spectroscopy, thermoanalytical studies, CEC analyses and SEM-EDX. Supergene kaolinization forms a repository for heavy minerals critical for the interpretation of the emplacement of the Late Paleozoic pegmatites as well as a matrix for pegmatite-related trace elements and thereby may be used as an ore guide during exploration of these rare metal pegmatites. The resultant kaolin is also the protagonist in the story of exhumation and destruction of a pegmatite by weathering and erosion. Irrespective of the strength of kaolinization, Nb–Ta–Ti heavy minerals can be identified in the regolith atop the host pegmatite or aplite and used for genetic interpretation of the primary mineralization and the origin of the felsic intrusive. Nb–Ta solid solution series (s.s.s.) have to be treated cautiously because of the disposition of Ta-enriched Nb–Ta oxide s.s.s. to undergo corrosion in their tantalite lamellae more easily than in their niobium-enriched zones. Kaolinization may alter the primary Nb/Ta ratio but not to the extent that Ta is released completely. The most strongly kaolinized new aplite is the youngest member of a series of felsic intrusive rocks in the Pleystein pegmatite–aplite system. The supergene kaolinization extending from the Miocene through the Pliocene can easily be correlated by “minero-stratigraphy” with the larger Tirschenreuth kaolin deposit. The four stages established in the area furnish evidence of gradual alkalinization of the meteoric pore fluids throughout the Neogene and the Quaternary. Youngest stages are found at Tirschenreuth, the oldest regolith stage is present at Pleystein.     

Geochronology and Geochemistry of Small Granitoid Intrusions in the Western Yana–Kolyma Gold Belt (Northeast Asia)

Doklady Earth Sciences - Data on the petrographic–geochemical and U–Th–Pb geochronological studies of granitoids of the Bukeschensky and Samyrsky massifs of small intrusions...     

The results of geochronological and isotope–geochemical study of zircons from tuff of the Sylvitsa Group (western slope of the Middle Urals): The origin of ash layers in Vendian rocks of the East European Platform

Doklady Earth Sciences - New LA-ICP-MS data on the U–Pb isotope age, Hf isotope characteristics, and concentrations of trace elements in zircons from volcanic tuff of the Upper Vendian...     

Mineralogy and genetic features of the Cu-As-Ni-Sb-Pb mineralization from the Mlakva polymetallic deposit (Serbia) — New occurrence of (Ni-Sb)-bearing Cu-arsenides

(Ni-Sb)-bearing Cu-arsenides are rare minerals within the Mlakva and Kram mining sectors (Boranja ore field) one of the less-known Serbian Cu deposits. (Ni-Sb)-bearing Cu-arsenides were collected from the Mlakva skarn-replacement Cu(Ag,Bi)-FeS polymetallic deposit. The identified phases include β-domeykite, Ni-bearing koutekite and (Ni-Sb)-bearing α-domeykite. (Ni-Sb)-bearing Cu-arsenides are associated with nickeline, arsenical breithauptite, chalcocite, native Ag, native Pb and litharge. Pyrrhotite, pyrite, chalcopyrite, cubanite, bismuthinite, molybdenite, sphalerite, galena, Pb(Cu)-Bi sulfosalts and native Bi, as well as minor magnetite, scheelite and powellite are associated with the sulfide paragenesis. The electron microprobe analyses of the (Ni-Sb)-bearing Cu-arsenides yielded the following average formulae: (Cu_2.73,Ni_0.17,Fe_0.03,Ag_0.01)_∑ 2.94(As_0.98,Sb_0.05,S_0.02)_∑ 1.06–β-domeykite (simplified formula (Cu_2.7,Ni_0.2)_∑ 2.9As_1.1); (Cu_3.40,Ni_1.40,Fe_0.11)_∑ 4.91(As_1.94,Sb_0.13,S_0.02)_∑ 2.08–Ni-bearing koutekite (simplified formula (Cu_3.4Ni_1.5)_∑ 4.9As_2.1); and Cu_1.97(Ni_0.98,Fe_0.03)_∑ 1.01(As_0.81,Sb_0.22)_∑ 1.03–(Ni–Sb)-bearing α-domeykite (simplified formula Cu₂NiAs). The Rietveld refinement yielded the following unit-cell parameters for β-domeykite and Ni–bearing koutekite: a = 7.1331(4); c = 7.3042(5) Å; V = 321.86(2) ų, and a = 5.922(4); b = 11.447(9); c = 5.480(4) Å; V = 371.48(5) ų, respectively. Ore geology, paragenetic assemblages and genesis of the Mlakva deposit are discussed in detail and the Cu-As-Ni-Sb-Pb mineralization has been compared with similar well-known global deposits.     

Overbank sediment profiles—evidence of early mining and smelting activities in the Harz mountains,Germany

Two overbank sediment cores to a depth of 5.6 m and 2.3 m respectively from the Uferbach catchment on the western foothills of the Harz mountains, Lower Saxony, Germany, revealed two anomalies of Pb, Zn, and Cu at 30–130 cm and at 204 cm, a PbZn-anomaly at 280 cm and a Pb-anomaly at 410 cm—evidence of four phases of mining and smelting activities in the catchment. The geochemical (major, minor, and trace elements) and mineralogical investigations (microscopy and microprobe analysis of matrix and slag particles) allowed for a broad interpretation of the element behavior (e.g., landuse) and the source region of the processed ore (hydrothermal deposits of the Upper Harz). A simple calculation model, based on¹⁴C-data, helped to estimate the time frame for the anomalies. The most likely interpretation requires an increase of the sedimentation rates over time (from 1 to 4 mm a⁻¹) and suggests medieval (1140–1345 A.D.), karolingian (82–890 AD), roman-germanic (425–500 A.D.) and early historic (825–625 B.C.) phases of smelting activities.     

Geological evolution of Mount Etna volcano (Italy) from earliest products until the first central volcanism (between 500 and 100 ka ago) inferred from geochronological and stratigraphic data

We present an updated geological evolution of Mount Etna volcano based on new ⁴⁰Ar/³⁹Ar age determinations and stratigraphic data integrating the previous K/Ar ages. Volcanism began at about 500 ka ago through submarine eruptions on the Gela–Catania Foredeep basin. About 300 ka ago fissure-type eruptions occurred on the ancient alluvial plain of the Simeto River forming a lava plateau. From about 220 ka ago the eruptive activity was localised mainly along the Ionian coast where fissure-type eruptions built a shield volcano. Between 129 and 126 ka ago volcanism shifted westward toward the central portion of the present volcano (Val Calanna–Moscarello area). Furthermore, scattered effusive eruptions on the southern periphery of Etna edifice occurred until about 121 ka ago. The stabilization of the plumbing system on the Valle del Bove area is marked by the building of two small polygenic edifices, Tarderia and Rocche volcanoes. Their eruptive activity was rather coeval ending 106 and 102 ka ago, respectively. During the investigated time-span volcanism in Etna region was controlled by a main E–W extensional tectonic related to the reactivation of Malta Escarpment fault system in eastern Sicily. Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

Ernst Weinschenk (1865–1921) a pioneer of microscopy and petrography in Munich (Southern Germany)

Ernst Weinschenk was an excellent teacher at the High School of Technology from 1897 till his death 1921, and at the university in Munich from 1900. His studies of the mineralogy of meteorites and the contact-metamorphic mineralization in the eastern and western Alps and southern Tyrol made him widely known early-on. He successfully determined many new minerals with the aid of the polarizing microscope and the use of mineral and thin rock sections. He attributed the genesis of the sulfidic ore deposit Silberberg at Bodenmais (northern Bavarian Forest) and the graphite deposits near Passau (Lower Bavaria) to the exhalative output of sulphur and carbon during the granite orogenesis (Weinschenk 1914).     

New results concerning the pedo- and chronostratigraphy of the loess–palaeosol sequence Attenfeld (Bavaria,Germany) derived from a multi-methodological approach

Loess–palaeosol sequences (LPS) represent important records of palaeoenvironmental dynamics throughout the Quaternary. During the Pleistocene's dry and cold phases, the Danube's riverbed was one of the major sources for loess sediments that built up LPS in southern Germany and southeastern Europe. Surprisingly, studies addressing Bavarian LPS along the Danube River often lack actuality. The Attenfeld site was one of them and is often cited as a typical LPS. Nevertheless, the site's previous interpretations are based on a few empirical data and field observations. Considering the site's closeness to the sediment's source area, the Alps, and the region's importance in Middle and Upper Palaeolithic migrational movements, those former renditions needed an evaluation. Therefore, we applied a multi-proxy approach (including analyses of grain-size distribution, element composition, and sediment colour attributes) combined with optically stimulated luminescence. Based on our findings, we conclude that the Attenfeld site's former interpretations might be too generalised. We identified units that were not mentioned by previous studies (e.g. Early Glacial dark greyish horizon). Field observations, sediment characteristics, and age estimates indicate sediment deposition of the dated units partly before MIS 4, which contrasts with previous interpretations. The results further demonstrate how sensitive LPS are to environmental settings and dynamics.     

Accumulative Landforms in Valleys with Gas-Hydrothermal Occurrences (from the Example of Watercourses of Some Volcanic Massifs in the Kuril—Kamchatka Region)

Doklady Earth Sciences - The sulfur isotope anomalies ∆33S and ∆36S known today in ancient rocks exhibit common geochemical patterns reflected in the existence of a correlation like...     

U-Pb zircon and Sm—Nd geochronology of mafic and ultramafic rocks from the central part of the Tauern Window (eastern Alps)

Geochronological and geochemical analyses were carried out in order to identify the pre-Variscan basement of the Tauern Window (eastern Alps). Maficultramafic rocks from the central part of the Tauern window have been studied by REE-analysis and U-Pb and Sm-Nd isotopic analyses on whole rock, zircons, garnets and sphene. U-Pb and Sm—Nd zircon dating define both magmatic Pan-African and Cambro-Ordovician events from 650 Ma to 486 Ma within the Alpine fold belt. This indicates a time span of 150 Ma for magmatic activities in the Tauern Window of the eastern Alps. The ages of 657 Ma (U-Pb zircon) and 644 (Sm—Nd zireon) obtained from an amphibolite are the oldest dates of the Eastern Alps; they may be related to the Pan-African orogeny, and imply an early cycle of magmatic intrusion before major activity started at around 500 Ma. Sm-Nd whole rock analyses of the Precambrian rocks do not define an isochron, reflecting heterogenities within the mantle source. The initial _Nd values (+1.2 to +4.7) are very low, implying an enrichment of the magma source. The second main phase of magmatic activity (539 486 Ma) is characterized by the emplacement of mafic/ultramafic rock sequences. As no ophiolitic relies are observed in these domains, the Early Paleozoic magmatism was likely associated with extensional tectonics. Obtained ages of 301±3 and 314+4/-3 Ma point to a Variscan metamorphism. The first combined U-Pb zircon/Sm—Nd zircon data for an amphibolite from the Basal Amphibolite Formation (BAF) favoured the Sm-Nd zircon isochron age as a magmatic age, whereas the low initial _Nd value point to an enriched magma source as well as to heterogenities within the magma source. The obtained ages suggest that parts of the pre-Variscan basement within the Alpine fold belt were formed during the Pan-Africa cycle. The detection of Pre-Variscan ages within the Alpine basement must reffect a complex history involving significant pre-Variscan activity.     

Preservation of diagenetic products of β-carotene in sedimentary rocks from the Lopare Basin (Bosnia and Herzegovina)

Sedimentary rocks from the saline formation of the Lopare Basin were investigated. Sediments contain a moderate amount of immature to marginally mature algal organic matter deposited under slightly reducing to anoxic and slightly saline to hypersaline conditions. Almost all of the samples contain β-carotane in a relatively high quantity, and in some, it represents the most abundant compound in the total distribution of hydrocarbons. The objective of the study was to determine the conditions that are favourable to precursors of β-carotene and/or the preservation of the carotenoid hydrocarbon skeleton. Moreover, the dominant transformation pathways of β-carotene under different redox and salinity conditions, which lead to the formation of aromatic carotenoids were defined.