A northwest North American training set: distribution of freshwater midges in relation to air temperature and lake depth     

Erin M. Barley  Ian R. Walker  Joshua Kurek  Les C. Cwynar  Rolf W. Mathewes  Konrad Gajewski  Bruce P. Finney 《Journal of Paleolimnology》2006,36(3):295-314

Freshwater midges, consisting of Chironomidae, Chaoboridae and Ceratopogonidae, were assessed as a biological proxy for palaeoclimate in eastern Beringia. The northwest North American training set consists of midge assemblages and data for 17 environmental variables collected from 145 lakes in Alaska, British Columbia, Yukon, Northwest Territories, and the Canadian Arctic Islands. Canonical correspondence analyses (CCA) revealed that mean July air temperature, lake depth, arctic tundra vegetation, alpine tundra vegetation, pH, dissolved organic carbon, lichen woodland vegetation and surface area contributed significantly to explaining midge distribution. Weighted averaging partial least squares (WA-PLS) was used to develop midge inference models for mean July air temperature (r _boot² = 0.818, RMSEP = 1.46°C), and transformed depth (ln (x+1); r _boot² = 0.38, and RMSEP = 0.58).  相似文献   

Metasomatism of sub-arc mantle peridotites below southernmost South America: reduction of<Emphasis Type="Italic"> f</Emphasis>O<Subscript>2</Subscript> by slab-melt     

Jian Wang  Kéiko H. Hattori  Rolf Kilian  Charles R. Stern 《Contributions to Mineralogy and Petrology》2007,153(5):607-624

Quaternary basalts in the Cerro del Fraile area contain two types of mantle xenoliths; coarse-grained (2–5 mm) C-type spinel harzburgites and lherzolites, and fine-grained (0.5–2 mm) intensely metasomatized F-type spinel lherzolites. C-type xenoliths have high Mg in olivine (Fo = 90–91) and a range in Cr# [Cr/ (Cr + Al) = 0.17–0.34] in spinel. Two C-type samples contain websterite veinlets and solidified patches of melt that is now composed of minute quenched grains of plagioclase + Cr-spinel + clinopyroxene + olivine. These patches of quenched melts are formed by decompression melting of pargasitic amphibole. High Ti contents and common occurrence of relic Cr-spinel in the quenched melts indicate that the amphibole is formed from spinel by interaction with the Ti-rich parental magma of the websterite veinlets. The fO₂ values of these two C-type xenoliths range from ΔFMQ −0.2 to −0.4, which is consistent with their metasomatism by an asthenospheric mantle-derived melt. The rest of the C-type samples are free of “melt,” but show cryptic metasomatism by slab-derived aqueous fluids, which produced high concentrations of fluid-mobile elements in clinopyroxenes, and higher fO₂ ranging from ΔFMQ +0.1 to +0.3. F-type lherzolites are intensely metasomatized to form spinel with low Cr# (∼0.13) and silicate minerals with low MgO, olivine (Fo = ∼84), orthpyroxene [Mg# = Mg/(Mg + ΣFe) = ∼0.86] and clinopyroxene (Mg# = ∼0.88). Patches of “melt” are common in all F-type samples and their compositions are similar to pargasitic amphibole with low TiO₂ (<0.56 wt%), Cr₂O₃ (<0.55 wt%) and MgO (<16.3 wt%). Low Mg# values of silicate minerals, including the amphibole, suggest that the metasomatic agent is most likely a slab melt. This is supported by high ratios of Sr/Y and light rare earth elements (REE)/heavy REE in clinopyroxenes. F-type xenoliths show relatively low fO₂ (ΔFMQ −0.9 to −1.1) compared to C-type xenoliths and this is explained by the fusion of organic-rich sediments overlying the slab during the slab melt. Trench-fill sediments in the area are high in organic matter. The fusion of such wet sediments likely produced CH₄-rich fluids and reduced melts that mixed with the slab melt. High U and Th in bulk rocks and clinopyroxene in F-type xenoliths support the proposed interpretation.  相似文献   

Dating multiply overprinted Sn-mineralized granites—examples from the Erzgebirge,Germany     

Rolf L. Romer  Rainer Thomas  Holly J. Stein  Dieter Rhede 《Mineralium Deposita》2007,42(4):337-359

Granites and primary tin mineralization in the Erzgebirge were dated using (1) conventional U–Pb dating of uraninite inclusions in mica, (2) Rb–Sr dating of inclusions in quartz that represent highly evolved melts, (3) Re–Os dating of magmatic–hydrothermal molybdenite, and (4) chemical Th–U–Pb dating of uraninite. Conventional isotope dilution and thermal ion mass spectrometry and chemical Th–U–Pb dating of uraninite in granites from the Ehrenfriedersdorf mining district provide ages of 323.9 ± 3.5 Ma (2σ; Greifenstein granite) and 320.6 ± 1.9 and 319.7 ± 3.4 Ma (2σ, both Sauberg mine), in agreement with U–Pb apatite ages of 323.9 ± 2.9 and 317.3 ± 1.6 Ms (2σ, both Sauberg mine). Rb–Sr analysis of melt inclusions from Zinnwald gives highly radiogenic Sr isotopic compositions that, with an assumed initial Sr isotopic composition, permit calculation of precise ages from single inclusions. The scatter of the data indicates that some quartz-hosted melt inclusions have been affected by partial loss of fluid exsolved from the melt inclusion. Re–Os dating of two molybdenite samples from Altenberg provides ages of 323.9 ± 2.5 and 317.9 ± 2.4 Ma (2σ). Together with age data from the literature, our new ages demonstrate that primary tin mineralization and the emplacement of the large Sn-specialized granites in the Erzgebirge fall in a narrow range between 318 and 323 Ma. Primary Sn mineralization occurred within a short interval during post-collisional collapse of the Variscan orogen and was essentially synchronous over the entire Erzgebirge. In contrast to earlier claims, no systematic age difference between granites of the eastern and western Erzgebirge was established. Furthermore, our data do not support a large age range for Late-Variscan granites of the Erzgebirge (330–290 Ma), as has been previously suggested.  相似文献   

Indirect determination of the heat budget of tidal flats     

Reiner Onken  Ulrich CalliesBernd Vaessen  Rolf Riethmüller 《Continental Shelf Research》2007

A method is presented to calculate indirectly the heat budget of a tidal flat area from downstream observations of temperature and horizontal velocity in a tidal channel. It is only necessary to establish a relationship between the velocity and the volume flux. Then the heat budget of the upstream region is determined by integrating the heat flux over one tide. The proposed method is applied to long-term measurements obtained in 2004 at two sites in a tidal channel in the Hörnum Basin, German Wadden Sea. At the site located farther downstream in the channel, the upstream catchment area is diagnosed to export heat (heat gain in the interior) from March to August, while import is diagnosed for the same period of time at the other upstream site. From September to November the situation is reversed. An analytical estimate suggests that the sign of the budget is controlled by the tidal prism and the length of the dry-falling period of the flats in the respective upstream region. In addition, a simple model is developed which can be used to determine the integral bottom heat flux of the tidal flats.  相似文献   

Book Reviews: Personal Care Compounds in the Environment. Edited by K. Bester     

Rolf‐Alexander Düring 《洁净——土壤、空气、水》2007,35(3):219-219

  相似文献   

Temperature-dependent isotopic fractionation of lithium between clinopyroxene and high-pressure hydrous fluids   总被引：2，自引：1，他引：2  

Bernd Wunder  Anette Meixner  Rolf L. Romer  Wilhelm Heinrich 《Contributions to Mineralogy and Petrology》2006,151(1):112-120

The fractionation of lithium isotopes between synthetic spodumene as representative of Li-bearing clinopyroxene and Cl- and OH-bearing aqueous fluids was experimentally determined between 500 and 900°C at 2.0 GPa. In all the experiments, ⁷Li was preferentially partitioned into the fluid. The fractionation is temperature dependent and approximated by the equation Δ⁷Li_{(clinopyroxene–fluid)}=−4.61×(1,000/T [K]) + 2.48; R ²=0.86. Significant Li isotopic fractionation of about 1.0‰ exists even at high temperatures of 900°C. Using neutral and weakly basic fluids revealed that the amount of fractionation is not different. The Li isotopic fractionation between altered basalt and hot spring water (350°C) in natural samples is in good agreement with our experimentally determined fractionation curve. The data confirm earlier speculations drawn from the Li isotopic record of dehydrated metamorphic rocks that fluids expelled from a dehydrating slab carry heavier Li into the mantle wedge, and that a light Li component is introduced into the deeper mantle. Li and Li isotopes are redistributed among wedge minerals as fluids travel across the wedge into hotter regions of arc magma production. This modifies the Li isotopic characteristics of slab-derived fluids erasing their source memory, and explains the absence of cross-arc variations of Li isotopes in arc basalts.  相似文献   

Nd, Pb, and Sr isotope composition of juvenile magmatism in the Mesozoic large magmatic province of northern Chile (18–27°S): indications for a uniform subarc mantle     

Friedrich Lucassen  Wolfgang Kramer  Viola Bartsch  Hans-Gerhard Wilke  Gerhard Franz  Rolf L. Romer  Peter Dulski 《Contributions to Mineralogy and Petrology》2006,152(5):571-589

The Jurassic to Early Cretaceous magmatic arc of the Andes in northern Chile was a site of major additions of juvenile magmas from the subarc mantle to the continental crust. The combined effect of extension and a near stationary position of the Jurassic to lower Cretaceous arc favoured the emplacement and preservation of juvenile magmatic rocks on a large vertical and horizontal scale. Chemical and Sr, Nd, and Pb isotopic compositions of mainly mafic to intermediate volcanic and intrusive rock units coherently indicate the generation of the magmas in a subduction regime and the dominance of a depleted subarc mantle source over contributions of the ambient Palaeozoic crust. The isotopic composition of the Jurassic (²⁰⁶Pb/²⁰⁴Pb: ∼ 18.2; ²⁰⁷Pb/²⁰⁴Pb: ∼ 15.55; ¹⁴³Nd/¹⁴⁴Nd: ∼ 0.51277; ⁸⁷Sr/⁸⁶Sr: ∼ 0.703–0.704) and Present (²⁰⁶Pb/²⁰⁴Pb: ∼ 18.5; ²⁰⁷Pb/²⁰⁴Pb: ∼ 15.57; 143Nd/144Nd: ∼ 0.51288; ⁸⁷Sr/⁸⁶Sr: ∼ 0.703–0.704) depleted subarc mantle beneath the Central and Southern Andes (18°–40°S) was likely uniform over the entire region. Small differences of isotope ratios between Jurassic and Cenozoic to Recent of subarc mantle-derived could be explained by radiogenic growth in a still uniform mantle source.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .  相似文献   

Evolution of orbitolinid foraminifers and anoxic events: A comment on an article by J. Guex, Eclogae geol. Helv. 94 (2001) 321–328     

Antonietta Cherchi  Rolf Schroeder 《Eclogae Geologicae Helvetiae》2004,97(3):441-444

  相似文献   

Erdbeben als Ausdruck spontaner Tektonik     

Dr. Rolf Schick 《International Journal of Earth Sciences》1972,61(3):896-914

Zusammenfassung Erdbeben sind nach nichtlinearen Gesetzen ablaufende Prozesse im festen Teil des Erdkörpers. Ihre Beschreibung erfolgt aus Gründen der Zweckmäßigkeit durch eine Reihe von Zahlen, die Herdparameter genannt werden. Die mit der Tektonik eines Gebietes enger zusammenhängenden Herdparameter werden in der vorliegenden Arbeit diskutiert.

---

Earthquakes are nonlinear processes within the solid part of the earth. It is reasonable to describe an earthquake with a series of numbers, which are called source parameters. Those source parameters which show a closer relation to the tectonic structure of an area are discussed in this paper.

---

Résumé Les tremblements de terre sont des processus qui se déroulent dans la partie solide du globe terrestre suivant des lois non linéaires. Il est raisonnable de décrire un séisme par une série de nombres qu'on appelle les paramètres du foyer qui montrent une relation plus étroite avec la structure tectonique.

---

— , . , . , .

---

---

Der Deutschen Forschungsgemeinschaft, Bad Godesberg, bin ich für die Förderung der Arbeit zu Dank verpflichtet (Az. Schi 120/1, Kennwort: Geodynamik des mediterranen Raumes).  相似文献   

Rumpfflächen und Lagerstättenbildung über Itabiriten auf den präkambrischen Schilden von Südamerika und Afrika     

Dr. Jürgen Eichler  Prof. Dr. Rolf Thienhaus 《International Journal of Earth Sciences》1968,58(1):152-165

Zusammenfassung Verwitterungsreicherze über Itabiriten der präkambrischen Schilde von Südamerika und Afrika verdanken ihre Entstehung lateritischen Verwitterungsvorgängen bei günstigen Drainageverhältnissen. Sie sind stets an Erosionsrelikte hochgelegener alter Verebnungsflächen gebunden. Für die Reicherzbildung ist neben der sedimentären und metamorphen Fazies und der tektonischen Position des itabiritischen Muttergesteins vor allem die geomorphologische Entwicklung der präkambrischen Schildgebiete, mit seit Beginn der Unterkreide verstärkter epirogen bedingter Hebung und Einebnung, von Bedeutung. Die langfristige Erhaltung der alten Reliefs und der an sie gebundenen Lagerstätten wird im Zusammenspiel von Hebung und Abtragung maßgeblich durch die Bildung von chemisch und mechanisch resistenten Verwitterungskappen bestimmt. Gleichartige Beziehungen zwischen alten Rumpfflächen und Lagerstättenbildung gelten auch für Reicherzvorkommen in Indien und Westaustralien.

---

The paper deals with the genesis of supergene high-grade iron ores formed by lateritic weathering of itabirites. Remarkably, the iron ores are always related to remnants of high lying old land surfaces of Cretaceous to early Tertiary age. Hence, besides other important conditions such as the sedimentary and metamorphic facies of the itabiritic parent rock, the physiographic development of the Precambrian shield areas appears to be an essential factor of control for the ore-forming process. Special reference is paid to some iron ore deposits in South America and the western part of Africa which in many details resemble to similar occurrances in India and Western Australia.

---

Résumé Les gisements de fer sur les itabirites des massifs précambriennes de l'Amérique du Sud et de l'Afrique doivent leur genèse aux procédés de décomposition latéritique. Ils sont toujours liés à crêtes ferriféres qui portent restes des pénéplaines anciennes et dépassent d'environ plusieurs centaines de métres les pénéplaines récentes.La conservation à long terme des reliefs anciens et des gisements de fer dépend de la formation d'une couverture résistant de canga. Le développement des chapeaux de fer est favorisé par le drainage profond des pénéplaines élévées, que rend possible la dissolution et le transport de la silice. Rapports de même nature entre la géomorphologie et la genèse de ce type des gisements de fer aussi existent à l'Inde et dans l'ouest de l'Australie.

---

Resumo A formação de minério rico supergênico sobre itabiritos por intemperismo laterítico depende, além de outros fatores como facies sedimentar e metamórphico dos itabiritos, essencialmente da posição fisiográfica da região. Assim, encontra-se as jazidas profundas de minério rico supergênico sempre em niveis topográficos mais elevados, que representam restos de peneplanos post-cretáceos. A conservação prolongada do relevo, pressuposto para o desenvolvimento do perfil laterítico maduro, é decisivamente efectuada por formação d'uma capa resistente de canga na superficie.O trabalho trata umas ocorrencias na America do Sul e na África e aponta a condiç~oes semelhantes na India e Austrália, mostrando a grande importancia das condições geomorfológicas para a formação deste tipo de minério de ferro.

---

. . .. . , . , , . .

---

---

Die in dieser Abhandlung aus Minas Gerais mitgeteilten Ergebnisse sind Teil einer größeren Arbeit über die Genese itabiritischer Reicherze. Die Untersuchungen wurden durch eine Beihilfe seitens der Deutschen Forschungsgemeinschaft ermöglicht, wofür dieser sehr gedankt sei.  相似文献