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Snowball Earth is dead! Long live Snowball Earth!

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Episodes 2006年第4期29卷 287-288页

作者： Graham A. Shields institut für geologie und Palaeontologie Westfaeilische-Wilhelms Universitaet Correnstr. 24 48149 Münster Germany

Ticino in southern Switzerland played host this summer to a most extraordinary meeting of minds. About eighty scientists from all over the world came together in the exquisite setting of Monte Verita to discuss possib... 详细信息

关键词：瑞士雪球气候变化二氧化碳全球变暖环境气候问题

remanence acquisition and its alteration on sediments

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Chinese Science Bulletin 1998年第17期43卷 1421-1434页

作者： ErwinAppel Nanjing institute of Geography & Limnology Chinese Academy of Sciences Nanjing China institut für geologie und Palaeotonologie Universitat Tübingen Tübingen Germany

Previous palaeomagnetic work shows that the mechanism of remanence acquisition on sediments is very complicated. Different magnetizing processes under different conditions may produce some anomalous magnetic signals which have nothing to do with the changes of the geomagnetic field and are difficult to explain.;The depositional remanent magnetization (DrM) may produce an inclination error and a bedding error, while postdepositional remanent magnetization (PDrM) may result in a time delay between the magnetic and sedimentary ages. When there are some different magnetic phases with different lock-in depths in the sediments, it is difficult to judge the depth of the reversal or excursion, or even the artificial magnetic signal may be produced. Even if there is only one magnetic phase in the sediment, the recorded magnetic signals may also be different if the lock-in depth is changed comparative to the lasting period of one reversal or excursion. Demagnetization may also change the primary magnetic records and the changes of water content may result in the displacement of magnetic boundary. The so-called "unstable core", representing subtle changes in mineralogy into and out of a self-reversal region or a viscous magnetization region, gives a complicated palaeomagnetic record with many apparent changes in the palaeomagnetic direction. Moreover, some physical disturbances, such as biodisturbance, deformation, drilling processes and drying effects, may result in the remanence alteration. Some palaeomagnetic investigations demonstrate that good magnetic signals are invariably achieved on homogenous mud or clay sediments, but the worse signals on inhomogeneous profiles, especially on sandy layers.

关键词： remanence acquisition alteration sediment.

Experimental constraints on the genesis of Jadeite quartzite from Shuanghe,Dabie Mountain ultra-high pressure metamorphic terrane

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Science China Earth Sciences 2014年第1期57卷 104-116页

作者： ZHANG Yanfei WU Yao WANG Chao JIN ZhenMin Hans-Peter SCHErTL State Key Laboratory of Geological Processes and Mineral resources China University of Geosciences institut für geologie Mineralogie und Geophysik Ruhr-Universit t Bochum 44780 Bochum Germany

Jadeite quartzite,essentially a two-phase rock made up of jadeite and quartz,is one of the most important UHP lithologies occurring in the Dabie Mountain ultrahigh pressure metamorphic belt and forms layers in biotite-plagioclase *** pressurehigh temperature studies on natural albite from the country rock gneiss were undertaken to reveal the—in parts—complex mineralogical changes that occur in the jadeite quartzite during prograde *** were conducted at 800–1200°C,in the pressure range of 2.0–3.5 *** of the most intriguing results shows that the low pressure boundary of the jadeite+coesite stability field is located between about 3.2 GPa at 1000°C and 3.4 GPa at 1200°C,thus about(0.2–0.3)±0.1GPa higher than the quartz-coesite transition curve,given the uncertainty in the present *** amounts of sodium and aluminum entering the structure of quartz and the intimate intergrowth texture of the run products may contribute to the observed pressure *** petrological and mineralogical studies on the run products and the natural rocks yield the following prograde reaction sequence to have occurred:The protolith of the jadeite-quartzite from Dabie Mountain is an albitized siltstone/greywacke characterized by an albite+quartz *** prograde metamorphism albite breaks down to form jadeite+quartz and thus at this stage two types of quartz can be distinguished whereas type-I-quartz already existed in the protolith,type-II-quartz represents a newly formed reaction product of *** further P-T-increase the pure type-I-quartz was transformed to coesite,whereas type-II-quartz(together with jadeite)was still present as a stable phase because of its impurities of Na and *** a later stage during further subduction,type-II-quartz also decomposes to form *** studies represent an important puzzlement for a better understanding of the evolution of jadeite-quartzite from the Dabie Mountain during continental cru

关键词：超高压变质地体硬玉石英岩大别山翡翠实验黑云斜长片麻岩双河成因

recycling process and proto-kimberlite melt metasomatism in the lithosphere-asthenosphere boundary beneath the Amazonian Craton recorded by garnet xenocrysts and mantle xenoliths from the Carolina kimberlite

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Geoscience frontiers 2022年第5期13卷 89-105页

作者： fernanda Gervasoni Tiago Jalowitzki Marcelo Peres rocha ricardo Kalikowski Weska Eduardo Novais-rodrigues rodrigo Antonio de freitas rodrigues Yannick Bussweiler Elisa Soares rocha Barbosa Jasper Berndt Elton Luiz Dantas Valmir da Silva Souza Stephan Klemme Centro de Engenharias Universidade Federal de Pelotas(UFPel)PelotasBrazil Programa de Pós-graduação em Geociências Universidade Federal do Rio Grande do SulPorto AlegreBrazil Programa de Pós-graduação em Geologia Instituto de GeociênciasUniversidade de Brasília(UnB)BrasíliaBrazil faculdade de Geociências Universidade Federal do Mato Grosso(UFMT)CuiabáBrazil institut für geologie und Mineralogie Universität zu KölnGermany faculdade de Ciências e Tecnologia Universidade Federal de Goiás(UFG)Aparecida de GoiâniaBrazil institut für Mineralogie Universität MünsterMünsterGermany

Here we present new data on the major and trace element compositions of silicate and oxide minerals from mantle xenoliths brought to the surface by the Carolina kimberlite,Pimenta Bueno Kimberlitic field,which is located on the southwestern border of the Amazonian *** also present Sr-Nd isotopic data of garnet xenocrysts and whole-rocks from the Carolina *** xenoliths are mainly clinopyroxenites and *** of the clinopyroxenites were classified as GPP–PP–PKP(garnet-phlogopite peridotite,phlogopite-peridotite,phlogopite-K-richterite peridotite)suites,and two clinopyroxenites(eclogites)and two garnetites are relicts of an ancient subducted *** and pressure estimates yield 855–1102℃ and 3.6–7.0 GPa,*** are enriched in light rare earth elements(LrEE)(La_(N)/Yb_(N)=5–62;Ce_(N)/Sm_(N)=1–3;where N=primitive mantle normalized values),they have high Ca/Al ratios(10–410),low to medium Ti/Eu ratios(742–2840),and low Zr/Hf ratios(13–26),which suggest they were formed by metasomatic reactions with CO_(2)-rich silicate *** with high TiO_(2)(>2.0 wt.%),Al_(2)O_(3)(>12.0 wt.%),and feOt(5.0–13.0 wt.%)resemble those found in the groundmass of kimberlites,lamproites and ***,phlogopite with low TiO_(2)(r Al_(2)O_(3)(re similar to those present in GPP-PP-PKP,and in MArID(mica-amphibole-rutile-ilmenite-diopside)and PIC(phlogopite-ilmenite-clinopyorxene)*** GPP-PP-PKP suite of xenoliths,together with the clinopyroxene and phlogopite major and trace element signatures suggests that an intense proto-kimberlite melt metasomatism occurred in the deep cratonic lithosphere beneath the Amazonian *** Sr-Nd isotopic ratios of pyrope xenocrysts(G3,G9 and G11)from the Carolina kimberlite are characterized by high ^(143)Nd/^(144)Nd(0.51287–0.51371)and eNd(+4.55 to+20.85)accompanied with enriched ^(87)Sr/^(86)Sr(0.70405–0.71098).These results suggest intera

关键词： Carolina kimberlite K-rich mantle xenoliths Ancient subducted slab Proto-kimberlite melt metasomatism

The significance of U-Pb zircon ages in zoned plutons:the case of the flamenco pluton, Coastal range batholith, northern Chile

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Geoscience frontiers 2019年第3期10卷 1073-1099页

作者： Natalia rodríguez Juan Díaz-Alvarado Carlos fernández Paulina fuentes Christoph Breitkreuz Colombo Celso Gaeta Tassinari Departamento de Geología Universidad de Atacama Departamento de Ciencias de la Tierra Universidad de Huelva institut für geologie TU Bergakademie Freiberg High resolution Geochronological Laboratory University of S?o Paulo

Compositionally zoned plutons, both layered and concentrically arranged, provide granitic exposures where the mechanisms and timing of the magmatic emplacement processes can be studied. The importance of in-situ geochemical differentiation and the magma replenishment rates are revealed by geochemistry and field relations, together with the increasingly accurate U-Pb geochronology, which has promoted the knowledge about the pluton incremental assembly *** flamenco pluton, located in the Coastal range of northern Chile, is part of the Upper Triassic to Early Cretaceous Andean intrusives formed in the western active margin of South America, and present a normal zoned structure with mafic magmatic facies(mostly gabbros and Qtz-diorites) close to the contacts with the host metasediments, and tonalites, granodiorites and granites in the inner areas. A combined study of the field relations, geochemistry and zircon geochronology of the magmatic facies was applied to determine the emplacement sequence of the flamenco pluton, revealing three distinguishable domains separated by metasedimentary septa. The SW area is constituted by mostly homogeneous leucocratic granodiorites that yielded an age of 213 Ma as the best estimation for their emplacement age. Distinctive geochemical characteristics, such as the absence of an Eu anomaly, the depletion in HrEE, or the highest Sr, Sr/Y and Ce/Yb values among the granodioritic facies of the pluton,involve lower T and/or higher P conditions at the magmatic source according to experimental *** conditions were established during an early stage of the Andean magmatic arc building that is firstly defined here as Upper Triassic. The NW and E domains of the pluton were sequentially emplaced between 194 Ma and 186 Ma and both the field relations and the detailed geochronological results suggest that the mafic facies intruded latter in the emplacement sequence. To the NW, Qtz-dioritic and gabbroic externally emplaced pulses ga

关键词： Zircon U-Pb geochronology Zoned plutons Andean magmatic arc Sequential emplacement Individual and statistical zircon ages

Thermal evolution of an ancient subduction interface revealed by Lue Hf garnet geochronology, Halilba■? Complex(Anatolia)

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Geoscience frontiers 2019年第1期10卷 127-148页

作者： Amaury Pourteau Erik E.Scherer Simon Schorn rebecca Bast Alexander Schmidt Lisa Ebert institut für Erd- und Umweltwissenschaften Universit?t Potsdam Earth Dynamics research Group ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS) The Institute for Geoscience Research (TIGeR) School of Earth and Planetary Sciences Curtin University Münster Isotope research Centre Institut für Mineralogie Westf?lische Wilhelms-Universit?t Münster Department of Geological Sciences University of Cape Town institut für geologie und Mineralogie Universit?t zu K?ln

The thermal structure of subduction zones exerts a major influence on deep-seated mechanical and chemical processes controlling arc magmatism, seismicity, and global element cycles. Accretionary complexes exposed inland may comprise tectonic blocks with contrasting pressureetemperature(Pe T)histories, making it possible to investigate the dynamics and thermal evolution of former subduction interfaces. With this aim, we present new Lue Hf geochronological results for mafic rocks of the Halilbag?Complex(Anatolia) that evolved along different thermal gradients. Samples include a lawsoniteeepidote blueschist, a lawsoniteeepidote eclogite, and an epidote eclogite(all with counter-clockwise Pe T paths),a prograde lawsonite blueschist with a "hairpin"-type Pe T path, and a garnet amphibolite from the overlying sub-ophiolitic metamorphic sole. Equilibrium phase diagrams suggest that the garnet amphibolite formed at w0.6 -0.7 GPa and 800 -850℃, whereas the prograde lawsonite blueschist records burial from 2.1 GPa and 420℃ to 2.6 GPa and 520℃. Well-defined Lue Hf isochrons were obtained for the epidote eclogite(92.38 ± 0.22 Ma) and the lawsoniteeepidote blueschist(90.19 ± 0.54 Ma),suggesting rapid garnet growth. The lawsoniteeepidote eclogite(87.30 ± 0.39 Ma) and the prograde lawsonite blueschist(ca. 86 Ma) are younger, whereas the garnet amphibolite(104.5 ± 3.5 Ma) is *** data reveal a consistent trend of progressively decreasing geothermal gradient from granulite-facies conditions at ~104 Ma to the epidote-eclogite facies around 92 Ma, and the lawsonite blueschist-facies between 90 Ma and 86 Ma. Three Lue Hf garnet dates(between 92 Ma and 87 Ma) weighted toward the growth of post-peak rims(as indicated by Lu distribution in garnet) suggest that the HP/LT rocks were exhumed continuously and not episodically. We infer that HP/LT metamorphic rocks within the Halilbag?Complex were subjected to continuous return flow, with "warm" rocks being exhumed during the tectonic bur

关键词： Subduction Lu/Hf dating of garnet Metamorphic sole Eclogite Blueschist Lawsonite

Analysis of the Influence of Wind Turbine Noise on Seismic recordings at Two Wind Parks in Germany

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Journal of Geoscience and Environment Protection 2017年第5期5卷 76-91页

作者： Hortencia flores Estrella Michael Korn Kilian Alberts institut für Geophysik und geologie Universitat LeipzigLeipzigGermany

We recorded continuous seismic noise close and around two wind parks with different geological site conditions in order to investigate the effects of wind turbines on seismic signals in the frequency interval between 1 and 10 Hz. In wind park fraureuth-Beiersdorf (5 turbines, 11 km south from Zwickau, Saxony), we used small seismic networks, with 3 to 5 stations for 1 - 2 weeks. In Heinde (2 turbines, close to Hildesheim, Lower Saxony), we recorded 1 week with one station around 1 km away from the wind turbines and some additional stations for several hours only. With the spectrogram analysis of the data, we clearly identify the diurnal variation on the spectral amplitude separately from the noise generated by the turbines. The turbine noise appears at certain frequency bands around 2.2, 2.7, 3.3, 4.5, 5.2 and 6.6 Hz. A linear relation between the spectral amplitudes of these frequency bands and the wind velocity or rotation velocity of the turbines is clearly identified. The seismic signals produced by the operation of the wind turbines are not peaks at single frequencies, but look more like frequency bands with increased noise amplitudes. They could be identified up to at least 10 km in the case of fraureuth-Beiersdorf. These bands depend on numerous parameters, i.e. wind turbine height, weight and construction, number of turbines, geology, etc. In both wind parks we also recorded along profiles with increasing distances from the wind turbines. With the analysis of these data, we propose an amplitude attenuation model for the wind park fraureuth-Beiersdorf to a distance of 9 km, and for Heinde to a distance of 4 km. The attenuation models for both wind parks are quite different, depending probably on the local geology and topography.

关键词： Wind Turbine Seismic Noise Seismic records

Environmental magnetic studies of lacustrine sediments

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Chinese Science Bulletin 2002年第7期47卷 613-616页

作者： HU Shouyun, DENG Chenglong, E. Appel & K. L. VerosubNanjing institute of Geography and Limnology, Nanjing 210008, China institute of Geology and Geophysics, Beijing 100101, China institut fur Geologic, Universitat Tubingen, 72076 Tubingen, Germany Departm Nanjing institute of Geography and Limnology Nanjing China institute of Geology and Geophysics Beijing China institut für geologie Universität Tübingen Tübingen Germany Department of Geology University of California Davis USA

In recent decades, environmental magnetism has become an important method for studying past global climatic and environmental changes. for an environmental magnetic study, it is important to understand the magnetic properties of various magnetic minerals in lacustrine sediments and the processes involved in the formation, transport, and preservation of these magnetic minerals. The magnetic response of lacustrine sediments to climatic change may vary widely from lake to lake. To reconstruct the processes contributing to paleoclimatic and paleoenvironmental change, it is, therefore, necessary to derive a complete understanding of the potential origin of the magnetic signal observed.

关键词： rock magnetism paleoclimate paleoenvironment lacus-trine sediments.

remote Gully Erosion Mapping Using ASTEr Data and Geomorphologic Analysis in the Main Ethiopian rift

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Geo-Spatial Information Science 2011年第4期14卷 246-254页

作者： Moncef Bouaziz Arief Wijaya richard Gloaguen remote Sensing Group Institut für GeologieTU Bergakademie Freiberg Laboratoire 3E(AD‐10‐02) Ecole National d'Ingénieurs de Sfax faculty of Agricultural Technology Gadjah Mada University

The Main Ethiopian rift(MEr)is an area of extreme topography underlain by post-Miocene volcanic rocks,Jurassic limestone and a Precambrian basement.A prime concern is the rapid expansion of wide gullies that are impinging on agricultural *** investigate the potential contribution of Advanced Space-borne Thermal Emission and reflection radiometer(ASTEr)data and geomorphologic parameters to discern patterns and features of gully erosion in the *** Likelihood Classifica-tion(MLC),Support Vector Machine(SVM),and Minimum Distance(MD)classifiers are used to extract different gully shapes and *** spatial textures based on Grey Level Co-occurrence Matrices(GLCMs)are then ***,the same classifiers are applied to the ASTEr data combined with the spatial texture *** used geomorphologic parameters ex-tracted from SrTM and ASTEr DEMs to describe the geomorphologic setting and the gullies' *** classifications show accuracies varying between 67% and 89%.Maps derived from this quantitative analysis allow the monitoring and mapping of land degradation as a direct result of *** study reveals the utility of combining ASTEr data and spatial textural infor-mation in discerning areas affected by gully erosion.

关键词： ASTEr数据沟壑侵蚀埃塞俄比亚地貌分析裂谷映射最大似然分类空间结构信息