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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 occur- ring in the Dabie Mountain ultrahigh pressure metamorphic belt and forms layers in biotite-plagioclase gneiss. High pressure- high 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 metamorphism. Experiments were conducted at 800- 1200~C, in the pressure range of 2.0-3.5 GPa. One 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）_＋0.1 GPa higher than the quartz-coesite transition curve, given the uncertainty in the present study. Minor amounts of sodium and aluminum entering the structure of quartz and the intimate intergrowth texture of the run products may contribute to the ob- served pressure shift. Combined petrological and mineralogical studies on the run products and the natural rocks yield the fol- lowing 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 assemblage. During 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 pro- tolith, type-II-quartz represents a newly formed reaction product of albite. During 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 im- purities of Na and A1. At a later stage during further subduction, type-II-quartz also decomposes to form coesite. These studies represent an important puzzlement for a better understanding of the evolution of jadeite- quartzite fro

关键词： jadeite-quartzite high.pressure experiment albite

A New Triassic Primitive Ichthyosaur from Yuanan, South China

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Acta Geologica Sinica(English Edition) 2013年第3期87卷 672-677页

作者： CHEN Xiaohong P. Martin SANDEr CHENG Long WANG Xiaofeng Wuhan Centre of China Geological Survey Steinmann-institut für geologie Mineralogie und Palontologie Universitt Bonn

Based on the systematic study of two fossil skeleton specimens collected from the top of the third member of the marine Lower Triassic Jialingjiang formation of Yuanan, Hubei Province, South China, a new Early Triassic primitive ichthyosaur Chaohusaurus zhang]iawanensis sp. nov. is reported and described. The beds yielding the type material are correlated with the Neospathodus homeri-N, triangularis Conodont zone. The new taxon is most similar to Chaohusaurus geishanensis Young and Dong, 1972 in the shape and configuration of the scapula, forefin, pelvic girdle and hindfin, presacral vertebral count and well-developed caudal peak, but distinguished from the latter by its larger size, the position of the pineal foramen in the centre of the parietal, the occurrence of a larger calcaneum in hindfin and the first sacral rib with distal expansion. The new species exhibits common features of primitive ichthyosaurs such as：（1） the prefrontal has an antero-dorsal shelf projecting towards the orbit; （2） the upper temporal fenestra is small; （3） the postorbital and the squamosal meet laterally to the upper temporal fenestra; and （4） cylindrical centra. However, more derived ichthyosaur characters are seen with the frontal separated from the orbital dorsal margin by the contact of the prefrontal and postfrontal, which offer new clues to the early radiation of ichthyosaurs.

关键词： vertebrate paleontology reptilian ichthyosauria Lower Triassic (Spathian) Hubei Province

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

rECOrD Of BLOCK rOTATION AND MAGNETIC fIELD rEVErSALS IN THE TETHYAN HIMALAYA(HIDDEN VALLEY,CENTrAL NEPAL)

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地学前缘 2000年第S1期7卷 56-57页

作者： C.Crouzet H.Stang E.Schill E.Appel institut für geologie und Pal█ontologie Abteilung GeophysikUniversitat TübingenSigwartstrasse 1072076 TübingenGermany

Metasediments from the Tethyan Himalaya (TH) were sampled for paleomagnetic studies in several areas. In this paper, we will present the first results from Carboniferous and Early Triassic marly limestones from Hidden Valley (Central Nepal).. The paleomagnetic directions reflect a Tertiary overprint probably synchronous with the metamorphism. In this area, the metamorphic conditions reached during Tertiary are poorly constrained. Temperatures are probably in between 300 and 400℃. The age of the thermal event is still debated. No geochronological data is available in this area. Previously published geochronological data from the northern part of TH metasediments in India ranges from 47 to 42Ma (Ar/Ar Illite) after Weissman et al. (1999) and Bonhomme and Garzanti (1991). While in the southern part (close to HHC), biotite Ar/Ar data ranges from 30 to 26Ma in Marsyandi Valley (Coleman and Hodges, 1998) and muscovite Ar/Ar ranges from 18 to 12Ma in the upper Kali Gandaki Valley (Godin et al., 1998).. In this context, the age of the magnetization can′t be defined with precision.

关键词： paleomagnetism Central Nepal Tethyan Himalaya block rotation thermal evolution

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 possibly the coldest spell in our planet＇s long history： the Cryogenian Period. ‘Snowball Earth 2006＇ was organized by a research group at the ETH in Zurich under the leadership of Professor Philip Allen, now at Imperial College, London, and was the first conference to focus solely on this topic. The Cryogenian global freeze of about 7204535 million years ago closely preceded--some would say ominously so--the first fossil evidence for animal life on Earth, and as such has attracted the attention of natural scientists worldwide. Such a resurgence of interest in deep Earth history has not been witnessed since the great K/T boundary debate of the early 1980s. On the first day of the conference, on a hot and sultry evening during the hottest July on record, it was ice of a different kind that was being broken high above Lago Maggiore. The first hesitant introductions over chilled white wine made it clear that a tluly multidisciplinary throng had been invited for what promised to be a vigorous debate on the causes and effects of Neoproterozoic climate change. Gathered for the ＇snowball fight＇ were geologists, palaeobiologists, geochemists, geophysicists and climate modellers, all of whom would, one-by-one over the coming five days, borrow centre stage to offer their unique perspective on this most polarizing of topics.

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.

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

Metamorphic Characteristics and Tectonic Implications of the Kadui Blueschist in the Central Yarlung Zangbo Suture Zone,Southern Tibet

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Journal of Earth Science 2018年第5期29卷 1026-1039页

作者： Guangming Sun Xu-Ping Li WenYong Duan Shuang Chen Zeli Wang Lingquan Zhao Qingda feng Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals Shandong University of Science and TechnologyQingdao 266590China institut fur geologie Mineralogie und GeophysikRuhr-UniversitatBochum 44780Germany Center of Hydrogeology and Environmental Geology Survey China Geological SurveyBaoding 071051China

The Kadui blueschist is located in the central section of Yarlung Zangbo suture zone （YZSZ）, southern Tibet, and has been subjected to the subduction of the Neo-Tethyan Ocean below the Asian Plate and provides important clues for better understanding the evolution of the India-Asia convergence zone. In this paper, the systematical petrographic and mineral chemical studies were carried out on the Kadui blueschist, which reveal a mineral assemblage of sodic amphibole, chlorite, epidote, albite and quartz with accessory minerals of titanite, calcite and zircon. Electron microprobe analyses demonstrate that amphibole shows zoned from actinolite core to ferrowinchite/riebeckite rim composition indicating that the sodic amphibole has formed during a prograde metamorphic event. The protolith of the blueschist is an intermediate-basic pyroclastic rock. The calculated pseudosection indicates a clockwise P-T path and constrains peak metamorphic conditions of about 5.9 kbar at 345 ℃. This condition is transitional between pumpellyite-actinolite, greenschist and blueschist facies with a burial depth of 20-22 km and a thermal gradient of 15-16 ℃/km. This thermal gradient belongs to high pressure intermediate P/T facies series and is possibly related to a warm subduction setting of young oceanic slabs. Our new findings indicate that the Kadui blueschist in the central part of YZSZ experienced a rapid subduction and exhumation process as a response to a northward subduction of the Neo-Tethyan oceanic lithosphere during the initial India-Asia collision stage.

关键词： Kadui blueschist metamorphism P-T conditions accretionary complex southern Tibet.

APPrOXIMATE CALCULATION Of SOLAr rADIATION TrANSfEr IN CLEAr ATMOSPHErE

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Chinese Science Bulletin 1989年第11期34卷 930-932页

作者：赵高祥汪宏七 B.rOCKEL E.rASCHKE institute of Atmospheric Physics Academia Sinica Beijing institut fuer geophysik und Meteorologic der Universitaet zu Koeln

Bsaed on two-stream approximation, the upward and downward diffuse solar radiation flux densities, M_i^+ and M_i^-, in a plane-parallel atmosphere can be expressed

关键词： solar radiation atmosphere diffuse radiation.