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Dust growth in protoplanetary disks-a comprehensive experimental / theoretical approach

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research in Astronomy and Astrophysics 2010年第12期10卷 1199-1214页

作者： Jürgen Blum institut für geophysik und extraterrestrische Physik University of Braunschweig

More than a decade of dedicated experimental work on the collisional physics of protoplanetary dust has brought us to a point at which the growth of dust aggregates can - for the first time - be self-consistently and reliably modeled. In this article, the emergent collision model for protoplanetery dust aggregates, as well as the numerical model for the evolution of dust aggregates in protoplanetary disks, is reviewed. It turns out that, after a brief period of rapid collisional growth of fluffy dust aggregates to sizes of a few centimeters, the protoplanetary dust particles are subject to bouncing collisions, in which their porosity is considerably decreased. the model results also show that low-velocity fragmentation can reduce the final mass of the dust aggregates but that it does not trigger a new growth mode as discussed previously. According to the current stage of our model, the direct formation of kilometer-sized planetesimals by collisional sticking seems unlikely, implying that collective effects, such as the streaming instability and the gravitational instability in dust-enhanced regions of the protoplanetary disk, are the best candidates for the processes leading to planetesimals.

关键词： planetary systems: protoplanetary disks -- planetary systems: formation-- methods: laboratory -- methods: numerical

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

LIU tUNGSHENG'S PALAEOMAGNEtIC LOESS rESEArCH IN SWItZErLAND

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第四纪研究 2009年第5期29卷 847-850页

作者： friedrich Heller institut für geophysik EtH-Zentrum CH-8092 Zürich

11月22日是刘东生先生的生日,在先生离开我们的一年多时间里,我们时刻在怀念他。这里我们刊登了刘先生的密友之一、瑞士的Heller教授的短文,怀念与刘先生一起研究黄土磁学的点点滴滴。本文是Heller教授为刘先生的纪念文集撰写的,但因故... 详细信息

11月22日是刘东生先生的生日,在先生离开我们的一年多时间里,我们时刻在怀念他。这里我们刊登了刘先生的密友之一、瑞士的Heller教授的短文,怀念与刘先生一起研究黄土磁学的点点滴滴。本文是Heller教授为刘先生的纪念文集撰写的,但因故未及在文集中刊出。现在本刊补登,除了表示对先生的深切怀念,也表示对Heller教授的感谢和歉意。

关键词：黄土磁学研究刘东

Improved responses with Multitaper Spectral Analysis for Magnetotelluric time Series Data Processing:Examples from field Data

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Acta Geologica Sinica(English Edition) 2024年第S1期98卷 14-17页

作者： Matthew J.COMEAU rafael rIGAUD Johanna PLEtt Michael BECKEN Alexey KUVSHINOV Department of Geoscience&Engineering Delft University of technology The Netherlands institute of Geophysics ETHZürichSwitzerland institut für geophysik Universität MünsterGermany

In order to attain good quality transfer function estimates from magnetotelluric field data(i.e.,smooth behavior and small uncertainties across all frequencies),we compare time series data processing with and without a multitaper approach for spectral *** are several common ways to increase the reliability of the fourier spectral estimation from experimental(noisy)data;for example to subdivide the experimental time series into segments,taper these segments(using single taper),perform the fourier transform of the individual segments,and average the resulting spectra.

关键词： magnetotellurics electrical resistivity time series processing fourier analysis multitaper

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

Imaging the Architecture of Mineral Systems and the Pathways of Ore-forming fluids across Mongolia with Magnetotellurics

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Acta Geologica Sinica(English Edition) 2024年第S1期98卷 11-13页

作者： Matthew J.COMEAU rafael rIGAUD Erdenechimeg BAtMAGNAI Shoovdor tSErENDUG Sodnomsambuu DEMBErEL Michael BECKEN Alexey KUVSHINOV Department of Geoscience&Engineering Delft University of technology The Netherlands institute of Geophysics ETHZürichSwitzerland institute of Astronomy and Geophysics Mongolian Academy of SciencesUlaanbaatarMongolia institut für geophysik Universität MünsterGermany

In the framework of a mineral system approach,a combination of components is required to develop a mineral *** includes the whole-lithosphere architecture,which controls the transport of ore-forming fluids,and favorable tectonic and geodynamic processes,occurring at various spatial and temporal scales,that influence the genesis and evolution of ore-forming fluids(Huston et al.,2016;Groves et al.,2018;Davies et al.,2020).Knowledge of the deep structural framework can advance the understanding of the development of a mineral system and the emplacement of mineral *** geophysical exploration carried out with this aim is increasingly important for targeting new ore deposits in unexplored and underexplored regions(Dentith et al.,2018;Dentith,2019).

关键词： magnetotellurics electrical resistivity mineral exploration mineral emplacement ore fluids fluid transport

Investigating the Whole-lithosphere Structure of a Mineral System——Pathways and Source of Ore-forming fluids Imaged with Magnetotelluric Modeling

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Acta Geologica Sinica(English Edition) 2021年第S1期95卷 73-75页

作者： Matthew J.COMEAU Michael BECKEN Alexey V.KUVSHINOV Sodnomsambuu DEMBErEL Erdenechimeg BAtMAGNAI Shoovdor tSErENDUG institut für geophysik Universitat MünsterGermany institute of Geophysics ETHZürichSwitzerland institute of Astronomy and Geophysics Mongolian Academy of SciencesUlaanbaatarMongolia

Whole-lithosphere structure has direct implications for both the genesis of minerals and the locations of mineral emplacement;thus knowledge of the deep structural framework of the lithosphere can advance understandin... 详细信息

关键词： magnetotellurics electrical resistivity lithosphere structure mineral exploration metal belt oreforming fluids mineral emplacement fluid transport

An Asthenospheric Upwelling Beneath Central Mongolia——Implications for Intraplate Surface Uplift and Volcanism

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Acta Geologica Sinica(English Edition) 2021年第S1期95卷 70-72页

作者： Matthew J.COMEAU Michael BECKEN Alexey V.KUVSHINOV Alexander GrAYVEr Johannes KAUfL Erdenechimeg BAtMAGNAI Shoovdor tSErENDUG Sodnomsambuu DEMBErEL institut für geophysik Universitat MünsterGermany institute of Geophysics ETHZürichSwitzerland institute of Astronomy and Geophysics Mongolian Academy of SciencesUlaanbaatarMongolia

Intraplate processes,such as continental surface uplift and intraplate volcanism,are enigmatic and the underlying mechanisms responsible are not fully *** Mongolia is an ideal natural laboratory for studying such proc... 详细信息

关键词： magnetotellurics electrical resistivity lithosphere structure intraplate volcanism surface uplift mantle upwelling lithosphere removal thermo-mechanical modeling

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