A new low-mass eclipsing binary: NSVS 02502726     

Ö. Çakırlı  C. İbanogˇlu  C. Güngör 《New Astronomy》2009,14(5):496-502

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Petrology of Al- and Cr-rich ophiolitic chromitites from the Muğla,SW Turkey: implications from composition of chromite,solid inclusions of platinum-group mineral,silicate, and base-metal mineral,and Os-isotope geochemistry     

İbrahim Uysal  Mahmud Tarkian  M. Burhan Sadiklar  Federica Zaccarini  Thomas Meisel  Giorgio Garuti  Stefanie Heidrich 《Contributions to Mineralogy and Petrology》2009,158(5):659-674

Ultramafic rocks around the city of Muğla in SW Turkey are represented by mantle peridotites depleted to various degrees, ranging from cpx-rich harzburgites to depleted harzburgite and dunite. Cpx-rich harzburgites are thought to be the residua left after extraction of MORB-type basalt, from which high-Al chromitite [49.2 < Cr# = 100 × Cr/(Cr + Al) < 53.5] crystallised with a higher proportion of ¹⁸⁷Os/¹⁸⁸Os (average of 0.1361). However, depleted harzburgites are assumed to be the residua left after extraction of hydrous boninitic melt produced by second stage partial melting of already depleted mantle due to a subducting slab, from which high-Cr chromitites (64.2 < Cr# < 85.9) with lower and heterogeneous ¹⁸⁷Os/¹⁸⁸Os ratio (average of 0.1324) were crystallised as a result of melt–rock interaction in a supra-subduction environment. Dunites around the chromite deposits are considered to be the product of melt–peridotite interaction. Most of the chromitites contain high-Cr chromite and display enrichment in IPGE (Os, Ir, Ru) over PPGE (Rh, Pt, Pd), with PGE concentrations between 61 and 1,305 ppb. Consistently, laurite-erlichmanite series minerals with various Os concentrations are found to be the most abundant PGM inclusions in chromite. Os–Ir–Ru alloy, irarsite, and kashinite, as well as Pt–Fe alloy and Pt-oxide, which are not common in ophiolitic chromitites, were also detected as magmatic PGM inclusions. Pentlandite, millerite, and, rarely heazlewoodite form the magmatic inclusions of base-metal sulphide. The presence of olivine and clinopyroxene, as well as hydrous silicate inclusions such as amphibole and phlogopite, in high-Cr chromitite supports the idea that high-Cr chromitites were formed in a supra-subduction environment.  相似文献   

Structure coefficients for use in stellar analysis     

Gülay İnlek  Edwin Budding 《Astrophysics and Space Science》2012,342(2):365-370

We present new values of the structural coefficients η _j , and related quantities, for realistic models of distorted stars in close binary systems. Our procedure involves numerical integration of Radau’s equation for detailed structural data and we verified our technique by referring to the 8-digit results of Brooker & Olle (Mon. Not. R. Astron. Soc. 115:101, 1955) for purely mathematical models. We provide tables of representative values of η _j , and related quantities, for j=2,3,…,7 for a selection of Zero Age Stellar Main Sequence (ZAMS) stellar models taken from the EZWeb compilation of the Dept. of Astronomy, University of Wisconsin-Madison. We include also some preliminary comparisons of our findings with the results of Claret and Gimenez (Astron. Astrophys. 519:A57 2010) for some observed stars.  相似文献   

Two‐dimensional speckle spectroscopy of Hα features     

N. Al  J. Hirzberger  F. Kneer 《Astronomische Nachrichten》2003,324(4):364-365

In May 2002, the solar chromosphere was observed with a two‐dimensional spectrometer which is mounted in the German Vacuum Tower Telescope (VTT) at the Observatorio del Teide/Tenerife. The aim of this observation was to investigate the fine structure of the solar chromosphere seen in Hα. We took narrow‐band filtergrams (Δλ ≈ 72 mÅ) by scanning through this line. Broad‐band images taken strictly simultaneously with the narrow‐band filtergrams were restored by speckle methods. The instantaneous optical transfer function from this restoration procedure was used for the reconstruction of the narrow‐band images. Some results of this high spatial resolution observation are presented below.  相似文献   

英国约克郡( Yo rkshire Dale)国家公园钙华苔藓植物群落研究   总被引：8，自引：0，他引：8  

张朝晖  艾伦.培特客斯 《中国岩溶》1999,18(4):367-374

报道英国约克郡国家公园5个钙华沉积地点苔藓植物群落调查结果。该区域钙华苔藓群落共13个,由12科15属18种组成。区系地理成分由北温带和世界广布两种成分组成;生活型以垫状矮丛集型和交织型占优势。根据钙华沉积环境特征,划分Cron钙华苔藓群落、洞穴钙华苔藓群落、瀑华苔藓群落、峭壁钙华苔藓群落和泉华苔藓群落等5种类型。调查结果表明,研究区现代苔藓植物群落钙华沉积作用十分显著。   相似文献   

Microseismic events enhancement and detection in sensor arrays using autocorrelation‐based filtering          下载免费PDF全文

Entao Liu  Lijun Zhu  Anupama Govinda Raj  James H. McClellan  Abdullatif Al‐Shuhail  SanLinn I. Kaka  Naveed Iqbal 《Geophysical Prospecting》2017,65(6):1496-1509

Passive microseismic data are commonly buried in noise, which presents a significant challenge for signal detection and recovery. For recordings from a surface sensor array where each trace contains a time‐delayed arrival from the event, we propose an autocorrelation‐based stacking method that designs a denoising filter from all the traces, as well as a multi‐channel detection scheme. This approach circumvents the issue of time aligning the traces prior to stacking because every trace's autocorrelation is centred at zero in the lag domain. The effect of white noise is concentrated near zero lag; thus, the filter design requires a predictable adjustment of the zero‐lag value. Truncation of the autocorrelation is employed to smooth the impulse response of the denoising filter. In order to extend the applicability of the algorithm, we also propose a noise prewhitening scheme that addresses cases with coloured noise. The simplicity and robustness of this method are validated with synthetic and real seismic traces.  相似文献   

Normal fault growth and linkage in the Gediz (Alaşehir) Graben,Western Turkey,revealed by transient river long‐profiles and slope‐break knickpoints          下载免费PDF全文

Emiko Kent  Sarah J. Boulton  Alexander C. Whittaker  Iain S. Stewart  M. Cihat Alçiçek 《地球表面变化过程与地形》2017,42(5):836-852

The Gediz (Ala?ehir) Graben is located in the highly tectonically active and seismogenic region of Western Turkey. The rivers upstream of the normal fault‐bounded graben each contain a non‐lithologic knickpoint, including those that drain through inferred fault segment boundaries. Knickpoint heights measured vertically from the fault scale with footwall relief and documented fault throw (vertical displacement). Consequently, we deduce these knickpoints were initiated by an increase in slip rate on the basin‐bounding fault, driven by linkage of the three main fault segments of the high‐angle graben bounding fault array. Fault interaction theory and ratios of channel steepness suggest that the slip rate enhancement factor on linkage was a factor of 3. We combine this information with geomorphic and structural constraints to estimate that linkage took place between 0.6 Ma and 1 Ma. Calculated pre‐ and post‐linkage throw rates are 0.6 and 2 mm/yr respectively. Maximum knickpoint retreat rates upstream of the faults range from 4.5 to 28 mm/yr, faster than for similar catchments upstream of normal faults in the Central Apennines and the Hatay Graben of Turkey, and implying a fluvial landscape response time of 1.6 to 2.7 Myr. We explore the relative controls of drainage area and precipitation on these retreat rates, and conclude that while climate variation and fault throw rate partially explain the variations seen, lithology remains a potentially important but poorly characterised variable. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Seafloor seismic acquisition using autonomous underwater vehicles     

Constantinos Tsingas  Thierry Brizard  Abdulaziz Al Muhaidib 《Geophysical Prospecting》2019,67(6):1557-1570

Although narrow-azimuth towed-streamer data provide good image quality for structural interpretation, it is generally accepted that for wide-azimuth marine surveys seabed receivers deliver superior seismic reflection measurements and seismically derived reservoir attributes. However, seabed surveys are not widely used due to the higher acquisition costs when compared to streamer acquisition. In recent years, there have been significant engineering efforts to automate receiver deployment and retrieval in order to minimize the cost differential and conduct cost-efficient seabed receiver seismic surveys. These engineering efforts include industrially engineered nodes, nodes on a rope deployment schemes and even robotic nodes, which swim to and from the deployment location. This move to automation is inevitable, leading to robotization of seismic data acquisition for exploration and development activities in the oil and gas industry. We are developing a robotic-based technology, which utilizes autonomous underwater vehicles as seismic sensors without the need of using a remotely operated vehicle for deployment and retrieval. In this paper, we describe the autonomous underwater vehicle evolution throughout the project years from initial heavy and bulky nodes to fully autonomous light and flexible underwater receivers. Results obtained from two field pilot tests using different generations of autonomous underwater vehicles indicate that the seismic coupling, and navigation based on underwater acoustics are very reliable and robust.  相似文献   

Morphometric analysis of Chattian–Early Aquitanian Miogypsinidae from Iraq and their stratigraphic distribution in the Arabian Tethys     

Qahtan A. M. Al Nuaimy 《Arabian Journal of Geosciences》2017,10(24):542

A biometric study of Chattian–Early Aquitanian taxa from shallow marine transgressive carbonate deposits in the Oligo-Miocene sedimentary basin of Kirkuk, Iraq, provides new insight into their taxonomy, stratigraphy, and palaeobiogeography. Their evolution is based on a distinct change in general nepiont morphology, which agrees with the principle of nepionic acceleration. Each Miogypsinoides group is represented by more than one lineage. We demonstrate for the first time the parallel evolution of Miogypsina and Miogypsinoides in the late Chattian of north-eastern Iraq. We assign specimens into two lineage groups: Miogypsinoides formosensis of the Late Chattian, with smaller embryon and longer post-embryonic spirals, which evolved into Miogypsinoides bantamensis of the Early Aquitanian; and Miogypsinoides sivasensis, with shorter spirals and larger embryon, originally found in late Chattian to Early Aquitanian deposits. This group evolved into large embryon and longer post-embryonic spiral specimens of the upper Azkand Formation, assigned to Miogypsinoides dehaartii and associated with Miogypsina gunteri-basraensis and M. gunteri due to their peculiar morphological features. Miogypsina specimens are related to Miogypsina basraensis, which have much smaller embryon dimensions. This part of the sequence corresponds to Ms. formosensis and is overlain by a Miogypsina ex. interc. gunteri-basraensis succession, a composite species that evolved to Miogypsina gunteri, the most common Miogypsinids taxon in the carbonate upper Azkand Formation, thereby acting as a reference for the evolution of this taxon and its transition to M. ex. interc. tani-gunteri. Miogypsinoides evolution in the Iraqi sedimentary basin is similar to Western Tethys evolution yet differs from Indo-Pacific evolution.  相似文献   

Impact of rock-water interactions and recharge on water resources quality of the Agadir-Essaouira basin,southwestern Morocco     

Al Yacoubi Latifa  Bouchaou Lhoussaine  Jaillard Etienne  Masrour Moussa  Ait Brahim Yassine  El Mouden Ahmed  Schneider Jana  Reichert Barbara 《Arabian Journal of Geosciences》2017,10(7):169

The Agadir-Essaouira area in the occidental High Atlas Mountains of Morocco is characterized by a semi-arid climate. The scarcity and quality of water resources, exacerbated by long drought periods, constitute a major problem for a sustainable development of this region. Groundwater resources of carbonate units within Jurassic and Cretaceous aquifers are requested for drinking and irrigation purposes. In this study, we collected 84 samples from wells, boreholes, springs, and rivers. Hydrochemical and isotopic data were used to examine the mineralization and origin of water, which control groundwater quality. The chemical composition of water seems to be controlled by water-rock interactions, such as dissolution of carbonates (calcite and dolomite), weathering of gypsum, as well as ion exchange processes, which explain the observed variability. Stable isotopes results show that groundwater from the mainly marly Cretaceous aquifer are submitted to an evaporation effect, while samples from the chiefly calcareous Jurassic aquifer indicate a meteoric origin, due to a rapid infiltration of recharge runoff through the karstic outcrops. The low values of δ¹⁸O and δ²H suggest a local recharge from areas with elevations ranging from 400 to 1200 m for the Cretaceous aquifer and from 800 to 1500 m for the Jurassic units.  相似文献