The structural configuration of the first dome of Justinian's Hagia Sophia (A.D. 537–558): An investigation based on structural and literary analysis     

Ahmet Ş. Çakmak  Rabun M. Taylor  Eser Durukal 《Soil Dynamics and Earthquake Engineering》2009

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Behavior of apatite in granitic melts derived from partial melting of muscovite in metasedimentary sources     

《China Geology》2021,4(1):44-55

Fluid-absent and fluid-fluxed melting of muscovite in metasedimentary sources are two types of crustal anatexis to produce the Himalaya Cenozoic leucogranites. Apatite grains separated from melts derived from the two types of parting melting have different geochemical compositions. The leucogranites derived from fluid-fluxed melting have relict apatite grains and magmatic crystallized apatite grains, by contrast, there are only crystallized apatite grains in the leucogranites derived from fluid-absent melting. Moreover, apatite grains crystallized from fluid-fluxed melting of muscovite contain higher Sr, but lower Th and LREE than those from fluid-absent melting of muscovite, which could be controlled by the distribution of partitioning coefficient (D_Ap/Melt) between apatite and leucogranite. D_Ap/Melt in granites derived from fluid-absent melting is higher than those from fluid-fluxed melting. So, not only SiO₂ and A/CNK, but also types of crustal anatexis are sensitive to trace element partition coefficients for apatite. In addition, due to being not susceptible to alteration, apatite has a high potential to yield information about petrogenetic processes that are invisible at the whole-rock scale and thus is a useful tool as a petrogenetic indicator.©2021 China Geology Editorial Office.  相似文献   

中国南极第三次内陆冰盖考察剖面的雪貌及气象特征     

黄声享  鄂栋臣  陈春明  王清华 《武汉大学学报(信息科学版)》2000,25(3):252-256

给出了中国第三次南极考察的线路图、纵断面图及距离中山站 68～ 4 64km路段的表面年积雪状况图 ,分析了海拔高度的测定精度。同时 ,就考察剖面的雪貌及常规气象 (包括大气温度、湿度、气压和风速等 )特征进行了描述。  相似文献   

Elevation change around Dome A region of Antarctica from EnviSat satellite radar altimetry during 2002–2012     

Qiang Qiang  Mingsheng Liao  Qiuyang Zhao  Zemin Wang 《地球空间信息科学学报》2013,16(4):193-199

The expected responses of ice sheets to climate warming are growth in the thickness of the inland ice areas and thinning near the margins. In recent decades, researchers have identified glacier acceleration along Antarctic ice sheet coastal margins. However, the study of ice sheet interiors where seasonal accumulation eventually balances ice wastage at the lower elevation is poorly understood. In this paper, the ice sheet elevation change around Dome A region is analyzed from 2002 to 2012 using two million elevation change measurements from EnviSat satellite radar altimeter data covering an area of about 7000 km². A declining trend of 0.572 ± 1.31 mm/year which means that the Dome A region was in balance during the last decade can be captured. In addition, two obvious changes in accumulation which divide elevation change time series into three independent equilibration stages are also extracted. In order to explain this phenomenon, two speculations related to snowfall and firn compaction are proposed in this paper.  相似文献   

Mirror seeing of the Antarctic survey telescope     

ZHANG Kaiyuan  LI Zhengyang  YUAN Xiangyan  PEI Chong 《极地研究(英文版)》2014,(3):133-137

Site testing results indicate that Antarctic Dome A is an excellent ground-based astronomical site suitable for observations ranging from visible to infrared wavelengths. However, the harsh environment in Antarctica, especially the very low temperature and atmospheric pressure, always produces frost on the telescopes＇ mirrors, which are exposed to the air. Since the Dome A site is still unattended, the Antarctic telescope tubes are always designed to be filled with dry nitrogen, and the outer surfaces of the optical system are heated by an indium-tin oxide thin film. These precautions can prevent the optical surfaces from frosting over, but they degrade the image quality by introducing additional mirror seeing. Based on testing observations of the second Antarctic Survey Telescope （AST3-2） in the Mohe site in China, mirror seeing resulting from the heated aspheric plate has been measured using micro-thermal sensors. Results comparing the real-time atmospheric seeing monitored by the Differential Image Motion Monitor and real-time examinations of image quality agree well.  相似文献   

An assessment of variations in mercury deposition to Antarctica over the past 34,000 years     

尹雪斌  孙立广  谢周清 《极地研究(英文版)》2003,14(2)

We performed a comparison analysis of the variations .in Mercury ( Hg) concentrations and the precipitation proxies ( e. g. , 18 O values and 10 Be concentrations) in the Dome C ice core. The results showed that there were significant correlations between Hg and δ 10O values, 10Be concentrations, indicating that the accumulation rate in Dome C is one of the key factors controlling the variations of Hg concentrations in the past 34 ,000 years, and implying that Hg concentrations in ice core can be used as another reliable proxy of precipitation rate in Antarctica. Based upon the high-resolution δ 18O values, we estimated the variations in mercury deposition flux to Antarctica over the past 34,000 years. The highest mercury deposition flux is about 3. 80 pg cm-2 yr-1 during the Last Glacial Maxium (LGM) as high as 3. 5 times of the mercury deposition flux ( about 1. 08 pg cm -2 yr -1) in Holocene due to the fluctuations in natural mercury emissions such as the oceanic biological emissions.  相似文献   

Structural characteristics and active time of the Kangmar detachment,southern TibetEI北大核心CSCD     

Wang X.  Zhang J.  Yan S.  Liu J. 《大地构造与成矿学》2015,(2):250-259

The Kangmar gneiss dome, typical of the north Himalayan gneiss domes, is composed of three tectono- lithologic units separated by an upper and a lower detachment fault (Kangmar detachment fault). The low-grade metamorphic Tethyan Himalayan sedimentary sequence formed the upper unit above the brittle upper detachment fault. The mylonitic granites and two-mica granites made up the lower unit beneath the ductile lower detachment fault. The mylonitc middle-grade garnet two-mica schist and biotite-plagioclase gneiss constituted the middle unit inbetween the two detachment faults and were involved in the ductile deformation of the Kangmar detachment fault. The meso- and micro-scale structural analyses on the tectonites from the detachment fault zone indicated that the Kangmar detachment fault experienced a top-down-to-north shear. Integrating macro-/micro-analyses of petrology and mineralogy, this study adopts 40Ar/39Ar dating method to constrain the active time of the Kangmar detachment fault. Analyses of the syn-deformation muscovite from the mylonitic garnet two-mica schist yield a 40Ar/39Ar plateau age of 13.23±0.15 Ma, representing the active time of the Kangmar detachment fault. The chronological result hints that the Kangmar detachment was synchronous with the south Tibet detachment systems to the south and was probably part of the south Tibet detachment systems exposed in the Tethyan Himalayan sedimentary sequence. However, this hypothesis needs from the supports of more geological and geophysical evidence. ©, 2015, Science Press. All right reserved.  相似文献   

Specific features in distribution of natural radioactivity in rocks of the Bazhenovo Formation on the western slope of the Surgut Dome,West Siberia     

G. A. Kalmykov  N. S. Balushkina  A. P. Aleshin  N. K. Glebocheva 《Moscow University Geology Bulletin》2009,64(1):35-42

This paper presents an analysis of the radioactivity distribution in the Bazhenovo Formation rocks on the western slope of the Surgut Dome. The maximum uranium concentrations are confined to accumulations of organic matter and are proportional to its concentration in the rocks. The lowermost part of the section has lower radioactivity values than the upper one. The value of radioactivity varies throughout the area of the Surgut Dome. Coeval analogs of the Bazhenovo Formation show lower radioactivity values.  相似文献   

藏南拉轨岗日隆起带东段哈金桑惹隆起东侧发现夕卡岩型多金属矿化带     

王克友  赵兴国  周志广  张祥信  辛洪波 《安徽地质》2005,15(4):256-259

哈金桑惹隆起上的夕卡岩型多金属矿化带是在开展1：25万江孜县幅区调工作时首次发现的。该矿化带的矿石组合具钙夕卡岩型特征。共发现两个矿化体,Ⅰ号矿化体的有益元素以铜为主,伴生银、铅锌等;Ⅱ号矿化体有益元素以铅锌为主,伴生银和铜等。该矿化带的发现对该地区的找矿和基础地质研究具有重要的意义。  相似文献   

Dynamics of explosive volcanism at Unzen volcano: an experimental contribution     

Bettina Scheu  Oliver Spieler  Donald B. Dingwell 《Bulletin of Volcanology》2006,69(2):175-187

Knowledge of the dynamics of magma fragmentation is necessary for a better understanding of the explosive behaviour of silicic volcanoes. Here we have measured the fragmentation speed and the fragmentation threshold of five dacitic samples (6.7–53.5 vol% open porosity) from Unzen volcano, Kyushu, Japan. The measurements were carried out using a shock-tube-based fragmentation apparatus modified after Alidibirov and Dingwell (1996a,b). The results of the experimental work confirm the dominant influence of porosity on fragmentation dynamics. The velocity of the fragmentation front increases and the value of the fragmentation threshold decreases with increasing porosity. Further, we observe that the fragmentation speed is strongly influenced by the initial pressure difference and the texture of the dacite. At an initial pressure difference of 30 MPa, the fragmentation speed varies from 34 m/s for the least porous sample to 100 m/s for the most porous sample. These results are evaluated by applying them to the 1990–1995 eruptive activity of Unzen volcano. Emplacements of layered lava dome lobes, Merapi-type pyroclastic flows and minor explosive events dominated this eruption. The influence of the fragmentation dynamics on dome collapse and Vulcanian events is discussed.  相似文献