Discharge and suspended sediment dynamics during two jökulhlaups in the Skaftá river,Iceland     

Gareth H. Old  Damian M. Lawler  rni Snorrason 《地球表面变化过程与地形》2005,30(11):1441-1460

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Compositional variations (major and trace elements) of clinopyroxene and Ti-andradite from pyroxenite, ijolite and nepheline syenite, Alnö Island, Sweden     

Jaana Hode Vuorinen  Ulf H  lenius  Martin J. Whitehouse  Joakim Mansfeld  Alasdair D.L. Skelton 《Lithos》2005,81(1-4):55-77

Clinopyroxenes from pyroxenite, ijolite and nepheline syenite from the main intrusion of the Alnö complex define two sub-parallel compositional trends with respect to Na, Ca and Fe_TOT plotted against alkali-pyroxene fractionation index (Na–Mg). Both trends define a smooth fractionation of increasing Na and Fe_TOT and decreasing Ca with increasing Na–Mg, but one set of samples contain clinopyroxenes that constantly plot at higher Na and lower Fe_TOT and Ca (at similar Na–Mg) than the rest of the samples. Clinopyroxenes with higher Ca and Fe_TOT and lower Na (trend 1) co-exist with substantial amounts of Ti-andradite (up to 70 vol.%), while the sample set defining the more Na-rich trend (trend 2) lack co-existing Ti-andradite. Clinopyroxenes from both trends show fractionated REE patterns with a distinct difference in HREE content, reflecting the content of co-existing Ti-andradite. The rocks of the first Ti-andradite-bearing trend crystallized slightly prior to the rocks of the second trend, probably from a primitive, Ca- and Ti-rich nephelinitic magma. Crystallisation of pyroxenite and melteigite occurred under low aSiO₂ and high aCaO and aTiO₂ as evidenced by the presence of perovskite and sometimes substantial amounts of magnetite. Subsequent increase in aSiO₂ is evidenced in the overgrowth of perovskite by titanite, which in turn is overgrown by Ti-andradite. Nepheline syenitic residuals crystallized under higher aSiO₂ and aNa₂O and lower aCaO and aTiO₂, which reduced Ti-andradite into an accessory phase and produced more Si- and Na-rich clinopyroxenes. Some of these residuals probably also mixed with new primitive magma producing a hybrid magma that crystallised the more Na-rich and Ca- and Fe_TOT-poor clinopyroxenes of trend 2. The complete lack of Ti-andradite in these rocks indicates different crystallisation conditions and also a different magma composition.  相似文献   

Vegetation history of the penultimate glacial period (Marine isotope stage 6) at Ioannina,north‐west Greece     

K. H. Roucoux  P. C. Tzedakis  I. T. Lawson  V. Margari 《第四纪科学杂志》2011,26(6):616-626

The vegetational history of the penultimate glacial period, Marine Isotope Stage (MIS) 6 (c. 185–135 ka), has remained relatively unexplored. Here we present a new record from the Ioannina basin, north‐west Greece, which constitutes the highest‐resolution terrestrial pollen record for this interval produced to date. It shows that the vegetation history of MIS 6 in this region can be divided into two parts: an early period (185–155 ka) with pronounced oscillations in tree population extent, and a later period (155–135 ka) with much smaller tree populations and subdued oscillations. This pattern is analogous to the MIS 3/MIS 2 division during the last glacial in the same sequence, although the early part of MIS 6 had larger Pinus populations and fewer temperate trees relative to the equivalent interval in MIS 3. This implies cooler and wetter conditions, which is somewhat counterintuitive given the high summer insolation during MIS 6e, but is in line with other palaeoclimatic evidence from the Mediterranean. Comparison with North Atlantic records suggests that despite the absence of pronounced iceberg discharges during MIS 6, North Atlantic millennial‐scale variability had a significant downstream impact on tree populations in north‐west Greece. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

2017年南丹Ms4.0地震前后重力变化     

文翔  毕熙荣  覃坚  柴现凡  冯骢 《大地测量与地球动力学》2019,39(4):344-350

利用广西及邻区2014~2017年流动重力观测资料，系统分析区域重力场变化及其与2017-07-15广西南丹MS4.0地震的关系，并结合GPS观测数据与地震地质调查成果，探讨区域重力场变化的时空分布特征及机理。结果表明：1）南丹M_S4.0地震前后，震区附近重力异常变化与主干断裂关系密切，反映沿控震断裂在2014~2017年间发生了引起地表重力变化效应的地壳变形和构造活动；2）差分重力图像表明，南丹M_S4.0地震前重力变化为“局部重力异常→四象限重力异常→重力反向变化发震”的过程；3）重力变化与GPS 观测反映的水平运动表明，南丹M_S4.0地震位于重力四象限分布中心部位及面压缩峰值附近，证明重力场和形变场动态变化对中强地震地点预测具有指示意义；4）天峨-南丹-环江一带是重力变化最剧烈地区，亦是水平形变面压缩过渡带，同时位于莫霍面等深线强烈变化地段、M_L3.0地震围空区、沿主断裂存在的低b值异常区。结合地震活动图像、定点前兆观测异常综合分析认为，该地区仍存在发生中强地震的可能。  相似文献   

Iron isotopic systematics of UHP eclogites respond to oxidizing fluid during exhumation   总被引：1，自引：0，他引：1       下载免费PDF全文

D.‐Y. Li  Y. L. Xiao  W.‐Y. Li  X. Zhu  H. M. Williams  Y.‐L. Li 《Journal of Metamorphic Geology》2016,34(9):987-997

The iron stable isotope compositions (δ⁵⁶Fe) and iron valence states of ultrahigh‐pressure eclogites from Bixiling in the Dabie orogen belt, China, were measured to trace the changes of geochemical conditions during vertical transportation of earth materials, for example, oxygen fugacity. The bulk Fe³⁺/ΣFe ratios of retrograde eclogites, determined by Mössbauer spectroscopy, are consistently higher than those of fresh eclogites, suggesting oxidation during retrograde metamorphism and fluid infiltration. The studied eclogites (five samples) display limited mid‐ocean ridge basalts (MORB)‐like (~0.10‰) δ⁵⁶Fe values, which are indistinguishable from their protoliths, that is, gabbro cumulates formed through differentiation of mantle‐derived basaltic magma. This suggests that Fe isotope fractionation during continental subduction is limited. Garnet separates display limited δ⁵⁶Fe variation ranging from ?0.08 ± 0.07 ‰ to 0.02 ± 0.07‰, whereas coexisting omphacite displays a large variation of δ⁵⁶Fe values from 0.15 ± 0.07‰ to 0.47 ± 0.07‰. Omphacite also has highly variable Fe³⁺/ΣFe ratios from 0.367 ± 0.025 to 0.598 ± 0.024, indicating modification after peak metamorphism. Omphacite from retrograde eclogites has elevated Fe³⁺/ΣFe ratios (0.54–0.60) compared to that from fresh eclogites (~0.37), whereas garnet displays a narrow range of ferric iron content with Fe³⁺/ΣFe ratios from 0.039 ± 0.013 to 0.065 ± 0.022. The homogenous δ⁵⁶Fe values and Fe³⁺/ΣFe ratios of garnet suggest that it survived the retrograde metamorphism and preserved its Fe‐isotopic features and ferric contents of peak metamorphism. Because of similar diffusion rates of Fe and Mg in garnet and omphacite, and constant Δ²⁶Mg_{omphacite‐garnet} values (1.14 ± 0.04‰), equilibrium iron isotope fractionation between garnet and omphacite was probably achieved during peak metamorphism. Elevated Fe³⁺/ΣFe ratios of omphacite from retrograde eclogites and variant Δ⁵⁶Fe_{omphacite‐garnet} values of the studied eclogites (0.13 ± 0.10‰ to 0.48 ± 0.10‰) indicate that oxidized geofluid infiltration resulted in the elevation of δ⁵⁶Fe values of omphacite during retrograde metamorphism.  相似文献   

JDT-6陀螺测斜仪软件GyroSProcess设计与实现          下载免费PDF全文

陈华北  李聚光 《探矿工程》2016,43(1):31-35,39

针对JDT-6陀螺测斜仪配套软件“陀螺测斜仪JDT-6”在使用过程中显露出的同时需要串、并口进行通信,仍无法脱离Windows98操作系统现象,并根据工程实践中提出的新要求采用VB6开发了适用于这款仪器的软件GyroSProcess。新软件除涵盖原功能外,还在数据通信方面将串、并两条通道合二为一个USB口或COM口;导入已有测斜数据,减少数据采集量,提高测斜作业效率;计算机自动控制绞车的运行,使数据采集过程自动化;运用对象编程技术,将测斜图件转成AutoCAD形式。介绍了新软件部分增加功能中采用的关键技术、算法。经现场试验,证明GyroSProcess软件的测量结果与旧软件结果一致,可替代旧软件而成为JDT-6陀螺测斜仪的新一代配套软件。  相似文献   

青蛤(Cyclina sinensis) TRAF6基因克隆及其在Poly I:C胁迫下的免疫应答     

高玮玮  潘宝平  闫春财 《海洋与湖沼》2016,47(5):1040-1046

对青蛤(Cyclina sinensis)转录组文库筛选并克隆得到青蛤TRAF6(Cs TRAF6)基因的c DNA序列,其开放阅读框为2337bp,编码778个氨基酸,分子量为86.59k Da。Cs TRAF6蛋白包含RING型锌指结构,两个TRAF型锌指结构,coiled-coil结构域以及MATH结构域。经生物信息学及分子系统学分析表明Cs TRAF6属于TRAF6家族的一员。利用实时荧光定量PCR方法检测了Cs TRAF6基因在青蛤各个组织以及在Poly I:C侵染下在血淋巴中的时序性表达情况。结果表明,Cs TRAF6基因在青蛤血淋巴、闭壳肌、鳃、性腺、外套膜和肝脏中普遍表达,其中在血淋巴中的表达水平最高。在Poly I:C刺激后的3h,青蛤血淋巴中Cs TRAF6的表达量迅速升高,在6h达到最大值,说明青蛤的Cs TRAF6基因参与了病毒类似物侵染下的免疫应答反应。  相似文献   

基于SPOT6遥感影像的滩涂湿地入侵种互花米草植株高度的反演研究   总被引：1，自引：0，他引：1  

周在明  杨燕明  陈本清 《海洋学报》2016,38(6):1-7

本文以SPOT6 高空间分辨率遥感影像为数据源,通过植被覆盖度和地上生物量两个参数进行滩涂湿地入侵种互花米草植株高度的估算研究。结果表明,三沙湾滩涂湿地互花米草植株高度平均值为2.04 m,以1~2 m和2~3 m植株为主要分布高度,分布面积分别为6.83 km2和10.31 km2,占研究区互花米草总面积的33.83%和51.06%,小于1 m和大于3 m的互花米草仅占9.26%和5.84%。估算值与真实值之间的均方根误差为0.204,绝对误差为0.04~0.37 m。该方法是对高空间分辨率光学影像应用研究的重要尝试,其反演方法具有较好的可行性,可较为准确的获取滩涂湿地植株高度信息。  相似文献   

Molybdenum Mass Fractions and Isotopic Compositions of International Geological Reference Materials          下载免费PDF全文

Pei‐Pei Zhao  Jie Li  Le Zhang  Zhi‐Bing Wang  De‐Xin Kong  Jin‐Long Ma  Gang‐Jian Wei  Ji‐Feng Xu 《Geostandards and Geoanalytical Research》2016,40(2):217-226

The double‐spike method with multi‐collector inductively coupled plasma‐mass spectrometry was used to measure the Mo mass fractions and isotopic compositions of a set of geological reference materials including the mineral molybdenite, seawater, coral, as well as igneous and sedimentary rocks. The long‐term reproducibility of the Mo isotopic measurements, based on two‐year analyses of NIST SRM 3134 reference solutions and seawater samples, was ≤ 0.07‰ (two standard deviations, 2s, n = 167) for δ^98/95Mo. Accuracy was evaluated by analyses of Atlantic seawater, which yielded a mean δ^98/95Mo of 2.03 ± 0.06‰ (2s, n = 30, relative to NIST SRM 3134 = 0‰) and mass fraction of 0.0104 ± 0.0006 μg g^?1 (2s, n = 30), which is indistinguishable from seawater samples taken world‐wide and measured in other laboratories. The comprehensive data set presented in this study serves as a reference for quality assurance and interlaboratory comparison of high‐precision Mo mass fractions and isotopic compositions.  相似文献   

High Precision Sr‐Nd‐Hf‐Pb Isotopic Compositions of USGS Reference Material BCR‐2          下载免费PDF全文

Jason Jweda  Louise Bolge  Cornelia Class  Steven L. Goldstein 《Geostandards and Geoanalytical Research》2016,40(1):101-115

The Lamont‐Doherty Earth Observatory radiogenic isotope group has been systematically measuring Sr‐Nd‐Pb‐Hf isotopes of USGS reference material BCR‐2 (Columbia River Basalt 2), as a chemical processing and instrumental quality control monitor for isotopic measurements. BCR‐2 is now a widely used geochemical inter‐laboratory reference material (RM), with its predecessor BCR‐1 no longer available. Recognising that precise and accurate data on RMs is important for ensuring analytical quality and for comparing data between different laboratories, we present a compilation of multiple digestions and analyses made on BCR‐2 during the first author's dissertation research. The best estimates of Sr, Nd and Hf isotope ratios and measurement reproducibilities, after filtering at the 2s level for outliers, were ⁸⁷Sr/⁸⁶Sr = 0.705000 ± 11 (2s, 16 ppm, n = 21, sixteen digestions, one outlier), ¹⁴³Nd/¹⁴⁴Nd = 0.512637 ± 13 (2s, 25 ppm, n = 27, thirteen digestions, one outlier) and ¹⁷⁶Hf/¹⁷⁷Hf = 0.282866 ± 11 (2s, 39 ppm, n = 25, thirteen digestions, no outliers). Mean Nd and Hf values were within error of those reported by Weis et al. (2006, 2007) in their studies of RMs; mean Sr values were just outside the 2s uncertainty range of both laboratories. Moreover, a survey of published Sr‐Nd‐Hf data shows that our results fall within the range of reported values, but with a smaller variability. Our Pb isotope results on acid leached BCR‐2 aliquots (n = 26, twelve digestions, two outliers) were ²⁰⁶Pb/²⁰⁴Pb = 18.8029 ± 10 (2s, 55 ppm), ²⁰⁷Pb/²⁰⁴Pb = 15.6239 ± 8 (2s, 52 ppm), ²⁰⁸Pb/²⁰⁴Pb = 38.8287 ± 25 (2s, 63 ppm). We confirm that unleached BCR‐2 powder is contaminated with Pb, and that sufficient leaching prior to digestion is required to achieve accurate values for the uncontaminated Pb isotopic compositions.  相似文献