Timing of UHP metamorphism in the Hong’an area,western Dabie Mountains,China: evidence from zircon U–Pb age,trace element and Hf isotope composition

The Hong’an area (western Dabie Mountains) is the westernmost terrane in the Qinling-Dabie-Sulu orogen that preserves UHP eclogites. The ages of the UHP metamorphism have not been well constrained, and thus hinder our understanding of the tectonic evolution of this area. LA-ICPMS U–Pb age, trace element and Hf isotope compositions of zircons of a granitic gneiss and an eclogite from the Xinxian UHP unit in the Hong’an area were analyzed to constrain the age of the UHP metamorphism. Most zircons are unzoned or show sector zoning. They have low trace element concentrations, without significant negative Eu anomalies. These metamorphic zircons can be further subdivided into two groups according to their U–Pb ages, and trace element and Lu–Hf isotope compositions. One group with an average age of 239 ± 2 Ma show relatively high and variable HREE contents (527 ≥ Lu_N ≥ 14) and ¹⁷⁶Lu/¹⁷⁷Hf ratios (0.00008–0.000931), indicating their growth prior to a great deal of garnet growth in the late stage of continental subduction. The other group yields an average age of 227 ± 2 Ma, and shows consistent low HREE contents and ¹⁷⁶Lu/¹⁷⁷Hf ratios, suggesting their growth with concurrent garnet crystallization and/or recrystallization. These two groups of age are taken as recording the time of prograde HP to UHP and retrograde UHP–HP stages, respectively. A few cores have high Th/U ratios, high trace element contents, and a clear negative Eu anomaly. These features support a magmatic origin of these zircon cores. The upper intercept ages of 771 ± 86 and 752 ± 70 Ma for the granitic gneiss and eclogite, respectively, indicate that their protoliths probably formed as a bimodal suite in rifting zones in the northern margin of the Yangtze Block. Young Hf model ages (T _DM1) of magmatic cores indicate juvenile (mantle-derived) materials were involved in their protolith formation. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

15N示踪-离子质谱法测定新生产力的研究

本文提出了~(15)N示踪-离子质谱法实测新生产力的方法,并于1991年11月—1992年5月结合胶州湾现场调查的实际样品,对示踪剂量、培养时间、样品贮存、消解剂量和时间、铵离子的扩散吸收,以及方法的空白值、检出限、精密度和准确度等进行了实验研究。结果表明,该法具有较高的精密度和良好的准确度,与经典的气体质谱法相比,还具有进样量少以及可同时分析~(15)N丰度、总氮浓度和水中铵离子浓度等特点,对于含氮量极低、铵氮再生迅速的海洋环境中新生产力的研究,具有特殊的意义。     

盐胁迫对番茄同工酶基因表达的影响

分析了普通番茄（Lycopersicumesculentum）在NaCl胁迫下酯酶（EST）和过氧化物酶（PRX）同工酶的变化，考察了盐胁迫对10个同工酶位点21个等位基因在特定组织中表达的影响。发现许多EST和PRX等位基因在盐胁迫下表达，产生盐诱导同工酶；另有些等位基因的表达受盐抑制，它们在盐胁迫下的表达活性显著减弱或消失。实验表明，EST和PRX同工酶表达的变化与番茄对盐胁迫的遗传适应性有密切关系。     

地震折射波的虚拟射线理论及其应用

本文提出了一种地震折射液的虚拟射线理论,根据该理论,只要已知地表层的速度,即可直接由折射波信息提取地震参数,从而可实现折射界面的反演。 文中通过实际介质模型的计算机实验结果,验证了该理论的正确性。     

Magnitude-frequency relationship of coastal sand delivery by a southern California stream

Coastal sand delivery by a stream in southern California is estimated based on a numerical model which stimulates unsteady flow, sediment transport, and the associated channel adjustments for a stream-delta system. An average annual sediment yield of 51,400 m³/yr is estimated for the San Dieguito River, which drains a semiarid watershed controlled by dams. Of the total sand delivery by the stream, 20.5 percent is contributed from floods greater than the 100-year flood; 17.6 percent from those between the 50- and 100-year events; 28.4 percent from those between the 25- and 50 year floods; and 33.5 percent from those smaller than the 25-year flood.     

Characteristics of Scour and Deposition in Front of Breakwaters Under Irregular Broken Clapotis

First the scour and deposition patterns of the sandy seabed in front of a vertical breakwater under the action of irregular broken clapotis are investigated experimentally and classified into five types: scour type Ⅰ , scour type Ⅱ, scour type Ⅲ, deposition type Ⅰ, and deposition type Ⅱ . Secondly, the processes of formation of scour and deposition patterns are probed in comparison with those induced by regular broken clapotis and standing waves. Thirdly, the criteria for distinguishing scour and deposition patterns under irregular broken clapotis are presented.     

A New Probability of Detection Model for Updating Crack Distribution of Offshore Structures

1 .IntroductionNondestructiveinspection (NDI)isveryimportantforensuringthereliabilityofoffshorestructuresintheirservicelives (Lauraetal.,1 996 ) .Itiswellknownthatdetectionofflawsinvolvesconsider ablestatisticaluncertainties.Asaresult,theprobabilityofdetection (POD)forallflawsofagivensizehasbeenusedintheliteraturetodefinethecapabilityofaparticularNDItechniqueinagivenen vironment.SincethedataofPODusuallyscatterlargely ,itisdifficulttodeterminewhichmodelfitstheavailabledatabest.Thismodelun…     

Glaciomarine sedimentation and palaeo-glacial setting of Maxwell Bay and its tributary embayment, Marian Cove, South Shetland Islands, West Antarctica

High-resolution (3.5 kHz and multi-channel) seismic profiles and piston cores were collected from Maxwell Bay and its tributary embayment, Marian Cove, in the South Shetland Islands, Antarctica, during the Korea Antarctic Research Program (1992/93 and 1995/96) to elucidate the glaciomarine sedimentation processes and recent glacial history of the area. Seismic data from Maxwell Bay reveal a rugged bay margin and flattened basin floor covered with well-stratified hemipelagic muds. On the base-of-slope, acoustically transparent debris flows occur, indicating downslope resedimentation of glaciomarine sediments. Despite the subpolar and ice-proximal settings of Marian Cove, the seafloor is highly rugged with a thin sediment drape, suggesting that much of the area has been recently eroded by glaciers. Sediment cores from the cove penetrated three distinct fining-upward lithofacies: (1) basal till in the lower part of the core, accumulated just seaward of the grounding line of the tidewater glacier; (2) interlaminated sand and mud in the middle part, deposited in ice-proximal zone by a combination of episodic subglacial meltwater inflow and iceberg dumping; and (3) pebbly mud in the upper part, deposited in ice-distal zone by both surface meltwater plume and ice-rafting from the glacier front. A reconstruction of the glacial history of these areas since the late glacial maximum shows an ice sheet filling Maxwell Bay in late Wisconsin time and grounding of the tidewater glacier in Marian Cove until about 1300 yr BP.     

顶空气相色谱法测定海水二甲基硫和浮游植物细胞二甲基硫丙酸的研究

建立了顶空ＧＣ／ＦＰＤ测定海水中二甲基硫（ＤＭＳ）和浮游植物细胞中二甲基硫丙酸（ＤＭＳＰ）的方法，并研究盐度、温度、气液相比ＤＭＳ诸因素对ＤＭＳ顶空灵敏度的影响。该法对ＤＭＳ测定的相对标准偏差均小于６％，平均回收率为１０６％，最低检出限为２０ｎｇ／Ｌ。细胞ＤＭＳＰ先经碱作用转化为ＤＭＳ，在５０℃下作用时间不少于６ｈ，峰高与浓度的双对数线性相关系数大于０．９９。对１９９４年冬、１９９５年夏采自胶州湾     

养殖对虾病毒性疾病的细菌并发症防治研究

本文研究报道了发病对虾肝胰腺分离菌物敏感性，采用防台细菌人工感染方法进行药物饲料的筛选，在实验室及养殖池中进行药物饲料的防治效果试验。结果表明，在对虾病毒流行期间，采用药物饲料可有效防止对虾爆发性大量死亡，提高对虾存活率。