下扬子天目山盆地火山岩锆石LA-ICP-MS定年及地质意义

天目山盆地是下扬子江南隆起带保存较完整的中生代火山盆地,中生代火山岩系岩性自下而上主要为流纹岩-英安岩-安山岩。对盆地内黄尖组下段流纹岩和英安岩分别进行了锆石 LA-ICP MS定年,分别获得了133．6±1．5 Ma（MSWD＝0．73）和135．0±2．1 Ma（MSWD＝0．78）的锆石U-Pb年龄,指示天目山盆地黄尖组火山岩时代为早白垩世。天目山盆地火山活动起始时间和长江中下游地区晚中生代火山活动基本一致,说明江南隆起带和长江中下游地区在早白垩世均处于强烈拉张环境。     

华南二叠系卡匹敦阶高分辨率浮点年代标尺

基于详细的生物地层学研究,以磁化率为古气候替代指标,对广西来宾铁桥剖面卡匹敦阶地层开展时间序列分析,建立高分辨率浮点年代标尺(FPTS).结果表明,磁化率记录了铁桥剖面中二叠世晚期沉积序列中的米兰科维奇旋回,卡匹敦阶上部磁化率突然增加与峨眉山玄武岩喷发和卡匹敦晚期全球性海退有关,这些事件导致同期沉积物中碎屑物质增加.铁桥剖面瓜德鲁普—乐平统界线附近磁化率和蓬莱滩剖面(乐平统底界GSSP)表现出一致的变化趋势,具可对比性.利用多窗谱法(MTM)和傅里叶变换(FT)从磁化率序列中识别出五个米兰科维奇周期:长偏心率周期(E2,405ka)、短偏心率周期(E1,100ka)、长地轴斜率周期(O2,44.1ka)、长岁差周期(P2,20.95ka)和短岁差周期(P1,17.7ka).对比基于E2周期建立的磁性地层磁化率(MSS)带和标准参考带(SRZ),建立整个沉积序列的高分辨率(200ka)FPTS,提出卡匹敦阶的时限为3.85 Ma(存在+0~0.28 Ma误差),整段沉积序列的平均沉积速率为2.91cm·ka-1.同时计算出卡匹敦阶内部七个牙形石带的时限,从最短26.6ka到最长2.3 Ma.另外,估算出峨眉山大火成岩省喷发启动时间为262.67 Ma,位于瓜德鲁普—乐平统界线之下1.42 Ma.     

桂东大瑶山成矿带花岗岩类岩石年代学格架的厘定

桂东大瑶山成矿带是指与侵入于大瑶山地区寒武纪浅变质岩系中的岩浆岩有关、呈近EW向展布的金-多金属成矿带。成矿带内花岗岩类岩浆活动强烈,多呈岩株、岩脉和岩筒状产出,主要岩性为花岗闪长岩、花岗斑岩、二长花岗岩和花岗闪长斑岩。笔者报道了成矿带内的大王顶岩体、大岸岩体、古龙岩体、大村岩体、社山复式岩体和思委岩体的LA-ICP-MS定年结果,并结合前人对大瑶山成矿带内花岗岩类的研究成果,建立了大瑶山成矿带花岗岩类的年代学格架。结果显示,大瑶山成矿带花岗岩类主要形成于加里东期(444.8±2.5) Ma和燕山晚期晚白垩世(96.6±1.1) Ma,燕山早期侏罗纪次之(164.2±2.8) Ma,且花岗岩类岩体侵位年龄与金-多金属矿床的成矿时代具有良好的对应关系。     

芦山地震、汶川地震与龙门山地区水汽异常

对龙门山地区水汽动态的分析研究表明,在2013年芦山MS7.0地震和2008年汶川MS8.0地震前,龙门山地区大气相对湿度异常频次都出现了先逐年下降,然后快速回升的过程;下降时间较长,10a以上,上升时间较短,1~2a;震中位于异常频次相对下降和上升幅度都是最大的中心或邻近区域。在地震孕育中期阶段发生水汽异常趋势变化的原因可能是由于岩层裂隙的张合、地下流体的运动和地热能的变化,影响地面温度和潜热交换的速度所致。在地震孕育的中长期阶段(10a~几a),地壳岩石受压缩变形,孔隙、裂隙不断闭合或减少,由地下释放的热水、热汽减少,潜热交换速度也随之降低,相对湿度异常频次表现为逐年下降的趋势。在地震孕育的中短期阶段,地壳岩石变形进一步加大,可能导致微破裂不断扩展,由地下释放的热水、热汽由减少转为增加,潜热交换速度由降低转为迅速增加,相对湿度异常频度也表现出由逐年下降转为突发的快速上升。     

大凉山次级块体内强震发生的构造特征与2014年鲁甸6.5级地震对周边断层的影响

2014年8月3日,在云南鲁甸发生MS6.5地震.该地震位于巴颜喀拉块体、川滇块体与华南块体三者之间的以挤压和左旋走滑为主要活动特征的大凉山次级块体内部.该次级块体吸收了来自川滇块体和巴颜喀拉块体的挤压作用,主要以各边界断裂带的挤压作用和内部大凉山断裂带、峨边断裂带等NNW向的左旋走滑次级断裂为主要特征;在历史上大凉山次级块体边界上以7级以上强震活动为主要特征,而在次级块体内部则以5级地震频繁活动为主.2014年鲁甸MS6.5地震发生在逆冲走滑断裂带内部的NNW向左旋走滑断裂上,该地震主要受到了发生在小江断裂带上的1733年M73/4和则木河断裂带上的1850年M71/2强震的影响,这两次地震对2014年鲁甸MS6.5地震有促进作用,而2014年鲁甸6.5级地震促进了2014年10月1日越西5.0级地震的发生,此外鲁甸地震对大凉山断裂带北段、峨边断裂带、昭通-鲁甸断裂带东段以及则木河断裂带南段有一定的库仑应力增强作用.     

CCD and photon-counting photometric observations of asteroids carried out at Padova and Catania observatories

We present the results of observational campaigns of asteroids performed at Asiago Station of Padova Astronomical Observatory and at M.G. Fracastoro Station of Catania Astrophysical Observatory, as part of the large research programme on Solar System minor bodies undertaken since 1979 at the Physics and Astronomy Department of Catania University. Photometric observations of six Main-Belt asteroids (27 Euterpe, 173 Ino, 182 Elsa, 539 Pamina, 849 Ara, and 984 Gretia), one Hungaria (1727 Mette), and two Near-Earth Objects (3199 Nefertiti and 2004 UE) are reported. The first determination of the synodic rotational period of 2004 UE was obtained. For 182 Elsa and 1727 Mette the derived synodic period of 80.23±0.08 and , respectively, represents a significant improvement on the previously published values. For 182 Elsa the first determination of the H-G magnitude relation is also presented.     

X-ray and strong lensing mass estimate of MS2137.3–2353

We present new mass estimates of the cluster of galaxies MS2137.3–2353, inferred from X-ray and strong lensing analyses. This cluster exhibits an outstanding strong lensing configuration and indicates a well-relaxed dynamical state, being most suitable for a mass reconstruction which combines both techniques. Despite this, several previous studies have claimed a significant discrepancy between the X-ray and the strong lensing mass estimates. The primary aim of this paper is to address and explain this mismatch. For this purpose, we have analysed Chandra observations to recover the profiles of the intracluster medium properties and, assuming a functional form for the matter density, the total mass distribution. The notable strong-lensing features of MS2137.3 allow us to reconstruct its projected mass in the central regions with good accuracy, by taking advantage of the lensing inversion code lenstool . We compare the results obtained for both methods. Our mass estimates for MS2137.3 are in agreement within errors, leading to a mean, extrapolated value of   M ₂₀₀≃ 4.4 ± 0.3 × 10¹⁴ M_⊙  , under the assumption of the Navarro–Frenk–White (NFW) mass profile. However, the strong lensing mass estimate is affected by the details of the brightest cluster galaxy mass modelling, since the radial arc is a very sensitive probe of the total mass derivative in the central region. In particular, we do not find evidence for a high concentration for the NFW density profile, as reported in some earlier works.     

Changes in temperature extremes based on a 6-hourly dataset in China from 1961–2005

Changes in Chinese temperature extremes are presented based on a six-hourly surface air temperature dataset for the period 1961--2005. These temperature series are manually observed at 0200, 0800, 1400, and 2000 Beijing Time (LST), and percentile based extreme indices of these time series are chosen for analysis. Although there is a difference in time among the different time zones across China, as more than 80% of the stations are located in two adjacent time zones, these indices for all the stations are called warm (cold) nights (0200 LST), warm (cold) mornings (0800 LST), warm (cold) days (1400 LST), and warm (cold) evenings (2000 LST), respectively for convenience. The frequency of the annual warm extremes has generally increased, while the frequency of the annual cold extremes has decreased, and significant changes are mainly observed in northern China, the Tibetan Plateau, and the southernmost part of China. Based on the national average, annual warm (cold) nights increase (decrease) at a rate of 5.66 (-5.92) d (10 yr)^-1, annual warm (cold) days increase (decrease) at a rate of 3.97 (-2.98) d (10 yr)^-1, and the trends for the annual warm (cold) mornings and evenings are 4.35 (-4.96) and 5.95 (-4.35) d (10 yr)^-1, respectively. For China as a whole, the increasing rates for the occurrence of seasonal warm extremes are larger in the nighttime (0200, 2000 LST) than these in the daytime (0800, 1400 LST), the maximal increase occurs at 2000 LST except in the summer and the minimal increase occurs at 1400 LST except in autumn; the maximal decrease in the occurrence of seasonal cold extremes occurs at 0200 LST and the minimal decrease occurs at 1400 LST.     

汶川M_S8.0地震河谷地形对汉源县城高烈度异常的影响

汉源县城位于汶川M_S8.0特大地震六度区内唯一的八度异常区,为典型且罕见的远震高烈度异常区.汉源县城处于流沙河的河流阶地之上,河谷地形对地震震害有显著的影响.为定量分析河谷地形对汶川大地震汉源县高烈度异常的影响,基于汉源县城震害科学考察和场地勘察获取的资料,根据震害分布特征和流沙河谷地形的特点,选取1条实测得到的横切汉源县城并垂直流沙河河谷方向的典型剖面作为计算模型,以脉冲作为基底输入,采用有限差分方法研究了该剖面的场地放大效应,分析了地形对高烈度异常的影响.计算结果表明:汉源县城场地对地震动放大效应的显著频段是1.0~10Hz,且这一频段老县城场地的放大效应比新县城场地显著;汉源老县城场地对汶川M_S8.0地震主震的地震动有显著的放大效应,地表峰值加速度大大超过了抗震设计规范的规定值;汉源场地地形放大效应显著频段与汶川M_S8.0地震的能量集中频段基本吻合,汉源老县城建筑物的自振频率恰恰位于该频段,产生共振效应,从而造成更显著的放大效应,这也是汉源震害异常的主要原因之一.由此可见,河谷地形对地表地震动有重要的影响,在工程选址和抗震设计时应考虑其影响.