Characteristics of rapid giant landslides in China

Factual data for 70 rapid, giant landslides since 1900 show that the occurrence of these landslides was largely predisposed by tectonics, geological structures, lithology and topography, and often triggered by rainfall and earthquakes. In terms of mobile behavior, the giant landslides can be classified into three types: slides, slide-flows and flows. It is found that each type of landslide was constrained to certain geologic and topographic regimes. There are good correlations between kinematic parameters of landslides and slope geometries, which confirm the important role played by topographical condition in the mobile behavior of landslides. Moreover, it is also found that each type of landslide presents distinct geotechnical characteristics in terms of nature of the slip zone and properties of sliding mass. Brief analyses of five typical cases illustrate that landslide mechanisms can be conceptually depicted by failure mechanisms of their slip zones prior to onset of movement and following energy conversion during movement. Problems and questions related to experience in China suggest that comprehensive and systematic investigation and study on rapid giant landslides are urgently needed.     

Chevron Ridges and Runup Deposits in the Bahamas from Storms Late in Oxygen-Isotope Substage 5e

Landward-pointing V-shaped sand ridges several kilometers long are common along the windward margin of the Bahama Islands. Their axes share a northeast–southwest trend. Internally, the ridges contain low-angle oolitic beds with few erosional truncations. Commonly interbedded are tabular, fenestrae-rich beds such as those formed by the sheet flow of water over dry sand. Defined here as “chevron ridges,” these landforms appear to have originated in the rapid remobilization of bank margin ooid bodies by the action of long-period waves from a northeasterly source. Deposits along adjacent coastlines also preserve evidence of the impact of large waves. Reworked eolian sand bodies preserve beach fenestrae and hydraulic scour traces up to +40 m on older ridges. On cliffed coasts, 1000-ton boulders have been thrown well inland, recording the impact of large waves. Amino acid ratios confirm a correlation of the ridges across the archipelago, while stratigraphy, spacing, and cross-cutting relationships indicate emplacement as sea level fell rapidly from the substage 5e maximum at or above +6 m.     

联合古陆演化周期中超大型含煤及含油气盆地的形成

联合古陆———Ｐａｎｇｅａ的拼合与裂解反映了地球系统内部的巨大变革，这一过程根本上改变了浅部圈层的构造和环境。地史上超大型含煤盆地及含油气盆地与Ｐａｎｇｅａ的演化周期密切相关。在石炭纪及二叠纪拼合过程中形成了一系列超大型聚煤盆地；晚侏罗世Ｐａｎｇｅａ开始裂解，出现全球性裂陷作用期，大西洋张开，许多与裂陷有关的大型叠合盆地形成。在这些盆地中已发现十余个与晚侏罗世烃源岩有关的巨型含油气系统。上述情况表明Ｐａｎｇｅａ演化过程中出现了对能源资源聚集极为有利的古构造、古环境和古气候条件。     

3. Solar System Formation and Early Evolution: the First 100 Million Years

The solar system, as we know it today, is about 4.5 billion years old. It is widely believed that it was essentially completed 100 million years after the formation of the Sun, which itself took less than 1 million years, although the exact chronology remains highly uncertain. For instance: which, of the giant planets or the terrestrial planets, formed first, and how? How did they acquire their mass? What was the early evolution of the “primitive solar nebula” (solar nebula for short)? What is its relation with the circumstellar disks that are ubiquitous around young low-mass stars today? Is it possible to define a “time zero” (t ₀), the epoch of the formation of the solar system? Is the solar system exceptional or common? This astronomical chapter focuses on the early stages, which determine in large part the subsequent evolution of the proto-solar system. This evolution is logarithmic, being very fast initially, then gradually slowing down. The chapter is thus divided in three parts: (1) The first million years: the stellar era. The dominant phase is the formation of the Sun in a stellar cluster, via accretion of material from a circumstellar disk, itself fed by a progressively vanishing circumstellar envelope. (2) The first 10 million years: the disk era. The dominant phase is the evolution and progressive disappearance of circumstellar disks around evolved young stars; planets will start to form at this stage. Important constraints on the solar nebula and on planet formation are drawn from the most primitive objects in the solar system, i.e., meteorites. (3) The first 100 million years: the “telluric” era. This phase is dominated by terrestrial (rocky) planet formation and differentiation, and the appearance of oceans and atmospheres.     

Weed preference and growth of young grass carp in New Zealand

In each of eight 5‐day pond experiments carried out at intervals over a year, 0+ to 1 +‐year‐old grass carp, Ctenopharyngodon idella Val., were offered a choice of at least 10 species of water weeds from the Rotorua area. Water temperature was measured each day. Food selectivity decreased with increasing temperature and size of fish, but preference for the weeds did not change. At summer temperatures the fish ate much weed and grew at about 4g/fish/day, but in winter little food was taken and growth was slow.     

O-rich SR and Mira variables in DENIS

Previous VLA observations of the triple radio continuum source in Serpens showed that it has very unusual and extraordinary characteristics. While this source is associated with a star forming region, its outer components exhibit a combination of thermal and nonthermal spectra and large proper motions, Furthermore, the NW lobe has knotty and extended emission connecting the central source with the bright outer knot. Here, we present results of new VLA radio continuum high-angular resolution observations of this Radio Jet. Combining these observations with those obtained previously, we find that: a) one of the knots along the main body of the radio jet (knot G) exhibits proper motions similar to those observed in the outer NW and SE components, and the time variable knot A; b) the outer knots are moving away from the central source in slightly different directions; and c) the orientation of the central source seems to change with time. These results are consistent with a central precessing source that undergoes periodic ejection of material.     

西藏知不拉和浪母家果矽卡岩铜矿地质特征及驱龙-知不拉-浪母家果成矿系统的确定

西藏驱龙巨型斑岩铜钼矿床周围产出有知不拉与浪母家果矽卡岩铜矿。通过揭示知不拉和浪母家果的地质特征、成矿侵入体的地球化学特征和硫同位素特征,结合前人的年代学资料,确立两者与驱龙斑岩铜矿共同构成斑岩-矽卡岩成矿系统。结果显示知不拉与浪母家果矽卡岩矿床中的侵入岩地球化学特征与驱龙矿区的侵入岩地球化学特征相似,属于准铝质、钙碱性-高钾钙碱性岩石;稀土元素表现为强烈的LREE和HREE的分异,除知不拉的细晶岩有很强的Eu负异常,其他具有很弱的Eu负异常;明显富集大离子亲石元素(LILE)和高场强元素(HFSE),K、Pb的正异常,Ta、Nb、Ti的负异常。知不拉硫化物硫同位素与驱龙斑岩铜钼矿的硫同位素相比有明显的差异,这样的差异可能是由于成矿热液氧逸度的变化和晚期高δ34S值的天水加入造成的。研究确立驱龙-知不拉-浪母家果斑岩-矽卡岩成矿系统,主要基于:时代相近,空间毗邻;驱龙斑岩铜矿花岗闪长岩接触带发育有明显矽卡岩矿化;与矿化有关的侵入岩地球化学特征相似性;成矿物质演化趋势相似;矽卡岩连续演化的物理化学条件。而钙质围岩、多期次侵位且侵位较浅的岩浆与区域内构造活动及矿区内断裂、裂隙发育,共同决定了斑岩-矽卡岩系统的产出。     

河南东沟钼矿花岗斑岩成因: 岩石地球化学、锆石U-Pb年代学及Sr-Nd-Hf同位素制约

本研究对东沟超大型钼矿床的成矿母岩-东沟花岗斑岩开展了系统的年代学、岩石地球化学及Sr-Nd-Hf同位素分析工作.LA-ICP-MS锆石U-Pb定年结果表明,东沟花岗斑岩成岩年龄为114～117Ma,与已有的成矿年龄(116±2Ma,Re-Os法)一致,证实了东沟钼矿为一斑岩型矿床.详细的岩石地球化学分析显示东沟花岗斑岩岩体与区域上太山庙大型花岗岩基为同源演化关系,它们均为弱过铝质,具有富Si、富K、富Rb、Th、U等大离子亲石元素、富Nb、Ta、Zr、Hf等高场强元素,贫Fe、Mg、Ca,贫Sr、Ba,Ga/Al比值较高等地球化学特征,属铝质A型花岗岩,形成于伸展构造体制,东沟岩体是母岩浆经历了强烈结晶分异高度演化的产物;东沟岩体Nd同位素组成为0.51166～0.51182,ε_(Nd)(t))值在-17.3～-14.3之间,锆石的ε_(Hf)(t)值变化较大,由-3.4至-18.7,另有一颗年龄为1715Ma的捕获锆石的ε_(Hf)(t)值为-2.4,Nd、Hf模式年龄分别为1.5～1.8Ga与1.3～1.7Ga.我们认为东沟岩体的岩浆源区以古老地壳物质为主,但也有少量幔源组分参入,并且幔源物质的加入及很高的岩浆演化程度可能对东沟钼矿的成岩成矿过程具有重要作用.     

Analysis of microsecond- and submicrosecond-scale electric field pulses produced by cloud and ground lightning discharges

We examined microsecond- and submicrosecond-scale pulses in electric field records of cloud and cloud-to-ground lightning discharges acquired in summer 2006, in Gainesville, Florida. A total of 12 cloud and 12 ground flashes were analyzed in detail, with the electric field record length being 96 or 200 ms and sampling interval being 4 or 10 ns. The majority of pulses in both cloud and ground discharges analyzed in this study were associated with the initial breakdown process and were relatively small in amplitude and duration. The typical durations were an order of magnitude smaller than tens of microseconds characteristic of “classical” preliminary breakdown pulses. We estimated that 26% of the pulses in the 12 cloud discharges and 22% of the pulses in the 12 cloud-to-ground discharges had total durations less that 1 µs.