川东北地区长兴组-飞仙关组固体沥青的形貌特征与成因分析

利用扫描电镜观察川东北某地区上二叠统、下三叠统储层固体沥青时,发现固体沥青与显微镜下的无定形、它形充填构造不同,按其外形可分为皮壳状、葡萄状、瘤状、蠕虫状和柿饼状5种类型。其中皮壳状、葡萄状沥青分布在飞仙关组,瘤状、蠕虫状和柿饼状沥青分布在长兴组。根据固体沥青内部鳞片状结构和球粒中间相结构推测其已达高演化阶段。     

Preliminary Evidence for Iodate Reduction in Bottom Waters of the Gulf of Mexico During an Hypoxic Event

The distributions of iodate and total inorganic iodine concentrations in the waters on the Texas?CLouisiana shelf in April, June, and August 2004 are described. Iodine?Csalinity graphs show three-end-member mixing involving onshore and offshore surface waters and deep offshore water. The April survey showed simple mixing on the surface, but in the later surveys, iodate concentrations were often much lower than predicted by the mixing curve while those for total inorganic iodine were higher. This demonstrated both iodate reduction in the water and iodide addition, although individual samples did not show equivalent speciation changes. Hydrographically, the system consists of the estuaries of the Mississippi and Atchafalaya rivers as they spill onto the shelf. The waters are stratified seasonally by a robust halocline, leading to hypoxia in the bottom waters from the combined effect of restricted downward diffusion of oxygen and the sinking of the luxuriant growth of phytoplankton induced by riverine nutrient supply. The distributions of iodate and total inorganic iodine are, therefore, interpreted in terms of water?Csediment interaction as the shelf shoals to the north.     

First observations of jelly-falls at the seafloor in a deep-sea fjord

Faunal communities at the deep-sea floor mainly rely on the downward transport of particulate organic material for energy, which can come in many forms, ranging from phytodetritus to whale carcasses. Recently, studies have shown that the deep-sea floor may also be subsidized by fluxes of gelatinous material to the benthos. The deep-sea scyphozoan medusa Periphylla periphylla is common in many deep-sea fjords in Norway and recent investigations in Lurefjorden in western Norway suggest that the biomass of this jellyfish currently exceeds 50000 t here. To quantify the presence of dead P. periphylla jellyfish falls (hereafter termed jelly-falls) at the deep seafloor and the standing stock of carbon (C) and nitrogen (N) deposited on the seafloor by this species, we made photographic transects of the seafloor, using a ‘Yo-Yo’ camera system during an opportunistic sampling campaign in March 2011. Of 218 seafloor photographs taken, jelly-falls were present in five, which resulted in a total jelly-fall abundance of 1×10^-2 jelly-falls m⁻² over the entire area surveyed. Summed over the entire area of seafloor photographed, 1×10^-2 jelly-falls m⁻² was equivalent to a C- and N-biomass of 13 mg C m⁻² and 2 mg N m⁻². The contribution of each jelly-fall to the C- and N-amount of the sediment in the immediate vicinity of each fall (i.e. to sediment in each 3.02 m² image in which jelly-falls were observed) was estimated to be 568±84 mg C m⁻² and 88±13 mg N m⁻². The only megafaunal taxon observed around or on top of the jelly-falls was caridean shrimp (14±5 individuals jelly-fall⁻¹), and shrimp abundance was significantly greater in photographs in which a jelly-fall was found (14±5 individuals image⁻¹) compared to photographs in which no jelly-falls were observed (1.4±0.7 individuals image⁻¹). These observations indicate that jelly-falls in this fjord can enhance the sedimentary C- and N-amount at the deep-sea floor and may provide nutrition to benthic and demersal faunas in this environment. However, organic enrichment from the jelly-falls found in this single sampling event and associated disturbance was highly localized.     

基于遥感数据的温度剖面预报研究

为了提高温度剖面的预报精度,提出了一种基于遥感数据的温度剖面预报方法.文中使用27个实测温度剖面和遥感SST、SSHA数据实现了对温度剖面的预报,并用该点的ARGO数据进行了检验.实验结果表明,将遥感数据同化到温度剖面的预报中是可行的,并能有效的提高温度剖面的预报精度.     

A concept for providing warning of earth impacts by small asteroids

The atmospheric detonation of a 17 m-asteroid above Chelyabinsk, Russia on 2013 February 15 shows that even small asteroids can cause extensive damage. Earth-based telescopes have found smaller harmless objects, such as 2008 TC3, a 4 m-asteroid that was discovered 20h before it exploded over northeastern Sudan (Jenniskens, 2009). 2008 TC3 remains the only asteroid discovered before it hit Earth because it approached Earth from the night side, where it was observed by large telescopes searching for near-Earth objects (NEO’s). The larger object that exploded over Chelyabinsk approached Earth from the day side, from too close to the Sun to be detected from Earth. A sizeable telescope in an orbit about the Sun-Earth L1 (SE-L1) libration point could find objects like the “Chelyabinsk” asteroid approaching approximately from the line of sight to the Sun about a day before Earth closest approach. Such a system would have the astrometric accuracy needed to determine the time and impact zone for a NEO on a collision course. This would give at least several hours, and usually 2–4 days, to take protective measures, rather than the approximately two-minute interval between the flash and shock wave arrival that occurred in Chelyabinsk. A perhaps even more important reason for providing warning of these events, even smaller harmless ones that explode high in the atmosphere with the force of an atomic bomb, is to prevent mistaking such an event for a nuclear attack that could trigger a devastating nuclear war. A concept using a space telescope similar to that needed for an SE-L1 monitoring satellite, is already conceived by the B612 Foundation, whose planned Sentinel Space Telescope could find nearly all 140 m and larger NEO’s, including those in orbits mostly inside the Earth’s orbit that are hard to find with Earth-based telescopes, from a Venus-like orbit (Lu, 2013). Few modifications would be needed to the Sentinel Space Telescope to operate in a SE-L1 orbit, 0.01 AU from Earth towards the Sun, to find most asteroids larger than about 5 meters that approach the Earth from the solar direction. The spacecraft would scan 165 square degrees of the sky around the Earth every hour, finding asteroids when they are brightest (small phase angle) as they approach Earth. We will undertake Monte Carlo studies to see what fraction of asteroids 5 m and larger approaching from the Sun might be found by such a mission, and how much warning time might typically be expected. Also, we will check the overall coverage for all Earth-approaching NEO’s, including ground-based observations and observations by the recently-launched NEOSSat, which may best fill any gaps in coverage between that provided by an SE-L1 telescope and ground-based surveys. Many of the objects as large as 50 m, like the one that created Meteor Crater in Arizona, will not be found by current NEO surveys, while they would usually be seen by this possible mission even if they approached from the direction of the Sun. We should give better warning for future “Bolts out of the blue.”     

Quantifying volcanic ash fall hazard to electricity infrastructure

Quantifying the potential ash fall hazards from re-awakening volcanoes is a topic of great interest. While methods for calculating the probability of eruptions, and for numerical simulation of tephra dispersal and fallout exist, event records at most volcanoes that re-awaken sporadically on decadal to millennial cycles are inadequate to develop rigorous forecasts of occurrence, much less eruptive volume. Here we demonstrate a method by which eruption records from radiocarbon-dated sediment cores can be used to derive forecasting models for ash fall impacts on electrical infrastructure. Our method is illustrated by an example from the Taranaki region of New Zealand. Radiocarbon dates, expressed as years before present (B.P.), are used to define an age-depth model, classifying eruption ages (with associated errors) for a circa 1500–10 500 year B.P. record at Mt. Taranaki (New Zealand). In addition, data describing the youngest 1500 years of eruption activity is obtained from directly dated proximal deposits. Absence of trend and apparent independence in eruption intervals is consistent with a renewal model using a mix of Weibulls distributions, which was used to generate probabilistic forecasts of eruption recurrence. After establishing that interval length and tephra thickness were independent in the record, a thickness–volume relationship (from [Rhoades, D.A., Dowrick, D.J., Wilson, C.J.N., 2002. Volcanic hazard in New Zealand: Scaling and attenuation relations for tephra fall deposits from Taupo volcano. Nat. Hazards, 26:147–174]) was inverted to provide a frequency–volume relationship for eruptions. Monte Carlo simulation of the thickness–volume relationship was then used to produce probable ash fall thicknesses at any chosen site. Several critical electrical infrastructure sites in the Taranaki Region were analysed. This region, being the only gas and condensate-producing area in New Zealand, is of national economic importance, with activities in and around the area depending on uninterrupted power supplies. Forecasts of critical ash thicknesses (1 mm wet and 2 mm dry) that may cause short-circuiting, surges or power shutdowns in substations show that the annual probabilities of serious impact are between ~ 0.5% and 27% over a 50 year period. It was also found that while large eruptions with high ash plumes tend to affect “expected” areas in relation to prevailing winds, the direction impacts of small ash falls are far less predictable. In the Taranaki case study, areas out of normal downwind directions, but close to the volcano, have probabilities of impact for critical thicknesses of 1–2 mm of around half to 60% of those in downwind directions and therefore should not be overlooked in hazard analysis. Through this method we are able to definitively show that the potential ash fall hazard to electrical infrastructure in this area is low in comparison to other natural threats, and provide a quantitative measure for use in risk analysis and budget prioritisation for hazard mitigation measures.     

Petrogenesis and tectonic setting of bimodal volcanism in the Sakoli Mobile Belt, Central Indian shield

The Sakoli Mobile Belt comprises bimodal volcanic rocks that include metabasalt, rhyolite, tuffs, and epiclastic rocks with metapelites, quartzite, arkose, conglomerate, and banded iron formation (BIF). Mafic volcanic rocks are tholeiitic to quartz‐tholeiitic with normative quartz and hypersthene. SiO₂ shows a large compositional gap between the basic and acidic volcanics, depicting their bimodal nature. Both the volcanics have distinct geochemical trends but display some similarity in terms of enriched light rare earth element–large ion lithophile element characteristics with positive anomalies for U, Pb, and Th and distinct negative anomalies for Nb, P, and Ti. These characteristics are typical of continental rift volcanism. Both the volcanic rocks show strong negative Sr and Eu anomalies indicating fractionation of plagioclases and K‐feldspars, respectively. The high Fe/Mg ratios for the basic rocks indicate their evolved nature. Whole rock Sm–Nd isochrons for the acidic volcanic rocks indicate an age of crystallization for these volcanic rocks at about 1675 ± 180 Ma (initial ¹⁴³Nd/¹⁴⁴Nd = 0.51017 ± 0.00017, mean square weighted deviate [MSWD] = 1.6). The εNd_t (t = 2000 Ma) varies between ?0.19 and +2.22 for the basic volcanic rock and between ?2.85 and ?4.29 for the acidic volcanic rocks. Depleted mantle model ages vary from 2000 to 2275 Ma for the basic and from 2426 to 2777 Ma for the acidic volcanic rocks, respectively. These model ages indicate that protoliths for the acidic volcanic rocks probably had a much longer crustal residence time. Predominantly basaltic magma erupted during the deposition of the Dhabetekri Formation and part of it pooled at crustal or shallower subcrustal levels that probably triggered partial melting to generate the acidic magma. The influence of basic magma on the genesis of acidic magma is indicated by the higher Ni and Cr abundance at the observed silica levels of the acidic magma. A subsequent pulse of basic magma, which became crustally contaminated, erupted as minor component along with the dominantly acidic volcanics during the deposition of the Bhiwapur Formation.     

合欢树地震观测与试验研究项目通过验收

中国地震局地震科学联合基金会办公室于 1999年 10月 19日至 2 0日在山西省太原市太原钢铁 (集团 )有限公司地震台召开了合欢树地震观测与试验研究课题验收会。验收组听取了课题组关于合欢树地震观测与试验的研究报告 ,查看了观测现场 ,观测仪器、设备及观测环境 ,查阅了观测资料、图件 ,及山西省科学技术情报研究所出具的科技查新检索报告 ,并对有关问题进行了询问 ,验收组经过认真的评议讨论 ,认为 :利用合欢树生物电位进行地震短临观测、探索 ,在国内属首次进行 ,具有新颖性、实用性 ,课题组重点观测、研究的不同树种、不同树龄、不同传…