泰安台日本6.8级地震前体应变变化观测报告

2007年7月16日日本发生ML 6.8地震。此次地震前的7月6日,山东泰安台钻孔应变仪观测到异常变化。本文报告了变化情况,同时给出了水位和气压的变化。     

天然火山作用探测华北下地壳组成、结构及其形成过程

与中上地壳相比，对下地壳组成、结构的认识受限于样品的获取，然而天然火山作用携带的下地壳捕虏体可以为了解下地壳提供关键样品。华北克拉通是世界上最古老的克拉通之一，显生宙以来的火山作用携带有丰富的下地壳捕虏体，为探测华北下地壳组成、结构及其形成过程提供了可能。通过对这些捕虏体定深、定性及定年的综合研究，构建了以信阳，莒南，汉诺坝和女山等典型地区为代表的下地壳组成、结构剖面模型。这些剖面表明，华北克拉通下地壳具有分层的特点，且上老下新，暗示可能与底侵作用有关。其中捕虏体的锆石U- Pb年龄和Hf同位素的研究，揭示了该克拉通下地壳复杂的形成与演化过程：最古老的组成部分可能老至~4. 0 Ga冥古宙，此后经历了3. 80~3. 65 Ga古太古代的再造作用，2. 8~2. 5 Ga 新太古代和2. 3~1. 8 Ga 古元古代的增生与再造共存，同时还经历了显生宙以来包括462~220 Ma，140~90 Ma和47~45 Ma的增生与再造事件。     

中国湿地生态系统的外来入侵种研究

湿地是地球上各种生命形式高度聚集的生态体系之一,被称为“物种基因库”。湿地良好的环境条件不仅有利于本地种的生存,也利于外来物种的入侵。据现有资料统计,目前中国湿地生态系统中有外来入侵植物10种,隶属7个科;外来入侵动物53种,涉及哺乳类、鸟类、爬行类、两栖类、甲壳类、软体动物、鱼类和昆虫类。论述了这些入侵种的主要入侵途径,包括作为饲料、观赏、净化水质等目的人为有意引种,以及由非人为因素引起的入侵;同时还讨论了这些外来入侵种给湿地生态系统造成的不良影响,即导致物种多样性丧失、降低社会经济价值、破坏原有的生态系统和景观。     

Petrogenesis of Cretaceous adakitic and shoshonitic igneous rocks in the Luzong area, Anhui Province (eastern China): Implications for geodynamics and Cu–Au mineralization

Both adakitic and shoshonitic igneous rocks in the Luzong area, Anhui Province, eastern China are associated with Cretaceous Cu–Au mineralization. The Shaxi quartz diorite porphyrites exhibit adakite-like geochemical features, such as light rare earth element (LREE) enrichment, heavy REE (HREE) depletion, high Al₂O₃, MgO, Sr, Sr / Y and La / Yb values, and low Y and Yb contents. They have low ε_Nd(t) values (− 3.46 to − 6.28) and high (⁸⁷Sr / ⁸⁶Sr)_i ratios (0.7051–0.7057). Sensitive High-Resolution Ion Microprobe (SHRIMP) zircon analyses indicate a crystallization age of 136 ± 3 Ma for the adakitic rocks. Most volcanic rocks and the majority of monzonites and syenites in the Luzong area are K-rich (or shoshonitic) and were also produced during the Cretaceous (140–125 Ma). They are enriched in LREE and large-ion lithophile elements, and depleted in Ti, and Nb and Ba and exhibit relatively lower ε_Nd(t) values ranging from − 4.65 to − 7.03 and relatively higher (⁸⁷Sr / ⁸⁶Sr)_i ratios varying between 0.7057 and 0.7062. The shoshonitic and adakitic rocks in the Luzong area have similar Pb isotopic compositions (²⁰⁶Pb / ²⁰⁴Pb = 17.90–18.83, ²⁰⁷Pb / ²⁰⁴Pb = 15.45–15.62 and ²⁰⁸Pb / ²⁰⁴Pb = 38.07–38.80). Geological data from the Luzong area suggest that the Cretaceous igneous rocks are distributed along NE fault zones (e.g., Tanlu and Yangtze River fault zones) in eastern China and were likely formed in an extensional setting within the Yangtze Block. The Shaxi adakitic rocks were probably derived by the partial melting of delaminated lower crust at pressures equivalent to crustal thickness of > 50 km (i.e., 1.5 GPa), possibly leaving rutile-bearing eclogitic residue. The shoshonitic magmas, in contrast, originated mainly from an enriched mantle metasomatized by subducted oceanic sediments. They underwent early high-pressure (> 1.5 GPa) fractional crystallization at the boundary between thickened (> 50 km) lower crust and lithospheric mantle and late low-pressure (< 1.5 GPa) fractional crystallization in the shallow (< 50 km) crust. The adakitic and shoshonitic rocks appear to be linked to an intra-continental extensional setting where partial melting of enriched mantle and delaminated lower crust was probably controlled by lithospheric thinning and upwelling of hot asthenosphere along NE fault zones (e.g., Tanlu and Yangtze River fault zones) in eastern China. Both the shoshonitic and adakitic magmas were fertile with respect to Cu–Au mineralization.     

Characterization of water bursting and discharge into underground mines with multilayered groundwater flow systems in the North China coal basin

A conceptual framework for characterization of water bursting and discharge into underground mines with multilayered groundwater flow systems is presented, based on the features of the site conditions and analyses of the water bursting and mine inundation events of the North China coal basin. Comprehensive analyses of the hydrogeological conditions for establishment of the three-dimensional groundwater flow systems of the North China coal basin revealed different vertical hydraulic connection paths or channels. These connections include karst collapse columns, fault or fracture zones, buried weathering zones, and fracture networks in aquitards, within the multilayered groundwater flow systems. Also examined, was the effect of the primary features of the flow system and those different connection paths on water bursting and discharge into the underground coal mines. It was demonstrated that appropriately identifying and adequately understanding the three-dimensional multilayered groundwater flow systems and those various vertical hydraulic connection mechanisms are critical for appropriately preventing water bursting hazards and predicting water discharge into underground mines. A valuable guideline is presented on characterization of water bursting and discharge into underground mines with multilayered groundwater flow systems.

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Resumen Un cadre de travail conceptuel pour la caractérisation du jaillissement et de la vidange des eaux dans les mines à plusieurs niveaux d'écoulement est présenté, basé sur les conditions et l'analyse sur site du jaillissement des eaux et des inondations dans les bassins charbonneux du Nord de la Chine. L'analyse compréhensive des conditions hydrogéologiques des systèmes d'écoulement tridimensionnel de ces bassins, révèle des trajets ou des chenaux qui sont autant de connections hydrauliques verticales. Ces connections comprennent des effondrement karstiques en colonne, des zones de fractures et de failles, des zones d'altération, des réseaux de fractures dans les aquitards, dans le système hydrogéologique multicouche. L'influence des caractéristiques primaires du système d'écoulement et de ces différentes connections sur le jaillissement et la vidange dans les mines, est également examiné. Il a été démontré que l'identification appropriée et la compréhension adéquate du système d'écoulement souterrain multicouche et tridimensionnel, et des mécanismes variés de connection hydraulique verticale est critiquée pour prévenir de manière appropriée les risques de jaillissement et de vidange dans les mines. Des guidelines valorisables sont présentées, pour la caractérisation du jaillissement et de la vidange dans de tels systèmes.

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Résumé Se presenta un marco conceptual para la de caracterización de la despresurización y descarga de agua a minas subterráneas con sistemas de acuíferos de múltiples niveles, el cual se basa en las condiciones del sitio, análisis de la despresurización de agua e inundaciones de minas en la cuenca de carbón del norte de la China.Un análisis comprehensivo de las condiciones hidrogeológicas para el establecimiento de los sistemas de flujo de agua de tri-dimensionales en la cuenca de carbón del norte de la China ha revelado diferentes canales hidráulicos verticales. Estas conexiones incluyen columnas de karst colapsadas, fallas o zonas de fracturas, zonas de regalita hundida y redes de fracturas en zonas de poca permeabilidad dentro de los sistemas de flujo de múltiples niveles.También se investigó el efecto de los rasgos primarios del sistema de flujo y los diferentes canales conectivos sobre la despresurización y descarga de agua a minas subterráneas. Se demostró que el entendimiento e identificación adecuada de los sistemas de acuíferos de múltiples niveles en tres dimensiones es crítico para prevenir apropiadamente la despresurización y descarga de agua a minas subterráneas. Se presentan lineamientos valiosos en relación con la despresurización y descarga de agua a minas subterráneas en sistemas de flujo de múltiple nivel.

     

Palaeovariations in the East-Asian Monsoon Regime Geochemically Recorded in Varved Sediments of Lake Sihailongwan (Northeast China, Jilin Province). Part 1: Hydrological Conditions and Dust Flux

The varved sediments of the dimictic Lake Sihailongwan (Long Gang mountain area, Jilin Province, Northeast China) represent a palaeoclimatic archive which documents the local precipitation frequency during the summer monsoon, and variations in the aeolian flux of dust with their remote sources in the arid and semi-arid regions of inner Asia. Based on a detailed discussion of sediment genesis in Lake SHL, dust flux rates and palaeohydrological conditions were reconstructed on a decadal scale over the past 220 years. The aeolian influx by dry and wet deposition was quantified and characterised in its chemical composition. Photosynthetic production in the lake is positively correlated with the inflow of nutrient-rich groundwater. The groundwater discharge largely reflects the strength of the summer monsoon. Net accumulation rates for biogenic silica were determined for annually laminated sediments from the centre of the U-shaped lake basin based on sediment data. In a Si-balance model of the modern lake, the depositional flux of biogenic silica could be independently quantified on the base of hydrochemical monitoring data. Comparison of the both estimates allowed to asses the focussing of the particle flux in the lake. Though water retention in Lake SHL is rather high (ca. 30 years), changes in the hydrological conditions are sensitively recorded in the sediments because (i) nutrient-rich groundwater discharges into the productive zone of the lake, (ii) a substantial proportion of the total dissolved Si-inventory of the mixed lake (ca. 30%) is annually consumed by diatom growth, and (3) sediment accumulation is substantially focussed towards the flat bottom of the lake basin. The bulk siliciclastic sediment fraction (ca. 75 wt.%) largely originates from influx of dust of remote provenance. In sediment thin-sections, the dry-deposited dust fraction is microscopically identifiable as seasonal silt layer. Aeolian input by wet-deposition shows a distinctly higher variability than the influx of dust by dry-deposition. As diatom production, wet-deposition of dust is positively correlated with the rainfall during the summer monsoon. The inferred positive correlation between rainfall and dust flux during the summer monsoon implies that dust deposition is determined by the out-wash efficiency of mineral particles for a permanent high atmospheric dust concentration over Northeast China in the last 220 years.     

Diurnal Variations of Hydrochemistry in a Travertine-depositing Stream at Baishuitai, Yunnan, SW China

Diurnal variations of hydrochemistry were monitored at a spring and two pools in a travertine-depositing stream at Baishuitai, Yunnan, SW China. Water temperature, pH and specific conductivity were measured in intervals of 5 and 30 min for periods of 1 to 2 days. From these data the concentrations of Ca²⁺, HCO₃⁻, calcite saturation index, and CO₂ partial pressure were derived. The measurements in the spring of the stream did not show any diurnal variations in the chemical composition of the water. Diurnal variations, however, were observed in the water of the two travertine pools downstream. In one of them, a rise in temperature (thus more CO₂ degassing) during day time and consumption of CO₂ due to photosynthesis of submerged aquatic plants accelerated deposition of calcite, whereas in the other pool, where aquatic plants flourished and grew out of the water (so photosynthesis was taking place in the atmosphere), the authors suggest that temperature-dependent root respiration underwater took place, which dominated until noon. Consequently, due to the release of CO₂ by the root respiration into water, which dominated CO₂ production by degassing induced by temperature increase, the increased dissolution of calcite was observed. This is the first time anywhere at least in China that the effect of root respiration on diurnal hydrochemical variations has been observed. The finding has implications for sampling strategy within travertine-depositing streams and other similar environments with stagnant water bodies such as estuaries, lakes, reservoirs, pools and wetlands, where aquatic plants may flourish and grow out of water.     

西藏昌都镇地质灾害发育特征及防治对策

昌都镇位于澜沧江上游“三河一江”地带(即昂曲、扎曲、色曲、澜沧江)。地质构造条件复杂,气候较恶劣,昼夜温差大,物理风化强烈,植被稀疏,地质灾害发育。该区是藏东的政治、经济、文化中心。随着地区的经济发展,其城镇建设与地质灾害之间的矛盾日益突出。调查研究显示昌都镇发育地质灾害33处,其中崩塌16处,占灾害点总数48.5%,主要发育于路堑边坡和河流下切侧蚀形成的自然边坡;滑坡13处,占灾害点总数的39.4%,且90%为土质滑坡,多与人类工程活动有关;泥石流4处,占灾害点总数的12.1%,以中小型为主。文章总结了昌都镇崩塌、滑坡和泥石流灾害的发育分布特征,地质灾害与地层岩性、空间位置和人类工程活动等之间的关系,以及对昌都城镇建设和发展的影响。结合调查分析提出了昌都镇地质灾害防治的总体策略———治灾、设防、治水、治坡、生态建设和加强环保意识。     

库车坳陷侏罗系煤成气动力学模拟研究

应用黄金管—高压釜封闭体系热模拟实验与GC、GC-IRMS分析技术,结合KINETICS专用软件,对库车坳陷侏罗系煤成气进行了动力学模拟研究。库车坳陷侏罗系煤具有高的产气性,在高演化阶段主要产甲烷气;侏罗系煤热解气甲烷碳同位素为-36‰～-25‰,乙烷碳同位素为-28‰～-16‰;甲烷、C2-C5气态烃的生成活化能分别为(47～64k)calm/ol、(55～72k)calm/ol,频率因子各为5.265×1013s-1、5.388×1018s-1。在此基础上,进一步探讨了克拉2气田天然气的成因。研究认为,克拉2气田天然气属阶段捕获的煤成气,主要聚集了5～1Ma时期的天然气,其成熟度Ro分布范围为1.3%～2.5%。     

中国中新生代咸化湖盆烃源岩沉积的问题及相关进展

我国东部断陷湖盆和西部坳陷湖盆第三系均有蒸发岩与烃源岩共生现象。前者水体深、咸化范围小，在氯化盐和碳酸盐沉积环境中形成了优质烃源岩，后者水体浅、咸化范围大，在氯化盐和硫酸盐沉积环境中发育了优质烃源岩，作者认为两种湖盆出现的水体分层是有机质堆积和保存的重要条件。济阳坳陷和柴达木盆地为两类咸化湖盆的典型代表，对它们的研究可以深化蒸发岩-烃源岩共生区油气地质的认识、促进勘探发展。