Paleoproterozoic Potassic Granitoids in the Sushui Complex from the Zhongtiao Mountains, Northern China： Geochronology, Geochemistry and Petrogenesis

1 Introduction The early Precambrian basement of the North China Craton (NCC) consists mainly of the Eastern Continental Block, the Western Continental Block and the Trans-North China Orogen (TNCO, or “the Central Tectonic Zone”), which formed by continental collision between the Eastern and Western Blocks (Zhao et al., 1998). This evolutionary model has now been widely accepted (Wu and Zhong, 1998; Guan et al., 2002; Guo et al., 2002; Liu et al., 2002a, b; Liu et al., 2004a, b;…     

The Liaonan Metamorphic Core Complex： Constitution, Structure and Evolution

The Liaonan metamorphic core complex (mcc) has a three-layer structure and is constituted by five parts, i.e. a detachment fault zone, an allochthonous upper plate and an supradetachment basin above the fault zone, and highly metamorphosed rocks and intrusive rocks in the lower plate. The allochthonous upper plate is mainly of Neoproterozoic and Paleozoic rocks weakly deformed and metamorphosed in pre-Indosinan stage. Above these rocks is a small-scale supradetachment basin of Cretaceous sedimentary and volcanic rocks. The lower plate is dominated by Archean TTG gneisses with minor amount of supracrustal rocks. The Archean rocks are intruded by late Mesozoic synkinematic monzogranitic and granitic plutons. Different types of fault rocks, providing clues to the evolution of the detachment fault zone, are well-preserved in the fault zone, e.g. mylonitic gneiss, mylonites, brecciated mylonites, microbreccias and pseudotachylites. Lineations in lower plate granitic intrusions have consistent orientation that indicate uniform top-to-NW shearing along the main detachment fault zone. This also provides evidence for the synkinematic characteristics of the granitic plutons in the lower plate. Structural analysis of the different parts in the mcc and isotopic dating of plutonic rocks from the lower plate and mylonitic rocks from detachment fault zone suggest that exhumation of the mcc started with regional crustal extension due to crustal block rotation and tangential shearing. The extension triggered magma formation, upwelling and emplacement. This event ended with appearance of pseudotachylite and fault gauges formed at the uppermost crustal level. U-Pb dating of single zircon grains from granitic rocks in the lower plate gives an age of 130±5 Ma, and biotite grains from the mam detachment fault zone have 40Ar-39Ar ages of 108-119 Ma. Several aspects may provide constraints for the exhumation of the Liaonan mcc. These include regional extensional setting, cover/basement contact, temporal and spatial coupling of extension and magmatism, basin development and evolution of fault tectonites along detachment fault zone. We propose that the exhumation of the Liaonan mcc resulted from regional extension and thinning of crust or lithosphere in eastern North China, and accompanied with synkinematic intrusion of granitic plutons, formation of detachment fault zone, uplifting and exhumation of lower-plate rocks, and appearance of supradetachment basin.     

丽江高美古的天文观测条件

综述对丽江高美古的视宁度、天光亮度、消光系数进行观测的原理、仪器、观测方法和结果．结果表明,高美古是我国南方的优良光学天文台址,视宁度达到世界优良台址的水平     

1999年山西大同-阳高5.6级地震灾害损失评估

１９９９年１１月１日在山西省大同县和阳高县间发生Ｍｓ５．６地震,通过野外调查,对这次地震灾害损失进行了评估。评估结果表明,这次地震受灾面积达３２４ｋｍ＾２,主要受灾村５６个,重伤１０人,轻伤６０人,总经济损失为１４０２３万元。指出灾区所有房屋经历了１９８９年、１９９１年１次或２次中强地震的破坏,抗震能力明显降低是这次震害较生的主要原因。并针对这次震害的特征,提出防御与减轻震害的经验、教训及有关建议     

中国大陆科学钻探工程简介

随着航天技术的发展开辟了人类通往宇宙星际的大门,一个与之相呼应的“入地“计划应运而生,这就是直接观测地球陆壳的“大陆科学钻探”。作为伸入地球内部的“望远镜”,大陆科学深钻是当代地球科学具有划时代意义的大科学工程,是解决当代人类面临的资源、灾害和环境等重大问题的重要途径之一。 由于大陆科学钻探对当代经济、社会发展和科学进步具有重大意义,自70年代以来,俄、德、法、日、美和英等国家实施了大陆钻探,取得令人瞩目的科学研究成果,并带动了钻探和相关科学技术的大发展。     

Oceanographic conditions on the Weddell Sea Shelf during the German Antarctic Expedition 1979/80

Hydrographic (CTD), current and water level measurements obtained in the vicinity of the floating Ronne and Filchner Ice Shelves are presented. The distribution of Western Shelf Water (S > 34.7) and Ice Shelf Water (T<−1.9°C) are discussed. The general circulation in the area seems to consist of two large cyclonic gyres, one in the Filchner Depression and one north of the Ronne Ice Shelf. Each gyre shows a'warm'(T 1°C) southgoing flow of Modified Weddell Deep Water and a cold northward flow of Ice Shelf Water. The mean surface current was found to be 8cm/s towards the north-west along the barrier. The mean flow below the ice shelf shows significant components normal to the barrier, and mixing seems to be very efficient here. Well mixed layers down to more than 150 m were observed. North of Berkner Island the water level shows a typical mixed tide with tidal range ∼3m. In the tidal currents the semidiurnal constituents dominate (∼30cm/s) and with the largest current components normal to the barrier.     

Hydrographic observations from the Weddell Sea during the Norwegian Antarctic Research Expedition 1976/77

CTD observations from the southern Weddell Sea in 1977 show that Ice Shelf Water originating under the floating Filchner Ice Shelf overflows at the sill of the Filchner Depression and can be identified on the continental slope at more than 2000m depth. Intrusions of Weddell Deep Water upon the shelf are especially noticeable in the region of dense shelf water outflow and are possibly driven by the outflow. Anomalous low core temperature of Weddell Deep Water is probably related to winter convection in the Weddell Polynya. Anomalous CTD stations at the periphery of the 1976 winter polynya region indicate that deep convection phenomena, as reported by Gordon (1978), are perhaps quite common. The observations indicate that double diffusive convection is important for vertical heat transport in the central Weddell Sea.     

“重庆雾”动力统计预报模型

本文首先对重庆雾1981～1987年159个例进行500hPa、700hPa、850hPa各气象要素的相关和合成分析,得到了影响重庆雾的主要因子和主要关键区以及雾发生时24小时以前各层要素场的异常特征。在此基础上,对重庆雾进行了分类,用关键区的因子作为自变量,利用逐步回归残差订正和模型集成,建立起重庆雾24小时预报模型,并设计成软件系统,在IBM机上自动预报。