The effects of pre-existing normal faults on thrust ramp development: An example from the northern Apennines,Italy

The Umbria-Marche foreland fold-and-thrust belt in the northern Apennines of Italy provides excellent evidence to test the hypothesis of synsedimentary-structural control on thrust ramp development. This orogenic belt consists of platform and pelagic carbonates, Late Triassic to Miocene in age, whose deposition was controlled by significant synsedimentary extension. Normal faulting, mainly active from Jurassic through Late Cretaceous-Paleogene time, resulted in significant lateral thickness variability within the related stratigraphic sequences. By Late Miocene time the sedimentary cover was detached from the underlying basement and was deformed by east-verging folds and west-dipping thrusts. Two restored balanced cross sections through the southernmost part of the belt show a coincidence between the early synsedimentary normal faults and the late thrust fault ramps. These evidences suggest that synsedimentary tectonic structures, such as faults and the related lithological lateral changes, can be regarded as mechanically important controlling factors in the process of thrust ramp development during positive tectonic inversion processes.     

阿尔泰造山带构造演化研究中的几个关键问题剖析

对阿尔泰山地区的构造格局、构造变质、岩浆岩时代、动力热事件和构造区类型归属等几个地学基础问题进行深入细致研究的基础上，反演了阿尔泰地槽造山带形成和演化的递进历程。     

A Study on the Geological—Geochemical Dynamics of Hydrothermal Ore Deposition as Exemplified by the Muping—Rushan Gold Deposit Belt,Eastern Shandong,China

This paper presents a method of establishing a hydrothermal ore-forming reaction system.On the basis of the study of four typical hydrothermal deposits,the following conclusions concerning geochemical dynamic controlling during hydrothermal mineralization have been sions concerning geochemical dynaamic controlling during hydrothermal mineralization have been drawn:(1)The regional tectonic activities control the concentration and dispersion of elements in the ore-forming process in terms of their effects on the thermodynamic nature and conditions of the ore-forming reaction system.(2)During hydrothermal mineralization the activites of ore-bearing faults can be divideb into two stages:the brittle splitting stage and the brittle-tough tensing stage,which would create characteristically different geodynamic conditions for the geochemical thermodynamic ore-forming system.(3)The hydrothermal ore-forming reaaction system is an open dynamic system.At the brittle splitting stage the system was so strongly supersaturated and unequilibrated as to speed up and enhance the crystallization and differentiation of ore-forming fluids.And at the brittle-tough tensing stage,the ore-forming system was in a weak supersaturated state;with decreasing temperature and pressure the crystallization of oreforming material would show down,and it can be regarded as an equilibrated state.(4)In the lates stages of hydrothermal evolution,gold would be concentrated in the residual ore-forming solution.The pulsating fracture activite in this stage led to the crush of pyrite ore and it was then filled with gold-enriched solution,forming high-grage“fissure”gold ore.This ore-forming process could be called the coupling mechanism of ore formation.     

北秦岭南缘弧前盆地沉积作用及盆地发展

秦岭被商丹缝合带分为北秦岭和南秦岭两个部分,在北秦岭南缘残留着与俯冲作用相关的岛弧火山岩以及弧前沉积体。对沿海丹带两个地区(黑河地区和黑山地区)弧前沉积体岩相组合和相序的研究显示,它们主要由深水浊积岩系。火山碎屑岩,扇三角洲沉积以及局限性台地碳酸盐岩和陆棚碎屑岩组成。总的沉积序列显示向上变浅趋势,但在弧前内侧边缘则表现为向上变深趋势。两个不同地区岩相和相序的差异明显受物源、海平面变化以及特别是构造作用的挫制。深水浊积岩系所反映的线状物源供给形式、扇三角洲体系的发育和其内部不同沉积段反复重叠的特征指示一种活动构造环境。弧前区构造发展一方面与其前部加积或下部垫底作用有关,另一方面则在很大程度上受由斜向俯冲而导致的伸展作用的影响。     

湘中雪家坡脆韧性剪切构造岩地球化学特征

在１∶５万黄材幅区调中，对脆韧性剪切构造岩进行的岩石化学、微量元素、稀土元素研究表明，由中细粒含斑二云母二长花岗岩改造为糜棱岩化花岗岩、初糜棱岩、绢云母糜棱岩、硅化糜棱岩、千糜岩、糜棱片岩等，其化学成分发生了不同程度的改变。化学元素的分散、聚集或不变，既受原岩控制（继承性），又受变形强度和流体的成分、性质、活动性等控制（变化性）。     

湖北省随枣地区推覆构造格局的研究

研究区构造格局的基本特征是上地壳多层次自北而南的逆冲—拆离，柳林、洪清、大洪山３条逆掩断层与深部拆离面一起组成了尖端指向南的楔形薄皮构造。逆冲系统以背驮式扩展演化。多层次推覆构造格局因后期高角度断裂的切割破坏而复杂化，构造格局定型时代为燕山期     

安徽省铜陵地区侵入岩成因的实验研究

通过３７次成岩实验研究认为：（１）在地壳温度下，地壳物质的重熔不可能形成石英闪长质或更基性的岩浆；（２）碱性玄武岩浆同化花岗质地壳，可以生成石英闪长质和花岗闪长质岩浆，所产生的岩浆高钾富碱，属高钾岩系，与铜陵地区侵入岩相似；（３）高压下形成的岩浆比中压下形成的岩浆更高钾富碱；（４）在岩浆演化过程中铜与钾似无成因联系，钾与铜的“相关性”与它们的趋同性有关，即两者均于岩浆晚期富集。     

内蒙古西拉木伦断裂带韧性变形特征

西拉木伦断裂带在早二叠世末发生了韧性右行走滑，形成了包括韧性右行走滑带、韧性压扁带及弱韧性变形带在内的韧性变形带。据动力和运动分析，表明该韧性变形带为一普通剪切带，其中韧性右行走滑带在平面上以简单剪切为主，韧性压扁带在平面上以纯剪切为主。     

Radon,Lung Cancer Risk and Environmental Geology in Gejiu Area

The incidence of lung cancer in the Gejiu area of Yunnan Province ranks the first in the world.The radon level(indoor,soil) was measured in the Gejiu area by the SSNTD method from 1990 to 1996,The result indicates an extensive high-level of indoor radon in that area though U and Th are lower in local limestones,The indoor radon level of houses located in the geologic fault zone is 6 times high that 2km far from the fault zone.The reason probably is that the radon level of soil in the fault is 6-8 times high that 1 km far from the faults.our data indicate that a lower range of radon levels,0-100Bq.m^-3,exists in healthy families.However,a higher radon level,over 800 Bq.m^-3,is often found corresponding to that of cancer patients‘ homes(the house-owners are suffering from either lung cancer or leukaemia or liver cancer),Obviously,an increase in lung cancer incidence follows an increase in indoor radon level,The risk of cancer induced by indoor radon is no longer an inference,but a fact.     

Streambank fish-shelter structures help stabilize tributary streams in Wisconsin

 A significant proportion of stream sediment yield in North America comes from stream channel and bank erosion. One method used for stream stabilization is the bank installation of timber and stone fish-shelter structures, but there is little evidence for their potential effectiveness. Nine to nineteen years of precise survey data from Coon Creek, Wisconsin, however, show that fish structures enhance sediment deposition along the stream and may retard lateral migration of channels. Such structures have greater utility for sediment control when streams are eroding away a high bank and replacing it with a lower bank. Received: 18 October 1996 · Accepted: 4 February 1997