Thermal budget of the Transylvanian lithosphere. Reasons for a low surface heat-flux anomaly in a Neogene intra-Carpathian basin     

Maria Andreescu  Søren B. Nielsen  Gabriela Polonic  Cri&#;an Demetrescu 《Geophysical Journal International》2002,150(2):494-505

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Fracturation d'âge Aptien supérieur sur la bordure orientale de la plate-forme arabique (Haushi-Huqf,Oman)Aptian faulting (Shu'aiba Formation) on the eastern edge of the Arabian Platform (Haushi-Huqf,Oman)     

Christian Montenat  Pascal Barrier 《Comptes Rendus Geoscience》2002,334(10):781-787

In the Haushi-Huqf (Eastern Central Oman) as in other parts of the Arabian platform, a major sedimentary break is recorded between the Early Aptian carbonates (Shu'aiba Formation) and the Albian orbitolinid-rich marls (Nahr Umr Formation). The unconformity corresponds to a succession of events: (1) a brusque interruption of the regressive sequence of the Shu'aiba limestone (algae and small rudistid build-ups); (2) a stratigraphic gap related to the Late Aptian; (3) the development of a thick ferruginous crust (hardground) that covered the top surface of the Shu'aiba; the hardground is related to a forced flooding surface; (4) the Shu'aiba was rapidly drowned and buried under the Nahr Umr marls. Moreover, the Shu'aiba limestone was subject to faulting NW–SE-trending normal faults before lithification and formation of the ferruginous crust. The faulting episode is clearly dated: post-Early Aptian and pre-Albian. The signification of the faulting remains hypothetical. The syndiagenetic NW–SE normal faults may correspond to ‘en echelon’ faults, combined with transcurrent fault movements (for example the Haushi-Nafun Fault). The possible causes of these intra-platform transcurrent movements are discussed. To cite this article: C. Montenat, P. Barrier, C. R. Geoscience 334 (2002) 781–787.  相似文献   

Straight river: its formation and speciality     

WANG Sui-ji  NI Jin-ren 《地理学报》2002,12(1):72-80

Straight river is generally regarded as one of the typical river patterns in conventional classifications in terms of their channel plain landforms. However, very few straight patterns were found to be distributed in wider spatial and temporal spans in the self-adjusted fluvial rivers. Thus, the questions occur such as that is it possible for a channel takes on a stable straight pattern? What are the main factors controlling the processes of the river pattern formation and transformation from a straight to other patterns? Various theories and hypotheses including geomorphic threshold hypothesis, the extreme hypothesis on energy dissipation rate, the stability theory, etc. have been developed to explain the aforementioned questions, but none of them is sound for the explanation to the straight-river formation. From the modern fluvial plain patterns, the straight patterns are not as stable as other typical patterns which occurred in nature; from the historic records of the river sedimentation, no apparent evidence was found to support the stable straight river evolution. Based on the analysis of existing theories, observations, evolvement processes of the channel patterns in the experimental results, this paper concluded that the straight pattern should not be included as one of the typical patterns that are self-formed and developed. This study is of importance to understanding of the river pattern formation and transformation.  相似文献   

Locating and quantifying the seismic discontinuities in a complex medium through the migration and AVA analysis of reflected and converted waves: an application to the Mt Vesuvius volcano     

E. Auger  J. Virieux  A. Zollo 《Geophysical Journal International》2003,152(2):486-496

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锡铁山铅锌矿地质特征、矿床成因及找矿标志   总被引：4，自引：1，他引：4  

李如满  汪树栋 《矿产与地质》2003,17(3):218-221

通过找矿工作的实践，认为锡铁山铅锌矿床是由火山喷流沉积—后期热液叠加改造富集的块状硫化物多金属矿床。区域上NW—SE向早古生代形成的裂谷带，三级盆地内沉积的晚奥陶世滩间山群的大理岩与绿片岩系是表区找矿的最佳区段。而绢云绿泥斜长片岩、含碳质绢云绿泥片岩、白色大理岩、条带状大理岩是铅锌矿的最重要的找矿标志。  相似文献   

贵州寒武系底部黑色硅质岩成因及沉积环境探讨   总被引：14，自引：1，他引：14  

张位华  姜立君  高慧  杨瑞东 《矿物岩石地球化学通报》2003,22(2):174-178

贵州寒武系底部形成的黑色层状硅质岩，岩石展布广，层位稳定，厚度较大。硅质岩的δ^30Si值为—0．1‰～0．9‰，平均0．314‰；δ^18O值为12．8‰～21．2‰，通过δ^18O值计算出该区硅质岩形成温度82．2～162．5℃；硅质岩富含Ba、As、Sb、Bi和U，呈明显的Ce负异常。硅质岩的地球化学特征表明其主要成因是热水沉积作用。同时由于硅质岩主要是热水来源，所以在讨论其形成环境时还结合了岩相古地理的方法，指出该套硅质岩形成于深水缓坡至浅水滞流海环境之中。  相似文献   

青海锡铁山热水沉积型铅锌矿床的地球化学特征   总被引：15，自引：0，他引：15  

邓达文  孔华  奚小双 《矿物岩石地球化学通报》2003,22(4):310-313

通过对锡铁山铅锌矿床的围岩(矿石)化学成分、稀土及微量元素特征的研究，发现矿区地层普遍具有铈负异常(δCe=0．47～0．90)，为海相沉积岩，近矿围岩中Ag、Hg、As、Sb、Ba等热水沉积指示元素偏高，显示成矿流体性质为热卤水，矿区火山岩不发育，矿床类型可以划为Sedex型。  相似文献   

西藏尼玛地区古近纪美苏组的建立     

谢国刚廖思平  罗小川邹爱建 胡肇荣 《地质通报》2003,22(5):341-345

通过1：25万邦多区幅地质调查，在尼玛县西部拉舍—岷千日一带发现一套基性—中性—酸性—酸碱性火山岩岩石组合，其时代属古新世—始新世，新创建美苏组。描述了该组的分布、岩性、岩相、古生物及同位素年代特征，讨论了其形成的构造环境。  相似文献   

渤海湾老狼坨子海岸带^14C,^137Cs、^210Pb测年与现代沉积速率的加速趋势   总被引：10，自引：5，他引：10  

王宏 姜义李建芬  夏威岚M．VanStrydonck S．L．Goodbred 康慧 《地质通报》2003,22(9):658-664

通过对渤海湾西岸L剖面中同一关键层的碳酸钙和原生腹足类壳债权的^14C测年对比研究，确定了晚全新世的2800cal BP的层位及沉积速率0.045cm/a;8个样柱的^137Cs和^210Pbex强度、蓄积量揭示了距今约120年来堤后盐沼的平均沉积速率约为0.35cm/a，而面向开放海湾的潮坪上部则达到约2-3cm/a。研究区近1个世纪以来沉积速率的加速趋势，是渤海湾西岸泥质海岸带的特征之一。  相似文献   

浅论新疆海相火山热水沉积矿床的分带及其找矿意义   总被引：9，自引：0，他引：9  

王永新  田培仁 《地质与勘探》2003,39(4):6-11

新疆海相火山热水沉积矿床，一般在时间上没有明显的集中生长期。空间上依附于活动大陆边缘火山岛弧带，它在区域上和矿床本身具有矿种转化、类型转换、配套与分带特征。以块状氧化物、块状碳酸盐和块状硫化物转换序次来研究该类矿床。利用铁木尔特铅锌矿上部铅锌下部铜金，预须开普台铁矿上铁下铜；莫托沙拉铁锰矿上锰下铁中间铅锌重晶石等矿种转化规律和由块状氧化物和块状碳酸盐向块状硫化物成生过渡特点，预测诸如蒙库铁矿、赤龙峰火山盆地中铁矿和喀喇昆仑山各铁矿床(点)外围与深部转换、发展成为铜金矿的成矿前景。  相似文献