云南鸡街碱性超基性岩杂岩体中橄榄石的化学成分分带现象     

吴静  黄智龙  A.McCaig  E.Condliffe  颜以彬 《矿物学报》2004,24(1):7-13

云南鸡街碱性超基性岩杂岩体的主体岩石为岩浆结晶分异作用的产物，形成顺序为霞霓钠辉岩→霓霞岩→磷霞岩。在杂岩体的霓霞岩中发现了1粒具分带现象的橄榄石，从中心到边缘，SiO2、MgO和NiO逐渐降低，而FeO和MnO逐渐升高。MgO与SiO2和NiO之间呈正相关关系，与FeO和MnO之间呈负相关关系，中心的Fo值(最高为86．91)略高于霞霓钠辉岩中斑晶橄榄石(Fo值：85．66～86．02)，而边缘的Fo值(最低为73．82)与霓霞岩中无分带现象橄榄石(Fo值：72．18～74．72)相近。各种证据表明，发现的具分带现象橄榄石可能不是霓霞岩熔体结晶分异作用的产物，而可能是霓霞岩熔体捕获的Fo值相对较高(高于霓霞岩橄榄石的Fo值)的橄榄石晶体内部MgO和FeO等成分扩散作用的结果。  相似文献   

断裂活动对金矿形成的作用机理          下载免费PDF全文

倪培兵 《地质找矿论丛》2005,20(Z1):7-9

文章从断裂活动和热液流体迁移的热动力学角度阐述了金矿热液形成、迁移和富集沉淀的物理化学机理,得出了断裂活动不仅为金矿形成提供了储矿空间,更主要的是为金矿热液形成提供了活化热能和大量流体,为其迁移提供了动能,为其沉淀富集提供了有利的、多期多阶段的物理化学条件.  相似文献   

多面聚能射孔压裂排放瓦斯的研究     

罗勇 《岩土工程技术》2005,19(1):28-31

复合射孔技术能有效地控制射孔方向和压裂缝的扩展。对其作用机理进行了初步的分析研究 ,并对相关参数进行了理论计算。针对煤层的特性 ,将该技术用于煤层致裂 ,经过现场应用 ,效果良好。该技术在煤层致裂爆破中的发展方向较多 ,有良好的应用前景  相似文献   

Sur l’origine karstique et l’age plio-quaternaire des accumulations bréchiques dites ?brèches marines et paléocènes? d’Amélie-les-Bains (Pyrénées-Orientales, France)     

Joseph Canerot  Bernard Laumonier  Thierry Baudin 《Eclogae Geologicae Helvetiae》2006,99(1):49-64

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Fracture Toughness Evaluation Based on Tension-softening Model and its Application to Hydraulic Fracturing     

Kazushi Sato  Toshiyuki Hashida 《Pure and Applied Geophysics》2006,163(5-6):1073-1089

This paper discusses the applicability of the tension-softening model in the determination of the fracture toughness of rocks, where the fracture toughness evaluated based on the tension-softening model is compared with the crack growth resistance deduced from laboratory-scale hydraulic fracturing tests. It is generally accepted that the fracture process is dominated by the growth of a fracture process zone for most types of rocks. In this study, the J-integral based technique is employed to determine the fracture toughness of Iidate granite on the basis of the tension-softening model, where compact tension specimens of different dimensions were tested in order to examine the specimen size effect on the measured fracture toughness. It was shown that the tension-softening relation deduced from the J-integral based technique allowed us to determine the specimen size independent fracture toughness K_c of Iidate granite. Laboratory-scale hydraulic fracturing tests were performed on cubic specimens (up to a 10 m sized specimen), where cyclic pressurization was conducted using a rubber-made straddle packer to observe the extent of the hydraulically induced crack. The experimental results of pressure and crack length were then used to construct the crack growth resistance curve based on the stress intensity factor K. The crack growth resistance obtained from the hydraulic fracturing tests was observed to initially increase and then level off, giving a constant K value for a long crack extension stage. The plateau K value in the crack growth resistance curve was found to be in reasonable agreement with the fracture toughness K_c deduced from the tension-softening relation. It was demonstrated that the tension-softening model provides a useful tool to determine the appropriate fracture toughness of rocks, which may be applicable for the analysis of the process of large-scale crack extension in rock masses.  相似文献   

东天山博格达裂谷发现大规模层间水力断裂系统   总被引：7，自引：0，他引：7  

汪劲草  王建业  王正云  耿文辉  肖龙 《地球科学进展》1998,13(4):403-406

层间水力断裂是沉积盆地深处与大规模流体活动有关的断层,目前的地球物理方法及深源钻探取样已经证实活动水力断裂广布于中、新生代沉积盆地中。已褶皱成山的晚古生代裂谷盆地中发育的大规模层间水压碎屑岩是过去沉积盆地发育过程中大规模流体相带及其水力压裂作用的地质遗迹。研究了水压碎屑岩的地质特征、形成地质条件及构造—流体动力作用成岩模式。认为研究水力断裂对认识上地壳层圈拆离、推覆构造、流体输导、多位成矿、油气运移、慢震活动及常规地震发生等问题有极重要的地质意义。  相似文献   

冀东长城式金矿赋金角砾状岩石成因初探     

翟安民 《华北地质》1998,21(3)

冀东地区新发现一批产在中元古代碳酸盐岩层中的金矿床（点）,文中对该类矿床的容矿围岩特征及其成因、产出的区域构造背景进行了讨论,提出容矿角砾岩是液压致裂角砾岩,是一种矿控构造岩。  相似文献   

地下洞室围岩应力的测量研究   总被引：3，自引：2，他引：3  

安其美  郭启良 《岩土力学》1996,17(1):48-53

介绍了在地下洞室不同方向的钻孔中，采用水力劈裂技术进行的原位地应力测量。结合广西全州天湖水电站，广州抽水蓄能电站和广西龙滩水电站的实测结果，分析研究了地下洞室围岩应力的分布状态及影响围岩应力分布的主要因素。  相似文献   

Pacific-type orogeny revisited: Miyashiro-type orogeny proposed   总被引：30，自引：0，他引：30  

Shigenori  Maruyama 《Island Arc》1997,6(1):91-120

Abstract The concept of Pacific-type orogeny is revised, based on an assessment of geologic data collected from the Japanese Islands during the past 25 years. The formation of a passive continental margin after the birth of the Pacific Ocean at 600 Ma was followed by the initiation of oceanic plate subduction at 450 Ma. Since then, four episodes of Pacific-type orogeny have occurred to create an orogenic belt 400 km wide that gradually grew both oceanward and downward. The orogenic belt consists mainly of an accretionary complex tectonically interlayered with thin (<2 km thick), subhorizontal, high-P/T regional metamorphic belts. Both the accretionary complex and the high-P/T rocks were intruded by granitoids ～100 million years after the formation of the accretionary complex. The intrusion of calc-alkaline (CA) plutons was synchronous with the exhumation of high-P/T schist belts. Ages from microfossils and K-Ar analysis suggest that the orogenic climax happened at a time of mid-oceanic ridge subduction. The orogenic climax was characterized by the formation of major subhorizontal orogenic structures, the exhumation of high-P/T schist belts by wedge extrusion and subsequent domed uplift, and the intrusion-extrusion of CA magma dominantly produced by slab melting. The orogenic climax ended soon after ridge subduction, and thereafter a new Pacific-type orogeny began. A single Pacific-type orogenic cycle may correspond to the interaction of the Asian continental margin with one major Pacific oceanic plate. Ophiolites in Japan occur as accreted material and are not of island-arc but of plume origin. They presumably formed after the birth of the southern Pacific superplume at 600 Ma, and did not modify the cordilleran-type orogeny in a major way. Microplates, fore-arc slivers, intra-oceanic arc collisions and the opening of back-arc basins clearly contributed to cordilleran orogenesis. However, they were of secondary importance and served only to modify pre-existing major orogenic components. The most important cause of cordilleran-type orogeny is the subduction of a mid-oceanic ridge, by which the volume of continental crust increases through the transfer of granitic melt from the subducting oceanic crust to an orogenic welt. Accretionary complexes are composed mainly of recycled granitic sediments with minor amounts of oceanic material, which indicate that the accretion of oceanic material, including huge oceanic plateaus, was not significant for orogenic growth. Instead, the formation and intrusion of granitoids are the keys to continental growth, which is the most important process in Pacific-type orogeny. Collision-type orogeny does not increase the volume of continental crust. The name ‘Miyashiro-type orogeny’ is proposed for this revised concept of Pacific-type or cordilleran-type orogeny, in order to commemorate Professor A. Miyashiro's many contributions to a better understanding of orogenesis.  相似文献   

盆地演化认识中的几个问题     

Chiyu.  W 《地学前缘》1995,2(3):29-44

本文论述了盆地演化认识中的几个主要问题。一是陆缘裂解过程，华南边缘传统上认为是被动裂谷边缘的一个例子，其东部沉积物记录了压实的历史，它明显不同于被动裂谷作用模式，而是显示早第三纪大规模上隆和侵蚀的特征；而且，该地区覆盖在下地壳楔形体上面，具有比周围地壳明显要高的地震速度和密度，指示岩浆底侵作用。这些证据说明，与被动裂谷作用模式相比，华南边缘与主动裂谷作用模式较为一致，它是由早第三纪华南边缘东部底下地幔柱形成的主动裂谷。另一个问题是关于页岩的浅部破裂作用机理。大多数研究者认为，微裂隙的形成需要高孔隙压力，它限于深埋、低渗透率的岩石。然而，最近从北海观察表明，在第三纪页岩中，整个盆地范围内的破裂型式从未达到大于几百米的埋藏深度。这说明泥质源岩经历了水压破裂和浅部脱水，在破裂前可能达到深埋后生作用所需要的深度，实质上渗透率的改变是由于源岩的浅部破裂作用可能根本上改变了烃类的初次运移时间和效率。  相似文献