东天山库姆塔格发现辉长岩中钼的超常富集     

程松林 《地质与勘探》2010,46(6):1015-1018

在新疆东天山库姆塔格新发现了辉长岩中钼元素的超常富集,超过了目前的工业品位。从野外产状看,与钼矿化直接相关的岩石均为辉长岩,共两类:一是规模较小但全岩矿化的辉长岩脉;二是规模较大但没有矿化的辉长岩体;矿化的辉长岩脉穿插于非矿化的辉长岩体之中。虽然辉长岩体矿区东侧有中酸性岩浆岩存在,但野外产状和现有的物化探工作尚未发现钼矿化与中酸性岩浆岩有直接关系。无论辉长岩的形成与钼的富集是否属于同一次地质作用的产物,这都可能是一种尚未被认识的、全新的钼矿床(矿化)类型,具有重要的理论意义。  相似文献   

九江堤防塑料排水板软基处理施工技术          下载免费PDF全文

王志磊 《探矿工程》2010,37(11):61-63

塑料排水板在海堤、公路、码头、水闸等软基加固工程中应用较广,塑料排水板处理软地基,是用塑料排水板将地基中的水排除,以增加作用于土颗粒的有效应力来加速地基固结沉降,达到提高强度的目的。在九江市日元贷款城市防洪工程八里湖大堤软基处理中成功应用了塑料排水板施工技术,结合该工程实例。介绍了塑料排水板施工工艺。  相似文献   

Tidal modification and its effect on sluice-gate outflow after completion of the Saemangeum dike,South Korea     

Seok Lee  Heung-Jae Lie  Kyu-Min Song  Cheol-Ho Cho  Eun-Pyo Lim 《Journal of Oceanography》2008,64(5):763-776

This study examined tidal modification and change in tidal currents caused by the construction of the Saemangeum dike, based on field observations and a numerical model. The Saemangeum dike was completed in April 2006, enclosing an estuarine area along the mid-western coast of South Korea. After closure of the dike, the tidal range outside the dike decreased slightly but significantly, while the inside tidal range decreased drastically. The numerical model results show that the dike construction has influenced tidal energy propagation and the tidal system in the Yellow Sea. The tidal current speed near the dike decreased abruptly following closure of the dike, except in front of the sluice gates. Since completion of the dike, outflow water discharged from the sluice gates has longer residence times due to the weakened tidal current; the change in the tidal current field has also caused greater northward expansion of outflow water. The sluice gates release fresher water, which spreads over the sea surface mainly by inertial momentum near the gate; this water is then gradually mixed with sea water farther from the gate. The less saline, possibly more contaminated outflow impacts the marine environment near the Saemangeum dike. Controlling the discharge and gate-opening timing can partially mitigate these impacts on the marine environment.  相似文献   

Petrology of gabbroic xenoliths in 1960 Kilauea basalt: crystalline remnants of prior (1955) magmatism     

R. V. Fodor  R. B. Moore 《Bulletin of Volcanology》1994,56(1):61-73

The 1960 Kapoho lavas of Kilauea’s east rift zone contain 1–10 cm xenoliths of olivine gabbro, olivine gabbro-norite, and gabbro norite. Textures are poikilitic (ol+sp+cpx in pl) and intergranular (cpx+pl±ol±opx). Poikilitic xenoliths, which we interpret as cumulates, have the most primitive mineral compositions, Fo_82.5, cpx Mg# 86.5, and An_80.5. Many granular xenoliths (ol and noritic gabbro) contain abundant vesicular glass that gives them intersertal, hyaloophitic, and overall ‘open’ textures to suggest that they represent ‘mush’ and ‘crust’ of a magma crystallization environment. Their phase compositions are more evolved (Fo_80–70, cpx Mg# 82–75, and An_73–63) than those of the poikilitic xenoliths. Associated glass is basaltic, but evolved (MgO 5 wt%; TiO₂ 3.7–5.8 wt%). The gabbroic xenolith mineral compositions fit existing fractional crystallization models that relate the origins of various Kilauea lavas to one another. FeO/MgO crystal–liquid partitioning is consistent with the poikilitic ol-gabbro assemblage forming as a crystallization product from Kilauea summit magma with ∼8 wt% MgO that was parental to evolved lavas on the east rift zone. For example, least squares calculations link summit magmas to early 1955 rift-zone lavas (∼5 wt% MgO) through ∼28–34% crystallization of the ol+sp+cpx+pl that comprise the poikilitic ol-gabbros. The other ol-gabbro assemblages and the olivine gabbro-norite assemblages crystallized from evolved liquids, such as represented by the early 1955 and late 1955 lavas (∼6.5 wt% MgO) of the east rift zone. The eruption of 1960 Kapoho magmas, then, scoured the rift-zone reservoir system to entrain portions of cumulate and solidification zones that had coated reservoir margins during crystallization of prior east rift-zone magmas. Received: January 7, 1993/Accepted: November 23, 1993  相似文献   

The stress state near Spanish Peaks,colorado determined from a dike pattern   总被引：1，自引：0，他引：1  

Otto H. Muller  David D. Pollard 《Pure and Applied Geophysics》1977,115(1-2):69-86

The radial pattern of syenite and syenodiorite dikes of the Spanish Peaks region is analysed using theories of elasticity and dike emplacement. The three basic components of Odé's model for the dike pattern (a pressurized, circular hole; a rigid, planar boundary; and uniform regional stresses) are adopted, but modified to free the regional stresses from the constraint of being orthogonal to the rigid boundary. Dike areal density, the White Peaks intrusion, the strike of the upturned Mesozoic strata, and the contact between these strata and the intensely folded and faulted Paleozoic rocks are used to brient the rigid boundary along a north-south line. The line of dike terminations locates the rigid boundary about 8 km west of West Peak. The location of a circular plug, Goemmer Butte, is chosen as a point of isotropic stress. A map correlating the location of isotropic stress points with regional stress parameters is derived from the theory and used to determine a regional stress orientation (N82E) and a normalized stress magnitude. The stress trajectory map constructed using these parameters mimics the dike pattern exceptionally well. The model indicates that the regional principal stress difference was less than 0.05 times the driving pressure in the West Peak intrusion. The regional stress difference probably did not exced 5 MN/m².  相似文献   

Volcanoes as possible indicators of tectonic stress orientation — Aleutians and Alaska     

Kazuaki Nakamura  Klaus H. Jacob  John N. Davies 《Pure and Applied Geophysics》1977,115(1-2):87-112

A new method for obtaining from volcanic surface features the orientations of the principal tectonic stresses is applied to Aleutian and Alaskan volcanoes. The underlying concept for this method is that flank eruptions for polygenetic volcanoes can be regarded as the result of a large-scale natural magmafracturing experiment. The method essentially relies on the recognition of the preferred orientation of radial and parallel dike swarms, primarily using the distribution of monogenetic craters including flank volcanoes. Since dikes tend to propagate in a direction normal to the minimum principal stress (T-axis), the method primarily yields the direction of the maximum horizontal compression (MHC) of regional origin. The direction of the MHC may correspond to either the maximum (P-axis) or intermediate (B-axis) principal stress.The direction of MHC obtained at 20 volcanoes in the Aleutian arc coincides well with the direction of convergence between the Pacific and North American plates. This result provides evidence that in the island arc the inferred direction of MHC is parallel to the maximum principal tectonic stress. In the back-arc region, general E-W trends of MHC are obtained from seven volcanic fields on islands on the Bering Sea shelf and the mainland coast of Alaska. These volcanic fields consist mostly of clusters of monogenetic volcanoes of alkali basalt. In the back-arc region, the trends of MHC may correspond to an E-W intermediate, a vertical maximum, and a N-S minimum principal stress.Implications for the tectonics of island arcs and back-arc regions are: (1) volcanic belts of some island arcs, including the Aleutian arc, are under compressional deviatoric stress in the direction of plate convergence. It is improbable that such arcs would split along the volcanic axis to form actively spreading marginal basins. (2) This compressional stress at the arc, probably generated by underthrusting, appears to be transmitted across the entire arc structure, but is apparently replaced within several hundred kilometers by a stress system characterized by horizontal extension (tensional deviatoric stress) in the back-arc region. (3) The volcanoes associated with these two stress systems differ in type (polygenetic vs. monogenetic) and in the chemistry of their magmas (andesitic vs. basaltic). These differences and the regional differences in orientation of the principal tectonic stresses suggest that the back-arc stress system has its own source at considerable depth beneath the crust.Lamont-Doherty Geological Observatory Contribution No. 2503.  相似文献   

柴北缘乌兰北部三叠纪辉长岩的年代学和地球化学特征     

岳悦  孙德有  侯可军  彭银彪 《吉林大学学报(地球科学版)》2021,51(1):154-168

柴北缘乌兰地区中生代岩浆岩分布广泛，主要出露辉长岩、闪长岩、花岗闪长岩和花岗岩。乌兰北部两件辉长岩样品的LA-ICP-MS锆石U-Pb测年显示其加权平均年龄分别为（241.9±0.9） Ma和（245.4±1.9） Ma，说明其形成于中三叠世早期。辉长岩的w（SiO₂）为47.94%和52.01%，全碱质量分数较低（ALK为1.25%和1.47%），里特曼指数为0.33和0.26，属钙碱性系列岩石；w（Cr）（1 661.00×10^-6和1 418.00×10^-6）、w（Ni）（394.00×10^-6和280.00×10^-6）和Mg^#值（81和79）极高，具幔源原生玄武岩浆特征。轻、重稀土元素分馏较弱，LREE/HREE为3.92和3.44，无明显负Eu异常，表明未发生明显的岩浆分异作用；富集K、Rb等大离子亲石元素，不同程度地亏损Nb、Ta、Ti等高场强元素，表现为与俯冲作用相关的弧岩浆岩特征。辉长岩的ε_Hf（t）值（-3.0~9.3）变化较大，暗示来自地幔的基性岩浆中有地壳组分的加入。结合区域地质演化特征研究成果，认为辉长岩形成于古特提斯洋向北俯冲背景下的大陆边缘弧环境，俯冲的洋壳板片脱水产生的流体导致上覆地幔楔部分熔融，形成玄武质岩浆，岩浆上升侵位过程中遭受地壳物质混染或与壳源岩浆发生混合作用。  相似文献   

内蒙古狼山地区乌花辉长岩的年代学、地球化学和Sr-Nd-Hf同位素组成:对地幔源区特征和岩石成因的约束     

张云  孙立新  张天福  孙义伟  张祺  李艳锋  杨泽黎  刘文刚 《现代地质》2020,34(3):450-465

内蒙古狼山地区乌花辉长岩体主要由橄榄辉长岩和角闪辉长岩组成,其锆石LA-ICP-MS U-Pb同位素测年结果表明,岩体形成于(319.8±1.8)~(325.4±1.6) Ma,属于早石炭世末期岩浆活动的产物。地球化学特征上,乌花辉长岩属低钾钙碱性玄武岩系列,具有较高的Mg^#(多在76.70~80.35之间)、Al₂O₃(13.55%~25.13%)和较低的TiO₂(0.18%~1.35%)。稀土总含量较低(∑REE= 8.92×10^-6~40.10×10^-6),稀土元素分馏程度不高,呈现出轻稀土元素(LREE)略微富集、重稀土元素(HREE)相对亏损((La/Yb)_N = 1.74~3.06)的特点,Eu呈明显的正异常(δEu=1.156~3.86)。岩石富集Pb和K、Rb、Ba、Sr等大离子亲石元素,明显亏损Nb、Ta、Zr、Hf、Th等高场强元素,较低的Zr含量(4.38×10^-6~26.6×10^-6)和Zr/Y比值(1.08~2.35),呈现出典型的俯冲-消减带弧火山岩的地球化学特征。Sr-Nd-Hf同位素研究表明,乌花辉长岩岩浆源区为富集地幔,在侵位过程中受到的地壳混染程度较弱。结合区域地质背景,认为乌花辉长岩为俯冲-消减构造体制下由俯冲带流体交代富集地幔部分熔融而成,代表了俯冲相对早期阶段的产物,指示华北板块北缘西段在早石炭世晚期开始进入到安第斯型活动大陆边缘阶段,并可能结束于早二叠世之前。  相似文献   

An experimental study on semi-brittle and plastic rheology of Panzhihua gabbro   总被引：10，自引：0，他引：10  

何昌荣  周永胜  桑祖南 《中国科学D辑(英文版)》2003,46(7):730-742

Rheological properties of the crust and upper mantle are essential data that are needed in modelling the mechanical behaviour of the shallow part of the earth. The importance of such data has been seen in discussions about the strength profile of continen…  相似文献   

某堤防工程中防渗墙对地下水运动规律影响的初步分析   总被引：1，自引：0，他引：1  

许季军  肖利  张伟  吴昌瑜 《岩土力学》2004,25(Z2):524-530

在1998年之后,长江堤防部分堤段采用了垂直防渗墙措施来处理堤身和堤基中存在的渗流隐患问题,但与此同时,也有人担心防渗墙实施后,会影响原有的江水与地下水之间补给排泄关系而带来新的环境问题.本文将以某实施了防渗墙的堤段为例,采用GMS软件中的MODFLOW计算模块模拟分析临江地层中地下水与江水的动态互动关系,并重点讨论了防渗墙实施后对这种关系的影响,分析结果认为,防渗墙实施后一般不会带来新的地下水环境问题.  相似文献