甘肃景泰县老虎山地区蛇绿岩及其上覆岩系中枕状熔岩的地球化学特征   总被引：10，自引：3，他引：10  

张旗  王岳明 《岩石学报》1997,13(1):92-99

甘肃景泰县老虎山地区蛇绿岩之上覆盖着一套镁铁质的喷出岩和沉积岩组合，位于蛇绿岩的枕状熔岩之上，不是蛇绿岩的成员，为蛇绿岩的上覆岩系。蛇绿岩的枕状熔岩具Ｎ－ＭＯＲＢ的特征，而其上覆岩系中的枕状熔岩类似Ｅ－ＭＯＲＢ。前者来自扩张脊的下部岩浆房；后者推测源于扩张脊之外的岩浆房，也是软流圈地幔中等至高程度部分熔融的产物，不过，可能有少量来自下地幔的物质的加入  相似文献   

From alkali basalt to phonolite in hand-size samples: vapor-differentiation effects in the Bouzentès lava flow (Cantal, France)     

Martial Caroff  Ccile Ambrics  RenC. Maury  Joseph Cotten 《Journal of Volcanology and Geothermal Research》1997,79(1-2)

The Bouzentès lava flow is a 20-m-thick alkali basalt flow emplaced during the last stage of formation of the Cantal stratovolcano at 4.2 Ma. Its upper part has 1- to 20-cm-thick vesicle-rich segregation sheets which recur every 0.1–2 m. These horizontal veins are hawaiitic in composition. They are characterized by hypertrophic development of their minerals (‘pegmatoids’) and by glassy phonolitic segregation vesicles. Internal differentiation within the Bouzentès lava flow was triggered by an unusually high water content, as suggested by pre-emptive iddingsite alteration of olivine phenocrysts. The proposed model of formation of the segregation sheets includes the upward motion of diapirs of residual melt plus addition of vapor from the bottom of the central liquid lens to the base of the upper solidified crust of the cooling lava flow. Olivine settling appears to have been inhibited or at least retarded by upward migration of melt plus vesicles. Most of the features observed in Bouzentès recall the internal differentiation processes usually described within thick Hawaiian lava lakes. The segregation vesicles are believed to result from an increase of gas solubility in residual melt during the crystallization process.  相似文献   

Comments on ‘Generation of Deccan Trap magmas’ by Gautam Sen     

H. C. Sheth 《Journal of Earth System Science》2002,111(4):483-485

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一个海底基性火山喷流成因的银锑矿床地质特征   总被引：8，自引：3，他引：8  

郑庆年 《矿床地质》1996,15(3):238-248

广东梅县嵩溪宝山是个产于具裂谷性质的永－梅裂陷槽南段翼部裂陷火山－沉积盆地内的一个海底基性火山喷流成因的银锑组合大型银矿。文中阐述以下问题：容矿层位岩性组合、建造和相及层位地球化学特征、矿区地质构造；海底基性熔岩玄武岩的地质、地球化学、稀土元素特征及其构造环境与成矿意义；矿体（层）形态、产状、矿石结构构造、矿物共生组合、地球化学、稀土元素、同位素、包裹体等  相似文献   

江西相山碎斑熔岩成因及其控矿作用的讨论   总被引：3，自引：0，他引：3  

李邦达 《地质论评》1993,39(2)

江西相山碎斑熔岩因其产状、岩石结构比较特殊,因此在岩石成因、岩相归属及岩体产状方面,长期以来存在多种不同看法。在控矿作用及找矿勘探方向看法上也有不同。作者通过多年野外地质、岩矿鉴定及矿床勘探资料的综合分析,从岩石学、岩石化学、地质产状上论证了相山岩体为一种介于火山与侵入之间的过渡性岩相—地下隐爆火山侵出相碎斑熔岩,具有一个主火山侵出通道和多个侧火山侵出通道的碎斑熔岩复式穹窿,其主、侧火山侵出通道机构及复式穹窿环锥状构造控制了矿田的格局及矿床和富矿体的生成部位。  相似文献   

Detailed Bathymetric Mapping of the Eastern Offshore Slope of Lipari Island (Tyrrhenian Sea): Insight into the Dark Side of an Arc Volcano     

Fabiano Gamberi  Michael P. Marani 《Marine Geophysical Researches》1997,19(4):363-377

A detailed multibeam coverage of the eastern offshore of Lipari Island(Aeolian arc) has permitted its subdivision into two sectors with differentmorphobathymetric features. In the northern one, numerous, large, previouslyundetected rhyolitic lava flows have been identified. In the southern one, aconical pyroclastic and epiclastic edifice built on top of afan-shaped lava field has been discovered. Since some of theseoffshore features have no analogues on land, their recognition has furnishednew information about the volcanic processes that built the eastern portionof Lipari Island. In particular, the finding of a huge volume of offshorerhyolitic lava flows, largely exceeding the amount of this kind of lavas onland, shows that the contribution of rhyolitic products in the building ofthe Lipari apparatus has been up to now underestimated. More generally, thecomparison between the land and the offshore units of Lipari volcanicapparatus indicates that a better investigation of the submarine portions ofvolcanic islands can reveal new, unforeseen aspects and greatly enhance ourknowledge about their evolution.  相似文献   

Volcanic and Seismic Swarm Events on the Reykjanes Ridge and Their Similarities to Events on Iceland: Results of a Rapid Response Mission     

Kathleen Crane  Lynn Johnson  Bruce Appelgate  Clyde Nishimura  Roger Buck  Chris Jones  Peter Vogt  Rubin Kos’yan 《Marine Geophysical Researches》1997,19(4):319-338

On 21 May 1989, a major earthquake swarm on the Reykjanes Ridge at59°44 N, 29°32 W at a water depth of about 1000 m andabout 500 km southwest of Iceland was detected on both the WorldwideStandard Seismic Network (WWSSN) and Icelandic seismic networks. As part ofa multi-institutional response to this swarm, the Naval ResearchLaboratory arranged for a P3 Orion Aircraft to deploy sonobuoys and AXBTs inthe immediate vicinity of the swarm activity. The detection of the swarmmotivated a survey of the region in 1990, using the towed SeaMARC IIside-looking sonar system. In 1990–1991 the Russian ShirshovInstitute of Oceanology offered the use of its MIR deep-divingsubmersibles to investigate the rise axis for recent volcanism. During 1992,a scientific team comprised of five US and ten Russian scientists mobilizedthe twin, deep diving Russian submersibles to study the spreading axis ofthe Reykjanes Ridge. The resulting data analyses allows us to conclude thatthe 1989 seismic swarm event occurred adjacent to and east of the largeaxial high in the center of our survey area. The length, width and depthrange of the earthquakes were very similar to major seismic swarm eventsconfined to fissure systems in the Krafla region of Iceland. It is likelythat the earthquake swarm was located on a fresh, well-defined systemof fissures and faults extending south of the northernmost axial highstudied. The earthquake swarm was probably associated with an emanation oflava creating a region of high backscatter, located just to the east of thecentral axial high. In addition, the region of high-backscatterremains unsampled because it lay underneath the nadir of the processedSeaMARC tracks used to plan the submersible survey. However many sampleswere taken and structural studies of the evolving Reykjanes Ridge werecarried out.  相似文献   

辽西义县组火山岩:拆沉作用还是岩浆混合作用的产物?   总被引：9，自引：4，他引：5  

张宏福  邵济安 《岩石学报》2008,24(1):37-48

通过对所有已发表的辽西义县组火山岩数据进行系统的主、微量元素和同位素分析,发现义县组火山岩以中基性为主,其上部层位中酸性组分增多。其高的Mg~#值和埃达克质特征并不是原始岩浆本身的性质,不能作为下地壳拆沉作用的有力证据。义县组火山岩的基性部分主要来自于受洋壳俯冲作用改造过的岩石圈地幔,并存在与古老下地壳来源的熔体不同程度的混合作用。因此,义县组火山岩是岩浆混合作用的产物而非下地壳拆沉作用的产物。底侵的下地壳也参与了义县组火山岩的形成,但软流圈组分的参与有限。  相似文献   

云南大红山哈母白祖熔岩铁矿矿床地质特征及成因探讨     

戚金栋  李俊  杨光树  肖斌  覃龙江 《矿产与地质》2016,(1):82-86

哈母白祖熔岩铁矿位于大红山铁铜矿区东部.矿体均赋存于大红山群红山组变钠质熔岩、绿片岩中,呈层状、似层状、透镜状产出,矿石以磁铁矿为主。矿床的形成与古元古代的海相基性岩浆喷发作用关系密切,具有火山喷溢和火山喷发沉积的特点,后期又经历了区域变质作用的改造,是经过多次地质作用而形成的多成因复合型矿床,成因类型初步判断为火山岩浆喷溢-喷发沉积-变质改造复合成因矿床。  相似文献   

Applied volcanology in geothermal exploration in Iceland     

Ingvar B. Fridleifsson 《Pure and Applied Geophysics》1978,117(1-2):242-252

In an active spreading area like Iceland, where the regional geothermal gradient is in the range 50–150°C/km, it is normally not a problem to find high enough temperature with deep drilling, but the difficulties arise with finding permeable layers at depth within the strata. Various volcanological methods can be applied in the search for aquifers and geothermal reservoir rocks. The flow pattern (as deduced from deuterium studies) indicates that the thermal water flows preferentially along high porosity stratiform horizons and dyke swarms from the recharge areas in the highlands to the hot spring areas in the lowlands. The primary porosity of the volcanic strata is dependent on the chemical composition and the mode of eruption of the volcanic units. Both the reservoir rocks and the flow channels forming the geothermal plumbing system are thought to vary from the Tertiary to the Quaternary provinces due to environmental conditions at the eruptive sites.  相似文献