共查询到20条相似文献，搜索用时 220 毫秒
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通过对区内岩性、沉积构造、古生物、地球化学特征以及对区内沉积相、沉积旋回、沉积模式等沉积环境的初步分析,认为研究区含煤建造形成于潮坪～泻湖沉积体系,由湖泊相、泻湖相、潮坪相、泥炭沼泽相组成.区内稳定可采的主要煤层形成于岛后潮坪～泻湖演变成的泥炭沼泽,厚度大,延伸广.影响区内各煤层厚度和煤质变化的沉积因素主要有地形、蓄水盆地水位、海相顶板等. 相似文献
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研究区位于额尔古纳地块的额木尔山中间隆起带东部边缘塔河过渡带内，砂金资源极为丰富，成矿条件十分优越，具有良好的找矿远景.通过对区内地层、岩浆岩、构造、地球物理、地球化学、遥感等综合信息进行分析，初步总结了区内成矿规律，指出找矿的有利部位，并对区内找矿关键作了简单探讨，为区内下步找矿工作取得突破性进展提供了一定的思路. 相似文献
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准噶尔盆地南缘平原区地下水动态及地下水资源可持续利用对策 总被引：1，自引：0，他引：1
准噶尔盆地南缘平原区是新疆地下水开发利用程度较高的地区之一,水资源短缺是严重制约区内经济发展的主要因素.研究和分析区内地下水位变化趋势和特征及由于地下水开采引发的一系列环境地质问题,对盆地南缘地下水资源评价、地下水合理开发利用和地质环境保护具重要指导意义.从区内30年来地下水位时间和空间变化分析入手,阐述了盆地南缘因人类经济活动引起的水位持续下降和地下水开采量持续增加特征及地下水开采引发的环境地质问题,为今后区内地下水资源评价及开发利用提供较好依据. 相似文献
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鄂尔多斯沙漠高原区白垩系含水层补给源的探讨 总被引：3，自引：1，他引：3
白垩系砂岩是部尔多斯高原的主要含水介质,对区内工农业、居民用水具有的重要的作用.大气降水面状入渗补给是白垩系含水层的主要补给来源,占区内补给量的78.5%.鄂尔多斯沙漠高原区影响大气降水入渗补给白垩系砂岩的因素有降雨特征、地形地貌和白垩系砂岩上覆岩性.研究表明,区内不同区域大气降水入渗补给特征不同,主要表现为:1、在区内南部大气降水间接补给砂岩,北部直接补给砂岩2、区内分水岭控制区内整体地下水循环;波状高原上具有梁地-过渡带-洼地分布的地貌特征控制着小区域地下水循环.认识大气降水对白垩系砂岩补给的这些规律,对合理开发利用水资源,保证当地经济可持续性发展具有重要意义.此外,白垩系砂岩的补给来源还有凝结水、地表水(河流、湖淖)、人工回灌等,补给量不大. 相似文献
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抚顺发电厂地面沉降成因分析及其灰色理论预测 总被引：2，自引：0，他引：2
在论述研究区环境地质条件的基础上,对区内地面沉降的成因进行了分析,并基于区内地面沉降监测点实际观测数据建立了灰色DGM模型,然后以此模型对研究区未来三年的地面沉降进行了预测,预测结果表明:在未来三年内,区内大部分主要建筑物基础地面最大沉降量将超出或接近允许值,而基础沉降差在允许值范围内. 相似文献
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Magma mixing and mingling textures in granitoids: examples from the Galway Granite, Connemara, Ireland 总被引：16，自引：0，他引：16
Summary ?Many granitoid intrusions display textural evidence for the interaction of mafic and silicic magmas during their genesis.
The ∼ 400 Ma Galway Granite exhibits excellent evidence for magma mixing and mingling both at outcrop/map scale (magma mingling
and mixing zones), and at thin-section/crystal scale (mixing textures). These textures – quartz ocelli, rapakivi feldspars,
acicular and mixed apatite morphologies, inclusion zones in feldspars, anorthite ‘spikes’ in plagioclase, sphene ocelli, K-feldspar
megacrysts in mafic microgranular enclaves (MME), and mafic clots – constitute a textural assemblage whose origin can be explained
in terms of magma mixing and mingling models. Furthermore, textures from this assemblage have been recorded throughout the
Galway batholith indicating that magma mingling and mixing played a key role during its evolution.
Received November 18, 2000; revised version accepted November 6, 2001 相似文献
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Mizuhiko Akizuki 《Lithos》1983,16(4):249-254
Spherulites consisting of fibrous alkali feldspar and silica minerals are produced by devitrification of rhyolite glass under hydrothermal conditions. The alkali feldspars (Ab72.5Or23.0An4.5, Ab81.7Or14.0An4.3) in spherulites from two localities in Japan consist of triclinic anorthoclase showing fine cross-hatched twinning and monoclinic sanidine showing fine cross-hatching not attributable to twinning. The cross-hatching, which corresponds to albite and pericline twinning, is produced in the process of transition from a monoclinic to a triclinic phase. The spherulite may develop at a temperature lower than about 200°C because the co-existing silica mineral is not quartz, but metastable tridymite. According to the phase diagram of the alkali feldspars by MacKenzie (1952), the alkali feldspars should have been triclinic during growth. However, the textures show that the alkali feldspar grew as a disordered monoclinic phase. Because of the high growth rate, the Al/Si disordered structure was produced during growth and afterwards transformed into a triclinic structure with cross-hatched twinning. 相似文献
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A well-developed regolith is preserved beneath early Proterozoic (Aphebian) rocks of the Otish and Mistassini Groups in Central Quebec, Canada. The regolith is covered by fluviatile clastic rocks (Otish Group) in the north, and by a thick sequence of stromatolitic and sandy dolomite (Mistassini Group) in the south.Where preserved beneath clastic rocks, the regolith exhibits the structures and textures of its crystalline parent rocks (tonalite, gneiss and amphibolite), despite the alteration of feldspars to clay minerals and the partial oxidation of biotite. A later event recrystallized the clay minerals to muscovite, while conserving the original outline of the feldspars. Beneath the dolomite, the regolith was largely replaced by dolomite, but retains many original textures. Dolomite replaced first the clay minerals, then quartz and unaltered feldspars and finally biotite. Repeated crustifications of dolomite with intervals of chert and minor anthraxolite surround unaltered blocks of crystalline rock within the regolith profile and similar complex veins fill many master joints. These veins are identical in composition to vug fillings throughout the overlying carbonate formations. Clasts of partly dolomitized regolith included in non-dolomitic sands filling channels and scours dug deep into the profile, suggest that dolomitization commenced very early, possibly related to a sabkha environment developed during the transgression. 相似文献
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Axel Müller 《Geology Today》2007,23(3):114-120
Rapakivi granites, especially the famous rapakivis from southern Finland, are some of the most attractive building and decorative stones, used world-wide because of their striking textures and beautiful colours. But rapakivi granites are more than just building material, they have also been studied scientifically for over 100 years to try to explain the formation of their plagioclase-mantled alkali feldspar ovoids, the rapakivi feldspars which are responsible for the unique texture of the rock. Despite all the work which has been done on them, the formation of this distinctive texture is still not fully understood. Rapakivi granite complexes are not just a 'pretty face', they are also associated with important tin deposits in Rondônia and Amazonas in Brazil. 相似文献
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钾长石和斜长石是花岗岩中最主要的造岩矿物,约占岩石中矿物总含量的65%。研究稀有元素在二类长石里的数量分配,是探讨稀有元素存在形式、富集规律、稀有元素与主要造岩元素的相互关系以及稀有元素矿物成因的重要依据之一,也是地球化学研究工作中不可缺少的一环。为了获得纯钾长石和纯斜长石,以往地质工作人员主要寻找岩石中长石斑晶,然后利用钻头和小铁锤逐粒雕取;或用氢氟酸-玫棕试剂染色法把染有红色的钾长石和未染色的斜长石在双目镜下用手工分别挑选。显而易见,用这两种方法每完成一个样品必将花费很多时间,在缺少大斑晶和需要较多数量长石单矿物的情况下,往往会迫使此项研究工作陷于停顿。为了探索长石分选法,作者先后作了优先浮选、静电选、重液分离三个项目的条件实验。鉴于钾长石-斜长石的比重、可浮性、导磁率、导电率都极其相近,是选矿学上较难分选的矿物之一,因此最初的实验都告失败。 相似文献
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We review petrologic observations of reaction textures from high-grade rocks that suggest the passage of fluids with variable alkali activities. Development of these reaction textures is accompanied by regular compositional variations in plagioclase, pyroxenes, biotite, amphibole and garnet. The textures are interpreted in terms of exchange and net-transfer reactions controlled by the K and Na activities in the fluids. On the regional scale, these reactions operate in granitized, charnockitized, syenitized etc. shear zones within high-grade complexes. Thermodynamic calculations in simple chemical systems show that changes in mineral assemblages, including the transition from the hydrous to the anhydrous ones, may occur at constant pressure and temperature due only to variations in the H2O and the alkali activities. A simple procedure for estimating the activity of the two major alkali oxides, K2O and Na2O, is imple- mented in the TWQ software. Examples of calculations are presented for well-documented dehydration zones from South Africa, southern India, and Sri Lanka. The calculations have revealed two end-member regimes of alkalis during specific metamorphic processes： rock buffered, which is characteristic for the precursor rocks containing two feldspars, and fluid-buffered for the precursor rocks without K-feldspar. The observed reaction textures and the results of thermodynamic modeling are compared with the results of available experimental studies on the interaction of the alkali chloride and carbonate-bearing fluids with metamorphic rocks at mid-crustal conditions. The experiments show the complex effect of alkali activities in the fluid phase on the mineral assemblages. Both thermodynamic calculations and experiments closely reproduce paragenetic relations theoretically predicted by D.S. Korzhinskii in the 1940s. 相似文献
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Summary Feldspar phenocrysts in alkali rhyolite from Oki-Dogo island in the Sea of Japan show mantled textures with cores of anorthoclase and rims of sanidine. These feldspars were examined by electron microscopy, X-ray diffraction and X-ray microanalysis. Anorthoclase first crystallized, then was partially resorbed, and finally sanidine overgrew on the anorthoclase. Saw-tooth or comb-like interfaces between the cores and rims were likely formed at the magmatic stage of resorption and overgrowth. Optically perthitic intergrowths appear in thin sections cutting saw-tooth or comb-like interfaces of the mantled feldspars. The sanidine preserves primary cryptoperthitic textures of a periodicity smaller than 10 nm, which are considered to have been produced by subsolidus exsolution after the resorption event ended. The anorthoclase has no exsolution texture under an electron microscope.
With 6 Figures 相似文献
Feldspatkristalle in Alkali-Rhyolith von der Insel Oki-Dogo, Japan
Zusammenfassung Feldspatkristalle in Alkali-Rhyolith von der Oki-Dogo Insel im Japanischen Meer zeigen ummantelte Texturen mit Kernen von Anorthoklas und Rändern von Sanidin. Diese Feldspate wurden mit Elektronenmikroskopie, Röntgendiffraktion und Mikrosondenanalyse untersucht. Anorthoklas kristallisierte zuerst, wurde dann teilweise resorbiert und schließlich wuchs Sanidin über den Anorthoklas. Sägezahn- und Kamm-ähnliche Grenzen zwischen Kernen und Rändern wurden wahrscheinlich wahrend des magmatischen Stadiums von Resorption und Überwachsung gebildet. Unter dem Mikroskop erkennt man, daß perthitische Verwachsungen durch Sägezahn- oder Kamm-artige Grenzen der ummantelten Feldspäte hinwegsetzen. Der Sanidin erhellt primäre kryptoperthitische Texturen mit einer Periodizität von > 10 nm, die als Produkte einer Subsolidus-Entmischung nach der Resorption interpretiert werden. Anorthoklas läßt unter dem Elektronenmikroskop keine Entmischungstexturen erkennen.
With 6 Figures 相似文献
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The paragenic minerals plagioclase,perthite,biotite,hornblende and pyroxene in acid-granite alkali-granite,monzonite and volcanic rocks collected from seven areas different in thermal history have been determined.On the basis of 14 plateau age spectra and isochron ages of paragenic miner-als in conjunction with the observed mineral textures ,the suitability of plateau age spectra of plagioclase and perthite and their thermo-chronological significance are discussed in this paper.The results indicate that undisturbed feldspar gives satisfactory^40Ar-^39Ar plateau ages in consis-tence with those of paragenic minerals.This means that feldspars from the undisturbed area are suita-ble for ^40Ar-^39Ar dating .On the other hand,the age spectra of feldspars as well as of biotite,pyroxene and hornblende affected by tectonic or thermodynamic events appear unsmooth at varying temperatures,thus complicating their interpretation.Feldspars may give an emplacement age of a rock and /or that of the latest thermodynamic event,depending on the intensity of the event and the retentivity of Ar in the mineral. 相似文献
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C. J. A. SOUTENDAM 《Sedimentology》1967,8(4):281-290
For the study of the surface textures of quartz sand grains the normal microscope was used, besides the sofar generally applied electron microscope, and a new method was developed for using incident illumination. Grains from a desert sand and a river sand were studied, the former grains displayed textures not described yet by previous authors, the latter grains possessed a variety of textures, some of which have been found with beach sand grains, others with glacial sand grains by previous investigators. 相似文献