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391.
位于相山铀矿田西部的居隆庵铀矿床绿泥石化十分强烈,本文在对钻孔岩心样详细的野外和室内岩相学观测基础上,利用电子探针技术研究了绿泥石的产出状态及共生组合关系,并测定了其化学成分,探讨了该矿床绿泥石地球化学特征及其与铀矿成矿的关系。研究表明:①该矿床存在黑云母蚀变形成的绿泥石、长石蚀变形成的绿泥石、脉状绿泥石和与铀矿密切共生的绿泥石共4种类型绿泥石;②该矿床以蠕绿泥石和铁镁绿泥石为主,个别为鲕绿泥石,其形成温度介于190.5~269.9℃之间,平均为224.5℃,属于中低温条件;③该矿床绿泥石形成于还原环境,形成机制分为溶解-沉淀机制和溶解-迁移-沉淀机制两种;④绿泥石化过程改变了围岩的物理化学性质,改变了铀在岩石中的赋存状态并促使铀的预富集。 相似文献
392.
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Rock avalanches of the Ardon River valley at the southern foot of the Rocky Range,Northern Caucasus,North Osetia 总被引:1,自引:0,他引:1
Deposits of very large rock avalanches were identified at the southern foot of the Rocky Range of the Northern Caucasus. Cliffs facing the Ardon River are 1–1.5 km high and composed of Cretaceous and upper Jurassic, hard, crystaline limestone, underlain by softer, middle Jurassic shale, siltstone and sandstone flysh. The largest rock avalanche, at Karivhoh, is ~2×109 m3 in volume, travelled more than 7 km, and covered about 18 km2 with deposits up to 200–300 m thick. All rock-avalanche bodies are composed of intensively crushed debris overlain by a blocky carapace. Numerous subsequent landslides develop within these deposits, and pose a threat to villages built on them. 相似文献
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通过对西南某水电站在地下洞室的开挖过程中揭示的一些特殊地质现象分析认为该区存在一个从外表上很难发现的老滑坡体,根据该滑坡结构及解体特征,分析其变形破坏模式,认为它是一暴雨促发的平推式滑坡,并对其在各种工况下的稳定性进行量化评价。 相似文献
396.
南岭地区钨锡铌钽花岗岩及其成矿作用 总被引:25,自引:1,他引:25
在晚侏罗世时,南岭地区发生了与花岗岩有关的钨锡铌钽大规模成矿作用。依据花岗岩的岩石学、地球化学及其矿化特征,可将南岭地区含钨锡铌钽花岗岩划分为三个主要类型:含钨花岗岩、含锡钨花岗岩和含钽铌花岗岩。含钨花岗岩的地球化学特征可归纳为铝过饱和,低Ba+Sr 和TiO2,轻重稀土比值低,铕亏损强烈,富Y 和Rb,Rb/Sr 比值高,分异强烈。含锡钨花岗岩总体特征表现为TiO2 含量高,准铝质—弱过铝质,轻重稀土比值和CaO/(K2O+Na2O)比值高,富高场强元素、稀土、Ba+Sr 和Rb,低Rb/Sr 比值,分异演化程度较低。含钽铌花岗岩的地球化学特征主要为TiO2 含量和CaO/(K2O+Na2O)比值低,Al2O3/TiO2 和Rb/Sr 比值明显偏高,强过铝质,贫Ba+Sr、稀土和高场强元素,铕亏损强烈,明显富Rb 和Nb,高度分异演化。三类含矿花岗岩具有明显不同的演化特征,成矿作用与它们的演化密切相关。黑云母花岗岩主要与锡成矿作用有关,二云母花岗岩和白云母花岗岩主要产生钨矿化或锡钨共生矿化,钠长石花岗岩主要与钽铌或锡(钨)钽铌矿化有关。总结了南岭锡钨钽铌矿床的重要类型,提出了绿泥石化花岗岩型锡矿新类型,指出南岭地区要特别注意在含锡钨花岗岩中寻找此类锡矿和云英岩- 石英脉型锡钨矿。 相似文献
397.
The geochemical investigation of sediments deposited in the Renuka Lake basin and its adjoining wetland has shown variation
in the distribution and concentration of major, trace and REEs. The major elements are depleted in the lake in relation to
wetland and that of Post Archaean Australian, Shale (PAAS), except for CaO which is strikingly in excess and has a dilution
effect on SiO2 and other oxides and trace elements. The Wetland sediments, on the other hand, are enriched in Al2O3, Fe2O3, K2O and TiO2 and the latter three show a positive correlation with Al2O3 in both wetland and lake sediments suggesting their association with phyllosilicates and similar source rocks. The enrichment
of Y, Zr, Ni, Th, U and Nb in wetland compared to lake and their similarity with PAAS in the former, suggests more clay fractions
in the wetland. A high Zr/Hf ratio in wetland and lake sediments and a positive correlation of Zr with Y and HREE indicate
Zr control on HREEs. However, higher Zr/Yb and Zr/Th ratios in wetland compared to lake indicate mineral sorting during the
process of lighter particles (clays) being trapped in wetland soil. This is also reflected from negative correlation of GdN/YbN with Al2O3 and a strong positive correlation with SiO2 in wetland sediments. The wetland in this context has a control on lake sediment chemistry. The chondrite normalized REE
patterns are essentially the same for lake as well as wetland sediments but abundance decreases in the former. The similarity
of pattern with that of PAAS and negative Eu anomaly indicates a cratonic source of sediments. In a plot of the individual
samples, wetland samples cluster while lake samples are separated indicating fractionation of lake sediments. A strong positive
correlation of LaN/YbN with Al2O3 and a positive correlation of Zr-∑LREE and Zr-LaN/YbN suggest that LREEs are controlled by both phyllosilicates and zircon. The chemical index of alteration (CIA) indices in lake
sediments and in wetland are higher than PAAS indicating moderate chemical weathering in the source area. The petrography,
lack of felsic magmatic rock fragments, and negative correlation between Zr-(Gd/Yb)C indicate sedimentary source rocks for the detritus. This is in conformity with the Lesser Himalayan sedimentary sequence
belonging to neo-Proterozoic–Proterozoic age and constituting lake catchment of Renuka. The tectonic delineation and discriminant
function plots of lake and wetland sediments indicate their cratonic and/or quartzose sedimentary orogenic terrain source
that has been deposited in a passive margin setting. 相似文献
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399.
The East-Ujimqin complex, located north of the Erenhot–Hegenshan fault, North China, is composed of mafic–ultramafic and granitic rocks including peridotite, gabbro, alkali granite, and syenite. We investigated the tectonic setting, age, and anorogenic characteristics of the Xing’an–Mongolian Orogenic Belt (XMOB) through field investigation and microscopic and geochemical analyses of samples from the East-Ujimqin complex and LA-MC-ICP-MS zircon U–Pb dating of gabbro and alkali granite. Petrographic and geochemical studies of the complex indicate that this multiphase plutonic suite developed through a combination of fractional crystallization, assimilation processes, and magma mixing. The mafic–ultramafic rocks are alkaline and have within-plate geochemical characteristics, indicating anorogenic magmatism in an extensional setting and derivation from a mantle source. The mafic–ultramafic magmas triggered partial melting of the crust and generated the granitic rocks. The granitic rocks are alkali and metaluminous and have high Fe/(Fe + Mg) characteristics, all of which are common features of within-plate plutons. Zircon U–Pb geochronological dating of two samples of gabbro and alkali granite yielded ages of 280.8 ± 1.5 and 276.4 ± 0.7 Ma, placing them within the Early Permian. The zircon Hf isotopic data give inhomogeneous εHf(t) values of 8.2–14.7 for gabbroic zircons and extraordinary high εHf(t) values (8.9–12.5) for the alkali granite in magmatic zircons. Thus, we consider the East-Ujimqin mafic–ultramafic and granitic rocks to have been formed in an extensional tectonic setting caused by asthenospheric upwelling and lithospheric thinning. The sources of mafic–ultramafic and granitic rocks could be depleted garnet lherzolite mantle and juvenile continental lower crust, respectively. All the above indicate that an anorogenic magma event may have occurred in part of the XMOB during 280–276 Ma. 相似文献
400.