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1.
A. Kr?ner A. P. Willner E. Hegner A. Frischbutter J. Hofmann R. Bergner 《Geologische Rundschau》1995,84(3):437-456
Single zircons from two orthogneiss complexes, the Grey Gneiss and Red Gneiss, the lowermost tectonic units in the Erzgebirge, were dated. The grey Freiberg Gneiss is of igneous origin and has a 207Pb/206Pb emplacement age of 550±7 Ma. A quartz monzonite from Lauenstein contains idiomorphic zircons with a mean 207Pb/206Pb age of 555±7 Ma as well as xenocrysts ranging in age between 850 and 1910 Ma. Red gneisses from the central Erzgebirge contain complex zircon populations, including numerous xenocrysts up to 2464 Ma in age. The youngest, idiomorphic, zircons in all samples yielded uniform 207Pb/206Pb ages between 550±9 and 554±10 Ma. Nd isotopic data support the interpretation of crustal anatexis for the origin of both units. Nd(t) values for the grey gneisses are –7.5 and –6.0 respectively, (mean crustal residence ages of 1.7–1.8 Ga). The red gneisses have a wider range in Nd(t) values from –7.7 to –2.8 (T
DM ages of 1.4–1.8 Ga). The zircon ages document a distinct late Proterozoic phase of granitoid magmatism, similar in age to granitoids in the Lusatian block farther north-east. However, Palaeozoic deformation as well as medium pressure metamorphism ( 8 kbar/600–650° C) are identical in both gneiss units and distinguish these rocks from the Lusatian granitoids. The grey and red gneisses were overthrust by units with abundant high-pressure relicts and a contrasting P-T evolution. Zircon xenocryst and Nd model ages in the range 1000–1700 Ma are similar to those in granitoid rocks of Lusatia and the West-Sudetes, and document a pre-Cadomian basement in parts of east-central Europe that, chronologically, has similarities with the Sveconorwegian domain in the Baltic Shield. 相似文献
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Anestis Filippidis Panagiotis Misaelides Alexander Clouvas Athanasios Godelitsas Nikolaos Barbayiannis Ioannis Anousis 《Environmental geochemistry and health》1997,19(2):83-88
A black-sand formation located at Touzla Cape, near Thessaloniki city, Greece, was investigated using optical microscopy, powder-XRD, SEM-EDS, INAA and in-situ -ray spectrometry. This black sand is mainly composed of ilmenite, magnetite, garnet, zircon and rutile. Also present, in minor or trace amounts, are quartz, sphene, pyroxenes, sillimanite, feldspars, biotite, haematite, tourmaline, chromite, niobian-rutile and pyrrhotite. Niobian-rutile and pyrrhotite were found as inclusions in ilmenite and magnetite respectively. The radioactivity measurements indicated contributions of the uranium and thorium radioactive series and of 40K and 137Cs, and the maximum value of the total absorbed dose rate in air was found to be 62, 172, 8 and 2 nGy h-1 respectively. The main radioactivity of the uranium and thorium series is attributed to the fractions of zircon (304 µg Th g-1 and 157 µg U g-1), of ilmenite (89 µg Th g-1) and to a lesser extent to the fraction of garnet (5 µg Th g-1). The zircon fraction also contained 5076 µg Hf g-1. Some minerals and elements (Ti, Zr, Hf, Th, U) contained in the black sand could be of potential economic value. The high proportions of monomineralic grains along with the variations observed in mineral phases, in colour, in sphericity, in roundness, in grain size, in composition and in mineral inclusions, imply that the minerals and grains were subjected to several cycles of weathering and sedimentation, as well as being derived from multiple source rocks and areas. 相似文献
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广东南山花岗岩体位于陂头复式岩体西端,锆石的SHRIMP U-Pb年龄为158.1±1.8Ma,是燕山早期岩浆活动的产物.岩石化学特征显示岩体以高硅、富碱、贫Ca和Mg以及高TFeO/MgO、低CaO/Na2O为特征.其K2O/Na2O>1,A/NK=7.8~11.92,A/CNK=1.33~1.68,属过铝质碱性岩石.在稀土和微量元素组成上,岩石富含稀土元素(除明显的负Eu异常,δEu=0.09~0.16)以及Zr、Y、Th、U、Nb等高场强元素,贫Ba、Sr、Ti等,高10000x Ga/AI(比值大于2.6).在Zr、Nb、Ce、Y对10000×Ga/Al以及TFeO/MgO-SiO2等A型花岗岩多种判别图上,投影点主要落在A型花岗岩区,而与高分异的I、S型花岗岩明显不同.这些特征均指示,南山岩体具有铝质A型花岗岩的特点.通过Y-Nb-3Ga和Y-Nb-Ce构造环境判别图解将其进一步划分为A2型花岗岩,代表其形成于拉张的构造背景之下.本文在此研究基础上,认为南山花岗质岩浆可能形成于相对挤压的中侏罗世.而在晚侏罗世早期相对拉张的作用下,岩石圈减薄,软流圈地幔上涌,地壳的泥质岩和少量砂质岩受到幔源流体富集后发生部分熔融后上侵形成铝质A型花岗岩,且有较强的结晶分异作用. 相似文献
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采集太原市冬季大气细颗粒物(PM2.5),选取4周、4月、10月龄C57BL/6雌性小鼠,采用咽后壁滴注的方法用3mg/kg(体重)PM2.5暴露4周.此外,分别采集太原市、北京市、杭州市和广州市4个城市的冬季PM2.5,将10月龄小鼠暴露其中.采用荧光定量PCR技术检测心脏组织中细胞色素C氧化酶亚基I(co1)、IV(co4)和ATP合酶(ATP6)以及核转录因子pgc-1α、nrf1和tfam的mRNA转录水平.结果发现,太原市PM2.5暴露后,10月龄小鼠心脏组织中co1、co4和ATP6以及核转录因子pgc-1α、nrf1和tfam的mRNA水平与对照组相比均显著升高.但4周和4月龄小鼠中上述基因表达则未见明显差异.10月龄小鼠暴露于不同城市PM2.5后,杭州PM2.5暴露可引起小鼠心脏组织中co1、co4、ATP6、pgc-1α、tfam的mRNA表达上升.北京PM2.5暴露可引起小鼠心脏组织中co1、ATP6和tfam的mRNA表达显著上升;广州PM2.5暴露则未见上述任何基因表达的显著改变.研究表明,太原市PM2.5对易感小鼠心脏线粒体氧化磷酸化的影响最大,其次是杭州市和北京市,而广州市的影响最小. 相似文献
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hate would formed into middle molecular weight substances during the degradation process. 相似文献
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中国机动车行驶里程分布规律 总被引:11,自引:5,他引:6
机动车行驶里程是计算机动车尾气排放量的一个重要参数.对全国数百个地级及以上城市不同车龄的机动车(包括轻型客车、公交车、出租车和摩托车)行驶里程进行了调查.结果表明:除公交车外,其他机动车的累积行驶里程均随车龄而呈现对数递减性,即车龄越长机动车的累积行驶里程增加越慢,年使用率越小;某类型机动车车队的年均行驶里程与调查基准年的各车龄机动车的保有量相关;提出了轻型客车年行驶里程和车龄的经验公式,并得到2007年轻型客车的年均行驶里程为2.691×104km. 相似文献