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611.
金沙江中段元古宙变质岩的Sm-Nd同位素年龄报道 总被引:3,自引:0,他引:3
金沙江中段的古老变质岩由多期变质的元古宙变质岩石单元组成。利用Sm-Nd同位素方法获得了雄松群二云母片岩全岩同位素等时线年龄1594Ma和1723Ma、2011Ma两组模式年龄。前者代表了成岩年龄,后者代表金沙江中段地层的基底年龄,这与金沙江流域乃至整个华南地壳最初形成的年龄十分相似。表明,川西、藏东地区雄松群变质岩可能属于华南地壳的组成部分。其形成时间应在早元古代或更早的时期内。 相似文献
612.
Bao Peisheng Wang Xibin Hao Ziguo Peng Genyong Institute of Geology Chinese Academy of Geological Sciences Beijing Fei Zhenbi 《《地质学报》英文版》1993,67(1)
Ultramafic rocks of Tibet and Xinjiang are the products of partial melting of the upper mantle. The evolution of their mineral composition is marked by two parallel evolutionary series: one is the progressive increase of the 100 Mg/(Mg+Fe~(2+) ratio of silicate minerals in order of lherzolite→harzburgite→dunite, i.e. the increase in magnesium; the other is the increase of the 100 Cr/(Cr+Al) ratio of accessory chrome spinel in the same order, i. e. the increase in Chromium. The above-mentioned evolutionary trends are contrary to that of magmatic differentiation. The evolution of fabrics of ultramafic rocks is characterized by progressive variation in order of protogranular texture→melted residual texture, symplectic texture and clastophyritic texture→equigranular mosaic texture and tabular mosaic texture. Experiments of partial melting of lherzolite have convincingly shown that the evolution of Alpine ultramafic rocks resulted from the partial melting of pyrolite. Various subtypes of them represent different degrees of partial melting. The vertical zoning marked by more basic rocks in the upper part and more acid rocks in the lower actually belongs to the fusion zoning of pyrolite. 相似文献
613.
笔者运用GC—MS方法,在广西百色盆地湖相暗色泥岩和原油的UNA组分中普遍检测到单环烷烃。经初步研究认为,此类化合物碳数组成与分布和典型海相有机质明显有别。同一样品中烷基环己烷、正构烷烃和一元正脂肪酸的碳数组成、分布的相似性为烷基环己烷源于脂肪酸提供了证据,因而此类化合物亦属生物标志化合物,是生源物输入和油源对比的潜在良好标志。 相似文献
614.
615.
616.
用补偿校正系数法校正X荧光光谱分析中基体效应的影响,对岩石中七个主量元素的测定结果表明该方法准确、可靠。 相似文献
617.
Comparison of eolian transport during five high-velocity wind events over a 29 day period on a narrow estuarine beach in Delaware Bay, New Jersey, USA, reveals the temporal variability of transport, due to changes in direction of wind approach. Mean wind speed measured 6 m above the dune crest for the five events ranged from 8·5 to 15·9 ms?1. Mean wind direction was oblique to the shoreline (63° from shore-normal) during one event but was within 14° of shore-normal during the other events. Eolian transport is greatest during low tide and rising tide, when the beach source area is widest and when drying of surface sediments occurs. The quantity of sediment caught in a vertical trap for the five events varied from a total of 0·07 to 113·73 kgm?1. Differences in temperature, relative humidity and moisture and salt content of surficial sediments were slight. Mean grain sizes ranged from 0·33 to 0·58 mm, causing slight differences in threshold shear velocity, but shear velocities exceeded the threshold required for transport during all events. Beach width, measured normal to the shoreline, varied from 15·5 to 18·0 m; beach slope differed by 0·5°. The oblique wind during one event created a source width nearly double the width during other days. Beach slope, measured in the direction of the wind, was less than half as steep as the slope measured normal to the shoreline. The amount of sand trapped during the oblique wind was over 20 times greater than any other event, even those with higher shear velocities. The ability of the beach surface to supply grains to the air stream is limited on narrow beaches, but increased source width, due to oblique wind approach, can partially overcome limitations of surface conditions on the beach. 相似文献
618.
Summary This paper presents an experimental study of the newly developed double-punch test method for determination of the tensile strength of rocks. The method for preparation of test specimens and test procedure is reported and discussed. Comparisons of tensile strength determined from double-punch and split-cylinder tests are also presented.With 5 Figures 相似文献
619.
IntroductionAfteramoderateorstronger(Ms25.0)earthquake,themosturgentworkofthedivisionforearthquakemonitoringandpredictionistodetermineitstimeoforigin,hypocentrallocation(longitude,latitudeanddepth)andmagnitudeandtojudgethetrendofseismicregimedevelopmentassoonaspossible.Ingeneralcases,whenanearthquakewithMS25.0insideChinaoraonewithMS26.0inneighboringareasofChinahasoccurred,theEarthquakeBulletinofChineseSeismologicalNetworkcanprovidedeterminationoftheorigintime,hypocentrallocation(longitude,… 相似文献
620.
Tempo-spatial rupture process of the 1997 Mani, Xizang (Tibet), China earthquake of MS=7.9 总被引:3,自引:0,他引:3
IntroductionAnearthquakeofMs=7.9occurredinMaul,Xizang(Tibet),Chinaat10:02f55.4(UTC),No')ember8.1997.TheepicenterdeterminedbyChinaNationalSeismographNetwork(CNSN)is87.33"E.3>.26'N,thefocaldepthis40km,andthemagnitudeisMs=7.4.Accordingtothedeterllllnati... 相似文献