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371.
High-resolution Givetian-Frasnian boundary recognition from conodont-chemo-stratigraphic correlation at Liujing, Guangxi, South China 总被引:1,自引:0,他引:1
The Givetian-Frasnian boundary at Liujing, Guangxi, South China is for the first time recognized and correlated in high resolution
using characteristic chemocycles of element abundance fluctuation integrated with conodont biostratignphy. The first appearance
of Ancyrodella rotundiloba early form is as a biomarker, and the boundary of lowering fluctuation of element abundance followed
by a sequence of characteristic chemocycles with a sequence of cmodonts is as an abiotic auxiliary marker. The error is not
more than 0.10 Ma. The study indicates that in a quiet interval, characteristic chemocycles integrated with biomarkers can
be used for boundary recognition and regional cormlation in high resolution, and this method has potential for intercontinental
correlation 相似文献
372.
373.
W.Q. Gan 《Astrophysics and Space Science》2000,274(3):481-488
Investigation of the gamma-ray spectra observed by the GRS/SMM leads to the conclusion that there exist two extreme cases:
electron-dominated spectra and proton-dominated spectra. The observation of different spectra is determined by both the spectral
hardness of non-thermal electrons and the number ratio of protons to electrons. Any viable acceleration mechanism should be
able to explain these differences in accelerating electrons versus protons.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
374.
Trace elements in cassiterite,including Ta,W,Fe,Mn,Ti,Zr,V,Sc,Si,Al,In,Ga,Ge,Be,Bi,Ag,Sb,As,Cu,Pb,Zn,Co and REE,have been studied by many workers (Shan Zhenhua etal.,1998;Huang Zhou Tianren et al.,1987;Wu Qingsheng et al.,1988;Hu Zening,1988,Li Zhong-qing 1988 Mingzhei et al.,1988;Wang Lihua et al.,1988;Liu Kanghuai,1990).Up to now,however,most of the previous studies are concerned with trace-element variations in cassiterites of different occurrences and colors from different types of ore deposits,Data concerning the modes of occurrence of these trace elements are rare,except for the contention that Nb-Ta,Fe^2 -Mn-Fe^3 and W-Fe^3 may substitute isomorphously for Sn as pointed out by Zhou Tianren et al.(1987) and Moller et al.(1988).In this paper we are concerned with the compositional characteristics as well as the modes of occurrence of trace elements in cassiterites from quartz veins and greisens in the Dupangling tin field,Guangxi,based on multivariate statistical analyses.Tin mineralization in the Dupangling area is found associated with the medium-to fine-grained protolithionite-albite granite(γ5^2b) and its outer contacts.Cassiterite occurs,with wolframite,both in quartz veins in the contact and in greisens within the granite.^1) Spatially,greisens become dominant over quartz veins in the contact andin greisens with the granite.^1)Spatialy,gresens become dominant over quartz veins in going from the contact to the interior of the granite and with increasing depth.The greisens are of various shapes.The vein-shaped and the sheet-shaped greisens at the top of the granie are rich in quartz and the chambered greiens always constitute rich ores and contain abundant topaz or mica.Genetically,Sn,W mineralizations associated with the protolithionite-albite granite(γ5^2b) are considered to have been formed from fluid melt derived from the ore-forming magma responsible for the granite(γ5^2b). 相似文献
375.
为恢复中拐凸起JL30井区上乌尔禾组碎屑岩储层沉积古环境和物源性质,探明它们对储层物性的影响,对上乌尔禾组13件细粒碎屑岩样品主微量元素及稀土元素进行了测试分析。结果显示,主微量元素丰度接近UCC平均丰度,稀土元素丰度变化大并且表现出明显的轻稀土元素富集及轻微的Eu负异常,指示物质成分来源于上地壳,且未发生大规模热液作用。剔除成岩蚀变作用影响后的Sr/Cu和∑LREE/∑HREE显示上乌尔禾组沉积期间为温暖湿润的气候,降水丰沛,Mg/Ca和Sr/Ba以及自生矿物中的氧化还原敏感元素U和Th的比值显示沉积水体属于富氧条件下的微咸水环境。古沉积环境控制了沉积相类型,影响着储层物性的优劣,受此影响,上乌尔禾组沉积环境从扇三角洲前缘水下分流河道向扇三角洲平原分流河道演变,整体表现为沉积物粒度逐渐变细的正旋回沉积,中间发育多套小旋回,形成了多套下储上盖组合,有利于油气成藏。La/Th- Hf母岩类型判别图和稀土元素特征显示母岩类型主要为长英质岩石及部分基性岩与长英质岩混合岩,古老沉积岩的贡献不大。La/Sc Ti/Zr判别图及稀土元素参数特征显示源区构造背景为大陆岛弧,类型为切割的岩浆弧。大陆岛弧活跃的构造运动促使研究区形成了“两凸一凹”地貌形态,为沉积物提供了可容空间,是扇三角洲沉积环境形成的基础;后期火山活动的停歇是上乌尔禾组碎屑岩沉积物形成的前提。 相似文献
376.
377.
378.
To analyze the genesis of Sr isotopes in groundwater of Hebei plain, time-accumulative effect of 87Sr/86Sr ratio was studied. It is shown that 87Sr/86Sr ratio increases with the increasing age and depth of groundwater and has a positive correlation to 4Heexc and a negative correlation to δ18O and δD. The groundwater is divided into three groups to discuss the relation between 87Sr/86Sr ratio and Sr2 content: ① moderate Sr2 content and higher 87Sr/86Sr ratio (water I); ② lower Sr2 content and higher 87Sr/86Sr ratio (water II); and ③ higher Sr2 content and lower 87Sr/86Sr ratio (water III), that is hot water. On the basis of integrated analysis, it was considered that ① the radiogenic Sr in the Quaternary groundwater (Q4-Q1) originates from weathering of silicate rich in Na and Rb, mainly from plagioclase; ② the radiogenic Sr of hot water in Huanghua port is attributed to carbonate disso- lution, with lower 87Sr/86Sr ratio and higher Sr/Na ratio; ③ the recharge area is laterally recharged by the groundwater flowing through igneous and metamorphic rocks, with moderate 87Sr/86Sr ratio. How- ever, the formation mechanism of Sr isotopes in Tertiary groundwater needs further studies. 相似文献
379.
A. N. Luk’yanov A. Yu. Karpechko V. A. Yushkov L. I. Korshunov S. M. Khaikin A. V. Gan’shin E. Kyro R. Kivi M. Maturilli H. Voemel 《Izvestiya Atmospheric and Oceanic Physics》2009,45(3):294-301
Processes of mass exchange through the tropopause at extratropical latitudes are studied. For this purpose, balloon data on ozone and water vapor obtained during the LAUTLOS field campaign were analyzed and a trajectory model was used to analyze the origin of air masses and to calculate fluxes through the tropopause. The results of observations and trajectory modeling showed that tropospheric air masses penetrated into the stratosphere by no more than ~2.5 km above the tropopause level during the campaign. Both tropospheric and stratospheric particles are present in this mixing layer. Backward trajectories showed that, at the anticyclone boundary, tropospheric air penetrates into the stratosphere in the form of fine fibrous structures (filaments). The fluxes through the tropopause were also quantitatively estimated by the Wei method with the use of forward and backward trajectories. The spatial structure of the fluxes through the tropopause coincides with the regions of the tropopause inclination and its folds. The absolute values of the fluxes calculated with the use of the Wei method decrease, depending on the length of trajectories at the expense of the filtering-out of a shallow reversible exchange. It is shown that the exchange depth can be controlled by both vertical fluxes in the troposphere and changes in the level of the tropopause itself. The use of isentropic and three-dimensional trajectories made it possible to estimate the contribution of nonadiabatic processes to the stratosphere-troposphere exchange. 相似文献
380.
国有企业改革的目标是建立现代企业制度,而随着改革的逐步深化,事业单位改革已成为重要课题,也是测绘事业单位的必然选择。 相似文献