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991.
992.
造盆作用及成矿盆地的历史动力综合分类建议 总被引:3,自引:0,他引:3
本文把历史分析方法与动力分析方法两种分折方法结合起来,提出了一个综合的盆地分类方案。按历史动力综合分类,造盆作用及盆地可划分为三大类:大洋壳型、雏陆壳(过渡壳)型及大陆壳型大壳型中可细分为活动区型及稳定区型。雏陆壳型包括前地槽型及地槽前期型。大陆壳型中计有地槽后期型、地台型和地洼型。 相似文献
993.
燧石和脉石英中氩,氯的相关性对^40Ar—^39Ar定年意义 总被引:5,自引:1,他引:5
由于过剩Ar的存在,长期以来燧石和脉石英的^40Ar-^39Ar定年被视为不可能。通过对这类矿物中Ar,Cl丰度及其相关性研究,可以校正过剩Ar,从而实现了这类矿物的年龄测定,这为沉积岩定年及成矿时代的研究提供了重要手段,应用这一技术测得长城系底砾岩中石英年龄为1744±97Ma,滹沱群郭家寨亚群热事件年龄为1766±49Ma,进而推断长城系与郭家寨亚群的层位呈上下系。 相似文献
994.
M_(17)树脂在>6mol/L的HCl介质中能同时吸附Se和Te,Se和Te可用水和丙酮分别洗脱,也可用丙酮同时洗脱。从而建立了两个新的Se、Te分离富集体系,使原子荧光测定达到纳克量级。 相似文献
995.
Trace Elements and Sr, Nd Isotope Geochemistry of the Lajimiao Norite-Gabbro from the North Qinling Belt 总被引:1,自引:0,他引:1
S.R.Hart 《《地质学报》英文版》1994,68(2)
The Lajimiao norite-gabbro complex, as a part of the ophiolites on the southern side of the North Qinling belt, consists of gabbro and norite-gabbro. They were derived from different magma series: the gabbro was derived from tholeiitic magma series with higher TiO2, REE abundance and Fe3+/Fe2+ ratio ; norite-gabbro was derived from calc-alkali magma series with lower TiO2, Fe3+/Fe2+ ratio and REE abundance and much lower HREE abundance, which suggests that the source of the norite-gabbro magma was deeper and controlled by eclogite facies. Geochemical characteristics of both plutonic rocks are similar to those of island-arc basalts, such as relatively high contents of Ba, Pb and Sr and relatively low contents of Nb, Zr and N j.The Sr, Nd isotopic characteristics of the Lajimiao norite-gabbro complex are similar to those of ophiolites. Its εNd values are constant, about+2; whereas εst values have wide variation from - 6.4 to +31.2 and positively correlate with Na2O, H2O+ and CO2 contents and the Fe3+/Fe 相似文献
996.
福建省上杭县罗卜岭斑岩型铜(钼)矿床地质特征 总被引:1,自引:0,他引:1
罗卜岭异常区处于成矿有利部位,本文通过对该区的热液蚀变分带、岩石化学特征、包裹体特征等的初步研究以及对化探异常进行深部验证,认为罗卜岭异常区存在着斑岩型铜(钼)矿床,是寻找斑岩型铜(钼)矿床的有利靶区。 相似文献
997.
On the significance of CO2 inclusions in plagioclase microphenocrysts in tholeiite from Moeraki,New Zealand 总被引:1,自引:0,他引:1
Liquid plus vapour inclusions of CO2 are widespread in plagioclase microphenocrysts in small tholeiitic intrusions and tephra of the Moeraki and adjacent areas
of northeast Otago, New Zealand. They imply the presence of immiscible CO2 droplets in the magma at depths of about 7–14 km. Their presence within 5 μm of the edges of microphenocrysts as little as
35 μm thick and 118 μm long indicates minimal feldspar crystal growth during the final ascent and quenching of the magma.
Delicate branching clusters of lath-like microphenocrysts escaped disruption during this ascent. Such CO2 inclusions are a potential source of ‘excess argon’ perturbing K-Ar age determinations.
Received March 24, 1993/Accepted September 10, 1993 相似文献
998.
Christian Werner 《地球表面变化过程与地形》1994,19(8):747-762
Every basin of higher than first order is drained by a channel network composed of two subnetworks. Their basins are separated by a drainage divide line, called the basin divider, which is the primary organizing feature of the main basin. Each basin of magnitude n contains n – 1 subnetworks of higher order, and is therefore organized by a set of n – 1 dividers. The dividers and the basin boundary are interconnected in a graph called the divider network of the basin; in graph-theoretic terms this network forms a tree and has the same magnitude and link numbers as the channel network draining the basin. While the subbasins and subnetworks of a drainage basin form a nesting hierarchy, the corresponding dividers do not; indeed, any two dividers share at most one node in common, and whether they do so is independent of whether the corresponding subbasins are nesting or disjoint. However, the dividers of nesting basins are linked by recursive relationships which permit the derivation of a set of algebraic equations; these equations relate the dividers of a basin to other basin components; for example, their combined length is equal to half the length of all first-order basin boundaries minus the length of the main basin boundary. The second part of the paper explores the dependence of the divider length on other basin parameters. The expected length, as predicted by the assumption of topological randomness, is clearly rejected by the data. An alternative approach (regression) is based on the observed magnitudes of the subbasins separated by each divider, and is reasonably successful in estimating divider length. The last section introduces the concept of the standardized basin defined by a boundary length of unity; the estimated lengths of the basin divider and the basin boundary permit an approximate reconstruction of the idealized basin shape and the location of the divider in it. 相似文献
999.
1000.