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排序方式： 共有67条查询结果，搜索用时 629 毫秒
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The technique of linear parametric programming has been applied to derive sets of internally consistent thermodynamic data for 21 condensed phases of the quaternary system CaO-Al2O3-SiO2-H2O (CASH) (Table 4). This was achieved by simultaneously processing:
- calorimetric data for 16 of these phases (Table 1), and
- experimental phase equilibria reversal brackets for 27 reactions (Table 3) involving these phases.
3.
Cosmas Kongnyuy Shang Muharrem Satir Emmanuel Nkonguin Nsifa Jean-Paul Liégeois Wolfgang Siebel Heiner Taubald 《International Journal of Earth Sciences》2007,96(5):817-841
We present a geochemical and isotopic study that, consistent with observed field relations, suggest Sangmelima late Archaean
high-K granite was derived by partial melting of older Archaean TTG. The TTG formations are sodic-trondhjemitic, showing calcic
and calc-alkalic trends and are metaluminous to peraluminous. High-K granites in contrast show a potassic calc-alkaline affinity
that spans the calcic, calc-alkalic, alkali-calcic and alkalic compositions. The two rock groups (TTG and high-K granites)
on the other hand are both ferroan and magnesian. They have a similar degree of fractionation for LREE but a different one
for HREE. Nd model ages and Sr/Y ratios define Mesoarchaean and slab-mantle derived magma compositions respectively, with
Nb and Ti anomalies indicating a subduction setting for the TTG. Major and trace element in addition to Sr and Nd isotopic
compositions support field observations that indicate the derivation of the high-K granitic group from the partial melting
of the older TTG equivalent at depth. Geochemical characteristics of the high-K granitic group are therefore inherited features
from the TTG protolith and cannot be used for determining their tectonic setting. The heat budget required for TTG partial
melting is ascribed to the upwelling of the mantle marked by a doleritic event of identical age as the generated high-K granite
melts. The cause of this upwelling is related to linear delamination along mega-shear zones in an intracontinental setting. 相似文献
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Zusammenfassung Nach einer kurzen Erläuterung der Erkennungsmöglichkeit einfacher Kristallformen zur Unterscheidung von Hoch-und Tiefquarz wird das Auftreten von eindeutigen Würfelquarzen (Rhomboeder), und damit von Tiefquarzen, in Rhyolithen (Quarzkeratophyren) des südlichen Rheinischen Schiefergebirges (Bundesrepublik Deutschland) beschrieben. Diese Quarzrhomboeder-führenden Vulkanite lassen sich petrographisch wie auch chemisch von den übrigen Rhyolithtypen jenes Gebietes unterscheiden. Eine eindeutige genetische Aussage zur Bildung dieser Tiefquarze in einem Vulkanit ist nicht zu machen, es werden dazu zwei alternative Modelle vorgestellt.
Mit 6 Abbildungen 相似文献
Pseudo-cubic quartz crystals of magmatic origin in rhyolites (quartz keratophyres) from the Rheinisches schiefergebirge
Summary Recognition of simple crystal forms for the distinction between high-and low-quartz is briefly outlined. Pseudo-cubic crystals of low-quartz are described from rhyolitic rocks (quartz keratophyres) of the southern Rheinisch Mountains (Federal Republic of Germany). These volcanics, carrying idiomorphic quartz rhombohedrons, can be distinguished by petrographic as well as by chemical means from the other rhyolites in that area. However, there is no decisive genetic solution to the origin of low-quartz in those volcanic rocks. Two alternative models are proposed.
Mit 6 Abbildungen 相似文献
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Cokriging is applied to the estimation of mineral resources in a polymetallic deposit. Several major steps, which should be taken in using cokriging, are highlighted as necessary practical considerations. The case study is related to an ultramafic copper-nickel deposit. Six elements, Cu, Ni, Au, Ag, Pt, and Pd, occurring in the deposit, are partitioned into three subgroups and the elements within each group are simultaneously estimated on the basis of over 4000 drill assays. A comparison was made between ordinary kriging and cokriging methods through cross-validation. The results show that cokriging has significantly improved the estimates of resources by reducing the overall estimation error by over 15% and the variance of error by over 20%. 相似文献
8.
Holger Steffen Olga Gitlein Heiner Denker Jürgen Müller Ludger Timmen 《Tectonophysics》2009,474(1-2):69
Fennoscandia is a key region for studying effects of glacial isostatic adjustment. The associated mass variations can be detected by the Gravity Recovery and Climate Experiment (GRACE) satellite mission, which observes the Earth's gravity field since April 2002, as well as by absolute gravimetry field campaigns. Since 2003, annual absolute gravity (AG) measurements have been performed in Fennoscandia by the Institut für Erdmessung (IfE, Institute of Geodesy) of the Leibniz Universität Hannover, Germany, within a multi-national cooperation. This offers a unique opportunity for validation and evaluation of the GRACE results. In this preliminary study, the GRACE results are compared to secular gravity changes based on the surveys from 2004 to 2007 with the FG5-220 gravimeter of the IfE.The results from GRACE monthly solutions provided by different analysis centres show temporal gravity variations in Fennoscandia. The included secular variations are in good agreement with former studies. The uplift centre is located west of the Bothnian Bay, the whole uplift area comprises Northern Europe. Nevertheless, the differences between the GRACE solutions are larger than expected and the different centre-specific processing techniques have a very strong effect on possible interpretations of GRACE results. The comparison of GRACE to the AG measurements reveals that the determined trends fit well with results from GRACE at selected stations, especially for the solution provided by the GFZ. Variations of land hydrology clearly influence results from GRACE and the AG measurements. 相似文献
9.
A two-step free-positioned point mass method is used for regional gravity field modeling together with the remove-compute-restore (RCR) technique. The Quasi-Newton algorithm (L-BFGS-B) is implemented to solve the nonlinear problem with bound constraints in the first step, while in the second step the magnitudes of the point masses are re-adjusted with known positions in the least-squares sense. In order to reach a good representation of the gravity field, a number of parameter sets have to be defined carefully before the computations. The effects of four important parameter sets (depth limits, number of point masses, original/reduced basis functions and optimization directions) are investigated for regional gravity field modeling based on two numerical test cases with synthetic and real data. The results show that the selection of the initial depth and depth limits is of most importance. The number of point masses for obtaining a good fit is affected by the data distribution, while a dependency on the data variability (signal variation) is negligible. Long-wavelength errors in the predicted height anomalies can be reduced significantly by using reduced basis functions, and the radial-direction optimization proves to be stable and reliable for regular and irregular data scenarios. If the parameter sets are defined properly, the solutions are similar to the ones computed by least-squares collocation (LSC), but require fewer unknowns than LSC. 相似文献
10.