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231.
W. Siebel K. Breiter I. Wendt A. Höhndorf F. Henjes-Kunst M. René 《Mineralogy and Petrology》1999,65(3-4):207-235
Summary Late-Variscan granitoid plutons in western Bohemia (Bor, Waidhaus-Rozvadov) have distinct petrographic, geochemical and isotopic features that suggest different magmatic evolutions. The Bor pluton comprises a suite of metaluminous tonalites and quartz diorites (Bor I), weakly peraluminous (monzo-)granites and granodiorites (Bor II) and medium-aluminous, late vein-forming leucomonzogranites (Bor III). The Waidhaus-Rozvadov pluton is strongly peraluminous, comprising a cordierite-biotite granitoid (CBG), the Rozvadov granite (ROG), the Bärnau granite (BÄG) and the subordinate, highly evolved Kreuzstein (Kíový kámen) granite (KG). Geochemical parameters and initial87Sr/86Sr ratios straddle the boundary between I- and S-type granites in the Bor pluton and are characteristic of purely S-type granites in the Waidhaus-Rozvadov pluton.The Bor II granitoids have been dated by the Rb-Sr whole-rock method at 341±17 Ma (ISr = 0.70724±0.00060). K-Ar biotite and muscovite ages of all units of the Bor pluton are mainly in the range 321-315 Ma. The K-Ar mineral ages are in good agreement with recently published U-Pb zircon data of these rocks. The different units of the Waidhaus-Rozvadov pluton have yielded less well-constrained Rb-Sr whole-rock ages, ranging from 313 to 300 Ma. However, the intrusion sequence is constrained by K-Ar muscovite ages (312-302 Ma), which define a systematic decrease towards the chemically more evolved granite types. Taken as a whole, it seems likely that the new radiometric ages characterize two temporally distinct periods of late-Variscan granitoid intrusion. The regional significance of these periods is emphasized by contemporaneous ages previously found in the adjacent northeastern Bavarian granitoids.The initial Sr and Nd isotope systematics indicate that the Bor and the WaidhausRozvadov plutons were derived from different source rocks. The Bor granitoids reflect the influence of less evolved crustal material which may have been similar to paragneisses of the Teplá-Barrandian region, including the Zone of ErbendorfVohenstrauß (ZEV). The Waidhaus-Rozvadov granitoids probably resulted from anatexis of rocks resembling surrounding Moldanubian paragneisses or metapelites. In addition, the two plutons exhibit poorly defined, opposite trends of Nd(T) variation which are ascribed to assimilation processes.
With 10 Figures 相似文献
Petrogenese kontrastierender Granitplutone in Westböhmen (Tschechien)
Zusammenfassung Spätvariscische Granitplutone in Westböhmen (Bor, Waidhaus-Rozvadov) weisen petrographische, geochemische und isotopische Kontraste auf, die unterschiedliche magmatische Entwicklungen nahelegen. Der Bor Pluton umfaßt metalumine Tonalite und Quarzdiorite (Bor I), schwach peralumine (Monzo-)granite und Granodiorite (Bor II) und mäßig alumine, gangbildende Leukomonzogranite (Bor III). Der WaidhausRozvadov Pluton besitzt stark peralumine Zusammensetzung und läßt sich in einen Cordierit-Biotit Granitoid (CBG), den Rozvadov Granit (ROG), den Bärnau Granit (BÄG) und den stofflich hochentwickelten Kreuzstein (Kíový kámen) Granit (KG) untergliedern. Geochemische Parameter und initiale87Sr/86Sr-Verhältnisse liegen im Falle des Bor Plutons im Übergangsbereich zwischen I- und S-Typ Graniten und im Falle des Waidhaus-Rozvadov Plutons im Bereich reiner S-Typ Granite.Die Bor II Granitoide wurden nach der Rb-Sr Gesamtgesteinsmethode auf 341±17 Ma (ISr = 0.70724±0.00060) datiert. K-Ar Biotit- und Muskovitalter der Bor Granitoide liegen zwischen 321 and 315 Ma. Die K-Ar Mineralalter stehen im Einklang mit den kürzlich publizierten U-Pb Zirkondaten dieser Gesteine. Die verschiedenen Teilintrusionen des Waidhaus-Rozvadov Plutons liefern weniger gut definierte Rb-Sr Gesamtgesteinsalter zwischen 313 and 300 Ma. Die Intrusionsabfolge läßt sich dennoch durch K-Ar Muskovitalter festlegen (312-302 Ma), die eine systematische Abnahme von den weniger zu den starker entwickelten Granittypen aufweisen. Als Ganzes betrachtet dokumentieren die neuen radiometrischen Daten zwei zeitlich voneinander getrennte spdtvariscische Intrusionsereignisse. Die regionale Signifikanz dieser Ereignisse wird durch eine analoge Altersverteilung in den benachbarten nordostbayerischen Granitoiden untermauert.Anhand der initialen Sr und Nd Isotopensystematik können für die Bor und Waidhaus-Rozvadov Plutone unterschiedliche Quellen abgeleitet werden. Die Bor Granitoide spiegeln den Einfluß von gering entwickelten krustalen Material wider, das ähnliche stoffliche Eigenschaften besaß, wie Paragneise des Teplá-Barrandiums und der Zone von Erbendorf-Vohenstrauss (ZEV). Die Waidhaus-Rozvadov Granitoide lassen sich als Derivate moldanubischer Paragneise and Metapelite oder vergleichbarer Gesteine auffassen. Die zwei Plutone weisen schwach ausgeprägte gegensätzliche Nd(T)-Variationen auf, was auf unterschiedliche Assimilationsprozesse zurückgeführt wird.
With 10 Figures 相似文献
232.
J. René Roy 《Solar physics》1973,28(1):95-114
High resolution on- and off-band Hα filtergrams of disk solar surges obtained with the Vacuum Tower Telescope of the Sacramento Peak Observatory have been compared to magnetic data.
- Surges constitute clusters of very fine dark (sometimes bright) filaments where each thread connects to an Ellerman bomb brightening. If the magnetic map reveals the existence of a satellite polarity as defined by Rust (1968), the bomb(s) lies over it.
- Although a large fraction of surges is not associated with clearly detectable satellite polarities, events are strongly favored in regions of evolving magnetic features, characterized by dimensions of about 10 000 km and significant flux change over a period of less than a day. A flux change rate of 3 × 1015 Mx s?1 has been measured along at least three homologous bomb-surge events in a satellite of region MW 18594. Surges appear to be related to rising flux of one polarity into a region of stronger opposite flux.
- The trajectories of surges are matched by magnetic lines of force computed in the current-free approximation.
233.
Aluminum in the macrotidal Yalujiang estuary: Partitioning of Al along the estuarine gradients and flux 总被引:1,自引:0,他引:1
Water samples were collected from the Yalujiang estuary in both flood periods (August 1992 and August 1994) and dry season (May 1996) and were analyzed for aluminum (Al). Al behaves non-conservatively in the Yalujiang estuary, and a significant loss (70–80%) in dissolved concentration is observed in the upper estuary, in spite of seasonal variation in water discharge and sediment load. About 0.4×106, tons of Al is annually transported from Yalujiang to the estuary, of which the particulate pool clearly dominates. The particulate Al flux through the Yalujiang contributes 35% of the total Al input from Chinese rivers to the Yellow Sea. The data sets from size fractionation and C-18 SPE separation demonstrate that a large fraction of dissolved Al is in colloidal (≈50%) and organically complex (≈60%) forms in the Yalujiang. The observed scavenging from solution to particulate pools in the estuary is most likely through the flocculation of colloidal and organic-complexed Al, which results in a considerable change in dissolved-particulate partitioning, shown by laboratory mixing experiments. Exchange between dissolved and particulate phases is examined by analysis of Kd, the distribution coefficient. The empirical relationship of Kd with chlorinity and suspended matter concentrations was investigated with field observations and model simulations. The model indicated that Kd values of Al are inversely related to the amount of total suspended matter, but Kd-chlorinity plots show different features between dry and flood seasons. 相似文献
234.
The distribution of some trace metals (Cu, Zn, Ni, Co,Fe, Mn) and of DOC over a particulate (> 1 m),a colloidal (size < 0.45 m and molecular weight > 10 kD) and an ultrafiltered fraction (< 10 kD)was determined at several sites on the Thur River,Switzerland, at various times of the year. Thecomplexation of Cu by strong ligands in theultrafiltrate and in the conventional filtrate (<0.45 m) was compared using a ligand-exchange/CSV method.The <0.45 m concentrations of Cu (from anaverage of 7 nM to 24 nM), Zn (<5–23 nM), Ni (5–13 nM),Co (1.5–3 nM) and Mn (7–92 nM)increased downstream. The major part of Cu, Zn, Niand Co usually occurred in the ultrafiltratefraction at all sites, whereas Fe and Mn were mostlyin the particulate fraction, under conditions of lowsuspended matter content (< 10 mg L-1) in theriver. The percentage of metal in the colloidalfraction, with respect to the 0.45-m filtrate,decreased in the order: Cu (median 11%) > Zn Ni(median 5–6%) > Mn Co (median < 5%). DOCalso consisted mostly of molecules in the < 10 kDrange.Cu was strongly complexed by natural organic ligandsin all filtrate and ultrafiltrate samples. A largepart of the strong Cu binding ligands consisted ofcompounds in the < 10 kD range, but colloidalligands with similar properties also occurred. Cu wasdistributed among the dissolved and the colloidalligands, roughly in proportion to organic carbon.The colloidal fraction (as defined here) did notincrease in its proportional amount downstream and wasonly of limited significance in transporting traceelements in the Thur River under low discharge conditions. 相似文献
235.
利用与现今地面有关的数字地形资料,确定了内蒙古河套裂谷带北翼狼山-色尔腾山的剥蚀面序列及其分布型式。始新世末期始发的裂谷作用导致该裂谷北翼在渐新世(E3)、中新世(N1)、上新世(N2)和第四纪(Q)发生了4幕区域性地面隆起和剥蚀作用,与裂谷盆地的4幕沉降和沉积作用相关联。区域性地面降起量和剥蚀作用的时间长度、流水侵蚀对局部地势的潜在影响、隆起和侵蚀速度的相对重要性,以及构造、侵蚀和均衡作用的联合效应是该裂谷翼部景观发育的主要控制因素。 相似文献
236.
237.
238.
Interdecadal variations in the frequency of typhoon affecting China (TAC) during 1951-2004 were investigated in this study. The yearly frequency of TACs showed a slightly increasing trend from the 1950s to the early 1970s and a significant decreasing trend afterwards. There were more TACs during the 1960s while the most inactive period was observed in recent 10 years. A decreasing trend was observed in the monthly frequency of TACs in June, August and September throughout the 54 years. Large interannual variabilities were apparent in yearly and monthly frequencies of TACs. 相似文献
239.
中国城市固体废弃物甲烷排放研究 总被引:2,自引:0,他引:2
The greenhouse effect of methane (CH4) is only inferior to that of carbon dioxide (CO2). As an important anthropogenic emission source, the calculation of the emission amount of CH4 from waste treatment in landfills plays an important role in compiling greenhouse gases inventory and in estimating the climate change effects caused by increasing of greenhouse gases. Based on the previous work, and according to the sampling and analysis on municipal solid waste (MSW) in typical cities, the degradable organic carbon (DOC) percentile was identified in typical cities in recent years. According to the IPCC greenhouse gases inventory guideline and default method of CH4 emission from MSW landfills, and in light of MSW managing situation in different regions, the amount of CH4 emission was calculated. The results show that the amount of CH4 emission decreases geographically from east to west and it increases temporally from 1994 to 2004 in China. 相似文献
240.
首先介绍了激光测距仪的发展历程,针对应用领域的不同,分别对3维激光成像仪和机载/星载激光测高仪的测量原理进行了阐述,并分别介绍了两种激光测距仪的工作流程以及数据处理流程,最后对两种激光测距仪的应用范围进行了阐述,并把两种激光测距技术和普通摄影测量进行了比较,指出了激光测距技术相对于普通摄影测量的优点,即高精度性、穿透性、实时性。 相似文献