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341.
342.
青岛青山湾—垭口出露一套浅变质的海相陆缘碎屑沉积岩,上覆岩浆锆石的LA-ICP-MS U-Pb年龄为(118.9±3.3)Ma,成熟度较低,与中新生代造山带砂岩类似。稀土元素球粒陨石化标准配分曲线均为轻稀土明显富集的右倾型,表明,研究区碎屑岩具有相同的物源区和构造背景,与活动陆缘的稀土元素配分曲线非常接近。Ce具弱的负异常,指示碎屑岩为大陆边缘海相成因,(La/Ce)N(PAAS)表明陆缘碎屑物质对该区碎屑岩有明显的贡献。主微量元素构造环境判别图解表明,研究区碎屑岩具有活动陆缘和大陆岛弧的特征,经历了相对简单的沉积演化过程;结合稀土元素配分曲线的特征,该区碎屑岩更可能是活动大陆边缘沉积形成。主微量元素分析揭示研究区碎屑岩物源富长英质岩石,镁铁质岩石作为物源也参与到成岩过程中。 相似文献
343.
基于2001—2018年长时间序列地表水遥感监测数据,提取中亚五国地表水面积信息,通过动态度法、变化斜率法和相关分析法揭示中亚五国地表水面积的时空动态变化特征并对其进行驱动力分析。结果表明:① 中亚五国地表水呈“北密南疏”分布特征,中北部地表水变化明显。近18 a来,季节水面积呈显著增加趋势,增加了133.55%,而永久水呈波动减少趋势,减少了17.27%。哈萨克斯坦地表水面积占比最大且变化也最为明显,其次是乌兹别克斯坦,其余三国无较大变化。② 2001—2018年,中亚五国全区季节水动态度为7.42%,并呈快-慢-快的增长趋势,而永久水呈增长-下降-增长的演变趋势,乌兹别克斯坦地表水变化最为活跃;北部边缘及图尔盖洼地、西部里海沿岸和咸海地区永久水面积显著减少而季节水显著增加,永久水向季节水转换现象明显。③ 中亚五国增温趋势不明显,降水呈减少趋势,人口、GDP和耕地均呈增加趋势。中亚五国地表水面积变化主要受社会经济因子的影响,气候因子对地表水的影响不显著。 相似文献
344.
马家疃金矿区位于胶东著名的台前-陡崖金成矿带上盘,笏山、西陡崖金矿床东邻。笏山、西陡崖矿区已累计提交金资源储量30余吨,其主矿体倾向深部,向马家疃矿区延伸稳定。区内地层出露单一,岩浆岩发育,矿体产出于玲珑花岗岩体中,严格受NNE向压扭性断裂控制,矿石类型主要为黄铁绢英岩化碎裂岩。通过对矿床地质特征及矿床成因的分析,其深部有较大的找矿前景,在总结成矿规律的基础上,围绕有利构造部位进一步勘查,有望实现栖霞地区找矿的再次突破。 相似文献
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346.
G. H. F. Young R. J. Bale N. J. Loader D. Mccarroll N. Nayling N. Vousden 《第四纪科学杂志》2012,27(6):606-614
In regions with seasonal temperate climatic regimes, tree growth is rarely controlled by any single environmental factor. As a consequence, the development of robust palaeoclimate reconstructions has proved challenging. Tree‐ring stable carbon isotope ratios (δ13C), however, are controlled primarily by photosynthetic rate, not by net growth. Therefore, at sites where climatic controls on tree‐ring growth are not strongly expressed, a robust (isotopic) palaeoclimate signal may still potentially be preserved. This hypothesis was tested using a 160‐year record of δ13C measured from the pooled latewood cellulose of six Quercus petraea L. (sessile oak) trees from Allt Lan‐las in West Wales, UK. Raw δ13C values were corrected for changes in the isotopic ratio of atmospheric carbon dioxide and for changes in the behaviour of trees due to the increasing availability of atmospheric CO2 since AD 1850. Strong correlations with local summer temperature and sunshine are reported, and also with the Central England Temperature record over the full length of the isotopic chronology (AD 1850–2010) (r = 0.69, P < 0.001). We conclude that tree‐ring stable isotopes can be used to extract strong palaeoclimate signals even from oak trees growing in a temperate maritime climate. This demonstrates the potential for extracting robust palaeoclimatic information from the very long and well‐replicated oak chronologies which have been developed in western and central Europe primarily for dating rather than palaeoclimatic research purposes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
347.
A. Correa‐Metrio S. Lozano‐García S. Xelhuantzi‐López S. Sosa‐Nájera S. E. Metcalfe 《第四纪科学杂志》2012,27(5):509-518
The late glacial and the transition towards the Holocene marked a period of significant environmental change at a global scale. In western Central Mexico, few records span beyond the Holocene, and little is known about Pleistocene climatic and environmental variability. Here we report on the pollen record of a composite sequence made of three cores that cover the last 50 ka (thousands of calibrated radiocarbon years before present) in the Zacapu Basin, western Central Mexico (~1970 m asl). The conjunction of modern pollen rain from the area with the composite fossil pollen sequence from cores Cantabria, Cantabria 1 and CEMCA Point‐1 provided a detailed history of the vegetation of the area. Recognition of modern environmental patterns through individual modern pollen taxa proved difficult, but multivariate analysis separated different vegetation types. No‐modern‐analog communities relative to the modern vegetation cover of the area were evident, especially during periods of drought. Apparently, summer precipitation was significant before 40 ka and after the deglaciation. However, this moisture source declined from ~40 to 10 ka because tradewinds from the Gulf of Mexico were blocked by the eastern mountains of Central Mexico as a result of lower temperatures. By contrast, westerly and northerly winds were enhanced by maximum ice cover from ~19 to 17 ka, providing abundant winter precipitation and therefore preventing extreme drought in the area. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
348.
近年来,随着济宁、枣庄地区煤矿资源的大规模开发,矿坑排水对矿区地下水资源及生态环境产生的负面影响愈发突出,已逐步引起政府和社会有关部门的关注.本文是在全面调查区内矿山基本情况。矿坑排水水量、水质的基础上,进行了矿坑水水处理方法的探索.指出了矿坑排水合理开发利用方向.并提出了综合利用规划建议。 相似文献
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350.
V. GARDIEN M. TEGYEY J. M. LARDEAUX M. MISSERI E. DUFOUR 《Journal of Metamorphic Geology》1990,8(5):477-492
Garnet lherzolite from the Lyonnais area (eastern French Massif Central) occurs as several lenses elongated within the regional foliation of garnet-biotite-sillimanite gneisses. Within the peridotites a mylonitic foliation can be observed which clearly is oblique to the regional foliation of the surrounding gneisses. Petrological and thermobarometric studies emphasize a tectonometamorphic re-equilibration for both crustal and mantle rocks characterized by a prograde metamorphic stage followed by retrograde evolution. During the burial stage, interpreted as lithospheric subduction, the peridotites underwent their mylonitic deformation, under high-pressure conditions (23–30 kbar). In contrast, the paragneisses have suffered their deformation during the retromorphic evolution under mesozonal conditions (6–8 kbar, 700°C). Our thermobarometric investigations allow us to interpret the granulitic/ultramafic association from the Monts du Lyonnais area as a lithospheric section buried into a Palaeozoic subduction zone, laminated during continental collision and uplifted by erosion processes. 相似文献