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1.
CHRIS W. LEE 《Geology Today》1991,7(4):133-136
Each year many hundreds, if not thousands, of Earth-science students visit the coastline at Ogmore-by-Sea, mid-Glamorgan. They study the excellent exposures of Lower Carboniferous Limestone, with their well-preserved coral and other shelly faunas, together with the presumed late Triassic 'breccias'* that rest unconformably on top. A study of the cements within the breccias may give an insight into syndepositional mineralization and the formation of sedimentary basins linked to the opening of the Atlantic in early Mesozoic times. 相似文献
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为了支持玩具业,许多实验室需要分析各种复杂基体中的金属含量。人们关心的主要元素是铅,但很多其他有毒元素也具有潜在的威胁,尤其对于儿童。这些重金属元素包括锑、砷、钡、镉、铬、硒、汞和铅,累积在人体中将产生不利的影响。一些塑料和木制玩具,特别是表面色彩鲜艳的玩具被证实含有更高水平的铅和其他元素,儿童因接触易摄入,相关法规对产品表面含有这些元素的材料作了一些限制。为了保证玩具和其他物品的生产、流通和销售,有必要检测其中的重金属含量。不同的管理机构对各类样品中的元素提供了限量要求。在玩具安全性的欧洲标准EN71第3部分(已纳入ISO8124-3),其中在“特定元素的迁移”一节给出了玩具材料中元素迁移的 相似文献
4.
In this study, long-term (1777–1997) precipitation data for Seoul, Korea, wetness indices from eastern China, and modern observations are used to identify the interdecadal variability in East Asian summer monsoon precipitation over the last 220 years. In the East Asian monsoon region, two long-term timescales of dry–wet transitions for the interdecadal variability and quasi-40-and quasi-60-year timescales are dominant in the 220-year precipitation data of Seoul, as well as in the wetness indices over China.... 相似文献
5.
大兴安岭中生代两类流纹岩与玄武岩的成因联系 总被引:2,自引:0,他引:2
根据地质产状和地球化学特征大兴安岭中生代流纹岩类可划分为高Ti流纹岩和低Ti流纹岩。高Ti流纹岩类与亚碱性系列玄武岩类紧密伴生 ,两者在地球化学上构成连续变异系列。低Ti流纹岩类则与碱性系列玄武岩类构成地球化学双峰态。岩相学和地球化学研究表明 ,这两类流纹岩与该区同期玄武岩类有着密切的成因联系 :起源于地幔柱亏损成分的亚碱性系列玄武岩浆经过单斜辉石、斜长石、磷灰石、锆石的分离结晶 ,形成亚碱性系列低钾玄武岩→高钾玄武岩→高Ti流纹岩演化系列 ;起源于地幔柱富集成分的碱性系列玄武岩浆侵入下地壳 ,使下地壳岩石发生部分熔融 ,形成碱性系列玄武岩 -低Ti流纹岩双峰态组合 相似文献
6.
Eleven years ago when this society held its Third General Meeting I had the opportunity of calling your attention to certain strange deposits and topographical features that came under my notice in certain parts of North China. I showed you a number of striated boulders that could not be attributed to mere 相似文献
7.
In general, geologically speaking, it has been noted that if the formation of coal took place during the Permo-Carboniferous period, its volatile matter will al ways be less than 30% when analized, and the contrary is usually the case for coal created during the Tertiary and Jurassic, these having more than 40%. 相似文献
8.
MARK D. JOHNSON DAVID M. MICKELSON LEE CLAYTON JOHN W. ATTIG 《Boreas: An International Journal of Quaternary Research》1995,24(2):97-116
Glacial hummocks associated with the Superior Lobe in western Wisconsin are stagnant-ice features composed of melt-out till, meltwater-stream sediment, and flow till. The greater proportion of melt-out till in these hummocks than in hummocks described elsewhere suggests that a model of extensive, supraglacial reworking of supraglacially released debris does not apply to the western Wisconsin hummocks. Interpretation of melt-out till in hummock exposures is based on its strong fabric oriented parallel to regional ice-flow direction. Other features of this melt-out till include poorly developed stratification (color banding and discontinuous thin sandy lenses), and minor faulting, both of which support a melt-out origin. We suggest that as stagnant, debris-rich ice began to melt, supraglacially released debris was deposited as flow till and meltwater-stream sediment (with some debris-flow sediment and lake sediment), but as the thickness of supraglacial debris increased, debris melting out at depth was stabilized, allowing features characteristic of melt-out till to be retained. Because the supraglacial debris was sandy and the stagnant ice was likely at the pressure-melting point, the supraglacial debris was well drained and did not readily fail and flow. Debris volume in the glacier generally was greater at the glacier margin, but lateral and longitudinal variations within this zone were caused by thrusting, freezing-on, or ice-margin fluctuations, which in turn resulted in variations in hummock relief. Ice-walled-lake plains are commonly associated with the hummocks and developed where debris volume was small. 相似文献
9.
The senior author has, since several years,~1 pointed out the high magnesian content in the upper Wutai formation in which frequently occur 相似文献
10.
Ⅰ. GENERAL DESCRIPTION. This meteorite is obtained from the province of Kiangsu. The weight is about 82 grams. The specific gravity is 3. 6. The shape is conical. This conical shape is evidently due to the atmospheric pressure which exerts 相似文献