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41.
Tectonic Units and Their Fundamental Characteristics on the Northern Margin of the Alxa Block 总被引:6,自引:0,他引:6
Wu Tairan Geology Department China University of Geosciences Beijing He Guoqi Geology Department Peking University Jiang Minxi 《《地质学报》英文版》1993,67(4)
The northern margin of the Alxa block is the junction of a tectonic units. Four first-order tectonic units are distinguished: 1. the Yagan structural zone characteristic of an immature island arc; 2. the Zhusileng-Hangwula structural zone, which was a passive continental margin in the Early Palaeozoic and was transformed into an active continental margin in the Late Palaeozoic;3. the Shalazha structural zone characteristic of a mature island arc; 4. the Nuru-Langshan structural zone, which was a Proterozoic orogenic belt and later evolved into an extensional transtional crust in the Palaeozoic. The above-mentioned tectonic units differ remarkably in sedimentary formations, magmatic rock associations, metamorphism and geochemistry and are bounded by faults between one another. 相似文献
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Relationships between riverbed morphology, concavity, rock type and rock uplift rate are examined to independently unravel the contribution of along-strike variations in lithology and rates of vertical deformation to the topographic relief of the Oregon coastal mountains. Lithologic control on river profile form is reflected by convexities and knickpoints in a number of longitudinal profiles and by general trends of concavity as a function of lithology. Volcanic and sedimentary rocks are the principal rock types underlying the northern Oregon Coast Ranges (between 46°30′ and 45°N) where mixed bedrock–alluvial channels dominate. Average concavity, θ, is 0·57 in this region. In the alluviated central Oregon Coast Ranges (between 45° and 44°N) values of concavity are, on average, the highest (θ = 0·82). South of 44°N, however, bedrock channels are common and θ = 0·73. Mixed bedrock–alluvial channels characterize rivers in the Klamath Mountains (from 43°N south; θ = 0·64). Rock uplift rates of ≥0·5 mm a−1, mixed bedrock–alluvial channels, and concavities of 0·53–0·70 occur within the northernmost Coast Ranges and Klamath Mountains. For rivers flowing over volcanic rocks θ = 0·53, and θ = 0·72 for reaches crossing sedimentary rocks. Whereas channel type and concavity generally co-vary with lithology along much of the range, rivers between 44·5° and 43°N do not follow these trends. Concavities are generally greater than 0·70, alluvial channels are common, and river profiles lack knickpoints between 44·5° and 44°N, despite the fact that lithology is arguably invariant. Moreover, rock uplift rates in this region vary from low, ≤0·5 mm a−1, to subsidence (<0 mm a−1). These observations are consistent with models of transient river response to a decrease in uplift rate. Conversely, the rivers between 44° and 43°N have similar concavities and flow on the same mapped bedrock unit as the central region, but have bedrock channels and irregular longitudinal profiles, suggesting the river profiles reflect a transient response to an increase in uplift rate. If changes in rock uplift rate explain the differences in river profile form and morphology, it is unlikely that rock uplift and erosion are in steady state in the Oregon coastal mountains. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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通过因子分析、相关分析和聚类分析,研究了巴彦温多尔金矿矿石和围岩样品12种元素的组合特征。结果显示,矿石中金与其他11种元素的相关程度很低,而围岩中金与银有较强的相关性。围岩和矿石的元素组合也有明显差别,围岩样品代表控矿构造带的矿化背景,矿石样品代表成矿时的元素组合。 相似文献
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磁力勘探与岩性测深理论基础的对比 总被引:1,自引:0,他引:1
首先概括了岩性测深技术的理论基础和物性基础要点,强调电偶极子场是岩性测深技术的基本理论。然后通过电偶极子场与磁偶极子场的类比,以及岩性测深与磁力勘探的对比,提出了一条研究岩性测深技术理论基础及正演计算的思路。 相似文献
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交会图和Carbon软件在火山碎屑岩识别中的应用 总被引:1,自引:0,他引:1
针对火山岩储层的特殊性(复杂性、离散性和随机性),应用交会图及Carbon软件对火山岩测井解释中岩性识别问题进行了研究。该方法的技术关键是交会图的选取,以交会图和Carbon软件为基础实现对岩性的识别。将研究方法应用在海拉尔地区火山碎屑岩岩性识别问题中,取得了很好的效果,岩性解释符合率80%。 相似文献