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呷村多金属矿床是典型的海相火山热液一喷气沉积块状硫化物矿床。它具明显的垂向分带性,自下而上依次为铅锌矿带、铜铅锌银矿带和重晶石矿带,类似于日本黑矿型矿床的黄矿带、黑矿带和重晶石矿带。下部矿石主要呈粒状结构,脉状、网脉状构造;上部矿石常呈胶状、草莓状结构,块状、条带状、层纹状构造.围岩蚀变在铅锌矿带及其下伏火山岩中非常发育,而在上部块状矿层中却十分微弱。按蚀变的种类和强度,矿区分五个蚀变带。cu、Pb、Zn、Ag、Au、S、Ba等元素含量在含矿带内有随层位升高而增大的变化规律。研究表明,成矿溶液的温度、物质成份、fO_2、pH值,以及围岩岩性等因素控制呷村矿床的垂向分带。 相似文献
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斜长石环带的成因机制 总被引:1,自引:0,他引:1
系统地分析了外长石环带的研究现状,并提出了外长石的小尺度韵律环带起因于自组织过程,而与环境因素无关,其形成对应着相对静态的环境;斜长石的大尺度韵律环带刚起因于环境(主要是温度、压力)的“周期性”波动,而不可能是自组织成因,其形成过程记录了环带生长期间岩浆活动的情况(岩浆的温度、压力、组分浓度等)。斜长石的小尺度韵律环带是在结晶五度稳定在国相线附近的温度范围内形成的。当结晶温度低于团相线温度时,则形成非韵律环带或枝晶甚至玻璃体;非韵律型环带是由于环境的温度或压力的持续变化而形成的,它的结晶温度比大环带中套小环带形成时的结晶温度要低一些,或者说其非平衡程度更大一些。 相似文献
215.
Brad Gilmour Ted Huffman Andy Terauds Charles Jefferson 《Journal of Agricultural and Environmental Ethics》1996,9(1):16-41
The specific issue addressed in this paper is urban encroachment on agricultural lands, and the problems it poses for both analysis and the conservation of the land resource. The purpose of our discussion is two-fold: (1) to identify where and why traditional analytical and regulatory approaches fail to resolve land use conflicts, and (2) to explore ways and means of resolving some of the dilemmas which society faces in making land use decisions. This paper's contribution is in the spirit of Getting Incentives Right for the inter-temporal transfer of wealth, as represented in trade-offs between environmental and resource endowments and human and physical capital. Efforts are placed on identifying what the appropriate price, levy, taxes, and grant ratios ought to be in order to encourage individuals in the marketplace to act in society's interest. We have also explored ways of efficiently transmitting those incentives through the market mechanism, without unduly relying on bureaucratic methods or suasion. Emphasis is placed on mechanisms that have little scope for preferential access and are subject to public scrutiny; emphasis on such self-disciplining approaches should result in less effort expended on (unproductive) lobbying activities and bureaucratic administration.Brad Gilmour and Ted Huffman are Policy Analyst and Land Use Specialist respectively with Agriculture and Agri-food Canada. Andy Terauds and Charlie Jefferson are chairman and secretary respectively for the Ontario Institute of Agrologists Ottawa Branch Land Use Committee. This paper is intended to provoke thought and stimulate debate for input into the land use policy process and should not be seen as representing the views and policies of either Agriculture Canada or the Ontario Institute of Agrologists. 相似文献
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从自然的、经济的和技术的角度出发,以环境保护的观点,按照自然环境条件、生态条件、社会条件、社会经济状况和水质状况的共同性和差异性,进行区域划分,确定区域的水资源功能分区,为合理开发、利用和保护该区域水资源指明目标、方向和途径. 相似文献
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中条山东段植被垂直带的数量分类研究 总被引:20,自引:0,他引:20
在野外调查的基础上,应用有序样方聚类法对中条山东段植 垂直带进行了数量分类研究,结果为:1.落叶阔叶林带,包括4个亚带:(1)侧柏林带(500 ̄800m),(20松栎林带(800 ̄1800m),(3)栓皮林带(1400 ̄2000m)和(4)杨桦林带(1900 ̄2200m);2.山地草甸带(2100 ̄2358m)。此外,与前人的划分结果进行了比较,结果表明,有序样方聚类法的结果更符合实际情况。 相似文献
220.
Introduction: In recent years, Australia is seeing an increase in the total number of cyclists. However, the rise of serious injuries and fatalities to cyclists has been a major concern. Understanding the factors affecting the fatalities and injuries of bicyclists in crashes with motor vehicles is important to develop effective policy measures aimed at improving the safety of bicyclists. This study aims to identify the factors affecting motor vehicle-bicycle (MVB) crashes in Victoria, Australia and introducing effective countermeasures for the identified risk factors. Method: A data set of 14,759 MVB crash records from Victoria, Australia between 2006 and 2019 was analyzed using the binary logit model and latent class clustering. Results: It was observed that the factors that increase the risk of fatalities and serious injuries of bicyclists (FSI) in all clusters are: elderly bicyclist, not using a helmet, and darkness condition. Likewise, in areas with no traffic control, clear weather, and dry surface condition (cluster 1), high speed limits increase the risk of FSI, but the occurrence of MVB crashes in cross intersection and T-intersection has been significantly associated with a reduction in the risk of FSI. In areas with traffic control and unfavorable weather conditions (cluster 2), wet road surface increases the risk of FSI, but the areas with give way sign and pedestrian crossing signs reduce the risk of FSI. Practical Applications: Recommendations to reduce the risk of fatalities or serious injury to bicyclists are: improvement of road lighting and more exposure of bicyclists using reflective clothing and reflectors, separation of the bicycle and vehicle path in mid blocks especially in high-speed areas, using a more stable bicycle for the older people, monitoring helmet use, improving autonomous emergency braking, and using bicyclist detection technology for vehicles. 相似文献