Terrestrial Heat Flow and Heat Generation in South-west England

Three heat flow values for south-west England are presented. Two of the sites, Geevor and South Crofty, are operating tin mines on the northern contacts of the Land's End and Carnmenellis Granites, respectively, while the third, Wilsey Down, is a stratigraphical borehole 5 km north of the Bodmin Moor Granite. After applying topographic corrections values of 128·6 mW m^-2 (3·07 μ cal cm^-2 s^-1) for Geevor, 128·9 mW m^-2 (3·08 (A cal cm^-2 s^-1) for South Crofty and 67·3 mW cm^-2 (1·61 cal cm^-2 s^-1) for Wilsey Down, were determined. The value at Wilsey Down is shown to be consistent with that for an environment in which the Hercynian orogeny was the last significant thermal event. An additional heat source term must clearly be involved at Geevor and South Crofty to account for the unusually high values at these sites. Radiogenic heat production has been determined on granites from these sites and in spite of the fact that it is high it does not fully account for the measured heat flow. A compilation of underground temperature measurements made in the nineteenth century suggests that high heat flow is a general feature of the mineralized belt. At least part of this can be explained in terms of hot spring activity recorded widely throughout the area but the ultimate cause remains to be evaluated.     

珠海市土地利用空间格局与地形的相关性研究

以2008年Landsat TM遥感影像、地形图为基础数据,通过建立DEM、高程分级、坡度分级及叠加分析等方法,分析了珠海市土地利用空间格局及其与地形因子的关系.珠海市土地利用类型空间分布具有强烈的区域差异性,不同高程与坡度分级区域土地利用类型组合不同;各土地类型的面积在低海拔、低坡度段占绝对优势,随着高程和坡度的上升,土地利用类型减少,多样性降低.在高程<40 m、坡度<2°的区域,水域为主导土地利用方式,而在高程＞40 m、坡度＞2°的区域,林地成为主导土地利用类型的优势越来越明显;在海拔40～100 m、坡度2°～15°区域土地利用破碎度指数最高,受人类活动强烈干扰的地段主要集中在海拔低、坡度平缓的区域,自然因子在高坡度区域对土地利用空间格局起到一定的制约作用.     

Heat Flow and Geothermal Potential in the South-Central United States

Geothermal exploration is typically limited to high-grade hydrothermal reservoirs that are usually found in the western United States, yet large areas with subsurface temperatures above 150°C at economic drilling depths can be found east of the Rocky Mountains. The object of this paper is to present new heat flow data and to evaluate the geothermal potential of Texas and adjacent areas. The new data show that, west of the Ouachita Thrust Belt, the heat flow values are lower than east of the fault zone. Basement heat flow values for the Palo Duro and Fort Worth Basins are below 50 mW/m² while, in the frontal zone of the belt, they can exceed 60 mW/m². Further east, along the Balcones fault system the heat flow is in general higher than 55 mW/m². The eastern most heat flow sites are in Louisiana and they show very high heat flow (over 80 mW/m²), which is associated with the apparently highly radioactive basement of the Sabine uplift. The geothermal resource in this area is large and diverse, and can be divided in high grade (temperature above 150°C) convective systems, conductive based enhanced geothermal systems and geothermal/geopressured systems. One of the most attractive areas east of the cordillera extends from eastern Texas across Louisiana and Arkansas to western Mississippi. Here temperatures reach exploitation range at depths below 4 km, and tapping such a resource from shut in hydrocarbon fields is relatively easy. The initial costs of the development can be greatly reduced if existing hydrocarbon infrastructure is used, and therefore using shut-in hydrocarbon fields for geothermal purposes should not be neglected.     

A New Model for Heat Flow in Extensional Basins: Radiogenic Heat,Asthenospheric Heat,and the McKenzie Model

The McKenzie model proposed in 1978, which is widely used in calculating the thermal history of rift basins and other extensional basins, incorrectly assumes that all heat passing through the lithosphere originates below the lithosphere. In reality, heat from radiogenic sources within the lithosphere, especially in the upper crust, may represent more than half the heat flow at the top of basement. Thinning of the lithosphere during extension does indeed result in an increase of heat flowing from the asthenosphere, but this thinning also reduces the radiogenic heat from within the lithosphere. Because these two effects cancel to a large degree, the direct effects of lithospheric extension on heat flow at the top of basement are smaller than those predicted by the McKenzie model. Because of permanent loss of radiogenic material by lithospheric thinning, the heat flow at the top of basement long after rifting will be lower than the pre-rift heat flow.The McKenzie model predicts an instantaneous increase in heat flow during rifting. The Morgan model proposed in 1983, however, predicts a substantial time delay in the arrival of the higher heat flow from the asthenosphere at the top of basement or within sediments. Using the Morgan model, heat flow during the early stages of rifting will actually be lower than prior to rifting, because the time delay in the loss of radiogenic heat is less than the time delay in arrival of new heat from the asthenosphere.     

西安旅游区旅游流空间结构研究

把握旅游流运动规律有利于区域旅游产品开发方向的确定和线路合理组织。该文运用行为地理学相关概念和理论,采用实证分析和数理统计相结合的方法,对西安旅游区入境旅游流流动规律和空间结构进行了刻画和测度。结果显示,研究区内旅游流空间结构较不均衡,基尼系数高达0．38,游客对东线旅游产品往往表现出明显的整体偏好。对这种状况形成的机理和应对策略进行阐释与描述。     

良好植被区泥石流防治初探

通过对近年来发生在良好植被区的几次重大泥石流、滑坡灾害的考察,发现植被在泥石流、滑坡形成中的作用有待于进一步认识。通过分析,当中小强度降雨激发下,植被能够削减泥石流、滑坡灾害的规模,甚至抑制泥石流、滑坡灾害的发生;当降雨超过一定阀值后,在水作用下,植被不但不能削减灾害规模,反而增大灾害的规模。在这类地区,简单地使用一般的防治措施,已经不能满足防灾、减灾的需要,客观要求针对这些地区泥石流灾害的形成原因、危害特征,研究防治对策。经初步研究提出3点防治措施:1)加强泥石流滑坡灾害的预测预报工作;2)在重点区域设置自动雨量记录报警装置;3)特别针对漂木拦挡,采取新型结构减轻泥石流的危害。     

Connected Degree Evaluation on Watershed Topography Factors of Man-made Debris Flow Gully in Semiarid Area

在神府—东胜矿区人为泥石流沟道广泛野外调查的基础上,选取了43条典型泥石流样沟,在1∶10 000地形图及卫片上进行了形态要素量测,应用流域地貌分析原理,对43条样沟各形态要素进行了剖析及关联度评价,并进行了泥石流沟道发育阶段的信息维分析,所得结论为半干旱地区的人为泥石流沟道地势比沿程变化奇特,以形成区比降最大,区别于自然泥石流沟道;沟道分区面积比以汇水区面积最大,明显区别于湿润地区;流域形状以扇形为主,沟道给养面积较大,崎岖系数不甚太大是半干旱地区人为泥石流沟道的独特之处,泥石流沟道发育以幼、青年期为主,最后得出了以沟道比降为主因子的各形态要素的主次排序。     

紫色土丘陵区生态恢复模式与土壤性质相关性分析

探讨不同治理措施（林地采用等高草带、乔灌草、封禁等措施,园地采用隔坡梯田、水平梯田、梯田＋竹节沟等措施）对植被恢复和土壤性质的影响,并对植物多样性和土壤性质进行了相关分析,结果表明：不同治理措施对植物多样性（丰富度指数、多样性指数、均匀度指数）和土壤性质都有较大影响。林地以林草＋封禁措施效果最佳,其次是乔灌草措施;园地以隔坡梯田的综合效益最好,再次是水平梯田。在紫色土丘陵地区侵蚀地植被和土壤恢复时,以工程措施和林草措施并用为宜,如隔坡梯田＋乔灌草模式。