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1.
Regional groundwater flow in deep aquifers adds advective components to the surface heat flow over extensive areas within the Great Plains province. The regional groundwater flow is driven by topographically controlled piezometric surfaces for confined aquifers that recharge either at high elevations on the western edge of the province or from subcrop contacts. The aquifers discharge at lower elevations to the east. The assymetrical geometry for the Denver and Kennedy Basins is such that the surface areas of aquifer recharge are small compared to the areas of discharge. Consequently, positive advective heat flow occurs over most of the province. The advective component of heat flow in the Denver Basin is on the order of 15 mW m−2 along a zone about 50 km wide that parallels the structure contours of the Dakota aquifer on the eastern margin of the Basin. The advective component of heat flow in the Kennedy Basin is on the order of 20 mW m−2 and occurs over an extensive area that coincides with the discharge areas of the Madison (Mississippian) and Dakota (Cretaceous) aquifers. Groundwater flow in Paleozoic and Mesozoic aquifers in the Williston Basin causes thermal anomalies that are seen in geothermal gradient data and in oil well temperature data. The pervasive nature of advective heat flow components in the Great Plains tends to mask the heat flow structure of the crust, and only heat flow data from holes drilled into the crystalline basement can be used for tectonic heat flow studies.  相似文献   

2.
Heat flow values were calculated from direct measurements of temperature and thermal conductivity at thirteen sites in the Arkansas-Missouri Ozark Plateau region. These thirteen values are augmented by 101 estimates of heat flow, based on thermal conductivity measurements and temperature gradients extrapolated from bottom-hole temperatures. The regional heat flow profile ranges from 9 mW m−2 to over 80 mW m−2, but at least two distinct thermal regimes have been identified. Seven new heat flow determinations are combined with three previously published values for the St. Francois Mountains (SFM), a Precambrian exposure of granitic and rhyolitic basement rocks, average 47 mW m−2. Radioactive heat production of 76 samples of the exposed rocks in the SFM averages 2.4 μW m−2 and a typical continental basement contribution of 14 mW m−2 is implied. Conversely, the sedimentary rock sequence of the plateau is characterized by an anomalously low heat flow, averaging approximately 27 mW m−2. Groundwater transmissivity values that are based on data from 153 wells in deep regional aquifers demonstrate an inverse relationship to the observed heat flow patterns. The areas of high transmissivity that correspond to areas of low total heat flux suggest that the non-conservative vertical heat flow within the Ozark sedimentary sequence can be attributed to the effects of groundwater flow.  相似文献   

3.
Geothermal studies have been conducted in China continuously since the end of the 1950's with renewed activity since 1970. Three areas of research are defined: (1) fundamental theoretical research on geothermics, including subsurface temperatures, terrestrial heat flow and geothermal modeling; (2) exploration for geothermal resources and exploitation of geothermal energy; and (3) geothermal studies in mines.Regional geothermal studies have been conducted recently in North China and more than 2000 values of subsurface temperature have been obtained. Temperatures at a depth of 300 m generally range from 20 to 25°C with geothermal gradients from 20 to 40°C/km. These values are regarded as an average for the region with anomalies related to geological factors.To date, 22 reliable heat flow data from 17 sites have been obtained in North China and the data have been categorized according to fault block tectonics. The average heat flow value at 16 sites in the north is 1.3 HFU, varying from 0.7 to 1.8 HFU. It is apparent that the North China fault block is characterized by a relatively high heat flow with wide variations in magnitude compared to the mean value for similar tectonic units in other parts of the world. It is suggested that although the North China fault block can be traced back to the Archaean, the tectonic activity has been strengthening since the Mesozoic resulting in so-called “reactivation of platform” with large-scale faulting and magmatism.Geothermal resources in China are extensive; more than 2000 hot springs have been found and there are other manifestations including geysers, hydrothermal explosions, hydrothermal steam, fumaroles, high-temperature fountains, boiling springs, pools of boiling mud, etc. In addition, there are many Meso-Cenozoic sedimentary basins with widespread aquifers containing geothermal water resources in abundance. The extensive exploration and exploitation of these geothermal resources began early in the 1970's. Since then several experimental power stations using thermal water have been set up in Fengshun (Fungshun),  相似文献   

4.
Large variations in terrestrial heat flow from 21 to 209 mW/m2 have been observed over the North Island, New Zealand. This is generally in good agreement with the pattern of existing geological and geophysical observations. A high heat flow zone with a value of 92 ±3 mW/m2, which corresponds to melting temperatures near the base of the crust, is delineated in the northern part of the Taranaki Basin. In the rest of the island, heat flow appears to be low to normal, but some isolated high values are also found. Observed results are interpreted in terms of crust and mantle structure in a region of plate subduction.  相似文献   

5.
Summary The coalification data of 12 boreholes in the Central Bohemian Basin are used to evaluate the paleotemperature gradients for the Upper Carboniferous period of the basin's development. Two versions of the burial history considered are supposed to yield an upper and a lower estimate. According to the more probable lower version, the average values of the paleogradient suggest an increasing tendency from west to east in the interval of 45–53K/km. The current geothermal gradients vary in the range of 28–35K/km. By combining the present thermal conductivity and the paleogradients, we have tried to estimate the Upper Carboniferous heat flow. Its values range from 96mW/m 2 to 117mW/m 2 .The results obtained can be compared with the paleogradient estimates in the Saar-Nahe Basin (F. R. of Germany). This region, which is similar with respect to the time of origin and tectonic pattern to the Central Bohemian Basin, displays on the average a slightly higher Permo-Carboniferous geothermal gradient of 60K/km.  相似文献   

6.
Five new heat flow values obtained in deep boreholes in the Western Carpathians are presented. Three holes were located in pre-Neogene folded units, the other two holes in Tertiary volcanites. The heat flow values range from 50.7 to 73.3 mW m?2 with an average value of 65.9 mW m?2 and they represent very needed information on the geothermal field in an area where heat flow values are still scarce.  相似文献   

7.
Preliminary heat flow values ranging from 42 to 175 mW m–2 have been estimated for Egypt from numerous geothermal gradient determinations with a reasonably good geographical distribution, and a limited number of thermal conductivity determinations. For northern Egypt and the Gulf of Suez, gradients were calculated from oil well bottom hole temperature data; east of the Nile, and at three sites west of the Nile, gradients were calculated from detailed temperature logs in shallow boreholes. With one exception, the heat flow west of the Nile and in northern Egypt is estimated to be low, 40–45 mW m–2, typical of a Precambrian Platform province. A local high, 175 mW m–2, is probably due to local oxidational heating or water movement associated with a phosphate mineralized zone. East of the Nile, however, including the Gulf of Suez, elevated heat flow is indicated at several sites, with a high of 175 mW m–2 measured in a Precambrian granitic gneiss approximately 2 km from the Red Sea coast. These data indicate potential for development of geothermal resources along the Red Sea and Gulf of Suez coasts. Water geochemistry data confirm the high heat flow, but do not indicate any deep hot aquifers. Microearthquake monitoring and gravity data indicate that the high heat flow is associated with the opening of the Red Sea.  相似文献   

8.
In southern British Columbia the terrestrial heat flow is low (44 mW m–2) to the west of the Coast Plutonic Complex (CPC), average in CPC (50–60 mW m–2),and high to the east(80–90 mW m–2). The average heat flow in CPC and the low heat generation (less than 1 W m–3) indicate that a relatively large amount of heat flows upwards into the crust which is generally quite cool. Until two million years ago the Explorer plate underthrust this part of the American plate, carrying crustal material into the mantle. Melted crustal rocks have produced the inland Pemberton and Garibaldi volcanic belts in the CPC.Meager Mountain, a volcanic complex in the CPC 150 km north of Vancouver, is a possible geothermal energy resource. It is the product of intermittent activity over a period of 4 My, the most recent eruption being the Bridge River Ash 2440 y B.P. The original explosive eruption produced extensive fracturing in the granitic basement, and a basal explosion breccia from the surface of a cold brittle crust. This breccia may be a geothermal reservoir. Other volcanic complexes in the CPC have a similar potential for geothermal energy.Earth Physics Contribution No. 704.  相似文献   

9.
Heat flow values of 33–58 mW m–2 were found for the Transylvanian Depression, 45–57 mW m–2 for the crystalline nucleus of the Eastern Carpathians, and 70–120 mW m–2 for the Neogene volcanic area. Temperature-depth profile and some geophysical implications of the low values for the Transylvanian Depression are discussed, rendering evident clear-cut differences between this tectonic unit and other Noegene depressions. The heat flow values for the other two investigated tectonic units are usual ones for areas of their age.A preliminary map of the heat flow distribution over the Romanian territory is presented and its relation to other geophysical fields is discussed. A positive correlation was found between gravity and heat flow, and a negative one between crustal thickness and heat flow. A general conclusion could be drawn that the heat flow distribution over the Romanian territory seems to be governed by processes taking place in the upper mantle, rather than by the radioactive decay within the crust.  相似文献   

10.
The results of seismic measurements along the deep seismic sounding profile VII and terrestrial heat flow measurements used for construction of heat generation models for the crust in the Paleozoic Platform region, the Sudetic Mountains (Variscan Internides) and the European Precambrian Platform show considerable differences in mantle heat flow and temperatures. At the base of the crust variations from 440–510°C in the models of Precambrian Platform to 700–820°C for the Paleozoic Platform and the Variscan Internides (Sudets) are found. These differences are associated with considerable mantle heat flow variations.The calculated models show mantle heat flow of about 8.4–12.6 mW m–2 for the Precambrian Platform and 31 mW m–2 to 40.2 mW m–2 for Paleozoic orogenic areas. The heat flow contribution originating from crustal radioactivity is almost the same for the different tectonic units (from 33.5 mW m–2 to 37.6 mW m–2). Considerable physical differences in the lower crust and upper mantle between the Precambrian Platform and the adjacent areas, produced by lateral temperature variations, could be expected. On the basis of carbon ratio data it can be concluded that the Carboniferous paleogeothermal gradient was much lower in the Precambrian Platform area than in the Paleozoic Platform region.  相似文献   

11.
A heat flow isoline map is presented. Low and relatively constant heat flow has been observed in the old shield areas of the East European Platform (25–40 mW/m2). Increased heat flow (>50 mW/m2) has been found in the Dniepr-Donetz depression. The area south of the East European Platform is characterized by highly variable heat flow (55–100 mW/m2). Some geophysical implications are discussed.  相似文献   

12.
南海北部大陆边缘盆地地热特征与油气富集   总被引：3，自引：3，他引：0       下载免费PDF全文
本文报道了莺歌海盆地、北部湾盆地共148个新测热导率数据,根据收集的钻井温度数据新增计算65个大地热流数据;结合前人研究成果绘制了南海北部大陆边缘沉积盆地的地温梯度图、大地热流分布图;系统归纳了南海北部大陆边缘油气勘探成果.结果表明,南海北部大陆边缘珠江口盆地、琼东南盆地、北部湾盆地、莺歌海盆地的平均热流值分别为68.7±11 mW/m2、71.1±13 mW/m2、65.7±8.9 mW/m2、74.7±10 mW/m2,属于典型的“热盆”.热流区域分布特征总体上受大地构造背景控制,随地壳厚度从北向南,由陆架到陆坡区逐渐减薄而增高,水热活动与岩浆活动等是引起局部高热流异常的原因.盆地地温场的差异控制和约束了油气分布富集规律,从研究区油气勘探成果中可以发现,该区域的气田多发育于高热流盆地（凹陷）,而中-低热流盆地（凹陷）则多孕育油田,油气田具有“北油南气”的分布特征.  相似文献   

13.
Continental shield regions are normally characterized by low-to-moderate mantle heat flow. Archaean Dharwar craton of the Indian continental shield also follows the similar global pattern. However, some recent studies have inferred significantly higher mantle heat flow for the Proterozoic northern block of Southern Granulite Terrain (SGT) in the immediate vicinity of the Dharwar craton by assuming that the radiogenic elements depleted exposed granulites constitute the 45-km-thick crust. In this study, we use four-layered model of the crustal structure revealed by integrated geophysical studies along a geo-transect in this region to estimate the mantle heat flow. The results indicate that: (i) the mantle heat flow of the northern block of SGT is 17 ± 2 mW/m2, supporting the global pattern, and (ii) the lateral variability of 10–12 mW/m2 in the surface heat flow within the block is of crustal origin. In terms of temperature, the Moho beneath the eastern Salem–Namakkal region appears to be at 80–100 °C higher temperature than that beneath the western Avinashi region.  相似文献   

14.
中国陆域居里等温面深度特征   总被引：14，自引：1，他引：13       下载免费PDF全文
基于最新编制的1/100万全国航陆域磁异常图数据,采用功率谱法对中国陆域的居里点深度进行了估算,获得了8004个居里点深度,完成了中国陆域居里面深度图的编制,首次完整的展现了中国陆域的居里面起伏特征.研究表明,居里面在稳定地块表现为坳陷,埋深为28~45km,如塔里木盆地,准噶尔盆地,柴达木盆地,可可西里—巴颜喀拉坳陷区,扬子盆地区,华北盆地区,松辽盆地,二连盆地,巴彦浩特—武威—潮水盆地,珠江口—琼东南盆地等.华北盆地区的居里面深度与塔里木陆块和扬子陆块有较大的差异,相对偏浅,这可能与华北陆块遭受了复杂的后期改造,导致软流圈上隆和岩石圈减薄有关.可可西里—巴颜喀拉地块是青藏高原北部发育的呈NWW向展布的巨型居里面坳陷带,其原因是该地区发育大面积的三叠系沉积地层和较少的岩浆活动,这些稳定的地块都具有莫霍面隆起和居里面坳陷的特征.在活动频繁的造山带居里面以隆起为特征,埋深为18~26km,如东北部山岭区、西北部山岭区、秦岭—大别山地区、西昆仑—西藏—三江—康滇地区、东南沿海地区等.这反映了构造运动及岩浆活动所引起的地壳地温梯度的差异.根据我国816个大地热流数据,对比研究居里面深度与地温梯度和大地热流的关系,结果显示居里面深度与热流值并非线性关系,居里面深度大于30km时,热流值较低,均小于100mW·m~(-2);在居里面深度小于30km的地区,热流值变化范围较大.并且,随着热流值的升高,热流值有向中国东部沿海、藏南—三江地区、秦岭—大别地区、辽东等集中的趋势,这些地区都呈现出居里面隆起的特征,是地热资源勘探开发的重要远景区.  相似文献   

15.
The chemical compositions of a total of 120 thermal water samples from four different tectonically distinct regions (Central, North, East and West Anatolia) of Turkey are presented and assessed in terms of geothermal energy potential of each region through the use of chemical geothermometers. Na–Ca–HCO3 type waters are the dominant water types in all the regions except that Na–Cl type waters are typical for the coastal areas of West Anatolia and for a few inland areas of West and Central Anatolia where deep water circulation exists. The discharge temperature of the springs ranges up to 100°C, and the bottom-hole temperatures in drilled wells up to 232°C. Geothermometry applications yield reservoir temperatures of about 125°C for Central Anatolia, 110°C for North Anatolia, 136°C for East Anatolia and 251°C for West Anatolia, the latter agreeing with some of the bottom hole temperatures measured in drilled wells. The results reveal that the highest geothermal energy potential in Turkey is associated with the West Anatolian extensional tectonics which provides a regional, deep-seated heat source and a widespread graben system allowing deep circulation of waters. The North Anatolian region, bounded to the south by the dextral North Anatolian Fault along which most of the geothermal sites are located, has the lowest energy potential, probably due to the restriction of the heat source to local magmatic activities confined to pull-apart basins. The East Anatolian region (undergoing contemporary compression) and the Central Anatolian region (where the compressional regime in the east is converted to the extensional regime in the west) have moderate energy potential. Although the recently active volcanoes suggest the presence, at depth, of still cooling magma chambers that are potential heat sources, the lack of well-developed fault systems is probably responsible for the comparatively low energy potential of these regions. Almost all the thermal waters of Turkey are saturated with respect to calcite and, hence, have a significant calcite scaling potential which is particularly high for West Anatolian waters.  相似文献   

16.
沁水盆地大地热流与地温场特征   总被引：11，自引：3，他引：8       下载免费PDF全文
分析了20口井的温度数据和39个岩石样品的热导率数据,计算了20个大地热流值.结果表明：沁水盆地具有偏高的大地热流背景,现今热流变化于448～1018 mW/m2之间,平均627±152 mW/m2,现今地温梯度介于209～476 ℃/km之间,平均地温梯度282±103 ℃/km. 热流的分布与本区上、下主煤层含气量的分布特征相似,在一定程度上反映了现代热流继承了煤层气生气期的古地热背景.  相似文献   

17.
The surface heat flow in the interior of Archean cratons is typically about 40 mW m−2 while that in Proterozoic and younger terrains surrounding them is generally considerably higher. The eighty-four heat flow observations from southern Africa provide an excellent example of this contrast in surface heat flow, showing a difference of some 25 mW m−2 between the Archean craton and younger peripheral units. We investigate two possible contributions to this contrast: (1) a shallow mechanism, essentially geochemical, comprising a difference in crustal heat production between the two terrains, and (2) a deeper mechanism, essentially geodynamical, arising from the existence of a lithospheric root beneath the Archean craton which diverts heat away from the craton into the thinner surrounding lithosphere. A finite element numerical model which explores the interplay between these two mechanisms suggests that a range of combinations of differences in crustal heat production and lithospheric thickness can lead to the contrast in surface heat flow observed in southern Africa. Additional constraints derived from seismological observations of cratonic roots, the correlation of surface heat flow and surface heat production, petrological estimates of the mean heat production in continental crust and constraints on upper mantle temperatures help narrow the range of acceptable models. Successful models suggest that a cratonic root beneath southern Africa extends to depths of 200–400 km. A root in this thickness range can divert enough heat to account for 50–100% of the observed contrast in surface heat flow, the remainder being due to a difference in crustal heat production between the craton and the surrounding mobile belts in the range of zero to 0.35 μW m−3.  相似文献   

18.
More than fifty heat flow measurements in Italy are examined. The values, corrected only for local influences (when present), are related to the main geological features with the following results: foreland areas, 55±19 mW m–2, foredeep areas, 45±21 mW m–2; folded regions and intermountain depressions, 76±29 mW m–2. In volcanic areas the heat flow rises to in excess of 600 mW m–2. From a tectonic point of view, these values are consistent with the hypothesis that the Apennine chain is intersected by two arcuate structures: the first from Liguria to Latium is very probably a continental arc, that is an are which occurs within a continent, and the second from Campania to Calabria is very similar from geophysical evidence to the classic island arcs.  相似文献   

19.
The aeromagnetic values over the study region are relatively uniform except for a few anomalies in the northeastern and southwestern areas. Analyses of aeromagnetic data were performed in NW Turkey, in order to have a look into the subsurface regional thermal structure of the region. For this purpose, power spectra, reduced to pole (RTP), and band-pass filtered anomalies were produced using geophysical techniques. Band-pass filtered data were produced from the RTP aeromagnetic anomalies to isolate near surface and undesired deep effects. Based on the aeromagnetic data interpretation, the thickness of the magnetized crust, named the Curie Point Depth (CPD), in the study area lies between 9.7 and 20.3 km. The CPD estimates in the Thrace region of Turkey indicate two shallow CPD (SCPD1 and SCPD2) zones (the Istranca Massif and the Saros Graben area). The deep CPD are located within the Thrace Basin with sediment thickness of about 9 km. The corresponding heat flow map prepared from the averaged thermal conductivities and thermal gradients from the CPD reveals the existence of one low heat flow zone (75 mW/m2) over the center of Thrace Basin, and two high heat flow zones over the Istranca Masif (100–125 mW/m2) in the northern side and Saros Graben (125–135 mW/m2) areas in the southern side of the Thrace Basin.  相似文献   

20.
Summary A geothermal anomaly reported to exist in southern Portugal and with heat flow density values as high as 160 mW/m2 was studied by the magneto-telluric method. The results of the magneto-telluric survey indicate that the study area is divided into several high electrical resistivity, deep-rooted blocks separated by low electrical resistivity zones. These latter zones coincide with the main trends of the faults that cross the region. The high heat flow density values reported for the area are incompatible with the high electrical resistivities observed in the magneto-telluric survey. Furthermore, heat production values calculated for some of the rocks that crop out in the area of the geothermal anomaly cannot explain the high heat flow density valuss. Since no hydrothermal activity is known for the region and recent volcanism is absent, it is suggested that previous heat flow density calculations for the area covered by the magnetotelluric survey are overestimated.Presented at International Meeting on Terrestrial Heat Flow and the Structure of Lithosphere, Bechyn Castle, Czech Republic, September 2 – 7, 1991.  相似文献   

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