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1.
Seismic reflection data document for the first time the existence of a BSR in a limited area west of the Dnieper Canyon in the northwestern Black Sea. Seismic wide-angle data suggest that gas hydrates occupy in average 15±2% of the pore space in a zone of 100 m in thickness. A conservative quantification of the amount of methane associated with this gas hydrate occurrence is about 12±3×1011 m3 (0.6±0.2 Gt of methane carbon). Conductive heat flow deduced from the BSR depth is in the range of 21±6 to 55±15 mW m–2.  相似文献   

2.
Heat flow anomalies provide critical information in active tectonic environments. The Gulf of Cadiz and adjacent areas are affected by the plate convergence between Africa and Europe, causing widespread deformation and faulting. Active thrust faults cause lateral movement and advection of heat that produces systematic variations in surface heat flow. In December 2003 new heat flow data were collected during the research vessel Sonne cruise SO175 in the Gulf of Cadiz over two sites of recent focused research activity: (i) the Gulf of Cadiz sedimentary prism and (ii) the Marques de Pombal escarpment. Both features have also been discussed as potential source areas of the Great Lisbon earthquake and tsunami of 1755. Background heat flow at the eastern terminus of the Horseshoe abyssal plain is about 52–59 mW/m2. Over the Gulf of Cadiz prism, heat flow decreases from ∼57 mW/m2 to unusually low values of 45 mW/m2 roughly 120 km eastward. Such low values and the heat flow trend are typical for active thrusting, supporting the idea of an east-dipping thrust fault. Slip rates are 10 ± 5 mm per year, assuming that the fault dips at 2°. A fault dipping at 5°, however, would result into slip rates of 1.5–5 mm per year, suggesting that subduction has largely ceased. Based on seismic data, the Marques de Pombal fault is interpreted as part of an active fault system located ∼100 km westward of Cape San Vincente. Heat flow over the fault is affected by refraction of heat caused by the 1 km high escarpment. Thermal models suggest that the slip rate along the fault must either be small or shear stresses acting on the fault are rather high. With respect to other fault zones, however, it is reasonable to assume that the fault's slip rate is small.  相似文献   

3.
琼东南盆地深水区构造热演化特征及其影响因素分析   总被引：5，自引：1，他引：4  
To reveal the tectonic thermal evolution and influence factors on the present heat flow distribution, based on 154 heat flow data, the present heat flow distribution features of the main tectonic units are first analyzed in detail, then the tectonic thermal evolution histories of 20 profiles are reestablished crossing the main deep-water sags with a structural, thermal and sedimentary coupled numerical model. On the basis of the present geothermal features, the Qiongdongnan Basin could be divided into three regions: the northern shelf and upper slope region with a heat flow of 50–70 m W/m2, most of the central depression zone of 70–85 m W/m2, and a NE trending high heat flow zone of 85–105 m W/m2 lying in the eastern basin. Numerical modeling shows that during the syn-rift phase, the heat flow increases generally with time, and is higher in basement high area than in its adjacent sags. At the end of the syn-rift phase, the heat flow in the deepwater sags was in a range of 60–85 m W/m2, while in the basement high area, it was in a range of 75–100 m W/m2. During the post-rift phase, the heat flow decreased gradually, and tended to be more uniform in the basement highs and sags. However, an extensive magmatism, which equivalently happened at around 5 Ma, has greatly increased the heat flow values, and the relict heat still contributes about 10–25 m W/m2 to the present surface heat flow in the central depression zone and the southern uplift zone. Further analyses suggested that the present high heat flow in the deep-water Qiongdongnan Basin is a combined result of the thermal anomaly in the upper mantle, highly thinning of the lithosphere, and the recent extensive magmatism. Other secondary factors might have affected the heat flow distribution features in some local regions. These factors include basement and seafloor topography, sediment heat generation, thermal blanketing, local magmatic injecting and hydrothermal activities related to faulting and overpressure.  相似文献   

4.
The Pearl River Mouth Basin (PRMB) and Qiongdongnan Basin (QDNB) are oil and gas bearing basins in the northern margin of the South China Sea (SCS). Geothermal survey is an important tool in petroleum exploration. A large data set comprised of 199 thermal conductivities, 40 radioactive heat productions, 543 measured geothermal gradient values, and 224 heat flow values has been obtained from the two basins. However, the measured geothermal gradient data originated from diverse depth range make spatial comparison a challenging task. Taking into account the variation of conductivity and heat production of rocks, we use a “uniform geothermal gradient” to characterize the geothermal gradient distribution of the PRMB and QDNB. Results show that, in the depth interval of 0–5 km, the “uniform geothermal gradient” in the PRMB varies from 17.8 °C/km to 50.2 °C/km, with an average of 32.1 ± 6.0 °C/km. In comparison, the QDNB has an average “uniform geothermal gradient” of 31.9 ± 5.6 °C/km and a range between 19.7 °C/km and 39.5 °C/km. Heat flows in the PRMB and QDNB are 71.3 ± 13.5 mW/m2 and 72.9 ± 14.2 mW/m2, respectively. The heat flow and geothermal gradient of the PRMB and QDNB tend to increase from the continental shelf to continental slope owing to the lithosphereic/crustal thinning in the Cenozoic.  相似文献   

5.
Measurements of dispersed vitrinite along several exploration wells within the northern Rhinegraben are indicative of a thermal graben history that is influenced by a combination of basal conductive and groundwater-flow related convective heat transfer. To determine the conductive/convective components of heat transfer within the rift today, a series of 2D numerical groundwater flow and heat models are developed along a cross-sectional transect across the northern Rhinegraben. Fault zone permeability is varied in the simulations of these models to determine the possible fluid pathways and the effects of circulating groundwater on the graben temperature field. Depending on the fault permeability, negative thermal anomalies always develop in areas of cold recharging groundwater along the graben flanks regardless of fault permeability, whereas hot discharging groundwater near the topographic low of the graben only results in positive thermal anomalies under the assumption of high fault permeability. Simulation results suggest that the modern groundwater flow system has an overall net cooling effect on the temperature field of the rift.Without convective cooling by groundwater, vitrinite reflectance levels in wells would be expected to be much higher on average than are observed. Although relatively high heat flow densities (100 mW/m2) are documented in the Rhinegraben, an average of only 65 mW/m2 would be sufficient to produce the observed vitrinite reflectance levels. Thus, a long-lived (>10 My) cooling convective fluid flow in combination with a high basal heat flow seems to be active.  相似文献   

6.
In July 2007, new marine heat flow data were collected at ten sites (HF01–10) in the central and southwestern sectors of the Ulleung Basin (East Sea or Sea of Japan) as part of regional gas hydrate research. In addition, cores were collected at five of these sites for laboratory analysis. The results show that the geothermal gradient ranged from 103–137 mK/m, and the in-situ thermal conductivity from 0.82–0.95 W/m·K. Laboratory measurements of thermal conductivity were found to deviate by as much as 40% from the in-situ measurements, despite the precautions taken to preserve the cores. Based on the in-situ conductivity, the heat flow was found to increase with water depth toward the center of the basin, ranging from 84–130 mW/m2. Using a simple model, we estimated the heat flow from the depths of the BSR, and compared this with the observed heat flow. In our study area, the two sets of values were quite consistent, the observed heat flows being slightly higher than the BSR-derived ones. The evaluation of regional pre-1994 data revealed that the heat flow varied widely from 51–157 mW/m2 in and around the basin. Due to a large scatter in these older data, a clear relationship between heat flow and water depth was not evident, in contrast to what would be expected for a rifted sedimentary basin. This raises the question as to whether the pre-1994 data represent the true background heat flow from the underlying basin crust since the basin opening, and/or whether they contain large measurement errors. In fact, evidence in support of the latter explanation exists. BSRs are generally found in the deep parts of the basin, and vary by only ±15 m in depth below the seafloor. From the average BSR depth, we inferred the background heat flow using a simple model, which in the case of the Ulleung Basin is approximately 120 and 80 mW/m2 for 2.5 and 1 km below sea level, respectively.  相似文献   

7.
In January–February 1987, an urgent cruise JENEX-87 was carried out in the central equatorial Pacific during the occurrence of the 1986–87 El Niño. This cruise, supported by the Japan Science and Technology Agency, supplied heat flux data through the sea surface, on the basis of direct measurements of short- and long-wave radiation fluxes.In the time average, the heat gain due to the radiation flux (153 W m–2) was almost compensated by the heat loss due to latent heat flux (130 W m–2), and thus the net heat gain was small in magnitude (20 W m–2). On the other hand, day-to-day changes of the net heat flux ranged within ±130 W m–2, mainly reflecting the downward short-wave radiation variations.The heat balance in the surface oceanic mixed layer was investigated in two quadrangle areas (160°E-180° and 180°-160°W between 2°N and 2°S), using the surface heat flux and estimating the advective heat fluxes due to the geostrophic and Ekman currents. In these two quadrangles, we respectively derived –187±88 W m–2 and +27±95 W m–2. The former value, which is equivalent to about 1°C month–1 drop of the mixed layer temperature, is evidence of the abnormal oceanic condition in the occurrence of the 1986–87 El Niño event.  相似文献   

8.
A detailed heat flow study of some areas in the Middle America Trench is attempted. Forty six measurements were obtained in the region between the Tres Marias Islands and the Tehuantepec Ridge. The stations were concentrated in three detailed survey areas and 4 profiles. The obtained data show a steep decrease in the heat flow values towards the southern portion of the trench. The detailed survey area, located in the northern end of the trench (Area 20–1) has the highest heat flow average (122 mW m-2), however a characteristical pattern was observed: most data within the Rivera Plate have higher than average heat flow due to the young age of this plate and contrast with the low values associated with the continental lithosphere of the North America Plate. Areas 20–3 and 20–4 have lower averages (50 and 27 mW m-2 respectively) and they coincide with portions of the Guadalupe Plate, proposed by Klitgord and Mammerickx (1982) and assumed to be older than the Cocos Plate, though magnetic lineations have not been directly correlated with age in those areas.  相似文献   

9.
The Qiangtang Basin is a significant prospective area for hydrocarbon and gas hydrate resources in the Tibetan Plateau, China. However, relatively little work has been performed to characterise heat flow in this basin, which has restricted petroleum and gas hydrate exploration. In this study, we compare present and palaeo-heat flow in the Qiangtang Basin to provide information on geothermal regime, hydrocarbon generation and permafrost that is necessary for further petroleum and gas hydrate exploration. We base our study on temperature data from a thermometer well, thermal conductivity tests, vitrinite reflectance data, homogenisation temperature data from fluid inclusions, stratigraphic information and a time-independent modelling approach. Our results indicate that in the central Qiangtang Basin, the present thermal gradient is approximately 15.5 °C/km, and heat flow is approximately 46.69 mW/m2. Heat flow in the Qiangtang Basin is not relatively stable since the Early Jurassic, as previous research has suggested, and it is generally decreasing with time. Additionally, there is a clear difference between the hottest thermal regime of the southern and northern Qiangtang Depressions during Cretaceous to Pleistocene time. In the southern Qiangtang Depression, the palaeogeothermal gradient is approximately 32.0 °C/km, and palaeo-heat flow is approximately 70 mW/m2. However, in the northern Qiangtang Depression, the palaeogeothermal gradient exceeds 81.8 °C/km, and palaeo-heat flow is greater than 172.09 mW/m2. The high thermal regime in the northern Qiangtang Depression is driven mainly by hydrothermal convection. Gas reservoirs are possible targets for hydrocarbon exploration in this depression. Currently, the northwestern part of the northern Qiangtang Depression is the most favourable area for gas hydrate exploration in the Qiangtang Basin.  相似文献   

10.
Bottom simulating reflectors (BSRs), known as the base of gas hydrate stability zone, have been recognized and mapped using good quality three-dimensional (3D) pre-stack migration seismic data in Shenhu Area of northern South China Sea. Additionally, seismic attribute technique has been applied to better constrain on the distribution of gas hydrate. The results demonstrate that gas hydrate is characterized by “blank” zone (low amplitude) in instantaneous amplitude attribute. The thickness of gas hydrate stability zone inferred from BSR ranges from 125 to 355 m with an average of 240 m at sea water depth from 950 to 1,600 m in this new gas hydrate province. The volume of gas in-place bound in hydrate is estimated from 1.7 × 109 to 4.8 × 109 m3, with the most likely value of around 3.3 × 109 m3, using Monte Carlo simulation. Furthermore, geothermal gradient and heat flow are derived from the depths of BSRs using a conductive heat transfer model. The geothermal gradient varies from 35 to 95°C km−1 with an average of 54°C km−1. Corresponding heat flow values range from 43 to 105 mW m−2 with an average of 64 mW m−2. By comparison with geological characteristics, we suggest that the distribution of gas hydrate and heat flow are largely associated with gas chimneys and faults, which are extensively distributed in Shenhu Area, providing easy pathways for fluids migrating into the gas hydrate stability zone for the formation of gas hydrate. This study can place useful constraints for modeling gas hydrate stability zone from measured heat flow data and understanding the mechanism of gas hydrate formation in Shenhu Area.  相似文献   

11.
Heat flow was measured on the Lomonosov Ridge during the 5th Chinese National Arctic Expedition in 2012. To derive the time-temperature curve, resistivity data were transformed to temperature by the resistivity- temperature program. Direct reading and linear regression methods were used to calculate the equilibrium temperature, which were regressed against the depth of the probes in sediment to derive the geothermal gradient. Then, heat flow was calculated as the product of geothermal gradient and thermal conductivity of sediments. The heat flow values on the basis of the two methods were similar （i.e., 67.27 mW/m2 and 63.99 mW/m2, respectively）. The results are consistent with the measurements carried out at adjacent sites. The age of the Lomonosov Ridge predicted by the heat flow-age model was 62 Ma, which is in accordance with the inference that the ridge was separated from Eurasia at about 60 Ma.  相似文献   

12.
2016年8月7－14日中国第七次北极科学考察期间,在83°N附近设立的长期浮冰站开展了辐射和湍流通量观测研究。结果表明,观测期间反照率变化范围为0.64~0.92,平均反照率为0.78;基于现场观测数据评估了PW79、HIRHAM、ARCSYM和CCSM3 4种不同复杂度的反照率参数化方案在天气尺度的表现,最为复杂的CCSM3结果优于其他参数化方案,但不能体现降雪条件下的反照率快速增长。浮冰区冰雪面平均净辐射为18.10 W/m2,平均感热通量为1.73 W/m2,平均潜热通量为5.55 W/m2,海冰表面消融率为（0.30±0.22） cm/d,表明此时北冰洋浮冰正处于快速消融期。冰面的平均动量通量为0.098（kg·m/s）/（m2·s）,动量通量与风速有很好的对应关系,相关系数达0.80。  相似文献   

13.
Between 33°S and 47°S, the southern Chile forearc is affected by the subduction of the aseismic Juan Fernandez Ridge, several major oceanic fracture zones on the subducting Nazca Plate, the active Chile Ridge spreading centre, and the underthrusting Antarctic Plate. The heat flow through the forearc was estimated using the depth of the bottom simulating reflector obtained from a comprehensive database of reflection seismic profiles. On the upper and middle continental slope along the whole forearc, heat flow is about 30–60 mW m–2, a range of values common for the continental basement and overlying slope sediments. The actively deforming accretionary wedge on the lower slope, however, in places shows heat flow reaching about 90 mW m–2. This indicates that advecting pore fluids from deeper in the subduction zone may transport a substantial part of the heat there. The large size of the anomalies suggests that fluid advection and outflow at the seafloor is overall diffuse, rather than being restricted to individual fault structures or mud volcanoes and mud mounds. One large area with very high heat flow is associated with a major tectonic feature. Thus, above the subducting Chile Ridge at 46°S, values of up to 280 mW m–2 indicate that the overriding South American Plate is effectively heated by subjacent zero-age oceanic plate material.  相似文献   

14.
Several heat flow measurements were made during the NAT83 cruise in the central part of the Solomon Sea Basin. The average value of 87 mW/m2 (2.08 HFU) calculated from these and other data indicates that the age of the Solomon Sea Basin may range from 24 to 44 Ma. This is supported by the water depth, of approximately 4,500 m, versus age relationship. There is a possibility that the Solomon Sea Basin is not a back-arc basin associated with an arc but was formerly a relatively large oceanic plate. The agreement in age from both heat flow and water depth data favors the latter hypothesis.  相似文献   

15.
Several heat flow measurements were made during the NAT83 cruise in the central part of the Solomon Sea Basin. The average value of 87 mW/m2 (2.08 HFU) calculated from these and other data indicates that the age of the Solomon Sea Basin may range from 24 to 44 Ma. This is supported by the water depth, of approximately 4,500 m, versus age relationship. There is a possibility that the Solomon Sea Basin is not a back-arc basin associated with an arc but was formerly a relatively large oceanic plate. The agreement in age from both heat flow and water depth data favors the latter hypothesis.  相似文献   

16.
This study addresses the morphology of pockmarks along the western continental margin of India using multibeam bathymetry and backscatter data. Here, for the first time we have utilized the application of ArcGIS (Geographical Information System) for understanding the morphology of pockmarks from the western continental margin of India. The pockmarks observed in water depths of 145–330 m are circular, elliptical or elongated in plan-view, with an average length and width of 157 (±72) m and 83 (±19) m respectively. The average pockmark relief and perimeter are 1.9 (±0.9) m and 412 (±181) m, respectively. The pockmarks have average areas and volumes of 10 759 m2 and 15 315 m3 respectively. Spatial separation that coincides with 210 m isobath divides the pockmarks into two groups with differing distributions and morphologies. These pockmarks originated from seepages of biogenic or thermogenic gas or from pore fluids from deeper sources, migrated vertically along the faults. Besides a possible structural control, the pockmark morphologies are also affected by bottom currents and/or by submarine slumping. The average acoustic backscatter strength from pockmark centre is higher (−35 dB) than the average backscatter of the total area (−40 dB), which suggests their possible linkage to the precipitation of diagenitic minerals from biodegradation of seepage material.  相似文献   

17.
低勘探程度盆地模拟研究——以南黄海盆地北部坳陷为例   总被引：5，自引：0，他引：5  
盆地模拟已成为当前沉积盆地研究的重要工具。南黄海盆地北部坳陷自裂陷期演化以来沉积了巨厚的中-新生代碎屑沉积,近年来的地质调查获取的数据为其盆地模拟研究提供了条件,本次研究在收集相关基础数据的基础上,首先对盆地构造热演化史进行了模拟,重建了盆地热史,模拟结果显示其古热流在中-晚侏罗世平均值约为61mW/m2,在约145-74Ma间不断上升至约80 mW/m2,随后缓慢下降至65 mW/m2,并持续到渐新世末期,据此将盆地演化阶段划分为裂前期、裂陷期及裂后期。盆地模拟结果显示北部坳陷在白垩纪逐步进入强裂陷演化阶段并经历快速沉积过程,至晚白垩纪裂陷发育程度中等,在此基础上,对研究区进行了三维盆地模拟,结果显示北部坳陷生烃门限深度大致位于古近系阜宁组顶部,下伏的侏罗系及白垩系烃源岩基本完成生排烃过程,其中侏罗系烃源岩生排烃主要发生在盆地发育的裂陷期及裂后期,而白垩系及古近系烃源岩生排烃主要发生在裂后期。尽管研究区尚处在低勘探程度阶段,但盆地模拟结果已能为研究区下一步的勘探提供重要的信息,此外,本次研究对模拟过程中的主要不确定性也进行了分析。  相似文献   

18.
The Late Miocene Zeit Formation is exposed in the Red Sea Basin of Sudan and represents an important oil-source rock. In this study, five (5) exploratory wells along Red Sea Basin of Sudan are used to model the petroleum generation and expulsion history of the Zeit Formation. Burial/thermal models illustrate that the Red Sea is an extensional rift basin and initially developed during the Late Eocene to Oligocene. Heat flow models show that the present-day heat flow values in the area are between 60 and 109 mW/m2. The variation in values of the heat flow can be linked to the raise in the geothermal gradient from margins of the basin towards offshore basin. The offshore basin is an axial area with thick burial depth, which is the principal heat flow source.The paleo-heat flow values of the basin are approximately from 95 to 260 mW/m2, increased from Oligocene to Early Pliocene and then decreased exponentially prior to Late Pliocene. This high paleo-heat flow had a considerable effect on the source rock maturation and cooking of the organic matter. The maturity history models indicate that the Zeit Formation source rock passed the late oil-window and converted the oil generated to gas during the Late Miocene.The basin models also indicate that the petroleum was expelled from the Zeit source rock during the Late Miocene (>7 Ma) and it continues to present-day, with transformation ratio of more than 50%. Therefore, the Zeit Formation acts as an effective source rock where significant amounts of petroleum are expected to be generated in the Red Sea Basin.  相似文献   

19.
The long-term mean (31-year mean) surface heat fluxes over the Japan Sea are estimated by the bulk method using the most of the available vessel data with the resolution of 1o×1o. The long-term annual mean net heat flux is about –53 W m–2 (negative sign means upward heat flux) with the annual range from 133 W m–2 in May to –296 W m–2 in December. The small gain of heat in the area near Vladivostok seems to indicate the existence of cold water flowing from the north. In that area in winter, the mean loss of heat attains about 200 W m–2, and the Bowen's ratio is over the unity. The largest insolation occurs in May in the Japan Sea, and the upward latent heat flux becomes the largest in November in this area. The heat flux of Haney type is also calculated, and the result, shows that the constantQ 1 has the remarkable seasonal and spatial variation, while the coefficientQ 2 has relatively small variation throughout all seasons. Under the assumption of constant volume transport of 1.35×106 m3s–1 through the Tsugaru Strait, the long-term averages of the volume transport through the Tsushima and Soya Straits are estimated to be about 2.20 and 0.85×106 m3s–1 from the result of the mean surface heat flux, respectively.  相似文献   

20.
The Upper Cretaceous Mukalla coals and other organic-rich sediments which are widely exposed in the Jiza-Qamar Basin and believed to be a major source rocks, were analysed using organic geochemistry and petrology. The total organic carbon (TOC) contents of the Mukalla source rocks range from 0.72 to 79.90% with an average TOC value of 21.50%. The coals and coaly shale sediments are relatively higher in organic richness, consistent with source rocks generative potential. The samples analysed have vitrinite reflectance in the range of 0.84–1.10 %Ro and pyrolysis Tmax in the range of 432–454 °C indicate that the Mukalla source rocks contain mature to late mature organic matter. Good oil-generating potential is anticipated from the coals and coaly shale sediments with high hydrogen indices (250–449 mg HC/g TOC). This is supported by their significant amounts of oil-liptinite macerals are present in these coals and coaly shale sediments and Py-GC (S2) pyrograms with n-alkane/alkene doublets extending beyond nC30. The shales are dominated by Type III kerogen (HI < 200 mg HC/g TOC), and are thus considered to be gas-prone.One-dimensional basin modelling was performed to analysis the hydrocarbon generation and expulsion history of the Mukalla source rocks in the Jiza-Qamar Basin based on the reconstruction of the burial/thermal maturity histories in order to improve our understanding of the of hydrocarbon generation potential of the Mukalla source rocks. Calibration of the model with measured vitrinite reflectance (Ro) and borehole temperature data indicates that the present-day heat flow in the Jiza-Qamar Basin varies from 45.0 mW/m2 to 70.0 mW/m2 and the paleo-heat flow increased from 80 Ma to 25 Ma, reached a peak heat-flow values of approximately 70.0 mW/m2 at 25 Ma and then decreased exponentially from 25 Ma to present-day. The peak paleo-heat flow is explained by the Gulf of Aden and Red Sea Tertiary rifting during Oligocene-Middle Miocene, which has a considerable influence on the thermal maturity of the Mukalla source rocks. The source rocks of the Mukalla Formation are presently in a stage of oil and condensate generation with maturity from 0.50% to 1.10% Ro. Oil generation (0.5% Ro) in the Mukalla source rocks began from about 61 Ma to 54 Ma and the peak hydrocarbon generation (1.0% Ro) occurred approximately from 25 Ma to 20 Ma. The modelled hydrocarbon expulsion evolution suggested that the timing of hydrocarbon expulsion from the Mukalla source rocks began from 15 Ma to present-day.  相似文献   

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