Application of numerical modelling to a case of compaction-driven dolomitization: a Jurassic palaeohigh in the Po Plain, Italy     

ALBERTO CONSONNI  PAOLA RONCHI  CLAUDIO GELONI†  ALFREDO BATTISTELLI†  DOMENICO GRIGO  SIMONA BIAGI‡  FABRIZIO GHERARDI‡  GIOVANNI GIANELLI‡  Associate Editor: Dave Cantrell 《Sedimentology》2010,57(1):209-231

Dolomitization of a carbonate platform can occur at different times and in different diagenetic environments, from synsedimentary to deep burial settings. Numerical simulations are valuable tools to test and select the model that, among different hypotheses compatible with field and geochemical data, best honour mass balance, kinetic and thermodynamic constraints. Moreover, the simulation can predict the distribution of the dolomitized bodies in the subsurface and evaluate porosity changes; valuable information for the oil industry. This study is the first attempt to reproduce and investigate the compaction dolomitization model. The diagenetic study of the Jurassic carbonate basin and palaeohigh system of the Po Plain indicates that the carbonates of the palaeohighs were dolomitized by basin compaction fluids. The main goal of the simulations is to evaluate the origin and evolution of the dolomitizing fluids and to provide insights regarding the distribution of the potential reservoir‐dolomitized bodies in the Po Plain. The modelling process is subdivided into two steps: basin modelling and reactive transport modelling. The SEBE3 basin simulator (Eni proprietary) was used to create a three‐dimensional model of the compacting system. The results include compaction fluid flow rate from the basin to the palaeohigh, compaction duration and a determination of the total amount of fluid introduced into the palaeohigh. These data are then used to perform reactive transport modelling with the TOUGHREACT code. Sensitivities on dolomite kinetic parameters suggest that dolomitization was an efficient process even at low temperatures, with differences mainly related to the dynamics of the process. Fluid composition is one of the main constraints, the sea water derived compaction fluid is proven to be efficient for dolomitization due to its relatively high Mg content. Simulations also confirmed that permeability is the most important factor influencing fluid flow and, consequently, the dolomite distribution in the formation. Permeable fractured zones have a strong influence, diverting the dolomitizing fluids from their normal path towards overlying or lateral zones. Moreover, the simulations showed that, after dolomite replacement is complete, the dolomitizing fluids can precipitate dolomite cement, causing over‐dolomitization, with related localized plugging effects in the zone of influx. Mass balance calculations indicate that in the dolomitization compaction model, the amount of compaction water fluxed from the basin to the carbonate is the main constraint on dolomitization efficiency. This observation implies that the ratio between the volume of the basin undergoing compaction and the volume of the palaeohigh is a limiting factor on the final size of the dolomitized bodies. An isolated palaeohigh could be an ideal site for pervasive replacement dolomitization due to the large volume of compaction fluids available compared with the carbonate rock volume. In the case of large platforms, the more permeable margin lithofacies are the most likely sites for compaction model dolomitization. The combined use of a basin simulator and reactive transport modelling has proved to be a successful method to verify model reliability and it provides insights into the volumetric distribution of diagenetic products.  相似文献   

矿床空间分布的分形研究及其找矿意义——以三江南段银铅锌矿床分布为例   总被引：2，自引：0，他引：2  

董方灵  曹月怀  胡官兵 《华南地质与矿产》2010,(1):48-54

矿床的空间分布规律对地质勘查和找矿工作具有指导作用,三江南段地区是我国重要的多金属成矿区带,因此在该地区使用现代数学理论来研究矿床的空间分布规律具有重要意义。本文在深入研究三江南段地区银铅锌成矿机理、成矿地质背景以及数盒子法(Box-counting method)的基础上采用近年来广泛使用的关联维数来研究该地区银铅锌矿床的空间分布规律。首先借助G IS技术量测了13个银铅锌矿床之间的距离,用不同的标度r及其对应的关联函数C(r)得到一点对序列(r,C(r)),然后通过在平面坐标下作出(lnr,lnC(r))的散点图,使用最小二乘法拟合直线来估算关联维数,整体拟合得到的关联维数D=0.875;分段拟合得到的关联维数D1=0.184、D2=1.00。研究结果表明三江南段地区的银铅锌矿床在空间上具有分形丛集分布的特征。依据本次研究,将该地区划分为三个银铅锌矿密集区,并就该地区找矿工作提出指导意见,同时也探讨了关联维数与盒子维数的差异。  相似文献   

华北东部平原浅层高矿化弱渗透地下水的开发技术示范研究   总被引：2，自引：0，他引：2  

刘少玉  靳盛海  韩双平  宋书红  王哲  周晓妮 《吉林大学学报(地球科学版)》2010,40(1):114-120

开发利用华北东部低海拔平原浅层弱渗透含水层地下水,是挖掘水土资源潜力与提高光热生物环境资源利用水平的关键问题。通过借鉴国内外经验和现场勘查设计施工,在天津、沧州、衡水和济阳等地成功建立了"抽咸换淡辐射井"、"河水-雨洪水-潜水循环利用井"、"虹吸连通增采井"等不同类型示范工程,取得了在低成本条件下的良好效果。这既解决了淡水、微咸水、甚至是咸水地区的农业灌溉用水问题,也使浅层咸水大规模改造利用成为可能,为合理开发利用水土资源开辟了一条可行的途径。  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987110000113   总被引：3，自引：0，他引：3  

Xueqi Xi  Zhongfang Yang  Yan Liao  Yujun Cui  Yansheng Li 《地学前缘(英文版)》2010,1(1):125-132

<正>Against the current background of global climate change,the study of variations in the soil carbon pool and its controlling factors may aid in the evaluation of soil's role in the mitigation or enhancement of greenhouse gas.This paper studies spatial and temporal variation in the soil carbon pool and their controlling factors in the southern Song-nen Plain in Heilongjiang Province,using soil data collected over two distinct periods by the Multi-purpose Regional Geochemical Survey in 2005—2007, and another soil survey conducted in 1982—1990.The study area is a carbon source of 1479 t/km~2 and in the past 20 years,from the 1980s until 2005.the practical carbon emission from the soil was 0.12 Gt.Temperature,which has been found to be linearly correlated to soil organic carbon,is the dominant climatologic factor controlling soil organic carbon contents.Our study shows that in the relevant area and time period the potential loss of soil organic carbon caused by rising temperatures was 0.10 Gt,the potential soil carbon emission resulting from land-use change was 0.09 Gt,and the combined potential loss of soil carbon(0.19 Gt) caused by warming and land-use change is comparable to that of fossil fuel combustion(0.21 Gt).Due to the time delay in soil carbon pool variation,there is still 0.07 Gt in the potential emission caused by warming and land-use change that will be gradually released in the future.  相似文献   

Impact of the shrinking winter wheat sown area on agricultural water consumption in the Hebei Plain简   总被引：6，自引：2，他引：4  

WANG Xue  LI Xiubin  XIN Liangjie 《地理学报(英文版)》2014,24(2):313-330

This study firstly analyzed the shrinkage of winter wheat and the changes of crop- ping systems in the Hebei Plain from 1998 to 2010 based on the agricultural statistic data of 11 cities and meteorological data, including daily temperature, precipitation, water vapor, wind speed and minimum relative humidity data from 22 meteorological stations, and then calcu- lated the water deficit and irrigation water resources required by different cropping systems, as well as the irrigation water resources conserved as a result of cropping system changes, using crop coefficient method and every ten-day effective precipitation estimation method. The results are as follows. 1） The sown areas of winter wheat in the 11 cities in the Hebei Plain all shrunk during the study period. The shrinkage rate was 16.07% and the total shrinkage area amounted to 49.62×10^4 ha. The shrinkage was most serious in the Bei- jing-Tianjin-Tangshan metropolitan agglomerate, with a shrinkage rate of 47.23%. 2） The precipitation fill rate of winter wheat was only 20%-30%, while those of spring maize and summer maize both exceeded 50%. The irrigation water resources demanded by the winter wheat-summer maize double cropping system ranged from 400 mm to 530 mm, while those demanded by the spring maize single cropping system ranged only from 160 mm to 210 ram. 3） The water resources conserved as a result of the winter wheat sown area shrinkage during the study period were about 15.96×10^8 m^3/a, accounting for 27.85% of those provided for Beijing, Tianjin and Hebei by the first phase of the Mid-Route of the South-to-North Water Diversion Project.  相似文献   

Effects of Nitrogen Addition on Plant Functional Traits in Freshwater Wetland of Sanjiang Plain,Northeast China   总被引：1，自引：0，他引：1  

MAO Rong  ZHANG Xinhou  SONG Changchun 《中国地理科学(英文版)》2014,(6):674-681

To clarify the responses of plant functional traits to nitrogen（N） enrichment, we investigated the whole-plant traits（plant height and aboveground biomass）, leaf morphological（specific leaf area（SLA） and leaf dry mass content（LDMC）） and chemical traits（leaf N concentration（LNC） and leaf phosphorus（P） concentration（LPC）） of Deyeuxia angustifolia and Glyceria spiculosa following seven consecutive years of N addition at four rates（0 g N/（m^2·yr）, 6 g N/（m^2·yr）, 12 g N/（m^2·yr） and 24 g N/（m^2·yr）） in a freshwater marsh in the Sanjiang Plain, Northeast China. The results showed that, for both D. angustifolia and G. spiculosa, N addition generally increased plant height, leaf, stem and total aboveground biomass, but did not cause changes in SLA and LDMC. Moreover, increased N availability caused an increase in LNC, and did not affect LPC. Thus, N addition decreased leaf C∶N ratio, but caused an increase in leaf N∶P ratio, and did not affect leaf C∶P ratio. Our results suggest that, in the mid-term, elevated N loading does not alter leaf morphological traits, but causes substantial changes in whole-plant traits and leaf chemical traits in temperate freshwater wetlands. These may help to better understand the effects of N enrichment on plant functional traits and thus ecosystem structure and functioning in freshwater wetlands.  相似文献   

江汉平原西部浅层孔隙水水文地球化学特征          下载免费PDF全文

何军  肖攀  彭轲  许珂 《中国地质调查》2014,6(5):36-42

为了揭示地下水由江汉平原周缘向中心径流过程中的水质演化和复杂的水文地球化学作用,以江汉平原西部地区为例,通过数理统计、水化学、同位素地球化学、离子比值关系等方法,开展了江汉平原西部边缘地带浅层孔隙地下水的水文地球化学特征研究。结果表明: 平原区孔隙水以HCO₃-Ca·Mg型为主,丘岗区(丘陵和岗地)主要是HCO₃-Ca·Mg型,少量为HCO₃·SO₄-Ca·Mg型,还出现了HCO₃·NO₃-Ca·Mg型水,总溶解固体(total dissolved solids,TDS)升高主要是由于碳酸盐岩的溶解; 浅层孔隙水均来源于大气降水,蒸发作用对该地区孔隙水的影响较小; 方解石、白云石和石膏的溶解主导研究区的水文地球化学过程,也是孔隙水中Ca²⁺、Mg²⁺的主要来源,Na⁺和K⁺的主要来源是阳离子交换吸附。  相似文献   

松嫩平原东部浅层地下水水化学特征及水质评价          下载免费PDF全文

高月  卞建民  张真真 《水文》2014,34(4):50-54

针对松嫩平原东部浅层地下水环境特征及存在的问题,利用该区地下水水质检测数据进行了水化学特征分析,利用1983年、1993年、2003年及2012年四个时段的地下水水质资料进行了对比分析,水质出现了明显的变化,在此基础上采用支持向量机法进行了水质现状评价。结果表明:第四系潜水及承压水中Fe、Mn含量较高,总硬度最大值1321.12mg/L,溶解性总固体最大值2214.45mg/L,水化学类型均为矿化度不大于1.5g/L的HCO3-Ca型水。NO3-、NH4+、Cl-、SO42-的含量呈现逐年增加的趋势,同时也出现了原来没有的酚、Cr6+等有毒物质。潜水Ⅰ、Ⅱ、Ⅲ类水样点占总样本的12.03%,Ⅳ、Ⅴ类水占总样本的87.97%。承压水Ⅰ、Ⅱ、Ⅲ类水占总样本的10.83%,Ⅳ、Ⅴ类水占总样本的89.17%。该方法评价结果与综合指数法结果一致率达95%,因此,评价结果可为该区水资源管理提供科学指导。  相似文献   

ESTIMATION AND EXPLOITATION OF WATER RESOURCES IN THE SANJIANG PLAIN     

郭大本 《中国地理科学(英文版)》1991,1(2):141-153

According to practical measurement and related data, the writer discusses the main features of rivers in the Sanjiang Plain and the change of water balance with time and space, and then estimates water resources of five types, namely, runoff, ground water, soil water, and water supplied by three rivers and lakes (or reservoirs).The total volume of the above-mentioned water resources can be up to 31.5 billion m3. But they are rather unevenly distributed and the annual change is considerable, too. Up to now, only 8.3% of water resources have been utilized. According to a programme, 17.5 billion m3 will be utilized in the future in the district. Rationally exploiting water resources in the district should be combined with protection and management, and the sole criterion for judging rationality of utilization is that whether it is beneficial to economic, ecologic and social aspects.  相似文献   

Interactions between groundwater and surface water in a virginia coastal plain watershed. 1. Hydrological flowpaths     

Keith N. Eshleman  John S. Pollard  Anne K. O'Brien 《水文研究》1994,8(5):389-410

A field study of surface water and groundwater interactions during baseflow and stormflow conditions was performed at the Reedy Creek watershed in the Virginia Coastal Plain. Three estimates of the average saturated hydraulic conductivity (K_s) of the unconfined aquifer were in reasonable agreement (ranging from 0.0033 to 0.010 cm/s), indicating that baseflow in the creek is entirely from the drainage of shallow groundwater from the relatively thin (1–6 m thick) unconfined aquifer. This relatively permeable surficial aquifer was found to be underlain by dark, olive grey, clay-silt and diatomaceous Miocene deposits of low permeability known as the Calvert Formation, which is believed to function as a confining bed in the area. A chemical hydrograph separation technique was used to resolve the contributions of [old] (pre-event) and [new] (event) water to stormflow. Results from a major rainstorm indicated that old water dominated the stormflow response of the watershed, although the new water contribution approached 40% at the hydrograph peak. Stormflow at Reedy Creek appears to result from saturation overland flow from variable source areas which include the stream channels and a significant part of the riparian wetland area. This response appears to be attributable to the transient dynamics of the shallow groundwater flow system and to the formation of localized groundwater mounds which raise the water-table to the wetland surface.  相似文献