Total Indicative Dose Determination in Water from the North Riviera Well Field of SODECI in Abidjan, Cote d’Ivoire

The Uranium-238 (238U), Thorium-232 (232Th) families and Potassium-40 (40K) are of terrestrial origin and contribute generally to an individual’s external exposure through our presence in this environment. They also contribute to the internal exposure through the ingestion of products and beverages such as water that are close to the earth. The aim of this work is to determine the committed effective dose or Total Indicative Dose (TID) due to gamma radioactivity of the borehole water from the Nord Riviera (NR) well field operated by the Côte d’Ivoire Water Distribution Company (SODECI) for the supply of drinking water to part of the population of Abidjan. In addition, the populations, with their habits, could use these borehole waters directly as drinking water. To this end, water samples from the seven (07) functional boreholes were collected and analyzed on a gamma spectrometry chain, equipped with an HPGe detector in the laboratory of the Radiation Protection Institute (RPI) of the GHANA Atomic Energy Commission (GAEC). The results of the specific activities of 238U, 232Th and 40K obtained were transcribed into TID. As the natural radioactivity of the borehole water is high [1], the TIDs calculated from the activity results of the natural radionuclides238U, 232Th, and 40K vary for the seven boreholes from 0.150 to 0.166 mSv/yr with an average of 0.161 ± 0.034 mSv/yr. The TID of the control tower, where the borehole water is mixed and treated for household use, is equal to 0.136 ± 0.03 mSv/yr. The TIDs obtained are therefore all slightly greater than the WHO reference dose value of 0.1 mSv/yr. But all remain below the UNSCEAR reference dose of 0.29 mSv/yr.

Three dimensional tectonic stress field in North China

According to the latest data of geological structure, geophysics, in-situ stress measurement and focal mechanism,3-D tectonic stress field model in North China is built and 3-D tectonic stress field pattern of North China aresimulated by finite element method. Then the overall characteristics and regional specific feature of North Chinaare studied. Finally, the influences of the valid dynamic boundary conditions of North China Block, active faultsand the inhomogeneity of crustal medium on tectonic stress field of North China are investigated.

Numerical modeling of tectonic stress field and fault activity in North China

On the basis of a 3-dimension visco-elastic finite element model of lithosphere in North China, we numerically simulate the recent mutative figures of tectonic stress field. Annual change characteristics of stress field are： 1 ） Maximum principal tensile stress is about 3 -9 kPaa-1 and its azimuth lie in NNW-SSE. 2） Maximum principal compressive stress is about 1 - 6 kPaa-1 and its azimuth lie in NEE-SWW. 3 ） Maximum principal tensile stress is higher both in the west region and Liaoning Province. 4） Variation of tectonic stress field benefits fault movement in the west part and northeast part of North China. 5 ）Annual accumulative rates of Coulomb fracture stress in Tanlu fault belt have segmentation patterns： Jiashan-Guangji segment is the high- est （6 kPaa - 1 ） , Anshan-Liaodongwan segment is the second （5 kPaa - l ） , and others are relatively lower （ 3 - 4 kPaa-1 ）.

Study on Evolution of Gravity Fieldand Earthquake Prediction in theNorth-south Seismic Belt and theEastern Qinghai-Xizang Block

The relation between the dynamic evolution feature of gravity field and strong seismicity is studied. The result shows that the regional gravity field variation enjoys inhomogeneity of spatial and temporal distribution and gravity change in different regions. It may be resulted from active faults and seismogenic process, and may be due to microdynamic activity of regional strain energy, which might be accumulated or released in different stages, and there exists transformation process of stress.

Characteristics and Formation Mechanism of the Geothermal Field in the North China Downfaulted Basin

The geothermal field is mainly controlled by the regional tectonic framework characterized by alternationsof uplifted and depressed basement. and exhibits a similar zoned distribution of temperatures. In the upliftedarea the geothermal gradient （G） and terrestrial heat flow value（q） of the Cenozoic sedimentary cover are rela-tively high, with G=3.5-5.0℃/100m and q=63-84mW/m;; whereas in the depressions they are rela-tively low, with G=2.7-3.5℃/100m and q=46-59mW/m;. In the whole region, G=3.58℃/100m and q=61.5±13.4nW/m;, indicating a comparatively high geothermal background and the presence of localgeothermal anomalies. A comparison of the results of mathematical simulation of the geothermal field with themeasured values shows a good agrecment between them. The geothermal difference between various tectonicunits is caused chiefly by the lateral and vertical variation of thermal properties of shallow crustal rocks. Thisphenomenon can be regarded as the result of redistribution of relatively uniform heat flows from the deep crustin the surficial part of the crust in the process of their upward conduction.

Assessment of Radioactivity in Borehole Waters of the North Riviera Sodeci Catchment Field in Abidjan, Côte d’Ivoire

The radioactive isotopes of the decay series of uranium-238 (238U), thorium-232 (232Th) and potassium-40 (40K) occur naturally in varying amounts in groundwater. They are the subject of many measures, mainly because of the risk they represent from a public health point of view. The purpose of this study is to measure the radioisotope content of borehole waters from the north riviera (NR) catchment field of the Ivorian drinking water distribution company (SODECI). These measurements will make it possible to assess the absolute levels of radioisotopes in the water from SODECI’s boreholes used directly for drinking or swimming, and possibly the associated risk from a public health point of view. To achieve this, a sampling campaign from the seven functional boreholes and the control or treatment tower took place in July 2018 at the NR well field. The analysis of radionuclides by gamma spectrometry was carried out in the laboratory of the Radiation Protection Institute (RPI) of the Ghana Atomic Energy Commission (GAEC). The naturally occurring radionuclides identified during the borehole water samples analysis are 238U, 232Th, and 40K. The results reveal that the specific activities of uranium vary from 0.45 ± 0.18 Bq/L to 0.55 ± 0.17 Bq/L with an average of 0.49 ± 0.15 Bq/L. Those of thorium vary from 0.66 ± 0.14 Bq/L to 0.78 ± 0.18 Bq/L with an average of 0.72 ± 0.16 Bq/L and potassium of 4.14 ± 0.53 Bq/L at 5.87 ± 0.60 Bq/L with an average of 5.32 ± 0.58 Bq/L.

THE REMOTE SENSING IN COAL GEOLOGY——A study on detection of coal spontanous burning by remote sensing in the coal fields in the north of China

The spontaneous burning has been lasting for thousands of years in the coal fields in the north of China. It spreads from the west (Tianshan coal field) to the east (Huolinhe coal field). Its E-W extension is up to 3750km, concentrating in N35°toN45°, its vertical depth up to 260m, and the surface temprature locally up to 270℃. Annually, it burns out 0, 250-300 million tones of coal, causing economic loss equivalent to 2-3 billion R.M.B. Yuan.It destroies coal resources and causes hazards in coal mines. In order to locate the extent and the direction in coal burning areas, the remote sensing technique has heen used and has produced an obvious benefit.

Estimating Field Source Parameters of Gravity Change in North China Based on the Euler Deconvolution Method

Based on the absolute and relative gravity observations in North China from 2009 to 2014,spatial dynamic variations of the regional gravity field are obtained. We employed the Euler deconvolution method and the theoretical model to get the best estimates of parameters. Gravity field change caused by the depth and distribution in North China is calculated by back analysis. The results show the structural index that equals 1 is suitable for inversion of the gravity variation data. The inversion results indicate that the depths of anomaly field sources are spread over the Hetao fault. The research method of this paper can be used in the quantitative study on the field source and may shed new light on the interpretations of gravity change, and also provide quantitative basis for earthquake prediction index criterions based on the gravity change.

North-South Asymmetry of the Interplanetary Magnetic Field Magnitude and the Geomagnetic Indices

Data of the daily interplanetary magnetic field (IMF), and the geomagnetic indices (aa, Ap, Kp, and DST) have been used to examine the asymmetry between the solar field north and south of the heliospheric current sheet, over the period (1975-2013). It important to note that during the positive polarity epochs: (T) refers to Toward the South of the heliospheric current sheet (Southern Hemisphere), and (A) refers to Away from North of the heliospheric current sheet (Northern Hemisphere). While, during the negative polarity epochs the opposite will be happened. The present study finds no clear indication of the presence of north-south asymmetry in the field magnitude, and also there is no magnetic solar cycle dependence that is evident. During the considered period, the north-south asymmetry for the considered parameters reaches maximum values around the declining phase or near to the minimum of the solar cycle. The geomagnetic indices have a clear asymmetry during the positive solar magnetic polarity period (qA > 0) and have a northern dominance during cycles (22 & 23) and southern dominance during cycles (21 & 24). From the power spectrum density, the considered parameters showed significant peaks which appeared in the north-south asymmetry but the 10.7 yr solar cycle was absent. In addition, the main periodicity of the asymmetry may be 5.2, 4.0 and 3.3 years that exist in the parameters with higher confidence levels. Finally, one can conclude that the asymmetry of the interplanetary parameters and the geomagnetic indices may provide multiple causes for producing the observed asymmetric modulations of cosmic rays.

Evolution of 3D tectonic stress field and fault movement in North China

Based on data of fault movement surveying, we simulate the evolution process of three dimensional stress field in North China by three dimensional finite element method. Evolutional patterns in one-year time scale from 1986 to 1997 have been illustrated and the evolution characteristics of stress field have been analyzed. In comparison with the seismic activity among that time interval in North China, we have primarily discussed the relationship between the evolution of stress field and seismic activity.

Numerical simulation of the crustal stress field by using data of deep geophysical exploration in the northern part of North China

DSS data of the last twenty years and more in the northern part of North China are further interpreted, and combined with other geological and geophysical data, the crustal model for the 3 D finite element method is built after straticulate crustal structure and elastic mechanics parameters are obtained. Referring to regional tectonic stress field and taking the effect of gravity into account, the paper constrains properly the model boundary and then computes the displacement of each nodal point and the strain and stress of each element by using the program from the 3 D linear elastic finite method. The relationship between the distribution feature of the crustal stress field and seismicity is discussed on the basis of analyzing contour maps of maximum principal compressive stress in the upper, middle and lower crusts.

后唐明宗朝北面行营与北部边防

北面行营的设置,是唐明宗措置军事的一项重要措施。在平定叛乱时,北面行营的主导力量是唐明宗亲信与元随以及中央的禁军。行营统帅的设置,体现了分权与制衡的原则。北面行营运行体现了唐明宗时期中央权力的发展,以及战时状态下唐明宗对于军事的掌控意愿。在战争结束后,北面行营成为后唐措置北边防御的重要机构。行营制衡的原则也运用在边防体系的构建之上,并与唐明宗的对外政策互为照映。在行营之内,唐明宗通过任命来自不同政治势力的行营统帅,派遣禁军出戍的方式,来实现行营权力的互相制衡。在后唐北部边防体系中,唐明宗设置北面行营署理河北边防,以期与负责河东边防的河东节度使实现军事上的互相制衡。但在北面行营的实际运行中,由于唐末帝时期中央激烈的政治变动以及契丹突然的军事介入,其军事上的平衡作用逐步丧失。北面行营反而成为赵德钧拥兵谋夺天下的资本。北面行营的运行反映了唐宋时期边防体制演进中对军事权力分割与制衡的趋势。

粤北长江铀矿田隆升剥露历史和矿床保存——来自磷灰石裂变径迹热年代学的启示

粤北长江铀矿田是中国南方最重要和最具代表性的花岗岩型铀矿田之一。前人关于长江铀矿田的研究工作主要涉及铀矿成因、成岩成矿时代和铀矿化机制等方面,关于控矿构造研究也集中在矿床形成过程方面(如导矿、运矿和储矿构造),对成矿后矿床的剥露历史和保存研究甚少。本文通过磷灰石裂变径迹测试,恢复了长江铀矿田热演化历史,结果显示晚白垩世末以来表现为单向隆升剥露降温过程,在约63~55 Ma和44~34 Ma存在两次快速隆升过程,约34~5 Ma冷却速率较慢,为构造平静期,5 Ma以来又发生了快速隆升。自75 Ma至今长江铀矿田的隆升剥蚀量为3 km左右。矿田内被NEE向棉花坑断裂和NWW向油洞断裂分割的书楼丘、棉花坑和长排三个矿区隆升剥蚀量差异非常微小,说明棉花坑断裂两侧和油洞断裂两侧在新生代时期没有明显的差异升降,也进一步佐证了棉花坑断裂和油洞断裂的活动性不大。结合控矿构造的发育特点、3.2~5.6 km的成矿深度以及相关的成矿温压条件,表明长江铀矿田深部资源保存良好,深部具有很大的找矿潜力。

辽东郑屯地区基于广域电磁法的深孔验证

辽东金矿床的发育被认为受变质核杂岩体系叠加拆离断层带控制,传统观点判定永宁盆地永宁组盖层厚度达到几千米以上,阻碍含矿流体的运移的同时,不利于形成大规模金属矿床。辽东地区矿床深部探测投入少、研究程度低,勘查探测深度长期局限于1 km以内。本文在郑屯地区采用广域电磁法获得了3 km以浅的电阻率分布特征,厘清了辽东盖层厚度为千米左右,突破了对永宁组巨厚盖层的传统认识;进一步施工2 km深钻开展验证,在孔深1 345 m处发现永宁组地层与下伏太古宙基底呈不整合接触关系,界面附近未见明显的构造拆离迹象。本研究证实永宁盆地盖层厚度仅为千米左右,结合区内多期活动断裂构造和密集分布的浅成岩脉群,初步判定永宁盆地的成矿地质背景类似胶东金矿集区,推测存在华北克拉通破坏时期含矿变质流体或岩浆热液运移至界面上部成矿的可能。辽东地区具有实现多金属找矿突破的潜力,广域电磁法勘探为深地成矿预测指明了方向。

基于PE-ANGO的MIMU现场标定方法

针对当前微惯性测量单元(MIMU)的现场标定方法存在标定步骤复杂、不利于非专业人员操作等问题,提出了一种基于先验知识增强的自适应北苍鹰优化(PE-ANGO)算法的MIMU现场标定方法。首先分析了MIMU涉及的误差并建立了加速度计和陀螺仪的目标函数,然后使用PE-ANGO算法求解目标函数并得到最优参数。为了使得标定工作易于现场操作,引入了一种用于传感器数据采集的手持MIMU来验证所提算法。仿真结果表明:PE-ANGO算法的标定精度相较于北苍鹰优化算法提高了一个数量级。实测实验表明:标定前后对俯仰角和横滚角累积误差的抑制效果分别提高了约89%和87%;与传统标定方法相比,对俯仰角和横滚角累积误差的抑制效果分别提高了71%和68%,验证了所提方法的有效性。

鄂尔多斯盆地中北部重力场及基底特征分析

鄂尔多斯块体是我国华北地区在新生代和现代构造活动中重要的活动块体,处于华北、华南和青藏3个板块的交接部位,其构造活动和动力学问题一直在基础地质问题领域中备受关注。同时,鄂尔多斯盆地作为我国重要的能源基地,查明基底特征对于区内沉积盖层构造变形、挠曲与次级断裂形成、深部物质和能量的交换、后期深部流体上升运移通道、中新生代盖层沉积碎屑物质来源、油气分布与富集、后期铀成矿铀源分析等也具有重要指示作用(王晓鹏等,2023)。

北羌塘坳陷东缘上三叠统巴贡组海相烃源岩特征及勘探启示

羌塘盆地北羌塘坳陷晚三叠世发育了一套分布广、厚度大的黑色泥岩,对油气勘探具有重要意义。为明确北羌塘坳陷东缘巴贡组黑色泥岩的有机地球化学特征,采集了石油沟地区61块浅井岩心和64块手钻柱塞样品,开展地球化学和矿物学技术分析,对烃源岩生烃潜力、沉积环境进行了评价。结果表明:(1)巴贡组黑色泥岩TOC分布在0.06%~5.81%之间,整体为一套差―中等烃源岩,部分达到优质烃源岩标准;形成于弱氧化―弱还原环境,有机质类型为Ⅱ_(2)―Ⅲ型,以混合型有机质为主;R_(o)分布在0.95%~1.90%之间,处于成熟晚期至高成熟阶段。(2)巴贡组烃源岩有机质丰度较高,有机质类型好,成熟度适中,生烃潜力大。(3)巴贡组烃源岩与上覆雀莫错组底部砂砾岩形成“下生上储”的源储组合,为大中型油气田的形成奠定了基础,同时巴贡组也是页岩油勘探的有利层系。这套烃源岩对北羌塘坳陷东缘常规油气和非常规油气勘探均具有重要意义。

Recent tectonic stress field and major earthquakes of the Bohai Sea basin

渤海位于北华北新生代裂陷盆地的东部，是一个晚第四纪形成的内陆海盆．渤海盆地活动断裂发育，地震活动强烈，交会于渤海中部的NE向营口潍坊断裂带北段、庙西北一黄河口一临邑断裂带及NW向北京一蓬莱断裂带是主要的活动构造带，将海区分成4个次级新构造区，成为现代应力场作用的构造基础．综合研究38个震源机制解和75个井区应力场等资料，以及构造应力场二维数值模拟计算结果表明，渤海及其邻区现代构造应力场的压应力方向为NE60°～90°，张应力为SN—NW30°；以水平和近水平应力作用为主；不同构造区主应力方向存在一定的差异．现今渤海地区地壳发育以NNE-NE和NW-WNW走向的共轭剪切破裂为特征，是控制地震活动的主要构造．

南北地震带北段及周边地区岩石圈磁场时空变化特征对地震活动的指示意义

基于南北地震带北段及周边地区2020~2022年流动地磁原始矢量资料,获得2期岩石圈磁场时空变化模型。结果表明,研究区磁偏角D、总强度F和垂直分量Z均由正异常高梯度带转变为负异常高梯度带,磁倾角I的0值线大致沿地块边界走向线展布。水平矢量和垂直矢量的幅值局部弱化及方向转变区主要分布在地块边缘和地块交界区域,矢量幅值和方向在地块边界、断裂带及周边区域以及断裂带两侧具有明显差异。历史震中磁异常变化表现为磁场各分量的0值线展布、高梯度带、水平矢量和垂直矢量的局部弱化及方向突变等特征。青藏地块东北缘、阿拉善地块东南缘、鄂尔多斯地块西北缘及以北地区岩石圈磁场异常特征明显。

神木北地区上古生界断裂构造分析及其影响

神木北地区位于鄂尔多斯盆地的东北部,富集油气资源,其在上古生界太原组、山西组和石盒子组上发育小型正断层、逆断层、个别切割能力较强的走滑断层及高角度裂缝,由构造作用产生的断层、裂缝及后期由烃源岩内部异常高压使泥岩破裂所形成的裂缝都影响油气运移和油气田分布。该文利用地震资料、钻井资料、测井资料和成像资料结合人工地震合成记录标定法、野外露头调查法等对地震资料处理、解释和结合野外露头调查法、岩心观察法,镜下薄片鉴定法和成像测井方法等识别裂缝构造、发育类型和发育基本规律,上述方法对神木北地区的油气资源勘探,具有重要的研究意义和具体的应用价值。