庐枞火山岩盆地南部拔茅山铜矿深部找矿潜力分析     

程培生  王芝水 《中国地质调查》2018,5(6):18-23

位于庐枞火山岩盆地南部的拔茅山铜矿,是细脉带蚀变岩型脉状铜矿的代表。研究表明,其深部具有斑岩型铜矿的勘探潜力。为了进一步明确其深部找矿潜力,针对研究区斑岩型、热液型铜多金属矿的岩体、断裂、接触带等主要控矿因素,利用高精度磁法和可控源音频大地电磁测深(CSAMT)成果,分别对拔茅山岩体的分布、产状和深部形态及其与围岩的接触带特征进行了剖析。在此基础上,通过与沙溪斑岩铜矿地质、物探异常特征的类比,指明了研究区的找矿方向和有利找矿部位,为进一步找矿提供了思路和依据。  相似文献   

湖北省山区与平原雷电分布及其参数特征     

王学良  张科杰  余田野  汪姿荷 《气象科技》2019,47(2):337-348

为进一步了解山区与平原雷电参数分布特征及其差异,为山区和平原地区雷电防护工程设计和雷击风险评估提供参考,根据湖北省ADTD地闪定位系统2006年12月至2016年12月监测的资料,采用数理统计方法,对山区和平原地区的地闪频次、极性、雷电流幅值和波头陡度等参数分布特征进行了对比研究。结果表明:①山区地闪密度略高于平原地区,平原正地闪百分比稍高于山区,近10年的正地闪百分比呈上升趋势。②正地闪平均强度山区比平原大1.16kA,负地闪平均强度山区比平原小3.67kA,平原总地闪平均强度比山区大3.46kA。③总地闪小雷电流幅值(I≤30kA)概率山区比平原大8.9%,大雷电流幅值(I100kA)概率平原比山区大0.6%。④山区正地闪平均陡度分别比负、总地闪平均陡度大2.44kA/μs和2.31kA/μs,平原正、负、总地闪平均陡度分别比山区大3.41kA/μs、5.77kA/μs和5.64kA/μs。可以得出,山区小雷电流绕击率大于平原,正地闪雷电感应的危害大于负地闪和总地闪;平原地区大雷电流反击率比山区大,雷电感应的危害大于山区。  相似文献   

卫星地面站雷电直击效应防护设计探讨          下载免费PDF全文

孙俊德  李志鹏  赵洪升  王凯 《气象与环境科学》2019,42(2):124-128

卫星地面站雷电防护工程通常采用接闪杆作为天线主体的雷电直击效应防护措施,接闪杆的高度不仅影响其保护范围,而且影响其截闪概率。通过计算年预计雷击次数对截闪概率进行量化分析,结果表明,截闪概率近似与接闪杆高度平方成正比,采用过高的接闪杆将增大地面站遭受雷击电磁脉冲损坏的风险。为优化接闪杆设计,定义了保护体积的概念,并利用折线法与滚球法分别计算了三维立体空间内的保护范围。结果表明:接闪杆的保护范围与高度呈现非线性相关,当接闪杆超过一定高度(折线法超过30m,滚球法超过0.8倍滚球半径)后,对保护范围的影响十分有限;当接闪杆高度低于0.4倍滚球半径时,滚球法保护范围较大,反之则折线法保护范围较大。对接闪杆接闪瞬间周边的磁场强度分析结果表明,无屏蔽环境下地面站电子系统与接闪杆的常规距离远小于两者的理论安全距离,实际工程中难以通过增大接闪杆与卫星地面站的间距消除雷击电磁脉冲危害。为降低这一风险,卫星地面站直击雷防护应优先采用天线自带接闪杆的方式,条件不具备时也应尽量避免采用单支高大接闪杆,可选取适当的计算方法,采用多支较低接闪杆共同防护的方案。  相似文献   

青藏高原东部表土磁化率特征与环境意义   总被引：2，自引：0，他引：2  

陈慧  杨胜利  成婷  刘楠楠  李帅  梁敏豪  唐国乾 《冰川冻土》2018,40(6):1187-1194

现代表土磁化率与气候因子关系的研究是黄土古气候重建的重要内容,在黄土高原地区取得了重要进展,但在青藏高原地区相对不足。在青藏高原东部系统采集了106个表土样品,分析了其磁化率的变化特征;并通过表土磁化率与气候因子的相关分析,讨论了气候因子对高原东部现代表土低频磁化率和频率磁化率的影响。结果表明：研究区表土磁化率特征主要受到温度和降水量的影响,水热组合差异影响表土磁化率值的高低。低频磁化率与气候因子的相关性较弱,总体上与温度的相关性优于降水量,可能表明其与气候因子的关系比较复杂;频率磁化率百分比与降水呈较好的正相关关系,表明该指标对降水量的变化更为敏感,可以用于青藏高原东部的古降水定量重建。  相似文献   

中国航磁大地构造单元划分   总被引：4，自引：3，他引：1       下载免费PDF全文

熊盛青  杨海  丁燕云  李占奎 《中国地质》2018,45(4):658-680

本文以我国截止到2011年基本覆盖陆域及部分海域的航磁数据编制的全国航磁系列图为基础,以航磁反映的区域磁场和磁性基底起伏特征为依据,汲取主流大地构造观的划分理念,以板块构造理论及大陆动力学思想为指导,以磁场反映的构造特征为切入点,结合重力、遥感、地质资料对中国陆域构造单元进行划分。大地构造单元划分4个级别:一级构造单元为陆块区和造山系,共划分出8个;二级构造单元为陆块、弧盆系和地块,共划分出32个;三级构造单元为盆地、坳陷带(区)和隆起带(区),共划分出85个;四级构造单元为隆起和坳陷,共划分出332个。本划分方案旨在为油气地质构造背景研究及油气勘探提供一份地球物理资料。文中重点讨论了一、二级构造单元界线厘定的磁场依据及与前人划分存在的不同之处,而三、四级构造单元完全依据磁场及磁性基底起伏情况进行划分,并在盆地和坳陷区给出了深度信息,这为油气勘探者提供了必要的技术支撑。同时,借助丰富的航磁信息提示出一些地质构造方面难解现象,供同行专家参考与讨论。  相似文献   

区域地球化学评价中变异系数校正参数的意义     

刘明义  张晶  孟广路  胡立 《现代地质》2018,32(5):1074

通过对我国新疆西天山各地球化学区数据的归纳和研究,计算西天山12种常见成矿元素在各地球化学区的富集系数,提出校正系数公式,并将变异系数进行合理的校正与排序。与实际矿床和矿点结合,验证校正系数的正确性和适用性,预测元素成矿有利顺序和规律,总结出西天山富集系数与变异系数在成矿中的制约关系。该方法实现了不同成矿元素之间成矿条件的对比,拓宽了地球化学参数的适用性,提高了在勘探程度较低的地区地球化学评价方法的准确性,为地球化学评价提供科学依据。  相似文献   

Depositional setting,provenance, and tectonic-volcanic setting of Eocene–Recent deep-sea sediments of the oceanic Izu–Bonin forearc,northwest Pacific (IODP Expedition 352)     

Alastair H. F. Robertson  Steffen Kutterolf  Aaron Avery  Alan T. Baxter  Katerina Petronotis  Gary D. Acton 《International Geology Review》2018,60(15):1816-1854

New biostratigraphical, geochemical, and magnetic evidence is synthesized with IODP Expedition 352 shipboard results to understand the sedimentary and tectono-magmatic development of the Izu–Bonin outer forearc region. The oceanic basement of the Izu–Bonin forearc was created by supra-subduction zone seafloor spreading during early Eocene (c. 50–51 Ma). Seafloor spreading created an irregular seafloor topography on which talus locally accumulated. Oxide-rich sediments accumulated above the igneous basement by mixing of hydrothermal and pelagic sediment. Basaltic volcanism was followed by a hiatus of up to 15 million years as a result of topographic isolation or sediment bypassing. Variably tuffaceous deep-sea sediments were deposited during Oligocene to early Miocene and from mid-Miocene to Pleistocene. The sediments ponded into extensional fault-controlled basins, whereas condensed sediments accumulated on a local basement high. Oligocene nannofossil ooze accumulated together with felsic tuff that was mainly derived from the nearby Izu–Bonin arc. Accumulation of radiolarian-bearing mud, silty clay, and hydrogenous metal oxides beneath the carbonate compensation depth (CCD) characterized the early Miocene, followed by middle Miocene–Pleistocene increased carbonate preservation, deepened CCD and tephra input from both the oceanic Izu–Bonin arc and the continental margin Honshu arc. The Izu–Bonin forearc basement formed in a near-equatorial setting, with late Mesozoic arc remnants to the west. Subduction-initiation magmatism is likely to have taken place near a pre-existing continent–oceanic crust boundary. The Izu–Bonin arc migrated northward and clockwise to collide with Honshu by early Miocene, strongly influencing regional sedimentation.  相似文献   

Petrophysical characterisation of tight sandstone gas reservoirs using nuclear magnetic resonance: a case study of the upper Paleozoic strata in the Kangning area,eastern margin of the Ordos Basin,China     

Y. Y. Huyan  T. S. Liu  F. J. Jiang  X. Z. Chen  X. Q. Ma 《Australian Journal of Earth Sciences》2018,65(6):863-875

Residual and movable porosity are significant parameters for characterising petrophysical properties, especially in tight reservoirs. Eight tight sandstone samples from the upper Paleozoic gas-bearing strata in the Kangning area, from the eastern margin of the Ordos Basin, were analysed using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), petrography, and porosity and permeability tests. The lithology and pore types were identified and classified using petrography and SEM. The residual and movable porosity were obtained with NMR. In addition, NMR was used to visualise pore structure and pore size distribution. The results suggest that the upper Paleozoic sandstones in the study area mainly comprise feldspathic litharenite and litharenite. The sandstone porosity and permeability are low, with means of 5.9% and 0.549 mD, respectively. Four pore types exist in the tight sandstones: residual primary pores, grain dissolution pores, micropores (clay-dominated) and microfractures. The T₂ spectra under water-saturated conditions correlate with pore size and can be used to distinguish small and large pores based on the transverse relaxation time cutoff value of 10 ms, which corresponds to a pore diameter of 0.232 μm. Small pores account for 72% of the pores in the tight sandstones. The continuous bimodal T₂ spectra suggest good connectivity between small and large pores, despite the low porosity and permeability. In this study, the movable porosity of the major tight sandstone gas reservoirs is higher than the residual porosity, which confirms the effective evaluation of movable porosity to tight sandstone reservoirs, based on NMR experiments.  相似文献   

融雪洪水跳跃变异对其参数估计不确定性影响分析     

陈伏龙  张婷  冯平  何新林  李绍飞  龙爱华 《冰川冻土》2018,40(5):1004-1015

利用Pettitt非参数检验法和Mann-Kendall非参数趋势检验法,分析年最大洪峰流量序列的非一致性,确定序列的变异形式,采用“分解-合成”理论对其进行一致性修正,得到过去、现状两种条件下年最大洪峰流量序列,根据贝叶斯理论对序列一致性修正前后参数不确定性进行估计,并对其预报区间优良性进行评价。研究结果表明：年最大洪峰流量序列变异点发生在1993年,序列整体上升趋势不显著,在1957-1993年子序列呈显著下降趋势,而1994-2006年子序列变化趋势不显著,跳跃变异为序列主要变异形式;给出了实测、还原及还现序列参数后验分布估计值及95%置信区间,将其结合优化适线法进行P-Ⅲ型频率分析,得到修正前后设计频率年最大洪峰流量预报区间估计值;还原、还现序列与实测序列相比,预报区间覆盖率均提高24%,平均带宽分别减少39.59%、23.17%,平均偏移幅度分别减少28.45%、11.39%。通过对非一致性年最大洪峰流量序列还原/还现计算,可减小参数估计不确定性对其计算产生的影响,从而提高预报区间的可靠性。  相似文献   

Magnetic measurements in electrical prospecting by resistivity methods     

V.S. Mogilatov  N.O. Kozhevnikov  A.V. Zlobinsky 《Russian Geology and Geophysics》2018,59(4):432-437

The electrical resistivity and induced polarization (IP) methods are widely used in geological mapping, prospecting and exploration of mineral deposits, engineering geology, hydrogeology, archaeology, and geotechnical and environmental applications. Historically, these methods have formed the basis of the electrical prospecting technique. In these methods, a DC or low-frequency AC electrical current is introduced into the earth through a grounded transmitter line. The measured quantity is the electric field. However, if the earth’s resistivity or chargeability changes horizontally, this change gives rise to an anomalous magnetic field, which is studied by the magnetometric resistivity (MMR) and magnetic induced polarization (MIP) methods, respectively. Along with advantages, some shortcomings are inherent in the MMR and MIP techniques. Apparently, the main drawback of these methods is that the magnetic fields of both the transmitter line wire and ground electrodes on the surface are several orders of magnitude greater than the anomalous magnetic field response. This introduces a significant “noise” to magnetic-resistivity data. We investigate the potential of using a circular electric dipole (CED) in magnetometric resistivity techniques. It has been found that the application of a CED, instead of a conventional transmitter line, dramatically enhances the signal-to-noise ratio.  相似文献