Application of fractal models to characterization of vertical distribution of geochemical element concentration

Characterization of the vertical distribution of geochemical element concentration is essential for economic planning in the mining industry. 10 mineralized boreholes and 1 non-mineralized borehole from the Qulong copper deposit, Tibet, western China, were collected to identify the vertical distribution properties of Cu values using fractal models. The vertical distribution of Cu values in mineralized and non-mineralized boreholes shows a positive skewed distribution in the former and multimodal distribution in the latter. The results obtained by the box counting method show that the vertical distributions of Cu values in mineralized and non-mineralized boreholes exhibit self-similarity with box dimensions ranging from 1.28 to 1.37. The box dimensions of mineralized boreholes are greater than that of Cu values in the non-mineralized borehole, indicating that the mineralization makes the distribution of Cu values more irregular. The power-law frequency analysis reveals that Cu values in mineralized boreholes are bifractal. The two portions of the plot define a crossover point at 0.33%, for Cu values less than and greater than 0.33, fractal dimensions range from 0.1 to 0.65, in non-mineralized rocks, and range from 2.71 to 5.79, in the mineralized rocks. Hurst exponents for mineralized boreholes occur at 0.8, which are greater than 0.5, indicating that Qulong copper deposit has a good continuity of mineralization.     

中国锡矿床时空分布特征与潜力评价

锡矿是中国传统优势矿种,但是近年来遇到了找矿潜力区不足和找矿方向不明等问题,急需进一步分析和总结其地质特征、成矿规律和资源潜力,为今后地质找矿工作提供借鉴。文中采用矿床模型综合地质信息预测方法,在各省区锡矿资源潜力预测成果的基础上,以MapGIS为平台,进行数据库汇总与综合分析研究。首先,基于全国893处锡矿产地数据的统计分析,初步总结了中国锡矿时空分布特征,岩浆岩、构造和地层等控矿因素。其次,根据锡矿床及预测区的空间分布和大地构造单元,划分了44个锡矿成矿区带。再次,将锡矿的预测类型划分为石英脉型、锡石硫化物型、夕卡岩型、云英型、伟晶岩型、火山岩型和砂矿型,并建立了主要锡矿类型的预测模型。最后,在全国范围累计圈定1 179个最小预测区,累计预测资源量1 861.13×104 t。根据锡矿区域成矿特征,将最小预测区归并为405个二级预测区,并进一步合并为109个锡矿三级预测区,其中找矿潜力大的湖南香花岭-千里山和塔山-大义山、云南个旧和薄竹山-都龙、内蒙古黄冈梁等5个三级预测区可优先部署锡矿勘查工作。预测结果还表明锡矿在500 m以浅的找矿空间里仍有很大资源潜力,因此,找矿工作应注重深浅结合,在重视老矿山深部外围找矿的同时,还应重视覆盖区和非传统锡矿类型等新领域的找矿勘查。     

中国稀土矿资源成矿地质特征与资源潜力分析

稀土元素是元素周期表中15种镧系元素以及钪、钇等17种元素的总称。由于其在材料、冶金等行业具有难以替代的作用,因而有“工业维生素”之称。作为具有战略意义的优势矿产资源之一,中国稀土资源由于近几十年的过度依赖极少数超大型矿床以及资源过度开采等问题,其占世界稀土资源储量的比重急剧下降。因此,急需进一步分析和总结其地质特征、成矿规律以及资源潜力评价。中国是世界稀土资源大国,稀土矿矿床类型齐全,前人针对其成矿理论方面也做了大量工作。本文采用矿床模型综合地质信息预测方法,在全国各省份稀土矿成矿潜力预测结果的基础之上,以MapGIS软件为平台,进行数据库汇总与综合分析研究。根据中国稀土时空分布、岩浆岩、构造和地层等控矿因素以及大地构造单元,划分了17个稀土矿成矿区带。同时,筛选出不同成因的典型矿床,总结其成矿地质特征及成矿模式。在此基础上,建立了沉积变质型、岩浆型、风化壳离子吸附型等稀土矿预测模型。在全国范围内总计圈定了930个稀土矿最小预测区,累积预测资源量约32 700×104 t。根据稀土矿区域成矿特征,将最小预测区归并为2级预测区,并进一步归并为133个3级预测区。此外,根据不同成矿带,按照不同预测深度、不同地质可靠程度以及不同利用程度对稀土资源量进行了汇总。最后根据稀土矿成矿地质条件,选取了广西云开大山、大寺-小董, 内蒙古白云鄂博、巴尔哲, 湖北庙娅-蒋家堰以及四川冕宁等6个重点的3级预测区进行资源潜力分析,为下一步勘查部署工作提供指导。     

福山凹陷流沙港组低渗储层孔隙特征及成因

通过普通薄片、铸体薄片、X射线衍射、扫描电镜和压汞等资料的综合分析,研究了北部湾盆地福山凹陷古近系流沙港组储层的孔隙特征,并结合储层的沉积环境、岩性特征和成岩作用,分析了影响储层孔隙发育的主要因素。结果表明,研究区流沙港组储层属中低孔低渗储层,以次生孔隙为主,孔隙类型主要为粒间溶孔、粒内溶孔,纵向发育3个次生孔隙带。影响储层孔隙发育的因素主要为沉积相带及成岩作用,其中沉积相带的不同导致了储层岩石成熟度的差异,进而控制原始孔隙度的大小,优质储层主要分布在辫状河三角洲前缘水下分流河道及河口坝附近。较强的压实作用、胶结作用对原生粒间孔的破坏是造成研究区低渗的重要原因,而溶蚀作用的强度决定了优质储层的发育状况。     

Pull-out behaviour of wood bolt fully grouted by PS-F slurry in rammed earth heritages

This article presents a laboratory and field investigation of pull-out resistance of wood bolts in rammed earth heritages. The laboratory testing involved axial tensile tests of four grout specimens prepared in specially designed moulds using PS-F (Potassium Silicate solution-Fly ash) slurry to investigate the performance of anchors. The field testing involved pull-out tests of three wood anchors installed in rammed earth heritages by gravity grouting. Experiments reveal that the failure mode is the pull-out of bolt from grout and average skin friction resistance of bolt–grout interface is approximately 0.34MPa. Load–displacement curves and elastic–residual displacement derived from cyclic loading indicate such anchor system has strong ductility with small elastic deformation and large residual deformation. Bond collapse firstly occurs at the loaded end and then propagates towards the full bonded length. Bond stress distribution is not uniform along the bonded length. Maximum bond stress distributes at the range from 0.3 m to 0.4 m. Emergence of compressive strain in the interface reveals such anchor system enjoys the advantages of both tensile and compressive anchor types, which significantly differs from results from other regular bolts. The research conclusion makes scientific senses to traditional material and craft in rammed earth heritages.     

西藏灌木林景观格局特征

应用景观生态学原理与方法,对西藏全区划分了景观要素,选取了10个景观指数,定量研究了斑块水平和景观要素水平上西藏主要类型灌木林的景观格局特征.结果表明,西藏各类型灌木林斑块大小均服从反J型分布,斑块面积越大,斑块数量越少,所占的面积比例越高.总体上,灌木林面积占景观总面积的4.6%,灌木林斑块数占总斑块数的54.8%.各个具体类型的灌木林在斑块大小、斑块形状和景观镶嵌度等方面均具有不同的格局特征.     

Evaluation of the uncertainty in estimation of metal resources of skarn tin in Southern China

This study is concerned with the problem of how many undiscovered mineral deposits can be expected to occur in the vicinity of any known deposit, especially if the deposit is nearly mined out. Skarn tin deposits in southern China were chosen to demonstrate that fractal modeling can be a useful tool to characterize the spatial–temporal distribution of mineral deposits, and to quantify their grades and tonnages. The results show that the spatial–temporal distribution of skarn tin deposits as well as their grades and tonnages satisfy fractal statistic, and suggest that 14 skarn tin deposits could be found around a known skarn tin deposit within a radius of 80 km. Monte Carlo simulation was used to combine the number of deposits and the frequency distributions of grade and tonnage and to capture the uncertainty in estimation of metal resources. At the 90%, 50% and 10% confidence levels, tin metal resources amount to 6 ton, 200 ton, and 1.0 × 10⁴ ton around a known tin deposit within a radius of 80, respectively.     

东营凹陷中央背斜隆起带形成机制分析

重建了东营凹陷构造演化过程 ,提出在盆地古近纪同裂陷期充填序列中 ,沙三段底界面S6′界面具有构造变格意义 ,过该界面盆地的构造应力场发生了由近南北向拉伸到NW—SE向拉伸的转换。在此基础上重新解析了盆地中央背斜隆起带 ,并指出中央背斜带是一个复合的构造系统。其东段的辛镇背斜的性质为受控于陈南铲式断层的大型伸展断弯褶皱 ,主要的活动期为Ek—Es下3 时期 ;而其西段为东营—梁家楼—现河弧形生长滑脱断裂系统的组成部分 ,主要形成于Es上3 —Es2 沉积时期。上述认识对于中央背斜隆起带油气勘探具有重要的意义。     

波浪式拖管法铺设海底管道力学性能研究

海底管道铺设是海洋油气资源开发的重要环节,传统的拖管法不能很好地适应海洋深度和复杂环境的变化。针对 Acergy公司在Girassol项目中提出的一种波浪式拖管方法,对其应用于2.0 km 长海底管道铺设进行分析。首先,结合深水海洋环境特征,采用集中质量法建立管道拖航数值模型,并介绍管道、拖缆和浮筒力学计算及水动力荷载计算方法;其次,基于非线性有限元OrcaFlex软件对拖管过程建模,以模拟实际项目拖管过程;然后,通过对比相同条件下的单波式和双波式两种拖管方式,探讨管道和拖缆的动态力学性能变化;最后,针对不同浮重比、拖航速度、拖缆长度和悬垂角、海流流速和流向角等因素展开敏感性分析。结果表明：波浪式拖管法可以有效地降低施工时对拖缆的张力需求,但也会因此增加管道局部弯矩和应力响应;相对于单波式拖管,双波式拖管在缓解由于拖航速度等变化而产生的管道局部损伤效应上更有优势,并能较好地适应不同水深环境;复杂的海流工况对拖航时管道的力学性能影响十分显著,施工前应选择合适的铺设窗口期以防止管道产生损伤。     

不同的大气云模式对月预报影响的数值试验

所用的 T42L10月长期数值预报谱模式采用了模式诊断云方案,在辐射计算中,用模式的预报水汽场和模式诊断云代替原民T42L9中的气候纬向平均水汽场和云,模式诊断云计算中还考虑了大地形作用对云的影响.本文利用国家气象中心1992年8月31日的客观分析资料为初始场,进行30天长期数值预报,对比研究了这两种不同的云模式对月际数值预报的影响.模式诊断云方案的预报明显优于气候云方案,采用模式诊断云预报的500hPa 高度场月平均的倾向相关系数有所提高,月平均预报误差减少.模式诊断云方案的预报误差低于对应的持续性误差.模式诊断云方法由于考虑了在预报时间内云分布的时间和空间变化,提高了模式中的辐射计算精度,从而改进模式中的云、辐射作用,克服由于气候云方法所出现的预报偏差,较显著地改善月际数值预报效果.