超基性岩红土风化壳中镍的表生富集规律及矿化结构研究 ——以印尼苏拉威西岛Kolonodale矿区为例

文章选取印尼苏拉威西岛Kolonodale红土型镍矿区为研究区,对201个浅井剖面共采取3 161件风化壳样品,进行了w(Ni)值的测试,以揭示超基性岩红土风化壳中Ni的表生富集规律及矿化结构特征。研究结果表明,在平面上,矿区内风化壳的w(Ni)平均值的高低与地形地貌关系密切。斜坡带、坡脚堆积带的风化壳为含镍高值区,其w(Ni)值为0.8%~1.8%;山顶平台区、山脊的风化壳为含镍低值区,其w(Ni)值为0.7%~1.4%。在垂向上,风化产物的w(Ni)值的高低与取样深度及样品属性密切相关。w(Ni)值随着红土带→腐岩带→基岩带的变化出现低值(0.85%~1.55%)→高值(1.15%~4.75%)→低值(≤0.55%)的波动变化规律。矿层的产状(分布、深度、厚度)与风化壳产状之间表现出明显的正相关关系。矿区内的低品位矿层〔1.5%≤w(Ni)≤2.0%〕和高品位矿层〔w(Ni)≥2.0%〕单独或组合发育,产出"正常型双层矿化"、"倒置型双层矿化"、"低品位单层矿化"、"高品位单层矿化"和"叠层矿化"等5种矿化结构类型。综合分析认为,富镁及中等程度蛇纹石化的超基性岩母岩、热带雨林气候环境是矿区内发育富镍红土风化壳的首要条件。吸附、离子交换以及次生沉淀等3种成矿作用的共同发育,导致了红土风化壳中Ni表生矿化的连续性、矿石类型的多样性及特高品位矿石的形成。矿床中矿化结构类型的多样化是区域构造背景、地形地貌、构造发育、水文条件等诸多因素耦合作用的结果。文章指出,在今后的红土型镍矿床的找矿勘查过程中,需要综合考虑各类内、外生控矿因素对矿床发育的影响,总结矿区尺度的矿化结构规律,可有效地指导矿床勘查工作。     

河南泌阳凹陷新生代天文地层研究

为油气成烃成藏定量研究,特别为油田剥蚀量的计算,需要建立新生代天文地层年代表。该表的数据是立足于天文学"米氏旋回假说"中地球轨道三要素的周期性和准周期性变化,求出各组(段或亚段)地质年龄。计算方法是选定泌阳凹陷11口井从大仓房组至凤凰镇组的地层分层、测井曲线数据等作频谱分析,寻找响应0.405Myr周期中的最大优势旋回和提出的三个‘基准面'的绝对年龄值。研究和计算的最后成果年龄为:1)大仓房组‘红层'顶/核三4亚段底是以邻近渤海湾盆地东营凹陷沙四下亚段‘红层'顶42.671Ma作为年龄对比和标定,向上计算出核三3亚段底为40.951Ma、核三3～1亚段顶为36.490Ma,核二段的顶为34.845Ma;2)廖庄组底/核一段之间是以邻近渤海湾盆地东营凹陷东营组底32Ma计算的数据作对比和标定,向下计算出核一段底的年龄为34.468Ma,核二段/核一段之间可能为一个大约时长为0.4Myr的小剥蚀面;向上计算廖庄组现有顶平均年龄为26.811Ma,即泌阳凹陷廖庄组全沉积的顶在中新世23.03Ma,地质构造上升和沉积回剥时间平均为3.781Myr;3)平原组底界的年龄标定为目前"国际地层表"(2004)中年龄为2.588Ma,向下计算出凤凰镇组底界平均年龄为4.155Ma。     

色谱法在稀土元素分离分析研究中的应用进展

稀土作为一种重要的不可再生资源,在各行业的应用正逐渐被人们所重视。色谱技术以其快速、高效、自动化程度高等优势已成为稀土元素分离分析的主要方法。文章总结了纸色谱法、薄层色谱法、气相色谱法、超临界色谱法、高效液相色谱法、毛细管电泳法等色谱法在稀土元素分离分析中的应用及研究概况。其中,纸色谱法因展开时间过长,分离效果不理想已很少应用;薄层色谱法因其操作方便、设备简单、显色容易等优点,可用于稀土元素分离分析的初步检测;气相色谱法由于对样品热稳定性的限制,以及因常用的β-二酮类稀土螯合物配体存在分辨率差和吸附等问题也很少应用;超临界色谱法在分离稀土元素络合物中分离效果较好,但是仪器难以普及,限制了技术的发展;高效液相色谱法因分离效率高、重复性好、自动化操作等优点已成为目前稀土元素分离分析的主要方法;毛细管电泳法具有高效、样品及试剂用量少、操作模式灵活等优点,在稀土元素分离分析方面更具有广阔的发展空间。     

Linear Elastic and Cohesive Fracture Analysis to Model Hydraulic Fracture in Brittle and Ductile Rocks

Hydraulic fracturing technology is being widely used within the oil and gas industry for both waste injection and unconventional gas production wells. It is essential to predict the behavior of hydraulic fractures accurately based on understanding the fundamental mechanism(s). The prevailing approach for hydraulic fracture modeling continues to rely on computational methods based on Linear Elastic Fracture Mechanics (LEFM). Generally, these methods give reasonable predictions for hard rock hydraulic fracture processes, but still have inherent limitations, especially when fluid injection is performed in soft rock/sand or other non-conventional formations. These methods typically give very conservative predictions on fracture geometry and inaccurate estimation of required fracture pressure. One of the reasons the LEFM-based methods fail to give accurate predictions for these materials is that the fracture process zone ahead of the crack tip and softening effect should not be neglected in ductile rock fracture analysis. A 3D pore pressure cohesive zone model has been developed and applied to predict hydraulic fracturing under fluid injection. The cohesive zone method is a numerical tool developed to model crack initiation and growth in quasi-brittle materials considering the material softening effect. The pore pressure cohesive zone model has been applied to investigate the hydraulic fracture with different rock properties. The hydraulic fracture predictions of a three-layer water injection case have been compared using the pore pressure cohesive zone model with revised parameters, LEFM-based pseudo 3D model, a Perkins-Kern–Nordgren (PKN) model, and an analytical solution. Based on the size of the fracture process zone and its effect on crack extension in ductile rock, the fundamental mechanical difference of LEFM and cohesive fracture mechanics-based methods is discussed. An effective fracture toughness method has been proposed to consider the fracture process zone effect on the ductile rock fracture.     

Thermal infrared anomalies as a precursor of strong earthquakes in the distant future

Satellite thermal infrared images contain valuable earthquake precursor information. Past studies concluded that such information appeared only a few days or dozens of days before an earthquake would occur. In our study, though, we observed that the time intervals between the thermal infrared precursor and an earthquake??s occurrence can be up to 10?years. An infrared image can also synchronously indicate the locations of additional future earthquakes with different epicenters within a region. The shape, area, intensity, and movement of thermal infrared anomaly areas are a combination of all the future strong earthquakes within a region. These distant future earthquakes are generally located near the edges, endpoints, or corners of the main structure, fine structures or periphery structures of a thermal infrared anomaly area and play a role in confining the anomaly area. There have not been any exceptions among the strong earthquakes we analyzed, which have included the 2011 Japan M _w 9 event, the 2010 Yushu M _S 7.1 event, the 2008 Wenchuan M _S 8 event, and many other strong events following the 2004 Sumatra M _S 9 event. Surprisingly, some of the earthquakes can outline an area of elevated temperature observed many months ago. If we can roughly locate these potential epicenters through the analysis of thermal infrared images and combining the analysis with other information, and then dynamically monitor them, it may be easier to observe the precursor of an earthquake and predict its occurrence.     

Correlations between 11B NMR parameters and structural characters in borate and borosilicate minerals investigated by high-resolution MAS NMR and ab initio calculations

Borates consisting of diverse fundamental building blocks (FBB) formed from complex polymerization of planar triangular [Bϕ₃] groups and tetrahedral [Bϕ₄] groups, where ϕ = O and OH, provide an excellent opportunity for investigation of correlations between the NMR parameters and local structures. However, previous studies suggested that the ¹¹B NMR parameters in borates are insensitive to local structural environments other than the B coordination number, in contrast to those documented for ²⁹Si, ²³Na and ²⁷Al in silicates, and no correlation between ¹¹B chemical shifts and the sum of bond valences has been established for borate minerals with hydroxyl groups or molecular water in the structures. In this study, high-resolution NMR spectra have been acquired at the ultra high field of 21 T as well as at 14 T for selected borate and borosilicate minerals, and have been used to extract high-precision NMR parameters by using combined ab initio theoretical calculations and spectral simulations. These new NMR parameters reveal subtle correlations with various structural characters, especially the effects of the ¹¹B chemical shifts from the bridging oxygen atom(s), site symmetry, symmetry of FBB, the sum of bond valences, as well as the next-nearest-neighbor cations and hydrogen bonding. Also, these results provide new insights into the shielding mechanism for ¹¹B in borate and borosilicate minerals. In particular, this study demonstrates that the small variation in ¹¹B chemical shifts can still be used to probe the local structural environments and that the established correlations can be used to investigate the structural details in borates and amorphous materials.     

蒙阴盆地早白垩世火山岩地球化学特征及其岩石成因

蒙阴盆地早白垩世火山岩主要出露于青山群八亩地组和方戈庄组中。火山岩SiO₂含量为53.71%~69.08%,主要为安山质岩石和流纹岩,以钙碱性系列为主(σ平均3.42);富集Rb、Ba等大离子亲石元素和轻稀土元素,相对亏损Nb、Ta、P、Ti等高场强元素和重稀土元素;具有富集的Sr-Nd-Pb同位素组成(⁸⁷Sr/⁸⁶Sr(t)=0.7051~0.7110,ε_Nd(t)=-5.16~-16.4)。根据MgO含量和Mg^﹟值,可将安山质火山岩划分为高镁(Mg^﹟>60)和低镁(Mg^﹟<60)两个系列。高镁安山质岩石的MgO、Cr、Ni及不相容元素的含量明显高于低镁安山质岩石,且具有相对高的⁸⁷Sr/⁸⁶Sr(t)和较低的ε_Nd(t)值,Sr-Nd同位素组成趋向于EMⅡ型富集地幔端元。低镁安山质岩石地球化学特征类似于埃达克岩,其同位素组成介于EMⅠ型富集地幔端元与华北麻粒岩相下地壳之间。流纹岩具有较低的MgO、Cr、Ni含量和明显的负Eu、Sr异常,同位素组成类似于扬子中、上地壳。研究表明,蒙阴盆地高镁安山质岩石由曾遭受俯冲扬子陆壳熔体改造的华北岩石圈地幔部分熔融形成,且岩浆在上升 过程中经历了华北下地壳物质一定程度的混染或混合作用;低镁安山质岩石主要由华北下地壳部分熔融形成;流纹岩为岩石圈伸展减薄背景下仰冲至华北克拉通之上的扬子中、上地壳部分熔融的产物。地质现象显示,郯庐断裂带的伸展活动控制着蒙阴断陷盆地的发育,与蒙阴盆地早白垩世火山岩的成因有着密切的联系,在华北克拉通破坏中可能起到了重要的作用。     

航空地球物理勘探资料微调平处理

航空物探测量中测线间水平往往存在差异,表现为沿测线方向的条带。调平处理旨在减少或消除测线间的水平差,是航空物探资料处理中的关键,对航空物探资料处理和解释具有重要作用。笔者以实际的航磁资料处理为例,详细介绍了航空物探资料微调平处理的原理与实现。微调平处理中首先通过方向滤波从原始资料中提取噪声网格,并按飞行测线提取噪声网格中的数据并分离有用的地质信息,最终将分离后的测线水平误差从原始资料中去除得到调平后资料,以此实现航空物探资料的微调平处理。同时,针对资料处理中遇到的诸如滤波器选取、异常分离阈值确定、最终调平效果检验等实际问题进行讨论,这对理解微调平并应用于实际资料处理均具有意义。     

苏北盆地高邮凹陷联盟庄地区戴南组物源及沉积相研究

综合运用碎屑岩类分析法、重矿物法对苏北盆地高邮凹陷联盟庄地区戴南组的物源方向进行了分析。结果表明,戴南组物源具有不稳定性,早、中期物源均来自柘垛低凸起,物源方向由沿东北方向沉积演变为沿南北方向沉积;晚期物源来自西北部的菱塘桥低凸起。联盟庄地区戴南组沉积物为再旋回沉积物,母岩区构造背景为活动大陆边缘,其源岩主要为花岗岩和中基性火成岩。根据岩心、电测曲线、录井以及分析测试资料,对联盟庄地区戴南组的沉积相平面分布进行了研究,三角洲的展布受河湖作用及物源供应的影响,早、中、晚期分别呈朵状、朵叶状和伸长状。