Mathematical model of a Hot Dry Rock system   总被引：1，自引：0，他引：1  

Norbert Heuer  Tassilo Küpper  Dirk Windelberg 《Geophysical Journal International》1991,105(3):659-664

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S-A多重分形法在地球化学异常 圈定中的对比应用—以甘肃文康地区为例     

牛旭刚 《地质与勘探》2023,59(4):817-827

通过对甘肃省陇南文康地区的地质背景分析,采用区域1:5万水系沉积物测量的17种常量元素含量数据,分别运用传统统计学方法、S-A（能谱密度-累计面积）多重分形滤波法,确定成矿元素（以Au为例）异常下限值,圈定化探异常。结果表明,与传统方法相比,S-A多重分形法所圈定的异常面积小、数量多,传统统计法圈定的面积较大;两种方法圈定的异常展布方向基本一致,与研究区内已知的矿点吻合度高。本次研究认为S-A多重分形法所圈定的异常基本位于传统方法所圈定异常的内带之中,重点突出,与矿床空间位置对应关系较好,便于野外开展工作。同时在传统异常周边提取了部分低背景区的弱异常,这些弱异常可作为下一步找矿工作的新靶区。  相似文献   

The added value of joint PP–PS inversion for reservoir characterization: A case study using Jubarte PRM seismic data (offshore Brazil)     

Andrea Damasceno  Ali Tura  James Simmons 《Geophysical Prospecting》2022,70(1):121-134

The added value of the joint pre-stack inversion of PP (incident P-wave and reflected P-wave) and PS (incident P-wave and reflected S-wave) seismic data for the time-lapse application is shown. We focus on the application of this technique to the time-lapse (four-dimensional) multicomponent Jubarte field permanent reservoir monitoring seismic data. The joint inversion results are less sensitive to noise in the input data and show a better match with the rock physics models calibrated for the field. Further, joint inversion improves S-impedance estimates and provides a more robust quantitative interpretation, allowing enhanced differentiation between pore pressure and fluid saturation changes, which will be extremely useful for reservoir management. Small changes in reservoir properties are expected in the short time between the time-lapse seismic acquisitions used in the Jubarte project (only 1 year apart). The attempt to recover subtle fourth-dimensional effects via elastic inversion is recurrent in reservoir characterization projects, either due to the small sensitivity of the reservoirs to fluid and pressure changes or the short interval between the acquisitions. Therefore, looking for methodologies that minimize the uncertainty of fourth-dimensional inversion outputs is of fundamental importance. Here, we also show the differences between PP only and joint PP–PS inversion workflows and parameterizations that can be applied in other projects. We show the impact of using multicomponent data as input for elastic seismic inversions in the analysis of the time-lapse differences of the elastic properties. The larger investment in the acquisition and processing of multicomponent seismic data is shown to be justified by the improved results from the fourth-dimensional joint inversion.  相似文献   

岩石内应力的X射线-中子散射测量方法     

陈卫昌  李守定  李晓  王思敬  何伦华  刘世民 《工程地质学报》2022,30(1):223-233

岩石内应力的储存和释放对深地资源和能源开发具有重要约束。矿物晶格间距的动态变化是揭示岩石内应力演化的重要指示。X射线衍射法是当前获取矿物晶体结构的主要手段,可以准确测定矿物的特征衍射峰。但是,对于具有复杂结构和矿物组成的岩石,X射线在穿透过程中携带的统计信息,难以反映矿物晶格间距的细节特征。中子射线的能量高、穿透深度大,且与原子核反应,因而能更准确地刻画矿物元素位置和结构细节,但中子的波长较长、校准困难,结果具有不确定性,导致中子射线在岩石内应力研究中未能发挥应有作用。在分析X射线、中子技术优势和固有局限的基础上,提出了岩石内应力的X射线-中子衍射测量方法,重点剖析了该方法的基本原理,提出了该方法的关键技术与研究前景。得出了如下结论:利用X射线在确定岩石矿物晶格参数的优势,结合加热处理等技术,可实现岩石矿物无应力条件下晶格间距的标定; 采用中子衍射技术可精确测量岩石矿物的衍射偏移峰,实现岩石内应力深度轮廓的精准刻画; 结合X射线与中子的优势,可实现岩石内应力绝对值的精确测量。提出的技术手段有利于揭示岩石内应力的微观储存和释放过程,以及长期存留的物质条件和物理力学机制,并有望为岩石矿物组成和微观结构研究提供一种新的技术方案。  相似文献   

岩体多尺度异质性及其力学行为     

兰恒星  包含  孙巍锋  刘世杰 《工程地质学报》2022,30(1):37-52

异质性是岩体的重要属性之一,从岩体的物质组成到结构特征,再到微宏观力学行为表现,异质性现象普遍存在。本文在梳理已有研究成果的基础上,从岩体的细微观异质性、结构面异质性和宏观异质性3个不同的尺度,对异质性的产生原因、表现特征、力学效应和时空演化规律等进行阐述,并介绍了相关研究方法以及异质性在不同尺度上的差异表现。岩体异质性的研究,是岩体工程地质力学理论体系的延伸,而多尺度的研究方法也成为全面揭示岩体变形破坏机制的一种有效手段。  相似文献   

Rapid assessment of beta dose variation inside cobbles,and implications for rock luminescence dating     

《Quaternary Geochronology》2022

Variation in beta dose rate within rocks may impact the results of rock surface luminescence dating, for both the burial age of cobbles and exposure age of rock surfaces. Current methods of rock surface luminescence dating assume that radionuclides are homogeneously distributed inside rocks. In this study, two rapid methods based on beta counting and on a portable XRF instrument were developed to measure the radioactivity of rock slices. These methods were applied to rock slices from four glaciofluvial granite cobbles that had previously been used for equivalent dose determination to test whether beta dose variation could be observed. Results from beta counting and K content from XRF show similar patterns and both vary along the depth profiles, but the magnitude of this variability is very different amongst the four cobbles. In rocks where the dose rate is highly variable, bleaching may not be the only source of variation of L_n/T_n or equivalent dose (D_e) along the luminescence-depth profile of cobbles, and it may be necessary to measure the beta dose rate for every single slice to determine whether multiple bleaching events are recorded or variations in D_e are due to dose rate heterogeneity.  相似文献   

Isolating quartz-dominated OSL signal of rock slice by using pulsed stimulation: Implications for dating burial age of cobbles     

《Quaternary Geochronology》2022

Although the OSL signal sourced from quartz is expected to be more stable and bleached more rapidly than the IRSL signal sourced from feldspar in a general sense, the former is much less investigated than the latter for rock surface related luminescence dating. It is mainly due to the difficulty in isolating quartz-dominated OSL signals from rock slices, and the low sensitivity and non-fast component dominated OSL signals for quartz in most of rocks. In merit of the sub-conduction band transition of trapped electrons of feldspar under both green light stimulation and IR stimulation at elevated temperature (Jain and Ankjӕrgaard, 2011), it is expected that the contribution of feldspars to the green light stimulated luminescence could be substantially reduced by a prior IR stimulation at elevated temperature. Meanwhile, more fast-component dominated quartz OSL signal (if there is any) could be obtained by green light stimulation (Bailey et al., 2011). Therefore, in this study, we investigated the feasibility of using the post-IR pulsed green stimulation, which is performed at 25 °C (PGLSL₂₅) following two IR stimulations (IR₅₀IR₂₂₅), to isolate the quartz-dominated OSL signals from rock slices of granite cobbles for burial dating. The decay characteristics of stimulation curve, characteristic saturation dose and thermal stability of the pIR₅₀IR₂₂₅ PGLSL₂₅ signal suggest that this signal is quartz-dominated, but still not fast-component dominated. We tentatively validated the equivalent dose (D_e) measurement protocol by dose recovery experiment. The luminescence-depth profiles show that the bleaching depths of pIR₅₀IR₂₂₅ PGLSL₂₅ signals are slightly smaller than or close to that of the IR₅₀ signals, while they are much shallower for the pIR₅₀IR₂₂₅ signals. The pIR₅₀IR₂₂₅ PGLSL₂₅ procedure enables multiple D_e values determined from luminescence signals, with different bleachabilities and stabilities, from both feldspars and quartz in one measurement, which is of potential for buried age dating of cobbles.  相似文献   

Dating of megaflood deposits in the Russian Altai using rock surface luminescence     

《Quaternary Geochronology》2022

Catastrophic drainage of ice-dammed lakes in the Altai Mountains has been inferred from geomorphological evidence in the Katun Valley (Russia), and is presumed to have occurred during the Pleistocene. The sedimentary features have been difficult to date directly, due to the absence of organic carbon, and the improbability that luminescence signals in sand grains would be reset during transport. However, the development of rock-surface luminescence dating provides a new opportunity to date the features: clasts have a different transport history to sand grains, and their luminescence depth profiles can be inspected for evidence of bleaching before burial. Here we investigate two sites in the Altai Mountains, and use rock-surface luminescence burial dating to constrain the age of the megaflood deposits. In the Katun Valley, we sampled granite cobbles from a frozen sediment clast emplaced as a dropstone within a massive megaflood gravel terrace. Burial ages for the clasts range from 16.7 to 21.4 ka, with a mean age of 19.8 ± 1.5 ka. This represents the depositional age of the fluvial sediments that preceded the lake outburst flood, (and hence places a maximum age on the catastrophic flood). Clasts sampled from mega-ripples in the Kurai Basin are shown to have a mid-to-late Holocene burial age, which is not consistent with the possible origin of these features during a catastrophic drainage of a glacier-dammed lake. Instead, the burial age of the Kurai Basin sediments may reflect local-scale periglacial or seismic processes along the Kurai Fault Zone.  相似文献   

岩脉多次侵入条件下斜坡变形破坏模式及稳定性分析     

张玉明  张明  胡新丽  谭福林  祝廷尉  徐聪 《工程地质学报》2015,23(2):227-232

岩质斜坡受到花岗岩脉的多次侵入,坡体结构和岩体结构均有较大的改变,因此斜坡的变形破坏模式和稳定性均有可能发生变化。本文以雅砻江中游楞古水电站坝址区嘎夏帕斜坡为例,对多次花岗岩脉侵入条件下斜坡的变形破坏模式和稳定性进行分析。嘎夏帕斜坡原本为陡倾中薄层砂岩组成的逆向坡,岩体完整性较好,稳定性较高; 由于受到花岗岩脉的多次侵入,坡体变成砂岩和岩脉互层的结构,在岩脉挤压作用下,大部分岩体呈碎裂状,完整性差,坡体的变形模式由弯曲-倾倒式变为挡墙溃决式。中部完整性较好的砂岩成为挡墙,和前部岩脉一起阻止后部大方量碎裂状岩体下滑,但是随着前部脉体的失稳破坏,斜坡有可能发生挡墙溃决式整体滑坡。并通过数值模拟软件3DEC进行了验证,计算结果与定性分析一致。本文的结论可以为此类斜坡的稳定性分析和防治提供理论支持,具有一定的参考价值和实际意义。  相似文献   

青海祁漫塔格虎头崖多金属矿区岩体热年代学研究   总被引：2，自引：0，他引：2  

瞿泓滢  丰成友  裴荣富  何书跃  李大新  刘建楠  王辉  周建厚 《地质学报》2015,89(3):498-509

虎头崖铜铅锌多金属矿床是青海祁漫塔格地区典型的与印支期岩浆侵入活动有关的接触交代矿床,矿区内出露多个不同时代的含碳酸盐地层,金属成矿元素组合复杂,中酸性侵入岩产状多变、岩性多样,成矿岩体及其成矿能力的判别一直制约着该矿区及区域的找矿勘查工作。本文基于详细的野外地质调查,开展了岩体热年代学和岩石地球化学研究。利用LA-MC-ICP-MS锆石U-Pb法,获得二长花岗岩体的年龄为230.3±3.7 Ma(n=13,MSWD=1.4);利用40 Ar-39 Ar法,获得二长花岗岩中黑云母和斜长石矿物的坪年龄分别为229.6±2.3 Ma和219.3±1.8Ma,厘定成岩时代为印支期。对二长花岗岩中不同矿物的岩体冷速率计算结果表明,虎头崖矿区二长花岗岩冷速率相对较快,其热效应较大,具有较大的成矿潜力。二长花岗岩为高钾钙碱性系列岩石,源于古老地壳物质的深熔或重熔,并可能有幔源物质的加入。  相似文献