Effect of freeze–thaw cycles on strength and ductility and microstructure of cement-treated silt with polypropylene fiber

Acta Geotechnica - In this paper, the strength, ductility and microstructure behavior of cement-treated silt with polypropylene fiber was studied by a host of experimental studies. The influence of...     

Evaluation of oil Wells performance ranking in high water cut stage

Computational Geosciences - In order to quantify the performance ranking of oil wells in high water cut reservoir, a quantitative evaluation method of oil wells is established from two perspectives...     

Study on deformation characteristics and mechanism of reactivated ancient landslides induced by engineering excavation and rainfall in Three Gorges Reservoir area

Natural Hazards - From 2015 to 2017, construction for the Dalixi Eco-Industrial Park in Dalixi Village, Xingshan County in the Three Gorges Reservoir area, reactivated a series of ancient...     

岩石膨胀性试验注意事项探讨

从室内试验的角度来探讨几类工程勘察中岩石常用膨胀性试验(自由膨胀率、膨胀力、侧向约束膨胀率、耐崩解)的注意事项,从野外取样、标准样品制取、试验操作、方法选择等方面进行了论述,力求减小试验误差,提高膨胀岩的试验水平,保证试验结果的准确性,并使膨胀岩膨胀性指标的测定方法更臻完善。     

虚拟仿真技术在地质学中的应用

得益于计算机技术、人工智能技术、多媒体技术、传感器技术等的迅速发展,虚拟仿真在科学领域已经得到了广泛的应用并具有巨大的市场需求。在地质学中,国内外高校已经将虚拟仿真技术应用到教学中,使其打破了传统教学的时空限制。但目前虚拟仿真在该领域的应用还存在场景内容欠缺,交互感不足,细节展示不够等问题。为能够进一步拓展虚拟仿真技术在地质学中的应用思路,文章对虚拟仿真技术在多个科学学科中的应用情况进行研究,介绍了面向地学的综合型、国际化的沉浸式虚拟仿真实验室实例。综合型的地学虚拟仿真实验室的建立,将深度融合地学与虚拟仿真技术,为多学科交叉融合、国际化教学等未来的教学发展方向提供更有效的平台。     

Helium-argon isotopic tracing for the Pb-Zn-Ag polymetallic ore deposits in the central-south segment of the Da Hinggan Ling Range

In recent years big strides have been made in the exploration of ores in the central-south segment of the Da Hinggan Ling Range, though some debates still exist on the metallogenesis and sources of ore-forming materials. Pyrite and other sulfides in direct relation to the Pb-Zn-Ag ore deposits were chosen for the He and Ar isotopic analysis of ore-forming fluids, and the first He and Ar isotope data have been obtained from the study region. ^3He/^4He ratios in 14 samples collected from 7 mining districts are 2.17×10^-6-12.52×10^-6, averaging 6.86×10^-6 and their R/Ra ratios are 1.56-9.01 Ra, averaging 4.37 Ra. By projecting the data points onto the ^3He-^4He concentrations diagram, all the points fall near the mantle helium area. The calculated mantle-source helium ratios are within the range of 19.58%-76.96%, with an average of 49.52%. Argon isotopic characteristics are close to those of mantle source, indicating that the ore-forming material was transport upwards via the multi-stage evolution of mantle plume and concentrated as ores in the favorable loci of mantle branch structures.     

河北省白洋淀洼地环境地球化学物源判断

河北省白洋淀洼地是一个大型天然平原洼地,在洼地的深、浅层土壤中均发现了以Cu、Pb、Zn、Cd为主的多变量地球化学异常。运用地球化学特征法、参考元素法及多元统计法,对深、浅层土壤Cu、Pb、Zn、Cd异常的性质和成因进行了判别。结果表明,深层土壤异常与特定的地球化学沉积环境有关,以自然地质作用成因为主,而浅层土壤异常具有典型的二元叠加特征,以人为源的输入为主。     

Jurassic Hornblende Gabbros in Dongga, Eastern Gangdese, Tibet: Partial Melting of Mantle Wedge and Implications for Crustal Growth

The Gangdese batholith, more than 2500 km in length, is composed mainly of JurassicMiocene igneous rocks. This batholith is one of the most important constituents of the Tibetan orogenesis and provides an ideal place for study of Neo-Tethyan ocean geodynamic evolution and plateau uplift. Recent studies on the Gangdese Jurassic felsic magmatism highlight its juvenile source. However, important aspects concerning the genesis of the juvenile magmatism and related deep geodynamic evolution are still unclear. Here, we report detailed petrological, geochronological, geochemical, whole-rock Sr-Nd isotopic, and in situ Sr-Hf isotopic data for a recently identified hornblende gabbro in the Dongga area, southern Lhasa sub-block. This hornblende gabbro is dominated by hornblende and plagioclase, dated at Early Jurassic(ca. 180–190 Ma), and characterized by a narrow compositional range in SiO_2(49.38wt%–52.27wt%), MgO(4.08wt%–7.00wt%), FeO(10.43wt%–11.77wt%), Na_2O(2.58wt%–3.51wt%), and K_2O(0.48wt%–1.53wt%). It has depleted isotopic signatures, with whole-rock(~(87)Sr/~(86)Sr)i ratios of 0.7033–0.7043, ε_(Nd)(t) values of +4.90 to +6.99, in situ plagioclase(~(87)Sr/~(86)Sr)i ratios of 0.7034–0.7042, and zircon ε_(Hf)(t) of +12.2 to +16.8. Our results integrated with published data suggest a model of Gangdese juvenile crustal growth by a subduction-related water-enriched mantle wedge. The hydrous partial melting of the lithosphere mantle was triggered by the dehydration of a Neo-Tethyan oceanic slab. This mafic magmatism emplaced in the middle-lower crust of intraoceanic arcs or active continental margins, leading to Jurassic juvenile crustal growth in southern Tibet.     

Monazite and xenotime U–Th–Pb geochronology by ion microprobe: dating highly fractionated granites at Xihuashan tungsten mine, SE China

Zircon, monazite, and xenotime have proven to be valuable chronometers for various geological processes due to their commonly high-U–Th and low common Pb contents. However, zircons that have crystallized in highly fractionated granites often have such high-U contents that radiation damage can lead to scattered U–Pb ages when measured with secondary ion mass spectrometry (SIMS). In this study, monazite and xenotime were separated from a number of highly fractionated granites at the Xihuashan tungsten mine, Southeast China, for alternative dating methods by SIMS. For monazite analysis, obvious excess ²⁰⁴Pb signal (mainly from interference of ²³²Th¹⁴⁴Nd¹⁶O₂ ⁺⁺) was observed in high-Th (>2 wt%) monazite, which hinders ²⁰⁴Pb-based common Pb corrections. A ²⁰⁷Pb-based common Pb correction method was used instead. By employing power law relationships between Pb⁺/U⁺ versus UO₂ ⁺/U⁺, Pb⁺/Th⁺ versus ThO₂ ⁺/Th⁺ and suitable exponentials, monazites with ThO₂ contents in the range of ~3–19 % do not exhibit this matrix effect. Independent SIMS U–Pb ages and Th–Pb ages of three phases of Xihuashan granite samples were consistent with each other and yielded dates of 158.7 ± 0.7, 158.0 ± 0.7, and 156.9 ± 0.7 Ma, respectively. Xenotime does show marked matrix effects due to variations of U, Th, and Y [or total rare earth element (REE), referred as ΣREE hereafter] contents. Suitable correction factors require end-member standards with extremely high or low U, Th, and Y (or ΣREE) contents. No excess ²⁰⁴Pb was observed, indicating that the ²⁰⁴Pb-based common Pb correction method is feasible. Independent ²⁰⁷Pb/²⁰⁶Pb ages can be obtained, although multi-collector mode is necessary to improve precision. The main difficulties with dating xenotime are when high-Th (U) mineral inclusions are ablated. We can identify when this occurs, however, by comparing the measured UO₂ ⁺/U⁺ and ThO₂ ⁺/Th⁺ with those in xenotime standards. Three xenotime samples from the first phase of Xihuashan granite yielded a weighted mean ²⁰⁷Pb/²⁰⁶Pb date of 159.5 ± 4.4 Ma (MSWD = 1.0) and a ²⁰⁶Pb/²³⁸U date of 159.4 ± 0.9 Ma (MSWD = 1.6), which are consistent with monazite U–Pb and Th–Pb ages from the same granites. This study demonstrates that monazite and xenotime are better SIMS chronometers for highly fractionated granites than zircon, which can yield doubtful ages due to high-U contents.     

利用蚂蚁追踪技术精细解释矿井地质构造

蚂蚁追踪技术是目前三维地震资料解释中用于地质构造解释的方法之一.该技术是在地震资料进行预处理、及利用方差体技术、相干体技术等多种地震属性技术检测地震反射不连续性时,以蚁群优化算法为指导,实现断裂的自动解释.应用实例表明:利用蚂蚁追踪技术获得的属性体切片可以更直观的显示断裂痕迹,有效的指导断裂人工解释及三维断片自动提取、编辑等工作.