The ore prospecting prediction model for the Huili copper orefield in Sichuan Province, China

The prediction theory and methodology of ore prospecting were developed from an in-depth study of 129 typical deposits in China. It has been verified to be an effective method that is particularly suitable for the initial ore prospecting. In this method, the internal and external factors of metallogenesis are combined together to construct a geological model of prospecting prediction, which consists of metallogenic geological body, metallogenic structure, metallogenic structural plane and metallogenic characteristics. The Huili area is located in the western margin of the Yangtze Plate, where the regional metallogenic geological conditions are superior, and a series of unique iron-copper deposits were formed. In recent years, great breakthroughs and progress have been made in the deep and peripheral areas of the Huili copper orefield. Herein, we take the Huili copper orefield as a typical example to illustrate the specific application of this method in deep ore prospecting of hydrothermal deposits. The metallogenic geological body is the ore-hosting volcanic rocks (albitite in the Hekou Group), and the main metallogenic structure and structural planes are interfaces between basic (intermediate) volcanic rocks and sedimentary rocks and the possible volcanic vent. Combined with the summary of metallogenic characteristics, we constructed a geological model for ore prospecting in the Huili copper orefield.

3D Geological Implicit Modeling Method of Regular Voxel Splitting Based on Layered Interpolation Data

In view of the problems in traditional geological modeling methods, such as the insufficient utilization of geological survey data, the inaccurate expression of a stratigraphic model, and the large amount of model data, a 3D geological model cannot be smoothly loaded and rendered on the web end. In this paper, a 3D geological implicit modeling method of regular voxel splitting based on hierarchical interpolation data is proposed. This method first uses the boreholes and geological section data from a geological survey for data conversion and fusion, compares the applicability of different interpolation algorithms through cross-validation research, and uses the best fitting algorithm to interpolate and encrypt discrete points in the formation. Then, it constructs the regular voxels, designs five different regular voxel split types, and divides the voxels. In addition, the data structure design of the voxel split model is implemented, and the irregular voxel metadata structure is analyzed and displayed through Three.js. Using this method, based on the survey data of an area in Zhengzhou, the global workflow from data processing to model construction and visualization is demonstrated. The experimental results show that the model can integrate multisource hierarchical interpolation data; express different stratum structures accurately and smoothly, and can realize the fast rendering, spatial query and analysis of the internal information of a geological body in a browser.

Hydro-Damage Properties of Red-Bed Mudstone Failures Induced by Nonlinear Seepage and Diffusion Effect

Nonlinear catastrophes caused by geological fluids are a fundamental issue in rock mechanics and the geoengineering hazard field. For the consideration of hydrodynamic force on red-bed mudstone softening damage, X-ray visualization test on the fissure flow in mudstone block failure under hydrodynamic force was performed in this study based on block scale and the physical phenomena of fissure seepage and nonlinear diffusion were further explored. A new method for evaluating the hydro-damage degrees of rocks using an X-ray image analysis was proposed, and the quantitative relation of diffusion coefficients of hydro-damage and seepage was established. The research results revealed that the hydrodynamic force promoted the fluid-filled fissure behavior in mudstone specimen failure. Also, the seepage and diffusion phenomena of fluid in rocks during failures were indicated using X-ray imaging. A dual mechanical behavior was presented in the nonlinear seepage and abnormal diffusion of a red mudstone geological body under hydrodynamic conditions. The damaged degree of mudstone was aggravated by the effect of hydrodynamic force, and the initial seepage–diffusion coefficient with respect to lower hydro-damage was larger than the final seepage–diffusion coefficient with respect to higher hydro-damage of rocks with a decreasing nonlinear trend.

Mechanism of Coal Bump among Mine Group under the Control of Large Geological Body: A Case Study of Yima Mining Area, China

Coal bump often occurs in coal mining among many working faces in mine group under the control of large geological bodies. In order to study the coal bump mechanism between adjacent working faces under the conditions of large fault and huge thick overburden conglomerate, this paper regards Yima mining area as a practical engineering background and theoretically analyzes the mechanical behavior of overlying rock in the spatial structure. Then, the deep-ground and whole-space measurement is carried out in the 13230 working face of Gengcun mine and 21121 working face of Qianqiu mine. The results show that the basic structural unit in Yima mining area is composed of two goafs, middle coal pillar, and overlying conglomerate. Under the condition of nonsynchronous mining in adjacent working faces, there is a comovement effect similar to lever’s “prying” phenomenon in thick conglomerate beam—the conglomerate strata above larger goaf side induce an overall uplift movement of the corresponding strata above smaller goaf side, and uplift length of the conglomerate strata is related to the mining length, coal pillar width, caving angle, and coal-conglomerate distance. The results of surface subsidence, microseism, and stress in the two working faces verify the conglomerate’s phenomenon of comovement effect and disturbance range and further explain the role of active movement of F16 fault and overall causes of huge thick conglomerate on the coal bump. The vertical stress of the 13230 face is relatively low at the beginning, and high horizontal stress by fault activation causes typical bump accident with the horizontal sliding of coal body. With the increasing development of 13230 face, the intensity and frequency of coal bump in horizontal direction decrease obviously, but with high proportion in vertical direction. The results provide a theoretical basis for the study on the mechanism of coal bump between two adjacent working faces under the conditions of huge thick conglomerate and large thrust fault.

GEOLOGICAL INFORMATION OF MAGNETIC PROPERTIES OF GRANITOIDS OF THE PRECEMBRIAN BASEMENT OF UKRAINIAN SHIELD (ON THE EXAMPLE OF THE MELNIKOVTSY PLOT)

In Ukraine, there are all possibilities for the development of geophysical methods for solving the problems of mapping the Precambrian foundation, as there is a well-exposed Ukrainian Shield (US). The article shows the possibilities of the magnetic scanning method for geological mapping, on the example of a section composed of granitoids with xenoliths of crystalline shales. The magnetic field and magnetic susceptibility on exposures are «scanned» in detail. Two positive anomalies of the magnetic field with a similar fine internal structure have been identified. The results of the study showed that granitoids have low magnetic properties that do not allow the formation of positive anomalies of the magnetic field. It is assumed that the source of «toothed» positive anomalies of the magnetic field in the studied section of the US can be two parts of one layered geological body — with a rhythmic internal structure composed of crystalline shales. It is possible that the body was awakened by local tectonic processes and torn into parts that are significantly displaced, and even lie almost parallel in the study area.

Insights into the petrogenesis and petrophysics of vein magmatism in the Lamas de Olo region, northern Portugal

<p>The onset of the final stages of the Variscan orogeny in the Central Iberian Zone (CIZ) is marked by the emplacement of several late to post-tectonic granite melts. The following transition into an extensional regime is associated with subvolcanic magmatism, commonly represented by veins and masses of rhyolitic porphyries, dolerites, and lamprophyres. In Portugal and Spain, these hypabyssal lithologies are fairly abundant.</p><p>The Lamas de Olo region of northern Portugal is located about 100 km to the ENE of Porto. Here, the most significant geological body is the composite, post-tectonic Lamas de Olo pluton. Several fracture systems, whose average trends are NNW-SSE, NNE-SSW, and WSW-ENE, cut through this pluton. The composing facies are known as the Lamas de Olo (LO), Alto dos Cabeços (AC), and Barragem (BA) granites. To the east of the pluton, there are two veins: a microgranite and a lamprophyre. While the microgranite is E-W trending, the lamprophyre is N53°E trending.</p><p>The felsic vein is rich in quartz and K-feldspar, which are frequently intergrown in granophyric texture, while muscovite, apatite, biotite, and ilmenite are accessories. The feldspars are intensely kaolinized and muscovitized, and biotite is mostly altered in chlorite and brookite/anatase. Compositionally, the microgranite is identical to the BA facies. It is subalkaline, highly felsic peraluminous, and associated with post-orogenic to transitional settings.</p><p>Biotite, K-feldspar, plagioclase, pyroxene, and amphibole are the main minerals composing the lamprophyre. Quartz, hematite, goethite, apatite, monazite, zircon, and magnetite are accessories. Pyroxene uralitization, amphibole biotitization, and biotite chloritization evidence the altered state of this vein. Geochemically, the pluton and lamprophyre have nothing in common. This lithology is metaluminous to weakly peraluminous, shoshonitic, alkaline, and associated with within-plate and post-collisional uplift settings. Zircon SHRIMP U-Pb analyses yield a concordia age of 295 ± 2 Ma (MSWD = 2.1) and the Nd isotopic signature is εNd = -0.05.</p><p>Considering the geochemistry, the microgranite is more evolved than the LO and AC granites. Most likely, it derived from a plagioclase-rich, crustal source, which was uncontaminated by mantle or young crustal materials. The microgranite melt was presumably derived from the same source that generated the BA granite, and its emplacement was controlled by WSW-ENE trending fractures. The mineral assemblage is mostly diamagnetic, and the post-magmatic alterations were mainly triggered by meteoric fluids, thus generating an ambiguous magnetic fabric. The microgranite is also associated with a subhorizontal magma flow and shallow roots. On the other hand, the lamprophyre was presumably derived from the lithospheric mantle and strongly contaminated by lower crustal materials. Geochemically, the lamprophyre is unrelated to the pluton, but structurally the NNE-SSW trending fractures probably influenced its emplacement. The petrophysical results point out a ferromagnetic behavior and influence of hydrothermal fluids. Based on our results, the lamprophyre was seemingly generated and emplaced after the microgranite.</p><p>This work was supported by the Portuguese Foundation for Science and Technology (FCT), through the project reference UIDB/04683/2020 and ICT (Institute of Earth Sciences). The main author is also financially supported by FCT through an individual Ph.D. grant (reference SFRH/BD/138818/2018).</p>