Mineralization and Structural Controls of the AB-Bid Carbonate-Hosted Pb-Zn (±Cu) Deposit, Tabas-Posht e Badam Metallogenic Belt, Iran

The Ab-Bid deposit, located in the Tabas-Posht e Badam metallogenic belt (TPMB) in Central Iran, is the largest Pb-Zn (±Cu) deposit in the Behadad-Kuhbanan mining district. Sulfide mineralization in the Ab-Bid deposit formed in Middle Triassic carbonate rocks and contains galena and sphalerite with minor pyrite, chalcopyrite, chalcocite, and barite. Silicification and dolomitization are the main wall-rock alteration styles. Structural and textural observations indicate that the mineralization occurs as fault fills with coarse-textured, brecciated, and replacement sulfides deposited in a bookshelf structure. The Ab-Bid ore minerals precipitated from high temperature (≈180–200 °C) basinal brines within the dolomitized and silicified carbonates. The sulfur isotope values of ore sulfides suggest a predominant thermochemical sulfate reduction (TSR) process, and the sulfur source was probably Triassic-Jurassic seawater sulfate. Given the current evidence, mineralization at Ab-Bid resulted from focusing of heated, over-pressurized brines of modified basinal origin into an active fault system. The association of the sulfide mineralization with intensely altered wall rock represents a typical example of such features in the Mississippi Valley-type (MVT) metallogenic domain of the TPMB. According to the structural data, the critical ore control is a bookshelf structure having mineralized dextral strike-slip faults in the northern part of the Ab-Bid reverse fault, which seems to be part of a sinistral brittle shear zone. Structural relationships also indicate that the strata-bound, fault-controlled Ab-Bid deposit was formed after the Middle Jurassic, and its formation may be related to compressive and deformation stages of the Mid-Cimmerian in the Middle Jurassic to Laramide orogenic cycle in the Late Cretaceous-Tertiary.

Performance Research of Materials and Engineering Application of Overburden Strata Separation-Zone Grouting Technology

To solve the ground subsidence problem associated with thick coal seam mining under the railway in the Tangshan Mine, the technology of overburden strata separation-zone grouting (OSSG) was proposed. Based on the analysis of the full height overlying strata structure in the range of the six working face areas of the second mining district, the spatial distribution characteristics of the separation zone within the overlying strata are obtained after fully mining the six working faces. Then, emphasis was placed on the selection ratio of grouting materials and the hydrodynamic properties of different grout types, and grouting grout with a high concentration, slow precipitation rate, and good stability was obtained by taking fly ash and local clay as aggregates. The designed grout concentration was approximately 40%; the bulk density was approximately 1.20; and the clay content in the aggregates was approximately 40–50%. The separation-zone grouting plan was designed for the six working faces, and continuous grouting technology with the characteristics of multiple separation zones within the full-height section with a large flow and a high concentration was proposed to form a complete grouting system and reasonable grouting process. After engineering verification, the technology has an ash injection ratio of 24.2%, a grouting ratio of 100.3%, and a reduction in the ground subsidence ratio of 51.5%, effectively reducing mining damage to the ground surface and ensuring the safe operation of ground surface railways. Simultaneously, this advancement improves the resource recovery rate of coal mines and provides greater benefits for mining enterprises.

Mechanism of Coal Burst and Prevention Practice in Deep Asymmetric Isolated Coal Pillar: A Case Study from YaoQiao Coal Mine

Coal pillar bursts continue to be a severe dynamic hazard. Understanding its mechanism is of paramount importance and crucial in preventing and controlling its occurrence. The extreme roadway deformations from the asymmetric isolated coal pillars in the central mining district of YaoQiao Coal Mine have responded with frequent intense tremors, with risky isolated coal pillar bursts. The theoretical analysis, numerical simulation, and field measurements were done to research the impact of spatial overburden structure and stress distribution characteristics on the isolated coal pillar area, aiming to reveal the mechanism of coal pillar burst leading to the practice of prevention and control in the asymmetric isolated coal pillar area. The study shows that the overburden structure of the asymmetric is an asymmetric “T” structure in the strike-profile, and the stress in the coal pillar is mostly asymmetric “saddle-shaped” distribution, with the peak stress in the east side of the coal pillar, and the coal pillar is a “high stress serrated isolated coal pillar.” Numerical simulation results showed that the support pressure in the isolated coal pillar area on the strike profile was asymmetrically “saddle-shaped” distribution. The peak vertical stress in the coal pillar area continued to rise and gradually shifted to the mining district's deep part. As a result, the response of the roadway sides to the dynamic load disturbance was more pronounced. They developed a coal burst prevention and control program of deep-hole blasting in the roof of asymmetrical isolated coal pillar roof and unloading pressure from coal seam borehole. Monitored data confirmed that the stress concentration was influential in the roadway’s surrounding rock in the asymmetric isolated coal pillar area, circumventing coal pillar burst accidents. The research outcomes reference the prevention and control of coal bursts at isolated working faces of coal pillars under similar conditions.

Estimation of the Pb Content in a Tailings Dam Using a Linear Regression Model Based on the Chargeability and Resistivity Values of the Wastes (La Carolina Mining District, Spain)

The study area is located in the old mining district of Linares–La Carolina (southeastern Spain), the largest global producer of lead between 1875 and 1920. The selected environmental liability is the dam of the Federico mine and the waste that was generated during the flotation process. Geophysical techniques were applied along the slope of the dam, specifically ERT and IP. In total, 26 waste samples were taken along the entire slope of the dam, in which a high metal(oid) content was identified, sometimes much higher than the reference levels established by European and regional legislation for contaminated soils. The concentrations of Pb, As, and Ba stood out, with mean values of 4863 mg.kg−1, 89 mg.kg−1, and 794 mg.kg−1, respectively. Univariate and multivariate statistical analysis could characterize the distribution of the contents of the different elements along the slope, defining the associations and dispersion patterns of the metal(oid)s in the interior structure of the mine wastes. With the results of the Pb content (the most abundant metal in mineral paragenesis), a mathematical model was obtained by linear regression that related the variability of this cation with the variation in electrical resistivity and chargeability obtained by geophysical techniques.