Ore-bearing Rocks Research Articles

ТЕОРЕТИКО-МЕТОДОЛОГІЧНІ І КРИТЕРІАЛЬНО-ПОНЯТІЙНІ ПІДҐРУНТЯ ПРОГНОЗНО-МЕТАЛОГЕНІЧНИХ ДОСЛІДЖЕНЬ

Theoretical-methodological and criterion-conceptual basis of forecasting-metallogenic researches, and also the maintenance and methods of drawing up of metallogenic and forecasting maps as the most important practical reflection of laws of space-time distribution of solid minerals deposits have been analysed. Deposits are formed due to certain combinations of geotectonic, geochemical, petrological and actually ore-forming processes. Knowledge of informative interpenetration and logical interaction of these processes determines the rationality, reliability and success of predictive research of potentially ore-bearing rock complexes. Metallogenic features, and hence the signs (criteria) of the manifestation of mineralization are always different at different stages of the geological history of the Earth's crust. Therefore, forecasting-metallogenic works should be performed taking into account only real, objectively available geological-geochemical and geophysical parameters of mineralization, which can be traced, documented, mapped and fully or as much as possible objectified in the process of compiling metallogenic and forecast maps. The metallogenic map shows the patterns of formation and localization of useful minerals, metallogenic zoning of the country or individual regions, the classification of metallogenic objects. In the case of such maps, two approaches are used: paragenetic (localization of deposits is determined on the basis of generalization of information about the confinement of deposits to certain geological formations and tectonic structures) and genetic (applied to sedimentary minerals that are part of the stratigraphic section and reflect sedimentation processes). Today, forecast maps are preferred because, unlike metallogenic ones, they reflect conclusions about possible, but not yet discovered ore-bearing areas and deposits, their long-term assessment, often with a description of their species and sequence. In fact, the forecast map is not one map, but a set of maps with a corresponding explanatory note.

Geochemical Compositions and Detrital Minerals of Stream Sediments around the Zijinshan Copper-Gold Orefield and Their Implications

Regional geochemical anomalies in stream sediments often have close spatial relationships with metallogenic provinces or ore districts, but the relationships between them have not been examined in depth. In this study, stream sediments were collected around the Zijinshan Copper-Gold Orefield, Fujian Province, China. Element geochemistry, U–Pb geochronology and Hf isotope compositions of detrital zircons, and electron microprobe and LA-ICP-MS analyses of iron oxides were conducted. The aims of this study were to investigate the relationship between the provenance of the stream sediments and ore-bearing magmatic rocks in the Zijinshan Copper-Gold Orefield, and to explore the enrichment mechanism of the ore-forming elements in stream sediments. The results show that the ore-forming elements and their associated elements are most significantly enriched in stream sediments near the orefield. U–Pb ages and Hf isotopic compositions of detrital zircons in the sediments closest to the orefield carry information on the ore- bearing magmatic rocks in the orefield. However, as the stream sediments are relatively far from the orefield, the degree of enrichment of ore-forming elements and the detrital zircon U–Pb age signals of the ore-bearing magmatic rocks in the orefield rapidly weaken. This weakening of the geochemical signals may have been affected by many factors, such as lithological resistance to weathering, vegetation coverage, micro-topographic conditions, etc. In-situ elements analysis of iron oxides and elemental correlation analysis of stream sediments indicate iron oxides and clay minerals are the main carrier minerals for the migration of ore-forming elements.

Quantification of the Spectral Variability of Ore-Bearing Granodiorite under Supervised and Semisupervised Conditions: An Upscaling Approach

Reflectance spectroscopy is a nondestructive, rapid, and easy-to-use technique which can be used to assess the composition of rocks qualitatively or quantitatively. Although it is a powerful tool, it has its limitations especially when it comes to measurements of rocks with a phaneritic texture. The external variability is reflected only in spectroscopy and not in the chemical-mineralogical measurements that are performed on crushed rock in certified laboratories. Hence, the spectral variability of the surface of an uncrushed rock will, in most cases, be higher than the internal chemical-mineralogical variability, which may impair statistical models built on field measurements. For this reason, studying ore-bearing rocks and evaluating their spectral variability in different scales is an important procedure to better understand the factors that may influence the qualitative and quantitative analysis of the rocks. The objectives are to quantify the spectral variability of three types of altered granodiorite using well-established statistical methods with an upscaling approach. With this approach, the samples were measured in the laboratory under supervised ambient conditions and in the field under semisupervised conditions. This study further aims to conclude which statistical method provides the best practical and accurate classification for use in future studies. Our results showed that all statistical methods enable the separation of the rock types, although two types of rocks have exhibited almost identical spectra. Furthermore, the statistical methods that supplied the most significant results for classification purposes were principal component analysis combined with k-nearest neighbor with a classification accuracy for laboratory and field measurements of 68.1% and 100%, respectively.

Genesis of interlayer oxidation zone-type uranium deposit in the channel conglomerates, Beisantai area, Junggar Basin: An insight into uranium mineralization

The Beisantai deposit is a newly discovered typical interlayer oxidation zone-type uranium deposit mainly hosted in distributary channel conglomerates of the Neogene Shawan Formation in East Junggar Basin, northwest China. This study aims to reveal the genetic process of the Beisantai deposit and constrain the mineralization characteristics conducted through petrographic observation, Rock-Eval pyrolysis, high-resolution microscopic mineralogical observation based on BSE, C-O isotopes of calcite cement, and in-situ measurements on pyrite of trace elements and S isotope. There are two types of calcite cements, including diagenetic microcrystalline calcite and epigenetic sparry calcite, dominantly occurring in the redox transition zone and the oxidation zone, respectively. The broad heterogeneity of δ13C values, ranging from −29.2‰ to −6.52‰, indicates the mixed sources of carbon. Given the poor organic content in sediments (0.05% in sandstone and from 0.11% to 0.26% in mudstones), the large amount of organic carbon in the transition zone conglomerates, revealed by the super low δ13C values, is attributed to extrinsic hydrocarbons. Besides, the widespread dissolution of microcrystalline calcite also indicates a weakly acidic environment in the formation. The heavy carbon isotopes are sourced from surface freshwater and the dissolved CO2, which causes the epigenetic metasomatism of early-stage calcite. Thus, the infiltrated groundwater is characterized as alkaline with carbonate dissolved. Pyrites are highly enriched in ore-bearing rocks, with complex morphologies. The extremely negative sulfur isotopic signatures (δ34S values from −48.38‰ to −35.65‰) indicate that these pyrites precipitate through bacterial sulfate reduction (BSR). Combined with the morphology features, distribution patterns, and the decrease in light sulfur isotope and several trace elements, including As, Se, Ni, and Co between individual pyrites and ore-related pyrites, a successive process of pyritization can be revealed. Ore-related pyrites are formed at the late stage. The pervasive coffinite replacement of pyrite suggests that uranium mineralization should occur after the cessation of pyritization, resulting from the consumption of organic matter. Distinctive bio-oxidation features of pyrite can also be observed, characterized as deep and oriented holes. Thus the role of microbes such as Acidithiobacillus thiooxidans is non-negligible, which enhances the dissolution rate of pyrite and the reduction of U(Ⅵ). Overall, as the major reducing material during the ore stage, the large amount of pyrite has played the predominant role in the precipitation of coffinite, with the catalysis and acceleration of microbes.

Thorium, uranium and rare earth mineralization in rocks of the Ugakhan gold deposit, Bodaibo ore region (Irkutsk oblast)

The paper reports on the results of studies of ore-bearing rocks of the Ugakhan gold deposit (Bodaybo district): metasandstones, metasiltstones and carbonaceous shales. The rocks consist of quartz, feldspar (albite, orthoclase), Fe-Mg chlorite, mica (muscovite, sericite) and carbonates (calcite, dolomite, anker-ite) and accessory titanite, rutile, tourmaline, zircon and apatite. All rocks contain fragments of microfossils exhibiting striking concentric zonation with alternated dark (carbonaceous matter) and light (carbonate-mica material) layers. In a range from metasandstones to carbonaceous shales, the rocks exhibit an increase in mica amount and the content (up to 3%) of carbonaceous matter, as well as the formation of regeneration rims around relict tourmaline and zircon. The REE mineralization includes silicates (REE-bearing epidote, thorite), fuorocarbonates (bastnesite) and phosphates (monazite, xenotime, ankylite), which are closely related to U minerals (uraninite, cofnite). Bastnesite, ankylite and thorite formed due to the decomposition of earlier REE-bearing epidote, whereas monazite and xenotime are the products of decomposition of apatite. Uraninite formed during lithifcation of matrix of carbon-bearing rocks and is replaced by cofnite. The thermal analysis of carbonaceous matter and the formation temperature of chlorite calculated using chlorite geothermometer (296–371 °С) indicate the transformation of rocks under conditions of sericite-chlorite subfacies of greenschist facies of metamorphism.

The Sulfide/Silicate Coefficients of Nd and Sm: Geochemical “Fingerprints” for the Syn- and Epigenetic Cu-Ni-(PGE) Ores in the NE Fennoscandian Shield

One of the current directions of the Sm-Nd isotope systematics development is a dating of the ore process using sulfide minerals. Yet, the issue of the existence of rare earth elements (REE) in sulfides is still a matter for discussion. Sulfides from ore-bearing rocks of Proterozoic (2.53–1.98 Ga) Cu-Ni and platinum group elements (PGE) deposits of the Fennoscandian Shield were studied. It is found that the most probable source of REE in sulfide minerals from Cu-Ni-PGE complexes could be submicronic fluid inclusions, which are trapped at the mineral crystallization stage. In such a case, fluid or melt inclusions are specimens of the syngenetic parental melt, from which the base mineral formed, and these reflect a composition of the parental fluid. The mineral–rock partition coefficients for Nd and Sm can be used as “fingerprints” for individual deposits, and these are isotope-geochemical indicators of the ore-caused fluid that is syngenetic to sulfide. Moreover, the DNd/DSm ratio for various sulfide minerals can be used as a prospective geochemical tool for reconstructing a mineral formation sequence in ore complexes. On the other hand, differences in isotope compositions of sulfide neodymium could be markers of some ore-caused fluids and related to certain generations of sulfide minerals.

Geological and geochemical specialization of ore-bearing formations

The geochemical and metallogenic specialization and zoning of structural-material complexes are analyzed. In the general systematic operational circuit of metallogenic forecasting and geological prospecting, processing the data on the geochemical specialization of geological formations and their constituents make it possible to perform a formational interpretation of anomalous geochemical fields revealed in the course of multipurpose geological and geochemical mapping; to subdivide the explored areas by the types of geological formations differing by their ore-bearing potential, with allocation of the most productive subformations, phases, and facies; and to provide quantitative estimates of the forecasted resources. Geochemical criteria of the ore-bearing potential of geological formations consist, first of all, in stable correlations between petrochemical features of ore-bearing rocks and their corresponding fluctuations of the ore composition (for example, the correlation of the potassium content of ore-hosting silicic volcanic rocks of the ore-bearing volcanogenic geological formations with the Cu/Pb ratio in ores of various types of deposits of the VMSD formational family). These criteria are to be taken into account in regional and local assessments of the perspective ore-bearing potential of geological formations.

Gold occurrences in copper-magnetite-apatite deposit at Seruwila, Sri Lanka

This study presents petrology and evidence for possible gold occurrences in Seruwila copper–iron oxide–apatite (IOA) deposit, hosted in an ultramafic intrusion which is located at the boundary between the Highland and Vijayan complexes, within the intermediate-granitic basement in north-eastern Sri Lanka. The study is complemented with petrological observations and XRD and SEM analysis, respectively, to investigate the petrology/subsurface geology of the deposit and identify possible gold occurrences in the deposit. The ore-bearing rocks are mainly composed of magnetite and apatite in various proportions, hosted in an ultramafic intrusion with cumulate features within the granitic-intermediate basement. The secondary veins contain magnetite, chalcopyrite, pyrrhotite, and pyrite together with apatite and scapolite, tremolite, diopside, and minor actinolite and calcite, serpentinite, anhydrite, or gypsum. The clinopyroxene euhedral crystals show cumulus textures including grain triple junctions and large dihedral angles (∼120°), showing magmatic origin. Texturally two types of amphiboles are identified as coarse-grained (0.5–1 mm), pale green euhedral amphibole that is free of inclusions, and fine-grained (<0.1 mm) and brownish, occurring as anhedral inclusions in clinopyroxene. The deposit contains varying amounts of sulfides in which pyrite is the potential gold carrier in magmatic–hydrothermal processes. By the results of XRD analysis, it is evident that the presence of Au (111), Au (200), Au (220) and Au (311), although with low count values (50–500), probably due to the low concentration of gold. Therefore, particularly in the samples with veins or veinlets, gold was inferred to be present in pyrite/chalcopyrite as invisible structurally-bonded gold and/or gold nanoparticles. Hence, the results of this study, although at non-ore grade, veinlets of gold-bearing pyrite/chalcopyrite may serve as a promising target for gold occurrence, being a potential site of gold-mineralization in the context of the East-Gondwana.

Regional multi-sources of Carboniferous karstic bauxite deposits in North China Craton: Insights from multi-proxy provenance systems

The sources of karstic bauxite are complex and have not been so far addressed by multi-proxy provenance studies that interrogate bauxite sources. The Carboniferous bauxite in the North China Craton, which is the largest karstic bauxite area in the world, contains considerable quantities of detrital heavy minerals, including zircon, rutile, tourmaline, and moissanite, allowing multi-proxy provenance studies. In this study, geological, mineralogical, geochemical analyses, and detrital heavy mineral analyses were conducted for the Jiagou and Kuancaoping bauxite deposits located in the southern and northern parts of the North China Craton, respectively. Coupled with previously published geological, geochemical, and detrital mineral data, this study aims to thoroughly clarify the provenance of karstic bauxites in the North China Craton. In general, the ore-bearing rock series contains three units: lower iron-bearing claystone consisting of illite, chamosite, and goethite; middle bauxite ore dominated by diaspore, kaolinite, illite, chamosite, and anatase; and upper bauxitic claystone composed of kaolinite, diaspore, and anatase. Immobile trace element ratios and Rare Earth Element patterns of the bauxites throughout the North China Craton revealed that the lower iron-bearing claystone was autochthonous and directly sourced from the underlying limestone. The isotope data of detrital zircon along with chemical compositions and morphological features of detrital rutile, tourmaline, and moissanite in the bauxite ores revealed that the bauxite ore and bauxitic claystone were mainly para-allochthonous and derived from regional multi-sources. The multi-sources origin is also shared by other karst bauxites in the world. The results indicate that the bauxite deposits in the northern and southern parts of the North China Craton have distinct source materials. The provenance of the bauxite in the northern part of the North China Craton is mainly from the northern margin craton orogenic belt and the adjacent intraplate paleo-uplifts, whereas in the southern part, it is dominated by the North Qinling orogenic belt and the nearby paleo-uplifts. Consequently, the Carboniferous karstic bauxites in the North China Craton are characterized by the autochthonous origin of the lower iron-bearing claystone and the para-allochthonous origin of the upper bauxite ore and bauxitic claystone. This clearly illustrates the dependence of provenance information on mineral proxy choice and underlines the preponderance of multiproxy provenance studies to solve the complex source issue of karst bauxites in North China Craton.

A path for evaluating the mechanical response of rock masses based on deep mining-induced microseismic data: A case study

Deep, high-intensity mining has become a general development trend in mineral resource extraction operations. Under deep mining conditions, high-intensity mining renders the mechanical environment more complicated. The strong disturbance caused by excavating ore-bearing rocks may trigger ground-pressure-induced disasters, and the associated disaster mechanism is more complex. In the mining of deep metal orebodies, stope stability has been a crucial factor restricting mining safety. In response to the above problems, a path for evaluating the mechanical response of surrounding rocks using mining-induced microseismic (MS) data was proposed and applied to a test stope of the Xiadian Gold Mine, which has experienced stope instability as a result of deep mining. First, MS data received before, during, and after the mining of the test stope were analyzed to explore the evolution of MS events, the failure mechanism, and the evolution of fractures during different stages. Subsequently, by utilizing the method for calculating the damage, seismic stress, and seismic strain defined by the moment tensor (MT), the dynamic response trends of damage, stress, and strain during the mining of the test stope were investigated. Finally, the proposed damage model based on fractures derived from MS data was mapped into a finite element numerical analysis. According to the time sequence of the stope mining, the rock mass parameters were dynamically weakened to investigate the changes in the plastic zone and the displacement of the test stope under the original and new stope structures and determine the stability of surrounding rocks under the new stope structure. The research is expected to aid in the mining design and support design of deep mines and provide a reference for the same type of mines elsewhere.

Formation conditions of noble metal mineralization in sulfide cobalt-copper-nickel ores of Kamchatka (on the example of Annabergitovaya Schel ore occurrence)

The authors present research results, the purpose of which is to study the specifics of noble metal mineralization and its genesis in sulfide cobalt-copper-nickel ores of the Kamchatka nickel-bearing province. The paper is dedicated to one of its many ore occurrences called Annabergitovaya Schel (Annabergite Gap). The material composition of platinoid, silver, gold, bismuth and tellurium minerals, as well as sulfarsenides in the ores of this occurrence was investigated. Based on the data of mineral formation sequence and the use of geosensors, conclusions were drawn regarding the genesis of noble metal mineralization.&#x0D; Formation of platinoid minerals, silver and gold at the Annabergitovaya Schel ore occurrence is mainly associated with the epigenetic effect of post-ore granitoids on ore-bearing intrusion rocks of the Dukuk complex of the cortlandite-norite formation and on syngenetic ores. An early association of noble metal minerals is represented by sperrylite, irarsite, and rare unnamed phases of Pt + Ir + Te. Irarsite and Pt + Ir + Te phases were formed at the contact-metasomatic stage. Sperrylite can be assumed to be of magmatic origin. Silver sulfides and tellurides, silver and palladium bismuth tellurides, and native gold were formed at the late, hydrothermal-metasomatic, stage. The occurrence conditions of mineral parageneses, associated with noble metal mineralization, correspond to the formation of shallow-depth metasomatic rocks (5 km). Sub-developed quartz-feldspar metasomatites, associated with the formation of early platinoid arsenides and sulfarsenides, are in equilibrium with circumneutral solutions (pH of 4.5-6.5) at temperatures of 350-600 °C. Late hydrothermal association with Pd, Ag and Au minerals is close to propylites and was formed at pH values of 4.5-6.5 and temperature of 150-350 °C.

The Influence of Size Effect on Strength and Deformation Characteristics of Different Types of Rock Samples

This paper presents the results of the experimental study of the influence of sizes effect on the strength and deformation characteristics of samples of hornfels, limestone, sandstone, siltstone and ore-bearing rocks. Tests were performed on cylindrical samples of three sizes of diameters - 10, 30 and 60 mm under uniaxial compression and tension loading. The results of the study demonstrated that the values of ultimate strength decrease when the size of samples increases for the samples of cornea, limestone, sandstone and siltstone. The ultimate strength increases with increasing of sample size for ore-bearing rocks containing viscous inclusions. The samples of smaller size of ore-bearing rocks exhibit a brittle character of the fracture for all types of rocks, and the viscosity of fracture increases with increasing size of samples. the obtained regularities were analysed from the positions of otwo types of size effect (volume and surface).

Biotite 40Ar/39Ar dating and chemical composition inform metallogenesis of Xiaoxi'nancha porphyry Au-Cu deposit, NE China

• Zircon U-Pb dating of ore-bearing rocks show age of ~255 Ma. • Hydrothermal biotite 40 Ar/ 39 Ar age show ~110 Ma. • The same age (biotite and molybdenite) indicate coeval Au-Cu-Mo mineralization . • Halogen fugacity ratios imply a relatively Cl-rich hydrothermal system . The Xiaoxi'nancha Au-Cu porphyry deposit, located in the eastern Jilin Province of Northeast China, is characterized by widespread biotite alteration, however, the age of Au-Cu mineralization is not well established. Hydrothermal biotite Ar/Ar dating and chemical composition are widely used to constrain the age and physico-chemical characteristics of hydrothermal fluids. In this paper, microscopy observation, electron microprobe analysis, and 40 Ar/ 39 Ar dating of hydrothermal biotite from the Xiaoxi'nancha porphyry Au-Cu deposit and zircon U-Pb dating on the ore-bearing granitoids have been carried out to constrain fluid characteristics and the age of mineralization. The zircon crystals from the ore-bearing granitoids display obvious inherited cores and oscillatory rims. A range of 206 Pb/ 238 U age populations were obtained on the cores (e.g., ~967 Ma, ~782 Ma, ~495 Ma, ~430 Ma, ~385 Ma, ~354 Ma, ~311 Ma) but a young population with a uniform concordia age of 254.4 Ma was determined on the rims. These features indicate the occurrence of xenocrystic zircon in the ore-bearing granitoids, and imply that these rocks were probably derived from partial melting of continental crust with significant crustal contamination. Au-Cu and Mo mineralization are found together and associated with potassic and chlorite alteration. The 40 Ar/ 39 Ar age of hydrothermal biotite (~110 Ma) is younger than the zircon U-Pb age (~255 Ma), but similar to the previously published molybdenite Re-Os age (~110 Ma). Thus, Au-Cu mineralization is coeval with Mo mineralization and formed at ~110 Ma, and has no genetic relationship with ore-bearing granitoids. The calculated log( f H 2 O/ f HF) and log( f H 2 O/ f HCl) ratios of hydrothermal fluids are similar to those determined at other major porphyry deposits. However, the log( f HF/ f HCl) ratio is lower than that of other porphyry deposits, indicating a relatively Cl-rich hydrothermal system at Xiaoxi'nancha. The Xiaoxi'nancha porphyry Au-Cu deposit is associated with early Cretaceous granitoids, generated during subduction of the Paleo-Pacific Ocean.

Age of Ore-Bearing Rocks at Devonian Fe–Mn Deposits, Central Kazakhstan

Age of Ore-Bearing Rocks at Devonian Fe–Mn Deposits, Central Kazakhstan

Two episodic Nb-Ta mineralization events and genesis of the Zhaojinggou rare-metal deposit, north margin of the North China Craton

The Zhaojinggou rare-metal deposit is located in the Wulashan-Daqingshan region, central north margin of the North China Craton. Nb-Ta mineralizations are mainly hosted in the biotite alkali-feldspar granite (BAG) and albite granite (AG), with subordinate mineralization in the alkali-feldspar aplite dyke (AFA), the amazonite granitic pegmatite dyke (AGP), and the greisen (black + white colored greisen). In this paper, we present a systematic work of geochronology (CGM U-Pb combined with cassiterite U-Pb, monazite U-Th-Pb, and muscovite 40Ar-39Ar dating), whole-rock geochemistry, and Sr-Nd isotopes to understanding the timing of mineralization, petrogenesis, geodynamic setting, and ore-forming processes. Our geochronological data reveal two episodic Nb-Ta mineralization events in the Zhaojinggou deposit during the Early Cretaceous. The first and major ore-forming episode occurred at ~130 Ma, forming a sequence of ore-bearing rocks of the BAG-AG-greisen-AFA. The second but subordinate ore-forming episode occurred at ~114 Ma, forming the ore-bearing AGP. The whole-rock geochemistry indicates the granitic rocks (the BAG-AG-AFA and AGP) from the two episodes are highly evolved with analogous trace element and REE patterns, and have A-type affinity. The whole-rock εNd(t) values of these granitic rocks are relative similar, ranging from −9.6 to −7.6, with corresponding T2DM ages of 1490–1713 Ma. These features suggest that these A-type granites from the two discrete episodes are derived from the same magma reservoir by high-temperature partial melting of the Middle Proterozoic basement in an infracrustal extensional environment. These A-type granites experienced extremely fractional crystallization during emplacement. The whole-rock REE tetrad effects, element ratios (Nb/Ta, Zr/Hf and K/Rb), and Nb-Ta fractionation modeling indicate that both magmatic and hydrothermal processes are involved to form the two episodic Nb-Ta mineralizations. High degree of factional crystallization and magmatic-hydrothermal processes after high-temperature anataxis are crucial to form the Zhaojinggou rare-metal deposit. Moreover, these highly-evolved A-type granites (the BAG-AG-AFA and AGP) formed during the Early Cretaceous (at ~ 130 Ma and ~ 114 Ma respectively) are the important targets for rare-metals prospecting in the central north margin of the NCC.

Distribution peculiarities of basic ore components in Goshgarchay porphyrous copper deposit (lesser Caucasus, Azerbaijan)

Formulation of the problem. Large size and great reserves, as well as the possibility to apply rational methods of metals extraction predetermined the increasing interest to the copper-porphyry deposits. Today, they are the main raw material based on Cu, Mo, accompanying metals all over the world. The value of these deposits lie in the fact that they are in located in geologically well-studied regions. However, their ores in basic and associated components have relatively small content of Cu, Mo, Au, Ag, Bi, Re, Se, Te, spreading in large area. The purpose of the article. The main objective of the research is to study distribution peculiarities of basic ore components of Goshgarchay deposits, to detect geochemical features and behaviour of elements in the process of sedimentation by developing geochemical criteria of the search and the prognosis of hidden mineralization. Methods. The author studied the distribution problem of basic ore components of copper-porphyry mineralization, carried out field investigations (field researches), documented and tested underground mine working and core samples of over seventy well bores. When choosing the type of analysis, a special attention was paid to the sensitivity and exactness of the determination method. Analytical work was conducted according to the definition of chemical elements. The following types of analytical methods were used: chemical, atomic-absorption, spectral-chemical, etc. The analytical data were processed by the method of mathematical statistics. Results. As follows from the analysis of the above-mentioned results, the elements flaccid for hydrothermal solutions (Cr, Ni, V, Co, Mn, Ti) keep their independence in all groups of rocks. Their grouping is probably associated with the process of crystallized differentiation of magma. The elements Cu, Pb, Zn, Ag and partly Mo, don’t have specific place. Their presence is likely associated with the degree of rocks susceptibility, hydrothermal interaction being the source of these elements. In various types of ores and mineral associations the definition of elemental impurities is different. Their amount increases the amount (quantity) of clarke and coefficient of concentration a thousand times. Three different mineral associations coexist in the ore body: 1-primary sulphide-chalcopyrite and bornite-chalcopyrite ore. 2-oxidized ore and zone of secondary enrichment. 3-primary sulphide ore, significantly enriched in copper. Scientific novelty. Based on existing analytical data, the author studied distribution of basic ore and admixture components (gangue) and basic sulphide minerals. The concentration in series of elemental impurities were detailed in ore-bearing rocks of copper-porphyry deposits of Goshgarchay. The primary geochemical zonality was revealed in the distribution of basic ore-containing components in the ore body of copper-porphyry deposits of Goshgarchay ore field. Practical significance. The revealed peculiarities of the distribution of basic ore components in the ore body and host rocks (wallrock), the factors contributing to the accumulation of indicated elemental impurities can be used as geochemical criteria for the prognosis of copper-porphyry mineralization , supporting the effective directions of the research.

Mineralization and petrogenesis of the Qiongheba porphyry copper deposit in Mengxi district, East Junggar, China

The Qiongheba porphyry Cu deposit is characterized by geochemical features of island arc and adakitic intrusions with fractional crystallization playing a key role in the formation of the ore-bearing rocks. Calculated sulfur concentrations in silicate melts at sulfide saturation show that two-thirds of the sulfur was exsolved during the fractional crystallization process to contribute to the formation of sulfides. The ore-bearing rocks in the Qiongheba area yielded U-Pb zircon ages of 414–412 Ma coeval with the 412 Ma Re-Os age of molybdenite indicating that sulfide mineralization is broadly coeval with magmatic crystallization. The color cathodoluminescence of quartz (purple) and K-feldspar (pink) in the fibrous veins and miarolitic cavities (Qtz-2 and Kfs-2) are the same as those (Qtz-1 and Kfs-1) in the granitic porphyry whereas the hydrothermal quartz (Qtz-3) and K-feldspar (Kfs-3) are black and green, suggesting that the color cathodoluminescence can be used to unravel the paragenesis of PCD. The oxygen isotopic values of Qtz-1 and Qtz-2 range from 9.15 to 10.1‰ and 8.93 to 10.4‰ with calculated equilibrium fluid compositions of 9.86 to 11.7‰ and 10.5 to 12.0‰, respectively, indicating a magma-dominated fluid composition, whereas Qtz-3 veins have very low oxygen isotopic values from −4.60 to −1.25‰ with corresponding fluid compositions of −3.51 to −0.17‰, implying that the fluid formed via the mixing of magmatic and meteoric water. Titanium-in-quartz thermometry constrains the magmatic crystallization to 580–627 °C, whereas the magmatic to hydrothermal transition occurred at 523–613 °C.

Geochemistry of the Yudong bauxite deposit, south-eastern Guizhou, China: Implications for conditions of formation and parental affinity

The Yudong bauxite deposit is located in the Kaili–Huangping bauxite-concentrated area, in south-eastern Guizhou Province, China. The ore-bearing rock series consists of the lower part (Fe-bearing member) and middle part (Al-bearing member) of the Middle Permian Liangshan Formation, covering the Upper Devonian Gaopochang Formation. The elemental content in the ore-bearing profile is variable. In general, Al, Ti, V, Cr, Zr, Nb, Hf, Th, and U increase from the Fe- to the Al-bearing member, whereas Si, Fe, Rb, Cs, Ba, and total rare earth elements (REE) decrease. These observations indicate the occurrence of bauxitisation, which corresponds to a process of elemental variation during which Si and Fe were dissolved and migrated, and Al was enriched. Compared with Ordovician–Silurian (O–S) mudrock, the ore-bearing rock series are enriched in Al, Ti, V, Zr, Hf, Nb, Ta, Th, and U, but depleted in Si, Fe, Rb, Cs, and Ba as a result of weathering. The REEs show negative correlations with Si, Fe, K, Na, Ca, Mg, and Y, indicating that the REEs may be associated with clay, Fe-bearing, and Y-bearing minerals.The La/Y ratio, (La/Yb)N ratio, and Ce anomalies show that the Fe-bearing member formed in an alkaline reducing environment, whereas the Al-bearing member formed in an acidic oxic environment. The immobile element ratios, Eu anomalies, REE distribution patterns, and Cr–Ni diagram, as well as the comparison with worldwide bauxite deposits, show that the ore-bearing rock series may have originated in the O–S mudrock, with contributions from the dolomite of the Gaopochang Formation. Furthermore, the position of the samples in the Al2O3–Fe2O3–SiO2 ternary plot, the chemical index of alteration, and the strong positive correlations of some stable elements (such as Al, Ti, Zr, Hf, Nb, and Ta) indicates that the degree of weathering gradually increases from the O–S mudrock to the bauxitic mudrock, and further increases into the bauxite; the bauxitic mudrock and bauxite therefore originated from the O–S mudrock. The laterisation products of the O–S mudrock from the northern part of the ore collection area were transported to the karst depression in the early stages of the Middle Permian. The weathering products of the O–S mudrock and a small amount of the Gaopochang Formation dolomite accumulated on the karst interface, forming the original bauxite layers through cycles of compaction and concretion. These bauxite layers were then uplifted to or near the surface during the Late Cretaceous to Paleogene, eventually, forming karstic bauxite.

ЭФФЕКТИВНОСТЬ КОМБИНИРОВАНИЯ ТЕХНОЛОГИЙ ВЫЕМКИ РУД В ПРЕДЕЛАХ РУДНОГО ПОЛЯ

Актуальность исследования. Статья посвящена актуальной проблеме совершенствования технологии разработки сложно-структурных месторождений скального типа для увеличения производства содержащихся в рудах редких и ценных металлов, дефицитность которых возрастает с развитием научно-технического прогресса. Цель исследования – определение условий совмещения систем разработки разных классов для увеличения возможностей селективизации добычных работ при использовании различных вариантов извлечения руд в смежных добычных участках. Методика исследования. Основу исследования составляет экономический расчет возможных вариантов совмещения в пределах рудного поля на основе полученных экспериментально сведений о рудовмещающем массиве. Результаты. Дана характеристика условий залегания руд на конкретном скальном месторождении сложной структуры. Произведено инженерно-геологическое районирование рудовмещающего массива с дифференцированной оценкой геолого-структурных нарушений по величине и направленности. Дан прогноз возможного по аналогии с практикой поведения горных выработок под влиянием разломных структур и макротрещин. На уровне экспертной оценки определена целесообразность применения слоевой или камерной систем разработки с закладкой технологических пустот твердеющими смесями. Выводы. Эффективность выемки руд достигается селективизацией выемки запасов в пределах одного рудного поля при комбинировании систем разработки при максимальном учете геолого-структурных факторов локализации руд и механо-физических свойств рудовмещающих пород.

Energy Evolution Law of Ore-Bearing Rock during Unloading under High Static Stress and Frequent Disturbance

Based on the complex engineering environment in deep rock engineering, preloaded high axial pressure, unloading of axial pressure, and impact loading were used to simulate high in situ stress, unloading of excavation, and blasting disturbance, respectively; the experimental study on frequent impact disturbances under unloading of high static load was carried out, which aimed at revealing the energy evolution law of rock. First, the equations of elastic property, plastic energy, and incident energy in the impact process are discussed by theoretical analysis. Then, it is found by further investigation that dynamic stress-strain curve and envelope curve of rock are with the same change tendency. The initial stage was short straight stage, and then linear stage appeared and was less influenced by unloading rate. The plastic energy, the ratio of reflected energy to incident energy, and the energy consumption per unit volume of rock increase during impact. The higher the preloaded axial pressure is, the greater the ratio of reflected energy to incident energy is, the smaller the ratio of transmitted energy to incident energy and the average energy dissipation per unit volume of rock are. When the unloading rate increased, the elastic energy generated by impact gradually increased, the plasticity gradually weakened, the ratio of transmitted energy to incident energy increased, and the ratio of reflection energy to incident energy decreased.