Mineral Province Research Articles

Age and generation conditions of quartz crystal deposits in the Subpolar Urals

Research subject. The Dodo and Puiva quartz crystal deposits in the Neroiskiy mineral province (Subpolar Urals) were studied. Although these deposits have received sufficient research attention, a number of issues remain to be elucidated, including the age of crystal-bearing mineralization and the age of host rocks. Aim. In this work, we aim to determine the age of the metasomatites that bear quartz crystal mineralization and to develop a model of the formation of the Dodo and Puiva deposits. Materials and Methods. 40Ar/39Ar dating was carried out according to the method described by A.V. Travin et al. The argon isotope composition was measured on a Micromass 5400 mass spectrometer (IGM SB RAS). Results. Microprobe studies of the mineralogy of the Dodo and Puiva quartz crystal deposits were carried out. The temperatures of meta-somtaite formation were determined to range within 339–364°C. Six main structural and morphological types of quartz veins were identified and described. The 40Ar/39Ar ages of mica of quartz crystal deposits and host metamorphic schists were determined. Reliable plateaus were obtained, the values of which ranged within 251–257 Ma and agreed with each other within the deviation (average for 4 dates is 255 ± 2 Ma). Conclusion. A new model for the formation of quartz crystal deposits in the Subpolar Urals is proposed. The obtained 40Ar/39Ar ages correspond to the period of the post-orogenic extension of the Urals. At that time, a system of meridional grabens and rifts was formed in the Urals and in the West Siberian Plate. At the same time, and as a result of the same stretching impulse, large blocks of the middle crust (granite, schist, etc.) were brought to the Earth’s surface in the Urals. During the rise of deep blocks, at a depth of 10 km, a sharp, approximately 3-fold drop in fluid pressures (from lithostatic to hydrostatic) and a strong decrease in temperatures due to adiabatic expansion and the throttling effect occurred. The obtained 40Ar/39Ar ages (255 Ma) reflect not only the age of the quartz crystal deposits of the Subpolar Urals, but also place the moment of rise of the entire Central Ural uplift above a depth of 10 km, i.e., to the level of the upper cortex.

Contribution of mine borehole data toward high-resolution stress mapping: An example from northern Bowen Basin, Australia

Most of in-situ stress data in the Australian continent comes from wellbore stress analysis in deep hydrocarbon reservoirs, and earthquake focal mechanism solutions near the Australian plate boundaries, where geophysical tools facilitate understanding of the present-day stress patterns. This resulted in a paucity of stress information in many other regions such as the northern Bowen Basin, which is an active mining province, but with low seismicity rates and limited deep petroleum exploration. The mining industry runs several hundred kilometres of image logs annually to characterise geotechnical attributes. These logs provide an image from the borehole wall, which facilitates analysis of stress-related borehole deformations for in-situ stress characterisation. This paper examines the orientation of horizontal in-situ stress using different types of image logs in mine boreholes across the northern Bowen Basin. Analyses of 128 km of image logs in 680 vertical boreholes resulted in the interpretation of 9046 pairs of stress-related indicators including 735 drilling induced fractures and 8311 borehole breakouts. Our comprehensive database comprises 890 quality-ranked data records for the orientation of maximum horizontal stress (SHmax), which makes the Bowen Basin as a basin with the highest data density in the world in terms of quality-ranked stress information according to the World Stress Map. Statistical analysis of SHmax orientation reveals that the mean SHmax orientation in northern Bowen Basin is N018° ± 16°. The results show that this orientation is consistent over long distances, which is in contrast with several eastern Australian basins. This uniform stress pattern agrees well with plate-scale geomechanical model predictions, which further highlights the impact of plate boundary forces in the contemporary stress pattern of this region. Detailed image log investigation did not show any systematic rotation of stress; however, some small-scale stress perturbations were observed in the vicinity of sharp stiffness contrasts and geological structures.

Geochemical and Isotopic Fractionation in the Hypogene Ore, Gossan, and Saprolite of the Alvo 118 Deposit: Implications for Copper Exploration in the Regolith of the Carajás Mineral Province

In the Carajás Mineral Province, gossan formation and lateritization have produced numerous supergene orebodies at the expense of IOCG deposits and host rocks. The Alvo 118 deposit comprises massive and disseminated hypogene copper sulfides associated with gossan and mineralized saprolites. The hypogene reserves are 170 Mt, with 1% Cu and 0.3 ppm Au, while the supergenes are 55 Mt, comprised of 30% gossan and 70% saprolite, with 0.92% Cu and 0.03 ppm Au. The gossan includes goethite, malachite, cuprite, and libethenite zones. The saprolite comprises kaolinite, vermiculite, smectite, and relics of chlorite. In the hypogene mineralization, Ag, Te, Pb, Se, Bi, Au, In, Y, Sn, and U are mainly hosted by chalcopyrite and petzite, altaite, galena, uraninite, stannite, and cassiterite. In the gossan, Ag, Te, Pb, Se, and Bi are hosted by Cu minerals, while Au, In, Y, Sn, and U are associated with iron oxyhydroxides, in addition to Zn, As, Be, Ga, Ga, Mo, Ni, and Sc. As supporting information, δ65Cu values indicate that the gossan is immature and, at least partly, not affected by leaching. In the saprolite, Ga, Sc, Sn, V, Mn, Co, and Cr are associated with the iron oxyhydroxides, partially derived from the host rock weathering. The δ56Fe values indicate that hypogene low contribution of the hypogene mineralization to the saprolite iron content. The association of Al2O3, Hf, Zr, Th, TiO2, Ce, La, Ba, and Sr represents the geochemical signature of the host rocks, with dominant contributions from chlorites, while In, Y, Te, Pb, Bi, and Se are the main pathfinders of Cu mineralization.

Computational aspects of the equivalent-layer technique: review

Equivalent-layer technique is a powerful tool for processing potential-field data in the space domain. However, the greatest hindrance for using the equivalent-layer technique is its high computational cost for processing massive data sets. The large amount of computer memory usage to store the full sensitivity matrix combined with the computational time required for matrix-vector multiplications and to solve the resulting linear system, are the main drawbacks that made unfeasible the use of the equivalent-layer technique for a long time. More recently, the advances in computational power propelled the development of methods to overcome the heavy computational cost associated with the equivalent-layer technique. We present a comprehensive review of the computation aspects concerning the equivalent-layer technique addressing how previous works have been dealt with the computational cost of this technique. Historically, the high computational cost of the equivalent-layer technique has been overcome by using a variety of strategies such as: moving data-window scheme, column- and row-action updates of the sensitivity matrix, reparametrization, sparsity induction of the sensitivity matrix, iterative methods using the full sensitivity matrix, iterative deconvolution by using the concept of block-Toeplitz Toeplitz-block (BTTB) matrices and direct deconvolution. We compute the number of floating-point operations of some of these strategies adopted in the equivalent-layer technique to show their effectiveness in reducing the computational demand. Numerically, we also address the stability of some of these strategies used in the equivalent-layer technique by comparing with the stability via the classic equivalent-layer technique with the zeroth-order Tikhonov regularization. We show that even for the most computationally efficient methods, which can save up to 109 flops, the stability of the linear system is maintained. The two most efficient strategies, iterative and direct deconvolutions, can process large datasets quickly and yield good results. However, direct deconvolution has some drawbacks. Real data from Carajás Mineral Province, Brazil, is also used to validate the results showing a potential field transformation.

Predictive Mapping of Prospectivity for Gold in the Central Portion of the Tapajós Mineral Province, Brazil

This work aims to model mineral prospectivity for intrusion–related gold deposits in the central portion of the Tapajós Mineral Province (TMP), southwestern Pará state. The scope includes experimentation and evaluation of knowledge and data-driven methods applied to multisource data to predict potential targets for gold mineralization. The radiometric data processing allowed to identify a hydrothermal alteration footprint of known gold deposits, providing information in regions with little or no field data available. The aeromagnetic data analysis prompted the identification of high magnetic zones, which are probably related to hydrothermal fluid transport. Linear features extracted from digital elevation data revealed an NNW–SSE general trend, which is consistent with the main structural control of deposits. The data were integrated through three modeling techniques—fuzzy logic (knowledge-driven), weights of evidence (WofE, data-driven), and a machine learning algorithm (SVM, data-driven)—resulting in three prospective models. In all models, the majority of indicated prospective regions coincide with the known deposits. The results obtained in the models were combined to generate an agreement map, which mapped the overlapping of their highest prospective scores, indicating new areas of prospective interest in the central portion of the TMP.

Tectonic and metallogenic implications of a metasomatized mantle inferred from magnetotellurics and gravity data: An example of Tapajós Mineral Province, Amazon Craton

The Tapajós Mineral Province (TMP) contains evidence of subduction processes during the Paleoproterozoic. Despite well-documented arc magmatism, the lack of solid geological evidence indicating a collision raises uncertainties about whether there was an arc-continent collision in the Paleoproterozoic or the process of subduction continued, and the closing of an ocean basin occurred only in Mesoproterozoic times. Additionally, world-class deposits have been linked with lithospheric electrical conductors using magnetotelluric (MT) data. On the lithospheric scale, an assessment of the potential for more significant deposits or correlated commodities is absent in the TMP. Therefore, we acquired MT data to provide constraints for the lithosphere of the TMP. The electrical resistivity model reveals a high resistivity zone (> 10,000 Ω.m) interpreted as the emplacement zone of granitoids in the upper crust. The mid-lower crust presents resistivity between 465 and 45 Ω.m, corresponding to depths of 10–35 km. A low resistivity zone below 35 km (45–10 Ω.m) represents a hydrated upper mantle due to the long-lived arc processes. Based on gravity-forward modeling, we estimate that the degree of serpentinization is <10% due to post-subduction magmatism. The lack of a lower crust conductor and paired high and low long wavelength Bouguer anomalies corroborates that a cryptic suture is unlikely. A low-angle conductor matches the limit of different magnetic domains and reveals the exhumation of the western portion of TMP's crust. The high correlation between the position of the deposits and electrical conductors corroborates that MT is a valuable tool for detecting fossil fluid pathways relevant to finding new mineral deposits.

Marker Minerals in Volcanics and Xenoliths—An Approach to Categorize the Inferred Magmatic Rocks Underneath the Present-Day Volcanic Landscape of Tenerife, Spain (NW African Rare Mineral Province)

A mineralogical mapping (terrain analysis) based on micro-mounts has been performed in the Archipelago of the Canary Islands, Spain. The rare elements Be, F, Li, Nb, Ta, Zr, Hf, and rare earth elements (REE) were investigated on the largest island of the Canary Islands Archipelago, Tenerife, Spain. This study forms a contribution to the metallogenetic evolution of the offshore area of the NW African Rare Mineral Province. The finds made at Tenerife were correlated by means of minero-stratigraphy with the adjacent islands La Gomera, Gran Canaria and Fuerteventura, where typical critical element host rocks, e.g., carbonatites, are exposed. At Tenerife, these hidden rock types are only indicated by a wealth of 128 compositional first-order marker minerals hosting Be, F, Zr, Nb, Ta, Zr, Hf, Li, Cs, Sn, W, Ti and REE plus Y and another 106 structural second-order marker minerals describing the geodynamic and morpho-structural evolution of Tenerife (Mn, Fe, Pb, U, Th, As, Sb, V, S, B, Cu, Zn, Mo, Au). Based upon the quantitative micro-mineralogical mapping of lithoclasts and mineralogical xenoliths (foid-bearing monzodiorite/gabbro, (nepheline) syenite, phonolite trachyte) in volcanic and volcaniclastic rocks, hidden intrusive/subvolcanic bodies can be delineated that are associated with contact-metasomatic, zeolitic and argillic alteration zones, as well as potential ore zones. Two potential types of deposits are determined. These are pegmatite-syenites with minor carbonatites bound to a series of agpaitic intrusive rocks that are genetically interlocked with rift zones and associated with a hotspot along a passive continental margin. Towards the east, the carbonatite/alkali magmatite ratio reverses at Fuerteventura in favor of carbonatites, while at Gran Canaria and La Gomera, shallow hypogene/supergene mineral associations interpreted as a marginal facies to Tenerife occur and a new REE discovery in APS minerals has been made. There are seven mineralizing processes different from each other and representative of a peculiar metallogenic process (given in brackets): Protostage 1 (rifting), stages 2a to 2d (differentiation of syenite–pegmatite), stages 3 to 4b (contact-metasomatic/hydrothermal mineralization), stages 5a to 5b (hydrothermal remobilization and zeolitization), stage 6 (shallow hypogene-supergene transition and kaolinization), and stage 7 (auto-hydrothermal-topomineralic mineralization). The prerequisites to successfully take this holistic approach in economic geology are a low maturity of the landscapes in the target area, a Cenozoic age of endogenous and exogenous processes amenable to sedimentological, geomorphological, volcano-tectonic and quantitative mineralogical investigations. The volcanic island’s mineralogical mapping is not primarily designed as a proper pre-well-site study on the Isle of Tenerife, but considered a reference study area for minero-stratigraphic inter-island correlation (land–land) and land–sea when investigating the seabed and seamounts around volcanic archipelagos along the passive margin, as exemplified by the NW African Craton and its metallogenic province. This unconventional exploration technique should also be tested for hotspot- and rift-related volcanic islands elsewhere on the globe for mineral commodities different from the ones under study.

Breaking up the temporal link between granitic magmatism and iron oxide-copper–gold (IOCG) deposits in the Carajás Mineral Province, NW Brazil

Breaking up the temporal link between granitic magmatism and iron oxide-copper–gold (IOCG) deposits in the Carajás Mineral Province, NW Brazil

The Colíder Paleoproterozoic felsic volcanism: New insights into stratigraphy and petrogenesis in the southern Amazonian Craton

The eastern side of Alta Floresta Mineral Province (AFMP) (União do Norte region) comprises an effusive/subvolcanic phase, explosive phase, and epiclastic rocks. The effusive/subvolcanic phase comprises massive porphyritic rhyolite with different degrees of crystallinity, porphyritic rhyolite with flow structure, and microcrystalline rhyolite. The explosive phase is characterized by welded lapilli tuff, lapilli tuff with flow structure, stratified lapilli tuff, and tuff with accretionary lapilli. Sandstones and siltstones characterize epiclastic rocks. There are porphyritic rhyolite dikes that cut the volcanic sequence. The rocks of the Colíder Group are rhyolites (>70 % SiO2) with calcic-alkaline to alkaline-calcic affinity. A rhyolitic rock is predominantly ferroan and metaluminous, while a pyroclastic rock is predominantly magnesian to ferroan and meta- to peraluminous in composition. The rocks have a high LREE content, and slight fractionation of HREE suggests they have hybrid geochemical characteristics of high potassium calc-alkaline, shoshonitic, and suggestive affinities of A-type magmas, probably produced in a post-collisional orogenic environment. These rocks have a relatively high level of Ba and Rb and a negative anomaly for Sr, P, Nb, Ta, and Ti, suggesting an intra-plate mantle source with contributions from a metasomatized mantle edge. The rocks do not have adakitic characteristics nor fertility for Cu-Au (Sr/Y < 1.9 and LaN/YbN < 38.0) as in other regions of the AFMP. The welded lapilli tuff rocks show U-Pb age of 1838 ± 17 Ma and 1817 ± 2 Ma and are the older explosive phases. The effusive/subvolcanic phase has U-Pb ages of 1800 ± 3 Ma and 1792 ± 3 Ma obtained in the massive porphyritic rhyolite. The age interval of approximately 46 Ma (1838–1792 Ma) suggests the presence of two or more volcanic cycles or distinct volcanic events. Based on the interpretation of volcanic and epiclastic deposits and remote sensing products, the paleoenvironmental reconstruction includes subaerial with effusive/subvolcanic and explosive stages in a probable eroded volcanic caldera system with epiclastic rocks from a fluvial depositional system. This volcanic scenario provides more information about the Colíder–Teles Pires volcano-plutonic event, uniquely mapped in AFMP, and offers new insights into the tectonic frame of the Amazonian craton.

Soil Chemical Attributes and Foliar Nutrient Contents of Native Species in Rehabilitation Chronosequence After Iron Ore Mining

ABSTRACT The mineland rehabilitation can be a challenge due to high soil density and low levels of organic matter and nutrients. This study assessed soil chemical attributes and leaf nutritional contents of two native species (Mimosa acutistipula var. ferrea and Vismia baccifera) grown in an iron waste pile under environmental rehabilitation in the Carajás Mineral Province, Eastern Amazon, Brazil. Soil samples were collected close to plant species in three different chronosequences of rehabilitation. Regardless of the rehabilitation stage, the soils have low levels of phosphorus, potassium, calcium, magnesium, and boron. A tendency of organic matter accumulation was observed at the advanced stage (5–8 years after the onset of rehabilitation process) and it was correlated with other soil nutrients. The leaf nutrient’ contents of M. acutistipula and V. baccifera tend to be distinct from each other, which could indicate that the studied species have different nutritional requirements. The V. baccifera presented higher leaf concentrations of sulfur, copper, and zinc, while M. acutistipula stood out for presenting a higher leaf nitrogen content, which is possibly related to its nitrogen-fixing capacity. In general, an improvement of soil chemical attributes was achieved with the advance of the rehabilitation stages, showing the efficiency of the procedures performed to rehabilitate the studied areas.

Mapping copper concentrations in tropical open cast mining fronts from X-ray fluorescence and FAAS techniques: A comparative study

Determining copper (Cu) contents and their spatial distribution in tropical open cast mining fronts is crucial for short-term exploitation planning. However, this evaluation in a fast and accurate way can be directly impaired by methods applied. The aim of this work was to assess the analytical performance of portable X-Ray fluorescence (pXRF) for Cu analysis in the mining fronts at the Cu Sossego Mine, in the Carajás Mineral Province, State of Pará, Brazil. For this, 143 drilling samples were collected in mining fronts at the Sequeirinho pit, an area chosen as representative of the heterogeneity of the Cu levels in the deposit of Sossego Mine. The samples were analyzed with three different techniques to determine the Cu levels as follows: pXRF; wavelength-dispersive X-Ray fluorescence (WDXRF); and flame atomic absorption spectrometry (FAAS) after acid digestion with aqua regia (reference method). Results of the three analytical methods were used to generate block models through Leapfroag Geo 6.0 software. Portable XRF data presented a strong positive correlation (>0.70) with the results obtained by the FAAS. In addition, pXRF performed better than WDXRF, with less dispersed values compared to FAAS. Similar distribution maps were generated using the three methods of analysis. After correction, the average Cu content from the pXRF-generated block model was only 0.15% lower than that derived from FAAS data. Therefore, pXRF is a fast, portable, non-destructive, low-cost, accurate and recommendable method for mining front sample analysis and to assist the quality control and geoscience teams in decision-making for feeding the mineral processing plant.

Comprehensive Risk Assessment of Heavy Metals in Topsoil and Their Risks to Human Health and Ecosystem in Zanjan Mineral Province, Western Iran

Comprehensive Risk Assessment of Heavy Metals in Topsoil and Their Risks to Human Health and Ecosystem in Zanjan Mineral Province, Western Iran

Geochemical signatures of the Neoarchean and Paleoproterozoic copper systems in the Carajás Mineral Province, NW Brazil: Implications for metal endowment

The main copper deposits of the Carajás Mineral Province are grouped into: i) iron oxide-copper-gold (IOCG), and ii) granite-related Cu-Au. They were formed during multiple mineralizing events in the Neoarchean (ca. 2.7; ca. 2.5 Ga) and Paleoproterozoic (ca. 2.1; ca. 1.8 Ga). A combination of non-composition and composition data analysis, molar element ratio, and principal component analysis using a lithogeochemical dataset (n = 1040) has been applied to recognize geochemical associations in these deposits. The Neoarchean IOCG deposits in the Northern and Southern Copper Belts of the Carajás Domain are controlled by ductile structures and comprise high-temperature hydrothermal associations within sodic (albite-scapolite), sodic-calcic (albite-actinolite-scapolite±hastingsite), calcic-iron (magnetite-actinolite-apatite), potassic (biotite-tourmaline±scapolite), potassic-iron (biotite-magnetite; almandine-grunerite-biotite) and iron-rich alteration zones. These zones envelop chalcopyrite-magnetite-actinolite-apatite (e.g., Sequeirinho orebody), magnetite-chalcopyrite-siderite (i.e., Igarapé Bahia deposit) breccias, or massive magnetite bodies with bornite-chalcocite (i.e., Salobo). The Fe-Cu-Au-P-REE association is common to all Neoarchean IOCG deposits of the province. Nevertheless, the IOCG deposits from the northern sector (ca. 2.5 Ga) are also enriched in Ba-Pb-Zn-Ag-Mo-REE ± Sn ± W ± Bi±U ± Nb ± Ta ± Y. Conversely, the chemical signature of Neoarchean (ca. 2.7 Ga) IOCG deposits from the southern sector display enrichment in V-Ni-Co-Cr. Part of these chemical variations may be due to differences in the nature of 7host rocks, including greenstone belt sequences in the south and metasedimentary exhalative rocks in north. Both in the northern and southern sectors, the sodic alteration is marked by Na, Ga, Ti, Sr, Th and Mo. The sodic-calcic displays Na, Ca, Mo, Mn, Mg, Pb, Zn and Sn enrichment. The iron-rich alteration zones (grunerite-almandine-magnetite) from the northern sector display a Fe, Mg, Ba, V, Ni, Co, Cr, Cu association. The calcic-iron alteration within the southern sector is marked by enrichment in Ca, Fe, V, Ni, Co, Cr, Mn, Mg, Th, P, HREE and Cu. The Fe-V-Ni-Co signature typical of the iron-rich and calcic-iron alteration stages is thus a lithogeochemical footprint of early Neoarchean IOCG mineralization, providing a useful proxy for exploration. Significant amounts of K, Rb, Ba, Al, Si, Nb, Ta, Th, U, Zr, Pb, Zn and Cu are common in potassic-iron alteration zones from Neoarchean deposits in both northern and southern sectors. The Paleoproterozoic IOCG and granite-related deposits are controlled by brittle structures and represent oxidized (muscovite-potassium feldspar-pyrite-hematite-chlorite), low temperature, sulfur-rich (pyrite-rich) and iron-deficient hydrothermal systems. The Paleoproterozoic IOCG deposits display potassic or potassic-iron alteration (potassium feldspar-biotite±magnetite), generally overprinted by chlorite alteration with late chalcopyrite-rich vein/breccia containing calcite-quartz-albite-chlorite-epidote-sericite. The Paleoproterozoic IOCG mineralized zones display enrichment in granitophile elements, defined by Sn-Mo-REE ± W ± Be±Bi±Nb ± Y. The granite-related deposits are marked by chlorite-rich or greisen alteration types characterized by enrichment in K, Sn, W, Mo, and Bi. The ore zones within these deposits are related to the Cu-Au-Mo-W-Sn-Bi-Be-Nb-U-Y signature. The recurrence and superposition of multiple hydrothermal events at a deposit-scale is evidenced by hybrid geochemical signatures, marked by an intermediate composition between the Neoarchean (Fe-V-Ni-Co-Ba-Pb-Zn) and Paleoproterozoic (Sn-W-Mo-Bi) signatures. The results obtained provide insights on the chemical evolution of the Carajás copper systems and demonstrate the influence of the multiple hydrothermal episodes on the geochemical signature of these deposits.

Age and mineralization origin of the Zhongshangou Au deposit, Zhangjiakou goldfield, North China: Constraints from molybdenite Re-Os age and sulfides S-Pb isotopes

The Zhangjiakou goldfield, located in the northern North China Craton (NCC) margin, is a typical gold mineral province in China, containing over 67 gold deposits with 260 t gold reserve. However, gold mineralization age in this district has not been well constrained. Here, we integrate mineral paragenesis, molybdenite Re-Os age and in situ sulfides S and Pb isotopes from the Zhongshangou Te-rich Au deposit to constrain the timing and origin of gold and tellurium mineralization. Molybdenite Re-Os dating yielded a weighted average age of 381.7 ± 2.0 Ma (2σ, MSWD = 0.37, n = 7). Molybdenite has similar δ34S value (-12.9 to −8.5‰, n = 10) to other sulfide minerals (23 pyrite, 2 chalcopyrite and 2 bornite, δ34S = -13.6 to −5.6‰). Lead isotope compositions also show no difference among these sulfide minerals. Considering the mineral paragenesis and S-Pb isotopes, we suggest that molybdenite coprecipitated with gold, tellurides and other types of sulfides from the ore-forming fluids, and that the molybdenite Re-Os data could represent the timing of Zhongshangou gold and tellurium mineralization. New and published age data define a ca. 380 Ma Au-Te mineralization event for the Zhangjiakou goldfield. These Au deposits were genetically associated with the Devonian alkaline magmatism.

Assessing Impacts of Mining-Induced Land Use Changes on Groundwater and Surface Water Quality Using Isotopic and Hydrogeochemical Signatures

The current investigation aimed to assess the impact of land use changes on groundwater quality because of the extensive mining activities in the coal mining province of the Mahan River catchment area, which is located in the Surguja district of Chhattisgarh, India. The water quality index (WQI), Collin’s ratio, stable isotope ratios of water molecules (δ18O and δD), and various physicochemical parameters were measured to determine the suitability of water for domestic purposes. Water samples collected from dug wells, tube wells, river water, and mine water were analyzed, and the results revealed that 28% of the samples were classified as excellent and 44%were classified as good during the pre-monsoon period. In the post-monsoon period, 50% of the samples were categorized as good, while 35% were classified as poor, whereas in mining areas, 54% of samples were found to be unsuitable during the pre-monsoon period, and this increased to 77% in the post-monsoon period. Stable isotope analysis was also conducted: samples were plotted to the right of the Local Meteoric Water Line (LMWL) in the isotope bivariate plot, and the observed slopes for all samples were smaller than that of the LMWL. The enrichment of the δ18O ratio and negative d-excess values at certain locations suggest the occurrence of non-equilibrium processes and mixing mechanisms.

Orogenic gold mineralization in the Huangling region and its intimate tectonic linkage to the Neoproterozoic orogeny of South China

Gold mineralization types were rarely exposed in the Neoproterozoic accretionary-to-collisional orogen, particularly in China, throughout Earth’s history. The Huangling region in South China contains more than 70 gold deposits/occurrences hosted in Archean-Paleoproterozoic metamorphic rocks and Neoproterozoic granitic complexes. However, the absolute age of hydrothermal mineralization, genesis, and their relationship with regional-scale processes, such as tectonism, magmatism, and metamorphism, remains unclear. Therefore, in this study, we investigated three gold deposits (Shuiyuesi, Hongwucun, and Guaizigou) hosted in different lithological units from the northern, central, and southern regions of Huangling, respectively. We conducted detailed fieldwork and analyzed the hydrothermal apatite and monazite geochronology and Sr-Nd isotopic composition of these deposits. The gold mineralization is mainly hosted within sulfide-quartz veinlets, and it is structurally controlled by second-order NW- or NNW-striking faults of the first-order NW trending main fault zone. Gold is present in various forms, such as native gold, electrum, and petzite or in fine-grained pyrite as invisible gold co-precipitated with alteration mineral assemblages that include sericite, quartz, and hydrothermal apatite, and monazite. LA-ICP-MS U-Pb dating of the hydrothermal monazite and apatite for the Shuiyuesi deposit yielded two ages: 831 ± 2 Ma and 830 ± 23 Ma. These ages are consistent with the weighted mean 206Pb/238U age of 834 ± 3 Ma for apatite, obtained from the southern Guaizigou deposit within margin of error. Monazite and apatite dating of the Hongwucun gold deposit yielded younger ages of 810 ± 3 Ma and 800 ± 10 Ma, respectively. The new dates suggest that the gold deposits in the Huangling region underwent two distinct metallogenic episodes of gold mineralization during the Neoproterozoic, coeval with the temporal post-collisional mafic dykes, which postdated the regional metamorphism by ∼100 m.y, as indicated in the Huangling region after the peak period of collisional orogeny and in response to an extensional setting, possibly due to asthenosphere wedging. The Sr-Nd isotope of apatite and monazite (87Sr/86Sr: 0.69555–0.76244, εNd(t): −22.1–−2.9) and collective geochemical data indicate that ore-forming fluids are mainly consistent with magmatic sources with significant contribution from mantle materials. The results of the study suggest that the Huangling gold mineralization province is genetically related to Neoproterozoic post-collisional magmatism. Additionally, the region shares many characteristics of large orogenic gold provinces around the world, including alteration types, element associations, occurrence states of gold, and the evolution of orogenic belts, offering valuable new insights into the gold metallogeny of the early Neoproterozoic period, which is generally not known for its abundance of Au deposits.

Stability Monitoring of Goaf Based on Remote Sensing Image

Large scale mining of coal resources is a major factor causing goaf collapse in China. According to the statistics of 21 major coal mining provinces, the area of coal mining surface subsidence is up to 4.5 billion m2, posing a great threat to the regional ecological environment and people's lives and property. The rapid development of remote sensing technology has changed the traditional field survey method and has become one of the important means of environmental monitoring. Information can be obtained not only by photography, but also by scanning. The amount of information obtained by remote sensing far exceeds that obtained by conventional traditional methods. Based on remote sensing images, this paper studies the stability monitoring of coal mine goaf, establishes a ground pressure monitoring network suitable for the actual situation of the mining area, and carries out long-term effective ground pressure monitoring. Through remote sensing images, we can fully grasp and avoid the hazards of the goaf. Remote sensing technology has the characteristics of wide use, large detection range, and rich information acquisition. It can comprehensively obtain the basic information of the mining area environment, and then monitor the mining area environment.

Changes in the surface water quality of a tropical watershed in the southeastern amazon due to the environmental impacts of artisanal mining

The expansion of areas of human occupation and the increase in economic activity and deforestation are negatively impacting the Amazon ecosystem. Situated in the Carajás Mineral Province in the southeastern Amazon, the Itacaiúnas River Watershed (IRW) encompasses several active mines and has a historical record of intense deforestation primarily linked with the expansion of pasturelands, but also of urban areas, and mining activities. Industrial mining projects are subjected to strict environmental control, but artisanal mining (ASM; ‘garimpos’) sites have not been controlled, despite their known environmental impacts. In recent years, the opening and expansion of ASM in the IRW for the exploitation of mineral resources (Au, Mn, and Cu) have been remarkable. This study presents evidence of anthropogenic impacts, mainly caused by ASM, on the quality and hydrogeochemical characteristics of the IRW surface water. The hydrogeochemical data sets of two projects carried out in the IRW, during 2017 and from 2020 until present, were used to evaluate these impacts within the region. Water quality indices were calculated for the surface water samples. For the whole IRW, water collected during the dry season tended to yield better quality indicators in comparison to those collected during the rainy season. Two sampling sites at Sereno Creek showed very poor water quality and extremely high concentrations of Fe, Al, and potentially toxic elements over time. From 2016 to 2022, ASM sites increased markedly. Moreover, there are indications that Mn exploitation via ASM in Sereno hill is the main source of contamination in the area. New trends of ASM expansion were observed along the main watercourses, related to the exploitation of Au from alluvial deposits. Similar anthropogenic impacts are registered in other regions of the Amazon and environmental monitoring should be encouraged to assess the chemical safety of strategic areas.

The southern IOCG and hydrothermal nickel mineralization trend of the Carajás Mineral Province: Airborne geophysical and remote sensing evidences for structural controls and hydrothermal signature

The iron oxide‑gold‑copper deposit (IOCG) and hydrothermal nickel deposit are globally important targets for mineral exploration due to their notable role in the clean energy transition. The Carajás Mineral Province stands out for having the highest known concentration of world-class IOCG deposits, especially within the regional Canaã shear system, which exerts a critical control in polymetallic deposit distribution. The dense regolith cover and rainforest vegetation hinder the structural mapping and recognition of host rocks and metasomatic facies. In this context, we integrated remote sensing and geological data to evaluate the influence of the structural framework on the IOCG and hydrothermal nickel mineralization location and the metasomatic footprints that envelope these mineral deposits. These deposits are spatially correlated to anomalies that have values greater than the average and standard deviation (⩾ x̄ + sx) of the gamma-spectrometry and geomorphological features (K/eTh, eU/eTh, F-parameter, K and eU deviations, and morpholineament density). The regional control is exerted by NW–SE- and N–S-trending structures, whereas NE–SW- and E–W-oriented shallow structures present the most significant mineralization control at the local scale. Structure intersections express the Carajás deep to the shallow crustal architecture of the region and the potential pathways for the hydrothermal and ore-forming fluids in multiple metallogenetic events.

Unravelling magmatic-hydrothermal processes at Salobo and GT-46 IOCG deposits, Carajás mineral province, Brazil: Constraints from whole-rock geochemistry and trace elements in apatite

The iron oxide-copper-gold (IOCG) deposits of the northern portion of the Carajás Province, Amazonian Craton, Brazil, were primarily formed at the 2.5 Ga IOCG event. These deposits commonly exhibit wide Fe–K hydrothermal alteration halos (i.e., almandine-grunerite-biotite-magnetite) and display a temporal and spatial association with the 2.5 Ga granitic bodies, particularly in the GT-46 and in the world-class Salobo deposit. However, this association still lacks investigation concerning the metallogenic influence of the 2.5 Ga granitic bodies in the IOCG formation. Within these deposits, ca. 2.5 hydrothermally altered granites are recognized and include the Old Salobo, at the Salobo deposit, and G1 and G2, at the GT-46 deposit. Whole-rock geochemistry combined with petrography has pointed out that the G1 and Old Salobo are represented by granites to monzogranites, ferroan, metaluminous to weakly peraluminous with negative Eu anomaly. On the contrary, the G2 granite seems to represent a distinct body with granite composition, ferroan, metaluminous to weakly peraluminous with positive Eu anomaly. This granite exhibit pegmatitic textures, high Sr/Y ratios and listric-shaped normalized REE patterns, which suggest crystallization under high water contents. These granites primarily plots in the field of the volcanic arc granites, though some shifts towards to syn-collisional granites are observed. Effects of hydrothermal alteration are commonly seen in these granites both in textural aspects and geochemistry. Apatite mineral chemistry studies shows that magmatic signature in apatite is preserved in the G2 granite (G2core apatite), Old Salobo granite (OSA) and in the GT-46 ore zone (OZGT-A apatite), represented by enrichment in LREE and negative Eu anomaly. Hydrothermally altered apatite is recognized in the Old Salobo (OSB) and G2 granite (G2rim) and in the ore zone of GT-46 deposit and (OZGT-B) with depletion in LREE, which suggest that the same fluid might have affected both deposits. Truly hydrothermal apatite crystals from the Salobo and GT-46 ore zones shows high (Eu/Eu*)N values, indicative of high oxygen fugacity and alkaline fluids. Strong HREE depletion of the apatite grains from the central zone of the deposits suggest coeval almandine crystallization in the Fe–K alteration halos and evolved hydrothermal fluids. These results indicate that magmatic and hydrothermal process coexist in the IOCG deposits from the northern sector of Carajás Province. This might suggest that the 2.5 Ga IOCG deposits from the Carajás Province can have formed during the development of wide magmatic-hydrothermal systems.