Search Results (5)

As strategic critical metals, tungsten (W) and tin (Sn) require efficient exploration methods for effective resource development. This study implemented an advanced spread-spectrum induced polarization (SSIP) method in the Xitian mining district of southern China. Through optimized survey system configuration (maximum current electrode spacing of 5200 m, 12-channel acquisition, and five discrete frequency points), we achieved significant advancements: (1) a penetration depth of 1200 m, and (2) three- to five-times higher data acquisition efficiency compared to conventional symmetrical quadrupole arrays. Inversion results of resistivity and chargeability profiles from two parallel survey lines (total length 2.4 km) demonstrated an 85% spatial correlation between resistivity and chargeability anomalies, successfully identifying three mineralized veins. Drill-hole verification confirmed the presence of greisen veins (characterized by low resistivity <100 $\mathrm{\Omega }\cdot \mathrm{m}$ and high chargeability > 3%) and skarn veins (moderate resistivity 150–200 $\mathrm{\Omega }\cdot \mathrm{m}$ and chargeability 1.5–2%). The method exhibits a detection sensitivity of 0.5% chargeability contrast for deep-seated W-Sn polymetallic deposits, providing quantitative technical references for similar deposit exploration. Full article

This article presents data on the composition of biotite from igneous rocks of the Shakhtama complex, which are associated with various types of mineralization in Eastern Transbaikalia: Au-Cu-Fe-skarn, skarn-porphyry, Mo-porphyry, rare-metal–greisen, Au-polymetallic and Au-Bi. The major element and halogen contents were determined by EPMA. The content of trace elements was determined by means of LA-ICP-MS. As a result, the specific traits of the composition of the biotite of igneous rocks associated with specific types of mineralization of the Eastern Transbaikalia were determined. The biotites of rare-metal–greisen deposits are characterized by the maximum content of fluorine (>2 wt. %) and low chlorine content (<0.04 wt. %). In addition, such biotites are characterized by high X_Fe (>0.47). Within Eastern Transbaikalia, igneous rocks developed at the Bystrinsky deposit are potentially ore-bearing for the “classic” porphyry type of mineralization. They have the highest values of IV(F/Cl) (4.9–7.1) and IV(F) (2–2.8) and the lowest values of Log(X_Mg/X_Fe) (0.1–0.4). The trace element composition clearly distinguishes biotites from rare-metal–greisen deposits and is identified by the highest contents (ppm) Ga > 65, Li > 600, Sn > 20, Mn > 2000, Cs > 50, Zn > 600. Biotites of Au-polymetallic and Au-Bi deposits occupy an average position between rare-metal–greisen and Mo-porphyry ones. Biotites of Mo-porphyry deposits differ in minimum values (ppm) of Sn < 3, Zn < 160, and low values of Li (150–290), V (290–440), and Ga (39–48). In general, the chemical composition of biotites shows that the degree of igneous rock fractionation of deposits increases in the series: porphyry–skarn–polymetallic–rare-metal. Full article

The paper reports the results of studies on critical metal mineralization genetically related to the late-stage intrusions of Salmi anorthosite-rapakivi granite batholith (SARGB) in the Riphean age. In, Bi, and Be mineralization in skarn-greisen deposits and occurrences at the SARGB endocontact, as well as REE and Nb-Ta mineralization in Li-F granites, understood as the late intrusive phases of the batholith, were studied. It is the first report on columbite-group minerals, as well as REE-Ta-Nb and REE mineralization in SARGB granites. Optical and scanning electron microscopy, EDS and LA ICP MS microanalysis, X-ray fluorescence spectrometry, Raman spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS) were used. The data obtained show that roquesite formation was mainly triggered by the decay of In-bearing solid sphalerite and chalcopyrite solutions. Zavaritskite, associated with unoxidized sulphides, was derived hypogenically and seldom occurs in ores. A helvine-group mineral association with zinc-enriched spinel (ZnO 22%–25%) seems to have been one of the factors preventing genthelvite formation. The Muzilampi, Hepaoja and Avtodor ore occurrences in Li-F granites display similar REE and Nb-Ta mineralization. They are associated with Y-fluorite and Li-siderophyllite, which contain exceptionally high Nb concentrations (0.25%–0.78%) in Muzilampi granites. Additionally, fluorite-1 is commonly overfilled (to >50%) with micron-sized synchisite and parisite inclusions. Columbite-tantalite-group minerals, present at all the occurrences studied, occur solely as ferricolumbites with a dominant Mn/(Mn + Fe) ratio of <0.2. Biotite and Li-siderophyllite, associated with columbite, have an extremely high iron index Fe/(Fe + Mg) > 0.9 approaching the maximum values (~1.0) in the most differentiated granites. Full article

The results of the study of rare-metal (Bi, Te, Se. Be, In) mineralization of skarn deposits (Sn, Zn) in the Pitkäranta Mining District, genetically related to the Salmi anorthosite-rapakivi granite batholiths of Early Riphean age are reported. Minerals and their chemical composition were identified on the base of optical microscopy as well as electron microanalysis. The diversity of rare-metal ore mineralization (native metals, oxides, and hydroxides, carbonates, tellurides, selenides, sulfides, sulphosalts, borates, and silicates) in Pitkäranta Mining District ores is indicative of considerable variations in the physicochemical conditions of their formation controlled by the discrete-pulse-like supply of fluids. Bismuth, wittichenite, and matildite are the most common rare-metal minerals. Sulfosalts of the bismuthinite-aikinite series are represented only by its end-members. The absence of solid solution exsolution structures in sulfobismuthides suggests that they crystallized from hydrothermal solutions at low temperatures. Be (>10 minerals) and In (roquesite) minerals occur mainly in aposkarn greisens. Roquesite in Pitkäranta Mining District ores formed upon greisen alteration of skarns with In released upon the alteration of In-bearing solid sphalerite (Cu¹⁺ In³⁺) ↔ (Zn²⁺, Fe²⁺) and chalcopyrite In³⁺ ↔ Fe³⁺ and 2Fe³⁺ ↔ (Fe²⁺, Zn²⁺) Sn⁴⁺ solutions. Sphalerite with an average In concentration of 2001 ppm, is a major In-bearing mineral in the ores. Full article

Abundant fluorites occur in the Shihuiyao rare metal (Nb-Ta-Rb) deposit in Inner Mongolia of NE China, and they can be classified by their occurrence into three types. Type I occurs disseminated in greisen pockets of albitized granite. Type II occurs in the skarn zone between granite and carbonate host rocks, and it can be subdivided into different subtypes according to color, namely dark purple (II-D), magenta (II-M), green (II-G), light purple (II-P), and white (II-W). Type III are the fluorite-bearing veins in the silty mudstones. On the basis of petrography of the fluorites and their high contents of HFSEs (high field strength elements) and LILEs (large ion lithophile elements), strong negative Eu anomalies, and tetrad effects, we suggest that Type I fluorites crystallized in a late-magmatic stage with all the components derived from the granite. The high Y/Ho ratios suggest that the Type II fluorites crystallized in the early- or late-hydrothermal stage. The rare earth elements (REEs) characterized by various Eu anomalies of the Type II fluorites indicate a mixed origin for ore-forming metals from granite-related fluids and limestones, and the oxygen fugacity increased during fluid migration and cooling. Compared to the Type II fluorites, the similar trace element contents of the Type III suggest a similar origin, and remarkable positive Eu anomalies represent a more oxidizing environment. The Sr isotopic composition (⁸⁷Sr/⁸⁶Sr)_i = 0.710861) of the Type I fluorites may represent that of the granite-derived fluids, whereas the (⁸⁷Sr/⁸⁶Sr)_i ratios of the Type II (0.710168–0.710380) and Type III (0.709018) fluorites are lower than that of the Type I fluorites but higher than those of the Late Permian-Early Triassic seawater, suggesting a binary mixed Sr source, i.e., granite-derived fluids and marine limestones. Nevertheless, the proportion of limestone-derived Sr in the mixture forming the Type III fluorites is much higher than that of Type II. The rare metal Nb and Ta get into the granite-derived F-rich fluids by complexing with F and precipitate in the form of columbite-group minerals after the Type I fluorites crystallize. Most of Nb and Ta may have deposited as columbite-group minerals during the magmatic stage, resulting in no Nb-Ta mineralization in the hydrothermal stage when the Type II and III fluorites formed. Hence, the Type I fluorites in the Shihuiyao mining area can be used as an important exploration tool for the Nb-Ta mineralization. Full article