Polymetallic Ore District Research Articles

Variscan Sn–W–Mo metallogeny in the gravity picture of the Krušné hory/Erzgebirge granite batholith (Central Europe)

Late Variscan wolframite (±molybdenite) and cassiterite–wolframite greisen, skarn and vein deposits occur in a close spatial association with the granites of the Krušné hory/Erzgebirge batholith (KHEB) in Central Europe. We examined the distribution of the deposits in relation to the gravity field affected by Late Variscan granites using the data from previous gravity and metallogenic studies. Late Variscan granites are differentiated into earlier biotite monzogranites (low-F granites) and later biotite or lithium mica syenogranites (high-F granites) in accordance with the previous classifications. All the outcrops of granites in the KHEB region and their hidden continuation are confined to the Bouguer anomaly contour of −20mGal. The Sn–W–Mo (rare metal) deposits and occurrences are within the gravity contour of −30mGal with the exception of the Grossschirma stratiform tin deposit in the Freiberg polymetallic ore district. We constructed a geological model based on the gravity data along two profiles across the KHEB showing the position of some rare metal deposits and of outcropping and hidden granite bodies. The models show that the overlapping of earlier and later granites is in the areas of the most intense regional gravity minima. These coincide with the Eastern Volcano-Plutonic Complex (Altenberg minimum), which encloses large volumes of felsic extrusives, microgranite dikes and granites, and the Western Plutonic Complex (Eibenstock minimum), with small volumes of felsic dikes and predominance of earlier and later granites, with no extrusives preserved. There is no distinct relationship between the masses of Late Variscan granites and the distribution and the sizes of associated W±Mo and Sn–W deposits. We prefer the idea that rare metal mineralization was formed by hydrothermal fluids derived from outside of presently outcropping granites. It originated in two cycles: one connected with the formation of earlier granites producing W±Mo associations and the other one associated with later granites connected with Sn–W mineralization. Mineralizing fluids were probably generated by mantle–crustal interaction in the crust near the mantle–crust boundary as also indicated by lamprophyric intrusions coeval with the Late Variscan granitic magmatism.

Ore‐forming Geological Conditions and Prospecting Potential in Dahutang W‐Cu Polymetallic Ore District of North Jiangxi, China

Ore‐forming Geological Conditions and Prospecting Potential in Dahutang W‐Cu Polymetallic Ore District of North Jiangxi, China

Fluid inclusion, rare earth element geochemistry, and isotopic characteristics of the eastern ore zone of the Baiyangping polymetallic Ore district, northwestern Yunnan Province, China

The Baiyangping Cu–Ag polymetallic ore district is located in the northern part of the Lanping–Simao foreland fold belt, which lies between the Jinshajiang–Ailaoshan and Lancangjiang faults in western Yunnan Province, China. The source of ore-forming fluids and materials within the eastern ore zone were investigated using fluid inclusion, rare earth element (REE), and isotopic (C, O, and S) analyses undertaken on sulfides, gangue minerals, wall rocks, and ores formed during the hydrothermal stage of mineralization. These analyses indicate: (1) The presence of five types of fluid inclusion, which contain various combinations of liquid (l) and vapor (v) phases at room temperature: (a) H2O (l), (b) H2O (l) + H2O (v), (c) H2O (v), (d) CmHn (v), and (e) H2O (l) + CO2 (l), sometimes with CO2 (v). These inclusions have salinities of 1.4–19.9 wt.% NaCl equivalents, with two modes at approximately 5–10 and 16–21 wt.% NaCl equivalent, and homogenization temperatures between 101°C and 295°C. Five components were identified in fluid inclusions using Raman microspectrometry: H2O, dolomite, calcite, CH4, and N2. (2) Calcite, dolomitized limestone, and dolomite contain total REE concentrations of 3.10–38.93ppm, whereas wall rocks and ores contain REE concentrations of 1.21–196ppm. Dolomitized limestone, dolomite, wall rock, and ore samples have similar chondrite-normalized REE patterns, with ores in the Huachangshan, Xiaquwu, and Dongzhiyan ore blocks having large negative δCe and δEu anomalies, which may be indicative of a change in redox conditions during fluid ascent, migration, and/or cooling. (3) δ34S values for sphalerite, galena, pyrite, and tetrahedrite sulfide samples range from −7.3‰ to 2.1‰, a wide range that indicates multiple sulfur sources. The basin contains numerous sources of S, and deriving S from a mixture of these sources could have yielded these near-zero values, either by mixing of S from different sources, or by changes in the geological conditions of seawater sulfate reduction to sulfur. (4) The C–O isotopic analyses yield δ13C values from ca. zero to −10‰, and a wider range of δ18O values from ca. +6 to +24‰, suggestive of mixing between mantle-derived magma and marine carbonate sources during the evolution of ore-forming fluids, although potential contributions from organic carbon and basinal brine sources should also be considered. These data indicate that ore-forming fluids were derived from a mixture of organism, basinal brine, and mantle-derived magma sources, and as such, the eastern ore zone of the Baiyangping polymetallic ore deposit should be classified as a “Lanping-type” ore deposit.

Ages and geochemistry of Laojunshan granites in southeastern Yunnan, China: implications for W-Sn polymetallic ore deposits

The Southeastern Yunnan region is one of the most important polymetallic ore districts in South China. Located in the southern margin of the South China Block, these ore districts are part of a wider granite-related magmatic-hydrothermal system. Laojunshan granite intrusions, located in the western part of the Southeastern Yunnan, are closely related to W-Sn mineralisation. In this paper we report zircon U-Pb ages, geochemical and petrological characteristics for the ore-related granites in Laojunshan area. Three samples from three intrusive suites of the granitic rocks in Laojunshan intrusion have been analyzed by the LA-ICPMS zircon U-Pb techniques, yielding ages of 86.66 ± 0.42 Ma, 86.72 ± 0.47 Ma and 86.02 ± 0.48 Ma, respectively. Bulk analysis reveals that three intrusive suites are strongly-peraluminous, silica-rich, aluminum-rich and alkali-rich granites and their ACNK values fall mainly into a small range of 1.10–1.38. Moreover, all granites show enriched Rb, La and Zr and depleted Ba, Sr and Ti, as well as a uniformly flat REE-pattern with a marked negative Eu anomaly. The granites and polymetallic W–Sn mineralization possibly both occurred during the Late Coniacian.

Application of the multifractal singular value decomposition for delineating geophysical anomalies associated with molybdenum occurrences in the Luanchuan ore field (China)

Abstract Fractal and multifractal scaling can be found in a wide variety of geological, geochemical and geophysical applications, which provide important clues to underlying processes. In this study, the multifractal singular value decomposition (MSVD) method was used to delineate geophysical anomalies associated with Mo mineralizations based on 1:25,000 scale gravity and magnetic data in the Luanchuan super-large molybdenum polymetallic ore district. The results show that: (1) negative gravity anomalies in the Luanchuan ore field have strong spatial relationships with Jurassic granite porphyry bodies associated with porphyry- and skarn-type Mo mineralizations; (2) the uncertainty linked with identifying gravity and magnetic anomalies' areas is correlated with cutoffs defined in the multifractal models, which can be utilized to recognize potential Mo mineralization at depths ranging from 500 m to 2000 m; and (3) positive magnetic anomalies have weak spatial correlations with Jurassic granite porphyry bodies, but are strongly correlated with gabbro and syenite porphyries associated with Fe mineralization, and with the boundary of Jurassic granite porphyry. Compared to the 3-D Jurassic granite porphyry model and the 2.5-D gravity and magnetic inversion plots of the study area, the gravity and magnetic anomalies identified by means of the MSVD method can be integrated to identify potential Mo targets. This application demonstrates that the MSVD method is convenient, simple, rapid, and direct for delineating geophysical anomalies and for outlining potential exploration targets without processing multiple geological, geophysical, and geochemical datasets from disparate sources.

Deep structure and metallogeny of the Kirovograd polymetallic ore district, the Ukrainian Shield: Correlation of geological and seismic data

The study of deep structure of the Kirovograd ore district proceeds from a broad treatment of its geological boundaries and combination of metasomatic uranium, pegmatitic lithium, and hydrothermal gold deposits, as well as lodes of magmatic titanium ore within these boundaries. The spatial juxtaposition of the Novoukrainsk-Kirovograd granitoid massif and the Korsun-Novomirgorod rapakivi granite-anorthosite massif is a distinguishing feature of the Kirovograd ore district. The former massif along with stratified metamorphic rocks forms an intrusive-ultrametamorphic basement, whereas the latter massif is autonomous with respect to the basement. Taken together, both massifs make up the Novoukrainsk-Korsun-Novomirgorod composite pluton, which determines the architecture of the Kirovograd ore district not only at the present-day erosion surface but also at deeper levels of the lithosphere. The uranium, lithium, and gold deposits are localized in the intrusive-ultrametamorphic basement and controlled by various combinations of intrinsic and superposed structures; the vertical extent of mineralization is also controlled by their combinations. Some combinations are unique. Primarily, these are triple junctions of superposed faults, which host the largest metasomatic uranium orebodies. At the same time, the deposits are spatially related to the local mediumscale trough in topography of the Moho discontinuity. This mantle trench is discordant relative to the Novoukrainsk-Korsun-Novomirgorod pluton. These and other data discussed in the paper allow us to consider the Kirovograd polymetallic ore district as a Paleoproterozoic center of crustal-mantle magmatic activity and ore formation. This center was formed 2.1-1.7 Ga ago in the course of juxtaposition of three development stages differing in associations of intrusive rocks, style of deformation and metamorphism of rocks, origin and localization of ore deposits.

Leogangite, Cu 10 (AsO 4 ) 4 (SO 4 )(OH) 6 ???8H 2 O, a new mineral from the Leogang mining district, Salzburg province, Austria

Leogangite, ideally Cu10(AsO4)4(SO4)(OH)6·8H2O, was found on sample material from mine dumps of the Danielstollen and Inschlagalm in the Schwarzleo valley, both part of the polymetallic ore district of Leogang, Salzburg province, Austria. It is intergrown with olivenite and malachite, all together coating small voids within a tennantite-bearing dolomite breccia, and is assumed to have formed as an alteration product of arsenic-rich fahlore. Associated minerals are tyrolite, parnauite, strashimirite, euchroite, brochantite, langite, posnjakite, and devilline. The new mineral crystallizes with monoclinic symmetry, space group C2/c (no. 15), with a=21.770(7) A, b=12.327(4) A, c=10.720(3) A, β=92.85(1)°, V=2873(2) A3, Z=4, and a calculated density of 3.55 g·cm−3. Leogangite exhibits a thin tabular habit with aggregates of platelets flattened on {100} and elongated along [010], measuring up to 0.1 mm in length, 0.05 mm in width, 0.01 mm in thickness. A perfect cleavage parallel to (100) can be observed. It is transparent, green with a bluish tint, the streak is light green, and it is optically negative with 2V=18(2)°. The refractive indices nx, ny, and nz are 1.590(2), 1.740(2), and 1.744(2), the optical orientation is X=a*, Y=b, Z=c, and the pleochroism is blue-green (X) to pale green (Y, Z). Typical microprobe analyses give (wt%) CuO 49.6–52.9, As2O5 28.5–31.1, SO3 4.9–5.4, which is equivalent to Cu9.94(As0.99Si0.01O4)4(S0.99O4)(OH)6·8.89H2O as the average composition based on 20+3 oxygens. The strongest reflections of the X-ray powder diffraction pattern are (dobs, I/Iobs, hkl): 10.85, 100, (200); 2.630, 60, (\({\it 20}{\bar {\it 4}}\)); 5.44, 50, (400); 3.625, 50, (600); 3.090, 40, (023). The structure of the mineral was refined to R1=0.095 for 1768 unique reflections with \(F^2_{\rm o} > 4\sigma(F^2_{\rm o})\) and is a new representative of the rare [5]-coordinated Cu2+ compounds with edge-sharing CuO5 square pyramids. The main motif consists of [Cu4O14] tetramers. Together with the AsO4 tetrahedra and the remaining CuO5 polyhedron they build complex heteropolyhedral layers parallel to (100), which are linked by the SO4 tetrahedron and parts of the hydrogen bonds along the a-axis, thus forming a complex open framework structure. Chemical, optical and X-ray powder pattern characteristics are the distinguishing features to similar minerals like parnauite, tyrolite, or clinotyrolite.

Fission track evidence on thermal history of Jiama polymetallic ore district, Tibet

Fission track evidence on thermal history of Jiama polymetallic ore district, Tibet

Gold-depleted zone and its metallogenic significance, Yinshan ore field, Jiangxi Province, China

Based on gold analyses of 213 samples of the Shuangqiaoshan Group in an area of 225 km2 with the Yinshan polymetallic ore district as the centre, a depleted zone of gold is recognized around the ore district, suggesting that the Shuangqiaoshan Group may be a source bed for gold. Discussions were given concerning the alteration-mineralization features of the Yinshan deposit, the ore-controlling mechanism of the NE-trending fault zone and promising targets for further ore prospecting.

Analysis of results of lithochemical exploration in metallogenic-prospecting

A truer expression of ore potential of an area, as in the two essentially polymetallic ore districts in Kazakhstan, and a statistically greater probability of discovery of large ore deposits therein are obtainable by a) certain corrections for the landscape-geochemical variables in processing the results of metallometric surveys; b) introduction of the “specific territorial ore potential,” the concept here developed, into pre-estimations of geological reserve of the ore in the given area; c) consideration of geochemical spectra of the mineralization (as in fig. 2). -- V.P. Sokoloff