scholarly journals Spatial and Temporal Evolution of the Freiberg Epithermal Ag-Pb-Zn District, Germany

2021 ◽  
Author(s):  
Laura J. Swinkels ◽  
Jan Schulz-Isenbeck ◽  
Max Frenzel ◽  
Jens Gutzmer ◽  
Mathias Burisch
Keyword(s):  
Fluid Inclusion ◽  
Metal Sulfide ◽  
High Grade ◽  
Geochemical Zoning ◽  
Fluid Systems ◽  
Mineral Associations ◽  
Temporal And Spatial ◽  
Homogenization Temperatures ◽  
Geochemical Analyses ◽  
Systematic Collection

Abstract The Freiberg district hosts one of the largest series of epithermal polymetallic vein deposits in Europe. The availability of a systematic collection of historical samples provides an excellent opportunity to study the anatomy of these epithermal systems. Detailed petrographic investigations, geochemical analyses, and fluid inclusion studies were conducted on several vertical profiles within the Freiberg district to decipher mineralogical and geochemical zoning patterns. Six distinctive mineral associations have been recognized within the Freiberg epithermal veins; sphalerite-pyrite-quartz and galena-quartz±carbonate associations are most abundant in the central sector, as well as in the deepest sections of veins on the periphery of the district. A high-grade sphalerite-Ag-sulfides-carbonate association occurs laterally between the central and peripheral sectors and at intermediate depth in veins on the periphery. Shallow and peripheral zones are dominated by an exceptionally Ag-rich Ag-sulfides-quartz association, whereas the shallowest veins locally comprise Ag-poor stibnite-quartz and quartz-carbonate associations. Fluid inclusion assemblages returned low salinities (<6.0 wt % NaCl equiv), and homogenization temperatures successively decrease from ~320°C associated with the proximal and deep sphalerite-pyrite-quartz association, to ~170°C related to the distal and shallow Ag-sulfides-quartz association. The architecture of the Freiberg district is related to the temporal and spatial evolution of magmatic-hydrothermal fluid systems, including boiling and concomitant cooling, as well as CO2 loss. Constraints on the paleodepth indicate that the veins formed between 200 and 1,800 m below the paleowater table. High-grade Ag ore occurs over a vertical interval of at least 500 m and is bracketed by shallower stibnite-quartz and barren quartz, and deeper base metal-sulfide-quartz zones.

Spatiotemporal zonation of the Freiberg Ag-Pb-Zn-(Cu) epithermal system

2021 ◽  
Author(s):  
Laura Swinkels ◽  
Jan Schulz-Isenbeck ◽  
Max Frenzel ◽  
Jens Gutzmer ◽  
Mathias Burisch
Keyword(s):  
Ground Level ◽  
Homogenization Temperature ◽  
Hydrothermal Activity ◽  
Silver Deposition ◽  
Geochemical Zoning ◽  
Metallogenic Model ◽  
Vertical Vein ◽  
Mineral Associations ◽  
Geochemical Analyses ◽  
Volatile Loss

<p>The Freiberg district, located in the eastern part of the Erzgebirge, Germany, hosts one of the largest series of epithermal polymetallic vein deposits in Europe. The present study aims to decipher mineralogical and geochemical zoning on the vein- and district-scale and to constrain the underlying ore-forming processes. Detailed petrographic investigations, geochemical analyses and fluid inclusion studies are carried out on several vertical vein profiles within the Freiberg district in order to develop a district-scale metallogenic model. Five different mineral associations related to Permian magmatic-hydrothermal activity have been recognized within the Freiberg epithermal vein system exhibiting a distinct district-scale and vein-scale zonation. The central part of the Freiberg district is dominated by sphalerite-pyrite-quartz and galena-quartz±carbonate associations with a mean silver grade of 769 g/t (n=65). Similar base metal-rich assemblages also predominate the deepest vein intersections (>300 m below ground level) in the peripheral sectors of the Freiberg District. Vein infill at intermediate depth and peripheral positions in the district is, in contrast, dominated by a sphalerite-Ag-sulfides-carbonate association. This association is marked by an abundance of carbonate gangue and significantly higher silver grades (mean = 4800 g/t; n=25). Veins in the shallowest and most peripheral parts (depth <150 m b.g.l.) of the Freiberg district are dominated by a Ag-sulfide-quartz association with a mean Ag concentration of 4900 g/t (n= 56). Silver is mainly hosted by sulfosalts and fahlore but significant concentrations may also be associated to Ag-sulfide inclusions in galena. Even shallower, the veins comprise a stibnite-quartz association with distinctly low Ag contents (410 g/t Ag, n=4). Fluid inclusions related to the various associations yield consistent salinities in the range of 0.1 to 6.0 % eq. w(NaCl). The homogenization temperature, however, progressively decreases from about 320°C for quartz associated with proximal sphalerite-pyrite-quartz mineralization, down to ~170°C for quartz related to distal Ag-sulfide-quartz association. The general formation of the Freiberg epithermal veins is related to the continuous evolution of a magmatic-hydrothermal system in time and space. Silver deposition is most likely triggered by boiling and associated cooling and volatile-loss, which results in a distinct carbonate horizon (typically at ~500 m depth b.g.l. for peripheral parts) with significantly elevated Ag grades (sphalerite-Ag-sulfides-carbonate association).</p>

scholarly journals Precious Metal Enrichment at the Myra Falls VMS Deposit, British Columbia, Canada

Geosciences ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 422
Author(s):  
Daniel Marshall ◽  
Carol-Anne Nicol ◽  
Robert Greene ◽  
Rick Sawyer ◽  
Armond Stansell ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Precious Metal ◽  
Metal Enrichment ◽  
Sea Floor ◽  
North West ◽  
Low Salinity ◽  
Volcanogenic Massive Sulphide ◽  
Igneous Fluids ◽  
Homogenization Temperatures ◽  
Water Depths

Gold, present as electrum, in the Battle Gap, Ridge North-West, HW, and Price deposits at the Myra Falls mine, occurs in late veinlets cutting the earlier volcanogenic massive sulphide (VMS) lithologies. The ore mineral assemblage containing the electrum comprises dominantly galena, tennantite, bornite, sphalerite, chalcopyrite, pyrite, and rarely stromeyerite, and is defined as an Au-Zn-Pb-As-Sb association. The gangue is comprised of barite, quartz, and minor feldspathic volcanogenic sedimentary rocks and clay, comprised predominantly of kaolinite with subordinate illite. The deposition of gold as electrum in the baritic upper portions of the sulphide lenses occurs at relatively shallow water depths beneath the sea floor. Primary, pseudosecondary, and secondary fluid inclusions, petrographically related to gold, show boiling fluid inclusion assemblages in the range of 123 to 173 °C, with compositions and eutectic melt temperatures consistent with seawater at approximately 3.2 wt % NaCl equivalent. The fluid inclusion homogenization temperatures are consistent with boiling seawater corresponding to water depths ranging from 15 to 125 m. Slightly more dilute brines corresponding to salinities of approximately 1 wt % NaCl indicate that there is input from very low-salinity brines, which could represent a transition from subaqueous VMS to epithermal-like conditions for precious metal enrichment, mixing with re-condensed vapor, or very low-salinity igneous fluids.

scholarly journals Fluid Inclusion and Oxygen Isotope Constraints on the Origin and Hydrothermal Evolution of the Haisugou Porphyry Mo Deposit in the Northern Xilamulun District, NE China

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Qihai Shu ◽  
Yong Lai
Keyword(s):  
Fluid Inclusion ◽  
Meteoric Water ◽  
Early Time ◽  
Low Oxygen ◽  
Potassic Alteration ◽  
Low Salinity ◽  
Oxygen Isotopic ◽  
Homogenization Temperatures ◽  
Porphyry Mo Deposit ◽  
Positive Correlations

The Haisugou porphyry Mo deposit is located in the northern Xilamulun district, northeastern China. Based on alteration and mineralization styles and crosscutting relationships, the hydrothermal evolution in Haisugou can be divided into three stages: an early potassic alteration stage with no significant metal deposition, a synmineralization sericite-chlorite alteration stage with extensive Mo precipitation, and a postmineralization stage characterized by barren quartz and minor calcite and fluorite. The coexistence of high-salinity brine inclusions with low-salinity inclusions both in potassic alteration stage (~440°C) and locally in the early time of mineralization stage (380–320°C) indicates the occurrence of fluid boiling. The positive correlations between the homogenization temperatures and the salinities of the fluids and the low oxygen isotopic compositions (δ18Ofluid < 3‰) of the syn- to postmineralization quartz together suggest the mixing of magmatic fluids with meteoric water, which dominated the whole mineralization process. The early boiling fluids were not responsible for ore precipitation, whereas the mixing with meteoric water, which resulted in temperature decrease and dilution that significantly reduced the metal solubility, should have played the major role in Mo mineralization. Combined fluid inclusion microthermometry and chlorite geothermometer results reveal that ore deposition mainly occurred between 350 and 290°C in Haisugou.

scholarly journals Diagenetic Pore Fluid Evolution and Dolomitization of the Silurian and Devonian Carbonates, Huron Domain of Southwestern Ontario: Petrographic, Geochemical and Fluid Inclusion Evidence

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 140 ◽  
Author(s):  
Marco Tortola ◽  
Ihsan S. Al-Aasm ◽  
Richard Crowe
Keyword(s):  
Fluid Inclusion ◽  
Isotopic Composition ◽  
Age Groups ◽  
Fluid Composition ◽  
Fluid System ◽  
Negative Shift ◽  
Fluid Systems ◽  
Saddle Dolomite ◽  
Deep Boreholes ◽  
Diagenetic Fluid

Core samples from two deep boreholes were analyzed for petrographic, stable and Sr isotopes, fluid inclusion microthermometry and major, minor, trace and rare-earth elements (REE) of different types of dolomite in the Silurian and Devonian carbonates of the eastern side of the Michigan Basin provided useful insights into the nature of dolomitization, and the evolution of diagenetic pore fluids in this part of the basin. Petrographic features show that both age groups are characterized by the presence of a pervasive replacive fine-crystalline (<50 µm) dolomite matrix (RD1) and pervasive and selective replacive medium crystalline (>50–100 µm) dolomite matrix (RD2 and RD3, respectively). In addition to these types, a coarse crystalline (>500 µm) saddle dolomite cement (SD) filling fractures and vugs is observed only in the Silurian rocks. Results from geochemical and fluid inclusion analyses indicate that the diagenesis of Silurian and Devonian formations show variations in terms of the evolution of the diagenetic fluid composition. These fluid systems are: (1) a diagenetic fluid system that affected Silurian carbonates and was altered by salt dissolution post-Silurian time. These carbonates show a negative shift in δ18O values (dolomite δ18O average: −6.72‰ VPDB), Sr isotopic composition slightly more radiogenic than coeval seawater (0.7078–0.7087), high temperatures (RD2 and SD dolomite Th average: 110 °C) and hypersaline signature (RD2 and SD dolomite average salinity: 26.8 wt.% NaCl eq.); and (2) a diagenetic fluid system that affected Devonian carbonates, possibly occurred during the Alleghenian orogeny in Carboniferous time and characterized by a less pronounced negative shift in δ18O values (dolomite δ18O average: −5.74‰ VPDB), Sr isotopic composition in range with the postulated values for coeval seawater (0.7078–0.7080), lower temperatures (RD2 dolomite Th average: 83 °C) and less saline signature (RD2 dolomite average salinity: 20.8 wt.% NaCl eq.).

Clumped isotope geothermometry of an Ordovician carbonate mound, Hudson Bay Basin

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-102
Author(s):  
Josué J. Jautzy ◽  
Martine M. Savard ◽  
Denis Lavoie ◽  
Omid H. Ardakani ◽  
Ryan S. Dhillon ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Oil And Gas ◽  
Fission Track ◽  
Hudson Bay ◽  
Apatite Fission Track ◽  
Burial Diagenesis ◽  
Carbonate Mound ◽  
History Of ◽  
Homogenization Temperatures ◽  
Clumped Isotope

The Hudson Bay sedimentary basin was overlooked geologically until two decades ago. Recent efforts to understand the palaeogeothermal history of this basin have led to the evaluation of fluid inclusion microthermometry, apatite fission track, organic matter reflectance and Rock–Eval analyses. Although apatite fission track and organic maturity indicators tend to show relatively low maximum burial temperatures (60–80°C), evidence of potential oil slicks on the sea surface and oil and gas shows in offshore wells have been reported across Hudson Bay. Fluid inclusion microthermometry in a carbonate mound sequence suggests homogenization temperatures of 118 ± 25 and 93 ± 10°C for recrystallized synsedimentary marine calcite and late pore-filling burial calcite, respectively. This sequence provides an interesting geological framework to test the application of clumped isotope thermometry against independent geothermometers. Here, we present clumped isotope data acquired on the late calcite cements and diagenetically altered early marine phases. The integration of clumped isotopic data with other thermal indicators allows the reconstruction and refinement of the thermal–diagenetic history of these carbonates by confirming an episode of heating, probably of hydrothermal origin and prior to normal burial diagenesis, that reset both fluid inclusions and the clumped isotope indicators without recrystallization.

Genesis of the Pb–Zn deposit at Sant’Antonio di Val D’Aspra, Southern Tuscany (Italy): disparity between geo-petrographic data and fluid inclusion microthermometry

1990 ◽  
Vol 54 (375) ◽  
pp. 289-294 ◽  
Author(s):  
M. Giamello ◽  
F. Riccobono ◽  
G. Sabatini
Keyword(s):  
Fluid Inclusion ◽  
Carbonate Rocks ◽  
Fluid Inclusion Study ◽  
Mississippi Valley ◽  
Ore Minerals ◽  
Inclusion Study ◽  
History Of ◽  
Homogenization Temperatures ◽  
The One ◽  
Internal Sediments

AbstractThe Pb–Zn deposit at Sant'Antonio di Val d'Aspra in the Farma Valley (Southern Tuscany) is hosted by Lower Moscovian carbonate rocks and shows many characters commonly found in Mississippi Valley type (MVT) deposits. Ore minerals (essentially sphalerite and galena) are closely confined to dolomitized portions of an only partly preserved black limestone. Mineralized carbonate rocks appear to have been eroded before the deposition of the overlying Upper Moscovian (Late Podolskian) shales. The diffuse presence of structures frequently found in internal sediments of karstic cavities indicates that supergene mechanisms have played an important role in the history of the deposit. A fluid inclusion study carried out on ore and gangue minerals revealed the presence of two different types of inclusions. The homogenization temperatures ranged from 120°C to 225°C but the most frequently found values were around 170°C. Salinity ranged from moderately low values up to 20 eq. wt. % NaCl. Lead isotopic composition rules out any relationship between the Sant'Antonio mineralization and Tertiary hydrothermal base metal occurrences in the same area. When all the data are taken together, a contrast is evident between geo-petrographic and isotopic data on the one hand, and fluid-inclusion microthermometry on the other.

scholarly journals Formation Mechanism of the Velyka Vyska Syenite Massif (Korsun-Novomyrhorod Pluton, Ukrainian Shield) Derived from Melt Inclusions in Zircon

2021 ◽  
Vol 43 (1) ◽  
pp. 3-15
Author(s):  
D.K. VOZNYAK ◽  
E.V. ., LEVASHOVA ◽  
S.G. SKUBLOV ◽  
S.G. KRYVDIK ◽  
O.A. VYSHNEVSKYI ◽  
...  
Keyword(s):  
High Pressure ◽  
Melt Inclusions ◽  
Ore Deposits ◽  
Partial Replacement ◽  
Type I ◽  
High Grade ◽  
Ree Distribution ◽  
The Matrix ◽  
Homogenization Temperatures ◽  
Primary Melt

The formation of leucosyenites in the Velyka Vyska syenite massif was provoked by the liquation layering of magmatic melt. This assumption is based on the presence of two primary melt inclusions of different chemical composition in zircon crystals from Velyka Vyska leucosyenites. They correspond to two types of silicate melts. Type I is a leucosyenite type that contains high SiO2 concentrations (these inclusions dominate quantitatively); type II is a melanosyenite type that contains elevated Fe and smaller SiO2 concentrations. The liquation layering of magmatic melt was slow because the liquates are similar in density; leucosyenite melt, which is more abundant than melt of melanosyenite composition, displays greater dynamic viscosity; the initial sizes of embryos of melanosyenite composition are microscopic. Sulphide melt, similar in composition to pyrrhotite, was also involved in the formation of the massif. Zircon was crystallized at temperatures over 1300°С, as indicated by the homogenization temperatures of primary melt inclusions. The REE distribution spectra of the main parts (or zones,) of zircon crystals from the Velyka Vyska massif are identical to those of zircon from the Azov and Yastrubets syenite massifs with which high-grade Zr and REE (Azov and Yastrubets) ore deposits are associated. They are characteristic of magmatically generated zircon. Some of the grains analyzed contain rims that are contrasting against the matrix of a crystal, look dark-grey in the BSE image and display flattened REE distribution spectra. Such spectra are also typical of baddeleyite, which formed by the partial replacement of zircon crystals. The formation of a dark-grey rim in zircon and baddeleyite is attributed to the strong effect of high-pressure СО2-fluid on the rock. The formation patterns of the Velyka Vyska and Azov massifs exhibit some common features: (а) silicate melt liquation; (b) high ZrO2 concentrations in glasses from hardened primary melt inclusions; (c) the supply of high-pressure СО2-fluid flows into Velyka Vyska and Azov hard rocks. Similar conditions of formation suggest the occurrence of high-grade Zr and REE ores in the Velyka Vyska syenite massif.

The Lavrion Pb-Zn-Ag–Rich Vein and Breccia Detachment-Related Deposits (Greece): Involvement of Evaporated Seawater and Meteoric Fluids During Postorogenic Exhumation

2019 ◽  
Vol 114 (7) ◽  
pp. 1415-1442 ◽  
Author(s):  
Christophe Scheffer ◽  
Alexandre Tarantola ◽  
Olivier Vanderhaeghe ◽  
Panagiotis Voudouris ◽  
Paul G. Spry ◽  
...  
Keyword(s):  
High Temperature ◽  
Fluid Inclusions ◽  
Meteoric Water ◽  
Ore Deposits ◽  
Metal Sulfides ◽  
Low Grade ◽  
High Grade ◽  
Base Metal Sulfides ◽  
Wide Range ◽  
Homogenization Temperatures

Abstract The formation of ore deposits in the Lavrion Pb-Zn-Ag district was associated with Miocene detachment that accommodated orogenic collapse and exhumation of high-grade nappes across the ductile-brittle transition. This district consists of (1) low-grade porphyry Mo style, (2) Cu-Fe skarn, (3) high-temperature carbonate replacement Pb-Zn-Ag, and (4) vein and breccia Pb-Zn-Ag mineralization. The vein and breccia mineralization locally contains high-grade silver in base metal sulfides that are cemented by fluorite and carbonate gangue. The rare earth element contents of these gangue minerals, chondrite-normalized patterns, and fluid inclusion studies suggest that they precipitated from a low-temperature hydrothermal fluid. Primary and pseudosecondary fluid inclusions in fluorite and calcite are characterized by a wide range of homogenization temperatures (92°–207°C) and salinities of up to 17.1 wt % NaCl equiv. Secondary fluid inclusions only represent <5 vol % of the total fluid trapped. Fluids extracted from inclusions in fluorite have values of δD = –82.1 to –47.7‰ (Vienna-standard mean ocean water [V-SMOW]) and δ18O = –10.4 to –5.1‰ (V-SMOW). These data and low ratios of Cl/Br measured by crush-leach analyses for fluids in fluorite (102–315) and calcite (162–188) are compatible with the ore fluid being the result of mixing of meteoric water with evaporated seawater. These data suggest that fluids leading to the deposition of late Pb-Zn-Ag–rich vein- and breccia-style mineralization in Lavrion were related to circulation of mixed evaporated seawater and meteoric fluids that was enhanced by brittle deformation. This contrasts with the fluids of magmatic origin related to the formation of low-grade porphyry Mo, Cu-Fe skarn, and high-temperature carbonate replacement deposits spatially related to the Plaka granodiorite.

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