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The first occurrence of cupropearceite in the Kupferschiefer deposit, Lubin mine, SW Poland

Kozub-Budzyń G. A., Piestrzyński A.

Geological Quarterly

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2018

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Vol. 62, No. 2

319--326

EN

Cupropearceite is a sulphosalt belonging to the pearceite-polybasite group, formed due to Cu-for-Ag substitution. It is a rare mineral of the Earth’s crust, described only in four locations so far. This work reports the occurrence of cupropearceite in the upper part of the Weissliegend sandstone from the Cu-Ag deposit in the Fore-Sudetic Monocline. The mineral is associated with stromeyerite, bornite, chalcocite, native silver, silver amalgams and, rarely, pyrite. Formation of cupropearceite is related to fluid activity during low-temperature hydrothermal events responsible for the formation of the Cu-Ag ore mineralization. The identification of cupropearceite is important in terms of constraining minerals bearing associated metals, particularly Ag and As. This work also presents occurrence of this rare mineral in the previously unnoted mineral assemblage mentioned above. The presence of cupropearceite confirms a low-temperature, hydrothermal origin of the Cu-Ag deposit in the Fore-Sudetic Monocline.

2

Charakterystyka geochemiczna minerałów srebra występujących w złożu rud miedzi na monoklinie przedsudeckiej

Kozub-Budzyń G. A., Piestrzyński A.

Biuletyn Państwowego Instytutu Geologicznego

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2017

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nr 468

49--59

PL

Srebro jest najważniejszym pierwiastkiem towarzyszącym w złożu rud miedzi na monoklinie przedsudeckiej. Oprócz minerałów własnych, takich jak srebro rodzime, amalgamaty srebra, stromeyeryt, mackinstryit, jalpait oraz siarczki systemu Cu-Fe-Ag, srebro występuje w postaci podstawień izomorficznych w minerałach miedzi. Głównym celem pracy była charakterystyka geochemiczna minerałów będących nośnikami srebra i korelacja występowania siarczków miedzi wzbogaconych w Ag ze strefami okruszcowania srebrem rodzimym i amalgamatami srebra. Rozmieszczenie Ag w złożu wykazuje wyraźną korelację z występowaniem Cu, a w strefach najbogatszej mineralizacji Cu znajduje się również wysoka zawartość Ag. Wyniki badań przy użyciu skaningowej mikroskopii elektronowej i mikrosondy elektronowej wskazują, że w siarczkach miedzi występuje do kilkunastu % wag. Ag w postaci domieszek diadochowych. Rozmieszczenie Ag w siarczkach miedzi jest silnie zróżnicowane, na co wskazuje znaczna zmienność zawartości Ag w poszczególnych minerałach, w granicach od kilku setnych do kilkunastu procent wagowych.

EN

Silver is the most important associated element in the copper ore deposit of the Fore-Sudetic Monocline. Besides its own minerals, such as native silver, amalgams, stromeyerite, mackinstryite, jalpaite and Cu-Fe-Ag system sulphides, the silver occurs as isomorphic substitutions in copper minerals. The aim of this work included geochemical characterization of Ag-bearing minerals and correlation of the occurrence of Ag-enriched Cu sulphides with the areas of native silver and amalgam mineralization. Distribution of silver in the ore deposit distinctly correlates with Cu concentrations, and the areas of the strongest Cu mineralization are accompanied by high silver concentrations. Results of the scanning electron microscopy and electron microprobe analysis indicate that the Cu sulphides contain up to several wt.% Ag as isomorphic substitutions. Distribution of Ag in Cu sulfides does not show regularity, as demonstrated by wide diversity of Ag contents in various minerals, ranging from 0.0X to dozen wt.% Ag.

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The stability of xenotime in high Ca and Ca-Na systems, under experimental conditions of 250–350°C and 200–400 MPa : the implications for fluid-mediated low-temperature processes in granitic rocks

Budzyń B., Kozub-Budzyń G. A.

Geological Quarterly

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2015

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Vol. 59, No. 2

316–324

EN

he stability of xenotime was tested by experiments in the presence of a silicate mineral assemblage and two different fluids, 2M Ca(OH)2 or Na2Si2O5 + H2O, under P-T conditions of 200-400 MPa and 250-350°C. The xenotime was stable in runs with 2M Ca(OH)2, replicating the low-temperature metasomatic alterations of granitic rocks, except in experiment at 350°C and 400 MPa, where some (Y,REE)-rich fluorapatite formed. Experiments with Na2Si2O5 + H2O resulted in significant xenotime alteration and partial replacement by an unknown (Y,HREE)-rich silicate, and in the formation of minor amounts of (Y,REE)-rich fluorapatite. The latter indicate preferential partitioning of Y and REE into silicates over phosphates during low-temperature, metasomatic processes in a high Na-Ca system, similar to peralkaline granitic rocks.

4

Monazite Th-U-total Pb geochronology and P-T thermodynamic modelling in a revision of the HP-HT metamorphic record in granulites from Stary Gierałtów (NE Orlica-Śnieżnik Dome, SW Poland)

Budzyń B., Jastrzębski M., Kozub-Budzyń G. A., Konečný P.

Geological Quarterly

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2015

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Vol. 59, No. 4

700--717

EN

Thermodynamic modelling and monazite Th-U-total Pb dating via electron microprobe were used to improve the pressure, temperature and timing constraints of the HP-HT metamorphic record in granulites from Stary Gierałtów (NE Orlica-Śnieżnik Dome (OSD), SW Poland). The thermodynamic calculations constrained the P-T conditions to 20-22 kbar and ca. 920ºC in the felsic to intermediate granulites and 20-22 kbar and ca. 970ºC in the mafic granulite. These conditions are considered to closely represent the peak temperatures experienced by these rocks. In the intermediate granulite, the matrix monazite and monazite inclusions in garnet and allanite yielded an age of 349±2.5 Ma. An HP-HT metamorphic event with temperature conditions exceeding 900ºC, which are greater than the closure temperatures of most geochronometers, must have disturbed and completely reset the isotopic systems, including the Th-U-Pb system in the monazite. Consequently, this resetting prevented us from constraining the age of potential earlier metamorphic events or the igneous protolith. The 349±2.5 Ma age reflects the timing of the late-stage HP-HT event and cooling below 900ºC related to the initial exhumation of the granulites. A comparison of the new P-T-t constraints with previous data from the NE Orlica-Śnieżnik Dome indicates that the activation of the channels that exhumed the HP rocks to mid-crustal depths most likely initiated at ca. 350 Ma, and all the metamorphic rocks in the OSD likely shared a common Variscan evolution after ca. 340 Ma.

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Stability of monazite and disturbance of the Th-U-Pb system under experimental conditions of 250–350 °C and 200–400 MPa

Budzyń B., Konečný P., Kozub-Budzyń G. A.

Annales Societatis Geologorum Poloniae

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2015

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Vol. 85, No. 2

405--425

EN

This experimental study provides important data filling the gap in our knowledge on monazite stability under conditions of fluid-mediated low-temperature metamorphic alteration and post-magmatic hydrothermal alterations. The stability of monazite and maintenance of original Th-U-total Pb ages were tested experimentally under P-T conditions of 250–350 °C and 200–400 MPa over 20–40 days. The starting materials included the Burnet monazite + K-feldspar ± albite ± labradorite + muscovite + biotite + SiO2 + CaF2 and 2M Ca(OH)2 or Na2Si2O5 + H2O fluid. In the runs with 2M Ca(OH)2, monazite was unaltered. REE-enriched apatite formed at 350 °C and 400 MPa. The presence of the Na2Si2O5 + H2O fluid promoted the strong alteration of monazite, the formation of secondary REE-enriched apatite to fluorcalciobritholite, and the formation of REE-rich steacyite. Monazite alteration included the newly developed porosity, patchy zoning, and partial replacement by REE-rich steacyite. The unaltered domains of monazite maintained the composition of the Burnet monazite and its age of (or close to) ca. 1072 Ma, while the altered domains showed random dates in the intervals of 375–771 Ma (250 °C, 200 MPa run), 82–253 Ma (350 °C, 200 MPa), and 95–635 Ma (350 °C, 400 MPa). The compositional alteration and disturbance of the Th-U-Pb system resulted from fluid-mediated coupled dissolution-reprecipitation. In nature, such age disturbance in monazite can be attributed to post-magmatic alteration in granitic rocks or to metasomatic alteration during metamorphism. Recognition of potentially altered domains (dark patches in high-contrast BSE-imaging, developed porosity or inclusions of secondary minerals) is crucial to the application of Th-U-Pb geochronology.