Geology and genesis of Variscan porphyry-style gold mineralization, Petr�?kova hora deposit, Bohemian Massif, Czech Republic

Zachariáš, Jiří; Pertold, Zdeněk; Pudilová, Marta; Žák, Karel; Pertoldová, Jaroslava; Stein, Holly J.; Markey, Richard J.

doi:10.1007/s001260100187

Cited by 48 publications

(23 citation statements)

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“…This could have resulted either from direct input of magmatic fluids into the hydrothermal-external fluid phase (as supported by fluid inclusion data, Zachariáš et al 2001), or from a low water/rock ratio. Finally, the (Leake et al 1997) of hornblende of various origins.…”

Section: Magmatic Vs Hydrothermal Biotite and Amphibolementioning

confidence: 95%

“…The mineralization is hosted largely by composite granodiorite stock and extends to the surrounding Lower Cambrian siliciclastic metasediments. The geology, mineralogy, fluid composition and evolution as well as genetic model of the PH deposit were described in detail by Studničný et al (1987Studničný et al ( , 1994, Studničná and Studničný (1995), Studničná and Zachariáš (1996) with Zachariáš et al (2001).…”

Section: Geological Settingmentioning

confidence: 99%

“…The PH granodiorite stock consists of the central (younger) and the peripheral (older) magmatic facies (Zachariáš et al 2001). Frequent subvertical dykes of two subgroups of granodiorite porphyry are older than the granodiorite, while that of leucocratic granodiorite and aplite are younger.…”

Section: Geological Settingmentioning

confidence: 99%

“…The gold content is highest in the Q 2 veins (up to 70 g/t Au) and decreases to the Q 4 and Q 5 veins (~5 g/t Au). The description of paragenetic relationships among gangue and ore minerals can be found in Zachariáš et al (2001). Quartz veins are usually devoid of visible attendant hydrothermal alteration, except for Q 1 veins that are bordered by K-feldspar rich assemblage (up to 20 mm thick).…”

Section: Geological Settingmentioning

confidence: 99%

“…Multiple evidence for intimate relationships between the mineralization and the granitic system was described by Zachariáš et al (2001) and includes: i) the spatial distribution of the mineralization; ii) the high temperature nature of gold-bearing quartz veins (590-400 °C); iii) the presence of relics of supposed magmatic fluids both in the granodiorite K-feldspar phenocrysts and in the quartz veins; iv) the absence of lower temperature hydrothermal alteration envelopes around the veins and the presence of high-temperature alterations resembling those typical for porphyry systems; and v) the very similar age of the mineralization (348-344 Ma) and of the host granodiorite (348 Ma). Deposit classification, however, is not unequivocal; the mineralization shares signs of both intrusion-related (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Compositional trends in magmatic and hydrothermal silicates of the Petráčkova hora intrusive complex, Bohemian Massif - link between the magmatic processes and intrusion-related gold mineralization

Zachariáš

2012

J. Geosci.

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Mineralized zones of the Variscan (348-344 Ma) Petráčkova hora gold deposit locally exhibit high-temperature (~600 to ~500 °C) hydrothermal alterations: K-alteration-1 (selectively pervasive) and K-alteration-2 (fracture-related) in the granodiorite and granodiorite porphyries, and silicification-1 and -2 in the country rocks (biotite hornfels and feldspathic quartzite). Alteration processes led to partial recrystallization of primary magmatic silicates, and to crystallization of new hydrothermal phases (K-feldspar, biotite and hornblende). Electron microprobe analyses were used to trace magmatic to hydrothermal evolution of the mineral chemistry. The K-feldspar phenocrysts in the granodiorite and granodiorite porphyry exhibit complex magmatic crystallization and resorption textures. Compositionally, K-feldspars differ especially in the barium admixture. It decreases from early (5-0.8 % celsian or 2.6-0.4 wt. % BaO; phenocrysts) to late magmatic (1.1-0 % celsian; groundmass) and hydrothermal (1.2-0 % celsian) K-feldspars. No significant differences were found between the chemistry of magmatic and early hydrothermal amphiboles. They all correspond to magnesiohornblende or actinolite. Tetrahedral silica (Si IV ) ranges from 6.7 to 7.8 atoms per formula unit, however; values greater than 7.2 are the most common. They exhibit positive Si IV -Mg/(Mg + Fe 2+ ) correlation. Late hydrothermal amphibole associated with silicification-2 is also magnesiohornblende; however, it exhibits negative Si IV -Mg/(Mg + Fe 2+ ) trend. Differences in the biotite composition are less pronounced in comparison to amphiboles and comprise especially a decrease in the Ti content and an increase in the Mg/(Mg + Fe 2+ ) ratio from the magmatic to the hydrothermal biotites. Some of the fine-grained biotite aggregates (recrystallized magmatic or hydrothermal biotite) are depleted in potassium, probably due to alteration demonstrated by the presence of submicroscopic intergrowths with clay/chlorite minerals (unrecognizable in back-scattered electron mode). Broad similarities in the chemistry of magmatic and early hydrothermal silicate minerals support the high-temperature nature of the early hydrothermal stage, and point to probable admixture of exsolved magmatic fluid phase in the early hydrothermal fluids.

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Section: Magmatic Vs Hydrothermal Biotite and Amphibolementioning

confidence: 95%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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