scholarly journals Rhenium - rich molybdenites in Thracian porphyry Mo±Cu occurrences, NE - Greece

2001 ◽  
Vol 34 (3) ◽  
pp. 1015 ◽  
Author(s):  
Β. ΜΕΛΦΟΣ ◽  
Π. ΒΟΥΔΟΥΡΗΣ ◽  
Κ. ΑΡΙΚΑΣ ◽  
Μ. ΒΑΒΕΛΙΔΗΣ
Keyword(s):  
Chemical Composition ◽  
Hydrothermal Alteration ◽  
Fluid Inclusions ◽  
Mineral Chemistry ◽  
Rare Element ◽  
Alteration Zones ◽  
Porphyry Cu ◽  
Mineral Assemblages ◽  
Host Rocks

The present study correlates both the mineralogy of the hydrothermal alteration and the mineral chemistry of molybdenites from three porphyry Mo ± Cu occurrences in Thrace: Melitena, Pagoni Rachi/Kirki and Ktismata/ Maronia. The mineralisations are genetically related to calcalkaline, subvolcanic bodies of Tertiary age. According to their mineralogical and chemical composition the host rocks are characterized as dacite (Melitena), dacitic andésite (Pagoni Rachi) and porphyry microgranite (Ktismata/Maronia). The molybdenites occur in disseminated form, as fracture fillings, as well within quartz stockworks crosscuting the central alteration zones of the intrusives. They are accompanied by the following mineral assemblages: quartz, sericite, pyrophyllite, diaspore, Ca-Ba-rich alunite, pyrite (Melitena); quartz, albite/K-feldspar, biotite, actinolite, magnetite (Pagoni Rachi); and sericite, kaolinite, pyrophyllite, chlorite (Ktismata). Preliminary microthermometric results showed homogenisation temperatures from 352° to 390 °C for Pagoni Rachi area and from 295° to 363 °C for Melitena area. The salinities range between 4.5 and 6.1 wt% eq. NaCl and between 2.7 and 3.4 wt% eq. NaCl, respectively. Detailed study on over 400 fluid inclusions from the porphyry Cu-Mo deposit in Maronia area revealed formation temperatures from 300° to 420 °C, whereas salinities are distincted in two different groups from 6 to 16 wt% eq. NaCl and from 28 to 55 wt% eq. NaCl. The chemical composition of the molybdenites from the three porphyry Mo±Cu deposits in Thrace was studied with 155 microprobe analyses. The results revealed unusual high and variable Re concentrations in the studied molybdenites. Re content in molybdenite from Melitena area vary from 0.21 to 1.74 wt%, 0.79 wt% on average. The highest values were measured in samples from Pagoni Rachi (0.45-4.21 wt%, 1.98 wt% on average). Finally, microprobe analyses from molybdenite in Ktismata/Maronia showed Re content between 0.12 and 2.88 wt% (0.76 wt% on average). Rhenium is a very rare element with many definite uses, and is mainly associated with molybdenite in porphyry type deposits. According to the data published so far the Re content in molybdenite reaches up to 0.42 wt%. It is obvious therefore that such high Re concentrations (0.12 to 4.22 wt%) from the studied molybdenites in Thrace, are very ineresting for a possible future exploitation.

scholarly journals Mineral associations and their distribution in hydrothermal alteration zones of the Chelopech high-sulphidation deposit, Bulgaria

2017 ◽  
Vol 46 (2) ◽  
pp. 11-16
Author(s):  
Sylvina Georgieva
Keyword(s):  
Hydrothermal Alteration ◽  
Hydrothermal Fluids ◽  
Alteration Zones ◽  
Acid Sulphate ◽  
Mineral Associations ◽  
Mineral Assemblages ◽  
Hydrothermal Alteration Zones ◽  
Hydrothermal Environment ◽  
Host Rocks

This study is focused on the mineral assemblages developed during hydrothermal alteration in the host rocks of the Chelopech deposit and aims to reveal some characteristics of ore-forming fluids. Three well-distinguished and simultaneously formed hydrothermal alteration zones, characterized by specific mineral associations, occur in the area: advanced argillic, sericitic and propylitic. The presence of silica residue localities in the advanced argillic zone marks the major channels of hydrothermal fluids and indicates participation of extremely acid fluids. The existence of alunite and zunyite in the alteration indicates development of acid-sulphate hydrothermal environment, with presence of F in the fluid, which is considered to be an important feature of ore-bearing high-sulphidation epithermal systems. Dickite in association with alunite in the upper levels of the deposit suggests temperature of formation 200–250 °C. The highest temperature in depth is limited up to 375 °C, considering the occurrence of zunyite, pyrophyllite and dickite.

scholarly journals Rare element minerals’ assemblage in El Quemado pegmatites (Argentina): insights for pegmatite melt evolution from gahnite, columbite-group minerals and tourmaline chemistry and implications for minerogenesis

2021 ◽  
Author(s):  
Vanina López de Azarevich ◽  
Paolo Fulignati ◽  
Anna Gioncada ◽  
Miguel Azarevich
Keyword(s):  
Chemical Composition ◽  
Hydrothermal Alteration ◽  
Major Element ◽  
Mineral Chemistry ◽  
Element Composition ◽  
Hydrothermal Fluids ◽  
Rare Element ◽  
Major Element Composition ◽  
Santa Elena ◽  
Melt Evolution

AbstractThe pegmatite district of El Quemado (NW Pampean Ranges, NW Argentina) hosts several Ordovician pegmatite bodies of the LCT (Li, Cs, Ta) type. We present paragenetic assemblages for a set of samples from two of the El Quemado pegmatite groups, Santa Elena and Tres Tetas, and mineral chemistry analyses for gahnite, columbite-group minerals, tourmaline, micas, albite, microcline, and discuss the relation between their major element composition and the degree of evolution of pegmatite melts. The chemical composition of rare element minerals allows recognizing an evolutive trend reaching highly differentiated compositions, with complex paragenetic assemblages including Li-, Zr-, U-, Zn-, P-, Mn- and Ta-bearing minerals. The temperature of crystallization during the magmatic phase was below 400 °C. Non-pervasive hydrothermal alteration, testified by a moderate presence of phyllosilicates, affected the pegmatite bodies. Chlorite geothermometry indicates that the circulation of post-magmatic hydrothermal fluids occurred at a temperature ranging between 200 °C and 250 °C. The mineralogical features recognized in the El Quemado pegmatite rocks have implications for the metallogenesis of the region, suggesting that the pegmatites potentially contributed to the genesis of Ta-Nb oxide placer mineralizations.

scholarly journals Mineralogical and Fluid Inclusions Study of Epithermal Type Veins Intruding the Volcanic Rocks of the Kornofolia Area, Evros, NE Greece.

2019 ◽  
Vol 55 (1) ◽  
pp. 202
Author(s):  
Foteini Aravani ◽  
Lambrini Papadopoulou ◽  
Vasileios Melfos ◽  
Triantafillos Soldatos ◽  
Triantafillia Zorba ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Fluid Inclusion ◽  
Hydrothermal Alteration ◽  
Fluid Inclusions ◽  
Volcanic Rocks ◽  
The Other ◽  
Calc Alkaline ◽  
Ft Ir ◽  
Host Rocks

The volcanic rocks of Kornofolia area, Evros, host a number of epithermal-type veins. The host rocks are Oligocene calc-alkaline andesites to rhyo-dacites. The andesites form hydrothermal breccias and show hydrothermal alteration. The veins comprise mainly silica polymorphs such as quartz, chalcedony and three types of opal (milky white, transparent and green). Amethyst also forms in veins at the same area. Apart from the silica polymorphs, the veins are accompanied by calcite and zeolites. The main aim of this study is the characterization of the silica polymorphs. Using FT-IR analyses, variations in the crystal structure of the three opals were recognized. The green opal is found to be more amorphous than the other two types. Fluid-inclusion measurements were performed in calcite and were compared with amethyst from previous studies. The Th is between 121-175 °C and the Te between -22.9 and -22.4 °C. The salinities range from 0.9 to 4.5 wt % NaCl equiv.

scholarly journals PLUMBIAN "ALUNITES" IN HYDROTHERMAL ALTERATION ZONES OF EPITHERMAL AND PORPHYRY TYPE MINERALIZATIONS IN W. THRACE

2004 ◽  
Vol 36 (1) ◽  
pp. 492 ◽  
Author(s):  
Π. Βουδούρης ◽  
Κ. Αρίκας ◽  
Α. Κατερινόπουλος
Keyword(s):  
Hydrothermal Alteration ◽  
Solid Solutions ◽  
Mineral Chemistry ◽  
Alteration Zones ◽  
Hydrothermal Alteration Zones ◽  
Hydrothermal Environment

In this study a new occurrence of Pb-rich members of the alunite supergroup minerals is described. The "alunites" were traced in advanced argilic alteration zones of epithermal and porphyry type mineralizations in W. Thrace/(Greece). These "alunites" are Ca-Sr-Ba-Pb-rich phosphatessulfates and represent solid solutions between members of the alunite, woodhouseite and crandallite group minerals. The highest concentrations of PbO in the Mavrokoryfi and Melitaina alunites are 24.7% and 17.4% respectively. The plumbian phosphates-sulfates occur in the cores of the crystals and are surrounded by common K-Na-rich alunites in Mavrokoryfi and Ba-rich woodhouseite in Melitena, an indication that they were formed in a magmatic-hydrothermal environment after dissolution of apatite and feldspars by phosphate-sulphate rich solutions. The mineral-chemistry of these "alunites" can provide information regarding the genesis of the advanced argilic alteration zones in Greece, and help us in the distinction of the epithermal from deep porphyry style environments.

Mineralogical and Isotopic Characteristics of Sodic-Calcic Alteration in the Highland Valley Copper District, British Columbia, Canada: Implications for Fluid Sources in Porphyry Cu Systems

2020 ◽  
Vol 115 (4) ◽  
pp. 841-870 ◽  
Author(s):  
Kevin Byrne ◽  
Robert B. Trumbull ◽  
Guillaume Lesage ◽  
Sarah A. Gleeson ◽  
John Ryan ◽  
...  
Keyword(s):  
Water Source ◽  
White Mica ◽  
Late Triassic ◽  
Supporting Evidence ◽  
Fine Grained ◽  
Porphyry Cu ◽  
Mineral Assemblages ◽  
Alteration Minerals ◽  
External Water ◽  
Host Rocks

Abstract The Highland Valley Copper porphyry Cu (±Mo) district is hosted in the Late Triassic Guichon Creek batholith in the Canadian Cordillera. Fracture-controlled sodic-calcic alteration is important because it forms a large footprint (34 km2) outside of the porphyry Cu centers. This alteration consists of epidote ± actinolite ± tourmaline veins with halos of K-feldspar–destructive albite (1–20 XAn) ± fine-grained white mica ± epidote. The distribution of sodic-calcic alteration is strongly influenced by near-orthogonal NE- and SE-trending fracture sets and by proximity to granodiorite stocks and porphyry dikes. Multiple stages of sodic-calcic alteration occurred in the district, which both pre- and postdate Cu mineralization at the porphyry centers. The mineral assemblages and chemical composition of alteration minerals suggest that the fluid that caused sodic-calcic alteration in the Guichon Creek batholith was Cl bearing, at near-neutral pH, and oxidized, and had high activities of Na, Ca, and Mg relative to propylitic and fresh-rock assemblages. The metasomatic exchange of K for Na, localized removal of Fe and Cu, and a paucity of secondary quartz suggest that the fluid was thermally prograding in response to magmatic heating. Calculated δ18Ofluid and δDfluid values of mineral pairs in isotopic equilibrium from the sodic-calcic veins and alteration range from 4 to 8‰ and −20 to −9‰, respectively, which contrasts with the whole-rock values for least altered magmatic host rocks (δ18O = 6.4–9.4‰ and δD = −99 to −75‰). The whole-rock values are suggested to reflect residual magma values after D loss by magma degassing, while the range of hydrothermal minerals requires a mixed-fluid origin with a contribution of magmatic water and an external water source. The O-H isotope results favor seawater as the source but could also reflect the ingress of Late Triassic meteoric water. The 87Sr/86Srinital values of strongly Na-Ca–altered rocks range from 0.703416 to 0.703508, which is only slightly higher than the values of fresh and potassic-altered rocks. Modeling of those data suggests the Sr is derived predominantly from a magmatic source, but the system may contain up to 3% seawater Sr. Supporting evidence for a seawater-derived fluid entrained in the porphyry Cu systems comes from boron isotope data. The calculated tourmaline δ11Bfluid values from the sodic-calcic domains reach 18.3‰, which is consistent with a seawater-derived fluid source. Lower tourmaline δ11Bfluid values from the other alteration facies (4–10‰) suggest mixing between magmatic and seawater-derived fluids in and around the porphyry centers. These results imply that seawater-derived fluids can infiltrate batholiths and porphyry systems at deep levels (4–5 km) in the crust. Sodic ± calcic alteration may be more common in rocks peripheral to porphyry Cu systems hosted in island-arc terranes and submarine rocks than currently recognized.

Mg-rich dumortierite in cordierite-orthoamphibole-bearing rocks from the high-grade Bamble Sector, south Norway

1991 ◽  
Vol 55 (381) ◽  
pp. 563-577 ◽  
Author(s):  
Diederik Visser ◽  
Antony Senior
Keyword(s):  
Mineral Chemistry ◽  
Total Iron ◽  
Significant Part ◽  
High Grade ◽  
Alteration Zones ◽  
Tetrahedral Sites ◽  
Titaniferous Magnetite ◽  
Mineral Assemblages ◽  
A Minor ◽  
Bamble Sector

AbstractDumortierite is described from several occurrences of cordierite-orthoamphibole-bearing rocks in the upper-amphibolite facies area of the Bamble Sector, south Norway. Dumortierite occurs with chlorite, muscovite and quartz in late M4 alteration zones or aggregates after M3, peak-metamorphic cordierite and garnet and early M4 vein-cordierite, and intergrown with or replacing orthoamphibole. Late M4P-T conditions, which are interpreted as conditions of dumortierite formation, are estimated from the associated late M4 kyanite-andalusite-chlorite-quartz assemblage and Mg-Fe exchange geothermometry to be 500 ± 50 °C and 3–4 kbar. Retrogression of M3 mineral assemblages is initiated by influx of fluids with XCO2 of 0.3–0.4 during early M4 followed by more water-rich fluids during late M4. Late M4 fluids may show local variations in alkalis and boron. The dumortierites are the most Mg-rich (2.23–3.42 wt. % MgO) ever reported, and contain 0.00–2.05 wt.% TiO2, 0.00–1.08 wt.% Fe2O3, 29.62–32.42 wt.% SiO2 and 55.20–59.71 wt.% Al2O3. Al is the most likely substituent for Si, which shows a minor deficiency at the tetrahedral sites in most dumortierites. The major variations in the mineral chemistry can be described by the coupled substitutions Mg + Ti = 2AlVI, 3Mg = 2AlVI and possibly Mg + H = AlVI. Favoured by low ƒO2 prevailing conditions a significant part of total iron in dumortierites at one locality is present as Fe2+ giving evidence for the Fe2+ + SiIV = AlIV + AlVI tschermakite substitution. FeMg−1 substitution is considered to be limited. Ti-rich dumortierites coexist with rutile, ilmenite or titaniferous magnetite. The development of dumortierite from orthoamphibole correlates with an observed decrease of Al, Mg and Na and increase of Si and Fe in orthoamphibole towards dumortierite.

scholarly journals HYDROTHERMAL ALTERATION AND MINERALIZATION OF THE PETROTA EPITHERMAL SYSTEMS (W.THRACE, GREECE)

2004 ◽  
Vol 36 (1) ◽  
pp. 369 ◽  
Author(s):  
Κ. Μιχαήλ ◽  
Μ. Δημήτρουλα
Keyword(s):  
Hydrothermal Alteration ◽  
Hydrothermal Systems ◽  
Alteration Zones ◽  
Epithermal System ◽  
Argillic Alteration ◽  
Ore Mineralization ◽  
System 2 ◽  
Advanced Argillic Alteration ◽  
Hydrothermal Alteration Zones ◽  
Host Rocks

At the Petrota graben important epithermal zones are developed. On the basis of the mineral assemblages of alteration zones and the type of the host rocks, the epithermal zones can be grouped into three epithermal systems: 1. Perama epithermal system 2. Mavrokoryfi epithermal system and 3. Othondoto epithermal system Hydrothermal alteration zones are developed within volcanoclastic rocks - epiclastic sandstones, andésite tuffs (Perama epithermal system), hyaloclastites (Mavrokoryfi) and rhyolitic rocks (Othondoto). Silicification (in various types) and advanced argillic alteration are the most important alteration zones and are established on the largest scale. Ore mineralisation occurs as veins, veinlets in silicification zones or secondary mineralisation in the supergene zone (Perama epithermal system). Disseminated ore mineralization is also found in the silicification zone at Othondoto and Mavrokoryfi epithermal systems. Based on the geological environment, the type of hydrothemal alteration zones (silicification and advanced argillic alteration) and the mineral compositon of the ore (enargite- luzonite), the hydrothermal systems of Petrota graben can be referred as high sulfidation systems.

Origin of the Basoren (Kutahya, W Turkey) bentonite deposits

Clay Minerals ◽  
2004 ◽  
Vol 39 (2) ◽  
pp. 219-231 ◽  
Author(s):  
A. Yildiz ◽  
M. Kuscu
Keyword(s):  
Chemical Composition ◽  
Hydrothermal Alteration ◽  
Volcanic Glass ◽  
Hydrothermal Solutions ◽  
X Ray Diffraction ◽  
Pyroclastic Rocks ◽  
X Ray ◽  
Alteration Zones ◽  
Parent Rocks ◽  
Ophiolitic Rocks

AbstractBentonite deposits in Basoren Kutahya, West Anatolia, Turkey formed from alteration of perlite and pyroclastic rocks of Pliocene age. The distribution of bentonite deposits along faults in the study area indicates that the alteration solutions were hydrothermal. Although lateral zonation is observed in bentonite deposits in some regions (i.e. Demirli, Akyokus, Seklice- Sarıokuz, etc.), alteration zones are extremely irregular in the Cayırlık bentonite deposit.X-ray diffraction studies have shown that Basoren bentonites contain dioctahedral Ca-smectite.The Greene-Kelly test (Li-saturation and heating) showed that the Demirli and Akyokus bentonites consist of montmorillonite and that the Cayırlık bentonite consists of montmorillonite and/or beidellite. Spherulitic or hemispherical ‘crystals’ of opal-CT minerals formed from hydrothermal alteration of volcanic glass. The MgO, CaO and total Fe2O3 enrichment in bentonites, compared to parent rocks, is related to the chemical composition of hydrothermal solutions that passed through the ophiolitic rocks such as serpentinite.

scholarly journals Hydrothermal alteration, fumarolic deposits and fluids from Lastarria Volcanic Complex: A multidisciplinary study

2016 ◽  
Vol 43 (2) ◽  
pp. 166 ◽  
Author(s):  
Felipe Aguilera ◽  
Susana Layana ◽  
Augusto Rodríguez-Díaz ◽  
Cristóbal González ◽  
Julio Cortés ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Fluid Inclusions ◽  
Alkali Metals ◽  
Fumarolic Activity ◽  
Volcanic Complex ◽  
Main Process ◽  
Gaseous Species ◽  
Alteration Zones ◽  
Multidisciplinary Study ◽  
Hydrothermal Alteration Zones

A multidisciplinary study that includes processing of Landsat ETM+ satellite images, chemistry of gas condensed, mineralogy and chemistry of fumarolic deposits, and fluid inclusion data from native sulphur deposits, has been carried out in the Lastarria Volcanic Complex (LVC) with the objective to determine the distribution and characteristics of hydrothermal alteration zones and to establish the relations between gas chemistry and fumarolic deposits. Satellite image processing shows the presence of four hydrothermal alteration zones, characterized by a mineral assemblage constituted mainly by clay minerals, alunite, iron oxides, and more subordinated ferrous minerals and goethite. Hydrothermal alteration zones present in the Lastarria sensu stricto volcano are directly related to the recent fumarolic activity. Geochemistry of fumarolic gas condensed, obtained from two fumaroles at temperatures between 328 and 320 °C, has allowed detecting 37 diverse elements corresponding to halogens, chalcophiles, siderophiles, alkali metals, alkali earth metals and Rare Earth Elements (REE), with concentrations that vary widely between 5,620 ppm (chlorine) and 0.01 ppm (Mo, Ag, Sn, Pb, Se, Mg and Cr). Logarithm of Enrichment Factor (log EFi) for each element present values between 6.35 (iodine) and<1 (K, Na, Ca, Fe and Al). Those elements are originated primarily from a magmatic source, whereas at shallow level a hydrothermal source contributes typical rock-related elements, which are leached from the wall rock by a strong interaction with hyperacid fluids. Mostly of elements detected are transported to the surface in the fumarolic emissions as gaseous species, while very few elements (Mg, Ca and Al) are transported in silicate aerosols. A wide spectrum of minerals are present in the fumarolic deposits, which are constituted by sublimates and incrustations, and the main minerals phases are distributed in six mineral families, corresponding to sulphates, hydrated sulphates, sulphides, halides, carbonates, silicates and native element minerals. The sublimate/incrustation minerals are dominated by the presence of sulphate, sulphur, chlorine and diverse rock-related elements, which are formed by processes that include a. oxidation of gaseous phase; b. strong rock-fluid interaction; c. dissolution of silicate minerals and volcanic glass; d. gas-water interaction; e. deposition/precipitation of saline bearing minerals; f. oxidation of sublimates/incrustations to form secondary minerals and g. remobilization of sulphur deposits by meteoric water. Despite that sublimate/ incrustation minerals are dominated by rock-related elements, its chemistry shows high contents of high-volatile elements as As, Sb, Cd, among others. Fluid inclusions studies carried out in thin pseudobanded native sulphur from fumarolic deposits, by use of Raman and infrared spectroscopy combined with microthermometry analyses, provided evidence of H2O, CO2, H2S, SO4, COS bearing fluids, homogenization temperatures around 110 °C and salinities varying from ~11 to ~7 wt% NaCl. Fluid inclusions data show also evidences of a mixing (dilution) between hot and saline fluid with a cooler fluid (cold groundwater or a steam-heated water) as the main process.

Secondary Beryl in Cordierite/Sekaninaite Pseudomorphs from Granitic Pegmatites – A Monitor of Elevated Content of Beryllium in the Precursor

2020 ◽  
Author(s):  
Petr Gadas ◽  
Milan Novák ◽  
Michaela Vašinová Galiová ◽  
Adam Szuszkiewicz ◽  
Adam Pieczka ◽  
...  
Keyword(s):  
Czech Republic ◽  
Chemical Composition ◽  
Limit Of Detection ◽  
Coarse Grained ◽  
Secondary Minerals ◽  
Moldanubian Zone ◽  
Granitic Pegmatites ◽  
Icp Ms ◽  
Mineral Assemblages ◽  
Host Rocks

Abstract Cordierite-group minerals (cordierite and sekaninaite) from granitic pegmatites are often strongly to completely altered to a fine- or coarse-grained mixture of muscovite, chlorite and/or, biotite, along with several less common secondary minerals, including mainly paragonite, tourmaline, and secondary beryl. The mixture is a common product of early subsolidus hydrothermal alteration at the examined pegmatites of the beryl-columbite subtype – Věžná I and Drahonín (Moldanubian Zone, Czech Republic) and Mount Begbie (Shuswap Complex, Canada); of the beryl-columbite-phosphate subtype – Szklary (Góry Sowie Block, Poland); and of miarolitic intragranitic pegmatites – Zimnik (Massif Strzegom-Sobótka, Poland). We studied in detail (EPMA, LA-ICP-MS) relics of primary cordierite/sekaninaite: Věžná I (Crd77–72Sek27–22MnCrd2–1, Be = 0.39–0.25 apfu, Li = 0.06–0.04 apfu), Drahonín (Crd13–9Sek74–71MnCrd17–16, Be = 0.24–0.18 apfu, Li = 0.07–0.05 apfu), Szklary (Crd50–49Sek30–26MnCrd25–21, Be = 0.45–0.41 apfu, Li ≤ 0.02 apfu), Mount Begbie (Crd34–33Sek53–43MnCrd24–14, Be = 0.33–0.29 apfu, Li = 0.26–0.23 apfu), and Zimnik (Crd2–1Sek75–71MnCrd28–23, Be = 0.25–0.15 apfu, Li = 0.18–0.12 apfu). Secondary beryl has a similar Mg/(Mg+Fe) ratio to its cordierite/sekaninaite precursor but is Mn depleted. The mineral assemblages and textures of the pseudomorphs were examined with a focus on secondary beryl, which forms anhedral grains to subhedral elongated crystals, up to 0.3 mm in size, or aggregates of these in textural equilibrium with associated phyllosilicates and tourmaline. Tourmaline is known from Věžná I, Drahonín, Mount Begbie, and Zimnik, the last also with topaz and “zinnwaldite” (a mineral with chemical composition between siderophyllite and polylithionite). Secondary beryl in pseudomorphs after cordierite/sekaninaite from granitic pegmatites and more evolved granites may have been often overlooked; hence, we present its textures and morphology so that it can be recognized during routine EPMA study and to study the source of elevated concentrations of Be in primary cordierite/sekaninaite. The empirical limit of detection of secondary beryl in pseudomorphs is ∼500–1000 ppm Be, which corresponds to ∼1–2 vol.% of secondary beryl. The chemical composition of the secondary beryl and other minerals indicate that the fluids responsible for the alteration were exsolved from the residual pegmatite melt and were not contaminated by fluids from the host rocks.

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