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Papers by Jan Cempirek

Goldschmidt2022 abstracts

The leucosome-hosted sapphire (corundum) occurrence near Revelstoke, British Columbia, Canada, oc... more The leucosome-hosted sapphire (corundum) occurrence near Revelstoke, British Columbia, Canada, occurs in the Monashee Complex of the Omineca Belt of the Canadian Cordillera. Corundum occurs in banded or pod-like zones within a leucosome containing muscovite + biotite + albite + orthoclase + garnet ± zircon ± sillimanite ± ilmenite ± monazite ± rutile ± Znrich spinel ± titanite. Petrography, whole rock geochemistry, zircon morphology, and thermodynamic models support an anatectic source for the leucosome. Relatively high FeO, MgO, Al 2 O 3 , CaO, and TiO 2 , and low SiO 2 and K 2 O contents of Blue Jay rocks suggest they represent restite. Numerically modeled melt compositions using the Rhyolite-MELTS software of Thor-Odin dome basement paragneiss approach the Blue Jay leucosome SiO 2 values at temperatures between 700-750 °C at 7-8 kbar, which correspond to melt-yields of ~10% melt. A calculated P-T projection using the Perple_X software indicates that the Blue Jay corundum formed at the expense of muscovite through the reaction: Ms = Crn + San + H 2 O. A pseudosection calculated using Perple_X shows that garnet equilibrated at 6-9 kbar and 650 to 750 °C in a melt bearing assemblage: staurolite + muscovite + garnet + sillimanite + ilmenite, and the corundumbearing pods were fully solidified by 2.5-5 kbar and 650-750 °C in the assemblage: plagioclase + K-feldspar + biotite + corundum + sillimanite + ilmenite. Zircon 206 Pb/ 238 U ages and trace element content indicates that corundum formed between 56 and 50 Ma.

Journal of GEOsciences, 2012

Radial aggregates of blue-grey tourmaline were found in plagioclase-muscovite-scapolite metaevapo... more Radial aggregates of blue-grey tourmaline were found in plagioclase-muscovite-scapolite metaevaporite layers in dolomite marble near Prosetín (Olešnice Unit, Moravicum, Czech Republic). It occurs in association with plagioclase (An 15-37), muscovite, scapolite, phlogopite, vermiculite, pumpellyite-(Al), and clinozoisite. Electron-microprobe analyses of tourmaline show dravitic composition with very high content of Mg (1.92 to 2.77 apfu), Al (up to 6.71 apfu), low content of Fe (up to 0.39 apfu) and variable amounts of vacancies (0.09 to 0.47) and Ca (0.03 to 0.29 apfu) in the X-site. Some analyses correspond to "oxy-dravite" and some others almost attain magnesio-foitite compositions. The proportion of X-site vacancy decreases from the crystal cores to their rims while Ca content increases. Generally, charge excess due to the high Al-contents is balanced either by an increasing X-site vacancy or by deprotonization of W OH; the W O 2content calculated from charge-balanced formula attains 0.71 apfu. Lattice parameters [a = 15.9116(6) Å; c = 7.1987(4) Å] and deduced average bond lengths ( = 1.995 Å; = 1.929 Å) indicate a relatively high Al-Mg disorder. Three main substitution mechanisms are inferred to operate in the studied magnesian tourmalines: (1) CaMg(NaAl)-1 , mainly in Ca-enriched dravite, (2) X □Al(NaMg)-1 in nearly magnesio-foititic compositions, and (3) AlO(MgOH)-1 in "oxydravitic" members. The tourmaline is relatively poor in trace elements; only Ti, Sr, and Ga exceed 100 ppm according to LA-ICP-MS study. There is a pronounced positive correlation between Sr and Ca (r 2 = 0.77), which suggests that Sr accumulated in Ca-enriched zones of dravite. The pale blue-grey color of the studied tourmalines is most likely a result of Fe 2+ crystal field transitions along with the absence of significant amounts of other chromophores. Trace-element contents, mineral assemblage and compositional zoning of tourmalines as well as host-rock mineral association suggest prograde metamorphic growth and support metaevaporitic origin of the plagioclase-muscovite-scapolite rocks.

The Canadian Mineralogist, 2014

Journal of GEOsciences, 2013

Ore Geology Reviews, 2015

The Sn-rich Qiguling topaz rhyolite dike intrudes the Qitianling biotite granite of the Nanling R... more The Sn-rich Qiguling topaz rhyolite dike intrudes the Qitianling biotite granite of the Nanling Range in southern China; the granite hosts the large Furong Sn deposit. The rhyolite dike is typically peraluminous, volatileenriched, and highly evolved. Whole-rock F and Sn concentrations attain 1.9 wt.% and 2700 ppm, respectively. The rhyolite consists of a fine-grained matrix formed by quartz, feldspar, mica and topaz, enclosing phenocrysts of quartz, feldspar and mica; it is locally crosscut by quartz veinlets. Lithium-bearing micas in both phenocrysts and the groundmass can be classified as primary zinnwaldite, "Mus-Ann" (intermediate member between annite and muscovite), and secondary Fe-rich muscovite. Topaz is present in the groundmass only; common fluorite occurs in the groundmass and also in a specific cassiterite, rutile and fluorite (Sn-Ti-F) assemblage. Cassiterite and rutile are the only Sn and Ti minerals; both cassiterite and Nb-rich rutile are commonly included in the phenocrysts. The Sn-Ti-F assemblage is pervasive, and contains spongy cassiterite in some cases; cassiterite also occurs in quartz veinlets which cut the groundmass. Electron microprobe and LA-ICP-MS compositions were used to study the magmatic and hydrothermal processes and the role of F in Sn mineralization. The presence of zinnwaldite and "Mus-Ann", which are respectively representative of early and late mica crystallization during magma differentiation, also suggests a significant decrease in f(HF)/f(H 2 O) of the system. Cassiterite included in the zinnwaldite phenocrysts is suggested to have crystallized from the primary magma at high temperature. Within the Sn-Ti-F aggregates, rutile crystallized as the earliest mineral, followed by fluorite and cassiterite. Spongy cassiterite containing inclusions of the groundmass minerals indicate a low viscosity of the late fluid. The cassiterite in the quartz veinlets crystallized from low-temperature hydrothermal fluids, which possibly mixed with meteoric water. In general, cassiterite precipitated during both magmatic and hydrothermal stages, and over a range of temperatures. The original fluorine and tin enrichments, f(HF)/f(H 2 O) change in the residual magma, formation of Ca,Sn,F-rich immiscible fluid, decrease of the f(HF) during groundmass crystallization, and mixing of magma-derived fluids with low-saline meteoric water during the late hydrothermal stage, are all factors independently or together responsible for the Sn mineralization in the Qiguling rhyolite.

Journal of GEOsciences, 2012

Clinopyroxene-garnet scheelite skarn containing accessory niobian titanite, native bismuth and Bi... more Clinopyroxene-garnet scheelite skarn containing accessory niobian titanite, native bismuth and Bi-tellurides of the Bi 2 X and Bi 5 X 3 series, together with Fe-and Fe-As sulphides, is associated with the contact of chondrodite marble with melanocratic granite-quartz syenite (durbachite). Hedenbergite-rich vein in this marble can be considered as an additional type of skarn. The presence of accessory niobian titanite is typical, in particular, of the veins. In addition to increased Nb contents (≤ 10.6 wt. % Nb 2 O 5 ; ≤ 0.164 apfu Nb) and locally Ta (≤ 4.07 Ta 2 O 5 ; ≤ 0.038 apfu Ta), it is relatively rich in Al (≤ 0.253 apfu). Locally it contains elevated Fe, Sn, Zr and F contents. Negative correlations of Al + F with R 4+ and Al + (Nb 5+ , Ta 5+) with R 4+ accompanied by low contents of Na in titanite correspond to the substitutions Al(OH,F)(TiO)-1 and Al(Nb,Ta)Ti-2. Niobian titanite has anomalous composition if compared to skarn mineral assemblages worldwide. The Bi-(sulpho-) telluride with empiric formula Bi 1.98 (Te 0.66 S 0.34 Se 0.02) Σ1.02 is a member of the Bi 2 X series, whose members were described from numerous localities as unnamed minerals. In contrast to the published data this phase contains increased sulphur contents up to 0.33 apfu. The second Bi-(sulpho-) telluride with empiric formula (Bi 4.51 Fe 0.40 Cd 0.03 Pb 0.02 Sb 0.01 As 0.01) Σ4.98 (Te 1.58 S 1.36 Se 0.08) Σ3.02 is probably a S-rich member of the Bi 5 X 3 series. In the evolution of the skarn it is possible to distinguish stage I responsible for the formation of the older Mg-and younger Ca-skarns, and stage II, characterised by increased Fe contents. The scheelite-sulphide mineralization was formed during a third (retrogression) stage followed by brittle deformation. Emplacement of siderite ± quartz veins represents the fourth (terminal) stage of mineralization.

Journal of GEOsciences, 2013

Two types of V-rich dravitic tourmaline (oxy-dravite to dravite) distinct in their color, morphol... more Two types of V-rich dravitic tourmaline (oxy-dravite to dravite) distinct in their color, morphology, paragenesis and composition from graphite quartzite at Bítovánky near Třebíč, Moldanubicum, Bohemian Massif, were studied by means of electron microprobe, laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS), and single-crystal X-ray diffraction. Green oxy-dravite (GVD) from graphite quartzite is sporadically zoned with V-enriched rims; brown oxy-dravite to dravite (BVD) from mobilized quartz-rich nests is characterized by such V-enriched rims. The formulae derived from chemical and structure data of the two oxy-dravite varieties are X (Na 0.534 Ca 0.284 □ 0.164 K 0.018) Y (Mg 1.461 V 0.679 Al 0.771 Fe 0.042 Mn 0.003 Ti 0.043) Z (Al 5.074 V 0.237 Mg 0.689) T (Si 5.782 Al 0.218 O 18) (BO 3) 3 [(OH) 3.058 O 0.75 F 0.192 ] for GVD and X (Na 0.539 Ca 0.148 □ 0.297 K 0.017) Y (Mg 0.992 V 0.302 Al 1.039 Fe 0.582 Mn 0.011 Ti 0.068 Cr 0.007) Z (Al 5.339 V 0.082 Mg 0.578) T (Si 5.864 Al 0.136 O 18) (BO 3) 3 [(OH) 3.209 O 0.621 F 0.171 ] for BVD, respectively. Both types of V-rich oxy-dravite feature Al-Mg-V disorder between the Y and Z sites; V and Cr are preferentially located at the Y site. The V-rich oxy-dravite from Bítovánky has unusually high Ca contents and high proportion of vacancy at the X site. Most common trace elements include Ti, Cr, Mn, Zn, Sc, Ga, Sr, Ni, Sn, and LREE. High concentrations of V, Cr and Ti (as well as elevated Mn, Zn, Sc, Sn, and Sr) in the GVD and late BVD most probably result from hydrothermal dissolution of (Ti,V)-oxides and other accessory phases during a high-grade metamorphic overprinting of the host graphite quartzite assemblage.

Journal of GEOsciences, 2012

Abyssal pegmatites from Starkoè and Bìstvina are typical examples of the AB-BBe subclass pegmatit... more Abyssal pegmatites from Starkoè and Bìstvina are typical examples of the AB-BBe subclass pegmatites in the Bohemian Massif. The features typical for origin and evolution of both abyssal pegmatites are better preserved in the pegmatite at Starkoè, where, based on paragenetic relationships, three distinct assemblages were recognized: (i) Primary igneous assemblage: plagioclase I + quartz I + muscovite + garnet III + tourmaline I + dumortierite I + chrysoberyl; (ii) Prograde metamorphic assemblage: quartz II + plagioclase II + kyanite + K-feldspar + staurolite + tourmaline II + dumortierite II; (iii) Retrograde metamorphic assemblage: pyrophyllite and kaolinite. Plagioclase, quartz and muscovite are major minerals in the pegmatite veinlet; the most common accessory minerals include tourmaline, dumortierite, garnet, K-feldspar and kyanite, whereas only trace amounts of chrysoberyl, staurolite and several very rare accessory minerals were found. Composition of tourmaline is controlled by the two-stage evolution of the pegmatite. Primary tourmaline I from Starkoè exhibits crystallization trend expressed by the substitution (Y,Z Al T Al)(Y,Z R 2+ T Si 4+)-1. Prograde metamorphic event introduced additional Fe and Mg from the host rock into the system and remobilization of B allowed crystallization of Mg-enriched, rather homogeneous tourmaline II. Strakoè and all other known pegmatites of AB-BBe subclass in the Bohemian Massif occur in the Gföhl Unit, along the easternmost border of the Moldanubicum. Pegmatite host rocks exhibit HP metamorphic conditions and low degree of MP overprint. Such metamorphic evolution is a typical feature of host rocks of similar abyssal pegmatites in high-grade terrains in Antarctica, Norway and Madagascar.

The Canadian Mineralogist, 2014

Mineralogy and Petrology, 2005

Elevated P contents of up to 0.086 apfu (1.21 wt.% P 2 O 5) were found in garnet from leucocratic... more Elevated P contents of up to 0.086 apfu (1.21 wt.% P 2 O 5) were found in garnet from leucocratic granitic rocks (orthogneisses, granites, barren to highly evolved pegmatites) in the Moldanubicum and Silesicum, Czech Republic, and in complex granitic pegmatites from southern California, USA, and Australia. Minor concentrations (0.15-0.55 wt.% P 2 O 5) appear ubiquitous in garnet from leucocratic granitic rocks of different origins and degrees of fractionation. Concentrations of P are not related to Mn=(Mn þ Fe) that vary from 0.12-0.86 and to textural types of garnet (i.e., isolated anhedral to euhedral grains and nodules, graphic and random garnet-quartz aggregates, subsolidus veins of fine-grained garnet). Garnet compositions exhibit negative correlations for P=Si and P=R 2þ where R 2þ ¼ Fe þ Mn þ Mg þ Ca, while Al is constant at $2.05 apfu. Concentrations of Na are largely below 0.02 apfu but positively correlate with P. The main substitution may involve A-site vacancy and=or the presence of some light element(s) in the crystal structure. The substitution &P 2 R 2þ À1 Si À2 and=or or alluaudite-type Na&P 3 R 2þ À1 Si À3 seem the most likely P-incorporating mechanisms. The partitioning of P among garnet and associated minerals in granitic systems remains unclear; however, it directly affects the distribution of Y and REEs. 206 K. Breiter et al. 208 K. Breiter et al.

Mineralogical Magazine, 2008

Euhedral crystals of complexly zoned niobian titanite (up to 0.3 mm) are enclosed in hedenbergite... more Euhedral crystals of complexly zoned niobian titanite (up to 0.3 mm) are enclosed in hedenbergite (Hd53—81Di15—43Jh3-5) and quartz from a hedenbergite vein skarn at Kamenne doly near Pisek, Czech Republic. They are associated with minor clinozoisite-epidote (Ps3—22), calcite, plagioclase (An95). scapolite (Me80—82), scheelite, pyrrhotite, fluorapatite, arsenopyrite, native bismuth and Bi,Te-minerals. The following textural and compositional subtypes were recognized: (I) Nb-rich titanite, (II) Nb-moderate titanite in the central zone, (III) Nb-poor, Sn-enriched titanite and (IV) Nb-poor, Al,F-rich titanite in the outer zone. The substitution Al(Nb,Ta)Ti—2 is dominant in subtypes I and II, the titanite subtype I being characterized by elevated contents of Al ≤ 0.257 atoms per formula unit (a.p.f.u.), Nb (≤ 0.161 a.p.f.u.) and Ta (≤ 0.037 a.p.f.u.). Amounts of Al, Nb and Ta in subtype II are smaller and more variable. The minor substitution SnTi—1 occurs chiefly in titanite subtype III...

Lithos, 2011

A peralkaline, ultrapotassic dyke found at Šebkovice (Třebíč district, western Moravia) is a mine... more A peralkaline, ultrapotassic dyke found at Šebkovice (Třebíč district, western Moravia) is a mineralogically extreme member of a dyke swarm occurring along the southeastern border of the Moldanubian Region of the Bohemian Massif. The dyke shows a simple zoning, with a very fine-grained marginal zone grading into a medium-grained central zone. It has a primary mineral assemblage of microcline and potassic amphiboles, with accessory apatite and altered phlogopite. The microcline exhibits an unusual red luminescence colour and pronounced substitution of Fe 3+ for Al, with measured contents of Fe 2 O 3 up to 8.5 wt.% (0.31 apfu Fe 3+). Amphiboles have very high K (up to 0.99 apfu) and Si contents; their compositions follow an alkaline fractionation trend from potassic-richterite to potassic-magnesio-arfvedsonite, characterized by an increase of Na/K and a decrease of Ca, Mg, Fe 2+ and Ti via heterovalent substitutions [B] Ca + [C] (Mg,Fe 2+) → [B] Na + [C] Fe 3+ and Ti +Mg → 2Fe 3+. The most evolved apatite is significantly enriched in SrO (up to 9.7 wt.%; 0.49 apfu Sr). The core of the dyke and late veinlets contain unique late-to post-magmatic Ba-Ti-Zr-bearing mineral assemblages of baotite, henrymeyerite, titanite, rutile, benitoite and bazirite. Anhedral baotite fills interstices distributed inhomogeneously in the dyke centre; it is locally replaced by a Ba-bearing titanite + henrymeyerite + rutile + quartz assemblage. Henrymeyerite (the second record in a lamproite) shows variable Fe/Ti ratios and represents a solid solution of the hepta-and hexatitanate components. Euhedral crystals of benitoite and bazirite are enclosed in the late-stage quartz-titanite-apatite veinlets in the finegrained margin of the intrusion. In terms of a mineralogical-genetic classification, the Šebkovice dyke can be considered as a new high-silica (~57 wt.% SiO 2) variety of lamproite (variety Šebkovice), and represents a unique expression of post-collisional potassic magmatism on the southeastern border of the Bohemian Massif. The peralkaline dykes from this area show mineralogical and geochemical features similar to those of silicarich orogenic lamproites emplaced at destructive plate margins. In terms of the modern classification of lamproites, the Šebkovice dyke is the first lamproite recognised in the Variscan orogenic belt.

Journal of Geochemical Exploration, 2009

Rare earth elements and yttrium geochemistry of dolomite from post-Variscan vein-type Zn-Pb-Cu mi... more Rare earth elements and yttrium geochemistry of dolomite from post-Variscan vein-type Zn-Pb-Cu mineralization was studied in the Nízký Jeseník and Upper Silesian Basins. Combined with crush-leach analyses of fluid inclusions, the study provided important information on fluid-rock interaction, physicochemical and redox conditions during crystallization of the dolomite. The mineralization is hosted by Carboniferous siliciclastic rocks, representing Variscan flysch and molasse sedimentation. Dolomite samples contain highly variable contents of REE (between 18 and 295 ppm) and Y (between 17 and 95 ppm). REY patterns are divided into four different groups which differ in regional provenance, LREE vs. HREE enrichment/depletion and significance of Eu, Gd and Y anomalies. These patterns can be the result of 1) precipitation of dolomite from near neutral fluids with important concentrations of complexing ligands as a main factor for the REY partitioning, 2) interaction of migrating fluids with host or basement rocks, or, most probably, 3) a combination of both. Regarding the importance of complexing ligands, it is proposed that in all samples fluoride and chloride complexes prevailed over sulphate, bicarbonate and hydroxide complexes. Interaction of fluids with rocks was strongly affected by the fluid temperature. Dolomites which precipitated from fluids with homogenization temperature higher than 110°C are mostly REY-enriched while fluids colder than 110°C produced REY-depleted dolomite. The REY-enrichment may indicate higher effectiveness of leaching of REEbearing minerals (probably monazite, allanite and biotite) at higher temperatures. The preferential loss of LREE can be caused by the recrystallization or remobilization of dolomite. Generally, an increase in salinity and contents of Cl and F in the fluids is mostly accompanied by a higher REY content in dolomite. Positive Eu anomalies and small negative Gd and Y anomalies are typical for most of the chondrite-normalized patterns. Positive Eu CN anomalies in dolomites are most probably the result of an increase of Eh in the parent fluid. Distribution of Y is expected to be predominantly controlled by solution complexation.

The Canadian Mineralogist, 2006

The pale blue rim of olenite on a black crystal of olenite-schorl tourmaline from an abyssal pegm... more The pale blue rim of olenite on a black crystal of olenite-schorl tourmaline from an abyssal pegmatite at the locality Kuklík, near Kutná Hora, Czech Republic, has been chemically and structurally characterized. The optimized formula, calculated using chemical and structural data, is X (Na 0.54 Ca 0.14 K 0.01 M 0.31) Y (Al 2.15 Fe 2+ 0.78 Mn 2+ 0.06 Ti 4+ 0.01) Z (Al 5.90 Mg 0.10) T (Si 5.60 Al 0.40) B 3 O 27 V [(OH) 2.49 O 0.51 ] W (O 0.99 F 0.01), with a 15.8838(3), c 7.1056(2) Å and R = 0.017. The relatively short bond-length, 1.992 Å, confirms the high content of Al at the Y site (~2.1 atoms per formula unit, apfu). It is similar to that of olenite from the type locality, though the olenite from Kuklík contains significant amounts of Fe at the Y site, and significant amounts of [4] Al (~0.4 apfu) instead of [4] B in the T site. This finding is supported by results of the structure determination, which show an enlarged bond-length of ~1.626 Å. This sample of olenite shows that nonstoichiometric content of Si does not always imply [4] B in aluminous tourmaline. No H could be found at the O1 site by refinement, and the spherical distribution of electron density in the difference-Fourier map around the O1 site supports the conclusion that this site is only or mainly occupied by O and not by OH. On a bond-angle distortion (s oct 2 of the ZO 6 octahedron)- distance diagram, the olenite from Kuklík lies between compositions containing 3 (OH) at the V site, and natural buergerite, which contains 0.3 (OH) and 2.7 O at the V site (O3 site). The (OH) content with ~2.5 (OH) pfu, which was calculated for a charge-balanced formula, is in a good agreement with these findings and with the integrated intensity of the OH overtones in the 7000 cm-1 region (690 cm-2 per cm thickness), which is one of the lowest measured to date for tourmaline. The OH seems to be ordered strongly at the O3 site. The composition of this sample of olenite shows a trend toward the proposed olenite end-member formula, which contains only 1 OH group. The low content of F (0.01 apfu) is uncommon for natural Al-rich and Mg-poor tourmaline from granitic pegmatites. Synchrotron micro-XANES was used to detect the valence state of Fe in this crystal; it was found to have 93 ± 10% of the total Fe as Fe 2+. Optical absorption spectra show that the blue color is derived primarily from a combination of [6] Fe 2+ , together with [6] Fe 2+ interaction with a minor amount of [6] Fe 3+ .

The Canadian Mineralogist, 2004

Dark brown porous ferrotapiolite is a dominant product of alteration in pseudomorphs after primar... more Dark brown porous ferrotapiolite is a dominant product of alteration in pseudomorphs after primary stibiotantalite from the lepidolite pegmatite at Laštovičky, western Moravia, Czech Republic. Two compositionally distinct varieties of ferrotapiolite were recognized, a volumetrically dominant Fe 3+-rich phase and a very rare Sb-rich phase. Niobium-rich ferrotapiolite, with up to 17.51 wt.% Nb 2 O 5 (0.61 apfu), is highly heterogeneous, with Ta/(Ta + Nb) of 0.69 to 0.84 and Mn/(Mn + Fe) of 0.01 to 0.05; Fe 2 O 3 calc. ≤ 3.09 wt.% (0.18 Fe 3+ apfu, ~0.16 to 0.22 Fe 3+ apfu from Mössbauer spectroscopy) in the ferrian variety, and Sb 2 O 3 ≤ 9.87 wt.% (0.34 Sb 3+ apfu) in antimonoan variety. The unit-cell dimensions of ferrian ferrotapiolite (4.746 < a < 4.757 Å, 9.198 < c < 9.244 Å) calculated from X-ray powder-diffraction data indicate highly variable degrees of structural order. The substitution NbTa-1 is dominant; the minor substitution Fe 3+ 3 Fe 2+-2 R 5+-1 typical of the ferrian ferrotapiolite strongly suggests the incorporation of Fe 3+ at both the A and the B sites in ferrotapiolite, indicative of solid solution toward Fe 3+ TaO 4. The substitution Sb 3+ 3 Fe 2+-2 R 5+-1 in the antimonoan variety tends to an end-member composition of SbTaO 4 , corresponding to stibiotantalite; however, it very likely reflects microscopic relics of primary stibiotantalite in ferrotapiolite hidden below the surface of polished samples. Stibiotantalite is replaced by ferrotapiolite along irregularly distributed fractures according to the hypothetical reaction 2Sb(Ta,Nb)O 4 + Fe(OH) 2 + 2H 2 O = Fe(Ta,Nb) 2 O 6 + 2Sb(OH) 3. Such a significant Fe-enrichment (stibiotantalite versus newly formed ferrotapiolite), documented by abundant secondary ferrotapiolite at Laštovičky, is exceptional among products of secondary replacement after primary (Nb,Ta)-oxide minerals in granitic pegmatites. High Fe 2 O 3 in ferrotapiolite indicates high but variable f(O 2) during alteration. Values of Ta/(Ta + Nb) in primary stibiotantalite and secondary ferrotapiolite are virtually equal; they suggest very low mobility of both Nb and Ta. Absence of hydrothermal (fluid) fractionation of Nb from Ta in granitic pegmatites and low mobility of Ta and Nb documented here and in other studies support the importance of magmatic processes as a dominant factor in crustal fractionation of Ta from Nb.

The Canadian Mineralogist, 2012

The Virorco dumortierite-bearing pegmatite dikes, in Sierra de San Luis, Eastern Pampean Ranges o... more The Virorco dumortierite-bearing pegmatite dikes, in Sierra de San Luis, Eastern Pampean Ranges of central Argentina, are a group of thin, steeply dipping dikes one to 10 cm thick with variable lengths (a few dm to <2 m). The pegmatites are emplaced in partially uralitized norite and gabbro that belong to a larger mafic-ultramafic intrusive belt. The pegmatite dikes are symmetrically zoned, with quartz, albite, oligoclase, tourmaline-supergroup and dumortierite-group minerals, muscovite and kyanite as the major phases; the accessory and trace minerals include beryl, chrysoberyl, garnet, fluorapatite, columbite-(Mn) to tantalite-(Mn), pollucite, gahnite, zircon, uraninite and thorite. Holmquistite was found in the exocontact assemblage. Primary textures of magmatic origin were partially disrupted by partial replacements by later minerals and incipient to strong deformation. The whole-rock chemical composition of the dikes shows SiO 2 contents normal for rare-element pegmatites, whereas amounts of Al 2 O 3 and B 2 O 3 are very high. The composition features high MgO, FeO, CaO and P 2 O 5 and, for pegmatites, unusually low Na 2 O and K 2 O contents. Amounts of trace elements are remarkably high in the case of Cs (4.3-94.1 ppm), Ta (130-500) and Be (137-261). The normalized REE contents are low (0.1 to 30 times chondrite), highlighted by a strong negative Eu anomaly. Five textural and compositional types of tourmaline-supergroup minerals were identified in the different pegmatitic zones, ranging from dravite-rich compositions to rossmanite, passing through schorl and Mn-rich elbaite. At least four generations of the dumortierite-holtite minerals are texturally and compositionally represented in these dikes: the earliest dumortierite replaces muscovite and tourmaline, locally together with a second generation that grades into As-poor holtite. The third generation is represented by overgrowths or individual crystals of As-poor and As-rich holtite; it is commonly overgrown by the last generation of dumortierite enriched in As. The chemical evolution of dumortierite-group minerals is characterized by an increase of Ta, Nb and minor As, followed by an extensive enrichment in As (+ Sb + Bi) along with gradual decrease in Ta + Nb. The various assemblages and particularly the compositional trends of tourmaline, dumortierite-holtite and columbite reflect superimposed processes. The initial stage comprises the magmatic crystallization of a highly evolved and boron-rich peraluminous melt. The second stage was a prograde medium-pressure metamorphism, with a fluid-phase-related episode of crystallization. The most likely source of the initial melt is an extraction of residual melt from an almost completely crystallized rare-element parental pegmatite.

American Mineralogist, 2013

American Mineralogist, 2013

Green vesuvianite crystals occur with garnet and calcite in a hand specimen from the Nedvědice ma... more Green vesuvianite crystals occur with garnet and calcite in a hand specimen from the Nedvědice marble near Kozlov (near Štěpánov nad Svratkou, Svratka Crystalline Complex) in the Czech Republic. The average electron microprobe composition of the vesuvianite shows 12.10 wt% Fe 2 O 3 (4.66 Fe pfu), 2.77 wt% B 2 O 3 (2.45 B pfu), 1.71 wt% As 2 O 5 (0.46 As pfu), and 1.40 wt% F (2.26 F pfu). The Fe concentration is the highest ever recorded for a vesuvianite-group mineral. The boron contents are extremely variable and two of the five compositions show more than the 2.50 B pfu needed for wiluite, and the average is only slightly less than this. The crystal structure [a = 15.7250(4), c = 11.7736(3) Å] was refined in space group P4/nnc to an R 1 value of 0.0221. The site refinement and Mössbauer spectroscopy results show Fe 2+ substituting for Ca at the X3 site and filling the Y1 position, and Fe 3+ substituting for Al at the Y3 position. Most of the Fe (70% from the site refinements and 78% from the Mössbauer interpretation) is ferric. The main effect of the high-Fe concentration is to increase the mean Y3-O distance to an unusually large 2.018 Å. Boron occurs at the T1 site, where it is coordinated by oxygen atoms at two O7B and two O11 positions, and at the T2 sites where it is coordinated by O atoms at one O10 and two O12A sites. When the nearby X3 site contains Fe, the T2 position is either vacant or [3]-coordinated by some combination involving an O10 site and two O12B positions, in which case the B atom is likely offset from the T2 site to reduce the B-O12B distance. Fluorine and OH occupy the O11 positions when there is a vacancy at the adjacent T1 position. Pentavalent As substitutes for Si at the Z2 site and Al at the Y2 site. The P4/nnc symmetry indicates that this vesuvianite formed at high temperatures (400-800 °C) and the predominance of Fe 3+ and As 5+ suggests under oxidizing conditions. The results showing Fe at three different sites with three different coordinations attests to the flexibility of the vesuvianite crystal structure. The incorporation of As at two different sites in the structure shows that rock-forming silicate minerals such as vesuvianite can be a reservoir for this heavy element.

American Mineralogist, 2010

A mineral assemblage involving grandidierite, ominelite, boralsilite, werdingite, dumortierite (l... more A mineral assemblage involving grandidierite, ominelite, boralsilite, werdingite, dumortierite (locally Sb,Ti-rich), tourmaline, and corundum, along with the matrix minerals K-feldspar, quartz, and plagioclase, was found in a veinlet cutting leucocratic granulite at Horní Bory, Bory Granulite Massif, Moldanubian Zone of the Bohemian Massif. Zoned crystals of primary grandidierite to ominelite enclosed in quartz are locally overgrown by prismatic crystals of boralsilite and Fe-rich werdingite. Boralsilite also occurs as separate cross-shaped plumose aggregates with Fe-rich werdingite in quartz. Grandidierite is commonly rimmed by a narrow zone of secondary tourmaline or is partially replaced by the assemblage tourmaline + corundum ± hercynite. Grandidierite (X Fe = 0.34-0.71) exhibits dominant FeMg-1 substitution and elevated contents of Li (120-1890 ppm). Boralsilite formula ranges from Al 15.97 B 6.20 Si 1.80 O 37 to Al 15.65 B 5.29 Si 2.71 O 37 and the formula of werdingite ranges from (Fe,Mg) 1.44 Al 14.61 B 4.00 Si 3.80 O 37 to (Fe,Mg) 1.22 Al 14.86 B 4.25 Si 3.55 O 37. Dumortierite and Sb,Ti-rich dumortierite occur as zoned crystals with zones poor in minor elements (≤0.12 apfu Fe+Mg) and zones enriched in Sb (≤0.46 apfu) and Ti (≤0.25 apfu). Secondary tourmaline (X Fe = 0.44-0.75) of the schorlmagnesiofotite-foitite-olenite solid solution occurs as a replacement product of grandidierite, rarely boralsilite. Other accessory minerals in the veinlet include monazite-(Ce), ilmenite, rutile, ferberite, srilankite, löllingite, arsenopyrite, and apatite. Formation of the borosilicate-bearing veinlet postdates the development of foliation in the host granulite and is related to the decompressional process. The assemblage most probably originated from a H 2 O-poor system at T ~ 750 °C and P ~ 6-8 kbar. Textural relations as well as geological position of the borosilicate veinlet suggest that it represents the earliest intrusion related to pegmatites in the Bory Granulite Massif. Younger granitic pegmatites in the area are characterized by high contents of B, Al, P, Fe, and minor concentrations of W, Ti, Zr, Sc, and Sb. All pegmatite types probably formed within a short time period of ~5 Ma.

Goldschmidt2022 abstracts

The leucosome-hosted sapphire (corundum) occurrence near Revelstoke, British Columbia, Canada, oc... more The leucosome-hosted sapphire (corundum) occurrence near Revelstoke, British Columbia, Canada, occurs in the Monashee Complex of the Omineca Belt of the Canadian Cordillera. Corundum occurs in banded or pod-like zones within a leucosome containing muscovite + biotite + albite + orthoclase + garnet ± zircon ± sillimanite ± ilmenite ± monazite ± rutile ± Znrich spinel ± titanite. Petrography, whole rock geochemistry, zircon morphology, and thermodynamic models support an anatectic source for the leucosome. Relatively high FeO, MgO, Al 2 O 3 , CaO, and TiO 2 , and low SiO 2 and K 2 O contents of Blue Jay rocks suggest they represent restite. Numerically modeled melt compositions using the Rhyolite-MELTS software of Thor-Odin dome basement paragneiss approach the Blue Jay leucosome SiO 2 values at temperatures between 700-750 °C at 7-8 kbar, which correspond to melt-yields of ~10% melt. A calculated P-T projection using the Perple_X software indicates that the Blue Jay corundum formed at the expense of muscovite through the reaction: Ms = Crn + San + H 2 O. A pseudosection calculated using Perple_X shows that garnet equilibrated at 6-9 kbar and 650 to 750 °C in a melt bearing assemblage: staurolite + muscovite + garnet + sillimanite + ilmenite, and the corundumbearing pods were fully solidified by 2.5-5 kbar and 650-750 °C in the assemblage: plagioclase + K-feldspar + biotite + corundum + sillimanite + ilmenite. Zircon 206 Pb/ 238 U ages and trace element content indicates that corundum formed between 56 and 50 Ma.

Journal of GEOsciences, 2012

Radial aggregates of blue-grey tourmaline were found in plagioclase-muscovite-scapolite metaevapo... more Radial aggregates of blue-grey tourmaline were found in plagioclase-muscovite-scapolite metaevaporite layers in dolomite marble near Prosetín (Olešnice Unit, Moravicum, Czech Republic). It occurs in association with plagioclase (An 15-37), muscovite, scapolite, phlogopite, vermiculite, pumpellyite-(Al), and clinozoisite. Electron-microprobe analyses of tourmaline show dravitic composition with very high content of Mg (1.92 to 2.77 apfu), Al (up to 6.71 apfu), low content of Fe (up to 0.39 apfu) and variable amounts of vacancies (0.09 to 0.47) and Ca (0.03 to 0.29 apfu) in the X-site. Some analyses correspond to "oxy-dravite" and some others almost attain magnesio-foitite compositions. The proportion of X-site vacancy decreases from the crystal cores to their rims while Ca content increases. Generally, charge excess due to the high Al-contents is balanced either by an increasing X-site vacancy or by deprotonization of W OH; the W O 2content calculated from charge-balanced formula attains 0.71 apfu. Lattice parameters [a = 15.9116(6) Å; c = 7.1987(4) Å] and deduced average bond lengths ( = 1.995 Å; = 1.929 Å) indicate a relatively high Al-Mg disorder. Three main substitution mechanisms are inferred to operate in the studied magnesian tourmalines: (1) CaMg(NaAl)-1 , mainly in Ca-enriched dravite, (2) X □Al(NaMg)-1 in nearly magnesio-foititic compositions, and (3) AlO(MgOH)-1 in "oxydravitic" members. The tourmaline is relatively poor in trace elements; only Ti, Sr, and Ga exceed 100 ppm according to LA-ICP-MS study. There is a pronounced positive correlation between Sr and Ca (r 2 = 0.77), which suggests that Sr accumulated in Ca-enriched zones of dravite. The pale blue-grey color of the studied tourmalines is most likely a result of Fe 2+ crystal field transitions along with the absence of significant amounts of other chromophores. Trace-element contents, mineral assemblage and compositional zoning of tourmalines as well as host-rock mineral association suggest prograde metamorphic growth and support metaevaporitic origin of the plagioclase-muscovite-scapolite rocks.

The Canadian Mineralogist, 2014

Journal of GEOsciences, 2013

Ore Geology Reviews, 2015

The Sn-rich Qiguling topaz rhyolite dike intrudes the Qitianling biotite granite of the Nanling R... more The Sn-rich Qiguling topaz rhyolite dike intrudes the Qitianling biotite granite of the Nanling Range in southern China; the granite hosts the large Furong Sn deposit. The rhyolite dike is typically peraluminous, volatileenriched, and highly evolved. Whole-rock F and Sn concentrations attain 1.9 wt.% and 2700 ppm, respectively. The rhyolite consists of a fine-grained matrix formed by quartz, feldspar, mica and topaz, enclosing phenocrysts of quartz, feldspar and mica; it is locally crosscut by quartz veinlets. Lithium-bearing micas in both phenocrysts and the groundmass can be classified as primary zinnwaldite, "Mus-Ann" (intermediate member between annite and muscovite), and secondary Fe-rich muscovite. Topaz is present in the groundmass only; common fluorite occurs in the groundmass and also in a specific cassiterite, rutile and fluorite (Sn-Ti-F) assemblage. Cassiterite and rutile are the only Sn and Ti minerals; both cassiterite and Nb-rich rutile are commonly included in the phenocrysts. The Sn-Ti-F assemblage is pervasive, and contains spongy cassiterite in some cases; cassiterite also occurs in quartz veinlets which cut the groundmass. Electron microprobe and LA-ICP-MS compositions were used to study the magmatic and hydrothermal processes and the role of F in Sn mineralization. The presence of zinnwaldite and "Mus-Ann", which are respectively representative of early and late mica crystallization during magma differentiation, also suggests a significant decrease in f(HF)/f(H 2 O) of the system. Cassiterite included in the zinnwaldite phenocrysts is suggested to have crystallized from the primary magma at high temperature. Within the Sn-Ti-F aggregates, rutile crystallized as the earliest mineral, followed by fluorite and cassiterite. Spongy cassiterite containing inclusions of the groundmass minerals indicate a low viscosity of the late fluid. The cassiterite in the quartz veinlets crystallized from low-temperature hydrothermal fluids, which possibly mixed with meteoric water. In general, cassiterite precipitated during both magmatic and hydrothermal stages, and over a range of temperatures. The original fluorine and tin enrichments, f(HF)/f(H 2 O) change in the residual magma, formation of Ca,Sn,F-rich immiscible fluid, decrease of the f(HF) during groundmass crystallization, and mixing of magma-derived fluids with low-saline meteoric water during the late hydrothermal stage, are all factors independently or together responsible for the Sn mineralization in the Qiguling rhyolite.

Journal of GEOsciences, 2012

Clinopyroxene-garnet scheelite skarn containing accessory niobian titanite, native bismuth and Bi... more Clinopyroxene-garnet scheelite skarn containing accessory niobian titanite, native bismuth and Bi-tellurides of the Bi 2 X and Bi 5 X 3 series, together with Fe-and Fe-As sulphides, is associated with the contact of chondrodite marble with melanocratic granite-quartz syenite (durbachite). Hedenbergite-rich vein in this marble can be considered as an additional type of skarn. The presence of accessory niobian titanite is typical, in particular, of the veins. In addition to increased Nb contents (≤ 10.6 wt. % Nb 2 O 5 ; ≤ 0.164 apfu Nb) and locally Ta (≤ 4.07 Ta 2 O 5 ; ≤ 0.038 apfu Ta), it is relatively rich in Al (≤ 0.253 apfu). Locally it contains elevated Fe, Sn, Zr and F contents. Negative correlations of Al + F with R 4+ and Al + (Nb 5+ , Ta 5+) with R 4+ accompanied by low contents of Na in titanite correspond to the substitutions Al(OH,F)(TiO)-1 and Al(Nb,Ta)Ti-2. Niobian titanite has anomalous composition if compared to skarn mineral assemblages worldwide. The Bi-(sulpho-) telluride with empiric formula Bi 1.98 (Te 0.66 S 0.34 Se 0.02) Σ1.02 is a member of the Bi 2 X series, whose members were described from numerous localities as unnamed minerals. In contrast to the published data this phase contains increased sulphur contents up to 0.33 apfu. The second Bi-(sulpho-) telluride with empiric formula (Bi 4.51 Fe 0.40 Cd 0.03 Pb 0.02 Sb 0.01 As 0.01) Σ4.98 (Te 1.58 S 1.36 Se 0.08) Σ3.02 is probably a S-rich member of the Bi 5 X 3 series. In the evolution of the skarn it is possible to distinguish stage I responsible for the formation of the older Mg-and younger Ca-skarns, and stage II, characterised by increased Fe contents. The scheelite-sulphide mineralization was formed during a third (retrogression) stage followed by brittle deformation. Emplacement of siderite ± quartz veins represents the fourth (terminal) stage of mineralization.

Journal of GEOsciences, 2013

Two types of V-rich dravitic tourmaline (oxy-dravite to dravite) distinct in their color, morphol... more Two types of V-rich dravitic tourmaline (oxy-dravite to dravite) distinct in their color, morphology, paragenesis and composition from graphite quartzite at Bítovánky near Třebíč, Moldanubicum, Bohemian Massif, were studied by means of electron microprobe, laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS), and single-crystal X-ray diffraction. Green oxy-dravite (GVD) from graphite quartzite is sporadically zoned with V-enriched rims; brown oxy-dravite to dravite (BVD) from mobilized quartz-rich nests is characterized by such V-enriched rims. The formulae derived from chemical and structure data of the two oxy-dravite varieties are X (Na 0.534 Ca 0.284 □ 0.164 K 0.018) Y (Mg 1.461 V 0.679 Al 0.771 Fe 0.042 Mn 0.003 Ti 0.043) Z (Al 5.074 V 0.237 Mg 0.689) T (Si 5.782 Al 0.218 O 18) (BO 3) 3 [(OH) 3.058 O 0.75 F 0.192 ] for GVD and X (Na 0.539 Ca 0.148 □ 0.297 K 0.017) Y (Mg 0.992 V 0.302 Al 1.039 Fe 0.582 Mn 0.011 Ti 0.068 Cr 0.007) Z (Al 5.339 V 0.082 Mg 0.578) T (Si 5.864 Al 0.136 O 18) (BO 3) 3 [(OH) 3.209 O 0.621 F 0.171 ] for BVD, respectively. Both types of V-rich oxy-dravite feature Al-Mg-V disorder between the Y and Z sites; V and Cr are preferentially located at the Y site. The V-rich oxy-dravite from Bítovánky has unusually high Ca contents and high proportion of vacancy at the X site. Most common trace elements include Ti, Cr, Mn, Zn, Sc, Ga, Sr, Ni, Sn, and LREE. High concentrations of V, Cr and Ti (as well as elevated Mn, Zn, Sc, Sn, and Sr) in the GVD and late BVD most probably result from hydrothermal dissolution of (Ti,V)-oxides and other accessory phases during a high-grade metamorphic overprinting of the host graphite quartzite assemblage.

Journal of GEOsciences, 2012

Abyssal pegmatites from Starkoè and Bìstvina are typical examples of the AB-BBe subclass pegmatit... more Abyssal pegmatites from Starkoè and Bìstvina are typical examples of the AB-BBe subclass pegmatites in the Bohemian Massif. The features typical for origin and evolution of both abyssal pegmatites are better preserved in the pegmatite at Starkoè, where, based on paragenetic relationships, three distinct assemblages were recognized: (i) Primary igneous assemblage: plagioclase I + quartz I + muscovite + garnet III + tourmaline I + dumortierite I + chrysoberyl; (ii) Prograde metamorphic assemblage: quartz II + plagioclase II + kyanite + K-feldspar + staurolite + tourmaline II + dumortierite II; (iii) Retrograde metamorphic assemblage: pyrophyllite and kaolinite. Plagioclase, quartz and muscovite are major minerals in the pegmatite veinlet; the most common accessory minerals include tourmaline, dumortierite, garnet, K-feldspar and kyanite, whereas only trace amounts of chrysoberyl, staurolite and several very rare accessory minerals were found. Composition of tourmaline is controlled by the two-stage evolution of the pegmatite. Primary tourmaline I from Starkoè exhibits crystallization trend expressed by the substitution (Y,Z Al T Al)(Y,Z R 2+ T Si 4+)-1. Prograde metamorphic event introduced additional Fe and Mg from the host rock into the system and remobilization of B allowed crystallization of Mg-enriched, rather homogeneous tourmaline II. Strakoè and all other known pegmatites of AB-BBe subclass in the Bohemian Massif occur in the Gföhl Unit, along the easternmost border of the Moldanubicum. Pegmatite host rocks exhibit HP metamorphic conditions and low degree of MP overprint. Such metamorphic evolution is a typical feature of host rocks of similar abyssal pegmatites in high-grade terrains in Antarctica, Norway and Madagascar.

The Canadian Mineralogist, 2014

Mineralogy and Petrology, 2005

Elevated P contents of up to 0.086 apfu (1.21 wt.% P 2 O 5) were found in garnet from leucocratic... more Elevated P contents of up to 0.086 apfu (1.21 wt.% P 2 O 5) were found in garnet from leucocratic granitic rocks (orthogneisses, granites, barren to highly evolved pegmatites) in the Moldanubicum and Silesicum, Czech Republic, and in complex granitic pegmatites from southern California, USA, and Australia. Minor concentrations (0.15-0.55 wt.% P 2 O 5) appear ubiquitous in garnet from leucocratic granitic rocks of different origins and degrees of fractionation. Concentrations of P are not related to Mn=(Mn þ Fe) that vary from 0.12-0.86 and to textural types of garnet (i.e., isolated anhedral to euhedral grains and nodules, graphic and random garnet-quartz aggregates, subsolidus veins of fine-grained garnet). Garnet compositions exhibit negative correlations for P=Si and P=R 2þ where R 2þ ¼ Fe þ Mn þ Mg þ Ca, while Al is constant at $2.05 apfu. Concentrations of Na are largely below 0.02 apfu but positively correlate with P. The main substitution may involve A-site vacancy and=or the presence of some light element(s) in the crystal structure. The substitution &P 2 R 2þ À1 Si À2 and=or or alluaudite-type Na&P 3 R 2þ À1 Si À3 seem the most likely P-incorporating mechanisms. The partitioning of P among garnet and associated minerals in granitic systems remains unclear; however, it directly affects the distribution of Y and REEs. 206 K. Breiter et al. 208 K. Breiter et al.

Mineralogical Magazine, 2008

Euhedral crystals of complexly zoned niobian titanite (up to 0.3 mm) are enclosed in hedenbergite... more Euhedral crystals of complexly zoned niobian titanite (up to 0.3 mm) are enclosed in hedenbergite (Hd53—81Di15—43Jh3-5) and quartz from a hedenbergite vein skarn at Kamenne doly near Pisek, Czech Republic. They are associated with minor clinozoisite-epidote (Ps3—22), calcite, plagioclase (An95). scapolite (Me80—82), scheelite, pyrrhotite, fluorapatite, arsenopyrite, native bismuth and Bi,Te-minerals. The following textural and compositional subtypes were recognized: (I) Nb-rich titanite, (II) Nb-moderate titanite in the central zone, (III) Nb-poor, Sn-enriched titanite and (IV) Nb-poor, Al,F-rich titanite in the outer zone. The substitution Al(Nb,Ta)Ti—2 is dominant in subtypes I and II, the titanite subtype I being characterized by elevated contents of Al ≤ 0.257 atoms per formula unit (a.p.f.u.), Nb (≤ 0.161 a.p.f.u.) and Ta (≤ 0.037 a.p.f.u.). Amounts of Al, Nb and Ta in subtype II are smaller and more variable. The minor substitution SnTi—1 occurs chiefly in titanite subtype III...

Lithos, 2011

A peralkaline, ultrapotassic dyke found at Šebkovice (Třebíč district, western Moravia) is a mine... more A peralkaline, ultrapotassic dyke found at Šebkovice (Třebíč district, western Moravia) is a mineralogically extreme member of a dyke swarm occurring along the southeastern border of the Moldanubian Region of the Bohemian Massif. The dyke shows a simple zoning, with a very fine-grained marginal zone grading into a medium-grained central zone. It has a primary mineral assemblage of microcline and potassic amphiboles, with accessory apatite and altered phlogopite. The microcline exhibits an unusual red luminescence colour and pronounced substitution of Fe 3+ for Al, with measured contents of Fe 2 O 3 up to 8.5 wt.% (0.31 apfu Fe 3+). Amphiboles have very high K (up to 0.99 apfu) and Si contents; their compositions follow an alkaline fractionation trend from potassic-richterite to potassic-magnesio-arfvedsonite, characterized by an increase of Na/K and a decrease of Ca, Mg, Fe 2+ and Ti via heterovalent substitutions [B] Ca + [C] (Mg,Fe 2+) → [B] Na + [C] Fe 3+ and Ti +Mg → 2Fe 3+. The most evolved apatite is significantly enriched in SrO (up to 9.7 wt.%; 0.49 apfu Sr). The core of the dyke and late veinlets contain unique late-to post-magmatic Ba-Ti-Zr-bearing mineral assemblages of baotite, henrymeyerite, titanite, rutile, benitoite and bazirite. Anhedral baotite fills interstices distributed inhomogeneously in the dyke centre; it is locally replaced by a Ba-bearing titanite + henrymeyerite + rutile + quartz assemblage. Henrymeyerite (the second record in a lamproite) shows variable Fe/Ti ratios and represents a solid solution of the hepta-and hexatitanate components. Euhedral crystals of benitoite and bazirite are enclosed in the late-stage quartz-titanite-apatite veinlets in the finegrained margin of the intrusion. In terms of a mineralogical-genetic classification, the Šebkovice dyke can be considered as a new high-silica (~57 wt.% SiO 2) variety of lamproite (variety Šebkovice), and represents a unique expression of post-collisional potassic magmatism on the southeastern border of the Bohemian Massif. The peralkaline dykes from this area show mineralogical and geochemical features similar to those of silicarich orogenic lamproites emplaced at destructive plate margins. In terms of the modern classification of lamproites, the Šebkovice dyke is the first lamproite recognised in the Variscan orogenic belt.

Journal of Geochemical Exploration, 2009

Rare earth elements and yttrium geochemistry of dolomite from post-Variscan vein-type Zn-Pb-Cu mi... more Rare earth elements and yttrium geochemistry of dolomite from post-Variscan vein-type Zn-Pb-Cu mineralization was studied in the Nízký Jeseník and Upper Silesian Basins. Combined with crush-leach analyses of fluid inclusions, the study provided important information on fluid-rock interaction, physicochemical and redox conditions during crystallization of the dolomite. The mineralization is hosted by Carboniferous siliciclastic rocks, representing Variscan flysch and molasse sedimentation. Dolomite samples contain highly variable contents of REE (between 18 and 295 ppm) and Y (between 17 and 95 ppm). REY patterns are divided into four different groups which differ in regional provenance, LREE vs. HREE enrichment/depletion and significance of Eu, Gd and Y anomalies. These patterns can be the result of 1) precipitation of dolomite from near neutral fluids with important concentrations of complexing ligands as a main factor for the REY partitioning, 2) interaction of migrating fluids with host or basement rocks, or, most probably, 3) a combination of both. Regarding the importance of complexing ligands, it is proposed that in all samples fluoride and chloride complexes prevailed over sulphate, bicarbonate and hydroxide complexes. Interaction of fluids with rocks was strongly affected by the fluid temperature. Dolomites which precipitated from fluids with homogenization temperature higher than 110°C are mostly REY-enriched while fluids colder than 110°C produced REY-depleted dolomite. The REY-enrichment may indicate higher effectiveness of leaching of REEbearing minerals (probably monazite, allanite and biotite) at higher temperatures. The preferential loss of LREE can be caused by the recrystallization or remobilization of dolomite. Generally, an increase in salinity and contents of Cl and F in the fluids is mostly accompanied by a higher REY content in dolomite. Positive Eu anomalies and small negative Gd and Y anomalies are typical for most of the chondrite-normalized patterns. Positive Eu CN anomalies in dolomites are most probably the result of an increase of Eh in the parent fluid. Distribution of Y is expected to be predominantly controlled by solution complexation.

The Canadian Mineralogist, 2006

The pale blue rim of olenite on a black crystal of olenite-schorl tourmaline from an abyssal pegm... more The pale blue rim of olenite on a black crystal of olenite-schorl tourmaline from an abyssal pegmatite at the locality Kuklík, near Kutná Hora, Czech Republic, has been chemically and structurally characterized. The optimized formula, calculated using chemical and structural data, is X (Na 0.54 Ca 0.14 K 0.01 M 0.31) Y (Al 2.15 Fe 2+ 0.78 Mn 2+ 0.06 Ti 4+ 0.01) Z (Al 5.90 Mg 0.10) T (Si 5.60 Al 0.40) B 3 O 27 V [(OH) 2.49 O 0.51 ] W (O 0.99 F 0.01), with a 15.8838(3), c 7.1056(2) Å and R = 0.017. The relatively short bond-length, 1.992 Å, confirms the high content of Al at the Y site (~2.1 atoms per formula unit, apfu). It is similar to that of olenite from the type locality, though the olenite from Kuklík contains significant amounts of Fe at the Y site, and significant amounts of [4] Al (~0.4 apfu) instead of [4] B in the T site. This finding is supported by results of the structure determination, which show an enlarged bond-length of ~1.626 Å. This sample of olenite shows that nonstoichiometric content of Si does not always imply [4] B in aluminous tourmaline. No H could be found at the O1 site by refinement, and the spherical distribution of electron density in the difference-Fourier map around the O1 site supports the conclusion that this site is only or mainly occupied by O and not by OH. On a bond-angle distortion (s oct 2 of the ZO 6 octahedron)- distance diagram, the olenite from Kuklík lies between compositions containing 3 (OH) at the V site, and natural buergerite, which contains 0.3 (OH) and 2.7 O at the V site (O3 site). The (OH) content with ~2.5 (OH) pfu, which was calculated for a charge-balanced formula, is in a good agreement with these findings and with the integrated intensity of the OH overtones in the 7000 cm-1 region (690 cm-2 per cm thickness), which is one of the lowest measured to date for tourmaline. The OH seems to be ordered strongly at the O3 site. The composition of this sample of olenite shows a trend toward the proposed olenite end-member formula, which contains only 1 OH group. The low content of F (0.01 apfu) is uncommon for natural Al-rich and Mg-poor tourmaline from granitic pegmatites. Synchrotron micro-XANES was used to detect the valence state of Fe in this crystal; it was found to have 93 ± 10% of the total Fe as Fe 2+. Optical absorption spectra show that the blue color is derived primarily from a combination of [6] Fe 2+ , together with [6] Fe 2+ interaction with a minor amount of [6] Fe 3+ .

The Canadian Mineralogist, 2004

Dark brown porous ferrotapiolite is a dominant product of alteration in pseudomorphs after primar... more Dark brown porous ferrotapiolite is a dominant product of alteration in pseudomorphs after primary stibiotantalite from the lepidolite pegmatite at Laštovičky, western Moravia, Czech Republic. Two compositionally distinct varieties of ferrotapiolite were recognized, a volumetrically dominant Fe 3+-rich phase and a very rare Sb-rich phase. Niobium-rich ferrotapiolite, with up to 17.51 wt.% Nb 2 O 5 (0.61 apfu), is highly heterogeneous, with Ta/(Ta + Nb) of 0.69 to 0.84 and Mn/(Mn + Fe) of 0.01 to 0.05; Fe 2 O 3 calc. ≤ 3.09 wt.% (0.18 Fe 3+ apfu, ~0.16 to 0.22 Fe 3+ apfu from Mössbauer spectroscopy) in the ferrian variety, and Sb 2 O 3 ≤ 9.87 wt.% (0.34 Sb 3+ apfu) in antimonoan variety. The unit-cell dimensions of ferrian ferrotapiolite (4.746 < a < 4.757 Å, 9.198 < c < 9.244 Å) calculated from X-ray powder-diffraction data indicate highly variable degrees of structural order. The substitution NbTa-1 is dominant; the minor substitution Fe 3+ 3 Fe 2+-2 R 5+-1 typical of the ferrian ferrotapiolite strongly suggests the incorporation of Fe 3+ at both the A and the B sites in ferrotapiolite, indicative of solid solution toward Fe 3+ TaO 4. The substitution Sb 3+ 3 Fe 2+-2 R 5+-1 in the antimonoan variety tends to an end-member composition of SbTaO 4 , corresponding to stibiotantalite; however, it very likely reflects microscopic relics of primary stibiotantalite in ferrotapiolite hidden below the surface of polished samples. Stibiotantalite is replaced by ferrotapiolite along irregularly distributed fractures according to the hypothetical reaction 2Sb(Ta,Nb)O 4 + Fe(OH) 2 + 2H 2 O = Fe(Ta,Nb) 2 O 6 + 2Sb(OH) 3. Such a significant Fe-enrichment (stibiotantalite versus newly formed ferrotapiolite), documented by abundant secondary ferrotapiolite at Laštovičky, is exceptional among products of secondary replacement after primary (Nb,Ta)-oxide minerals in granitic pegmatites. High Fe 2 O 3 in ferrotapiolite indicates high but variable f(O 2) during alteration. Values of Ta/(Ta + Nb) in primary stibiotantalite and secondary ferrotapiolite are virtually equal; they suggest very low mobility of both Nb and Ta. Absence of hydrothermal (fluid) fractionation of Nb from Ta in granitic pegmatites and low mobility of Ta and Nb documented here and in other studies support the importance of magmatic processes as a dominant factor in crustal fractionation of Ta from Nb.

The Canadian Mineralogist, 2012

The Virorco dumortierite-bearing pegmatite dikes, in Sierra de San Luis, Eastern Pampean Ranges o... more The Virorco dumortierite-bearing pegmatite dikes, in Sierra de San Luis, Eastern Pampean Ranges of central Argentina, are a group of thin, steeply dipping dikes one to 10 cm thick with variable lengths (a few dm to <2 m). The pegmatites are emplaced in partially uralitized norite and gabbro that belong to a larger mafic-ultramafic intrusive belt. The pegmatite dikes are symmetrically zoned, with quartz, albite, oligoclase, tourmaline-supergroup and dumortierite-group minerals, muscovite and kyanite as the major phases; the accessory and trace minerals include beryl, chrysoberyl, garnet, fluorapatite, columbite-(Mn) to tantalite-(Mn), pollucite, gahnite, zircon, uraninite and thorite. Holmquistite was found in the exocontact assemblage. Primary textures of magmatic origin were partially disrupted by partial replacements by later minerals and incipient to strong deformation. The whole-rock chemical composition of the dikes shows SiO 2 contents normal for rare-element pegmatites, whereas amounts of Al 2 O 3 and B 2 O 3 are very high. The composition features high MgO, FeO, CaO and P 2 O 5 and, for pegmatites, unusually low Na 2 O and K 2 O contents. Amounts of trace elements are remarkably high in the case of Cs (4.3-94.1 ppm), Ta (130-500) and Be (137-261). The normalized REE contents are low (0.1 to 30 times chondrite), highlighted by a strong negative Eu anomaly. Five textural and compositional types of tourmaline-supergroup minerals were identified in the different pegmatitic zones, ranging from dravite-rich compositions to rossmanite, passing through schorl and Mn-rich elbaite. At least four generations of the dumortierite-holtite minerals are texturally and compositionally represented in these dikes: the earliest dumortierite replaces muscovite and tourmaline, locally together with a second generation that grades into As-poor holtite. The third generation is represented by overgrowths or individual crystals of As-poor and As-rich holtite; it is commonly overgrown by the last generation of dumortierite enriched in As. The chemical evolution of dumortierite-group minerals is characterized by an increase of Ta, Nb and minor As, followed by an extensive enrichment in As (+ Sb + Bi) along with gradual decrease in Ta + Nb. The various assemblages and particularly the compositional trends of tourmaline, dumortierite-holtite and columbite reflect superimposed processes. The initial stage comprises the magmatic crystallization of a highly evolved and boron-rich peraluminous melt. The second stage was a prograde medium-pressure metamorphism, with a fluid-phase-related episode of crystallization. The most likely source of the initial melt is an extraction of residual melt from an almost completely crystallized rare-element parental pegmatite.

American Mineralogist, 2013

American Mineralogist, 2013

Green vesuvianite crystals occur with garnet and calcite in a hand specimen from the Nedvědice ma... more Green vesuvianite crystals occur with garnet and calcite in a hand specimen from the Nedvědice marble near Kozlov (near Štěpánov nad Svratkou, Svratka Crystalline Complex) in the Czech Republic. The average electron microprobe composition of the vesuvianite shows 12.10 wt% Fe 2 O 3 (4.66 Fe pfu), 2.77 wt% B 2 O 3 (2.45 B pfu), 1.71 wt% As 2 O 5 (0.46 As pfu), and 1.40 wt% F (2.26 F pfu). The Fe concentration is the highest ever recorded for a vesuvianite-group mineral. The boron contents are extremely variable and two of the five compositions show more than the 2.50 B pfu needed for wiluite, and the average is only slightly less than this. The crystal structure [a = 15.7250(4), c = 11.7736(3) Å] was refined in space group P4/nnc to an R 1 value of 0.0221. The site refinement and Mössbauer spectroscopy results show Fe 2+ substituting for Ca at the X3 site and filling the Y1 position, and Fe 3+ substituting for Al at the Y3 position. Most of the Fe (70% from the site refinements and 78% from the Mössbauer interpretation) is ferric. The main effect of the high-Fe concentration is to increase the mean Y3-O distance to an unusually large 2.018 Å. Boron occurs at the T1 site, where it is coordinated by oxygen atoms at two O7B and two O11 positions, and at the T2 sites where it is coordinated by O atoms at one O10 and two O12A sites. When the nearby X3 site contains Fe, the T2 position is either vacant or [3]-coordinated by some combination involving an O10 site and two O12B positions, in which case the B atom is likely offset from the T2 site to reduce the B-O12B distance. Fluorine and OH occupy the O11 positions when there is a vacancy at the adjacent T1 position. Pentavalent As substitutes for Si at the Z2 site and Al at the Y2 site. The P4/nnc symmetry indicates that this vesuvianite formed at high temperatures (400-800 °C) and the predominance of Fe 3+ and As 5+ suggests under oxidizing conditions. The results showing Fe at three different sites with three different coordinations attests to the flexibility of the vesuvianite crystal structure. The incorporation of As at two different sites in the structure shows that rock-forming silicate minerals such as vesuvianite can be a reservoir for this heavy element.

American Mineralogist, 2010

A mineral assemblage involving grandidierite, ominelite, boralsilite, werdingite, dumortierite (l... more A mineral assemblage involving grandidierite, ominelite, boralsilite, werdingite, dumortierite (locally Sb,Ti-rich), tourmaline, and corundum, along with the matrix minerals K-feldspar, quartz, and plagioclase, was found in a veinlet cutting leucocratic granulite at Horní Bory, Bory Granulite Massif, Moldanubian Zone of the Bohemian Massif. Zoned crystals of primary grandidierite to ominelite enclosed in quartz are locally overgrown by prismatic crystals of boralsilite and Fe-rich werdingite. Boralsilite also occurs as separate cross-shaped plumose aggregates with Fe-rich werdingite in quartz. Grandidierite is commonly rimmed by a narrow zone of secondary tourmaline or is partially replaced by the assemblage tourmaline + corundum ± hercynite. Grandidierite (X Fe = 0.34-0.71) exhibits dominant FeMg-1 substitution and elevated contents of Li (120-1890 ppm). Boralsilite formula ranges from Al 15.97 B 6.20 Si 1.80 O 37 to Al 15.65 B 5.29 Si 2.71 O 37 and the formula of werdingite ranges from (Fe,Mg) 1.44 Al 14.61 B 4.00 Si 3.80 O 37 to (Fe,Mg) 1.22 Al 14.86 B 4.25 Si 3.55 O 37. Dumortierite and Sb,Ti-rich dumortierite occur as zoned crystals with zones poor in minor elements (≤0.12 apfu Fe+Mg) and zones enriched in Sb (≤0.46 apfu) and Ti (≤0.25 apfu). Secondary tourmaline (X Fe = 0.44-0.75) of the schorlmagnesiofotite-foitite-olenite solid solution occurs as a replacement product of grandidierite, rarely boralsilite. Other accessory minerals in the veinlet include monazite-(Ce), ilmenite, rutile, ferberite, srilankite, löllingite, arsenopyrite, and apatite. Formation of the borosilicate-bearing veinlet postdates the development of foliation in the host granulite and is related to the decompressional process. The assemblage most probably originated from a H 2 O-poor system at T ~ 750 °C and P ~ 6-8 kbar. Textural relations as well as geological position of the borosilicate veinlet suggest that it represents the earliest intrusion related to pegmatites in the Bory Granulite Massif. Younger granitic pegmatites in the area are characterized by high contents of B, Al, P, Fe, and minor concentrations of W, Ti, Zr, Sc, and Sb. All pegmatite types probably formed within a short time period of ~5 Ma.