ALBERT

Description: A synthetic Cu-rich tourmaline crystal (Lebedev et al. 1988) consists of three different zones. Each zone was characterized by EMPA, SIMS, and single-crystal structure refinement (SREF). The first zone (which crystallized directly on the seed crystal) has the formula ~ X (Na 0.8 0.2 ) Y (Al 2.0 Cu 0.9 0.1 ) Z Al 6 T (Si 5.1 Al 0.9 )O 18 (BO 3 ) 3 V (OH) 3 W [O 0.7 F 0.2 (OH) 0.1 ] with lattice parameters a 15.835(1), c 7.093(1) Å ( R = 2.4%). The second zone has the formula ~ X (Na 0.8 0.2 ) Y (Al 1.8 Cu 1.1 0.1 ) Z Al 6 T (Si 5.1 Al 0.7 B 0.2 )O 18 (BO 3 ) 3 V (OH) 3 W [(OH) 0.4 F 0.3 O 0.3 ] with a 15.824(1), c 7.087(1) Å ( R = 2.3%). The third zone (highest Cu content with ~14 wt.% CuO) has the formula X (Na 0.81 0.19 ) Y (Cu 1.72 Al 1.21 0.07 ) Z (Al 5.96 Cu 0.04 ) (BO 3 ) 3 T (Si 5.17 Al 0.48 B 0.35 )O 18 V (OH) 3 W [(OH) 0.63 F 0.37 ] with a 15.849(1), c 7.087(1) Å ( R = 2.5%). While [4] Al decreases from zone 1 to zone 3, [4] B increases (by chemistry and SREF), which could be explained by a decreasing temperature during tourmaline crystallization. Such a T -site occupancy is in agreement with the 〈 T –O〉 distance, which strictly monotonically decreases from 1.625(1) to 1.616(1) Å. We suggest that very small amounts of Cu are present at the Z site of all investigated tourmaline samples, but only in the Cu-richest zone (~14 wt.% CuO) is the refined value for Cu at the Z site (~1% of the total Cu) higher than the 3 error. The Y O 6 octahedron of this Cu-richest known tourmaline is mainly occupied by Cu. Two of the six ( Cu ,Al)–O distances are significantly enlarged: Y –O1 with 2.031(2) Å and Y –O3 with 2.170(2) Å, while the other distances Y –O2 and Y –O6 with ~1.951(2) Å are significantly smaller. The proportion of the average of the two enlarged distances to the average of the other distances in the Cu-richest zone gives a value of ~1.08, which is the highest value known so far for Cu-bearing tourmalines. We conclude that for the Cu-richest zone the Jahn-Teller effect appears to be verified.

Description: Synthetic Al- and B-rich tourmaline crystals described by London (2011) were characterized further by SIMS and new EMP analyses. These tourmalines are the first synthetic B-rich olenites characterized by single-crystal X-ray diffraction, because they are significantly larger than synthetic samples produced in the past. The average final formulas are X (Na 0.7 0.3 ) Y (Al 2.5 Li 0.4 Fe 2+ 0.1 ) Z Al 6 (BO 3 ) 3 [Si 5.2 B 0.5 Al 0.3 O 18 ] V [(OH) 2.9 O 0.1 ] W [O 0.9 (OH) 0.1 ], with a = 15.765(1), c = 7.083(1) Å, X (Na 0.7 0.3 ) Y (Al 2.5 Li 0.5 ) Z Al 6 (BO 3 ) 3 [Si 4.8 B 0.9 Al 0.3 O 18 ] V (OH) 3 W [(OH) 0.5 O 0.5 ], with a = 15.746(1), c = 7.075(1) Å, and X (Na 0.6 Ca 0.1 0.3 ) Y (Al 2.3 Li 0.5 Fe 0.2 ) Z Al 6 (BO 3 ) 3 [Si 4.7 B 1.2 Al 0.2 O 18 ] V (OH) 3 W [(OH) 0.9 O 0.1 ], with a = 15.723(1), c = 7.068(1) Å. The small 〈T-O〉 distances, down to 1.599 Å, reflect relatively high amounts of [4] B (up to ~1.2 apfu; refinements with R = ~2%). All these samples also contain significant amounts of [4] Al (~0.2 apfu). A pronounced negative correlation ( r 2 = 1.00; only three data points) between temperature during crystal growth (at a constant pressure) and [4] B (from refinement) in these synthetic olenites was found.

Description: The H.U. Sverdrupfjella is part of the high-grade Maud Belt in Dronning Maud Land (East Antarctica), which was located in a central position of the Gondwana supercontinent. Here we study high-pressure granulites from the eastern H.U. Sverdrupfjella and present a detailed reconstruction of the P–T–t history based on a combination of Zr-in-rutile and Ti-in-zircon thermometry, zircon U–Pb dating, monazite chemical dating, garnet diffusion modelling and petrological modelling. Peak metamorphic conditions of ~930°C and 1·45 GPa persisted for less than 6 Myr and were attained at 570 ± 7 Ma, embedded in a well-documented clockwise loading, heating, and decompression path. The rocks had already been rapidly exhumed to a crustal depth of ~30 km at 556 ± 7 Ma. In addition to the very short-lived ultrahigh-temperature peak, zircon preserves evidence for protracted granulite-facies conditions with temperatures above 800°C from as early as c. 590 Ma, persisting for c. 40 Myr. Constraints on prograde metamorphism are recorded in zircon and in rutile inclusions in garnet. Zr-in-rutile thermometry using rutile included in different generations of garnet is used to reconstruct the prograde P–T path, documenting burial followed by heating to ultrahigh temperatures at peak pressures. Complementary Ti zonation in prograde cores of zircon grains documents and dates heating and peak temperatures, whereas younger zircon rims show lower Ti-in-zircon temperatures and date the retrograde stages of metamorphism. Our results provide the first evidence for Neoproterozoic high-pressure granulite-facies metamorphism and ultrahigh-temperature conditions for this region. The clockwise loading–heating path and the peak P–T conditions strongly indicate that the rocks preserved in Dronning Maud Land were part of the lower plate during a continent–continent collision event related to Gondwana assembly at c. 570 Ma. The metamorphic evolution determined in this study and the correlation with similar P–T evolutions documented in adjacent terranes favour the continuation of the c. 580–560 Ma Mozambique Belt into Dronning Maud Land. Furthermore, the striking contemporaneity of the metamorphism in the different parts of central Gondwana suggests that the Coats Land Block was part of greater India prior to this collision.

Description: Fluor-schorl, NaFe 2+ 3 Al 6 Si 6 O 18 (BO 3 ) 3 (OH) 3 F, is a new mineral species of the tourmaline supergroup from alluvial tin deposits near Steinberg, Zschorlau, Erzgebirge (Saxonian Ore Mountains), Saxony, Germany, and from pegmatites near Grasstein (area from Mittewald to Sachsenklemme), Trentino, South Tyrol, Italy. Fluor-schorl was formed as a pneumatolytic phase and in high-temperature hydrothermal veins in granitic pegmatites. Crystals are black (pale brownish to pale greyish-bluish, if 〈0.3 mm in diameter) with a bluish-white streak. Fluor-schorl is brittle and has a Mohs hardness of 7; it is non-fluorescent, has no observable parting and a poor/indistinct cleavage parallel to {0001}. It has a calculated density of ~3.23 g/cm 3 . In plane-polarized light, it is pleochroic, O = brown to grey-brown (Zschorlau), blue (Grasstein), E = pale grey-brown (Zschorlau), cream (Grasstein). Fluor-schorl is uniaxial negative, = 1.660(2)–1.661(2), = 1.636(2)–1.637(2). The mineral is rhombohedral, space group R 3 m, a = 16.005(2), c = 7.176(1) Å, V = 1591.9(4) Å 3 (Zschorlau), a = 15.995(1), c = 7.166(1) Å, V = 1587.7(9) Å 3 (Grasstein), Z = 3. The eight strongest observed X-ray diffraction lines in the powder pattern [ d in Å ( I ) hkl ] are: 2.584(100)(051), 3.469(99)(012), 2.959(83)(122), 2.044(80)(152), 4.234(40)(211), 4.005(39)(220), 6.382(37)(101), 1.454(36)(514) (Grasstein). Analyses by a combination of electron microprobe, secondary-ion mass spectrometry (SIMS), Mössbauer spectroscopic data and crystal-structure refinement result in the structural formulae X (Na 0.82 K 0.01 Ca 0.01 0.16 ) Y (Fe 2+ 2.30 Al 0.38 Mg 0.23 Li 0.03 Mn 2+ 0.02 Zn 0.01 0.03 ) 3.00 Z (Al 5.80 Fe 3+ 0.10 Ti 4+ 0.10 ) T (Si 5.81 Al 0.19 O 18 ) (BO 3 ) 3 V (OH) 3 W [F 0.66 (OH) 0.34 ] (Zschorlau) and X (Na 0.78 K 0.01 0.21 ) Y (Fe 2+ 1.89 Al 0.58 Fe 3+ 0.13 Mn 3+ 0.13 Ti 4+ 0.02 Mg 0.02 Zn 0.02 0.21 ) 3.00 Z (Al 5.74 Fe 3+ 0.26 ) T (Si 5.90 Al 0.10 O 18 ) (BO 3 ) 3 V (OH) 3 W [F 0.76 (OH) 0.24 ] (Grasstein). Several additional, newly confirmed occurrences of fluor-schorl are reported. Fluor-schorl, ideally NaFe 2+ 3 Al 6 Si 6 O 18 (BO 3 ) 3 (OH) 3 F, is related to end-member schorl by the substution F -〉 (OH). The chemical compositions and refined crystal structures of several schorl samples from cotype localities for schorl (alluvial tin deposits and tin mines in the Erzgebirge, including Zschorlau) are also reported. The unit-cell parameters of schorl from these localities are slightly variable, a = 15.98–15.99, c = 7.15–7.16 Å, corresponding to structural formulae ranging from ~ X (Na 0.5 0.5 ) Y (Fe 2+ 1.8 Al 0.9 Mg 0.2 0.1 ) Z (Al 5.8 Fe 3+ 0.1 Ti 4+ 0.1 ) T (Si 5.7 Al 0.3 O 18 ) (BO 3 ) 3 V (OH) 3 W [(OH) 0.9 F 0.1 ] to ~ X (Na 0.7 0.3 ) Y (Fe 2+ 2.1 Al 0.7 Mg 0.1 0.1 ) Z (Al 5.9 Fe 3+ 0.1 ) T (Si 5.8 Al 0.2 O 18 ) (BO 3 ) 3 V (OH) 3 W [(OH) 0.6 F 0.4 ]. The investigated tourmalines from the Erzgebirge show that there exists a complete fluor-schorl–schorl solid-solution series. For all studied tourmaline samples, a distinct inverse correlation was observed between the X –O2 distance (which reflects the mean ionic radius of the X -site occupants) and the F content ( r 2 = 0.92). A strong positive correlation was found to exist between the F content and the 〈 Y –O〉 distance ( r 2 = 0.93). This correlation indicates that Fe 2+ -rich tourmalines from the investigated localities clearly tend to have a F-rich or F-dominant composition. A further strong positive correlation ( r 2 = 0.82) exists between the refined F content and the Y–W (F,OH) distance, and the latter may be used to quickly estimate the F content.

Description: Crystal structures, chemical (including light elements) and spectral data (optical and Mössbauer spectroscopies) were used to characterize coloured (brown, pink, green) tourmalines from three granitic pegmatites from the Moldanubian nappes (Königsalm, Maigen and Blocherleitengraben; Lower Austria). The tourmalines can be classified as fluor-schorl, schorl, foitite, magnesiofoitite, olenite and "fluor-elbaite" with varying Li contents, up to ~1.2 wt% Li 2 O. Coexisting minerals are quartz, plagioclase (up to An 7 ), microcline, garnet (spessartine-almandine), muscovite, biotite (annite), very rare lepidolite, apatite, monazite-(Ce), xenotime-(Y), allanite-(Ce) and zircon. The chemical composition of the Fe 2+ -rich tourmaline samples (up to ~1.0 wt% TiO 2 ) varies from fluor-schorl, with a = 15.987(2), c = 7.163(2) Å to X ( 0.63 Na 0.37 ) Y (Fe 2+ 1.12 Al 1.09 Mg 0.56 Mn 2+ 0.08 Fe 3+ 0.07 Li 0.02 Ti 4+ 0.01 Zn 0.01 0.04 ) Z (Al 5.74 Mg 0.26 ) (BO 3 ) 3 [Si 5.96 Al 0.04 O 18 ] V (OH) 3 W [(OH) 0.95 F 0.05 ], strongly dichroic (pink and blue) foitite, with a = 15.9537(2), c = 7.1448(4) Å, to X ( 0.51 Na 0.49 ) Y (Fe 2+ 0.97 Al 0.93 Mg 0.75 Fe 3+ 0.23 Mn 2+ 0.04 Li 0.01 Ti 4+ 0.01 0.06 ) Z (Al 5.72 Mg 0.28 ) (BO 3 ) 3 [Si 5.95 Al 0.05 O 18 ] V (OH) 3 W [(OH) 0.91 O 0.06 F 0.03 ], magnesiofoitite, with a = 15.9476(4), c = 7.1578(4) Å. The chemical composition of the Al- and Li-rich and Mn 2+ -bearing (up to ~5.7 wt% MnO) samples varies from X (Na 0.84 Ca 0.02 0.14 ) Y (Al 1.35 Li 0.78 Mn 2+ 0.65 Ti 4+ 0.01 0.21 ) Z Al 6 (BO 3 ) 3 [Si 5.92 Al 0.04 B 0.04 O 18 ] V (OH) 3 W [F 0.81 (OH) 0.19 ], "fluor-elbaite" with a = 15.8887(3), c = 7.1202(3) Å, to X (Na 0.76 Ca 0.12 0.12 ) Y (Al 1.52 Li 0.69 Mn 2+ 0.43 Fe 2+ 0.09 0.27 ) Z Al 6 (BO 3 ) 3 [Si 5.71 B 0.29 O 18 ] V (OH) 3 W [F 0.69 (OH) 0.31 ], B-rich "fluorelbaite", with a = 15.8430(3), c = 7.1051(3) Å. A positive correlation between the 〈 T -O〉 and 〈 Z -O〉 bond lengths in tourmalines where the Z site is only occupied by Al ( R 2 = 0.617) is useful to correct the 〈 Z -O〉 bond length for the inductive effect of the varying 〈 T -O〉 bond length. This is important for producing accurate assignments for the different 6-coordinated sites in tourmaline. On the basis of Sm-Nd (garnet, monazite), U-Th-Pb, and U-Pb ages (monazite), the pegmatites crystallised during the Variscan tectonometamorphic event in the Visean (339 ± 4 Ma Maigen, 332 ± 3 Ma Königsalm). These ages are in the range of the earliest intrusions of the South Bohemian pluton (Rastenberg type durbachites). However, on the basis of the spatial relationship of the pegmatites and the Rastenberg type intrusions, a linkage of the intrusive body and the pegmatites is unlikely. Alternatively, the pegmatites may have evolved as granitic pegmatitic melts during decompression from the surrounding country rocks in the frame of exhumation of the Moldanubian nappes after the peak of the Variscan metamorphism.

Description: A new occurrence of ardennite near Vitolište in the southernmost Republic of Macedonia (FYROM) is described. In the westernmost Vardar zone, a high- P / T metamorphic conglomerate contains reddish clasts (up to 20–30 vol% of the rock) that consist of quartz, hematite, ardennite, pyrophyllite, sudoite, cookeite, phengite rimmed by muscovite, epidote/piemontite, lawsonite, tourmaline, titanite, albite, apatite and ±rutile. Epidote may contain inclusions of pumpellyite–(Fe 2+ ) and is partially transformed to piemontite. Ardennite is generally poor in As and its composition essentially follows the T4 exchange vector (Si + Al + P) –1 V, whereby Al and P are relatively low. Three compositional types of ardennite can be distinguished: ardennite-(V), ‘ardennite-(V,Si)’ and ‘ardennite-(Si)’, the latter possibly representing lavoisierite inter- and overgrowths. Metamorphic conditions of 0.65–0.80 GPa and 340–370 °C are deduced. The reddish Fe–Mn–(V–As)-rich detritus may have originated from a hydrothermal Fe–Mn deposit or, more likely, from a nickel–laterite deposit developed from weathered ophiolites. Such laterites and bauxites resulted from redeposition of ophiolite material in shallow seawater during the Lower Cretaceous.