ALBERT

Description: The [S]l[e][z]a Ophiolite is one of several thrust-bounded crustal slices dominated by metabasites in the western Sudetes. The apparent field association of serpentinites, gabbros and amphibolitic components led previous workers to consider that this lithological assemblage represented an ophiolite sequence. Fieldwork suggests that the ophiolite is now highly inclined, partly overturned, so that an ophiolitic pseudostratigraphy can be deduced, grading from serpentinites and gabbros in the south to metabasite lavas in the north. The recent discovery of pillow lava structures (at Gozdnica Hill, to the west of Sobotka town) confirms that the volcanic top of the ophiolite lies in the northern section, as might be expected from the ophiolite model. The gabbros have undergone greenschist facies metamorphism with the random development of low-grade amphibole. The volcanic portion of the sequence comprise metamorphosed dolerites and basalts partly within the contact aureole of the Variscan Strzegom-Sobotka granite. Previous work dated plagiogranites associated with the gabbros at about 400-420 Ma (U-Pb zircon ages). Geochemical data suggest that the gabbros are distinct and apparently not comagmatic with the volcanic section of sheeted dykes and lavas. The gabbros, in particular, although very depleted in incompatible elements are dissimilar to supra-subduction zone ophiolites, exhibiting instead N-MORB-like light REE depleted patterns. Depletion is both a feature of the cumulate character of many of the gabbros, as well as a source effect (especially the uniformly low Nb content). The metabasalts and metadolerites, on the other hand, are a well-evolved single comagmatic suite with high incompatible element contents, Zr/Y approximately 3-4, and generally flat to light REE-depleted patterns. The geochemical dichotomy of the plutonic and volcanic segments calls into question a simple interpretation of the body as a single-stage coherent stratiform ophiolite. Chemical comparison with Sudetic metabasites from within the nearby Rudawy-Janowickie and Kacazawa Complexes shows that the [S]l[e][z]a metabasites have a number of features in common, including the presence of both low-Ti (gabbros) and high-Ti (dykes and lavas) chemical groups. The correlation of the gabbros, dykes and lavas with the low-Ti and high-Ti (Main Series) metatholeiites respectively, seen throughout the Bohemian Massif, as well as the Sudetes, places them within the regional collage of Palaeozoic crustal blocks separated by the Saxothuringian Seaway. Comparison with Bohemian Massif metabasites also indicates that sediment contamination of the [S]l[e][z]a Ophiolite sources was not an important process and that an enriched plume source played no part in the generation of the ophiolitic melts. The two [S]l[e][z]a chemical groups were derived from variably depleted asthenospheric mantle sources. Simple modelling suggests that the volcanic segment could have been derived by 10-15% partial melting of a depleted N-MORB source, whereas the plutonic segment represents around 30% partial melting of a more depleted source. To develop varying degrees of depletion in an oceanic environment, the two sources could be related via incremental partial melting of a shallow MORB-type source.

Description: Bodies of coronitic metagabbro occur in the SW Marianske Lazn[e] Complex (MLC) and the adjacent Tepla Crystalline Unit (TCU) on the western margin of the Tepla-Barrandian Unit (TBU), Bohemian Massif. The characteristic structural, geochemical, petrographic, and metamorphic features of five groups of metagabbros and related rocks are presented, compared with other metabasites of the MLC and Zone of Erbendorff-Vohenstrauss (ZEV), and used to constrain the tectonometamorphic evolution of the western part of the TBU. The metagabbros are considered to be a younger intrusive member of the complicated lower crustal tectonic stack of Upper Proterozoic to Early Palaeozoic age which is formed by the Marianske Lazn[e] Complex and the Tepla Crystalline Unit together. It is proposed that a significant part of the metamorphic evolution of some parts of these units took place before the emplacement of metagabbros and granitoids at around 496-516 Ma. The sequence of metamorphic events is interpreted to have been as follows. Deep burial of primitive MORB type tholeiitic rocks (a) metamorphosed up to eclogite facies, followed by (b) uplift to lower crustal levels so that the partially exhumed rocks were juxtaposed with other lower/middle crustal rocks. Thermal relaxation (c) followed, with an episode of extension recorded in L-tectonites of amphibolite facies. Once this lithologically variegated stack was welded together, it was intruded by the Upper Cambrian-Lower Ordovician granitoids and gabbros (d). This pre-Variscan metamorphic event may be expressed at the supracrustal level by an unconformity between Upper Cambrian and Lower Ordovician rocks in the Barrandian. The final configuration of the units was established during the Variscan collision of the Tepla Barrandian terrane with Saxothuringia (e) in which the rocks of the MLC and TCU were thrust to the NW over the Saxothuringian para-autochthon. The accompanying metamorphic event reached upper amphibolite facies. The thermally relaxed rocks cooled rapidly, and pre-existing thrust planes were re-activated during the final extensional collapse.

Description: Moraskoite, a new natural phosphate of composition Na 2 Mg(PO 4 )F, has been found in the Morasko IAB-MG iron meteorite. The new phosphate occurs in a graphite-troilite inclusion enclosed in a kamacite-taenite matrix. Associated minerals in the inclusions are chlorapatite, buchwaldite, brianite, merrillite, a new phosphate phase of composition Na 4 MgCa 3 (PO 4 ) 4 , chromite, enstatite (bronzite), kosmochlor, kosmochlor–augite, olivine, albite, orthoclase, quartz, cohenite, schreibersite, nickelphosphide, altaite, pyrrhotite, sphalerite, daubreelite, djerfischerite, whitlockite and native Cu. The inclusions are rimmed by a schreibersite-cohenite halo. Moraskoite forms aggregates up to 1.5 mm in size, with individual grains 20–300 μm across. It is colourless and transparent, with a white streak and vitreous lustre; fluorescence is weak blue in ultraviolet radiation (254 and 360 nm); hardness is 4–5; it has irregular, conchoidal fracture and cleavage is rarely observed. Calculated density (using the empirical formula) is 2.925 g cm –3 . The moraskoite structure ( Pbcn, a = 5.2117(10), b = 13.711(3), c = 11.665(2) Å, V = 833.6(3) Å 3 and Z = 8) is similar to that of its synthetic analogue. The strongest diffraction lines of the moraskoite powder diffraction pattern are as follows ( d hkl , I ): 3.909(75), 3.382(52), 2.955(90), 2.606(100), 2.571(96), 2.545(68), 1.691 (67). In the Raman spectrum, the following characteristic bands are distinguished (cm –1 , strong bands bold): 1114 , 1027 , 962 , 589, 438, 336, 308, 279, 262, 244, 193, 184, 147 and 131. The Raman data prove the absence of H 2 O and CO 2 . Moraskoite is interpreted as being a primary phosphate, which crystallized together with graphite, troilite and other accessories inside the nodule.

Description: Sodic pyroxene is reported from an Ordovician metatrachyte of the Kaczawa Mountains, SW Poland. Its composition ranges from Jd0.98Ae0.02 to Jd0.15Ae0.85. Relict jadeite and phengite (up to 3.75 Si atoms per fomula unit) belong to the peak-pressure assemblage of an early HP-LT event. Later greenschist-facies stages are represented by riebeckite, biotite, chlorite, low-Si potassic white mica and actinolite. P-T pseudosections calculated for the range 200-450{degrees}C, 3-13 kbar allow evaluation of the conditions formation of jadeite in the metatrachyte and derivaton of a P-T path. Considering the position of prograde, peak and retrograde metamorphic assemblages and respective mineral compositions, we can derive the following equilibration stages: 8.5{+/-}0.5 kbar, 270{+/-}20{degrees}C for the pressure maximum, 6.0{+/-}1.0 kbar, 310{+/-}20{degrees}C for the temperature maximum and 3.5{+/-}0.5 kbar, 280{+/-}20{degrees}C as well as

Description: The final stages of the Variscan orogeny in Central Europe were associated with voluminous granitic plutonism and widespread volcanism. Four samples representative of the main rhyolitic volcanic units from the Stephanian–Permian continental succession of the North-Sudetic Basin, in the eastern part of the Variscan Belt, were dated using the SIMS (SHRIMP) zircon method. Three samples show overlapping 206 Pb– 238 U mean ages of 294 ± 3, 293 ± 2 and 292 ± 2 Ma, and constrain the age of the rhyolitic volcanism in the North-Sudetic Basin at 294–292 Ma. This age corresponds to the Early Permian – Sakmarian Stage and is consistent with the stratigraphic position of the lava units. The fourth sample dated at 288 ± 4 Ma reflects a minor, younger stage of (sub)volcanic activity in the Artinskian. The silicic activity was shortly followed by mafic volcanism. The rhyolite samples contained very few inherited zircons, possibly owing to limited contribution of crustal sources to the silicic magma, or owing to processes involved in anatectic melting and magma differentiation (e.g. resorption of old zircon by Zr-undersaturated melts). The SHRIMP results and the stratigraphic evidence suggest that the bimodal volcanism terminated the early, short-lived (10–15 Ma) and vigorous stage of basin evolution. The Permian volcanism in the North-Sudetic Basin may be correlated with relatively late phases of the regional climax of Late Palaeozoic volcanism in Central Europe, constrained by 41 published SHRIMP zircon age determinations at 299–291 Ma. The Permian volcanism and coeval plutonism in the NE part of the Bohemian Massif can be linked to late Variscan, post-collisional extension.

Description: The Earth has shown a systematic increase in mineral species through its history, with three ‘eras’ comprising ten ‘stages’ identified by Robert Hazen and his colleagues (Hazen et al. 2008), the eras being associated with planetary accretion, crust and mantle reworking and the influence of life, successively. We suggest that a further level in this form of evolution has now taken place of at least ‘stage’ level, where humans have engineered a large and extensive suite of novel, albeit not formally recognized minerals, some of which will leave a geologically significant signal in strata forming today. These include the great majority of metals (that are not found natively), tungsten carbide, boron nitride, novel garnets and many others. A further stratigraphic signal is of minerals that are rare in pre-industrial geology, but are now common at the surface, including mullite (in fired bricks and ceramics), ettringite, hillebrandite and portlandite (in cement and concrete) and ‘mineraloids’ (novel in detail) such as anthropogenic glass. These have become much more common at the Earth's surface since the mid-twentieth century. However, the scale and extent of this new phase of mineral evolution, which represents part of the widespread changes associated with the proposed Anthropocene Epoch, remains uncharted. The International Mineralogical Association (IMA) list of officially accepted minerals explicitly excludes synthetic minerals, and no general inventory of these exists. We propose that the growing geological and societal significance of this phenomenon is now great enough for human-made minerals to be formally listed and catalogued by the IMA, perhaps in conjunction with materials science societies. Such an inventory would enable this phenomenon to be placed more effectively within the context of the 4.6 billion year history of the Earth, and would help characterize the strata of the Anthropocene.

Description: Czochralskiite, Na 4 Ca 3 Mg(PO 4 ) 4 , is the second new phosphate mineral found in the Morasko IAB-MG iron meteorite. This very rare mineral occurs in phosphate inclusions (nodules) with graphite rims enclosed in the kamacite–taenite matrix of the meteorite. Almost thirty mineral species have been reported from this meteorite (most from various inclusions), including six, possibly eight phosphates (fluorapatite, buchwaldite, brianite, merrillite, moraskoite Na 2 Mg(PO 4 )F, chlorapatite? and whitlockite?), and schreibersite, chromite, enstatite (‘bronzite’), kosmochlor, kosmochlor–augite, olivine, albite, orthoclase, quartz, cohenite, nickelphosphide, altaite, troilite, pyrrhotite, sphalerite, daubreelite, djerfisherite, and native Cu. Czochralskiite forms xenomorphic, usually oval grains and amoeboid aggregates, between 0.1 and 0.5 mm in size. It is colourless and transparent, with white streak and vitreous lustre; it shows no fluorescence, it is biaxial (+): α = 1.608(2), β = 1.611(2), = 1.616(2); α = a , β = b , = c ; 2 V (meas.) = 70° (10), 2 V (calc.) = 76°; the dispersion is very weak; Mohs’ hardness is 4–5; the fracture is irregular, conchoidal, and no cleavage was observed. The mean of twelve electron-microprobe analyses is (wt%): P 2 O 5 46.28, CaO 27.59, Na 2 O 20.04, MgO 6.21, FeO 0.32, MnO 0.16, K 2 O 0.09, total 100.69, leading to the empirical formula Na 3.97 Ca 3.02 Mg 0.95 Mn 2+ 0.01 K 0.01 Fe 2+ 0.03 (P 4.00 O 16 ). The calculated density based on the empirical formula and the single-crystal structural data is 3.148 g · cm –3 . The structure of czochralskiite [ Pnma, a = 17.9230(2), b = 10.7280(2), c = 6.7794(1) Å, V = 1303.53(3)Å 3 , Z = 4] is of the glaserite-type and related to that of buchwaldite and brianite. The strongest diffraction lines of the calculated czochralskiite powder diffraction pattern are [ d hkl (I )]: 3.802(48), 3.728(31), 2.726(100), 2.679(63), 2.602(83), 1.901 (44). The Raman spectrum shows the following characteristic bands (cm –1 , strong bands underlined): 1119, 1167, 1053, 1039, 1022, 1011, 986 , 974 , 966 , 606, 585, 578 and 441. The Raman data show the absence of H 2 O and CO 2 . Czochralskiite is interpreted as a primary phosphate, which crystallized together with graphite and other phosphates inside the nodules. The mineral name honours Jan Czochralski (1885–1953), Polish chemist, crystallographer and metallurgist.