Four isolated occurrences of Tertiary volcanic rocks in the northern Spessart at Beilstein, Hoher Berg, Madstein and Kasselgrund are relics of volcanic vents or dikes. They display alkaline basalts (s.l.) with mainly trachybasaltic composition, which, from nonnative mineral contents, may be designated as nepheline-bearing alkali-olivine basalts and basanites. In part, centimetre-sized xenoliths of spinel lherzolite occur. According to Ar-Ar dating, the alkaline basalts (s.l.) from Kasselgrund have erupted at 18.1 +/- 0.3 or 19.3 +/- 0.4 Ma, those of Hoher Berg between c. 18 and c. 21 Ma. These ages correspond to the Vogelsberg eruption stage I.A slightly younger Ar-Ar age of 16.8 +/- 0.3 Ma was recorded for the Beilstein basalt, which is in chronological accordance to the turn of Vogelsberg eruption stages II and III. Samples of all four occurrences reveal major and trace element compositions, which are different from those of the Vogelsberg basalts. Compositions of basalts of the stage III from Vogelsberg coincide most with the Spessart basalts. This signals a special position of the northern Spessart volcanic rocks either as a discrete spatial part of the Vogelsberg volcanic suite or as smaller, independent eruption centres.

Imperial Porphyry, a famous dimension stone of spectacular purple color, was quarried in the Mons Porphyrites area north of Jabal Dokhan in the Eastern Desert of Egypt, from the beginning of the first until the middle of the fifth century AD. During this period, the valuable material was processed as decorative stone and was used for objects of art, reserved exclusively for the Imperial court of the Roman Empire. Later on, only antique spoils of smaller or bigger size have been re-used for these purposes. The Imperial Porphyry is a porphyritic rock of trachyandesitic to dacitic composition that occurs in the uppermost levels of shallow subvolcanic sill-like intrusions, forming a member of the Dokhan Volcanic Suite. Its purple color is mainly due to dispersed flakes of hematite, resulting from hydrothermal alteration of a dark green Common Porphyry of similar composition, underlying the Imperial Porphyry. Both, the Common Porphyry and the purple Imperial Porphyry’, are extensively exposed in the Roman quarries. Contacts between Common and Imperial Porphyry are irregular and gradational. In both rock types, intrusive breccias are frequent, indicating a complex intrusion history. U–Th–Pb zircon geochronology on two samples of Imperial Porphyry and one sample of the Common Porphyry yielded an age range of 609–600 Ma, thus confirming earlier results of radiometric dating. Geochemical evidence indicates that both the Imperial and the Common Porphyry are of medium- to high-K calc-alkaline affinity. The magmas have formed by partial melting of a subduction-modified upper mantle. The subsequent intrusion took place within a highly extended terrane (HET).

Stratigraphically well-defined volcanic rocks in Palaeozoic volcano-sedimentary units of the Frankenwald area (Saxothuringian Zone, Variscan Orogen) were sampled for geochemical characterisation and U–Pb zircon dating. The oldest rock suite comprises quartz keratophyre, brecciated keratophyre, quartz keratophyre tuff and basalt, formed in Upper Cambrian to Tremadocian time (c. 497–478 Ma). Basaltic volcanism continued until the Silurian. Quartz keratophyre shows post-collisional calc-alkaline signature, the Ordovician–Silurian basalt has alkaline signature typical of continental rift environments. The combined datasets provide evidence of Cambro-Ordovician bimodal volcanism and successive rifting until the Silurian. This evolution very likely resulted from break-up of the northern Gondwana margin, as recorded in many terranes throughout Europe. The position at the northern Gondwana margin is supported by detrital zircon grains in some tuffs, with typical Gondwana-derived age spectra mostly recording ages of 550–750 Ma and minor age populations of 950–1100 and 1700–2700 Ma. The absence of N-MORB basalt in the Frankenwald area points to a retarded break-off of the Saxothuringian terrane along a continental rift system from Uppermost Cambrian to Middle Silurian time. Geochemical data for a second suite of Upper Devonian basalt provide evidence of emplacement in a hot spot-related ocean-island setting south of the Rheic Ocean. Our results also require partial revision of the lithostratigraphy of the Frankenwald area. The basal volcanic unit of the Randschiefer Formation yielded a Tremadocian age and, therefore, should be attributed to the Vogtendorf Formation. Keratophyre of the Vogtendorf Formation, previously assigned to the Tremadoc, is most likely of Upper Devonian age.

The Münchberg Massif in northeastern Bavaria, Germany is an allochthonous metamorphic nappe complex within the Saxothuringian Zone of the Variscan orogen. From top to bottom it consists of four major units: Hangend-Serie, Liegend-Serie, Randamphibolit-Serie and Prasinit-Phyllit-Serie, which show an inverted metamorphic gradient of eclogite- to amphibolite-facies (top) to greenschist-facies (bottom) and are separated from each other by thrust faults. New geochemical and U-Pb zircon data indicate that the four units host metasedimentary and meta-igneous rocks, which were formed at different time and in distinct geotectonic settings during the evolution of the Saxothuringian terrane between 550 and 370Ma. Mafic and felsic protoliths of the Hangend-Serie result from a bimodal magmatism in an evolved oceanic to continental magmatic arc setting at about 550Ma. These rocks represent relics of the Cadomian magmatic arc, which formed a cordillera at the northern margin of Gondwana during the Neoproterozoic. The Liegend-Serie hosts slivers of granitic orthogneisses, emplaced during magmatic events at c. 505 and 480Ma, and Early Palaeozoic paragneisses, with our samples deposited at ≤483Ma. Ortho- and paragneisses were affected by an amphibolite-facies metamorphic overprint at c. 380Ma. Granite emplacement and sediment deposition can be related to the separation of the Avalonia microterrane from the northern Gondwana margin. Amphibolite protoliths of the Randamphibolit-Serie emplaced at c. 400Ma. They show N-MORB to E-MORB signatures, pointing to their formation along an oceanic spreading centre within the Rheic ocean. Mafic igneous rocks in the Prasinit-Phyllit-Serie emplaced at nearly the same time (407–401Ma), but their calc-alkaline to tholeiitic character rather suggests formation in an intra-oceanic island arc/back arc system. This convergent margin lasted for about 30Ma until the Late Devonian, as is suggested by a maximum deposition age of 371Ma of associated phyllites, and by metamorphic Ar-Ar ages of 374–368Ma. The timing of the different magmatic and sedimentary events in the Münchberg Massif and their plate tectonic settings are similar to those estimated for other Variscan nappe complexes throughout Europe, comprising the French Massif Central and NW Spain. This similarity indicates that the Münchberg Massif forms part of an European-wide suture zone, along which rock units of different origin were assembled in a complex way during the Variscan Orogeny.

Copper-bearing tourmalines are highly prized for their vivid coloration. We analysed the major and trace elements of some gem-quality Cu-bearing tourmalines (e.g. blue, greenish blue, yellowish green, green, violet and pink) from Brazil, Mozambique and Nigeria. Most of them contained significant amounts of Cu, Mn or a combination of both elements. There was no clear-cut correlation of the Cu and Mn contents with coloration. Blue colour was in most cases due to Cu2+. Pink and violet coloration (due to Mn3+) was shown by Mn-bearing tourmalines that contained no significant Fe. Green colour in the Nigerian tourmaline was most probably due to a combination of Mn, Cu and Fe. Some of the green samples from Brazil contained up to 0.6 wt.% V2O3. Among the trace elements, remarkable contents of Pb (up to 4,000 ppm) and Bi (up to 2,900 ppm) were detected rarely in samples from all three countries. Based on a comparison of unheated pink and violet samples with data for blue Paraiba-type tourmalines, CuO/MnOtot is usually >= 0.5 for unheated blue samples. Hence, we suggest that blue Cu-bearing tourmalines with CuO/MnOtot <0.5 may have been heat treated to reduce the contribution of the reddish component of Mn3+. (C) 2016 The Gemmological Association of Great Britain

The distinction between regional metamorphic and metasomatic mineral assemblages may be occasionally challenging when the two phenomena show a very close spatial and temporal association. The Khetri complex in NW India, provides an excellent example of a geological terrane that has been significantly affected by metamorphism followed by extensive metasomatism. The albitic quartzite, orthoamphibole-cordierite quartzite and chlorite metapelite in northern Khetri complex are the outcome of Na-Cl-Fe-Mg metasomatism. The andalusite metapelite and associated scapolite-bearing metasediments, however, do not show any significant metasomatic overprint, and the former rock unit has been used to deduce the metamorphic conditions, nature of provenance and weathering processes. The peak P-T conditions inferred from the conventional geothermobarometry and pseudosection modelling are consistent at 550 degrees C and 3.5 kbar. The geochemical data suggest that the source rocks of the metapelites were compositionally mature and experienced intense chemical weathering in a passive margin setting. The metasomatic overprint postdates the regional metamorphism and, the new monazite U-Th-Pb age data constrains the age of metasomatism at 900-850 Ma and that of the regional metamorphism at ca. 975 Ma in the Khetri complex. (C) 2016 Elsevier Ltd. All rights reserved.

Electron microprobe and laser ablation-inductively coupled plasma mass spectrometric (LA-ICPMS) analyses were carried out on individual uraninite grains from several localities worldwide, representing a variety of different U-deposit types ranging in age from Mesoarchaean to the Mesozoic. For the first time, concentration data on a comprehensive set of minor/trace elements in uraninite are presented, i.e. LA-ICPMS concentration data for Th, Si, Al, Fe, Mn, Ca, Mg, P, Ti, V, Cr, Co, Ni, Pb, Zn, As, rare earth elements (REE), Y, Zr, Nb, Mo, Ag, Ta, W, Bi, and Au. Most of these elements could be detected in significant quantities in many of the studied examples. The results obtained in this study, supplemented by previously published data on major element and REE concentrations, reveal systematic differences in uraninite composition between genetically different deposit types and also, for a given genetic type, between different locations.Low-temperature hydrothermal uraninite is marked by U/Th >1000, whereas high-temperature metamorphic and magmatic (granitic, pegmatitic) uraninite has U/Th <100. Our new data also confirm previous observations that low-temperature, hydrothermal uraninite has low total REE contents (<1 wt%) whereas higher temperature uraninite can contain as much as several percent total REE. Genetically different uraninite types can be further identified by means of different REE fractionation patterns. Systematic differences between primary uraninite from different localities could be also noted with respect to the abundances of especially Y, V, W, Zr, Nb, Ta, and to a lesser extent Mo, P, Bi, and As. Our findings open up the possibility of using uraninite chemistry as provenance tool, both for geological applications, as exemplified in this study by the application to uraninite in the Mesoarchean Witwatersrand Basin (South Africa), as well as for forensic purposes to track down the likely source of illegally mined uraninite. Uraninite chemistry provides strong support for a palaeoplacer model for the U-mineralisation in the auriferous and uraniferous conglomerates of the Witwatersrand, in which individual uraninite particles display chemical characteristics typical of high-temperature (magmatic) uraninite and a great variation in trace element concentrations that point to a variety of (magmatic) source rocks. (C) 2014 Elsevier Ltd. All rights reserved.

Base-metal sulfides in magmatic Ni-Cu-PGE deposits are important carriers of platinum-group elements (PGE). The distribution and concentrations of PGE in pentlandite, pyrrhotite, chalcopyrite, and pyrite were determined in samples from the mineralized portion of four Merensky Reef intersections from the eastern and western Bushveld Complex. Electron microprobe analysis was used for major elements, and in situ laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) for trace elements (PGE, Ag, and Au). Whole rock trace element analyses were performed on representative samples to obtain mineralogical balances. In Merensky Reef samples from the western Bushveld, both Pt and Pd are mainly concentrated in the upper chromitite stringer and its immediate vicinity. Samples from the eastern Bushveld reveal more complex distribution patterns. In situ LA-ICP-MS analyses of PGE in sulfides reveal that pentlandite carries distinctly elevated PGE contents, whereas pyrrhotite and chalcopyrite only contain very low PGE concentrations. Pentlandite is the principal host of Pd and Rh in the ores. Palladium and Rh concentrations in pentlandite reach up to 700 and 130 ppm, respectively, in the samples from the eastern Bushveld, and up to 1,750 ppm Pd and up to 1,000 ppm Rh in samples from the western Bushveld. Only traces of Pt are present in the base-metal sulfides (BMS). Pyrrhotite contains significant though generally low amounts of Ru, Os, and Ir, but hardly any Pd or Rh. Chalcopyrite contains most of the Ag but carries only extremely low PGE concentrations. Mass balance calculations performed on the Merensky Reef samples reveal that in general, pentlandite in the feldspathic pyroxenite and the pegmatoidal feldspathic pyroxenite hosts up to 100 % of the Pd and Rh and smaller amounts (10–40 %) of the Os, Ir, and Ru. Chalcopyrite and pyrrhotite usually contain less than 10 % of the whole rock PGE. The remaining PGE concentrations, and especially most of the Pt (up to 100 %), are present in the form of discrete platinum-group minerals such as cooperite/braggite, sperrylite, moncheite, and isoferroplatinum. Distribution patterns of whole rock Cu, Ni, and S versus whole rock Pd and Pt show commonly distinct offsets. The general sequence of “offset patterns” of PGE and BMS maxima, in the order from bottom to top, is Pd in pentlandite → Pd in whole rock → (Cu, Ni, and S). The relationship is not that straightforward in general; some of the reef sequences studied only partially show similar trends or are more complex. In general, however, the highest Pd concentrations in pentlandite appear to be related to the earliest, volumetrically rather small sulfide liquids at the base of the Merensky Reef sequence. A possible explanation for the offset patterns may be Rayleigh fractionation.

The distribution of mineral deposits, characterised as barite deposits, hematite-rich auriferous deposits and auriferous tourmaline–sulfide deposits, displays a regional sulfate–hematite–sulfide zoning along the thrust-delineated limbs of the Mariana anticline, in the south-eastern part of the Quadrilátero Ferrífero of Minas Gerais, Brazil. Cross-cut relationships of barite veins and sulfide lodes indicate that sulfidation occurred in a late-tectonic context, which is here attributed to the collapse of the ∼0.6-Ga Brasiliano thrust front. Reconnaissance S-isotopic data from barite and pyrite (Antônio Pereira barite deposit and its adjacent gold deposit, respectively), and arsenopyrite (Passagem de Mariana gold deposit), suggest a new interpretation for the hydrothermal fluid overprint in the Mariana anticline. The Antônio Pereira barite has Δ33S values that are near zero, constraining the sulfate source to rocks younger than 2.45 Ga. The barite-δ34S values are between +19.6 and +20.8 ‰. The Passagem arsenopyrite and tourmaline have Co/Ni ratios that define a positive linear trend with the Antônio Pereira pyrite. The latter has homogenous δ34S values, between +8.8 and +8.9 ‰, which are compatible with thermochemical reduction of aqueous sulfate with the S-isotopic composition of the Antônio Pereira barite.

Cu- and Mn-bearing tourmalines from Brazil and Mozambique were characterised chemically (EMPA and LA-ICP-MS) and by X-ray single-crystal structure refinement. All these samples are rich in Al, Li and F (fluor-elbaite) and contain significant amounts of CuO (up to ~1.8 wt%) and MnO (up to ~3.5 wt%). Structurally investigated samples show a pronounced positive correlation between the distances and the (Li + Mn2+ + Cu + Fe2+) content (apfu) at this site with R 2 = 0.90. An excellent negative correlation exists between the distances and the Al2O3 content (R 2 = 0.94). The samples at each locality generally show a strong negative correlation between the X-site vacancies and the (MnO + FeO) content. The Mn content in these tourmalines depends on the availability of Mn, on the formation temperature, as well as on stereochemical constraints. Because of a very weak correlation between MnO and CuO we believe that the Cu content in tourmaline is essentially dependent on the availability of Cu and on stereochemical constraints.

Results of measurements on gypsum for gold (Au) and uranium (U) using laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) are reported. The Au contents were mostly below the average detection limit of 0.07 mu g/g, with a maximum value of 0.20 mu g/g Au, whereas the U concentrations vary from 0.04 to 1.82 mu g/g. The gypsum formed from the weathering of auriferous pyrite in a Witwatersrand-like gold deposit, Ouro Fino, Minas Gerais, Brazil. The pyrite exposed along exploration adits was extensively dissolved in about 25 years by percolating ground water. The LA-ICPMS results indicate that gold has not followed the sulfate pathway during the weathering of auriferous pyrite. Compared to gypsum from continental evaporitic environments, the Ouro Fino gypsum shows some enrichment in U, which likely reflects its uraniferous Witwatersrand-like setting.

Ferroselite from Trogtal, the type locality of the cobalt selenide trogtalite, in the Harz Mountains, Germany, forms a trogtalite-ferroselite assemblage in pockets of massive clausthalite in which specular hematite is dispersed. The pockets occur in hematite-impregnated carbonate veins, emplaced in a reddened greywacke of Lower Carboniferous age. Ferroselite contains similar to 0.2- 5.0 ppm Au; trogtalite has even higher Au contents. Ferroselite has Co/Ni ratios mostly above unity. These characteristics likely reflect oxidizing brines with Co/Ni > 1, such as those involved in the formation of sediment-hosted copper deposits.

Enrichments in platinum-group elements were found in clausthalite, PbSe, which occurs in carbonate–hematite veins hosted in black shale of Upper Wenlockian age in the eastern Harz, Germany. Spot measurements by laser ablation–quadrupole inductively coupled plasma mass spectrometry (LA–QICPMS) show that the clausthalite has Pt contents that average 0.459 ppm and range from 0.003 to 2.83 ppm. Other noble metals quantified in the present work include Au (0.226 ppm, 0.109–0.451 ppm), Ru (0.061 ppm, 0.006–0.264 ppm), Ir (0.071 ppm, 0.010–0.185 ppm), Pd (0.046 ppm, 0.017–0.107 ppm) and Os (0.010 ppm, <0.003–0.024 ppm). Elemental ratios of Au/Ir, Pd/Ir and Pt/Ir, the average values of which are respectively 4.6, 0.8, and 4.9, suggest that Au, Pd and Pt are poorly fractionated from Ir. The resulting Ir enrichment is unusual and should reflect a particularly soluble (and stable) aqueous complex of Ir in a highly oxidizing, low-temperature, Se-rich solution.

Coltan (the African trade name for columbite‐tantalite, a tantalum ore) is one of several raw materials that finance the civil wars in the eastern provinces of the Democratic Republic of the Congo. To improve the transparency along the tantalum trade chain, a ‘certificate of origin’ for so‐called ‘conflict minerals’ has been recommended by the United Nations. Accordingly, the German Federal Institute for Geosciences and Natural Resources (BGR) has developed an analytical fingerprint procedure for coltan. Mineral formation age, modal mineralogy and chemical composition are important fingerprint parameters. The original workflow to obtain these parameters was streamlined and is now based on mineral liberation analysis and LA‐ICP‐MS. The use of an ICP‐MS instrument with a detector system covering an extended linear dynamic range and the application of an internal standard‐independent calibration strategy allowed data for major and trace element determination and mineral formation age estimates to be obtained simultaneously. The analytical results of this new approach were compared with analytical techniques of the original workflow and showed excellent agreement in terms of mineralogical and chemical characterisation and mineral formation age of coltan samples. Within a test, samples of different origin were allocated correctly and simple, binary mixtures were also identified successfully.

A comparative in situ LA-ICP MS trace-element study on pyrite from three different, variably auriferous, Archaean to Palaeoproterozoic palaeoplacer deposits in the Ouro Fino Syncline (Quadrilátero Ferrífero; Brazil), the Elliot Lake area north of Lake Huron (SE Canada) and several deposits within the Witwatersrand Basin (South Africa) revealed systematic differences between morphologically different pyrite types and between the various palaeoplacer deposits. Especially the Ni and Au concentrations as well as Co/Ni and Mo/Ni ratios were found to be systematically different in detrital compact, detrital porous and post-sedimentary/hydrothermal pyrite grains from different source areas. High Co/Ni ratios and low Au concentrations are typical of post-sedimentary pyrite, which is hydrothermal in origin. In contrast, relatively low Co/Ni ratios and high Au contents characterise detrital porous banded and concentric pyrite grains (Au > 1 ppm), which are syn-sedimentary in origin. In the Elliot Lake area and the Witwatersrand Basin, detrital compact rounded pyrite is characterised by high Co/Ni ratios, which is in agreement with derivation from a hydrothermal source. Low Au concentrations in this pyrite type support the contention of the gold and the pyrite in these deposits coming from different source rocks. In contrast, derivation from an originally diagenetic pyrite is suggested for the detrital compact pyrite in the Ouro Fino Syncline because of low to intermediate Co/Ni ratios. High Au contents may indicate a genetic relationship between pyrite and gold there. Systematic differences exist between the three areas with respect to Au, Ni, Co, Mo and Cu distributions in detrital pyrite, which reflects differences in the provenance. A predominantly mafic/ultramafic source is indicated for the Ouro Fino, a felsic source for the Elliot Lake, and a mixed felsic–mafic provenance for the Witwatersrand pyrite populations. Independently of pyrite type, the higher Au endowment of the studied Witwatersrand and Ouro Fino conglomerates are also reflected by an overall higher Au concentration in the respective pyrite grains compared to the relatively Au-poor samples from Elliot Lake. In general, a strong positive correlation between Au and Pb levels in the various pyrite grains is noted. Analogous to Pb, which is well known for not being easily accommodated in the pyrite crystal lattice but occurring as discrete PbS phases, Au is considered to be present mainly in the form of discrete Au phases in minute pores and interstices of the pyrite grains rather than within the pyrite lattice.

The Leon domain adjacent to the Cadomian realm in the North Armorican domain appears to be a displaced crustal block, as its metamorphism and rock types bear a resemblance to the South Armorican domain of the internal Variscan belt. The amphibolite-facies Conquet-Penze Micaschist unit overlies the high-grade Lesneven Gneiss unit in the central part of the Leon. Timing and conditions of the metamorphic evolution have been evaluated. At the base of the Lesneven Gneiss unit, a high-pressure eclogite-facies stage (700 degrees C at > 13 kbar) was followed by a high-temperature event (800 degrees C at 8 kbar), which is characterized by the crystallization of garnet-cordierite assemblages in aluminous paragneisses. Maximal temperatures in the upper parts of the Lesneven Gneiss unit were 630 degrees C at 6 kbar. Zoned garnet in assemblages with staurolite recorded prograde P-T paths from 490-610 degrees C at 5-8 kbar in the upper and at 6-9 kbar in the lower parts of the Conquet-Penze Micaschist unit. Garnet Y, heavy rare earth elements, and Li are low in high-grade gneisses and display strong zonations in the micaschists. A younger population of monazite with a broad range of Y contents displays Th-U-Pb ages between 340 and 300 Ma. It crystallized subsequent to formation of foliations S-1-S-2 and Variscan peak metamorphic assemblages. In contrast, an older population of Cadomian monazite at 552-517 Ma is uniformly rich in Y, suggesting an earlier crystallization than garnet, however, at elevated temperatures. The findings do not support a South Armorican provenance of the Leon domain. The Leon units appear as part of a Cadomian crust at the northern margin of the former Armorican microplate. During a Variscan collision, this crust was strongly overprinted by underthrusting toward the southeast or east beneath the Central Armorican domain and by later uplift accompanied by Late Carboniferous dextral shear tectonics. The features are typical of the Variscan Saxo-Thuringian zone, which faced the Rheic Ocean to the north.

We present new analytical data of major and trace elements for the geological MPI‐DING glasses KL2‐G, ML3B‐G, StHs6/80‐G, GOR128‐G, GOR132‐G, BM90/21‐G, T1‐G, and ATHO‐G. Different analytical methods were used to obtain a large spectrum of major and trace element data, in particular, EPMA, SIMS, LA‐ICPMS, and isotope dilution by TIMS and ICPMS. Altogether, more than 60 qualified geochemical laboratories worldwide contributed to the analyses, allowing us to present new reference and information values and their uncertainties (at 95% confidence level) for up to 74 elements. We complied with the recommendations for the certification of geological reference materials by the International Association of Geoanalysts (IAG). The reference values were derived from the results of 16 independent techniques, including definitive (isotope dilution) and comparative bulk (e.g., INAA, ICPMS, SSMS) and microanalytical (e.g., LA‐ICPMS, SIMS, EPMA) methods. Agreement between two or more independent methods and the use of definitive methods provided traceability to the fullest extent possible. We also present new and recently published data for the isotopic compositions of H, B, Li, O, Ca, Sr, Nd, Hf, and Pb. The results were mainly obtained by high‐precision bulk techniques, such as TIMS and MC‐ICPMS. In addition, LA‐ICPMS and SIMS isotope data of B, Li, and Pb are presented.