Sven Sindern

Burbankite group minerals and their alteration in rare earth carbonatites—source of elements and fluids (evidence from C–O and Sr–Nd isotopic data)

The 370–380 Ma Khibina and Vuoriyarvi complexes on the Kola Peninsula, Russia, which form part of the Palaeozoic Kola Alkaline Province, contain REE-rich carbonatites with burbankite (Na,Ca)3(Sr,Ca,REE,Ba)3(CO3)5 or calcioburbankite (Na,Ca)3(Ca,Sr,REE,Ba)3(CO3)5 as the principal primary REE mineral. Within each complex the C–O and Sr–Nd isotopic data are similar for burbankite group minerals and co-existing calcite or dolomite (Khibina: δ13C(V-PDB)=−6.4 to−5.8‰, δ18O(V-SMOW)=7.3–7.7‰, (87Sr/86Sr)370=0.70390–0.70404 and (143Nd/144Nd)370=0.51230–0.51235; Vuoriyarvi: δ13C=−4.2 to −3.0‰, δ18O=8.1–9.4‰, (87Sr/86Sr)370=0.70313–0.70315 and (143Nd/144Nd)370=0.51243–0.51245). This indicates that the REE mineralization and its host carbonatites in each complex are derived from the same source and are co-genetic. There is, however, a great difference between the Sr, Nd and C isotopic signatures from Khibina and Vuoriyarvi, whereas the δ18O ranges are similar. This suggests that the REE carbonatites of the two complexes originate from sources with different isotopic signatures. At least three mantle components are needed to explain the variations in Sr and Nd compositions in the carbonatites from Kola. The δ13C ranges of primary carbonatites with low δ18O values are quite different for Khibina and Vuoriyarvi and show correlation with the radiogenic isotope compositions. The data may be best explained by subduction-related source contamination that caused δ13C variations in different mantle components. During late-stage processes burbankite and calcioburbankite have been replaced by various assemblages of REE–Sr–Ba minerals. The alteration of burbankite group minerals is an open-system hydrothermal process leading to multiple element transfer. It has produced mineral assemblages which are characterized by high δ18O values (Khibina: δ18O(V-SMOW)=11.4–13.9‰ and Vuoriyarvi: δ18O=17.1–18.0‰) compared to primary burbankite and calcioburbankite. Co-existing calcite and dolomite have retained their original C and O isotope compositions, and one calcite sample from Khibina shows strong positive δ13C–δ18O shifts similar to those of the pseudomorph. The high δ18O and sometimes high δ13C values can be attributed to low-temperature isotope exchange between minerals and fluid with variable CO2/H2O ratio taking place during and/or after crystallization as usually observed in carbonatites. The Sr and Nd isotope compositions of pseudomorphs and associated calcite/dolomite in general are identical to those of burbankite/calcioburbankite and associated carbonates suggesting that the fluids which caused burbankite alteration are from the same source, i.e. carbonatitic. Small variations in the Sr and Nd isotope signatures point to interaction of the pseudomorph-forming fluid with alkali silicate wall rocks.

Assessment of heavy metals in water samples and tissues of edible fish species from Awassa and Koka Rift Valley Lakes, Ethiopia

The Ethiopian Rift Valley Lakes host populations of edible fish species including Oreochromis niloticus, Labeobarbus intermedius and Clarias gariepinus, which are harvested also in other tropical countries. We investigated the occurrence of six heavy metals in tissues of these fish species as well as in the waters of Lake Koka and Lake Awassa. Both lakes are affected by industrial effluents in their catchments, making them ideal study sites. Mercury concentrations were very low in the water samples, but concentrations in the fish samples were relatively high, suggesting a particularly high bioaccumulation tendency as compared with the other investigated metals. Mercury was preferentially accumulated in the fish liver or muscle. It was the only metal with species-specific accumulation with highest levels found in the predatory species L. intermedius. Lower mercury concentrations in O. niloticus could be attributed to the lower trophic level, whereas mercury values in the predatory C. gariepinus were unexpectedly low. This probably relates to the high growth rate of this species resulting in biodilution of mercury. Accumulation of lead, selenium, chromium, arsenic and cadmium did not differ between species, indicating that these elements are not biomagnified in the food chain. Values of cadmium, selenium and arsenic were highest in fish livers, while lead and chromium levels were highest in the gills, which could be related to the uptake pathway. A significant impact of the industrial discharges on the occurrence of metals in the lakes could not be detected, and the respective concentrations in fish do not pose a public health hazard.

Volume characteristics and element transfer of fenite aureoles: a case study from the Iivaara alkaline complex, Finland

Abstract Fenitization in granodioritic rocks has been investigated taking the Iivaara alkaline complex (Finland) as a case study. Five main fenitization reactions responsible for the transition from a granodioritic precursor mineral assemblage to a syenitic or even cancrinite–syenitic mineral assemblage of the fenites are set up. An assessment of element transfer and volume change associated with each of these reactions indicates a general volume loss of about 20% due to fenitization. High activities of Na, Ca, Mg and Fe as well as a low H2O/CO2 ratio in the fenitizing fluid phase are indicated. Si, which is the main component released from the precursor rock, was redistributed within the aureole and formed pyroxene dominated mineral assemblages in a reaction with the fenitizing fluid. These vein-type pyroxenites can be found cross-cutting all fenite types. Compositional data of aegirine augite in the fenites reveal disequilibria and feldspar compositions point to minimum temperatures for the production of fenites with syenitic compositions of 660°C and also indicate fast cooling. A Sr isotope characterization of the fenites allows assessment of minimum fluid–rock weight-ratios in the fenite aureole of 0.023–2.3. The element transfer scheme developed in this study is applicable to other localities since many aureoles formed in granitic to granodioritic host rocks have petrographic characteristics similar to the Iivaara fenites.

Heavy metals in river and coast sediments of the Jakarta Bay region (Indonesia) - Geogenic versus anthropogenic sources

Sediment geochemistry of the Jakarta region, a densely populated tropical coast, is studied - with particular focus on rivers discharging to Jakarta Bay. Weathering volcanics in the river catchment area control the composition of major elements, As, Cr and in part Cu. In contrast, Zn, Ni, Pb and partly Cu are affected by anthropogenic sources, mainly in central Jakarta City. The data reflect a high variability of local emission sources, among which metal processing industries, fertilizers or untreated animal waste may be important. In particular, the role of street dusts is emphasized. Locally, heavy metals reach levels considered to have adverse biological effects. River discharge leads to anthropogenic enrichment of heavy metals in the coastal sediments. Element data also show geogenic effects on the composition of the coastal sediments, such as mixing of detrital silicates with biogenic carbonates as well as suspended particulate matter from the ocean.

SHORT-TERM HYDROTHERMAL EFFECTS ON THE ‘CRYSTALLINITIES’ OF ILLITE AND CHLORITE IN THE FOOTWALL OF THE AACHEN-FAILLE DU MIDI THRUST FAULT – FIRST RESULTS OF THE RWTH-1 DRILLING PROJECT

Investigation of material from three core sections of the RWTH-1 drill-hole in the Wurm syncline of Aachen, Germany, shows mineralogical and structural evidence of intensive hydrothermal activity in the footwall of the Aachen thrust. Mineral and microstructural data indicate minimum temperatures of 200–250°C. CISillite 001 values of 0.45–0.61 (Δ°2θ) and insignificant amounts of smectite indicate a late diagenetic grade for illite pointing to temperatures <200°C. Chlorite, mainly formed in veins and cleavage planes, has CISchlorite 002 values between 0.35 and 0.26 (Δ°2θ) which only in part point to anchizonal grade. In contrast to these illite and chlorite data, maximum temperatures up to 370°C can be expected based on comparison with recently published fluid inclusion and mineral thermometric data. Illite is neither significantly affected by the hydrothermal event nor by deformation, and mirrors the burial history of the Wurm syncline.Chlorite grew syntectonically as is shown by bent and predominantly stretched sheets which do not, however, have deformed structures. Syntectonic hydrothermal growth by incipient nucleation along crystal edges limited domainsize and thus also the CISchlorite 002 values. The hydrothermal event did not last long enough to allow further crystal growth. The retarded CISillite and CISchlorite grades can be best explained by limited duration(probably <5000 y) of the hydrothermal event which for a short time reached epithermal temperatures. The hydrothermal fluid flow was caused by dewatering of sedimentary rocks during thrusting and tectonic thickening within the Variscan orogen and it was focused along the Aachen thrust which represents the frontal Variscan thrust.

Tl-speciation of aqueous samples – a review of methods and application of IC-ICP-MS/LC-MS procedures for the detection of (CH3)2Tl+ and Tl+ in river water

This study provides an overview on Tl-speciation methods developed in the last years. Most of them require transformation of a species and do not allow direct detection of the species of interest. LC-MS and IC-ICP-MS methods are optimised for direct analysis of the Tl-species Tl+ and (CH3)2Tl+ (dimethylthallium (DMT)) in freshwater on a ng L−1 level. The methods are applied in a study of water from Vicht River in Stolberg (Germany). Tl+ is shown to be at least in part derived from anthropogenic sources among which the industrial sources may be significant. The natural occurrence of DMT is proven, although this Tl-species is temporally variable in abundance and Tl+ predominates.

In situ U-Pb (Shrimp) dating of zircons from granosyenite of the Troitsk pluton, Kvarkush-Kamennogorsk Anticlinorium, central Urals

The Troitsk granosyenite pluton is located among the Neoproterozoic sedimentary sequences of the Kvarkush‐Kamennogorsk Anticlinorium on the western slope of the Urals. The sedimentary sequences comprise the Kedrovka and Basegi groups of the Upper Riphean and the Serebryanka and Sylvitsa groups of the Vendian [1, 2]. In the mid-1980s, the Troitsk pluton was used as a reference intrusive body for timing the lower boundary(620 ± 15 Ma) of the Upper Vendian [3]. However, later on, the validity of the Rb‐Sr wholerock isochron age of carbonated granosyenites was questioned [4]. In addition to the Troitsk pluton, a number of other igneous complexes (Shpalorezov, Dvoretsk, Blagodatny, Kus’ya, Zhuravlik, and others) are localized in the Vendian sedimentary rocks of the Kvarkush‐Kamennogorsk Anticlinorium. Their petrology, geochemistry, and age are discussed in many publications. The results of geological mapping under the supervision of Suslov [5] made an important contribution to recognition of the geological position of some igneous complexes. The most reliable correlation of the Late Riphean and Vendian igneous complexes in the Kvarkush‐Kamennogorsk Anticlinorium was given in [6‐8]. Karpukhina et al. [9] made an attempt to reconstruct geodynamic settings of the Dvoretsk, Kus’ya, and Blagodatny complexes and estimated their Sm‐Nd and Rb‐Sr ages. The modern data on geochemistry, geodynamics, and geochronology of the Neoproterozoic igneous complexes on the western slope of the central Urals are summarized in [10].

Oldest (3.5 Ga) Zircons of the Urals: U-Pb (SHRIMP-II) and T DM Constraints

The Archean domains of the Earth composed of granite‐greenstone and granulite‐gneiss associations are now sufficiently well studied. Nevertheless, many aspects related to the early history of the planet are still far from being solved [1, 2, and others]. Such a situation is also characteristic of the Uralian foldbelt. The formation of the crust in this region spanned a long period comprising the Archean‐Early Proterozoic, Late Proterozoic, Paleozoic, and post-Paleozoic stages [3]. In recent years, considerable progress has been achieved in reconstruction of the major features of the last three stages in the foldbelt evolution mainly due to the active introduction of advanced methods of isotope geology based on sophisticated analytical equipment into geological studies. At the same time, significant difficulties remain in the reconstruction of the preRiphean stage for the following reasons: first, the reliably defined Archean metamorphic domain in the Urals is extremely limited and represented, in fact, only by the Taratash polymetamorphic complex of the Central Uralian Uplift with the single Neoarchean date [4] obtained only recently by the classical U‐Pb zircon method; second, the dating of Neoarchean rocks is hampered by several methodological and analytical problems, the correct solution of which is essential for validity of the results obtained. The Taratash polymetamorphic complex is located among volcanosedimentary rocks of the Lower Riphean Ai and Satka formations at the junction of the Bashkir and Uraltau anticlinoriums located between the South and Middle Urals (Fig. 1). It occupies an area of 400 km 2 and is composed of lithologically variable gneisses, two-pyroxene crystalline schists, quartz-bearing diorites and gabbrodiorites, and quartz‐feldspar rocks. The geological structure of the Taratash Complex, the petrology of its rocks, and metamorphism evolution are described in detail in [5]. The history of the study of the Taratash Complex by methods of isotopic geology (K‐Ar, α -Pb, 207 Pb/ 206 Pb thermal isochron, and classical U‐Pb) is already more than 35 years old [4‐7]. These studies revealed several stages in the evolution of the rock complex corresponding to granulite metamorphism, high-temperature amphibolite-facies diaphthoresis, amphibolite-facies metamorphism, and greenschist diaphthoresis. Nevertheless, many aspects of its formation remain unclear. Moreover, they are conflicting to a significant extent in light of recent data [8].

New data on the composition and age of orogenic granitoids from Timanides of the North Urals

618 The structure, composition, and age of rock com plexes constituting the pre Paleozoic (pre–Late Cam brian) structural stage in the northern Urals fold belt have been considered in many publications. An analy sis of them is available in [1, 4–7]. A qualitative leap in understanding the geological features of pre–Late Cambrian structures developed in this segment of the belt happened in connection with the discovery that Riphean and Vendian rock complexes of the Urals, which constitute the large Vendian–Early Cambrian Timan orogen, continue under the Paleozoic and Mesozoic sequences of the Pechora Plate [2, 3, 5, 7, 9].

The oldest magmatic formation of the uralides in the north Urals

1185 The structural relations between the Uralides and pre Uralides as well as the composition and age of Early Paleozoic geological formations constituting the Uralian fold belt have attracted the attention of many researchers for a long time [1–4, 6]. In the northern Urals, the Upper Cambrian–Lower Ordovician Al’kesvozh Sequence and Lower Ordovician Tel’pos (Obeiz) Formation are considered to be oldest rocks, which mark the initial stage in development of the Early Paleozoic system of continental rifts that pre ceded the opening of the paleoocean [4].