1.90-1.88Ga arc magmatism of central Fennoscandia: geochemistry, U-Pb geochronology, Sm-Nd and Lu-Hf isotope systematics of plutonic-volcanic rocks from southern Finland

The earliest Svecofennian magmatism in southern Finland has been dated at 1.90-1.88Ga. As an example of this, the Orijärvi (ca. 1.89Ga) and Enklinge (ca. 1.88Ga) volcanic centres comprise bimodal plutonic batholiths surrounded by volcanic rocks of comparable ages and chemical compositions. Here, we report geochemical and Sm-Nd isotope data from intrusive and extrusive samples, combined with zircon U-Pb and Lu-Hf isotopes for granodiorites from both study areas. The samples range from gabbros to granites and indicate a subduction-related continental margin setting. The zircons from the Orijärvi granodiorite define an age of 1892±4Ma whereas the Enklinge granodiorite yields an age of 1882±6Ma. Several inherited ages of 2.25-1.95Ga as well as younger ages of 1.86-1.80Ga were found in the Enklinge granodiorite. The initial εNd values from the mafic rocks from both locations fall in the range +1.1 to +2.9 whereas the felsic rocks exhibit initial εNd values of -0.4 to +1.2. The magmatic zircons from the Orijärvi and Enklinge granodiorites show average initial εHf values of -1.1 (at 1892Ma) and zero (at 1882Ma), respectively, each with a spread of about 7 ε-units. The initial εHf values for the inherited zircons from Enklinge range from +3.5 to +7.6 with increasing age. The Sm-Nd data indicate that the mafic rocks were derived from a “mildly depleted” mantle source while the felsic rocks show larger crustal contribution. Also, the variation in εHf values indicates minor mixing between mildly depleted mantle derived magmas and crustal sources. U-Pb ages and Hf isotopes for inherited zircons in the Enklinge granodiorite suggest the presence of juvenile Svecofennian “proto-crust” at depth

The lead and copper isotopic composition of copper ores from the Sierra Morena (Spain)

The paper presents lead and copper isotope analyses of 51 copper ore samples from the Sierra Morena, South of Spain. They are from ancient mines of the Iberian Peninsula collected by Claude Domergue during various field campaigns in the central Sierra Morena from 1965 to 1975. Most samples consist of copper oxide minerals such as malachite, azurite and chrysocolla and stem from the surficial sections of the ore deposits. The aim of the study was to supplement the existing reference data bank on lead isotopic compositions of ancient copper mines from the Iberian Peninsula. This is particularly important for the Sierra Morena for which data exist mostly for lead-zinc but not for copper ores. The lead isotope ratios range from 18.165 to 19.712 (206Pb/204Pb), 0.797 to 0.859 (207Pb/206Pb) and 1.955 to 2.108 (208Pb/206Pb). Two separate fields can be distinguished with a major field intermediate between the ore deposits from SW and SE Spain and a second at higher 208Pb/206Pb values. Copper isotopes were analysed additionally to provide further constraints for provenance studies. The copper isotope ratios δ65Cu of the copper oxide samples are mostly positive and higher on average than those of sulphide minerals. They are a potential tool to distinguish between either sulphide ore or oxide ore deposit derived artefacts.En este artículo, presentamos los resultados de los análisis isotópicos (plomo y cobre) llevados a cabo sobre 51 muestras de mineral de cobre de Sierra Morena, Sur de España. Las muestras provienen de minas antiguas de la Península Ibérica, que habían sido recogidas por Claude Domergue en el curso de sus prospecciones en Sierra Morena central, entre 1965 y 1975. La mayoría de las muestras consiste de minerales de óxido de cobre como malaquita, azurita y crisocola que se encuentran en la superficie de los depósitos. El objetivo de este estudio es de contribuir a la base hoy disponible de datos de isótopos de plomo de las antiguas minas de cobre en la Península Ibérica. Este objetivo es particularmente importante puesto que la mayoría de los datos publicados de Sierra Morena se refieren a minerales de plomo-zinc. Las proporciones de isótopos de plomo varían entre 18.165 y 19.713 206Pb/204Pb, de 0.797 a 0.859 207Pb/206Pb, y de 1.955 a 2.108 208Pb/206Pb. Se pueden distinguir dos zonas independientes: una zona principal que se sitúa entre los depósitos de España del sudoeste y sudeste y una segunda zona con las proporciones de isótopos de plomo más altas. Además, los isótopos del cobre fueron analizados para suplir restricciones adicionales en los estudios de proveniencia. Las proporciones de isótopos de cobre, δ65Cu/63Cu, fueron analizadas en los óxidos de cobre y son en la mayor parte positivas y mas altas en medio que las proporciones δ65Cu de los sulfuros de cobre. Los resultados presentan un instrumento eficiente para distinguir los artefactos elaborados de minerales de sulfuros de cobre o de minerales de óxido de cobre

A 1.85 Ga volcanic arc offshore the proto-continent Fennoscandia in southern Sweden

The Fröderyd Group forms part of the Vetlanda-Oskarshamn belt (also known as the Oskarshamn-Jönköping Belt), which is a piece of Palaeoproterozoic crust that is completely encapsulated by 1.81–1.77 Ga granitoids of the Transscandinavian Igneous Belt in the southern part of the Fennoscandian Shield. New U-Pb zircon data from a felsic metavolcanic rock in the Fröderyd Group have been acquired using LA-ICP-MS single collector. The age is determined to 1853 ± 11 Ma. The Fröderyd Group is interpreted to represent a volcanic arc that was located southwest of the margin to the proto-continent Fennoscandia. Tonalitic magma, identified in the Eksjö-Bäckaby regions, formed the middle crust in this arc complex and intruded the volcanic arc rocks at ca. 1.83–1.82 Ga. When this arc complex gradually approached the margin to the proto-continent Fennoscandia, parts of it were uplifted above sea level and initiated lacustrine sedimentation in restricted basins, which now are found in the Vetlanda region. Parallel with the development of this arc complex, 1.86–1.85 Ga granitoids intruded the margin to the proto-continent Fennoscandia and 1.87–1.86 Ga clastic metasedimentary rocks in the Västervik area in an Andean-type active continental margin.It can be concluded that the Vetlanda and Västervik sedimentary basins formed in two completely different geological environments during two separate events. The Västervik sediments formed along the margin to the proto-continent Fennoscandia before the Fröderyd arc system had developed while the Vetlanda sediments formed in a post-arc environment outboard to the southwest of the margin to the proto-continent Fennoscandia. It is suggested that the mafic volcanic rocks close to the lake Nömmen should be excluded from the Vetlanda supergroup and instead be related in time to the Fröderyd Group. This paper presents an interpretation of the tectonic evolution including volcanic arc and rifted volcanic arc during the 1.87 to 1.77 Ga time span with relevance to the evolution of the active southwestern margin of the proto-continent Fennoscandia depicted as a sequence of schematic profiles.</p

Lithium isotopes in fluid inclusions as tracers of crustal fluids: An exploratory study

Lithium isotopes are extensively used to trace fluid migration and fluid-rock interactions in the shallow Earth's crust. Although, Li isotope systematics might give important information about deep crustal fluids, this stable isotope system remains surprisingly under exploited in fluid inclusions. Here, twenty-three samples from a variety of deep environments, from diagenetic, metamorphic to magmatic-hydrothermal conditions (~150 to 600°C), have been investigated in order to provide the first exploratory overview of the range in Li isotopic composition of fluid inclusions. From 1 to 2g of hydrothermal quartz or dolomite, cation analysis (Na, K, Ca, Mg, Sr, Li), Li fraction recovery and Li isotopic analysis of bulk fluid inclusion leachates were carried out by using an innovative approach coupling crush-leach extraction, high performance ion chromatography and MC-ICPMS analysis. Reconstructed Li concentrations and δ7Li values of these fluid inclusions (respectively 12 to 653mg/l and −1.4±0.2‰ to +41.3±0.8‰) are compatible with previously proposed models for the origin of the fluids and fluid-rock interactions. δ7Li values are independent from other tracers (Br/Cl, I/Cl) and parameters such as temperature, salinity, and cation content (Na/Ca, Na/K, Na/Mg, Na/Li, Na/Sr ratios). The results show that, in conjunction with other parameters, the Li isotopic compositions of fluid inclusions are potentially powerful source and process tracers of deep crustal fluids within a wide range of geological environments and related ore-forming systems, for example in from sedimentary basins, seafloor hydrothermal systems and subduction zones

Lithosphere 2016: Ninth symposium on the Structure, Composition and Evolution of the Lithosphere in Fennoscandia

The geochemical composition of seven post-kinematic mafic dykes in southern part of Central Svecofennia have been studied. Two dykes have been selected for in situ zircon U-Pb geochronology and one for in situ zircon Lu-Hf isotope analysis.These c. 1.86 Ga dykes can be divided into two subgroups by their geochemical characteristics: i) an enriched type with Nb contents up to 42 ppm, high contents of certain fluid mobile elements such as F, Ba, Sr, K2O and LREE and elevated contents of Fe2O3, Ti2O and P2O5, and ii) a primitive type with high MgO and Cr content. The primitive dyke exhibit positive, average c. +3, initial εHf values. The geochemical data combined with the petrological and the field observations suggest that the dykes are juvenile and derived from a subduction-enriched mantle source in a within-plate environment during the post-kinematic stage of the Svecofennian orogeny.</p

Novel Mechanism of Supersolid of Ultracold Polar Molecules in Optical Lattices

We study the checkerboard supersolid of the hard-core Bose-Hubbard model with the dipole-dipole interaction. This supersolid is different from all other supersolids found in lattice models in the sense that superflow paths through which interstitials or vacancies can hop freely are absent in the crystal. By focusing on repulsive interactions between interstitials, we reveal that the long-range tail of the dipole-dipole interaction have the role of increasing the energy cost of domain wall formations. This effect produces the supersolid by the second-order hopping process of defects. We also perform exact quantum Monte Carlo simulations and observe a novel double peak structure in the momentum distribution of bosons, which is a clear evidence for supersolid. This can be measured by the time-of-flight experiment in optical lattice systems

Cooling a nanomechanical resonator with quantum back-action

Quantum mechanics demands that the act of measurement must affect the measured object. When a linear amplifier is used to continuously monitor the position of an object, the Heisenberg uncertainty relationship requires that the object be driven by force impulses, called back-action. Here we measure the back-action of a superconducting single-electron transistor (SSET) on a radiofrequency nanomechanical resonator. The conductance of the SSET, which is capacitively coupled to the resonator, provides a sensitive probe of the latter's position;back-action effects manifest themselves as an effective thermal bath, the properties of which depend sensitively on SSET bias conditions. Surprisingly, when the SSET is biased near a transport resonance, we observe cooling of the nanomechanical mode from 550mK to 300mK-- an effect that is analogous to laser cooling in atomic physics. Our measurements have implications for nanomechanical readout of quantum information devices and the limits of ultrasensitive force microscopy (such as single-nuclear-spin magnetic resonance force microscopy). Furthermore, we anticipate the use of these backaction effects to prepare ultracold and quantum states of mechanical structures, which would not be accessible with existing technology.Comment: 28 pages, 7 figures; accepted for publication in Natur

Coherent collapse of a dipolar Bose-Einstein condensate for different trap geometries

We experimentally investigate the collapse dynamics of dipolar Bose- Einstein condensates of chromium atoms in different harmonic trap geometries, from prolate to oblate. The evolutions of the condensates in the unstable regime are compared to three-dimensional simulations of the Gross-Pitaevskii equation including three-body losses. In order to probe the phase coherence of collapsed condensates, we induce the collapse in several condensates simultaneously and let them interfere

d-wave collapse and explosion of a dipolar Bose-Einstein condensate

We investigate the collapse dynamics of a dipolar condensate of 52Cr atoms when the s-wave scattering length characterizing the contact interaction is reduced below a critical value. A complex dynamics, involving an anisotropic, d-wave symmetric explosion of the condensate, is observed. The atom number decreases abruptly during the collapse. We find good agreement between our experimental results and those of a numerical simulation of the three-dimensional Gross-Pitaevskii equation, including contact and dipolar interactions as well as three-body losses. The simulation indicates that the collapse induces the formation of two vortex rings with opposite circulations.Comment: 4 pages, 4 figure

Age and geochemistry of granitoids in the Precambrian basement of Öland, SE Sweden – implications for the extension of the Transscandinavian Igneous Belt in the Baltic Sea region

The Precambrian crust in the Baltic Sea region is mostly covered by Phanerozoic sedimentary rocks but can be studied in drill cores. Two granitoids from the crystalline basement below Öland were collected from the archives of the Geological Survey of Sweden and analyzed for geochemistry and dated with the U-Pb method on zircons. The Böda Hamn granitoid (northern Öland) has a monzodioritic composition and an age of 1799.8±3 Ma while the Valsnäs granitoid (central Öland) has a quartz monzonitic composition and an age of 1784.9±5.7 Ma. These geochemical-isotopic characteristics are compatible with those of generation 1 of the Transscandinavian Igneous Belt (TIB) in the Fennoscandian Shield, ≥30 km west of Öland.A more detailed review of the TIB-1 generation shows that two sub-generations (1a and 1b) can be distinguished on each respective side of the Oskarshamn-Jönköping Belt (OJB). Sub-generation 1a (north of OJB) has an age span of 1794-1808 Ma while sub-generation 1b (south of OJB) has an age span of 1769-1793 Ma. According to this subdivision, the Böda Hamn monzodiorite belongs to sub-generation 1a, which also can be followed to southernmost Gotland (Sundblad et al. 2003) and the Valsnäs quartz monzonite belongs to sub-generation 1b, which can be followed to the Latvian/Lithuanian border, where a marginally younger granitoid was reported from off shore drill core E-7 (Salin et al. 2016). Taken together, these data suggest that the Transscandinavian Igneous Belt can be traced across the Baltic Sea from the exposed parts within the Fennoscandian Shield to the Latvian/Lithuanian border.Salin, E., Sundblad, K., Woodard, J. and Lahaye, Y. 2016: The Precambrian crust in the Baltic Sea region. Bulletin of the Geological Society of Finland, 32nd Nordic Geological Winter Meeting, Helsinki. Abstract volume, p. 162.Sundblad, K., Claesson, S. & Gyllencreutz, R. 2003: The Precambrian of Gotland – a key to the understanding of the geologic environment for granitoids in the Baltic Sea region. Granitic systems – State of the art and future avenues. An international symposium in honor of professor Ilmari Haapala. Abstract volume, Helsinki, 102­–106. </p