A hidden alkaline and carbonatite province of early carboniferous age in northeast Poland: Zircon U-Pb and pyrrhotite Re-Os geochronology

Extensive geophysical investigations in NE Poland in the 1950s and 1960s led to the discovery of an alkaline and carbonatite magmatic province buried under thick (600-800 m) Meso-Cenozoic cover north of the Trans-European Suture Zone, or Tornquist Line. Drilling focused on geophysical anomalies identified three intrusions in the Paleoproterozoic metasedimentary and metavolcanic rocks of the Mazowsze Domain: the Pisz gabbro-syenite massif, the Ełk syenite massif, and the small, differentiated Tajno body consisting of clinopyroxenite cumulates and syenites crosscut by carbonatite veins. Emplacement ages for these intrusions have been obtained by (1) zircon U-Pb geochronology on a gabbro from Pisz, a syenite from Ełk, and an albitite from Tajno and (2) a Re-Os model age for pyrrhotite from a Tajno carbonatite. The ages measured by both methods fall in the narrow range 354-345 Ma (Early Carboniferous: Tournaisian). This is slightly younger than the Late Devonian (380-360 Ma) Kola Peninsula alkaline and carbonatite province (20 intrusions) of NW Russia and Karelia but is of comparable age to the first manifestations of the long-lasting (~100 m.yr.) Carboniferous to Permian magmatic event (360-250 Ma) manifest in northern Europe (from the British Isles to southern Scandinavia, the North Sea, and northern Germany) in the foreland of the Variscan orogeny (in the so-called West European Carboniferous Basin) and the East European Craton

A geochronological review of magmatism along the external margin of Columbia and in the Grenville-age orogens forming the core of Rodinia

A total of 4344 magmatic U-Pb ages in the range 2300 to 800 Ma have been compiled from the Great Proterozoic Accretionary Orogen along the margin of the Columbia / Nuna supercontinent and from the subsequent Grenvillian collisional orogens forming the core of Rodinia. The age data are derived from Laurentia (North America and Greenland, n = 1212), Baltica (NE Europe, n = 1922), Amazonia (central South America, n = 625), Kalahari (southern Africa and Dronning Maud Land in East Antarctica, n = 386), and western Australia (n = 199). Laurentia, Baltica, and Amazonia (and possibly other cratons) most likely formed a ca. 10 000-km-long external active continental margin of Columbia from its assembly at ca. 1800 Ma until its dispersal at ca. 1260 Ma, after which all cratons studied were involved in the Rodinia-forming Grenvillian orogeny. However, the magmatic record is not smooth and even but highly irregular, with marked peaks and troughs, both for individual cratons and the combined data set. Magmatic peaks typically range in duration from a few tens of million years up to around hundred million years, with intervening troughs of comparable length. Some magmatic peaks are observed on multiple cratons, either by coincidence or because of paleogeographic proximity and common tectonic setting, while others are not. The best overall correlation, 0.617, is observed between Baltica and Amazonia, consistent with (but not definitive proof of) their being close neighbours in a SAMBA-like configuration at least in Columbia, and perhaps having shared the same peri-Columbian subduction system for a considerable time. Correlation factors between Laurentia and Baltica, or Laurentia and Amazonia, are below 0.14. Comparison between the Grenville Province in northeastern Laurentia and the Sveconorwegian Province in southwestern Fennoscandia (Baltica) shows some striking similarities, especially in the Mesoproterozoic, but also exhibits differences in the timing of events, especially during the final Grenville-Sveconorwegian collision, when the Sveconorwegian evolution seems to lag behind by some tens of million years. Between the other cratons, the evolution before and during the final Grenvillian collision is also largely diachronous. After 900 Ma, magmatic activity had ceased in all areas investigated, attesting to the position of most of them within the stable interior of Rodinia.publishedVersio

Trichoceridae of Massif Central (France) (Dipt. Nematocera)

Résumé. — Après les travaux de Macquart (1834), Keilin (1912), Pierre (1924) et plus récemment de Thomas et Vaillant (1977), la faune des Trichocerides de France ne semblait comporter que 7 espèces sur les 25 signalées en Europe. Les auteurs présentent ici la phénologie de 11 espèces capturées dans le seul département du Puy-de-Dôme (Massif central français). Quatre de ces espèces sont nouvelles pour la faune de France : Trichocera forcipula, Trichocera implicata, Trichocera japónica, Trichocera major. Cette faune des Trichocerides de France peut être subdivisée en 2 groupes d'espèces : les espèces à large répartition qui occupent aussi la strate aérienne pendant presque toute l'année (de septembre à mai-juin) et les espèces sténothermes froides, strictement liées aux massifs montagneux, qui ne se rencontrent que brièvement à l'état imaginai (automne et hiver). Dans le premier groupe nous trouvons : Trichocera annulata, T. hiemalis, T. saltator, , T. regelationis et Trichocera maculipennis, et dans le le second : Trichocera forcipula, Trichocera dalhae, Trichocera implicata, Trichocera japónica, Trichocera major et Trichocera parva. Ces liens entre sténochronie et stenotopie d'une part et eurychronie et eurytopie d'autre part, ont été mis en évidence (Brunhes et Villepoux, sous presse) en ce qui concerne les Limonides des tourbières d'Auvergne.Krzeminska Ewa, Brunhes Jacques. Trichoceridae of Massif Central (France) (Dipt. Nematocera). In: Bulletin de la Société entomologique de France, volume 96 (1), mars 1991. pp. 49-54

Trichoceridae of Massif Central (France) (Dipt. Nematocera)

Résumé. — Après les travaux de Macquart (1834), Keilin (1912), Pierre (1924) et plus récemment de Thomas et Vaillant (1977), la faune des Trichocerides de France ne semblait comporter que 7 espèces sur les 25 signalées en Europe. Les auteurs présentent ici la phénologie de 11 espèces capturées dans le seul département du Puy-de-Dôme (Massif central français). Quatre de ces espèces sont nouvelles pour la faune de France : Trichocera forcipula, Trichocera implicata, Trichocera japónica, Trichocera major. Cette faune des Trichocerides de France peut être subdivisée en 2 groupes d'espèces : les espèces à large répartition qui occupent aussi la strate aérienne pendant presque toute l'année (de septembre à mai-juin) et les espèces sténothermes froides, strictement liées aux massifs montagneux, qui ne se rencontrent que brièvement à l'état imaginai (automne et hiver). Dans le premier groupe nous trouvons : Trichocera annulata, T. hiemalis, T. saltator, , T. regelationis et Trichocera maculipennis, et dans le le second : Trichocera forcipula, Trichocera dalhae, Trichocera implicata, Trichocera japónica, Trichocera major et Trichocera parva. Ces liens entre sténochronie et stenotopie d'une part et eurychronie et eurytopie d'autre part, ont été mis en évidence (Brunhes et Villepoux, sous presse) en ce qui concerne les Limonides des tourbières d'Auvergne.Krzeminska Ewa, Brunhes Jacques. Trichoceridae of Massif Central (France) (Dipt. Nematocera). In: Bulletin de la Société entomologique de France, volume 96 (1), mars 1991. pp. 49-54

Rewizja wieku najstarszych" skal w podlozu krystalicznym polnocno-wschodniej Polski

The oldest geochronological results between 2.69-2.57 Ga was previously obtained by using K-Ar method on biotite from pegmatite from Jastrzebna IG-1 borehole. In consequence, in many published reports up to 1998, the Mazowsze (or Masovian) granitoid massif has been regarded as Archean age structure. Therewithal, other rocks in the area, e.g. Bargłów gneiss sequence traditionally were described as Archean in age. In the paper we present new U-Pb SHRIMP zircon and monazite results for above mentioned rocks which have been considered as Archean. Cathodoluminescence images and SHRIMP analysis were carried out for zircons and monazites from Jastrzebna IG-1 pegmatite of 514 m depth (a historical sample previously dated by K-Ar method) and for zircon magmatic cores from Bargłów IG-2 orthogneiss of the 708 m depth. The obtained U-Pb ages of 1826±12 Ma (zircon) and 1789±34 Ma (monazite), and 1835±28 Ma (zircon) for two rock samples respectively have shown Paleoproterozoic origin. Only 4 of the 24 analysed zircons have clearly discordant results, which are all from the Jastrzebna pegmatite, where Pb-loss was possible (in partially metamict U-rich zircon grains). The new U-Pb SHRIMP dating indicates that Jastrzebna pegmatite and Bargłów magmatic protolith of the orthogneiss is only Late Paleoproterozoic in age and in general about 700 Ma younger than previously reported by K-Ar method. Therefore, there is no unequivocal evidence of the presence of Archean rocks in crystalline basement of NE Poland. This study has been undertaken as a part of a collaborative research agreement between the Polish Geological Institute and Geochronology and Isotope Geochemistry Research School of Earth Sciences of the Australian National University in Canberra

An extension of the Svecofennian orogenic province into NE Poland: Evidence from geochemistry and detrital zircon from Paleoproterozoic paragneisses

The Precambrian crystalline rocks of northern Poland are known only from deep drill cores. Drilling at Jastrzebna and Monki, in the Mazowsze Domain, NE Poland, has intersected a monotonous sequence of grey paragneisses superficially similar to the paragneisses of the Svecofennian Domain exposed in Sweden and Finland. Petrographically, geochemically and isotopically the rocks from the two regions are in fact almost the same. The Jastrzebna paragneiss is an immature metasediment characterised by depleted HREE and Y, indicative of derivation from a source dominated by TTG-type rocks. The Monki metasediment, in contrast, is more mature and chemically uniform, with a REE pattern very similar to average Post-Archean Australian Shale (PAAS). Both metasediments have La-Sc-Th compositions characteristic of active continental margin or continental arc settings. The detrital zircon populations in the two Polish metasediments have the same age distributions; a dominant Paleoproterozoic population at 2.1-1.9 Ga, a subordinate late Archean population at 2.9-2.7 Ga, and rare early Archean grains up to 3.4 Ga. Both samples have very few zircons in the age range 2.6-2.1 Ga. This age distribution is extremely similar to the age distributions of detrital zircon from Svecofennian metasediments exposed in Sweden and Finland. It is highly likely that the Polish metasediments are derived from the same source region as the 'classical' Svecofennian, and were deposited in the same basin or basin system. The ages of the detrital zircons do not match the ages of any known igneous rocks currently exposed in the Baltic Shield. However, they do match the ages of rocks within the Osnitsk-Mikashevichi Igneous Belt on the western margin of Sarmatia, plus Archean rocks of the adjacent Ukrainian Shield. It is likely that detritus eroded from this region at ca. 1.93-1.86 Ga, during a period of rapid uplift, was deposited in a continental marginal basin system adjacent to the Archean craton. The Polish metasediments were metamorphosed up to lower amphibolite facies at ca. 1.83 Ga

Wczesnokarboñski wiek intruzji platformowych w podlozu krystalicznym NE Polski

Three mafic-alkaline intrusive bodies in NE Poland: Ełk, Pisz and Tajno, have been dated recently with U-Pb SHRIMP method. An earlier Rb-Sr whole rock isochron of Ełk syenites pointed to an age 355±4 Ma, while K-Ar age estimates suggested a Late Paleo

A Late Paleoproterozoic (1.80 Ga) subduction-related mafic igneous suite from Lomza, NE Poland

The Lomza orthoamphibolites in the crystalline basement of NE Poland, dated at 1802 ± 9 Ma by SHRIMP zircon U-Pb, are characterized by high incompatible and REE element contents. These features, the low Nb, and the position of the rock compositions on L