PDF version. Plant 1 , A. Whittaker 1 , A. Demetriades 2 , B. De Vivo 3 , and J. The geological record of Europe extends back in time to about 3, million years, approximately 1, million years after the Earth was formed. Europe was the birthplace of geological sciences. The first writers who have contributed something of geological significance were the ancient Greek philosophers Adams , such as Thales of Miletus c.
AD and many others. Modern geology begins with Georgius Agricola in Germany AD , who was one of the most outstanding figures in the history of the geological sciences, not only of his own times, but of all time, and his rightfully called the "Forefather of Geology". Hence, the continent's stratigraphy and structure has been studied for almost years. Initially, geology involved the examination and survey of surface rock exposures to prepare geological maps. More recently, understanding of the evolution of Europe's continental crustal structure has been greatly enhanced by the interpretation of new types of geophysical and geochemical data.
The present continent of Europe stretches from its submarine continental margin in the west to the Ural mountains in the east, and from the ancient and relatively tectonically stable rocks of the Fennoscandia Shield in the north, to the young, more tectonically and volcanically active zone, of the central and eastern Mediterranean in the south.
The evolution of the continent took place as a result of lithospheric plate interactions, which are now relatively well understood. The outer region of the Earth, or lithosphere, includes the crust and the upper mantle, and is a rheologically more rigid layer lying above a more plastic layer of the upper mantle, known as the asthenosphere.
The lithosphere is divided into several major tectonic plates that move relative to one another, and interact and deform, especially around their margins. Orogenesis, involving crustal thickening, deformation and metamorphism, is often followed by extensional collapse with widespread intrusion of highly evolved peraluminous granites. Plume activity is generally associated with continental break up, and there is considerable evidence of this following the splitting of the Earth's most recent supercontinent - Pangaea, beginning during the Permo-Triassic times.
At present, Europe forms the western part of the Eurasian Plate. In the Mediterranean region it abuts against the African Plate to the south which, combined with the broadly SE-directed ridge-push forces of the mid-Atlantic Ridge, and the beginning of an eastward Atlantic plate compression along Iberia, give a broadly NW-SE maximum horizontal crustal compressive stress throughout much of western and central Europe.
Although the plate tectonic processes affecting Europe over the last Ma period are reasonably well understood, the earlier evolution of Europe's continental lithosphere has been extremely long and complex and geological, and tectonic events are more obscure and difficult to interpret further back in time. To fully understand Europe's geology requires consideration of plate tectonic processes and the changing geometry and geography of plates operating throughout the 3, Ma 3. Like all continental landmasses, Europe presently comprises various crustal blocks, which have been assembled over geological time Figure 1.
In the extreme northwest of Scotland, there is a fragment of the late Proterozoic continent of Laurentia, initially part of a North American-Greenland landmass. Otherwise, Europe's continental basement can be divided broadly into two large and distinct regions: in the north and east a stable Precambrian craton known as the East European Craton EEC , and in the south and west a mobile belt, comprising crustal blocks that have become successively attached to the ancient cratonic nucleus. The TESZ is everywhere obscured and concealed beneath Mesozoic and Caenozoic sediments, but it has been reasonably well-defined as a broad zone of NW-SE-striking faults by subsurface geology, drilling results and geophysical methods, including deep seismic reflection data.
In contrast, the mobile belts to the south and west comprise Proterozoic-Palaeozoic crustal blocks or 'microcontinents' , which originated as part of the southern Gondwana continent, tectonised by end-Precambrian Cadomian orogenesis that became attached to the south west margin of the EEC in Palaeozoic times. These crustal blocks, belonging to Eastern Avalonia, now form part of the basement of the English Midlands, the southern North Sea, and Armorica extending from western Iberia and Brittany eastwards through central Europe to the Bohemian Massif.
The southerly European Alpine orogenic belt is mostly of Caenozoic age. In Europe, the precise locations of separate terranes, fault-bounded blocks of continental crust, usually smaller than microcontinents, related to Avalonia or Armorica are poorly exposed and concealed beneath younger rocks.
Also, in places, the reworking of older rocks in later orogenies has resulted in collages of relatively small shear-zone-bounded terranes such as the Precambrian Mona complex of North Wales, and similar complexes in the Bohemian Massif. During this long and complex crustal evolution, earlier consolidated crustal elements were repeatedly remobilised and overprinted by later events.
Thus, the basement provinces of western and central Europe are defined by the latest orogenic event affecting that portion of crust, causing widespread metamorphic reworking and, in many cases, the intrusion of calc-alkaline igneous rocks.
The oldest Precambrian basement provinces of western and central Europe, therefore, comprise the East European and Hebridean cratons, the stable Cadomian blocks of the London Platform and the East Silesian Massif, and the Caledonian, Variscan and Alpine fold belts. The boundaries between the principal structural elements of the European continental elements are in places poorly defined, partly as a result of a lack of data, and partly because they are concealed by younger rocks.
Also, metamorphic overprinting of some older basement areas has occurred during later orogenic cycles.
This is particularly the case with the Variscan fold belt, which in places seems to contain some Caledonian, as well as the Late Palaeozoic Devonian-early Carboniferous orogenic belts. Similarly, throughout the Alps of southern Europe, pre-Alpine basement rocks, including pre-Variscan basement, late-Variscan granitoids and post-Variscan volcaniclastic rocks, occur in many places. It consists mainly of Archaean granodioritic, tonalitic and amphibolitic gneiss, formed under granulite and amphibolite facies conditions at c.
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The protoliths of the Lewisian Gneiss Complex consist of granodioritic and tonalitic intrusions, diorite bodies, layered mafic-ultramafic bodies, mafic dykes and lenticular bodies, and minor metasedimentary rocks. Recent U-Pb zircon dating has shown that these range from 3, Ma to c. The rocks were subject to deformation at middle to lower crustal levels under granulite and upper amphibolite facies conditions during the Scourian event between c.
The Archaean architecture of the complex was completed by intrusion of granite sheets and pegmatites around 2, Ma, mainly in the Outer Hebrides. A major suite of Early Proterozoic tholeiitic dolerite and basalt dykes, the Scourie Dyke Suite, was intruded into the complex in two phases at c. Arc-related metasedimentary and metavolcanic rocks were later accreted to the complex in the South Harris and Loch Maree areas at around 1, Ma. The terranes were then largely reworked during a Laxfordian tectonometamorphic event that peaked at c. Only the area centred on Assynt, and small parts of the Outer Hebrides, avoided this penetrative reworking.
Laxfordian granite sheets were intruded at c. The area was uplifted prior to 1,, Ma ago when the older Torridonian Supergroup rocks were deposited. Some possible Grenvillian shear zone effects are recorded by uplift dates from the highly deformed Langavat meta-sedimentary belt in South Harris. Lewisianoid inliers of Laurentian affinity are also found in the Caledonian orogen as basement to the Moine Supergroup rocks of northwest Scotland. The most extensive area of exposed Precambrian rocks in Continental Europe is in the Fennoscandian Shield, which comprises four main NW to SE trending orogenic belts with the rocks generally younging southwestwards Figure 1.
This orogenic belt has distinctive geophysical properties compared to the Svecofennian Orogen. It has an average crustal thickness of 45 km with an upper layer interpreted as mainly magnetic diorite, and an eclogite facies transition at 38 km. In the extreme NE, the Murmansk gneiss-granulite terrane consists predominantly of tonalitic gneiss, granodiorite, amphibolite and migmatite, and minor granulite, pyroxene gneiss and schist, with intercalated banded ironstone formation, metamorphosed in the upper amphibolite-granulite facies.
The major structures are large-scale reclined folds intruded by plutons of late Archaean granitic rocks. Uranium-Pb zircon ages obtained on gneiss are 2. Adjacent to this terrane, to the southwest, the composite Sorvaranger island arc terrane consists of: two greenstone belts comprising amphibolite, ultramafic rocks and agglomeratic meta-volcanics and meta-psammite, pelite, banded ironstone formations and quartzite, mostly at amphibolite facies, and amphibolite to granulite facies migmatitic alumino-silicate schist and gneiss in thrust contact with the greenstone belts.
The discordant Neiden granitic pluton intruding greenstone belt rocks and the gneiss have a U-Pb and Rb-Sr age of 2. It has been suggested that the greenstone belts formed in arc and back-arc settings, while the gneiss is derived from turbidite, laid down in an arc-trench accretionary wedge Windley , The Inari gneiss terrane consists of heterogeneous migmatitic trondhjemitic to granitic orthogneiss within which there are conformable layers and lenses of amphibolite and mica schist up to 10 km wide, associated locally with calcic gneiss, quartzite and banded ironstone formation.
Uranium-Pb determination on zircon from the gneiss gives dates of 2. The basement of the Karelian composite terrane comprises Archaean greenstone belts comparable to modern island arc assemblages, separated by gneiss and granite. More than 20 major greenstone belts up to km long have been recognised, as well as many smaller ones, separated by belts of gneiss with different types of granite intrusions.
Across eastern Finland and Karelia, there are four tectonic zones with different compositions and ages of volcanic rocks in the greenstone belts. The composition and ages of the gneiss and granite, and their degree of metamorphism and deformation also varies. The greenstone belts young westwards from 3. The gneiss and granite are less well understood than the greenstone belts.
Some consist mostly of paragneiss, while others comprise mainly of orthogneiss and granite. Many show a close spatial and temporal relationship with the development of the greenstone belts. The oldest known rock in the Baltic Shield is gneiss in southeastern Karelia, which gives U-Pb zircon ages of 3.
Amphibolite and migmatite are dated at 3. The orogen was formed in the Early Proterozoic between 2. Island arcs, Andean-type magmatic arcs, sutures and remnant shelf successions were all included. The Kola suture zone is a southward-dipping thrust zone up to 40 km along which the Inari terrane is thrust over the Sorveranger terrane, while the Sirkka thrust is a major tectonic boundary along which the high-grade Belmorian terrane was thrust southwards under the low-grade Karelian terrane.
The suture zone is displaced by 1. The suture contains thrust slices of different types and origin, including two types of turbidite: those on the Archaean craton, immediately to the NE of the suture, where autochthonous turbidite contain Archaean and Proterozoic detritus locally interbedded with tholeiitic volcanics, and those in the suture that comprise allochthonous turbidite, deposited from debris flows and turbidity currents in submarine canyons at an accretionary margin.
The suture zone also contains serpentinite, gabbro, basaltic pillow lava, non-detrital quartzite, dolomite, Mg-rich meta-volcanics and Cu-sulphide deposits. The Svecofennian orogen contains no Archaean terranes, and is thought to have developed by the growth and accretion of juvenile arcs dated at 2. The orogen has a mainly paramagnetic dioritic upper crustal layer, and an average crustal thickness of 48 km maximum 54 km and a thick lower crustal layer.
The orogen comprises several magmatic arcs with rocks and ores comparable to those of modern island arcs and intra-arc rifts.
Petrological Evolution of the European Lithospheric Mantle
The 1. Uranium-Pb zircon data suggest that most of the Svecofennian arc lavas were erupted between 1. Many of the Sveco-Fennian arcs are separated by biotite-bearing granitic gneiss and schist, widely regarded as meta-greywacke and meta-pelite, which contain numerous large lenses of amphibolite, metagabbro and meta-ultramafic rocks.
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Nickel-Cu deposits occur in some peridotite-dunite-pyroxenite-gabbro lenses. Following arc accretion, syn- and post-collisional deformation took place. Thrusting and folding was associated with high amphibolite facies metamorphism that locally reached granulite grade, followed by the emplacement of rapakivi granite.
The last event in the evolution of the Svecofennian orogen was the deposition of the Jotnian sandstone at 1. Locally, this extends into exposed basement as rifts, framed as a result of the extension and thinning of the Sveco-Fennian crust. The batholith may have developed above an eastward-dipping subduction zone on the western margin of the Sveco-Fennian orogen.
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A small part of the Gothian orogen, which escaped Sveco-Norwegian reworking, is preserved in the extreme southeast of Sweden, and on the island of Bornholm, Denmark. There, acid meta-volcanics with a U-Pb age of 1. The oldest known Gothian rocks here is amphibolite dated at 1.