1,720,974 research outputs found
Out of sequence thrust in the inner zone of northern Apennines: insight from Elba island nappe stack.
No full textCoexistence of contractional and extensional tectonics during the northern Apennines orogeny: The late Miocene out-of-sequence thrust in the Elba Island nappe stack
No full textIn the northern Tyrrhenian Sea, the Elba Island is one of the westernmost portions of the northern Apennine inner belt. One of its noteworthy features is the anomalous tectonic repetition of continental-derived (Tuscan Unit) and oceanic-derived (Ligurian units) thrust sheets, lately intruded by late Miocene granitoids. Moreover, in detail, a slice of strongly deformed Ligurian peridotites results tectonically sandwiched between two thrust sheets of Tuscan units. This tectonic setting results from a middle Miocene folding and thrusting of the Apenninic nappe stack with development of large-scale antiform and out-of-sequence thrust. In central-eastern Elba Island, the folding of an imbricate stack is bracketed between Langhian (middle Miocene) and Messinian (late Miocene). Consequently, the anomalous repetition of Tuscan and Ligurian units thrust sheets gives evidence of middle-late Miocene shortening deformation post-dating nappe stack and pre-dating late Miocene-Pliocene granite emplacement. We suggest that the architecture of the Elba Island nappe stack documents the coexistence of early-middle Miocene contractional and extensional tectonics in an overall convergent tectonic setting in the westernmost zone of northern Apennines. Extensional tectonics in the upper portion of the wedge, balancing transient gravitational instabilities due to over-thickened conditions, were followed by a renewal of contractional deformation leading to development of large-scale out-of-sequence thrust responsible for inversion of the stack order
The "Fornovolasco meta-rhyolite": an Early Permian magmatic event recorded in the Apuan Alps basement
No full textNo abstract availabl
New geological and structural characterization of Fornovolasco tectonic window (Alpi Apuane, Tuscany, Italy)
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Capraia quarry's a precious marble (Apuan Alps, Tuscany).
No full textE’ stato realizzato un rilevamento geologico di dettaglio dei
marmi “storici” affioranti nel fianco dritto della sinclinale della
Capraia nel versante occidentale delle Alpi Apuane (Toscana). Si
tratta di materiali di gran pregio, oggetto di coltivazione presso la cava
omonima ubicata nel Comune di Massa. La formazione geologica
interessata dalla coltivazione è nota in letteratura con il nome di
Breccia di Seravezza (Retico sup.), costituita da metabrecce
caratterizzate da clasti calcarei e dolomitici di colore molto variabile
dal rossastro al grigio al giallo crema, immersi in una matrice
generalmente rossastra per la presenza di ossidi di ferro e ricca di
cloritoide. Le varietà estratte sono commercializzate con nomi
particolarmente fantasiosi: Fior di Pesco, Breccia Capraia, Breccia
Madonn
A pilot study to test the reliability of the ERT method in the identification of mixed sulphides bearing dykes: The example of Sidi Flah mine (Anti-Atlas, Morocco)
No full textA multidisciplinary study, comprising geological, petrographical and geophysical methods, was carried out for the identification and the geometrical and volumetric assess of the main mineralized bodies (mixed sulphides, Zn-Pb and Fe-Cu) in the area of the Anti-Atlas chain, located at SW of the town of Sidi Flah (Ouarzazate, Morocco). The initial phase of exploration involved an extensive fieldwork (structural investigations and sampling) and a detailed survey for verifying the effectiveness and reliability of the Electrical Resistivity Method (ERT). Geological fieldworks and laboratory analyses played a fundamental role in identifying the resistivity anomalies and constraining tomographic results. Main issues we focused on are: i) mineralized bodies imaging according to the electrodic step; ii) consistency with geometry of mineralized bodies; iii) contrast of electrical resistivity between mineralized dykes and host rocks; iv) possible correlations between the type and amount of sulphides and electrical resistivity
Evidence of Permian magmatism in the Alpi Apuane metamorphic complex (Northern Apennines, Italy): New hints for the geological evolution of the basement of the Adria plate
Full text linkThe occurrence of metavolcanic rocks within the Paleozoic basement of the Alpi Apuane metamorphic complex has been known since long time. Among them, some massive porphyritic tourmaline-bearing rocks cropping out in the southern sector of the Alpi Apuane present some distinctive and peculiar features, differing from the better known middle Ordovician metarhyolites of the “Porfiroidi e scisti porfirici” Fm. The porphyritic tourmaline-bearing rocks belong to the recently proposed Fornovolasco Metarhyolite Fm. They are granular to porphyritic, with phenocrysts of quartz (often with magmatic embayment), pseudomorphosed feldspars, and mica (both biotite and muscovite), in a groundmass formed by quartz, white mica, albite, and K-feldspar. Tourmaline (schorl-dravite in composition) is an abundant accessory mineral, in some cases forming cm-sized spots. The studied rocks plot into the rhyolite field of the Total Alkali vs Silica classification diagram. They show a peraluminous nature, having an Alumina Saturation Index ranging from 1.3 and 3.2. Their trace-element signature is that typical of highly evolved orogenic magmas. Laser ablation-ICP-MS U—Pb datings on zircon suggest a Permian crystallization age (weighted average ages of the four samples ranging from 292 and 271 Ma), thus relating these rocks to a post-Variscan magmatism. This new dating represents the very first evidence of a Permian magmatism in the pre-Triassic basement of the Northern Apennines. The potential relationships between Permian felsic magmatism and the ore genesis in the Alpi Apuane metamorphic complex are also discussed
Geology and tectonic setting of the Fornovolasco area, Alpi Apuane (Tuscany, Italy)
Full text linkThe study area is located in the Alpi Apuane (Tuscany, Italy), and extends between N 44°0′49.883″–E 10°20′23.467″ (SW corner) and N 44°2′53.403″–E 10°23′19.175″ (NE corner). The area shows a pile of tectonic units belonging either to the Apuane metamorphic complex, and Tuscan Nappe, stacked during the Alpine orogeny. The latter is represented by a sedimentary Triassic-Miocene succession, and it is characterized by a large-scale east-dipping monocline, with local excision of stratigraphic terms due to the occurrence of intra-unit low-angle normal faults. The Apuane metamorphic complex is formed by Paleozoic phyllites, post-Variscan magmatic rocks (Fornovolasco Metarhyolite Fm.), and Mesozoic-Tertiary metasedimentary formations. The 1:5000 scale geological map and the cross-sections illustrate the tectonic setting of the Fornovolasco area, resulting from the Tertiary tectono-metamorphic events. In the Fornovolasco area, small Tl-rich pyrite + magnetite ore bodies occur close to the contacts between the Paleozoic basement and the cover metasedimentary formations.</p
Thallium distribution in rocks from the Sant'Anna tectonic window (Apuan Alps, Italy)
No full textNo abstract availabl
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