1,721,128 research outputs found
Strain localisation driven by marble layers: the Palmi shear zone (Calabria-Peloritani terrane, Southern Italy)
No full textWeathered biotite from granitoids: the fractionation of REE, Th and transition elements iand the role of accessory and secondary phases
No full textThe Curinga-Girifalco fault zone (northern Serre, Calabria) and its significance within the Alpine tectonic evolution of the western Mediterranean.
No full textHercynian basement rocks and Mesozoic ophiolites of the Calabria-Peloritani terrane drifted in the present position during the opening of western Mediterranean basins (namely Liguro-Provençal and Tyrrhenian basins) since the Oligocene. Basement rocks were partly involved by Alpine (late Cretaceous—Eocene) deformation and metamorphism before the onset of the drifting process. Even though the kinematics of the Alpine deformation in Calabria has been already defined, restoration of structural and kinematic data to the original position and orientation before the opening of the western Mediterranean has never been performed. In this work we present new structural and petrological data on a major tectonic contact of Alpine age exposed in central Calabria (Serre Massif). Structural and kinematic data are then restored at the original orientation in the early Oligocene time, to allow a correct tectonic interpretation.
In the Serre Massif the Hercynian basement is sliced into three nappes emplaced during the Alpine orogeny. The upper nappe is formed by a nearly continuous section of the Hercynian crust, consisting of medium- to high-grade metamorphic rocks in the lower portion. The intermediate nappe mainly consists of orthogneisses, whereas the lower nappe is chiefly composed of phyllites. The contacts between the Alpine nappes are outlined by well developed mylonitic and cataclastic rocks. The Curinga-Girifalco Line is a well exposed shear zone that overprints mainly metapelitic rocks of the upper nappe and granitoid orthogneisses of the intermediate nappe. Mylonites of the intermediate nappe typically show overgrowths on garnet and hornblende with grossular-rich and tschermakitic composition, respectively. The Alpine mineral assemblage indicates that deformation took place in epidote-amphibolite facies at pressures ranging from 0.75 to 0.9 GPa.
In the investigated area mylonites strike roughly WNW–ESE, with shallow dips towards SSW. Kinematic indicators in mylonites are mostly consistent with a top-to-the-SE shear sense in the present geographic coordinates. The mylonitic belt is affected by later extensional faults outlined by South-dipping cataclasite horizons. Published geochronological data indicate that mylonites and cataclasites developed in Eocene and early Miocene times, respectively.
Considering rotational parameters coming from paleomagnetic studies and large-scale palinspastic reconstructions, the shear sense of the Curinga-Girifalco Line has been restored to the early Oligocene position and orientation. Through restoration a top-to-the-S shear sense is obtained. This result is in striking agreement with the convergence direction between Africa and W-Europe/Iberia during Eocene, computed from the North Atlantic magnetic anomalies. Our geodynamic reconstruction, combined with structural and petrological evidence, allows to relate the Curinga-Girifalco mylonites to a thrust related to the southeastern front of the double-verging Alpine chain. The adopted method could be used also for other exotic terranes, such as the Kabylie or the Corsica-Sardinia, to better constrain geometry and evolution of the southern Alpine belt
The Hercynian evolution recorded in the Calabria-Peloritani Alpine range, southern Italy. An overview
No full textThermal history vs. fabric anisotropy in granitoids emplaced at different crustal levels: an example from Calabria, southern Italy
No full textThe Sila and Serre granitoids of Calabria were emplaced in the late
Carboniferous at depths ranging from 6 to 23 km in a postcollisional
extensional regime. Their fabric, which developed during and after final
crystallization up to the solid state, strongly increases in intensity
with emplacement depth, This relationship is attributed to the thermal
history of the Calabrian basement. Cooling histories of granitoids,
constrained by geological data and Rb-Sr cooling ages on micas,
demonstrate that residence times of rocks at temperatures greater than
those of the brittleductile transition vary greatly as a function of
initial emplacement depth. This explains why shallow-level granitoids,
that remained for about 10 Myr at temperatures above those of the
brittle domain, retain their original magmatic fabric, By contrast, the
strong fabrics of the deep-seated granitoids are explained by
solid-state strain overprint that lasted more than 100 Myr at
temperatures above those of the brittle domain
Polyphase metamorphic history revealed from garnet-core composition isopleths: an example from the low-P Hercynian basement in Sila (Calabria, Italy)
No full textSignificance of the permian magmatism of central-eastern Southern Alps, Italy: petrological and geochemical constraints
No full textStrain localisation driven by marble layers: the Palmi shear zone (Calabria-Peloritani terrane, Southern Italy)
No full textIn this study a shear zone transecting the Hercynian basement of the Calabria - Peloritani terrane in the neighbourhood of Palmi is described for the first time. A structural analysis was carried out to outline the tectonic meaning of the shear zone. In addition, thermobarometry and geochronology allowed to define the structural level and age of deformation. The shear zone is localised along layers of calc-silicate bearing marbles near the contact between late Hercynian tonalites and migmatitic paragneisses. Marbles, interpreted as former skarns, still retain the original high temperature Hercynian mineral assemblage including diopside, grossular, anorthite-rich plagioclase ± scapolite ± hornblende. Deformation took place in greenschist facies at about 400 °C and 600 MPa. This event partially affected the peak assemblage in marbles, as documented by coronas of clinozoisite around anorthite-rich plagioclase. Rb-Sr method applied on two biotite separates coming from sheared gneisses gave Eocene ages of 51 and 56 Ma. The shear zone is broadly oriented WNW - ESE and shows nearly vertical foliation planes. Large scale folds undulate the foliation planes whose direction swings from NW - SE to NE-SW. Lineations generally show a shallow plunge with trends mostly spanning from E-W to NW-SE. In some cases lineations show a wide scatter in orientation and locally can be nearly vertical. Shear sense indicators and quartz c-axis distribution are coherent with sinistral kinematics along nearly horizontal lineations, and south side up displacement along steeply plunging lineations. The Palmi shear zone is interpreted as an early Alpine sinistral transpressive belt developed within weak calc-silicate bearing marbles sandwiched between the rigid domains of tonalites and migmatitic paragneisses. Due to sinistral transpression tonalites were uplifted with respect to the migmatitic paragneisses
Petrological and geochemical evidence on the origin and significance of the permian magmatism in the Central-Eastern Southern Alps, Italy
No full textAlpine evolution of the western mediterranean: new insights from the Curinga - Girifalco fault zone (Serre Massif, Calabria)
No full text- …
