排序方式： 共有7条查询结果，搜索用时 421 毫秒
1
1.
Eleonora Maccarrone Antonio Paglionico Giuseppe Piccarreta Allesandro Rottura 《Lithos》1983,16(2):95-111
In the northwestern Serre, a near continuous section through the Palaeozoic lower continental crust crops out. This paper deals with granulite facies metasedimentary rocks of this section. Fifty-five chemical analyses (major elements, Sc, V, Cr, Co, Ni, Rb, Sr, Y, Nb and Ba) are given. Chemical data indicate that the original sedimentary sequence was made up of arenites in the lower part and mainly Fe and Mg rich pelites in the upper part. The metapelites experienced anatexis and removal of some melt, whereas the meta-arenites suffered only incipient anatexis and became dehydration granulites. The various rock types display an overall relatively low K/Rb ratio due mainly to the stability of K- and Rb-retaining phases. A weighted mean composition of the fragment of the lower continental crust outcropping in the Serre has been established by integrating the chemical data for metasediments (55 analyses), metabasites (92 analyses) and dioritic and tonalitic gneisses (10 analyses) with the field data. This composition compared to the compositions of the bulk continental crust and of other sections considered as belonging to the lower crust, confirms the hypothesis that (1) the lower crust is heterogeneous, and (2) it is more basic than the continental crust. 相似文献
2.
Weathering and transportation studies of the chemical composition of sediments have determined how surface fractionation processes modify the elemental signature due to provenance and tectonic setting of siliciclastic rocks. Although the bulk of the exposed upper continental crust comprises granitoids, metamorphic rocks from the intermediate to lower crust may be, in some geological contexts, the provenance of siliciclastic sediments. A preferential enrichment of the LREE relative to the HREE is observed in weathered, garnet-rich, kinzigitic paragneisses from the Calabrian Arc, southern Italy. This fractionation is due mostly to the mineralogical control exerted by monazite, which is concentrated in the silt-size fraction of the soil. However, a significant part of HREE, released during garnet alteration, is trapped by secondary minerals in the clay-sized fraction of the soil, in a manner similar to Pb2+ and Cs+ , cations of some concern in environmental geochemistry. In the weathered material monazite is also important in controlling the Eu-anomaly, the negative size of which increases with increasing Th addition. The Eu-anomaly in the clay-sized fraction of the soil is very similar to that of the fresh rock, suggesting that the Eu/Eu* index in pelitic sediments deriving from the intermediate to lower crust may be regarded as a reliable indicator of parental affinity. Other provenance indicators include La/Th, which share the same mineralogical control; indicators of contrasting mafic and felsic provenance, e.g. Sc/Th, should be used with care. 相似文献
3.
Aldo Del Moro Antonio Paglionico Giuseppe Piccarreta Alessandro Rottura 《Tectonophysics》1986,124(3-4)
Conflicting opinions exist concerning the structure and the post-Hercynian evolution of the Serre. The present paper deals with these topics on the basis of new geological, petrological and radiometric evidence. The composition of the so-called Stilo and Polia-Copanello units has been redefined. The above domains—former sections of upper and lower Palaeozoic continental crust respectively—came into contact, due to transcurrent movements 130–140 Ma ago. A significant vertical component during the transcurrent movements, probably, exhumed the former section of lower crust. The above domains, juxtaposed, were successively involved as a single kinematic body in the Alpine orogenesis. The results enable us to make inferences for the Calabrian Arc evolution and call attention to similarities between an Austro-Alpine element (Stilo + Polia-Copanello) of the Calabrian chain and a South-Alpine sector of the Alps (Ivrea + Ceneri zones). 相似文献
4.
Origin and significance of the Permian high-K calc-alkaline magmatism in the central-eastern Southern Alps, Italy 总被引：15，自引：0，他引：15
A. Rottura G. M. Bargossi A. Caggianelli A. Del Moro D. Vison C. A. Tranne 《Lithos》1998,45(1-4):329-348
The Atesina Volcanic District, the Monte Luco volcanics, and the Cima d'Asta, Bressanone-Chiusa, Ivigna, Monte Croce and Monte Sabion intrusions, in the central-eastern Southern Alps, form a wide calc-alkaline association of Permian age (ca. 280–260 Ma). The magmatism originated during a period of post-orogenic extensional/transtensional faulting which controlled the magma ascent and emplacement. The magmatic products are represented by a continuum spectrum of rock types ranging from basaltic andesites to rhyolites, and from gabbros to monzogranites, with preponderance of the acidic terms. They constitute a metaluminous to weakly peraluminous series showing mineralogical, petrographic and chemical characteristics distinctive of the high-K calc-alkaline suites. In the MORB-normalized trace element diagrams, the most primitive volcanic and plutonic rocks (basaltic andesites and gabbros with Mg No.=66 to 70; Ni=25 to 83 ppm; Cr=248 to 679 ppm) show LILE and LREE enriched patterns with troughs at Nb–Ta and Ti, a distinctive feature of subduction-related magmas. Field, petrographic, geochemical and isotopic evidence (initial 87Sr/86Sr ratios from 0.7057 to 0.7114; εNd values from −2.7 to −7.4; ∂18O values between 7.6 and 9.5‰) support a hybrid nature for both volcanic and plutonic rocks, originating through complex interactions between mantle-derived magmas and crustal materials. Only the scanty andalusite–cordierite and orthopyroxene–cordierite bearing peraluminous granites in the Cima d'Asta and Bressanone-Chiusa intrusive complexes can be interpreted as purely crustal melts (initial 87Sr/86Sr=0.7143–0.7167; initial εNd values between −7.9 and −9.6, close to average composition of the granulitic metasedimentary crust from the Ivrea Zone in the western Southern Alps). Although the Permian magmatism shows geochemical characteristics similar to those of arc-related suites, palaeogeographic restorations, and geological and tectonic evidence, seem not to support any spatial and/or temporal connection with subduction processes. The magmatism is post-collisional and post-orogenic, and originated in a regime of lithospheric extension and attenuation affecting the whole domain of the European Hercynian belt. A change in the convergence direction between Gondwana and Laurasia, combined with the effects of gravitational collapse of the Hercynian chain, could have been the driving mechanism for lithosphere extension and thinning, as well as for upwelling of hot asthenosphere that caused thermal perturbation and magma generation. In the above context, the calc-alkaline affinity and the orogenic-like signature of the Permian magmatism might result from extensive contamination of basaltic magmas, likely derived from enriched lithospheric mantle source(s), with felsic crustal melts. 相似文献
5.
The 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 brittle–ductile 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. 相似文献
6.
Yi Zhang Xingmin Meng Allesandro Novellino Tom Dijkstra Guan Chen Colm Jordan Yuanxi Li Xiaojun Su 《Landslides》2022,19(1):35-50
Landslides - At 6pm on July 19, 2019, the Yahuokou earthflow (Zhouqu County, Gansu Province, China) was reactivated following a period of intense rainfall. A volume of approximately... 相似文献
7.
A. Langone E. Gueguen G. Prosser A. Caggianelli A. Rottura 《Journal of Geodynamics》2006,42(4-5):140-158
Hercynian 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. 相似文献
1