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1.
In this contribution, we present a virtual voyage through 3D structures generated by chaotic mixing of magmas and numerical
simulations with the aim to highlight the power of 3D representations in the understanding of this geological phenomenon.
In particular, samples of mixed juveniles from Salina island (Southern Italy) are reconstructed in 3D by serial lapping and
digital montage and numerical simulations are performed by using a 3D chaotic dynamical system. Natural and simulated magma
mixing structures are visualized by using several multimedia tools including animations and “virtual reality” models. It is
shown that magma interaction processes can generate large spatial and temporal compositional heterogeneities in magmatic systems.
The same topological structures are observed in both 3D reconstructed rock samples and chaotic numerical simulations, indicating
that the mixing of magmas is governed by chaotic dynamics. The use of 3D multimedia models gives the opportunity to penetrate
into magma mixing structures and to understand their significance in the context of magma dynamics. Such an approach is very
powerful since multimedia tools can strongly capture the attention of the reader bringing him/her into an interactive and
memorable geological experience.
Electronic supplementary material enclosed: 相似文献
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3.
Petrogenesis of calc-alkaline,shoshonitic and associated ultrapotassic Oligocene volcanic rocks from the Northwestern Alps,Italy 总被引：1，自引：0，他引：1
G. Venturelli R. S. Thorpe G. V. Dal Piaz A. Del Moro P. J. Potts 《Contributions to Mineralogy and Petrology》1984,86(3):209-220
Along the Western Alps there is geological evidence of late-Alpine (Oligocene) magmatic activity which clearly postdates the
Lepontine (Eocene-early Oligocene) metamorphism and related deformation of the Alpine nappe pile. This magmatic activity was
notably delayed in relation to the most important convergent processes and may be related to buoyancy of lithosphere, tensional
tectonics and thermal updoming subsequent to the collision between the Eurasian and African plates. The geochemical features
of the rocks and the geophysical characteristics of the Alpine chain, suggest that: (a) shoshonitic and calcalkaline melts
may have been generated by partial melting of metasomatized peridotitic material and subsequent fractional crystallization
and crustal contamination; silicic andesites and latites, however, could have been also derived from metasomatized eclogite
or deep continental crust material; (b) the ultrapotassic lamprophyres with high K, P, LREE, Th, Zr, U and high 87Sr/86Sr ratios were generated by partial melting of strongly metasomatized mantle; the varied Sr-isotopic ratios may partially
also reflect additional radiogenic component from the continental crust following magma segregation from the source. 相似文献
4.
Summary A metadolerite of the ophiolites of the Northern Apennines (Vignola, Panaro Valley, near Modena, Italy) behaves as ocean-floor tholeiites when Ti, P, Zr, Cr, Y and Nb are considered. However, it deviates from typical oceanic tholeiites in that(1) it contains primary alkali amphiboles, (2) its clinopyroxenes plot in the diagram TiO2–MnO–Na2O not in the fields of the ocean-floor basalts, and (3) the calculated uranium content of the liquid in equilibrium with its magmatic minerals is similar to the one reported for alkali basalts.These results put constraints on the generalized significance attributed to the ophiolites of the Northern Apennines, i. e. not all of them were generated at spreading ridges similar to the normal ridge segments of the present-day ocean-floors, as has been generally accepted by now.The metamorphic parageneses indicate that the rock underwent low-pressure transformations, probably in oceanic environment, followed by recrystallizations at higher pressure, reasonably in concomitance with an orogenesis.
With 4 Figures 相似文献
Klinopyroxene und Amphibole in einem Metadolerit aus dem Nördlichen Apennin. Folgerungen für die paläogeographische Stellung der Ophiolithe
Zusammenfassung Ein Metadolerit aus den Ophiolithen des Nördlichen Apennins (Vignola im Panaro-Tal bei Modena, Italien) entspricht in den Gehalten an Ti, P, Zr, Cr, Y und Nb den Tholeiiten der Ozeanböden. Er weicht hingegen von typischen ozeanischen Tholeiiten dadurch ab, daß er 1. primäre Alkaliamphibole enthält, daß 2. seine Klinopyroxene im Diagramm TiO2–MnO–Na2O nicht in die Felder der Tholeiite der Ozeanböden fallen und daß 3, der berechnete U-Gehalt für die mit seinen magmatischen Mineralen im Gleichgewicht stehenden liquiden Phase ähnlich jener ist, die für Alkalibasalte angegeben wird.Diese Ergebnisse schränken die generelle Bedeutung, die den Ophiolithen des Nördlichen Apennins bisher allgemein zugeschrieben wurde, ein: Nicht alle entstanden an sich ausdehnenden Rücken ähnlich jenen der heutigen Ozeanböden.Die metamorphen Parageneses zeigen, daß das Gestein bei niedrigem Druck, wahrscheinlich in ozeanischer Umgebung, Umwandlungen erlitt; dann folgten Rekristallisationen unter höherem Druck, die wohl zeitlich mit einer Orogenese zusammenfielen.
With 4 Figures 相似文献
5.
Diego Perugini Giampiero Poli George Christofides George Eleftheriadis Antonis Koroneos Triantafyllos Soldatos 《Geological Journal》2004,39(1):63-80
Two distinct groups of subduction‐related (orogenic) granitoid rocks, one Jurassic and the other Tertiary, occur in the area between the Vardar (Axios) Zone and the Rhodope Massif in northern Greece. The two groups of granitoids differ in many respects. The first group shows evolved geochemical characters, it is not associated with mafic facies, and evidence of magmatic interaction between mantle‐ and crustal‐derived melts is lacking. The second group has less evolved geochemical characters, it is associated with larger amount of mafic facies, and magmatic interaction processes between mantle‐derived and crustal melts are ubiquitous as evidenced by mafic microgranular enclaves and synplutonic dykes showing different enrichment in K2O, Ti, and incompatible elements. This kind of magmatism can be attributed to the complex geodynamic evolution of the area. In particular, we suggest that two successive subduction events related to the closure of the Vardar and the Pindos oceans, respectively, occurred in the investigated area from Late Jurassic to Tertiary. We relate the genesis of Jurassic granitoids to the first subduction event, whereas Tertiary granitoids are associated with the second subduction. Fluids released by the two subducted slabs induced metasomatic processes generating a ‘leopard skin’ mantle wedge able to produce mafic melts ranging from typical calc‐alkaline to ultra‐potassic. Such melts interacted in various amounts with crustal calc‐alkaline anatectic melts to generate the wide spectrum of Tertiary granitoids occurring in the study area. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
6.
Observations of Comet 9P/Tempel 1 around the Deep Impact event by the OSIRIS cameras onboard Rosetta
Horst Uwe Keller Sonia Fornasier Stubbe F. Hviid Jörg Knollenberg Miriam Rengel Gabriele Cremonese Detlef Koschny Ekkehard Kührt Holger Sierks Cesare Barbieri Hans Rickman Michael F. A'Hearn Maria-Antonella Barucci Vania da Deppo Björn J.R. Davidsson Stefano Debei Fritz Gliem José J. Lopez Moreno Giampiero Naletto Angel Sanz Andrés 《Icarus》2007,187(1):87-103
The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel 1 from 5 days before to 10 days after it was hit by the Deep Impact projectile. The Narrow Angle Camera (NAC) monitored the cometary dust in 5 different filters. The Wide Angle Camera (WAC) observed through filters sensitive to emissions from OH, CN, Na, and OI together with the associated continuum. Before and after the impact the comet showed regular variations in intensity. The period of the brightness changes is consistent with the rotation period of Tempel 1. The overall brightness of Tempel 1 decreased by about 10% during the OSIRIS observations. The analysis of the impact ejecta shows that no new permanent coma structures were created by the impact. Most of the material moved with . Much of it left the comet in the form of icy grains which sublimated and fragmented within the first hour after the impact. The light curve of the comet after the impact and the amount of material leaving the comet ( of water ice and a presumably larger amount of dust) suggest that the impact ejecta were quickly accelerated by collisions with gas molecules. Therefore, the motion of the bulk of the ejecta cannot be described by ballistic trajectories, and the validity of determinations of the density and tensile strength of the nucleus of Tempel 1 with models using ballistic ejection of particles is uncertain. 相似文献
7.
Geochronology and magmatic character of the pliocene-pleistocene volcanism in Sardinia (Italy) 总被引：2，自引：0，他引：2
L. Beccaluva M. Deriu G. Macciotta C. Savelli G. Venturelli 《Bulletin of Volcanology》1977,40(3):153-168
The Pliocene-Pleistocene subaerial volcanic activity of the island of Sardinia developed from about five million years ago to the Pleistocene. Volcanism was mainly fissural, related to rifting of the Sardinian crustal block and connected to intraplate tensional tectonics involving at the same time the area of the Tyrrhenian Sea. Areally the most abundant rocks are basic, ranging in serial character from alkaline to subalkaline types. In some areas intermediate and salic lavas also occur; trachytic and phonolitic rocks are mainly associated with basalts of alkaline affinity, whereas rhyolites and dacites are mainly related to subalkalic basalts. K/Ar data show that lavas of different serial character (from alkalic to subalkalic) are produced on the island within the same time range, from about four to two million years; it is to be noted, however, that the early products (about 5 million years) are mildly alkalic in character whereas most of the youngest products (0.6–0.14 million years) are strongly alkalic. 相似文献
8.
Major and minor elements have been determined on 26 samples of andesitie to rhyolitic lavas from Nevado Coropuna and Andagua valley in Southern Peru. Nevado Coropuna dating back since late Miocene is the highest stratovolcano of Peru. It is located at 150 km NW of Arequipa and at 110 km E of the Pacific coast. Andagua valley is situated at about 30 km E of Coropuna. The magmatic activity there, as shown by the presence of several cones, is more recent than that of Corpouna and is related to the tectonic graben characterizing this valley. The geological position of the valley is very important because it is near the transverse line separating the zone of rather flat subduction of the Nazca plate from another one dipping more steeply to the SE. The lavas from Andagua show higher Ti, P, Sr and alkali contents than those from Coropuna, and several display some alkaline tendency with Na affinity. No shoshonitic rocks have been found in the area. According to their geochemistry, Corpuna and Andagua andesites do not seem to have been originated by a single process. In particular, the distribution of Ni, Cr, Ti, Zr, Y, P, Nb, and Sr would exclude either adirect origin from pyrolitic materials, or aprogressive crustal contamination as the most important factors for their origin. Calculations of mineral/melt equilibria for Coropana andesites suggests crystallization processes at depth less than 35 km and H2O-understurated conditons at the time of the phenocrysts precipitation, indicating a possible high undersaturation at depth of the source zone. As lar as the rhyolites are concerned, their geochemical characteristics do not preclude a crustal origin. A statistical study of the chemical zonation of the Plio-Quaternary lavas of southern Peru has shown an increase of Ti and P contents eastward of the Chile-Peru trench. 相似文献
9.
Geochemistry of granitic rocks from the Hercynian Sardinia-Corsica batholith: Implication for magma genesis 总被引：5，自引：0，他引：5
The Sardinia-Corsica batholith was structured in the late stage of the Hercynian orogenesis. The granitoids intrude mainly metamorphic complexes grading from zeolite up to amphibolite facies. The batholith is heterogeneous consisting of complexes with different affinity, chemical composition, age and degree of deformation. The present paper reports major-and trace-element data for selected samples coming only from Sardinian outcrops.
The rocks range from gabbro-diorite to tonalite, monzogranite and leucogranite. The two latter lithologies are the most abundant, gabbrodiorites and tonalites occurring in minor amounts and mainly in northern-central Sardinia. Over 75% of the granitoids contain microgranular enclaves of magmatic origin. The age of the rocks falls in the interval between 307 and 281 Ma. Sr isotope initial ratios are high, ranging between 0.7083 and 0.7107.
REE, Rb, Sr, Ba, Zr, Th, Ta, Hf, Co and Sc abundances were determined on selected samples. All elements follow three types of trends vs. CaO, which is used as differentiation index. Two trends show positive and negative correlations while the third one shows a bell-shaped pattern. LREE have different degrees of enrichment (La = 20−120× ch) and HREE show variable fractionation with prevailing (Tb/Yb)n<1. The two peraluminous samples have very different geochemical characteristics.
From the geochemical point of view all the rocks coming from the Sardinian segment of the batholith display a typical calc-alkaline chemical character showing the imprint of both “normal and mature” continental arc geodynamic environments.
Geochemical trends suggest some petrogenetic constraints. The complete sequence of differentiation can be neither the product of crystal/liquid fractionation processes starting from a single basic parent magma nor the product of an AFC process. On the contrary, a two-stage model can be proposed. In the first stage a mafic melt of subcrustal origin interacted with monzogranitic magmas derived from 25–35% degree of melting of a crustal biotite amphibolitic source. Such a mixing process acted together with a crystal/liquid fractionation process to give tonalites and granodiorites. In the second stage lesser degrees of melting of the same crustal source could give the late-stage leucogranitic masses.
A possible scenario, able to take into account field and geochemical data, can be suggested for the genesis of this suite and we propose it as a working model for future investigations. 相似文献
10.
The ophiolitic complex of Northern Pindos (Greece) contains ocean-floor basalts and low-Ti mafic rocks. The former rocks are similar to recent mid-ocean ridge basalts with a light REE depletion and a La/Yb ratio < 2. The low-Ti rocks resemble boninites in their high Mg and very low Ti and Zr contents and in their REE patterns which have convex-downwards shape with a slight light REE enrichment. However, their Zr/Ti, Ti/V and Zr/Y ratios are lower than in boninites. Both rock-types could be generated by dynamic partial melting of a rising upper mantle diapir. Slight enrichment in light REE, Sr, Rb and Ba in low-Ti rocks could be the result of either metasomatic or alteration processes. Although a subduction zone origin of the sequence is possible, the geochemical data do not necessarily imply such a setting. 相似文献