Petrogenesis of contrasting Hercynian granitoids from the Calabrian Arc, southern Italy

Rottura, A.; Bargossi, Giuseppe Maria; Caironi, Valeria; Moro, A. Del; Maccarrone, E.; Macera, Patrizia; Paglionico, A.; Petrini, Riccardo; Piccarreta, G.; Poli, Guido

doi:10.1016/0024-4937(90)90019-w

Cited by 69 publications

(73 citation statements)

References 32 publications

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“…Thus, neither calcic cores nor more complex and marked zoning are found, in contrast to the other peraluminous or calc-alkaline allochthonous granites (e.g. Rottura et al 1990;. It is noteworthy that the plagioclase has the same composition over the range from tonalites to monzogranites and is also similar to that of the peraluminous granulites and leucogranites (Fig.…”

Section: (B»mentioning

confidence: 85%

“…Rb/Sr (Barbero et al 1990); crosses = cordierite bearing Hercynian batholiths (Rottura et al 1990;Andonaegui 1990); see text for explanation. metamorphic climax and its restite-rich character lead to unusual mineralogical features: plagioclase is almost unzoned and does not vary in composition from the mafic to the more felsic members of the series; K-feldspar has relatively high albitic content; cordierite has low alkali and Mn content and usually contains sillimanite inclusions; biotite has high Ti and low Alv1 contents.…”

Section: Discussionmentioning

confidence: 99%

“…8). The anatectic origin is more evident in the Layos Granite than in other peraluminous Hercynian granites (Del Moro 1987;Andona egui 1990;Barbero et al 1990;Rottura et at. 1990).…”

Section: Nature Of the Sourcementioning

confidence: 95%

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The Layos Granite, Hercynian Complex of Toledo (Spain): an example of parautochthonous restite-rich granite in a granulitic area

Barbero¹,

Villaseca²

1992

Geological Society of America Special Papers

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ABSTRACf: The Layos Granite forms elongated massifs within the Toledo Complex of central Spain. It is late-tectonic with respect to the F2 regional phase and simultaneous with the metamorphic peak of the region, which reached a maximum temperature of 800-850°C and pressures of 400-600 MPa. Field studies indicate that this intrusion belongs to the "regional migmatite terrane granite" type. This granite is typically interJayered with sill-like veins and elongated bodies of cordierite/ garnet-bearing leucogranites. Enclaves are widespread and comprise restitic types (quartz lumps, biotite, cordierite and sillimanite-rich enclaves) and refractory metamorphic country-rocks including orthogneisses, amphibolites, quartzites, con glomerates and caJc-silicate rocks.These granites vary from quartz-rich tonalites to melamonzogranites and define a S-type trend on a QAP plot. Cordierite and biotite are the mafic phases of the rocks. The particularly high percentage of cordierite (10%-30%) varies inversely with the silica content. Sillimanite is a common accessory mineral, always included in cordierite, suggesting a restitic origin. The mineral chemistry of the Layos Granite is similar to that of the leucogranites and country-rock peraluminous granulites (kinzigites), indicating a close approach to equilibrium. The uniform composition of plagioclase (An2S)' the high albitic content of the K-feldspar, the continuous variation in the Fe/Mg ratios of the mafic minerals, and the high Ti content of the biotites (2·5-6·5%) suggest a genetic relationship.Geochemically, the Layos Granite is strongly peraluminous. Normative corundum lies between 4% and 10% and varies inversely with increase in Si02. The CaO content is typically low «1·25%) and shows little variation; similarJy the LILE show a limited range. On many variation diagrams, linear trends from peraluminous granulites to the Layos Granite and associated leucogranite can be observed. The chemical characteristics argue against an igneous fractionation or fusion mechanism for the diversification of the Layos Granite. A restite un mixing model between a granulitic pole (represented by the granulites of the Toledo Complex) and a minimum melt (Jeucogranites) could explain the main chemical variation of the Layos Granite. Melting of a peiitic protolith under anhydrous conditions (biotite dehydration melting) could lead to minimum-temperature melt compositions and a strongly peraluminous residuum.For the most mafic granites (61-63% Si02), it is estimated that the trapped restite component must have been around 65%. This high proportion of restite is close to the estimated rheological critical melt fraction, but field evidence suggests that this critical value has been exceeded. This high restite component implies high viscosity of the melt which, together with the anhydrous assemblage of the Layos Granite and the associated leucogranites, indicates H20-undersaturated melting conditions. Under such conditions, the high viscosity magma (crystal-liquid mush) had a restricted movement ca...

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Section: (B»mentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

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The Layos Granite, Hercynian Complex of Toledo (Spain): an example of parautochthonous restite-rich granite in a granulitic area

Barbero¹,

Villaseca²

1992

Geological Society of America Special Papers

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“…Three extreme possibilities can potentially account for the Sr isotope decrease: (i) assimilation of unradiogenic country rock material, and (ii) gradual or (iii) instantaneous change of 87 Sr= 86 Sr in the feeding magma. Crustal assimilation is incompatible with the high 87 Sr= 86 Sr of the crustal basement of southern Italy [24,25] and also requires special pleading to preserve a substantially constant [Sr] in the erupted magma (Fig. 2).…”

Section: Discussionmentioning

confidence: 99%

Sr isotope evidence for short magma residence time for the 20th century activity at Stromboli volcano, Italy

Francalanci

Tommasini

Conticelli

et al. 1999

Earth and Planetary Science Letters

107

109

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Stromboli is the type locality of continuous and moderately explosive volcanic activity. Monitoring temporal variations in the composition of the material erupted allows constraints to be made on the magma chamber dynamics and volcanic hazard. Here we present an Sr isotope survey of scoriae and lavas erupted from Stromboli volcano during this century. The material erupted is transitional between shoshonite and High-K basalt, with relatively constant major and trace element composition. This implies no substantial physical separation of minerals during crystallization (ca. 50 vol% minerals in both lavas and scoriae) and hence a relatively homogeneous reservoir. 87 Sr= 86 Sr values are constant from 1900 to ca. 1980, then, beginning prior to the major lava flow eruption of December 1985, there is a smooth decrease. The Sr isotope decrease records the arrival of a new feeding magma, and allows estimation of the magma residence time and the volume of the reservoir beneath Stromboli volcano. Our results, along with a critical assessment of magma flux estimates, are best reconciled with steady state conditions, and establish the existence of a relatively small, ¾0.3 to 0.04 km 3 , reservoir with a magma residence time .− / of ca. 19 years. Monitoring the temporal variation of isotopic ratios in active volcanoes appears a successful tool in forecasting some major volcanic eruptions.

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“…Pet Petrazza pyroclastics (Paleostromboli I); Omo Omo lava flows (Paleostromboli II). Magma series: calc-alkaline; high-K calc-alkaline; shoshonitic; potassic Hercynian calc-alkaline and peraluminous granitoids (Rottura et al 1990 and subordinate gabbrodiorite rocks (Caggianelli et al 1994).…”

Section: Geological Settingmentioning

confidence: 99%

Origin of high-silica liquids at Stromboli volcano (Aeolian Islands, Italy) inferred from crustal xenoliths

et al. 2001

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High-silica igneous xenoliths (granophyre and obsidian fragments with SiO 2 ca. 75 wt.%) and high-silica glass (SiO 2 between ca. 64 and 75 wt.%) within glass-bearing tonalitic and dioritic xenoliths have been discovered at Stromboli. They are well beyond the silica range of the volcanic rocks erupted during the subaerial activity of the volcano. The granophyre and the obsidian fragments occur within the Petrazza pyroclastics (high-K andesite pumiceous scoriae) of the Paleostromboli I period (<100 to >61 ka), whereas the glass-bearing tonalites and diorites are hosted in the Omo basaltic-andesite lava flows of the Paleostromboli II period (64±55 ka). The obsidian represents an extremely evolved liquid derived from lowpressure fractional crystallization of high-K calc-alkaline magmas of Stromboli, coupled with minor assimilation of upper crust or terrigenous sediments. The other studied high-silica products have an anatectic origin. The granophyre composition is compatible with a genesis by low-degree melting of leucotonalites similar to some Calabrian Arc lithotypes. Partial melting of crustal rocks from the Stromboli basement is also demonstrated by interstitial glass in the tonalite and diorite xenoliths. Textural evidence and the presence of variable glass compositions suggest that in these plutonic xenoliths the melt chemistry was controlled by dehydration melting of biotite and non-modal melting of local mineralogy. High-degree undercooling of granophyre melt and of the partially melted xenoliths is consistent with rapid rise of the host magmas leading to eruption. Whether partial melting was initiated during stoping and transport of xenoliths within the rising magma or in situ during magma storage within the crust has not been unequivocally established.

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Petrogenesis of contrasting Hercynian granitoids from the Calabrian Arc, southern Italy

Cited by 69 publications

References 32 publications

The Layos Granite, Hercynian Complex of Toledo (Spain): an example of parautochthonous restite-rich granite in a granulitic area

The Layos Granite, Hercynian Complex of Toledo (Spain): an example of parautochthonous restite-rich granite in a granulitic area

Sr isotope evidence for short magma residence time for the 20th century activity at Stromboli volcano, Italy

Origin of high-silica liquids at Stromboli volcano (Aeolian Islands, Italy) inferred from crustal xenoliths

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