O-Sr isotopic variations in Miocene granitoids from the Aegean: evidence for an origin by combined assimilation and fractional crystallization

Altherr, Rainer; Henjes‐Kunst, Friedhelm; Matthews, Alan; Friedrichsen, Hans; Hansen, Bent

doi:10.1007/bf00371381

Cited by 93 publications

(34 citation statements)

References 48 publications

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“…Volcanic rocks in Milos and centers of the Saronic gulf (Aegina, Methana, and in particular Crommyonia) generally have more radiogenic Sr and less radiogenic Nd isotopic ratios [48,50] than Santorini and KosNisyros. Interestingly, the magmas with highest 87 Sr/ 86 Sr and lowest ε Nd in both Milos and Nisyros are the more mafic ones (andesites; [23,24,48]). The wide (and poorlydefined) range of 87 Sr/ 86 Sr and ε Nd values obtained from samples of Nile sediments are indicated for reference (e.g., [51,52]).…”

Section: Whole-rock Chemistrymentioning

confidence: 98%

“…IV(F) yields a F value corrected for Fe/Mg variation [65]. tained in the course of this study, which imply that extensive participation of the old Paleozoic-Mesozoic basement or Miocene plutons (e.g., [87]) found in the area could not have been a major component in forming the local dacites and rhyolites. In addition, the absence of xenocrystic material in more than 150 ion probe data points in KPT zircons imply that wall rocks did not contribute much to the mass of zircons (and mass of magma by inference).…”

Section: Rhyolite Differentiation Process In the Aegeanmentioning

confidence: 99%

“…However, precisely determining the relative contributions from the different reservoirs (slab, subducted sediments, asthenopheric mantle, metasomatized lithospheric mantle, overriding continental plate) in the Aegean using Sr and Nd isotopes is unachievable in the present state of knowledge. It is not surprising that the continental crust from the Aegean microplate is isotopically highly variable (e.g., 87 Sr/ 86 Sr from ∼0.704 to 0.71; see among many [87][88][89]), but it is also known that European lithospheric mantle can be highly heterogeneous ( 87 Sr/ 86 Sr >0.715; [90][91][92][93]; see also discussion in [94] and a trachyandesite clast found in the KPT, [47]), while Nile sediments show a large range of isotopic values as well (see Figure 9; [47]; [51,52]). In these conditions, mixing calculations, which require welldefined endmembers, leave significant uncertainty in the determination of the relative proportion of each endmembers in the final rhyolitic magma.…”

Section: Rhyolite Differentiation Process In the Aegeanmentioning

confidence: 99%

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The petrologic evolution and pre-eruptive conditions of the rhyolitic Kos Plateau Tuff (Aegean arc)

Bachmann

2010

Open Geosciences

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Abstract:The Kos Plateau Tuff is a large (>60 km 3 ) and young (160 k.y.) calc-alkaline, high-SiO 2 rhyolitic ignimbrite from the active Kos-Nisyros volcanic center in the Aegean arc (Greece). Combined textural, petrological and geochemical information suggest that (1) the system evolved dominantly by crystal fractionation from (mostly unerupted) more mafic parents, (2) the magma chamber grew over 250 000 years at shallow depth (∼1.5-2.5 kb) and was stored as a H 2 O-rich crystalline mush close to its solidus (∼670-750°C), (3) the eruption occurred after a reheating event triggered by the intrusion of hydrous mafic magma at the base of the rhyolitic mush. Rare banded pumices indicate that the mafic magma only mingled with a trivial portion of resident crystal-rich rhyolite; most of the mush was remobilized following partial melting of quartz and feldspars induced by advection of heat and volatiles from the underplated, hotter mafic influx.

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Section: Whole-rock Chemistrymentioning

confidence: 98%

Section: Rhyolite Differentiation Process In the Aegeanmentioning

confidence: 99%

Section: Rhyolite Differentiation Process In the Aegeanmentioning

confidence: 99%

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The petrologic evolution and pre-eruptive conditions of the rhyolitic Kos Plateau Tuff (Aegean arc)

Bachmann

2010

Open Geosciences

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“…These faults removed the overburden from above the blueschists, leaving thin remnants comprising the Upper Unit. Orogenic activity was terminated by extensive intrusion of granitoids during the Miocene (Altherr et al ,1988.…”

Section: Geological Settingmentioning

confidence: 99%

“…2). The juxtaposition of the Upper tectonic Unit must have occurred in a relatively narrow time slot, limited on the one hand by the greenschistfacies metamorphic event dated at 23 to 21 Ma (Brocker et al 1993) and by the intrusion of the 18-Ma-old granite (Altherr et al , 1988) that cuts across the tectonic contact between the Lower and Upper units (Avigad & Garfunkel, 1989). The structure of Tinos as seen today was shaped by a Miocene or younger post-metamorphic phase of deformation that acted on all tectono-metamorphic units.…”

Section: Geological Settingmentioning

confidence: 99%

The tectono-metamorphic evolution of a dismembered ophiolite (Tinos, Cyclades, Greece)

et al. 1996

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-The six exposures of the Upper tectonic Unit of the Cycladic Massif occurring on the island of Tinos are shown to comprise a metamorphosed dismembered ophiolite complex. The common stratigraphic section consisting of tens-of-metres-thick tectonic slices of mafic phyllites overlain by serpentinites and gabbros is considered to have been derived by a combination of thrusting during obduction and subsequent attenuation by low-angle normal faults. All rock types show evidence of a phase of regional greenschistfacies metamorphism, which in the case of the phyllites is accompanied by penetrative deformation. The greenschist-facies metamorphism in gabbros is preceded by high temperature sea-floor amphibolite-facies alteration, whereas in the serpentinites, the antigorite + forsterite greenschist-facies assemblage overprinted an earlier low temperature lizardite serpentinite. Trace element patterns of the mafic phyllites and a harzburgitic origin of meta-serpentinites suggest a supra subduction zone (SSZ) affinity for the ophiolitic suite. 5"O values of phyllites, gabbros and serpentinites range from 6 to 15%o. Model calculations indicate that such values are consistent with low temperature (50-200 °C) alteration of parent rocks by sea-water at varying water/rock ratios. This would agree with the early low temperature mineralogy of the serpentinites, but the early high temperature alteration of the gabbros would require the presence of "O-enriched sea-water.The following overall history is suggested for Tinos ophiolitic slices.(1) Oceanic crust was generated at a supra-subduction zone spreading centre with high temperature alteration of gabbros. (2) Tectonic disturbance (its early hot stages recorded in an amphibolitic shear zone at the base of serpentinites) brought the already cooled ultramafics into direct contact with sea-water and caused low-7* serpentinization. (3) Tectonism after cooling involved thrusting which caused repetition and inversion of the original order of the oceanic suite. (4) Regional metamorphism of all the ophiolite components at greenschist-facies conditions (~450 °C) overprinted the early alteration mineralogy. It was probably induced by continued thrusting and piling up of nappes. The Tinos ophiolite, dated as late Cretaceous and genetically related to other low pressure rock-units of the same age in the Aegean, differs in age and degree of dismemberment and metamorphism from ophiolites in mainland Greece.

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Interactions between plutonism and detachments during metamorphic core complex formation, Serifos Island (Cyclades, Greece)

et al. 2015

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In order to better understand the interactions between plutonic activity and strain localization during metamorphic core complex formation, the Miocene granodioritic pluton of Serifos (Cyclades, Greece) is studied. This pluton (11.6-9.5 Ma) intruded the Cycladic Blueschists during thinning of the Aegean domain along a system of low-angle normal faults belonging to the south dipping West Cycladic Detachment System (WCDS). Based on structural fieldwork, together with microstructural observations and anisotropy of magnetic susceptibility, we recognize a continuum of deformation from magmatic to brittle conditions within the magmatic body. This succession of deformation events is kinematically compatible with the development of the WCDS. The architecture of the pluton shows a marked asymmetry resulting from its interaction with the detachments. We propose a tectonic scenario for the emplacement of Serifos pluton and its subsequent cooling during the Aegean extension: (1) A first stage corresponds to the metamorphic core complex initiation and associated southwestward shearing along the Meghàlo Livadhi detachment. (2) In the second stage, the Serifos pluton has intruded the dome at shallow crustal level, piercing through the ductile/brittle Meghàlo Livadhi detachment. Southwest directed extensional deformation was contemporaneously transferred upward in the crust along the more localized Kàvos Kiklopas detachment. (3) The third stage was marked by synmagmatic extensional deformation and strain localization at the contact between the pluton and the host rocks resulting in nucleation of narrow shear zones, which (4) continued to develop after the pluton solidification.

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O-Sr isotopic variations in Miocene granitoids from the Aegean: evidence for an origin by combined assimilation and fractional crystallization

Cited by 93 publications

References 48 publications

The petrologic evolution and pre-eruptive conditions of the rhyolitic Kos Plateau Tuff (Aegean arc)

The petrologic evolution and pre-eruptive conditions of the rhyolitic Kos Plateau Tuff (Aegean arc)

The tectono-metamorphic evolution of a dismembered ophiolite (Tinos, Cyclades, Greece)

Interactions between plutonism and detachments during metamorphic core complex formation, Serifos Island (Cyclades, Greece)

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