Geodynamic constraints deciphered from the petrology and geochemistry of the Late Cretaceous granitoids from Anafi island (Cyclades - Greece)

2021 ◽  
Author(s):  
Petros Koutsovitis ◽  
Konstantinos Soukis ◽  
Panagiotis Voudouris ◽  
Stylianos Lozios ◽  
Theodoros Ntaflos ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Mineral Chemistry ◽  
Crustal Assimilation ◽  
Corner Flow ◽  
Granitoid Magma ◽  
Thrust Sheets ◽  
Petrology And Geochemistry ◽  
Crystallization Conditions ◽  
Structural Levels ◽  
Temperature Crystallization

<p>In the Aegean region (Cyclades - Greece), the island of Anafi island comprises Late Cretaceous intermediate and felsic granitoids that intruded within exhumed HT/LP metamorphic sequences that include amphibolites, serpentinites and metasediments. The granitoids correspond to I-type arc-related rocks with calc-alkaline geochemical affinities. Variations in their petrography mineral chemistry and geochemical features are attributed to magma differentiation with removal of plagioclase and/or K-feldspar, but also amphibole and biotite. Differentiation processes of the upwelling granitoid magma included fractional crystallization accompanied with crustal assimilation, pointing to interaction with the overriding continental crust. Mineral chemistry and geochemical results display that the Anafi granitoids are highly comparable with the Late Cretaceous granitoids of East Crete and Donousa island suggesting that this magmatic activity was not a local event. Geothermometric results show relatively moderate temperature crystallization conditions (~790 °C) for the compositionally intermediate granitoids, which are and lower for the felsic granitoids (~630 °C). Geobarometric calculations suggest shallow intrusion conditions (~2.0-6.5 kbar), which corresponds to a depth of crystallization of ~12 ± 4 km.</p><p>The thrust sheets that overly the flysch constitute a subducted and metamorphosed oceanic sequence, that after the intrusion of the granitoids was exhumed from the Late Cretaceous to the Late Oligocene. These metamorphic units likely represent a part of the Pindos - CBU domain that was subducted at an earlier pre-Campanian stage. In the hydrated mantle wedge, incorporation of shallow level granitoids within metamorphic units was likely facilitated via corner flow intrusion mechanisms. Ongoing underplating of subducted material gradually brought the granitoids along with the host units to shallow structural levels and on top of the parautochtonous flysch.</p>

A Cretaceous Neo-Tethyan carbonate margin in Argolis, southern Greece

1990 ◽  
Vol 127 (4) ◽  
pp. 299-308 ◽  
Author(s):  
Peter D. Clift ◽  
Alastair H. F. Robertson
Keyword(s):  
Late Cretaceous ◽  
Foreland Basin ◽  
Ocean Basin ◽  
Passive Margin ◽  
Accretionary Complex ◽  
Early Tertiary ◽  
Thrust Sheets ◽  
Pelagonian Zone ◽  
Structural Levels ◽  
Southern Greece

AbstractThe Argolis Peninsula, southern Greece, is believed to form part of a Pelagonian microcontinent located between two oceanic basins, the Pindos to the west and theVardar to the east, in Triassic to Tertiary time. In eastern Argolis, two important units are exposed: (i) the Ermioni Limestones cropping out in the southwest; (ii) the Poros Formation, observed on an offshore island in the northeast, and on the adjacent mainland. Both these units comprise late Cretaceous (Aptian-Maastrichtian) pelagic limestones, calciturbidites, lenticular matrix- and clast-supported limestone conglomerates and slump sheets. However, the Poros Formation is distinguished from the Ermioni Limestones by the presence of bituminous micritic limestones and an increasing proportion of shale up sequence. These successions are deep-water slope carbonates that once formed the southeast-facing passive margin of the Pelagonian platform (Akros Limestone). Beyond this lay a late Cretaceous ocean basin in the Vardar Zone. This ocean was consumed in an easterly-dipping subduction zone in latest Cretaceous (?) to early Tertiary time, giving rise to an accretionary complex (Ermioni Complex). During early Tertiary (Palaeocene-Eocene) time the passive continental margin (Pelagonian Zone) collided with the trench and accretionary complex to the east. As the suture tightened, former lower-slope carbonates (Ermioni Limestones) were accreted to the base of the over-riding thrust sheets and emplaced onto the platform. Farther west, bituminous upper slope carbonates (Poros Formation) flexurally subsided and passed transitionally upwards into calcareous flysch and olistostromes in a foreland basin. These sediments were then overridden by the emplacing thrust stack and themselves underplated. Late-stage high-angle faulting then disrupted the tectonostratigraphy, in places juxtaposing relatively high and low structural levels of the complex.

Mineral chemistry and geothermobarometry of the Balıkesir Volcanites (NW Anatolia, Turkey) 

2021 ◽  
Author(s):  
Alp Ünal ◽  
Şafak Altunkaynak
Keyword(s):  
Mineral Composition ◽  
Magma Chamber ◽  
Magma Mixing ◽  
Textural Properties ◽  
Mineral Chemistry ◽  
Oscillatory Zoning ◽  
Magma Chamber Processes ◽  
Crystallization Conditions ◽  
Compositional Variations ◽  
Opaque Minerals

<p>Balıkesir Volcanites (BV) are included into the Balıkesir Volcanic Province and contain various products of Oligo-Miocene volcanic activity in NW Anatolia. BV are formed from trachyandesite, andesite and dacite lavas with associated pyroclastic rocks. In this study, we report the petrographical investigations, mineral chemistry results and geothermobarometry calculations of the Balıkesir Volcanites in order to deduce the magma chamber processes and crystallization conditions. Andesites present a mineral composition of plagioclase (An35–50) + amphibole (edenitic hornblende) +biotite ± quartz and opaque minerals. The major phenocryst phases in dacite lavas are plagioclase (An39–53), quartz, amphibole (magnesio-hornblende), biotite, sanidine and opaque minerals. The mineral composition of the trachyandesites, on the other hand, is represented by plagioclase (An38–57) + amphibole (pargasitic hornblende) + biotite + clinopyroxene (endiopside- augite) ± sanidine ± quartz ± opaque minerals. Balıkesir Volcanites present distinct textural properties such as rounded plagioclase phenocrysts with reaction rims, oscillatory zoning, honeycomb and sieve textures in plagioclase, reverse mantled biotite and hornblende crystals. The plagioclase- amphibole geothermobarometry calculations of Balıkesir volcanites indicate that, andesite and dacite lavas present similar crystallization temperature and pressures conditions of 798- 813°C and 1,98- 2.17 kbar. Oppositely, trachyandesites were crystallized under 857°C and 3,72 kbar temperature and pressure conditions. These results show that the andesite and dacite lavas were originated from the same magma chamber with the depth of 7km whereas trachyandesites were evolved in a deeper magma chamber with 13 km depth. Combined mineral chemistry, petrography and geothermobarometry studies indicate that the open system processes such as magma mixing/mingling and/or assimilation fractional crystallization (AFC) were responsible for the textural and compositional variations of the Balıkesir Volcanites.</p>

scholarly journals Tectonic denudation of a Late Cretaceous–Tertiary collisional belt: regionally symmetric cooling patterns and their relation to extensional faults in the Anatolide belt of western Turkey

2003 ◽  
Vol 140 (4) ◽  
pp. 421-441 ◽  
Author(s):  
UWE RING ◽  
CHRISTOPHER JOHNSON ◽  
RALF HETZEL ◽  
KLAUS GESSNER
Keyword(s):  
Late Cretaceous ◽  
Metamorphic Core Complex ◽  
Early Miocene ◽  
Second Phase ◽  
Late Oligocene ◽  
Core Complex ◽  
Cooling History ◽  
Western Turkey ◽  
Structural Levels ◽  
Metamorphic Core

Thermochronological data reveal that the Late Cretaceous–Tertiary nappe pile of the Anatolide belt of western Turkey displays a two-stage cooling history. Three crustal segments differing in structure and cooling history have been identified. The Central Menderes metamorphic core complex represents an ‘inner’ axial segment of the Anatolide belt and exposes the lowest structural levels of the nappe pile, whereas the two ‘outer’ submassifs, the Gördes submassif to the north and the Çine submassif to the south, represent higher levels of the nappe pile. A regionally significant phase of cooling in the Late Oligocene and Early Miocene affected the outer two submassifs and the upper structural levels of the Central Menderes metamorphic core complex. In the northern part of the Gördes submassif, cooling was related to top-to-the-NNE movement on the Simav detachment, as the apatite fission-track ages show a northward-younging trend in the direction of movement on this detachment. In the Çine submassif, relatively rapid cooling in Late Oligocene and Early Miocene times may have been related to top-to-the-S extensional reactivation of the basal thrust of the overlying Lycian nappes. The second phase of cooling in the Anatolide belt is related to Pliocene to Recent extension resulting in the formation of the Central Menderes metamorphic core complex in the inner part of the Anatolide belt. Core-complex development caused the formation of supra-detachment graben, which document the ongoing separation of the Central Menderes metamorphic core complex from the outer submassifs.

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