The role of shallow open system processes in the evolution of South Tepeldag Pluton (NW Turkey): insights and constraints from thermodynamic modelling

2021 ◽  
Author(s):  
Tunahan Arık ◽  
Ömer Kamacı ◽  
Işıl Nur Güraslan ◽  
Şafak Altunkaynak
Keyword(s):  
Fractional Crystallization ◽  
Open System ◽  
Suture Zone ◽  
Thermodynamic Simulations ◽  
Nw Turkey ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Ophiolitic Rocks ◽  
Compositional Variations ◽  
Spider Diagrams

<p>Eocene granitoids in NW Anatolia occurred following the continental collision between Sakarya Continent and Tauride-Anatolide Platform and mark the onset of post-collisional magmatism in the region. One of the representative members of the Eocene granitoids, the Tepeldağ pluton crops out as two isolated granitic bodies and is intruded into the Cretaceous blueschist assemblages (Kocasu formation) and ophiolitic rocks within the Izmir-Ankara-Erzincan suture zone (IAESZ). South Tepeldağ pluton (STP) is composed mainly of granodiorite with subordinate quartz diorite, which show transitional contacts. Aplitic dykes crosscut the pluton as well as the country rocks. STP includes a number of mafic microgranular enclaves (MME) of gabbro/diorite composition.</p><p>Geochemically, STP shows distinct I-type affinity with a metaluminous to slightly peraluminous (ASI ≤1.02) nature. The samples are medium-K to high-K calc-alkaline in character. They exhibit depletion in HFSE (Ti, Hf, Zr, Nb and Ta) compared to large ion lithophile elements (Rb, Ba, Th, U, K) and presents negative Nb, P, Ti anomalies. STP displays slight negative Eu anomalies (Eu/Eu* = 0.7–1.2), enrichment in LREE and flat HREE patterns in chondrite-normalized spider diagrams. MELTS modeling (with initial parameters of 1–3 kbar pressure, 2–3% water and QFM-NNO oxygen fugacity buffers) indicate that compositional variations in STP samples can be interpreted as a result of open system processes (assimilation fractional crystallization) rather than a reflection of fractional crystallization in the upper crustal magma chamber. All thermodynamic simulations dictate a crustal assimilation, especially in the late stages of the magmatic process, with a MgO, Na<sub>2</sub>O and Al<sub>2</sub>O<sub>3</sub>-rich assimilant similar to the suture zone (IAESZ) rocks.</p>

scholarly journals GEOCHEMICAL CHARACTERISTICS OF THE ERENLERDAGI VOLCANICS, KONYA, CENTRAL TURKEY

2017 ◽  
Vol 50 (4) ◽  
pp. 2057
Author(s):  
C. Uyanık ◽  
K. Koçak
Keyword(s):  
Fractional Crystallization ◽  
Magma Mixing ◽  
Primitive Mantle ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
High K ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Central Turkey ◽  
Pyroclastic Fall

Late Miocene to Pliocene volcanism produced lava domes with mafic microgranular enclaves (MMEs), nuée ardentes and pyroclastic fall and flow (ignimbrites) deposits in the WSW and NW of Konya city. All samples are predominantly high K-calc alkaline in composition but calc-alkaline and shoshonitic composition also exist. The felsic volcanics are mainly dacite, andesite, basaltic trachyandesite and rare trachyandesite in compositon. But, the MMEs have basaltic andesite and andesite compositon. SiO2 increases with decreasing TiO2, FeOt, MgO and CaO, suggesting fractional crystallization of mafic minerals. All samples have fractionated chondritenormalised REE pattern (La/YbN: 6.7-18.1), and negative Eu anomaly (Eu/Eu*: 0.67- 0.89), indicating plagioclase fractionation. In primitive mantle-normalized spider diagram, the samples show an enrichment in large ion litophile elements (LILE) such as Cs and Ba, and depletion in high field strength elements (HFSE), e.g. Dy and Y. They show negative Nb, Ta and Ti anomalies, indicating a subduction signature for their genesis. Based on geochemical data, the volcanics are suggested to have been formed by Assimilation-Fractional Crystallization (AFC) and/or magma mixing process. Various geotectonic diagrams imply volcanic arc to post collisional setting for the samples.

Eclogitic rocks in the St. Cyr klippe, Yukon, and their tectonic significance

1992 ◽  
Vol 29 (6) ◽  
pp. 1296-1304 ◽  
Author(s):  
Philippe Erdmer
Keyword(s):  
High Pressure ◽  
Oceanic Crust ◽  
North American ◽  
Suture Zone ◽  
Late Paleozoic ◽  
The North ◽  
Tectonic Significance ◽  
Subducted Oceanic Crust ◽  
Ophiolitic Rocks ◽  
Subducting Slab

Until recently, the Nisutlin allochthonous assemblage, a part of the Yukon–Tanana composite terrane interpreted as trench mélange from a late Paleozoic – Mesozoic arc system, was the only tectonic assemblage known to include subducted material in the northern Cordillera. The discovery of eclogitic rocks in two parts of a klippe of the Anvil allochthonous assemblage, which comprises mafic ophiolitic rocks, above the Cassiar terrane west of the Tintina fault confirms other evidence that subducted oceanic crust was also returned to the surface. The eclogitic rocks have been largely retrograded by postsubduction metamorphism. Their existence is interpreted as additional evidence of the link between nappes above the Cassiar terrane and their inferred root, the Teslin suture zone. The Nisutlin and Anvil allochthonous assemblages can now be interpreted, not simply as crustally metamorphosed assemblages with minor, structurally interleaved high-pressure components, but as deeply metamorphosed and intensely strained slices of continental and oceanic crust switched from subducting slab to overriding plate and returned to the surface during collision of the arc with the North American margin.

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