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| Titel |
Mafic sill/dykes intruding into late Maastrichtian-early Paleocene
calciclastic units, NE-Turkey: Petrographical and geochemical features of
latest magmatic activity before collision in the eastern Sakarya zone |
| VerfasserIn |
Faruk Aydin, Simge Oğuz, Orhan Karsli, Raif Kandemir, Cüneyt Şen, İbrahim Uysal |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150387
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| Publikation (Nr.) |
 EGU/EGU2017-14844.pdf |
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| Zusammenfassung |
| We present here new petrographical, mineralogical and whole-rock geochemical data for
mafic sill/dykes intruding into late Maastrichtian-early Paleocene calciclastic units in the
Düzköy (Trabzon) and Cankurtaran (Artvin) areas (NE Turkey) of the eastern Sakarya zone
(ESZ) in order to decipher the latest magmatic activity in the final stage of subduction-related
magmatism of the ESZ. U-Pb zircon dating for the mafic sill/dykes in the region yielded ages
varying from 83.6 to 78.5Ma (i.e. Early Campanian). Mafic sill/dykes consist of mostly
basalts and lesser basaltic-andesites with komatiitic basalts. Most of the dyke samples display
aphyric to porphyritic texture with phenocrysts of plagioclase (mostly replaced by calcite),
clinopyroxene (partly uralized), olivine (almost serpentinized), and amphibole (partly
chloritized).
Based on the MgO, Nb and Zr contents with Nb/Y ratio, the mafic dykes from Düzköy
area are mainly classified as two subgroups (basalts and basaltic andesites) while those of
Cankurtaran can be divided into three different groups (low- and high-Nb normal basalts and
komatitic basalts). Düzköy basaltic dykes have higher MgO (3.8-7.8%) and lower Nb
(3-4ppm) and Zr (53-62ppm) contents with Nb/Y ratio (∼0.2) than those of Düzköy
basaltic-andesitic dykes (MgO: ∼1.8%, Nb: 6-15ppm, Zr: 106-145ppm, Nb/Y: 0.3-0.6). On
the other hand, Cankurtaran mafic sill/dykes have relatively high MgO contents
(∼4-20%). These sill/dykes with 15-20% of MgO and <1% TiO2 contents are
called as komatiitic basalt which has relatively low K2O (<1%), Nb (∼1ppm), Zr
(23-26ppm) and Y (8ppm) contents with Nb/Y ratio (∼0.1-0.2). However, normal
basalts from Cankurtaran have quite lower MgO contents (∼4-9%) than that of
the komatiitic basalt. Also, they can be divided into two subgroups in terms of
MgO (5.7-8.7% for group 1 and 4.0-4.4% for group 2), Nb (3-14ppm for group
1 and 19-21ppm for group 2), Zr (94-111ppm for group 1 and 125-140ppm for
group 2) contents, and Nb/Y ratio (∼0.2-0.8 for group 1 and (∼1.0-1.2 for group
2).
Although the studied mafic sill/dykes have generally subalkaline composition, they show
a geochemical character changing from mostly tholeiitic to rarely calc-alkaline and show
typical features of late Cretaceous subduction-related magmatic rocks as in the
ESZ. On the chondrite-normalized REE patterns, the sill/dykes show enrichment
in LREEs, and show variable LREE/HREE fractionation (La/Yb)N=6.6-10.5 for
Düzköy and 6.2-24.5 for Cankurtaran) but similar Eu anomalies (Eu/Eu*=∼0.9-1.0
for all the dykes). On the N-MORB normalized diagrams, the mafic sill/dykes are
generally enriched in LILEs and depleted in HFSEs with Nb and Ti, suggesting
that the mantle source has compositional similarity with metasomatized mantle
wedge. These data reflect a genetic relationship between the komatiitic-basaltic and
basaltic-andesitic sill/dykes through fractional crystallization process with some crustal
contamination.
Acknowledgments
This study was supported by Karadeniz Technical University with FBA-2015-5314
project. |
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