 |
| Titel |
Petrology and geochemistry of late Cretaceous lamprophyric rocks from North Anatolian Ophiolitic Melange-Turkey |
| VerfasserIn |
Fatma Gulmez, Can Genç, Dejan Prelevic |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099161
|
| Publikation (Nr.) |
 EGU/EGU2014-14914.pdf |
|
|
|
|
|
| Zusammenfassung |
| The late Cretaceous lamprophyric rocks from Amasya and Kalecik region occur as dykes,
stocks and lava flows intruding volcanoclastic sequence of North Anatolian Ophiolitic
Melange. Their major and trace element compositions are very similar and it is not possible
to discriminate them as two subgroups according to their geochemical features. The
Al2O3 contents are variable, but relatively high (10.66-18.77 wt.%) typical for
the ultrapotassic rocks from active orogenic belts. K2O contents (wt.% 1.22-8.39)
are variable and Mg numbers (41-60) indicate that they were crystallized from
evolved melts. LILE enrichments relative to HFSE, depletions of Nb-Ta and Ti
elements are the characteristic features on N-MORB-normalized spider diagrams and
this pattern represent the addition of subducted sediment/melt to the source area
.
The main mineralogic composition of samples from each two regions is clinopyroxene +
mica ± feldspar ± olivine ± amphibole ± leucite + opaque minerals. The significant
difference is the presence of plagioclase (An47-65) and K-feldspar as matrix in Amasya
samples. Also some of the samples from Kalecik contain minor leucite. Based on the mineral
paragenesis, Amasya lampropyres are classified as minette-vogesite and Kalecik samples
are classified as kersantite-vogesite. Clinopyroxenes are mainly diopsite, salite
and fassaitic in composition (Wo 45-50En 26-43 Fs 10-16) for the Kalecik region
and displays diopsitic-salitic composition (Wo 44-48En 38-47 Fs 6-16) in Amasya
region.
The pressure-temperature calculations reveal significant differences for the lamprophyres
from Amasya and Kalecik regions. The pressure conditions of the clinopyroxene
crystallization for Amasya samples are between 16-24 kbar corresponds to 48-72 Km depth
while the crystallization depth of the clinopyroxene from Kalecik lamprophyres is restricted
between 12-36 Km.
Although ultrapotassic rocks in Turkéy are the products of extension related
volcanism in a post-collisional setting, Cretaceous lamprophyric rocks from Amasya and
Kalecik regions formed during the closure of Neo-Tethys that means they are either
subduction related or generated during incipient phases of postcollisional relaxation. |
|
|
|
|
|
|