TY  - JOUR
A1  - Sokol, Krzysztof
A1  - Halama, Ralf
A1  - Meliksetian, Khachatur
A1  - Savov, Ivan P.
A1  - Navasardyan, Gevorg
A1  - Sudo, Masafumi
T1  - Alkaline magmas in zones of continental convergence
BT  - the Tezhsar volcano-intrusive ring complex, Armenia
JF  - Lithos : an international journal of mineralogy, petrology, and geochemistry
N2  - Alkaline igneous rocks are relatively rare in settings of tectonic convergence and little is known about their petrogenesis in these settings. This study aims to contribute to a better understanding of the formation of alkaline igneous rocks by an investigation of the Tezhsar volcano-intrusive alkaline ring complex (TAC) in the Armenian Lesser Caucasus, which is located between the converging Eurasian and Arabian plates. We present new petrological, geochemical and Sr Nd isotope data for the TAC to constrain magma genesis and magma source characteristics. Moreover, we provide a new Ar-40/Ar-39 age of 41.0 +/- 0.5 Ma on amphibole from a nepheline syenite that is integrated into the regional context of ongoing regional convergence and widespread magmatism. The TAC is spatially concentric and measures similar to 10 km in diameter representing the relatively shallow plumbing system of a major stratovolcano juxtaposed by ring faulting with its extrusive products. The plutonic units comprise syenites and nepheline syenites, whereas the extrusive units are dominated by trachytic-phonolitic rocks. The characteristic feature of the TAC is the development of pseudomorphs after leucite in all types of the volcanic, subvolcanic and intrusive alkaline rocks. Whole-rock major element data show a metaluminous (Alkalinity Index = 0-0.1), alkalic and silica-undersaturated (Feldspathoid Silica-Saturation Index <0) character of the TAC. The general trace element enrichment and strong fractionation of REEs (La-N/Yb-N up to 70) indicate a relatively enriched magma source and small degrees of partial melting. All TAC rocks show a negative Nb Ta anomalies typical of subduction zone settings. The initial 87Sr/85Sr ratios (0.704-0.705) and positive sNd values (+3 to +5) indicate an isotopically depleted upper mantle and lack of significant crustal influence, which in turn suggests the TAC magma has formed via differentiation from lithospheric mantle melts.
KW  - Alkaline igneous rocks
KW  - Ring complex
KW  - Armenia
KW  - Geochemistry
KW  - Ar-40/Ar-39 dating
KW  - Pseudoleucite
Y1  - 2018
U6  - https://doi.org/10.1016/j.lithos.2018.08.028
SN  - 0024-4937
SN  - 1872-6143
VL  - 320
SP  - 172
EP  - 191
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Lepetit, Petra
A1  - Viereck, Lothar
A1  - Piper, John D. A.
A1  - Sudo, Masafumi
A1  - Gurel, Ali
A1  - Copuroglu, Ibrahim
A1  - Gruber, Manuela
A1  - Mayer, Bernhard
A1  - Koch, Michael
A1  - Tatar, Orhan
A1  - Gursoy, Halil
T1  - Ar-40/Ar-39 dating of ignimbrites and plinian air-fall layers from Cappadocia, Central Turkey: Implications to chronostratigraphic and Eastern Mediterranean palaeoenvironmental record
JF  - Chemie der Erde : interdisciplinary journal for chemical problems of the geo-sciences and geo-ecology
N2  - Magmatism forming the Central Anatolian Volcanic Province of Cappadocia, central Turkey, records the last phase of Neotethyan subduction after similar to 11 Ma. Thirteen large calc-alkaline ignimbrite sheets form marker bands within the volcano-sedimentary succession (the Urgup Formation) and provide a robust chronostratigraphy for paleoecologic evaluation of the interleaved paleosols. This paper evaluates the chronologic record in the context of the radiometric, magnetostratigraphic and lithostratigraphic controls. Previous inconsistencies relating primarily to K/Ar evidence were reason for the initiation of an integrated study which includes Ar-40/Ar-39 dating, palaeomagnetic and stratigraphic evidence. The newly determined Ar-40/Ar-39-ages (Lepetit, 2010) are in agreement with Ar/Ar and U/Pb data meanwhile published by Pauquette and Le Pennec (2012) and Aydar et al. (2012). The Ar-40/Ar-39-ages restrict the end of the Urgup Formation to the late Miocene. The paleosol sequence enclosed by the ignimbrites is thus restricted to the late Miocene, the most intense formation of pedogene calcretes correlating with the Messinian Salinity Crisis.
KW  - Ar-40/Ar-39 dating
KW  - Tephrostratigraphy
KW  - Neogene
KW  - Cappadocia
KW  - Turkey
Y1  - 2014
U6  - https://doi.org/10.1016/j.chemer.2014.05.001
SN  - 0009-2819
SN  - 1611-5864
VL  - 74
IS  - 3
SP  - 471
EP  - 488
PB  - Elsevier
CY  - Jena
ER  -