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  - GEN
A1  - Koehler, Jan
A1  - Zürcher, Christoph
T1  - Der Staat und sein Schatten : zur Institutionalisierung hybrider Staatlichkeit im Süd-Kaukasus
T1  - The state and its shadow : institutionalisation of hybrid states in the southern Caucasus region
N2  - This article looks at contemporary Armenia, Georgia, and Azerbaijan and addresses the question of how these states, which suffer from considerable institutional weaknesses, nevertheless retain the ability to control key aspects of statehood, first of all security and a measure of central authority. It is argued that these states invest only in selected aspects of statehood. The needed resources are mobilized by a system of informal taxes, which are then invested in certain selected core functions of statehood. This form of state depends on both formal and informal institutions, which are mutually supportive.
KW  - Georgien
KW  - Armenien
KW  - Aserbaidschan
KW  - Wechsel
KW  - Staatsaufbau
KW  - Georgia
KW  - Armenia
KW  - Azerbaijan
KW  - transition
KW  - state-building
Y1  - 2004
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-47422
ER  -