Titre :

Tholeiitic to calc-alkaline and alkaline volcanisms in an extensional arc setting of a Tethyan ophiolite: insights from small-scale compositional and temporal transitions from the Dali sector (Armenia)

Auteur(s) :

Seyler, Monique [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Galoyan, Ghazar [Auteur]
Institute of Geological Sciences of the National Academy of Sciences of Armenia [IGS NAS RA]
Witt, César [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Danelian, Taniel [Auteur]
Évolution, Écologie et Paléontologie (Evo-Eco-Paleo) - UMR 8198 [Evo-Eco-Paléo (EEP)]

Titre de la revue :

Journal of Asian Earth Sciences

Pagination :

105478

Éditeur :

Elsevier

Date de publication :

2023-01

ISSN :

1367-9120

Mot(s)-clé(s) en anglais :

Tethyan ophiolite
Armenia
island-arc magmatism
enriched tholeiites
calc-alkaline and alkaline lavas

Discipline(s) HAL :

Planète et Univers [physics]

Résumé en anglais : [en]

New field and petrographic observations, combined with whole rock and mineral geochemical analyses are applied on volcanic rocks present in the Dali sector, east of Lake Sevan (Armenia). A small-scale sampling of the ...
Lire la suite >New field and petrographic observations, combined with whole rock and mineral geochemical analyses are applied on volcanic rocks present in the Dali sector, east of Lake Sevan (Armenia). A small-scale sampling of the volcanic sequence allows us to identify, for the first time in Armenian ophiolites, two groups of lavas (groups B and C1) stratigraphically and geochemically intermediate between previously recognized arc tholeiite (group A) and OIB-like (group C2) basalts. Their age is constrained by two distinct intercalated radiolarite sequences, which were dated as Tithonian – Valanginian. Group B lavas are low-K tholeiitic basalts and basaltic andesites derived from an enriched mantle source (LaN/YbN 1.8–6.1; SmN/YbN 1.3–2.4; Nb/Yb 2.0–6.7). The composition of their clinopyroxenes ranges from Ti-poor augite to Ti-rich diopside augite in correlation with higher La/Yb and Nb/Yb ratios in bulk rocks. Group C1 lavas are basaltic andesites containing Ti and Na-rich amphiboles (kaersutites, hastingsites) as major mineral phases. Three analyzed diopside-amphibole-porphyritic samples are alkaline trachybasalts (LaN/YbN 20–21; Nb/Yb 16–18). Both the group B and C1 lavas exhibit variable, although moderate, enrichments in Th/Yb for given Nb/Yb ratios and Nb negative anomalies in normalized multi-elements patterns (Nb/La 0.53–1.02), which are not correlated with the degree of enrichment of their mantle sources. Our results suggest that transitional and OIB-like volcanic lavas were generated by low- (group B) and very low- (groups C1–C2) melting of a heterogeneous mantle source in an oceanic arc–back-arc system in extension, possibly in relation with slab break-off.Lire moins >

Langue :

Anglais

Comité de lecture :

Oui

Audience :

Internationale

Vulgarisation :

Non

Collections :

• Laboratoire d'Océanologie et de Géosciences (LOG) - UMR 8187

Source :

Harvested from HAL