Geology, geochemistry and ⁴⁰Ar/³⁹Ar dating of Sevan ophiolites (Lesser Caucasus, Armenia): Evidence for Jurassic Back-arc opening and hot spot event between the South Armenian Bl

详细信息    查看全文

• 作者：Ghazar Galoyan ; Yann Roll ; Marc Sosson ; Michel Corsini ; S ; ra Billo ; Chrystelle Verati ; Rafael Melkonyan
• 关键词：Ophiolites ; ⁴⁰Ar/³⁹Ar ; LOT ; Back-arc ; Hot spot ; Tethys ; Lesser Caucasus ; Armenia
• 刊名：Journal of Asian Earth Sciences
• 出版年：2009
• 出版时间：February 2009
• 年：2009
• 卷：34
• 期：2
• 页码：135-153
• 全文大小：2054 K

文摘

In the Lesser Caucausus the Sevan-Akera ophiolites of N Armenia have lithological features of a slow-spreading oceanic lithosphere: serpentinites are frequently exposed and hydrothermalized at sea-floor level, plutonic rocks and dykes are rare. A complete differentiation trend is observed from mafic norites evolving to diorites and plagiogranites. Normal faults have exposed some of the deep magmatic rocks at sea-floor level. Geochemically, two distinct lava flow series have been distinguished: (1) a contaminated Mid-Oceanic Ridge Basalt (MORB) series evolving from gabbros to plagiogranites and from basalts to basaltic andesites, exhibiting slight calc-alkaline features (enrichments in Large Ion Lithophile Elements (LILE); negative anomalies in Nb–Ta and Ti relative to N-MORB); (2) an alkaline series evolving from basanites to trachy-andesites (on anhydrous basis). ⁴⁰Ar/³⁹Ar age on amphibole-bearing gabbros evidence a Middle Jurassic age (165.3 ± 1.7 Ma, 2σ) for oceanic crust formation. Structural data, including geological cross-sections and logs of the ophiolite along the northern part of Sevan Lake allow discussing the geodynamic evolution of that segment of the Amassia-Sevan-Akera ophiolitic suture zone.