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Locally Thin Crust and High Crustal V P / V S Ratio Beneath the Armenian Volcanic Highland of the Lesser Caucasus: A Case for Recent Delamination
Author(s) -
Lin ChihMing,
Tseng TaiLin,
Meliksetian Khachatur,
Karakhanyan Arkady,
Huang BorShouh,
Babayan Hektor,
Hu JyrChing,
Gevorgyan Mikayel,
Chang ShuoFen,
Levonyan Ara
Publication year - 2020
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb019151
Subject(s) - geology , crust , stratovolcano , lithosphere , continental crust , geochemistry , mantle (geology) , basalt , lava , volcano , andesite , seismology , volcanic rock , petrology , tectonics
The Arabia‐Eurasia continental collision created the Caucasus Mountains and the Anatolian and Iranian plateaus. Between the two plateaus, the Armenian Highland features young Holocene‐aged volcanoes. In this study, the P ‐wave receiver functions from a new seismic array reveal a thick crust (up to ~52 km thick) beneath the Central Greater Caucasus and an unusually thin crust (32–35 km thick) beneath the northwestern part of Armenia near the Aragats stratovolcano and Gegham volcanic ridge formed by Pleistocene to Holocene monogenetic cinder cones. The average crustal V P / V S ratio in the Armenian Highland is anomalously high ( ≥ 1.9), with the highest value approaching 2.1 under the Gegham Ridge. Such high V P / V S ratios cannot be explained by an overall mafic crustal composition. Instead, the presence of partial melts is inferred in the lower crust based on the depth of the low‐velocity structure obtained by inversion of receiver function waveforms. Our study suggests that the postcollisional volcanism was potentially facilitated by the small‐scale removal of lithospheric mantle, resulting in a localized thinner crust balanced by thermal buoyancy and dynamic flow in the uppermost mantle beneath the Armenian Highland.