scholarly journals Middle Miocene to Recent volcanic rocks and their alteration in the Agatsuma area, Gunma Prefecture, central Japan

2016 ◽  
Vol 122 (8) ◽  
pp. 397-412
Author(s):  
Shohachi Nakamura ◽  
Koichiro Fujimoto ◽  
Toshio Nakayama ◽  
Shigeharu Houchigai
Keyword(s):  
Middle Miocene ◽  
Volcanic Rocks ◽  
Central Japan

scholarly journals Melt equilibration depths as sensors of lithospheric thickness during Eurasia-Arabia collision and the uplift of the Anatolian Plateau

Geology ◽  
2019 ◽  
Vol 47 (10) ◽  
pp. 943-947 ◽  
Author(s):  
M.R. Reid ◽  
J.R. Delph ◽  
M.A. Cosca ◽  
W.K. Schleiffarth ◽  
G. Gençalioğlu Kuşcu
Keyword(s):  
Late Miocene ◽  
Large Scale ◽  
Middle Miocene ◽  
Volcanic Rocks ◽  
Suture Zone ◽  
Arabian Plate ◽  
Seismic Structure ◽  
Eurasian Plate ◽  
Lithospheric Thickness ◽  
Anatolian Plateau

Abstract A co-investigation of mantle melting conditions and seismic structure revealed an evolutionary record of mantle dynamics accompanying the transition from subduction to collision along the Africa-Eurasia margin and the >1 km uplift of the Anatolian Plateau. New 40Ar/39Ar dates of volcanic rocks from the Eastern Taurides (southeast Turkey) considerably expand the known spatial extent of Miocene-aged mafic volcanism following a magmatic lull over much of Anatolia that ended at ca. 20 Ma. Mantle equilibration depths for these chemically diverse basalts are interpreted to indicate that early to middle Miocene lithospheric thickness in the region varied from ∼50 km or less near the Bitlis suture zone to ∼80 km near the Inner Tauride suture zone. This southward-tapering lithospheric base could be a vestige of the former interface between the subducted (and now detached) portion of the Arabian plate and the overriding Eurasian plate, and/or a reflection of mantle weakening associated with greater mantle hydration trenchward prior to collision. Asthenospheric upwelling driven by slab tearing and foundering along this former interface, possibly accompanied by convective removal of the lithosphere, could have led to renewed volcanic activity after 20 Ma. Melt equilibration depths for late Miocene and Pliocene basalts together with seismic imaging of the present lithosphere indicate that relatively invariant lithospheric thicknesses of 60–70 km have persisted since the middle Miocene. Thus, no evidence is found for large-scale (tens of kilometers) Miocene delamination of the lower lithosphere from the overriding plate, which has been proposed elsewhere to account for late Miocene and younger uplift of Anatolia.

scholarly journals VOLCANISM OF THE EARLY FORMATION STAGE OF ITURUP ISLAND (GREAT KURILE CHAIN)

2021 ◽  
pp. 87-98
Author(s):  
P.I. Fedorov ◽  
◽  
N.V. Tsukanov ◽  
A.R. Geptner ◽  
V.V. Petrova ◽  
...  
Keyword(s):  
Low Temperature ◽  
Field Strength ◽  
Partial Melting ◽  
Upper Mantle ◽  
High Field ◽  
Middle Miocene ◽  
Volcanic Rocks ◽  
High Field Strength ◽  
Iturup Island ◽  
Formation Stage

The article presents new petrogeochemical data on the Middle Miocene-Pliocene volcanic rocks from central part of Iturup Island (Great Kurile Chain). It is shown that volcanism of the Middle Miocene-Early Pliocene age in the central part of the Iturup Island took place in a suprasubduction setting. The distribution of high field strength elements (HFSE) and their ratio in the basaltoids indicate their formation upon partial melting of the depleted upper mantle, while the enrichment of rocks with large ionic lithophilic elements (LILE) indicates both a fluid mantle additive introduced into the melts during the evolution of primary magma and the participation of a low-temperature suprasubduction fluid. The established differences in the composition of the basaltoids of the frontal and rear zones due to the limited number of analyzed samples are considered preliminary. Thus, basaltoids in the rear zone are distinguished by higher concentrations of Th, Pb, HFSE (Nb, Zr, Y, Hf), relative enrichment in LREE, pronounced negative Zr and Hf anomalies, and positive Eu.

Sign in / Sign up

Export Citation Format

Share Document