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- Title
Thermal Evolution of the Lithosphere‐Asthenosphere Boundary Beneath Arc and Its Geodynamic Implications: Depth Variation of Thermal Histories of Mantle Xenoliths From Ichinomegata, Northeast Japan.
- Authors
Sato, Yuto; Ozawa, Kazuhito
- Abstract
Quantitative reconstruction of thermal history recorded in mantle xenoliths is imperative for understanding the temporal change of thermal state and dynamics of the lithosphere‐asthenosphere boundary (LAB). We challenged this problem in the arc settings by examining nine spinel peridotite xenoliths from Ichinomegata maar in the back‐arc side of Northeast Japan Arc. Extensive mineral chemical analyses combined with the derivation depths of the xenoliths revealed a depth‐dependent variation of chemical zoning patterns in olivine and pyroxenes. The depth variation of thermal histories of the Ichinomegata xenoliths was decoded by applying diffusion‐controlled reaction modeling to reproduce the zoning patterns. The decoded thermal events in the order of occurrence are (a) ∼14 million years of cooling causing lithosphere thickening up to ∼55 km depth, (b) subsequent ∼12 thousand years of heating from the underlying asthenosphere resulting in lithosphere thinning up to the depths of ∼40 km, and (c) 1–68 days of heating during xenolith transportation by the host magma. The duration of the lithosphere thickening is consistently explained by the period of the Japan Sea opening. On the other hand, the timescale of the lithosphere thinning is too short to be explained by heat conduction through the ∼15 km thick LAB and requires a more effective heat transportation mechanism such as direct magma injection into the LAB or significant viscosity reduction of the mantle peridotite aided by the pervasive permeable flow of silicate melt. Plain Language Summary: Evolution of the lithosphere (tectonic "Plate" in the framework of plate tectonics) accompanies dynamic change of the depth of the lithosphere‐asthenosphere boundary (bottom of the "Plate"), which causes the temporal change of thermal structure in the mantle. We challenged quantitative estimation for the timescale of such temporal change in the arc settings by examining the chemical heterogeneities recorded in olivine and pyroxene of the mantle xenoliths (fragments of mantle materials brought up by magma) from Ichinomegata maar in the back‐arc side of the Northeast Japan Arc. The decoded thermal events in the order of occurrence are (a) ∼14 million years of cooling causing thickening of the lithosphere up to ∼55 km depth, (b) subsequent ∼12 thousand years of heating from the underlying asthenosphere resulting in thinning of the lithosphere up to the depths of ∼40 km, and (c) 1–68 days of heating during xenolith transportation by the host magma. The lithosphere thickening is consistently explained by the long cooling event since the back‐arc spreading event in the Japan Sea. On the other hand, the timescale of the lithosphere thinning requires a more effective heat transportation mechanism such as direct magma injection or significant viscosity reduction of the mantle. Key Points: A depth‐dependent thermal history in the arc settings was decoded from chemical zonings in olivine and pyroxene of Ichinomegata xenolithsThe lithosphere beneath Ichinomegata experienced ∼14 million years of thickening and subsequent ∼12 thousand years of thinningThe duration of xenolith transportation by the host magma took 1–68 days and might suggest increasing ascent velocity at shallower depths
- Subjects
JAPAN; OLIVINE; INCLUSIONS in igneous rocks; PLATE tectonics; HEAT conduction; LITHOSPHERE; MINERAL analysis
- Publication
Journal of Geophysical Research. Solid Earth, 2023, Vol 128, Issue 10, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2023JB027208