Geodynamics & Tectonophysics· 2026Q2
GEOCHRONOLOGY (U-Pb, Ar-Ar), ISOTOPIC AND GEOCHEMICAL CHARACTERISTICS OF THE AKIT ALKALINE INTRUSION (NORTHERN BAIKAL ALKALINE PROVINCE): THE MESOZOIC MAGMATIC STAGE AND ITS GEODYNAMIC IMPLICATIONS
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- 2026year
Short summary
The Akit alkaline intrusion crystallized between 185-180 Ma (U-Pb zircon dating) and its K-Ar systems closed by 176-169 Ma, confirming a Mesozoic magmatic stage in the Northern Baikal region.
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Key points
- Akit alkaline intrusion crystallized between 185-180 Ma (U-Pb zircon dating).
- K-Ar isotopic systems in silicate minerals closed between 176-169 Ma.
- Confirms a Mesozoic stage of alkaline magmatism in the Northern Baikal region.
- Nepheline/alkaline syenites derived from mantle-crustal sources (εNd(T)=+0.06…+1.45).
- Quartz syenites (nordmarkites) derived from a distinct source isotopically similar to host granites (εNd(T)=–12.07).
AI-generated from the title and abstract; the full text is not read.
Abstract
The results of a geochronological (U-Pb LA-SF-ICP-MS, 40 Ar/ 39 Ar) and isotopic (Sr, Nd, O) study of the Akit alkaline intrusion are presented in the paper. U-Pb dating of zircons established the crystallization age of the nepheline syenites at 185–180 Ma, while 40 Ar/ 39 Ar dating of silicate minerals (biotite, tainiolite, nepheline) recorded the closure of K-Ar isotopic systems in the 176–169 Ma range. The established Mesozoic age of the Akit intrusion distinguishes it from Paleozoic alkaline intrusions (Synnyr and Burpala) and confirms the existence of a Mesozoic stage of alkaline magmatism in the Northern Baikal region. Isotopic data reveal a contrast in melt sources: nepheline and alkaline syenites exhibit mantle-crustal characteristics (εNd(T)=+0.06…+1.45), whereas quartz syenites (nordmarkites) display distinct values (εNd(T)=–12.07), showing isotopic affinity with the host granites.
The authors' abstract, as published at the source. Geodynamics & Tectonophysics, 2026 · DOI ↗
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