Ca. 1.89 Ga orthogneisses underlying the varena iron ore deposit in SE Lithuania, East European Craton – Implications for fluid evolution and Cl remobilization
(2026) In Precambrian Research 439.- Abstract
Scapolite-bearing orthogneisses underlying the Proterozoic Varena Iron Ore Deposit, eastern Lithuania, the western East European Craton, represent the development of a sodic alteration zone. Scapolite chemistry records fluid salinity increase with temperature, reaching its maximum at temperatures of ∼750 °C. Fluid-mineral reactions controlled the fluid KCl/NaCl ratio, enabling partial melting at peak temperatures, evident by the dark cathodoluminescence metamorphic zircon rims, felsic domain segregation and anhydrous mineral assemblage in the mafic domains. Partitioning of water from the fluid into the partial melt may have played a crucial role in Cl-rich fluid development, capable of mobilizing a substantial amount of iron and rare... (More)
Scapolite-bearing orthogneisses underlying the Proterozoic Varena Iron Ore Deposit, eastern Lithuania, the western East European Craton, represent the development of a sodic alteration zone. Scapolite chemistry records fluid salinity increase with temperature, reaching its maximum at temperatures of ∼750 °C. Fluid-mineral reactions controlled the fluid KCl/NaCl ratio, enabling partial melting at peak temperatures, evident by the dark cathodoluminescence metamorphic zircon rims, felsic domain segregation and anhydrous mineral assemblage in the mafic domains. Partitioning of water from the fluid into the partial melt may have played a crucial role in Cl-rich fluid development, capable of mobilizing a substantial amount of iron and rare earth elements. Oscillatory zoned zircons record the emplacement age of the orthogneiss precursor at ca. 1.89 Ga, while the ca. 1.75–1.79 Ga metamorphic rims are coeval with the mafic dyke emplacement further west, which marks a change from a compressive to tensile tectonic regime. Furthermore, the 1.75–1.79 Ga metamorphism coincides with rifting and dike emplacement along the Columbia supercontinent margins. A reheating event recorded at ca. 1.49–1.52 Ga in titanite and altered zircon grains has remobilized chlorine and initiated albitization at temperatures of ∼660°C. It is semi-simultaneous with the vein-type granite emplacement in the region and widespread anorogenic magmatism throughout the Baltica. While its effect on economically significant ore formation is unclear, iron mobilization on a microscopic scale is evident by the iron and Cl-rich chloro-potassic hastingsite nucleation. Our results show that scapolite in different instances can act as a sink and source of Cl in the fluid.
(Less)
- author
- Siliauskas, Laurynas ; Gumsley, Ashley ; Skridlaite, Grazina ; Whitehouse, Martin J. ; Næraa, Tomas LU ; Ene, Vlad Victor and Birmanaitė, Ugnė
- organization
- publishing date
- 2026-07-01
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Precambrian Research
- volume
- 439
- article number
- 108093
- publisher
- Elsevier
- external identifiers
-
- scopus:105034798082
- ISSN
- 0301-9268
- DOI
- 10.1016/j.precamres.2026.108093
- language
- English
- LU publication?
- yes
- id
- ca62b9ea-7dfb-4101-be96-e241958fa324
- date added to LUP
- 2026-06-08 16:11:18
- date last changed
- 2026-06-08 16:12:05
@article{ca62b9ea-7dfb-4101-be96-e241958fa324,
abstract = {{<p>Scapolite-bearing orthogneisses underlying the Proterozoic Varena Iron Ore Deposit, eastern Lithuania, the western East European Craton, represent the development of a sodic alteration zone. Scapolite chemistry records fluid salinity increase with temperature, reaching its maximum at temperatures of ∼750 °C. Fluid-mineral reactions controlled the fluid KCl/NaCl ratio, enabling partial melting at peak temperatures, evident by the dark cathodoluminescence metamorphic zircon rims, felsic domain segregation and anhydrous mineral assemblage in the mafic domains. Partitioning of water from the fluid into the partial melt may have played a crucial role in Cl-rich fluid development, capable of mobilizing a substantial amount of iron and rare earth elements. Oscillatory zoned zircons record the emplacement age of the orthogneiss precursor at ca. 1.89 Ga, while the ca. 1.75–1.79 Ga metamorphic rims are coeval with the mafic dyke emplacement further west, which marks a change from a compressive to tensile tectonic regime. Furthermore, the 1.75–1.79 Ga metamorphism coincides with rifting and dike emplacement along the Columbia supercontinent margins. A reheating event recorded at ca. 1.49–1.52 Ga in titanite and altered zircon grains has remobilized chlorine and initiated albitization at temperatures of ∼660°C. It is semi-simultaneous with the vein-type granite emplacement in the region and widespread anorogenic magmatism throughout the Baltica. While its effect on economically significant ore formation is unclear, iron mobilization on a microscopic scale is evident by the iron and Cl-rich chloro-potassic hastingsite nucleation. Our results show that scapolite in different instances can act as a sink and source of Cl in the fluid.</p>}},
author = {{Siliauskas, Laurynas and Gumsley, Ashley and Skridlaite, Grazina and Whitehouse, Martin J. and Næraa, Tomas and Ene, Vlad Victor and Birmanaitė, Ugnė}},
issn = {{0301-9268}},
language = {{eng}},
month = {{07}},
publisher = {{Elsevier}},
series = {{Precambrian Research}},
title = {{Ca. 1.89 Ga orthogneisses underlying the varena iron ore deposit in SE Lithuania, East European Craton – Implications for fluid evolution and Cl remobilization}},
url = {{http://dx.doi.org/10.1016/j.precamres.2026.108093}},
doi = {{10.1016/j.precamres.2026.108093}},
volume = {{439}},
year = {{2026}},
}