TY  - JOUR
A1  - Franz, Gerhard
A1  - Sudo, Masafumi
A1  - Khomenko, Vladimir
T1  - 40Ar/39Ar dating of a hydrothermal pegmatitic buddingtonite–muscovite assemblage from Volyn, Ukraine
T2  - European journal of mineralogy : EJM : an international journal on mineralogy, petrology, geochemistry, and related sciences
N2  - We determined Ar-40/Ar-39 ages of buddingtonite, occurring together with muscovite, with the laser-ablation method. This is the first attempt to date the NH4-feldspar buddingtonite, which is typical for sedimentary-diagenetic environments of sediments, rich in organic matter, or in hydrothermal environments, associated with volcanic geyser systems. The sample is a hydrothermal breccia, coming from the Paleoproterozoic pegmatite field of the Korosten Plutonic Complex, Volyn, Ukraine. A detailed characterization by optical methods, electron microprobe analyses, backscattered electron imaging, and IR analyses showed that the buddingtonite consists of euhedral-appearing platy crystals of tens of micrometers wide, 100 or more micrometers in length, which consist of fine-grained fibers of <= 1 mu m thickness. The crystals are sector and growth zoned in terms of K-NH4-H3O content. The content of K allows for an age determination with the Ar-40/Ar-39 method, as well as in the accompanying muscovite, intimately intergrown with the buddingtonite. The determinations on muscovite yielded an age of 1491 +/- 9 Ma, interpreted as the hydrothermal event forming the breccia. However, buddingtonite apparent ages yielded a range of 563 +/- 14 Ma down to 383 +/- 12 Ma, which are interpreted as reset ages due to Ar loss of the fibrous buddingtonite crystals during later heating. We conclude that buddingtonite is suited for Ar-40/Ar-39 age determinations as a supplementary method, together with other methods and minerals; however, it requires a detailed mineralogical characterization, and the ages will likely represent minimum ages.
Y1  - 2022
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/62692
SN  - 0935-1221
SN  - 1617-4011
VL  - 34
IS  - 1
SP  - 7
EP  - 18
PB  - Copernicus
CY  - Göttingen
ER  -