The solubility of potassium-feldspar in calcic plagioclase : experimental study and application to natural occurrences ...

• Main Author: Ai, Y
• Format: Thesis
• Language: unknown
• Published: University Of Tasmania 2023
• Subjects: Departure Rocks; Antarc*; Antarctica
• Online Access: https://dx.doi.org/10.25959/23235878.v1; https://figshare.utas.edu.au/articles/thesis/The_solubility_of_potassium-feldspar_in_calcic_plagioclase_experimental_study_and_application_to_natural_occurrences/23235878/1

Unusual feldspar intergrowths were found in two metamorphosed basalt dykes from Departure Rocks, Antarctica. They are composed of host calcic plagioclase (Kf 0 _3 An7 5_9 1 Ab9_25) and potassium-rich alkali feldspar (Kf90 _96 Ano_5 Ab0_8) lamellae. Their bulk composition is estimated to be Kf An 21 65 Ab14. The complex and yet regular lamella textures of these intergrowths suggest that they are exsolution products. This requires the existence of a formerly homogeneous plagioclase, compositionally equivalent to the estimated bulk composition of these intergrowths. Experimental studies in the binary system anorthite K-feldspar and in the albite-poor ternery feldspar system have proven the existence of such homogeneous plagioclase, which has been synthesized at 1150°C and 10 [(bar under dry conditions. The unusual feldspar intergrowths were homogenized under these same conditions, further supporting the hypothesized exsolution origin of these intergrowths. In an experiment of plagioclase crystallization in ...