K isotopic fractionation in K-feldspar: Effects of mineral chemistry

Shanke Liu, Wenjun Li, Benxun Su, Qiqi Pan, Meng Yuan, Patrick Asamoah Sakyi

Research output: Contribution to journalArticlepeer-review

Abstract

Controlling factors of potassium (K) isotopic fractionation in K-feldspar remain poorly constrained. In this study, we analyzed the K isotopic compositions of 11 K-feldspar samples from diverse lithological compositions. The degree of Al/Si order ranged from 0.22 to 0.94 (1.0 = completely ordered). Analyzed samples are mixtures of K-feldspar (>70 wt%) and coexisting albite. The relative contribution of K2O from the K-feldspar phase of the sample was over 98%, indicating that the K isotopic composition (δ41K) derives mainly from K-feldspar and hence reflects its behavior. The δ41K values of these samples range from -0.710 to -0.075‰, which are slightly correlated with the degree of Al/Si order. The correlations of δ41K with SiO2 and Al2O3 contents and the corresponding Al/Si mole ratios reveal that Al and Si play a significant role in the K isotopic behavior of K-feldspar. The correlations of δ41K with SiO2 and Al2O3 contents are attributed to the difference in K-O bond strengths. Compared to K-feldspar, the K content could be a better proxy for constraining the δ41K of plagioclase. Our results demonstrate that the δ41K of K-feldspar is dependent on its mineral chemistry, and its K isotopic composition may be insensitive to other factors, such as the source heterogeneity. The inference is further confirmed by comparing the δ41K values in this study with published δ41K values of K-feldspar from different sources.

Original languageEnglish
Pages (from-to)1523-1534
Number of pages12
JournalAmerican Mineralogist
Volume109
Issue number9
DOIs
Publication statusPublished - 1 Sep 2024

Keywords

  • Al/Si mole ratio
  • Al/Si order
  • K isotopes
  • K-feldspar
  • bond length

Fingerprint

Dive into the research topics of 'K isotopic fractionation in K-feldspar: Effects of mineral chemistry'. Together they form a unique fingerprint.

Cite this