Abstract
Feldspar grain-size reduction occurred due to the fracturing of plagioclase and K-feldspar, myrmekite formation and neocrystallization of albitic plagioclase along shear fractures of K-feldspar porphyroclasts in the leucocratic granitic rocks from the Yecheon shear zone of South Korea that was deformed under a middle greenschist-facies condition. The neocrystallization of albitic plagioclase was induced by strain energy adjacent to the shear fractures and by chemical free energy due to the compositional disequilibrium between infiltrating Na-rich fluid and host K-feldspar. With increasing deformation from protomylonite to mylonite, alternating layers of feldspar, quartz and muscovite developed. The fine-grained feldspar-rich layers were deformed dominantly by granular flow, while quartz ribbons were deformed by dislocation creep. With layer development and a more distributed strain in the mylonite, lower stresses in the quartz-rich layers resulted in a larger size of dynamically recrystallized quartz grains than that of the protomylonite.
| Original language | English |
|---|---|
| Pages (from-to) | 227-237 |
| Number of pages | 11 |
| Journal | Tectonophysics |
| Volume | 407 |
| Issue number | 3-4 |
| DOIs | |
| Publication status | Published - 2005 Oct 7 |
Bibliographical note
Funding Information:We thank W.M. Lamb and J. Newman for discussions on feldspar microstructures, and R. Guillemette and S. Choi for initial electron microprobe analyses on our samples. We appreciate thorough and constructive reviews by K. Kanagawa, an anonymous referee and J.-P. Burg which improved the paper significantly. This research was supported by KOSEF grant R02-2003-000-10039-0 to JHR.
Keywords
- Dynamic recrystallization
- Grain-size reduction
- Granitic mylonite
- Granular flow
- Yecheon shear zone
ASJC Scopus subject areas
- Geophysics
- Earth-Surface Processes