Textures of syntaxial quartz veins synthesized by hydrothermal experiments

Atsushi Okamoto, Kotaro Sekine

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Syntaxial quartz veins were synthesized by hydrothermal flow-through experiments using rock blocks (metachert, sandstone, and granite) containing slits. Based on analyses of vein textures using birefringence imaging microscopy, we identified two stages of crystal growth. During stage 1, quartz grain growth occurs without an increase in grain width. During stage 2, quartz grains develop facets and grow preferentially parallel to the c-axis orientation, and the aspect ratio of quartz grains shifts toward ∼2.9. Competitive growth occurs significantly at stage 2, and the transition from stage 1-2 occurs at a critical distance from the vein wall, being approximately equal to the host-rock grain size. Crystal growth in the slits produce various textures controlled by the ratio of slit aperture (H) to host-rock grain size (d). In high H/d cracks, elongate-blocky texture develops by grain impingement during stage 2, whereas in low H/d cracks, crystals that bridge the crack form without competitive growth by grain impingement at stage 1. Heterogeneous structures of fracture porosity are produced during syntaxial vein formation, due to the anisotropy in the growth rate of quartz. Such "incompletely sealed" cracks may act as important fluid pathways and as weak planes in the upper crust.

Original languageEnglish
Pages (from-to)1764-1775
Number of pages12
JournalJournal of Structural Geology
Volume33
Issue number12
DOIs
Publication statusPublished - 2011 Dec 1

Keywords

  • Competitive growth
  • Hydrothermal experiments
  • Quartz vein
  • Vein texture

ASJC Scopus subject areas

  • Geology

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