page_title: Cleavage (geology)
section_title: Spaced cleavage
hierarchical_section_title: Cleavage (geology) / Types of cleavage / Spaced cleavage
caption_attribution_description: English: A thin section depicting spaced cleavage. The cleavage domains are darker biotite grains, and the microlithons between consist of mostly muscovite and quartz. The grains in the microlithons are starting to align in a preferred orientation. A new foliation overprinted an old, showing the beginning signs of a crenulation cleavage.
context_page_description: Cleavage, in structural geology and petrology, describes a type of planar rock feature that develops as a result of deformation and metamorphism. The degree of deformation and metamorphism along with rock type determines the kind of cleavage feature that develops. Generally these structures are formed in fine grained rocks composed of minerals affected by pressure solution.
  Cleavage is a type of rock foliation, a fabric element that describes the way planar features develop in a rock. Foliation is separated into two groups: primary and secondary. Primary deals with igneous and sedimentary rocks while secondary deals with rocks that undergo metamorphism as a result of deformation. Cleavage is a type of secondary foliation associated with fine grained rocks. For coarser grained rocks, schistosity is used to describe secondary foliation.
  There is a variety of definitions for cleavage which may cause confusion and debate. The terminology used in this article is based largely on Passchier and Trouw. They state that cleavage is a type of secondary foliation in fine grained rocks characterized by planar fabric elements that form in a preferred orientation.
context_section_description: Spaced Cleavage occurs in rocks with minerals that are not evenly distributed and as a result the rock forms discontinuous layers or lenses of different types of minerals. Spaced cleavage contains two types of domains; cleavage domains and microlithons. Cleavage domains are planar boundaries subparallel to the trend of the domain, and microlithons are bounded by the cleavage domains. Spaced cleavages can be categorized based on whether the grains inside the microlithons are randomly oriented or contain microfolds from a previous foliation fabric. Other descriptions for spaced cleavages include the spacing size, the shape and percentage of cleavage domains, and the transition between cleavage domains and microlithons.
caption: A thin section depicting spaced cleavage. The cleavage domains are darker biotite grains, and the microlithons between consist of mostly muscovite and quartz. The grains in the microlithons are starting to align in a preferred orientation. A new foliation overprinted an old, showing the beginning signs of a crenulation cleavage.
exif: {}