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The Gazzi-Dickinson method is a point-counting technique used in geology to statistically measure the components of a sedimentary rock, chiefly sandstone. The main focus (and most controversial) part of the technique is counting all sand-sized components as separate grains , regardless of what they are connected to.
A facies encompasses all the characteristics of a rock including its chemical, physical, and biological features that distinguish it from adjacent rock. [ 2 ] The term "facies" was introduced by the Swiss geologist Amanz Gressly in 1838 and was part of his significant contribution to the foundations of modern stratigraphy , [ 3 ] which replaced ...
Igneous rock, with gray groundmass and white phenocrysts marked. Orthoclase phenocrysts within a finer-grained matrix of a granite porphyry. The matrix or groundmass of a rock is the finer-grained mass of material in which larger grains, crystals, or clasts are embedded.
The composition of igneous rocks and minerals can be determined via a variety of methods of varying ease, cost, and complexity. The simplest method is observation of hand samples with the naked eye and/or with a hand lens. This can be used to gauge the general mineralogical composition of the rock, which gives an insight into the composition.
Normative mineralogy is an estimate of the mineralogy of the rock. It usually differs from the visually observable mineralogy, at least as much as the types of mineral species, especially amongst the ferromagnesian minerals and feldspars, where it is possible to have many solid solution series of minerals, or minerals with similar Fe and Mg ratios substituting, especially with water (e.g ...
Lithic fragments can be derived from sedimentary, igneous or metamorphic rocks. A lithic fragment is defined using the Gazzi-Dickinson point-counting method and being in the sand-size fraction. Sand grains in sedimentary rocks that are fragments of larger rocks that are not identified using the Gazzi-Dickinson method are usually called rock ...
There are two geochemical methods in determining the bulk-rock composition: X-ray fluorescence (XRF) analysis, which directly determines the whole rock chemical composition. [25] Point-counting composition using an electron microprobe, which involves weighted calculation of minerals in rocks observed from thin-sections. [25]
5) The rock planes are determined by color-coding or statistical method for evaluating whether the points are grouped to form a single or different planes. [ 8 ] [ 27 ] 6) Output the structural orientations data into suitable computer software files, and plotting the distribution of dip and dip directions of different planes on a stereonet .