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Petrology
 
 
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In geology
Geology

Geology is the science and study of the solid and liquid matter that constitute the Earth. The field of geology encompasses the study of the composition, structural geology, physical properties, dynamics, and History of the Earth of Earth materials, and the processes by which they are formed, moved, and changed....
, petrology (from Greek: p?t?a, petra, rock; and ?????, logos, knowledge) is the study of rock
Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
s, and the conditions in which they form. Lithology once was approximately synonymous with petrography
Petrography

Petrography is that branch of petrology which focuses on detailed descriptions of rock . Someone who studies petrography is called a petrographer....
, but in current usage, lithology is a subdivision of petrology focusing on macroscopic hand-sample or outcrop-scale description of rocks, while petrography is the speciality that deals with microscopic details.

In the oil industry, lithology, or more specifically mud logging
Mud logging

Mud logging, also known as hydrocarbon well logging, is a type of borehole logging performed by the mud logger, that provides well owners with information about the lithology and fluid content of the borehole....
, is the graphic representation of geological formations being drilled through, and drawn on a log called a mud log
Mud log

A Mud log is a graphical representation of the ROP , lithology, hydrocarbons and other drilling parameters generated while drilling an oil well....
.






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In geology
Geology

Geology is the science and study of the solid and liquid matter that constitute the Earth. The field of geology encompasses the study of the composition, structural geology, physical properties, dynamics, and History of the Earth of Earth materials, and the processes by which they are formed, moved, and changed....
, petrology (from Greek: p?t?a, petra, rock; and ?????, logos, knowledge) is the study of rock
Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
s, and the conditions in which they form. Lithology once was approximately synonymous with petrography
Petrography

Petrography is that branch of petrology which focuses on detailed descriptions of rock . Someone who studies petrography is called a petrographer....
, but in current usage, lithology is a subdivision of petrology focusing on macroscopic hand-sample or outcrop-scale description of rocks, while petrography is the speciality that deals with microscopic details.

In the oil industry, lithology, or more specifically mud logging
Mud logging

Mud logging, also known as hydrocarbon well logging, is a type of borehole logging performed by the mud logger, that provides well owners with information about the lithology and fluid content of the borehole....
, is the graphic representation of geological formations being drilled through, and drawn on a log called a mud log
Mud log

A Mud log is a graphical representation of the ROP , lithology, hydrocarbons and other drilling parameters generated while drilling an oil well....
. As the cuttings are circulated out of the borehole
Borehole

A borehole is the generalised term for any narrow Shaft mining drilled in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes including the extraction of water or other liquid or gases , as part of a geotechnical investigation or Phase I Environmental Site Assessment#Other types of ESA, fo...
 they are sampled, examined (typically under a 10x microscope) and tested chemically when needed.

Methodology

Petrology utilizes the classical fields of mineralogy
Mineralogy

Mineralogy is an Earth Science focused around the chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization....
, petrography
Petrography

Petrography is that branch of petrology which focuses on detailed descriptions of rock . Someone who studies petrography is called a petrographer....
, optical mineralogy
Optical mineralogy

Optical mineralogy is the study of minerals and Rock by measuring their optics properties. Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope....
, and chemical analyses to describe the composition and texture of rocks. Modern petrologists also include the principles of geochemistry
Geochemistry

The field of geochemistry involves study of the chemistry composition of the Earth and other planets, chemical processes and reactions that govern the composition of Rock s and soils, and the cycles of matter and energy that transport the Earth's chemical components in time and space, and their interaction with the hydrosphere and the atmosph...
 and geophysics
Geophysics

Geophysics, a major discipline of the Earth sciences, is the study of the Earth by the quantitative observation of its physical properties, especially by Seismology, Electromagnetism, Radioactive decay, galvanic and potential field methods....
 through the studies of geochemical trends and cycles and the use of thermodynamic data and experiments to better understand the origins of rocks.

Branches of petrology

There are three branches of petrology, corresponding to the three types of rocks: igneous, metamorphic, and sedimentary, and another dealing with experimental techniques:

  • Igneous petrology focuses on the composition and texture of igneous rock
    Igneous rock

    Igneous rock is one of the three main Rock types . Igneous rock is formed by magma being cooled and becoming solid . They may form with or without crystallization, either below the surface as Intrusion rocks or on the surface as extrusive rocks....
    s (rocks such as granite
    Granite

    Granite is a common and widely occurring type of Intrusion , felsic, igneous rock rock . Granite has a medium to coarse texture, occasionally with some individual crystals larger than the groundmass forming a rock known as Porphyry ....
     or basalt
    Basalt

    Basalt is a common extrusive volcanic rock. It is usually gray to black and fine-grained due to rapid cooling of lava at the surface of a planet....
     which have crystallized from molten rock or magma
    Magma

    Magma is molten Rock that is found beneath the surface of the Earth, and may also exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and gas bubbles....
    ). Igneous rocks include volcanic and plutonic
    Intrusion

    In geology, an intrusion is a body of igneous rock that has crystallized from molten magma below the surface of the Earth. Bodies of magma that solidify underground before they reach the surface of the earth are called plutons, named for Pluto , the Roman mythology of the underworld....
     rocks.
  • Sedimentary petrology focuses on the composition and texture of sedimentary rock
    Sedimentary rock

    Sedimentary rock is one of the three main Rock types . Sedimentary rock is formed by deposition and consolidation of mineral and organic material and from precipitation of minerals from solution....
    s (rocks such as sandstone
    Sandstone

    Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock Particle size . Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust ....
    , shale
    Shale

    Shale is a fine-grained sedimentary rock whose original constituents were clay minerals or muds. It is characterized by thin laminae breaking with an irregular curving fracture, often splintery and usually parallel to the often-indistinguishable bedding plane....
    , or limestone
    Limestone

    File:Limestone Formation In Waitomo.jpgLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geology record....
     which consist of pieces or particles derived from other rocks or biological or chemical deposits, and are usually bound together in a matrix
    Matrix (geology)

    The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or crystals are embedded.The matrix of an igneous rock consists of fine-grained, often microscopic, crystals in which larger crystals are embedded....
     of finer material).
  • Metamorphic petrology focuses on the composition and texture of metamorphic rock
    Metamorphic rock

    Metamorphic rock is the result of the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form"....
    s (rocks such as slate
    Slate

    Slate is a fine-grained, foliation , homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcano ash through low grade regional metamorphism....
    , marble
    Marble

    Marble is a nonfoliated metamorphic rock resulting from the metamorphism of limestone, composed mostly of calcite . It is extensively used for Marble sculpture, as a architecture material, and in many other applications....
    , gneiss
    Gneiss

    Gneiss is a common and widely distributed type of Rock formed by high-grade regional metamorphic rock processes from pre-existing formations that were originally either igneous rock or Sedimentary rock rocks....
    , or schist
    Schist

    The schists form a group of Erins metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, Chlorite group, talc, hornblende, graphite, and others....
     which started out as sedimentary or igneous rocks but which have undergone chemical, mineralogical or textural changes due to extremes of pressure, temperature or both)
  • Experimental petrology employs high-pressure, high-temperature apparatus to investigate the geochemistry and phase relations
    Phase (matter)

    In the physical sciences, a phase is a region of space , throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, refractive index, and chemical composition....
     of natural or synthetic materials at elevated pressures and temperatures. Experiments are particularly useful for investigating rocks of the lower crust
    Crust (geology)

    In geology, a crust is the outermost solid shell of a planet or moon, which is chemically distinct from the underlying mantle . Crusts of Earth , our Moon, Mercury , Venus, and Mars have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantle s....
     and upper mantle
    Mantle (geology)

    The mantle is a part of an astronomical object. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers....
     that rarely survive the journey to the surface in pristine condition. The work of experimental petrologists has laid a foundation on which modern understanding of igneous and metamorphic processes has been built.


Terminology


Acid test: Using acid to test rock or soil for carbonates. Suite: A collection of rock specimens from a given area, or it can refer to the succession of closely associated sedimentary strata or layers, especially a repeated sequence of layers.

See also



External links

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