Page 361 - Geology and Geochemistry of Oil and Gas

322 APPENDIX C

pure quartz or calcite end-member composition,
respectively.
Maturity In reference to maturation above.
Mean square error (MSE) The expression of the square of the difference between
an estimate of a parameter and its true value, taken
with respect to the sampling distribution of the
estimate.
Meniscus [lith] The hour-glass shape of interparticle cements
precipitated from fluids held by attraction at grain-to-
grain contacts; usually indicative of cement
precipitation in the vadose environment.
Meniscus [petr] The curved upper surface of a liquid column, concave
when the containing walls are wet by the liquid
(negative meniscus) and convex when they are not
(positive meniscus).
Mesh A measure of fineness of a screen or sieve; e.g., a 200-
mesh sieve has 200 openings per linear inch through
which a particle of 74 mm can pass.
Mesogenetic Diagenetic changes in rocks occurring in the deep
burial environment. Syn: Catagenetic, Epigenetic.
Metamorphic rock A rock derived from preexisting rocks by
mineralogical, chemical, and structural alterations
caused by processes within the Earth’s crust.
Metastable Said of minerals that are unstable at certain
temperatures and pressures, or in fluids of certain
composition. Partial syn: Unstable.
Meteoric Water derived ultimately from rain; water of recent
atmospheric origin.
Methane A colorless odorless inflammable gas; the simplest
paraffin hydrocarbon, formula CH 4 . It is the
principal constituent of natural gas and is also found
associated with crude oil.
Mica A silicate mineral characterized by sheet cleavage, i.e.,
it separates in thin sheets. There are two major types
of micas: biotite, a ferromagnesian black mica, and
muscovite, a potassic white mica.
Micrite Particulate, fine-grained matrix of carbonate rocks,
by various definitions, the particles being less than
20 mm or 4 mm in size; a carbonate rock textural type
composed dominantly of mud. Syn: Carbonate
mudstone.
Micritization Organic or inorganic process of converting
preexisting carbonate cements or grains to micrite.
Microbial Pertaining to the presence, activities, or products of
microbes such as algae, bacteria, fungi, and yeasts.