
Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are
igneous
Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
The magma can be derived from partial ...
and
meta
Meta most commonly refers to:
* Meta (prefix), a common affix and word in English ( in Greek)
* Meta Platforms, an American multinational technology conglomerate (formerly ''Facebook, Inc.'')
Meta or META may also refer to:
Businesses
* Meta (ac ...
-igneous rocks with a very low
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...
content (less than 45%), generally >18%
MgO, high
FeO, low
potassium
Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
, and are usually composed of greater than 90%
mafic
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
s (dark colored, high
magnesium
Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...
and
iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
content).
Earth's mantle
Earth's mantle is a layer of silicate mineral, silicate rock between the Earth's crust, crust and the Earth's outer core, outer core. It has a mass of and makes up 67% of the mass of Earth. It has a thickness of making up about 46% of Earth's ...
is composed of ultramafic rocks. Ultrabasic is a more inclusive term that includes igneous rocks with low silica content that may not be extremely enriched in Fe and Mg, such as
carbonatite
Carbonatite () is a type of intrusive rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geoche ...
s and
ultrapotassic igneous rocks
Ultrapotassic igneous rocks are a class of rare, volumetrically minor, generally ultramafic or mafic silica-depleted igneous rocks.
While there are debates on the exact classifications of ultrapotassic rocks, they are defined by using the chemic ...
.
Intrusive ultramafic rocks
Intrusive ultramafic rocks are often found in large, layered
ultramafic intrusions where
differentiated rock types often occur in layers. Such
cumulate
Cumulate rocks are igneous rocks formed by the accumulation of crystals from a magma either by settling or floating. Cumulate rocks are named according to their texture; cumulate texture is diagnostic of the conditions of formation of this group ...
rock types do not represent the chemistry of the magma from which they crystallized. The ultramafic intrusives include the
dunite
Dunite (), also known as olivinite (not to be confused with the mineral olivenite), is an intrusive igneous rock of ultramafic composition and with phaneritic (coarse-grained) texture. The mineral assemblage is greater than 90% olivine, wit ...
s,
peridotite
Peridotite ( ) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high pr ...
s and
pyroxenite
Pyroxenite is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite, diopside, hypersthene, bronzite or enstatite. Pyroxenites are classified into clinopyroxenites, orthopyroxenites, and the w ...
s. Other rare varieties include
troctolite
Troctolite (from Greek τρώκτης 'trout' and λίθος 'stone') is a mafic intrusive rock type. It consists essentially of major but variable amounts of olivine and calcic plagioclase along with minor pyroxene. It is an olivine-rich ano ...
which has a greater percentage of calcic plagioclase. These grade into the
anorthosite
Anorthosite () is a phaneritic, intrusive rock, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic ...
s.
Gabbro
Gabbro ( ) is a phaneritic (coarse-grained and magnesium- and iron-rich), mafic intrusive igneous rock formed from the slow cooling magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is ch ...
and
norite
Norite is a mafic Intrusive rock, intrusive igneous rock composed largely of the calcium-rich plagioclase labradorite, orthopyroxene, and olivine. The name ''norite'' is derived from Norway, by its Norwegian name ''Norge''.
Norite, also known ...
often occur in the upper portions of the layered ultramafic sequences.
Hornblendite
Hornblendite is a plutonic rock consisting mainly of the amphibole hornblende. Hornblende-rich ultramafic rocks are rare and when hornblende is the dominant mineral phase they are classified as hornblendites with qualifiers such as garnet hornble ...
and, rarely
phlogopite
Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica.
Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg3AlSi3 ...
, are also found.
Volcanic ultramafic rocks on Earth
Volcanic
A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often fo ...
ultramafic rocks are rare outside of the
Archaean and are essentially restricted to the
Neoproterozoic
The Neoproterozoic Era is the last of the three geologic eras of the Proterozoic geologic eon, eon, spanning from 1 billion to 538.8 million years ago, and is the last era of the Precambrian "supereon". It is preceded by the Mesoproterozoic era an ...
or earlier.
Subvolcanic
A subvolcanic rock, also known as a hypabyssal rock, is an intrusive rock, intrusive igneous rock that is emplaced at depths less than within the crust (geology), crust, and has intermediate crystallite, grain size and often porphyritic texture be ...
ultramafic rocks and
dykes persist longer, but are also rare. There is evidence of ultramafic rocks elsewhere in the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
.
Examples include
komatiite
Komatiite is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava of at least 18 wt% magnesium oxide (MgO). It is classified as a 'picritic rock'. Komatiites have low silicon, potassium and aluminium, and ...
and
picritic basalt. Komatiites can be host to
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...
deposits of
nickel
Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...
.
Ultramafic tuff
Ultramafic
tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...
is extremely rare. It has a characteristic abundance of
olivine
The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...
or
serpentine and a scarcity or absence of
feldspar
Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...
and
quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...
. Rare occurrences may include unusual surface deposits of
maar
A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...
s of
kimberlite
Kimberlite is an igneous rock and a rare variant of peridotite. It is most commonly known as the main host matrix for diamonds. It is named after the town of Kimberley, Northern Cape, Kimberley in South Africa, where the discovery of an 83.5-Car ...
s in the
diamond
Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Diamond is tasteless, odourless, strong, brittle solid, colourless in pure form, a poor conductor of e ...
fields of southern Africa and other regions.
Ultrapotassic ultramafic rocks
Technically
ultrapotassic rocks
Ultrapotassic igneous rocks are a class of rare, volumetrically minor, generally ultramafic or mafic silica-depleted igneous rocks.
While there are debates on the exact classifications of ultrapotassic rocks, they are defined by using the chemica ...
and
melilitic rocks are considered a separate group, based on melting model criteria, but there are ultrapotassic and highly silica-under-saturated rocks with >18% MgO which can be considered "ultramafic".
Ultrapotassic, ultramafic igneous rocks such as
lamprophyre
Lamprophyres () are uncommon, small-volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks, and small intrusions. They are alkaline silica- undersaturated mafic or ultramafic rocks with high magnesium o ...
,
lamproite
Lamproite is an ultrapotassic mantle-derived volcanic or subvolcanic rock. It has low CaO, Al2O3, Na2O, high K2O/Al2O3, a relatively high MgO content and extreme enrichment in incompatible elements.
Lamproites are geographically widespre ...
and
kimberlite
Kimberlite is an igneous rock and a rare variant of peridotite. It is most commonly known as the main host matrix for diamonds. It is named after the town of Kimberley, Northern Cape, Kimberley in South Africa, where the discovery of an 83.5-Car ...
are known to have reached the surface of the Earth. Although no modern eruptions have been observed, analogues are preserved.
Most of these rocks occur as
dikes
Dyke or dike may refer to:
General uses
* Dyke (slang), a slang word meaning "lesbian"
* Dike (geology), formations of magma or sediment that cut through and across the layering of adjacent rocks
* Dike (mythology), ''Dikē'', the Greek goddess ...
,
diatreme
A diatreme, sometimes known as a maar-diatreme volcano, is a volcanic pipe associated with a gaseous explosion. When magma rises up through a crack in Earth's crust and makes contact with a shallow body of groundwater, rapid expansion of heated ...
s,
lopolith
A lopolith is a large igneous intrusion which is lenticular in shape with a depressed central region. Lopoliths are generally concordant with the intruded strata with dike or funnel-shaped feeder bodies below the body. The term was first defined ...
s or
laccolith
A laccolith is a body of intrusive rock with a dome-shaped upper surface and a level base, fed by a conduit from below. A laccolith forms when magma (molten rock) rising through the Earth's crust begins to spread out horizontally, prying apart ...
s, and very rarely, intrusions. Most kimberlite and lamproite occurrences occur as
volcanic
A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often fo ...
and subvolcanic diatremes and
maar
A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...
s; lavas are virtually unknown.
Vents of
Proterozoic
The Proterozoic ( ) is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, and is the longest eon of Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozo ...
lamproite (
Argyle diamond mine
The Argyle Diamond Mine was a diamond mine located in the East Kimberley region in the remote north of Western Australia. Argyle was at times the largest diamond producer in the world by volume (14 million carats in 2018), although the propo ...
), and
Cenozoic
The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...
lamproite (
Gaussberg
Gaussberg (or Schwarzen Berg, Mount Gauss) is an extinct, high volcanic cone in East Antarctica fronting on Davis Sea immediately west of Posadowsky Glacier (Antarctica), Posadowsky Glacier. It is ice-free and conical in nature, having formed s ...
,
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
) are known, as are vents of
Devonian
The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...
lamprophyre (
Scotland
Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...
). Kimberlite pipes in Canada, Russia and South Africa have incompletely preserved
tephra
Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism.
Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...
and
agglomerate
Agglomerate (from the Latin ''agglomerare'' meaning "to form into a ball") is a coarse accumulation of large blocks of volcanic material that contains at least 75% bombs. Volcanic bombs differ from volcanic blocks in that their shape records flui ...
facies
In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...
.
These are generally
diatreme
A diatreme, sometimes known as a maar-diatreme volcano, is a volcanic pipe associated with a gaseous explosion. When magma rises up through a crack in Earth's crust and makes contact with a shallow body of groundwater, rapid expansion of heated ...
events and as such are not lava flows although tephra and
ash deposits are partially preserved. These represent low-
volume
Volume is a measure of regions in three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch) ...
volatile melts and attain their ultramafic
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
via a different process than typical ultramafic rocks.
Metamorphic ultramafic rocks
Metamorphism
Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...
of ultramafic rocks in the presence of
water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
and/or
carbon dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
results in two main classes of metamorphic ultramafic rock;
talc carbonate
Talc carbonates are a suite of rock and mineral compositions found in metamorphosed ultramafic rocks.
The term refers to the two most common end-member minerals found within ultramafic rocks which have undergone talc-carbonation or carbonation rea ...
and
serpentinite
Serpentinite is a metamorphic rock composed predominantly of serpentine group minerals formed by serpentinization of mafic or ultramafic rocks. The ancient origin of the name is uncertain; it may be from the similarity of its texture or color ...
.
Talc carbonation reactions occur in ultramafic rocks at lower
greenschist
Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically and 2–10 kilobars (). Greenschists commonly have an abundance of green minerals such as Chlorite ...
through to
granulite
Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated ...
facies metamorphism when the rock in question is subjected to metamorphism and the metamorphic fluid has more than 10% molar proportion of CO
2 (
carbon dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
).
When such metamorphic fluids have less than 10% molar proportion of CO
2, reactions favor serpentinisation, resulting in
chlorite
The chlorite ion, or chlorine dioxide anion, is the halite (oxyanion), halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as s ...
-
serpentine-
amphibole
Amphibole ( ) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...
type assemblages.
Distribution in space and time
The majority of ultramafic rocks are exposed in
orogenic
Orogeny () is a mountain-building process that takes place at a convergent plate margin when plate motion compresses the margin. An or develops as the compressed plate crumples and is uplifted to form one or more mountain ranges. This involv ...
belts, and predominate in
Archaean and
Proterozoic
The Proterozoic ( ) is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, and is the longest eon of Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozo ...
terranes. Ultramafic magmas in the
Phanerozoic
The Phanerozoic is the current and the latest of the four eon (geology), geologic eons in the Earth's geologic time scale, covering the time period from 538.8 million years ago to the present. It is the eon during which abundant animal and ...
are rarer, and there are very few recognised true ultramafic lavas in the Phanerozoic.
Many surface exposures of ultramafic rocks occur in
ophiolite
An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle (Earth), upper mantle that has been uplifted and exposed, and often emplaced onto continental crustal rocks.
The Greek word ὄφις, ''ophis'' (''snake'') is ...
complexes where deep mantle-derived rocks have been
obducted onto
continental crust
Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...
along and above
subduction
Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...
zones.
Soil, regolith, and biology
Serpentine soil
Serpentine soil is an uncommon soil type produced by weathered ultramafic rock such as peridotite and its metamorphic derivatives such as serpentinite. More precisely, serpentine soil contains minerals of the serpentine subgroup, especially an ...
is a magnesium rich, calcium, potassium and phosphorus poor soil that develops on the
regolith
Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestria ...
derived from ultramafic rocks. Ultramafic rocks also contain elevated amounts of chromium and nickel which may be toxic to plants. As a result, a distinctive type of
vegetation
Vegetation is an assemblage of plants and the ground cover they provide. It is a general term, without specific reference to particular Taxon, taxa, life forms, structure, Spatial ecology, spatial extent, or any other specific Botany, botanic ...
develops on these soils. Examples are the ultramafic
woodland
A woodland () is, in the broad sense, land covered with woody plants (trees and shrubs), or in a narrow sense, synonymous with wood (or in the U.S., the '' plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunli ...
s and barrens of the
Appalachian Mountains
The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...
and
piedmont
Piedmont ( ; ; ) is one of the 20 regions of Italy, located in the northwest Italy, Northwest of the country. It borders the Liguria region to the south, the Lombardy and Emilia-Romagna regions to the east, and the Aosta Valley region to the ...
, the "wet
maquis" of the
New Caledonia rain forests
The New Caledonia rain forests are a terrestrial ecoregion, located in New Caledonia in the South Pacific. It is a tropical moist broadleaf forest ecoregion, part of the Australasian realm.
Setting
The ecoregion covers the windward eastern s ...
, and the ultramafic
forest
A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...
s of
Mount Kinabalu
Mount Kinabalu ( Dusun: ''Gayo Ngaran'' or ''Nulu Nabalu'', ) is the highest mountain in Malaysia and Borneo. With a height of , it is the third-highest peak of an island on Earth, the 28th highest peak in Southeast Asia, and 20th most prom ...
and other peaks in
Sabah
Sabah () is a States and federal territories of Malaysia, state of Malaysia located in northern Borneo, in the region of East Malaysia. Sabah has land borders with the Malaysian state of Sarawak to the southwest and Indonesia's North Kalima ...
,
Malaysia
Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...
. Vegetation is typically stunted, and sometimes includes
endemic
Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
species adapted to the soils.
Often thick,
magnesite
Magnesite is a mineral with the chemical formula ( magnesium carbonate). Iron, manganese, cobalt, and nickel may occur as admixtures, but only in small amounts.
Occurrence
Magnesite occurs as veins in and an alteration product of ultramafic r ...
-
calcrete
Caliche () is a soil accumulation of soluble calcium carbonate at depth, where it precipitates and binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or s ...
caprock Caprock or cap rock is a hard, resistant, and impermeable layer of rock that overlies and protects a reservoir of softer organic material, similar to the crust on a pie where the crust (caprock) prevents leakage of the soft filling (softer materia ...
,
laterite
Laterite is a soil type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by intensive and prolo ...
and
duricrust
Duricrust is a hard layer on or near the surface of soil. Duricrusts can range in thickness from a few millimeters or centimeters to several meters.
It is a general term (not to be confused with duripan) for a zone of chemical precipitation and ...
forms over ultramafic rocks in
tropical
The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...
and
subtropical
The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...
environments. Particular
floral
Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants (Flowering plant, angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls in ...
assemblages associated with highly nickeliferous ultramafic rocks are indicative tools for
mineral exploration
Mining engineering is the extraction of minerals from the ground. It is associated with many other disciplines, such as mineral processing, exploration, excavation, geology, metallurgy, geotechnical engineering and surveying. A mining engineer m ...
.
Weathered ultramafic rocks may form
lateritic nickel ore deposits Lateritic nickel ore deposits are surficial, weathered rinds formed on ultramafic rocks.
They account for 80% of the continental world nickel resources and will be in the future the dominant source for the mining of nickel.
Genesis and types of ni ...
.
Lichen
A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
communities on ultramafic rocks show distinctive characteristics, including the unusual co-presence of species that typically grow on either
acidic
An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen cation, H+), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid.
The first category of acids are the ...
or calcium-rich rocks, due to the rocks' unique chemical composition. While some lichen species appear to be characteristic of ultramafic environments within specific geographical regions, very few species are found exclusively on these rocks. Studies have shown that lichen communities on ultramafic rocks can be more diverse than those on adjacent mafic rocks, with some localities showing notably higher species counts on serpentinites compared to other rock types. These communities often display
xerophytic
A xerophyte () is a species of plant that has adaptations to survive in an environment with little liquid water. Examples of xerophytes include cactus, cacti, pineapple and some gymnosperm plants. The morphology (biology), morphology and physiology ...
characteristics and may include species with
disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but considerably separated from each other geographically. The causes are varied and might demonstrate either the expansion or contraction of a s ...
patterns. The weathering action of lichens on ultramafic rocks can promote
biogeochemical
Biogeochemistry is the scientific discipline that involves the study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment (including the biosphere, the cryosphere, ...
processes, including the complete depletion of magnesium from serpentine minerals beneath lichen
thalli
Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...
and the formation of
secondary mineral A primary mineral is any mineral formed during the original crystallization of the host Igneous rock, igneous Primary Rock, primary rock and includes the essential mineral(s) used to classify the rock along with any accessory minerals. In ore deposi ...
s common in serpentine soils.
Other celestial bodies
Io
Ultramafic lava may have been detected on
Io, a moon of
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
, because
heat-mapping of Io's surface found ultra-hot areas with temperatures in excess of . The
magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...
immediately below these hot spots is probably about hotter, based on surface-to-subsurface temperature differences observed for lava on Earth. A temperature of is thought to indicate the presence of ultramafic magma.
Mercury
Mercury appears to have ultramafic volcanic rock.
Mars
The undifferentiated crust of
Mars
Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
is largely composed of
mafic
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...
and ultramafic rocks. Dark lobate flows of upper
Hesperian
The Hesperian is a system (stratigraphy), geologic system and geologic timescale, time period on the planet Mars characterized by widespread Volcanology of Mars, volcanic activity and catastrophic flooding that carved immense outflow channels acr ...
and early
Amazonian age, probably extruded from a regional network of extension faults, can be traced in the Ladon Basin. Spectral analysis data confirm the ultramafic character of these flows and the underlying rocks.
Trappist-1 b
Mid-infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those of ...
(12.8 μm) observations have shown that the
exoplanet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...
's measured flux is consistent with a surface model of ultramafic rocks.
See also
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Chromitite
Chromitite is an igneous cumulate rock composed mostly of the mineral chromite. It is found in layered intrusions such as the Bushveld Igneous Complex in South Africa, the Stillwater igneous complex in Montana and the Ring of Fire discovery in ...
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Magnetite
Magnetite is a mineral and one of the main iron ores, with the chemical formula . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...
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Kambalda type komatiitic nickel ore deposits
Kambalda type komatiitic nickel ore deposits are a class of magmatic iron-nickel-copper-platinum-group element ore deposit in which the physical processes of komatiite volcanology serve to deposit, concentrate and enrich a Fe-Ni-Cu-(PGE) sulfide ...
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Fractional crystallization (geology)
Fractional crystallization, or crystal fractionation, is one of the most important geochemical and physical processes operating within crust and mantle of a rocky planetary body, such as the Earth. It is important in the formation of igneous ro ...
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Volcanism on Io
Io (moon), Io, a Moons of Jupiter, moon of Jupiter, has a substantial presence of volcanoes, patera (planetary nomenclature), volcanic pits and lava flows on its surface. Volcanic activity on the moon was first discovered in 1979 by Linda Morabi ...
, a moon of Jupiter
References
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Metamorphic rocks