[permalink] [id link]
In the olivine structure, the main olivine series of ( Mg, Fe )< sub > 2 </ sub > SiO < sub > 4 </ sub > consist of magnesium-rich forsterite and iron-rich fayalite.
from
Wikipedia
Some Related Sentences
olivine and structure
A possible mechanism for the generation of deep-focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure.
Olivine gives its name to the group of minerals with a related structure ( the olivine group ) which includes tephroite ( Mn < sub > 2 </ sub > SiO < sub > 4 </ sub >), monticellite ( CaMgSiO < sub > 4 </ sub >) and kirschsteinite ( CaFeSiO < sub > 4 </ sub >).
Figure 1: The atomic scale structure of olivine looking along the a axis.
At the high temperatures and pressures found at depth within the Earth the olivine structure is no longer stable.
Below depths of about olivine undergoes an exothermic phase transition to the sorosilicate, wadsleyite and, at about depth, wadsleyite transforms exothermically into ringwoodite, which has the spinel structure.
As pressure increases, the O < sup > 2 −</ sup > ions compress so olivine transforms to the spinel structure, which at still higher pressure converts to a perovskite structure and a coexisting periclase structure.
Between about 400 km and 650 km depth, olivine is not stable and is replaced by high pressure polymorphs with approximately the same composition: one polymorph is wadsleyite ( also called beta-spinel type ), and the other is ringwoodite ( a mineral with the gamma-spinel structure ).
In some meteorites, together with olivine it forms the bulk of the material ; it can occur in small spherical masses, or chondrules, with an internal radiated structure.
olivine and main
This main group Pallasite has some areas free of olivine crystals, and may have formed near the junction of the core and the mantle of an asteroid.
olivine and series
The ' Staffa Group ' is the name given to the series of olivine tholeiite basalts found in the vicinity of Mull which erupted 55 – 58 million years ago.
Hallival and Askival are formed from an extraordinary series of layered igneous rocks created as olivine and feldspar crystals accumulated at the base of a magma chamber.
The charnockite series includes rocks of many different types, some being felsic and rich in quartz and microcline, others mafic and full of pyroxene and olivine, while there are also intermediate varieties corresponding mineralogically to norites, quartz-norites and diorites.
Ferrohortonolite is a mineral variety in the olivine series composed of 70 % to 90 % fayalite and 30 % to 10 % forsterite or Fe /( Fe + Mg ) ratio of 0. 7 to 0. 9.
It is from the obsolete hortonolite terminology for the olivine series.
olivine and Mg
For example, the olivine group is described by the variable formula ( Mg, Fe )< sub > 2 </ sub > SiO < sub > 4 </ sub >, which is a solid solution of two end-member species, magnesium-rich forsterite and iron-rich fayalite, which are described by a fixed chemical formula.
** Ringwoodite: ( Mg, Fe )< sub > 2 </ sub > SiO < sub > 4 </ sub >, an abundant olivine polymorph within the Earth's mantle from about 520 to 660 km depth, and a rare mineral in meteorites
The mineral olivine ( when of gem-quality, it is also called peridot and chrysolite ), is a magnesium iron silicate with the formula ( Mg, Fe )< sub > 2 </ sub > SiO < sub > 4 </ sub >.
In contrast, Mg-rich olivine does not occur stably with silica minerals, as it would react with them to form orthopyroxene (( Mg, Fe )< sub > 2 </ sub > Si < sub > 2 </ sub > O < sub > 6 </ sub >).
* Dunite: more than 90 % olivine, typically with Mg / Fe ratio of about 9: 1.
Reaction 1c describes the hydration of olivine with water only to yield serpentine and Mg ( OH )< sub > 2 </ sub > ( brucite ).
olivine and sub
Compositions of olivine are commonly expressed as molar percentages of forsterite ( Fo ) and fayalite ( Fa ) ( e. g., Fo < sub > 70 </ sub > Fa < sub > 30 </ sub >).
olivine and >
* Nesosilicates ( lone tetrahedron )-< sup > 4 −</ sup >, e. g. olivine.
olivine and 2
The ideal reactions involve the magnesium endmember components of the olivine ( reaction 1 ) or serpentine ( reaction 2 ), the latter derived from earlier olivine by hydration and silicification ( reaction 3 ).
Mg-rich olivine has also been discovered in meteorites, the Moon, Mars, in the dust of comet Wild 2, within the core of comet Tempel 1, falling into infant stars, as well as on asteroid 25143 Itokawa.
Removal by reactions with olivine is an attractive option, because it is widely available and reacts easily with the ( acid ) CO < sub > 2 </ sub > from the atmosphere.
All the CO < sub > 2 </ sub > that is produced by burning 1 liter of oil can be sequestered by less than 1 liter of olivine.
Group-I kimberlites are of CO < sub > 2 </ sub >- rich ultramafic potassic igneous rocks dominated by a primary mineral assemblage of forsteritic olivine, magnesian ilmenite, chromium pyrope, almandine-pyrope, chromium diopside ( in some cases subcalcic ), phlogopite, enstatite and of Ti-poor chromite.
* Type 2 chondrites are those that have experienced extensive aqueous alteration, but still contain recognizable chondrules as well as primary, unaltered olivine and / or pyroxene.
The spectrum shows distinct olivine and pyroxene features at 1 and 2 micrometres, with a possibility of plagioclase.
Diabase normally has a fine, but visible texture of euhedral lath-shaped plagioclase crystals ( 62 %) set in a finer matrix of clinopyroxene, typically augite ( 20 – 29 %), with minor olivine ( 3 % up to 12 % in olivine diabase ), magnetite ( 2 %), and ilmenite ( 2 %).
* silica sand ( SiO < sub > 2 </ sub >), or chromite sand ( FeCr < sub > 2 </ sub > O ), or zircon sand ( ZrSiO < sub > 4 </ sub >), 75 to 85 %, or olivine, or staurolite, or graphite.
The entire volcanic Kaiserstuhl consists of rock types that contain feldspathoid minerals and olivine and are undersaturated with SiO < sub > 2 </ sub >.
olivine and </
Tetrahedral SiO < sub > 4 </ sub > units are found in olivine minerals, SiO < sub > 4 </ sub >, but the anion does not have a separate existence as the oxygen atoms are surrounded tetrahedrally by cations in the solid state.
olivine and 4
The presence of iron in the olivine or serpentine reduces the efficiency of sequestration, since the iron components of these minerals break down to iron oxide and silica ( reaction 4 ).
It has a rotational period of 4. 7012 hours, and is classified as an R-Type asteroid due to the presence of strong absorption lines in olivine and pyroxene with little or no metals.
olivine and consist
Mantle rocks shallower than about 410 km depth consist mostly of olivine, pyroxenes, spinel-structure minerals, and garnet ; typical rock types are thought to be peridotite, dunite ( olivine-rich peridotite ), and eclogite.
The volcanic rocks of the island consist of olivine basalt and trachyte.
They consist essentially of olivine and augite with a brownish glassy groundmass.
olivine and magnesium-rich
Spectral data from the spacecraft confirmed the asteroid was composed mainly of iron-poor minerals such as enstatite ( magnesium-rich pyroxene ), forsterite ( magnesium-rich olivine ) and feldspar.
It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron.
Peridotites are rich in magnesium, reflecting the high proportions of magnesium-rich olivine.
Part of the evidence that komatiites are not magnesium-rich simply because of cumulate olivine is textural: some contain spinifex, a texture attributable to rapid crystallization of the olivine from a magnesium-rich melt.
In contrast, picrites are magnesium-rich because crystals of olivine have accumulated in more normal melts by magmatic processes.
0.536 seconds.