Transcript Sodium

Mineralogy and
Geochemistry
Lecture: Sándor Szakáll
Practice: Ferenc Móricz
Aim of the course
• Distribution and abundance of chemical elements in the
spheres of the Earth, especially: appearance in the
minerals (solid, crystalline compounds, elements).
• Chemical elements in magmatic, sedimentary and
metamorphic processes, positions in the structure of the
minerals. Predominant, substituting and trace elements
in minerals.
• Positive anomalies, enrichments of chemical elements in
magmatic, sedimentary and metamorphic processes.
• Appearances of the elements in hydrosphere and
biosphere
Programme
1) Hydrogen and alkaline metals
2) Alkaline earth metals
3) Boron, aluminium, carbon, silicon
4) Rare earth elements, titanium, zirconium
5) Uranium, thorium, vanadium, niobium, tantalum
6) Chromium, molybdenium, tungsten
7) Manganese, iron, cobalt, nickel
8) Copper, gold, silver, platina group elements
9) Zinc, cadmium, mercury, gallium, indium, thallium
10) Tin, lead, arsenic, antimony, bismuth
11) Nitrogen, phosphorus, oxygen
12) Sulphur, selenium, tellurium, haloids, noble gases
Hydrogen (H)
Universe: 7.5 x 105 ppm (by weight)
Sun: 7.5 x 105 ppm (by weight)
Carbonaceous meteorite: 24000 ppm
Earth's Crust: 1500 ppm
Seawater: 107800 ppm
Carbonaceous meteorites: their compositions are considered to
be close to that of the solar nebula from which the Solar system
condensed.
Hydrogen in the lithosphere
1) Enrichment in the late period of magmatic processes:
especially in pneumatolithic, and hydrothermal system
(in the fluids and aqueous solutions). In volcanic vapor
(fumarolae) as water, or in haloids as HCl, HF or H2S.
2) In the structure of minerals: hydroxil group as anions
(hydroxiles/oxi-hydroxiles) or additional anions (e.g.
amphiboles, micas, alunite-jarosite minerals); in loosely
bonded water molecules of the crystal structure (some
sulphates, phosphates, arsenates, zeolites, clay
minerals, especially smectites etc.), as independent H+
ions in rare salt minerals.
3) Water molecules in porus of the rocks. In rock-forming
quantities as ice. The ice really one of the most
important mineral of hydrogen.
Hydrogen in the hydrosphere,
atmosphere, and biosphere
It concentrates largest quantities as water. Lesser amounts
in volcanic vapors (HCl, H2S, NH3 etc.).
Continous cycle of water between litosphere, hydrosphere,
atmosphere. Geochemically importance of water in the
chemical alteration, diagenesis, and soil formation.
H+ ions occurs in the aqueous solutions. As H2 gas
molecules found in the atmosphere.
Hydrogen (and carbon) main constituent of organic
compounds. Some of them have crystalline state (they
are the organic minerals). Essencially component of
hydrocarbons.
The water always contains
some compounds in solution state.
The ratio of these components
depends of the chemical compounds
of the host-rocks
This world map shows how the salinity of the oceans changes slightly from
around 32ppt (3.2%) to 40ppt (4.0%). Low salinity is found in cold seas,
particularly during the summer season when ice melts. High salinity is found in
the ocean 'deserts' in a band coinciding with the continental deserts. Due to cool
dry air descending and warming up, these desert zones have very little rainfall,
and high evaporation. The Red Sea located in the desert region but almost
completely closed, shows the highest salinity of all (40ppt) but the
Lithium (Li)
Universe: 0.006 ppm (by weight)
Sun: 0.00006 ppm (by weight)
Carbonaceous meteorite: 1.7 ppm
Earth's Crust: 20 ppm
Seawater: 0.18 ppm
Lithium in magmatic processes
It is enriched in ferromagnesium minerals (e.g. amphiboles,
pyroxenes, see Li-type inosilicates), but it does not
substitutes in feldspars structure. It mainly replaces Mg
or Fe2+ (ionic radius of Li+ 0.68, Mg2+ 0.66, Fe2+ 0.74).
It concentrated in later stages of magmatic differentiation
(pneumatolithic, pegmatitic), and forms separate phases,
as spodumene, petalite, lepidolite, zinnwaldite, elbaite.
About micas (e.g. biotite, muscovite) it does not replaces
alkali metals, Na or K (than feldspars), but it substitutes
Al or Mg, too.
The largest postmagmatic accumulations have pegmatitic
or pneumatholitic origin with Li-bearing silicates.
Lithium in weathering and sediments
Lithium is readily absorbed by clay minerals during
weathering. In this processes it moves similarly than Mg. It
can accumulates in evaporites or claystones.
The Li/Mg ratio is 0.0034 in magmatic rocks, while 0.00008
in seewater (the reason of difference is the absorption
facility in clays). It appears dissociated Li+Cl- forms in
thermal waters, and mineral waters.
There are three types of brine deposit (continental,
geothermal and oil-field) with the most common being
continental saline desert basins. They are located near
tertiary or recent volcanoes and are made up of sand,
minerals with brine and saline water with high
concentrations of dissolved salts. In clay deposits, lithium is
found mainly in the mineral smectite (hectorite variety).
Lithium in water
The total lithium content of seawater is very large and is
estimated as 230 billion tonnes, where the element exists
at a relatively constant concentration of 0.14 to 0.25 parts
per million (ppm). However, lithium is present in seawater,
commercially viable methods of extraction have yet to be
developed.
One potential source of lithium is the leachates of
geothermal wells, which are carried to the surface.
Recovery of lithium has been demonstrated in the field.
The lithium is separated by simple filtration.
Sodium (Na)
Universe: 20 ppm (by weight)
Sun: 40 ppm (by weight)
Carbonaceous meteorite: 5600 ppm
Earth's Crust: 23000 ppm
Seawater: 11500 ppm
Potassium (K)
Universe: 3 ppm (by weight)
Sun: 4 ppm (by weight)
Carbonaceous meteorite: 710 ppm
Earth's Crust: 15000 ppm
Seawater: 450 ppm
Sodium and potassium in magmatic rocks
Sodium is a major element in the Earth, especially in crustal
rocks. The bulk Earth Na content is variously estimated to
be about 1.6-1.8 mg/g. Sodium is an essential constituent of
many rock-forming minerals (there are almost silicates),
where it is typically in either 6- or 8-fold coordination.
Common minerals in which Na is an essential constituent
include plagioclase (felsic part: albite), paragonite, Naamphiboles, Na-pyroxenes (aegirine), nepheline, sodalite,
zeolites (analcime, natrolite), Na-tourmalines. Under high
pressure, Na can substitute in pyroxene as the jadeite
component, NaAlSi2O6. Some alkali magmatic rocks contain
other exotic Na minerals, e.g. NaF, villiaumite, pectolite.
Sodium and potassium in magmatic rocks
Common minerals in which potassium is an essential
constituent include alkali feldspars (orthoclase, microcline,
sanidine), leucite, biotite series, muscovite, phlogopite.
Sodium and potassium are volatile lithophile elements and
are monovalents. Both elements concentrated in the upper
continental crust of the Earth.
They concentrate highly amounts in alkali magmatic rocks
(one of Na and K series in which nepheline, leucite and the
alkali amphiboles/pyroxenes are the index minerals). The
Na/K ratio decrease from basic to acid magmatites.
Potassium, like sodium, is enriched acidic magmas. Basic
and ultrabasic rocks, which are rich in iron and magnesium,
contain little potassium, and sodium.
Sodium and potassium in weathering
During weathering of rocks, Na and K liberated by mineral
breakdown readily dissolves in the weathering solutions
and enters to the hydrosphere. Like all of the alkali
elements, Na and K ions are highly soluble in aqueous
solutions. In contrast to sodium, potassium migrates only
slightly on the earth’s surface. Weathering of rocks leads
to partial transfer of potassium to water, but this is rapidly
absorbed by organisms and clay minerals; therefore, river
waters are poor in potassium and much less potassium
than sodium reaches the oceans. In the ocean, potassium
is absorbed by organisms and bottom silts (e.g. a main
component of glauconite). For this reason ocean waters
contain only 0.038 percent potassium (25 times less than
sodium).
Sodium and potassium in weathering
The difference in abundance of K and Na in sediments or
surface waters is the difference of K and Na appearance
in the structure of clay minerals (it is much more Kbearing clay minerals than Na-bearing ones). See illite,
glauconite.
Plus, the difference of weathering features sodiumfeldspars and plagioclases (see table). Finally, better
absorption features of potassium than sodium (see soil
minerals, or manganese oxides/hydroxides).
Sodium and potassium in evaporites
The largest sources of Na and K are in the evaporites
(chlorides, sulphates, rarely borates, nitrates). They form
by evaporation from salt-containing waters.
Seewater and freshwater differ about cation/anion
compositions, so the non-marine evaporitic mineral
asseblages are far more diverse than marine
assemlages. The non-marine evaporites consist of
mainly Na-salts (chlorides, halite, carbonates,
thermonatrite, natron, trona, and sulphates, mirabilite,
thenardite), in contrary to marine evaporites, in which
many K-salts can accumulate. There are 5 typical Naassociations: 1) Na-CO3-Cl; (2) Na-CO3-SO4CI; (3) NaSO4CI; (4) Na-Mg-SO4Cl; (5) Ca-Mg-Na-Cl.
Sodium and potassium in biosphere
Na and K not only lithophil, but definitely biophil elements,
too. Na is characteristic microcomponent of plants (it
occurs higher amounts in marine plants). It is the main
cation in body fluids in the animals and the man. Sodium
is an essential mineral that regulates blood volume,
blood pressure, osmotic equilibrium and pH. Because of
ion equilibrium very important the fixation of Na/K ratio in
the organics.
The play of K is similar than Na in organics, but rather in
plants (e.g. synthesis of chlorophyl). It plays an important
role in the physical fluid system of humans and it assists
nerve functions. As the K+, concentrate inside cells, and
95% of the body's potassium is so located.
Rubidium (Rb)
Universe: 0.01 ppm (by weight)
Sun: 0.03 ppm (by weight)
Carbonaceous meteorite: 3.3 ppm
Earth's Crust: 60 ppm
Seawater: 0.12 ppm
Cesium (Cs)
Universe: 0.0008 ppm (by weight)
Sun: 0.008 ppm (by weight)
Carbonaceous meteorite: 0.14 ppm
Earth's Crust: 3 ppm
Seawater: 3 x 104 ppm
Rubidium in magmatic processes
Rubidium is strongly incompatible with almost all mantle
minerals (except phlogopite), and is therefore strongly
enriched in the continental crust relative to the mantle
(overall crustal abundance ~32 ppm). It is suggest that
rubidium is strongly depleted in the lower crust relative to
the upper crust ( 5.3 ppm vs 112 ppm). It appears mainly in
the late-stage stadiums, pneumatolithic and pegmatitic. It
substitutes K in silicate structures (alkali feldspars, micas).
In the late-stage magmatic products, such as pegmatites,
tend to have extremely high concentrations of Rb (> 1000
ppm). The Rb has only one mineral, as rubicline (it occurs
close association with microcline).
Cesium in magmatic processes
Because of low abundance in Earth crust, Cs does not form
any common rock-forming minerals. Rather, Cs substitutes
for K in rock-forming minerals (e.g. in alkali feldspars,
biotite and muscovite).
The Cs contents of typical granites are of the order
of 1300-6000 ng/g. Hence, Cs is concentrated in the upper
continental crust of the Earth.
It mainly accumulates in pegmatites, where it has some
independent minerals, among them the most important is
the pollucite (a tectosilicate).
Rubidium and cesium in weathering and
sedimentary rocks
The behavior of rubidium in sedimentary processes is
controlled by the adsorption of Rb onto clay minerals (illite
and montmorillonite), which adsorb Rb+ more strongly than
K+. In contrary to Rb not incorporated in significant
amounts into carbonate minerals. So, they behave than K
in sedimentary processes, absorption in clays, or replace K
in evaporite minerals.
During weathering of rocks, Cs readily dissolves in the
weathering solutions and enters to the hydrosphere. Like
all alkali elements, Cs ions are highly soluble in aqueous
solutions.