Download Calcium in magmatic processes

Alkaline earth metals
Beryllium (Be)
Universe: 0.001 ppm (by weight)
Sun: 0.0001 ppm (by weight)
Carbonaceous meteorite: 0.03 ppm
Earth's Crust: 2.6 ppm
Seawater: 0.02 ppm
Beryllium in magmatic processes
In magmatic differentiation it enriches in granite and
alkaline magmatic rocks, e.g. nepheline syenite,
especially in pegmatitic processes. Small ionic radius
(0,34), similar to Si (0,39), and little coordination number
(4). Important Be-minerals in pegmatites: beryl,
chrysoberyl, phenakite, all silicates. Rare oxide
(bromellite), phosphate (berillonite), borate (hambergite),
too.
Occassionally appears in skarns and hydrothermal ore
deposits (e.g. helvite). It can replaces Al or Si in skarn
silicates (garnets, vesuvianite etc.).
The largest Be-accumulation connect to acidic pyroclastic
rock (here the main Be-minerals is bertrandite).
Beryllium in weathering and sediments
In weathering processes move together with Al, such in
clays, bauxites, and recent marine sediments.
It can concentrates in coals (high enrichment in coal ash,
too), by absorption in organic matter with REE and other
elements (Nb, Ge, V, etc).
It concentrates in plants in biosphere, too.
The salts of beryllium have strong toxicity.
Magnesium (Mg)
Universe: 600 ppm (by weight)
Sun: 700 ppm (by weight)
Carbonaceous meteorite: 1.2 x 105 ppm
Earth's Crust: 23000 ppm
Seawater: 1200 ppm
Magnesium in magmatic processes
Magnesium is a highly compatible element during mantle
melting, and residual mantle is more magnesian than fertile
mantle. Magnesium remains a compatible element during
crystallization of magmas because olivine, orthopyroxene
and/or clinopyroxene are typical liquidus phases. Hence,
Mg is concentrated in the Earth's mantle, while in the crust
it is most abundant in the oceanic crust and the lower
continental crust.
Magnesium is a minor or trace element in highly evolved
igneous systems, and typical Mg contents of granites are
on the order of 0.2-5.8 mg/g.
Magnesium in magmatic processes
It appears both simple and complex compounds. It
concentrates in ultrabasic-basic magmatites.
Characteristic constituent of mafic rock-forming minerals,
as forsterite/olivine, Mg/Fe pyroxenes (e.g. enstatite) and
amphiboles.
Different abundance was detect about calcium-analogue
compounds, such fluorite – sellaite or apatite –
wagnerite. However, inverse abundance is well-known,
see periclase – lime, or brucite – portlandite pairs.
Characteristic Mg2+ / Fe2+ substitution in all rock-forming
minerals. The Mg dominance in high temperature and in
calk-alkaline magmatites. On the other hand, Fe
dominance appear in most of oxides (except of spinel).
It forms mainly carbonates in post-magmatic processes.
Rock-forming Mg-minerals
Magnesium in weathering processes and
sediments
During weathering of rocks, Mg readily dissolves in the
weathering solutions and enters to the hydrosphere.
Magnesium is removed from ocean water by carbonate
precipitation, but even so, Mg is a conservative element
in seawater. It enriches in marine and freshwater
sediments, too. It has similar characteristics than sodium,
but differs from calcium. It forms late precipitates (Mg- or
Mg-K-salts) in evaporites. Many times it occurs close
associates with borates.
Magnesium carbonates
It very rare forms directly from seewater or freshwater as
dolomite. Much more crystallize in long diagenetic
processes.
The Mg carbonates form from limestone by Mgmetasomatism with Mg-rich solutions. In the order of
total crystallization: limestone dolomitic limestone 
dolomite  magnesite. There are many substitutions in
cation position in these carbonates (e.g. Mg2+,Fe2+, Mn2,
Zn2) e.g. at Rudabánya ore deposit and some magnesite
localities of Szepes-Gömör Ore Mts., Eastern Slovakia.
Mg carbonates (mainly magnesite) crystallize from Mg-rich
ultrabasites and metamorphites (e.g. serpentinite) by
hydrothermal solutions, too.
Dolomitization
In high temperature experiments ( <200°C), following an
induction period, dolomitization proceeds rapidly, producing
the metastable phases (high Mg calcite) and calcian
dolomite before stoichiometric dolomite is formed. Several
hydrothermal and metamorphic dolomites are stoichiometric
and ordered. However, sedimentary dolomites exhibit
different degrees of ordering and compositional ranges. At
low, sedimentary temperatures, the types of natural waters
appears to occur are characterized by high supersaturation,
high Mg/Ca ratio and elevated CO3- and HCO3
concentrations. The dolomite produced is, however, weakly
ordered and calcian. Holocene dolomites are fine-grained,
poorly ordered, and may contain up to 7-8 mol% CaCO3.
Magnesium in biosphere
It forms around 10 pH as hydroxide in soils.
Common microcomponent in low-class plants. Essential
componens of high plants, e.g. in chlorophil. It catalytic
effects is well-known in photosynthesis. Important
activator of some enzyms, too.
Some marine plants, animals (e.g. algae) have high Mgcontent. Occassionally determined from skelets of shells
and gastropodas. In high-class animals (and the man)
common constituent in bones, musculars, and nervous
tissues. Mg-containing carbonates and/or phosphates
can produce occlusion in venas (e.g. coronary
occlusion).
Calcium (Ca)
Universe: 70 ppm (by weight)
Sun: 70 ppm (by weight)
Carbonaceous meteorite: 11000 ppm
Earth's Crust: 41000 ppm
Seawater: 390 ppm
Calcium in magmatic processes
Ca-content of the bulk Earth is variously estimated to be
16.2-19.3 mg/g. Mid-ocean ridge basalts typically contain
about 81 mg/g Ca. Calcium becomes a compatible element
during crystallization of magmas once plagioclase and/or
clinopyroxenes begin to crystallize, and during crustal
melting. The Ca contents of typical granites are of the order
of 2-18 mg/g. Calcium is concentrated in the oceanic ( ~81
mg/g) and the lower continental (37-67 mg/g) crusts of the
Earth.
Calcium in magmatic processes
Well-known simple and complex compounds both
magmatic and metamorphic rocks. Because of ionic
radius of Ca very often forms in the structure of silicates
(both mafic and felsic silicates).
Important Ca silicates: Ca-garnets (grossular, andradite)
Ca-pyroxenes (augite, diopside, hedenbergite), Capyroxenoides (wollastonite), Ca-amphiboles (actinolite,
tremolite, hornblende-family), epidote-group, Ca-micas,
(margarite, clintonite), Ca-plagioclase (anorthite),
felspatoids (cancrinite, haüyne), Ca-zeolites (laumontite,
scolecite, series of heulandite and chabazite).
Special Ca silicates found as characteristic minerals in high
temperature skarns (wollastonite, larnite, rankinite etc.).
Calcium in magmatic processes
Ca has low abundace in early magmatic differenciates,
except anorthite (in anorthosite). However, the basic
magmatic rocks, one of main mineral is a Ca-rich basic
plagioclase. About the half part of Ca crystallize in later
differentiates, as Ca-rich pyroxenes, and amphiboles.
Other Ca-containing compounds, e.g. oxides are
accessoric components (e.g. perovskite, pyrochlorgroup), they occur mainly in alkaline magmatics.
There are wolframates (scheelite), molibdates (powellite)
and especially carbonates (ankerite, dolomite, calcite,
aragonite) in post-magmatic origin.
Calcium in weathering and sediments
During weathering of rocks, Ca readily dissolves in the
weathering solutions and enters to the hydrosphere.
The ratio of Ca : Na is lower in sediments (e.g. in clays)
than magmatic rocks. Ca similar to Na, because it builds
in clay minerals in small amounts.
There is a different in Ca-contents between seewater and
freshwater (latter contains more Ca, because of quicker
weathering of anorthite than albite). Large masses of Cacarbonates forms in sedimentary environment, in some
cases with evaporites.
Latter environment not only carbonates, but Ca-sulphates
(gypsum, anhydrite) phosphates (apatite-OH, apatite-Cl,
apatite-F) form in large amounts.
Calcium carbonate and the carbonic acid
system
Calcium carbonate and the carbonic acid system have a
major role in the geochemistry of sedimentary carbonates
which form, dissolve and reprecipitate at the Earth's
surface and in the oceans. Karst dissolution, which shapes
the landscape of carbonate terrains, the formation of
carbonate platforms and atolls, the dissolution of deep-sea
sediments, the development of porosity in limestones and
dolomites and its destruction via precipitation of cements in
vugs are some of the phenomena depending on the
calcium carbonate and carbonic acid system interactions.
It forms chemical (direct precipitates from water), and
biological (skeletal parts of organisms) ways.
Calcium carbonate polymorphs
Calcium carbonate crystallizes in a variety of polymorphic
forms. The two most common natural polymorphs are
calcite (trigonal) and aragonite (orthorhombic). A third
polymorph, vaterite (hexagonal) has been found in
gallstones, tissues of fractured gastropod shells and as
rare alteration product. The vaterite is very instable phase.
Calcium carbonate polymorphs
Under Earth's surface conditions, calcite is the most
abundant and thermodynamically stable polymorph of
CaCO3. Aragonite is relatively abundant and it is stable
polymorph at high pressure. But at surface pressure is
unstable and should transform to calcite. Nevertheless,
aragonite persists in tectonically uplifted blueschist facies
metamorphic rocks, and precipitates both inorganically
(e.g. caves) and through biogenic processes to form
carbonate platform sediments and cements. Vaterite is
always metastable under sedimentary conditions.
Magnesian calcites are an important variety of CaCO3, they
are an important component of the shallow-water marine
sediments either as direct precipitates or as components of
the skeletal parts of organisms.
Strontium (Sr)
Universe: 0.04 ppm (by weight)
Sun: 0.05 ppm (by weight)
Carbonaceous meteorite: 8.9 ppm
Earth's Crust: 360 ppm
Seawater: 7.6 ppm
Barium (Ba)
Universe: 0.01 ppm (by weight)
Sun: 0.01 ppm (by weight)
Carbonaceous meteorite: 2.8 ppm
Earth's Crust: 500 ppm
Seawater: Atlantic surface: 4.7 x 10-3 ppm
Atlantic deep: 9.3 x 10-3 ppm
Pacific surface: 4.7 x 10-3 ppm
Pacific deep: 2 x 10-2 ppm
Strontium and barium in magmatic
processes
They rarely form indepentent minerals in magmatic
processes (e.g. barium feldspars, the celsianparacelsian-hyalophan series).
In common rock-forming minerals the Sr2+ substitutes Ca2+
(e.g. plagioclases, apatites, pyroxenes), while Ba2+
replaces K+ (mainly in alkali feldspars, micas).
The barium content in magmatic rocks normally increases
with increasing SiO2 concentration. Granitic rocks with high
Ca concentrations are generally enriched in barium, and
alkaline rocks are usually highly enriched in strontium.
Strontium and barium in magmatic
processes
Low abundaces in pegmatithic and pneumatolithic phases.
In contrary, hydrothermal processes they show higher
abundances with many independent minerals.
Examples of Sr: celestite, strontianite, svanbergite, and Srzeolites (brewsterite-Sr, chabazite-Sr). It substitutes Ca
most often in calcite, aragonite, and gypsum.
Examples of Ba: barite, witherite, Ba-zeolites (brewsteriteSr, harmotome, phillipsite-harmotome solid solutions,
edingtonite). It replaces K in alkali feldspars (e.g. adularia
in epithermal ore deposits). High frequency of barite –
celestite solid solution in hydrothermal processes (socalled baritocelestite).
Strontium in weathering and sedimentary
environment
After weathering Sr moves more amounts to the
hydrosphere, than Ca. In the evaporation it concentrates in
gypsum, calcite, anhydrite by substitution, or it forms
independent minerals, e.g. celestite.
In sedimentary rocks it is predominantly found in carbonate
rocks composed of calcite and/or dolomite. It may also be
present in carbonate cement. Diagenetic and weathering
processes may further distribute and re-distribute strontium
among the major rock groups. The amount of Sr found in
these rocks, depends on the depositional/diagenetic
redistribution of Sr with Ca. In contrast, in other
sedimentary rocks the distribution of Sr into feldspars
depends on the substitution with K.
Barium in sedimentary environment
In many natural environments, aqueous barium
concentrations are controlled primarily by ion exchange
and sorption reactions. Also important in the aqueous
geochemistry of barium is the low solubility of barite. In
alkaline systems, the soluble nature of witherite can control
barium mobility.
It has better absorption characteristics than strontium, so it
moves lesser amounts to oceans. The Sr : Ba ratio in
magmatic rocks is 0.6, while in the seewater is 260.
In sedimentary rocks, barium normally occurs as barite, or
in clays, and in feldspars. Barium can accumulates in
manganese oxides in soil and ferromanganese nodules in
the oceans.
Barium and strontium in sedimentary
environment and biosphere
Celestite and strontianite common sedimentary Srminerals, but they occur always in small amounts.
Sr in soils: it concentrates high amounts if Ca-content is
higher. Occassionally forms mainly as celestite or
strontianite. The precipitation of Ba-Sr sulphates are
controlled by microorganism, too.
Sr (and rare Ba) occurs in small amounts in skelets of
organics.