Yttrium (Y)



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Scandium is typically a trace element in most rocks and minerals. It lithophile and found in the trivalent state. Scandium differs from other rare earth elements in being much smaller and thus tends to substitute into early crystallizing phases with 6-fold coordination, such as pyroxenes and amphiboles. It has a similar size to Fe2+ , for which it commonly substitutes it.

  • Scandium is typically a trace element in most rocks and minerals. It lithophile and found in the trivalent state. Scandium differs from other rare earth elements in being much smaller and thus tends to substitute into early crystallizing phases with 6-fold coordination, such as pyroxenes and amphiboles. It has a similar size to Fe2+ , for which it commonly substitutes it.

  • Some independent Sc silicates: bazzite (Sc-analogue of beryl), jervisite (a pyroxene), thortveitite (a sorosilicate). They occur in alkaline magmatites or pegmatites.

  • .



It has a few phosphate, as pretulite (in metamorphic quartz-lazulite veins), and kolbeckite (in hydrothermal processes).

  • It has a few phosphate, as pretulite (in metamorphic quartz-lazulite veins), and kolbeckite (in hydrothermal processes).

  • In sedimentary environments, Sc behaves more like other rare earth elements but differs in being more readily

  • hydrolyzed. It concentrated than LREE by adsorption in clays, or organic matter in soils, or in Al-Fe oxides, e.g. in bauxite, laterite.



Yttrium (Y)

  • Yttrium (Y)

  • Universe: 0.007 ppm

  • Sun: 0.01 ppm

  • Carbonaceous meteorite: 1.9 ppm 

  • Earth's Crust: 30 ppm 

  • Seawater: 9 x 10-6 ppm



Lanthanium (La)

  • Lanthanium (La)

  • Universe: 0.002 ppm

  • Sun: 0.002 ppm

  • Earth's Crust: 34 ppm



The rare earth elements are perhaps the most significant group of trace elements in geochemistry. The lanthanide series develops by filling of 4f orbitals that are well shielded by 5s and 5p orbitals, leading to highly coherent behavior as a group. Among other things, this results in the trivalent state being especially stable and the ionic radius decreases in an unusually systematic fashion. The dominant controls on the geochemical behavior of the REE are their size (ionic radius), volatility, redox behavior and complexing behavior.

  • The rare earth elements are perhaps the most significant group of trace elements in geochemistry. The lanthanide series develops by filling of 4f orbitals that are well shielded by 5s and 5p orbitals, leading to highly coherent behavior as a group. Among other things, this results in the trivalent state being especially stable and the ionic radius decreases in an unusually systematic fashion. The dominant controls on the geochemical behavior of the REE are their size (ionic radius), volatility, redox behavior and complexing behavior.



The lanthanides (and Y) tend to be concentrated in magmatic liquids and late crystallizing phases. Of the major elements in the crust and mantle, only sodium and calcium come close in size to the REE, however substitution for these elements (especially Na) may lead to serious charge imbalance, because REE have been mainly trivalent.

  • The lanthanides (and Y) tend to be concentrated in magmatic liquids and late crystallizing phases. Of the major elements in the crust and mantle, only sodium and calcium come close in size to the REE, however substitution for these elements (especially Na) may lead to serious charge imbalance, because REE have been mainly trivalent.

  • Of great importance to geochemistry is the fact that Eu and

  • Ce commonly exist in other than trivalent states (Eu2+; Ce4+). Reduction of Eu occurs only at highly reducing,

  • typically magmatic conditions.



An example is that Eu becomes highly concentrated in feldspars (especially in plagioclase). Plagioclase is only stable to about 40 km on Earth and anomalous Eu behavior in magmatic rocks is a sign of relatively shallow igneous processes.

  • An example is that Eu becomes highly concentrated in feldspars (especially in plagioclase). Plagioclase is only stable to about 40 km on Earth and anomalous Eu behavior in magmatic rocks is a sign of relatively shallow igneous processes.

  • In contrast, Ce is oxidized almost exclusively under highly oxidizing surficial conditions, notably in early marine

  • diagenesis, to form manganese nodules and under certain

  • weathering conditions.



In most rocks and minerals, REE are trace elements and in

  • In most rocks and minerals, REE are trace elements and in

  • some cases minor elements; however, there are more than 70 minerals in which various REE are essential structural constituents. Among the most significant in geochemistry are Ianthanite, (La,Ce)2(CO3).8H2O, allanite (Ce,Ca,Y)2(AI,Fe)3(SiO4)3(OH), and the phosphates florencite CeAI3(PO4)2(OH), monazite La,Ce(PO4), xenotime Y(PO4) and fluorocarbonates (parisite, synchisite series). The name of mineral species are create the root name (monazite) plus the name of dominant REE in the structure: monazite-(Ce), monazite-(La), etc.



The REE substitute mainly Ca and Sr in structure (because of similar size of ions). E.g. in rock-forming silicates: amphiboles, pyroxenes, epidotes, but in apatite, fluorite.

  • The REE substitute mainly Ca and Sr in structure (because of similar size of ions). E.g. in rock-forming silicates: amphiboles, pyroxenes, epidotes, but in apatite, fluorite.

  • Constant REE/Y substitution is known in zircon, thorite (latter isomorphous with xenotime).





Often enriched in chemical weathering in clays and carbonates (with common substitutions of Ca), or by adsorption on surface of Mn-Fe oxides/hydroxides. Hydrated REE minerals can form other sediments or soils (e.g. lanthanite).

  • Often enriched in chemical weathering in clays and carbonates (with common substitutions of Ca), or by adsorption on surface of Mn-Fe oxides/hydroxides. Hydrated REE minerals can form other sediments or soils (e.g. lanthanite).

  • There are high REE concentration in bauxite, than relict phases (monazite, xenotime), secondary REE minerals (e.g. bastnasite), other rock-forming minerals with substitutions, finally as independent cations which can adsorbed on solid or gel-like phases (mainly on Fe-oxides/hydroxydes).



Under aqueous conditions, the rare earth elements exist mostly as a variety of complexes. Carbonates and bicarbonates dominate in seawater. For a number of rare earth complexes, such as fluorides and carbonates, the heavier (smaller) REE show a marked increase in stability.

  • Under aqueous conditions, the rare earth elements exist mostly as a variety of complexes. Carbonates and bicarbonates dominate in seawater. For a number of rare earth complexes, such as fluorides and carbonates, the heavier (smaller) REE show a marked increase in stability.



Titanium (Ti)

  • Titanium (Ti)

  • Universe: 3 ppm 

  • Sun: 4 ppm

  • Carbonaceous meteorite: 550 ppm

  • Earth's Crust: 6600 ppm

  • Seawater: 4.8 x 10-4 ppm



Titanium (4+) coordination is usually 6 (octahedral), but can be 4 coordinated (in some Al-deficient Ti-amphiboles and pyroxenes). Common 6 coordinated Ti phases are the rutile modification for TiO2 (rutile, brookite, anatase, there are polymorphs) and ilmenite (FeTiO3). 6 coordinated Ti is also known in kimzeyite and schorlomite garnets, titanite, various inosilicates such as titanaugite and in complex Ti-oxides/fluorides such as pyrochlore group minerals, and zirkelite, betafite, brannerite.

  • Titanium (4+) coordination is usually 6 (octahedral), but can be 4 coordinated (in some Al-deficient Ti-amphiboles and pyroxenes). Common 6 coordinated Ti phases are the rutile modification for TiO2 (rutile, brookite, anatase, there are polymorphs) and ilmenite (FeTiO3). 6 coordinated Ti is also known in kimzeyite and schorlomite garnets, titanite, various inosilicates such as titanaugite and in complex Ti-oxides/fluorides such as pyrochlore group minerals, and zirkelite, betafite, brannerite.

  • In the Earth's mantle, the perovskite (CaTiO3 ) may be the most common Ti-phase, but Ti3+ rich periclase (MgO) phases are also known.



Silicate glasses and melts (such as basalts) show a contrasted coordination chemistry for Ti: they contain essentially 5 coordinated Ti, as titanyl units or (Ti=O)O4. Highly polymerized magmas and glasses also

  • Silicate glasses and melts (such as basalts) show a contrasted coordination chemistry for Ti: they contain essentially 5 coordinated Ti, as titanyl units or (Ti=O)O4. Highly polymerized magmas and glasses also

  • show significant amounts of tetrahedrally coordinated Ti.

  • There are common Ti-containing minerals, as oxides in plutonic rock, in contrary as silicates in volcanics. The most important Ti-oxides are rutile, ilmenite, perovskite, Ti-containing magnetite. Titanite often shows Ca- REE/Nb substitutions.

  • It forms complex oxides and silicates in pegmatites with REE, Nb, Ta and Ca (e.g. pyrochlore minerals).



Ti3+ often occurs in mafic silicates, than pyroxenes, amphiboles (e.g. titanaugite). It can substitutes Fe3+, Al3+ and rare Mg2+.

  • Ti3+ often occurs in mafic silicates, than pyroxenes, amphiboles (e.g. titanaugite). It can substitutes Fe3+, Al3+ and rare Mg2+.

  • It concentrates high amounts in early basic magmatites (e.g. gabbros, norites) as Ti-magnetite, or ilmenite. High Ti-contents is known in alkali magmatites (e.g. phonolites, nepheline syenites), and their pegmatites. However, not only the simple oxides can be occur in this rocks, but complex silicates, than astrophyllite, Ti-garnets.



Near to the Earth's surface, Ti-oxides (rutile and ilmenite) are the most abundant Ti phases, because they are not very sensitive to external agents such as chemical weathering. They can be common in detritic sediments and metamorphic rocks. Such Ti minerals are useful tracers for valuable placers of gold, diamond, bauxites (etc.). The low solubility of Ti in water makes it unaggressive to the environment; however, reactive bio-inorganic molecules may be chemisorbed onto TiO2 surfaces. In contrary, the titanite (a rock-forming CaTiSiO5 mineral) often weathered and Ti moves in the hydrosphere, and later it forms secondary mixture of oxides, so-called leucoxene).

  • Near to the Earth's surface, Ti-oxides (rutile and ilmenite) are the most abundant Ti phases, because they are not very sensitive to external agents such as chemical weathering. They can be common in detritic sediments and metamorphic rocks. Such Ti minerals are useful tracers for valuable placers of gold, diamond, bauxites (etc.). The low solubility of Ti in water makes it unaggressive to the environment; however, reactive bio-inorganic molecules may be chemisorbed onto TiO2 surfaces. In contrary, the titanite (a rock-forming CaTiSiO5 mineral) often weathered and Ti moves in the hydrosphere, and later it forms secondary mixture of oxides, so-called leucoxene).



The leucoxene is mixture of different oxides, mainly rutile-brookite-anatase. The Ti-containing mafic rock-forming minerals relatively easy weathered and move to the hydrosphere. The Ti forms secondary phases (rutile, anatase, brookite) by diagenetic processes in sediments, such laterites, bauxites, clays or soils. The high Ti-contents of bauxite consist of not only relict phases, but diagenetic origin minerals, too.

  • The leucoxene is mixture of different oxides, mainly rutile-brookite-anatase. The Ti-containing mafic rock-forming minerals relatively easy weathered and move to the hydrosphere. The Ti forms secondary phases (rutile, anatase, brookite) by diagenetic processes in sediments, such laterites, bauxites, clays or soils. The high Ti-contents of bauxite consist of not only relict phases, but diagenetic origin minerals, too.





Zirconium (Zr)

  • Zirconium (Zr)

  • Universe: 0.05 ppm

  • Sun: 0.04 ppm

  • Carbonaceous meteorite: 6.7 ppm

  • Earth's Crust: 130 ppm 

  • Seawater: 9 x 10-6 ppm



Zr is a lithophile element, present essentially as Zr4+ in silicates but occurs sometimes in oxides. In Earth materials, Zr4+ coordination may be 6, 7 or 8. Six-coordinated Zr is observed in a wide number of rare minerals: as a major element in zirconosilicates and as a minor element in rock-forming silicates. For instance, Zr substitutes to Ti in a number of rock-forming silicates such as garnets, alkali-rich pyroxenes and amphiboles (like aegirine and arfvedsonite). 7-coordinated Zr is rare in minerals (as in baddeleyite and zirconolite, but also in metamict zircon, a naturally radiation damaged

  • Zr is a lithophile element, present essentially as Zr4+ in silicates but occurs sometimes in oxides. In Earth materials, Zr4+ coordination may be 6, 7 or 8. Six-coordinated Zr is observed in a wide number of rare minerals: as a major element in zirconosilicates and as a minor element in rock-forming silicates. For instance, Zr substitutes to Ti in a number of rock-forming silicates such as garnets, alkali-rich pyroxenes and amphiboles (like aegirine and arfvedsonite). 7-coordinated Zr is rare in minerals (as in baddeleyite and zirconolite, but also in metamict zircon, a naturally radiation damaged

  • zircon). Finally, 8-coordinated Zr is known mainly in crystalline zircon.



Simple, but most important and highly stable zirconium silicate is the zircon. Zr is concentrates in larger amounts in the acidic (e.g. granites) or in alkali magmatites (e.g. phonolites, nepheline syenites). However, the most highest Zr-content can be found in carbonatites. There are many complex Zr-silicates in alkali magmatites (e.g. eudialyte group minerals, catapleiite).

  • Simple, but most important and highly stable zirconium silicate is the zircon. Zr is concentrates in larger amounts in the acidic (e.g. granites) or in alkali magmatites (e.g. phonolites, nepheline syenites). However, the most highest Zr-content can be found in carbonatites. There are many complex Zr-silicates in alkali magmatites (e.g. eudialyte group minerals, catapleiite).

  • Zr is one of the most used trace elements in geochemistry

  • because this highly charged cation usually shows a clearly

  • incompatible behavior for most rock-forming minerals (olivines, pyroxenes, amphiboles, felspars). However, in peralkaline melts Zr can partition efficiently towards garnets (kimzeyite), inosilicates (aegirine, arfvedsonite, aenigmatite).



Zircon is the most abundant Zr phase close to the Earth's

  • Zircon is the most abundant Zr phase close to the Earth's

  • surface but baddeleyite has also been mined from alkaline

  • rocks (syenites, carbonatites). These phases are not very sensitive to weathering but radiation effects can partially destroy their atomic structure (when actinides, mainly U-Th are substituted to Zr). Zircon can be common in detritic sediments and metamorphic rocks and constitutes a useful tracer for gold, diamond, bauxites. Zr is not particularly aggressive to the environment, except in some nuclear waste sites (because of radiogenic isotopes of Zr). Because of its very stable minerals, small part of Zr move to the hydrosphere, later it adsorbed in the surface of clay minerals or Fe-Mn oxides/hydroxydes.



Hafnium (Hf)

  • Hafnium (Hf)

  • Universe: 0.0004 ppm

  • Sun: 0.0003 ppm

  • Carbonaceous meteorite: 0.04 ppm

  • Earth's Crust: 12 ppm 

  • Seawater: 9.2 ppm



Chemically it shows close analog of zirconium, and is almost always enriched or depleted to the same degree. The most important mineral host by far in the Earth's crust is zircon (Zr,Hf)SiO4 , where Hf averages 1%, corresponding to the terrestrial Zr/Hf ratio of ca. 37.

  • Chemically it shows close analog of zirconium, and is almost always enriched or depleted to the same degree. The most important mineral host by far in the Earth's crust is zircon (Zr,Hf)SiO4 , where Hf averages 1%, corresponding to the terrestrial Zr/Hf ratio of ca. 37.

  • We know only two independent Hf minerals: hafnon, (Hf,Zr)SiO4, the Hf-dominant analogue of zircon.



Thorium (Th)

  • Thorium (Th)

  • Universe: 0.0004 ppm

  • Sun: 0.0003 ppm

  • Carbonaceous meteorite: 0.04 ppm

  • Earth's Crust: 12 ppm 

  • Seawater: 9.2 ppm



Thorium occurs as a trace element in common rocks and rock-forming minerals, with concentrations in the range of a few ppb to tens of ppm. Th4+ has an ionic radius of~ 1 A (similar to that of U4+). Th along with the other incompatible elements (e.g. U, K, Rb and REE) accumulates in the residual magma and is incorporated into the late crystallizing silicate phases. Th and U are more abundant in granites and associated accessory minerals than in mafic and ultramafic rocks. There are many minerals in which Th is a major constituent. There are relatively common and they generally occur as accessory minerals.

  • Thorium occurs as a trace element in common rocks and rock-forming minerals, with concentrations in the range of a few ppb to tens of ppm. Th4+ has an ionic radius of~ 1 A (similar to that of U4+). Th along with the other incompatible elements (e.g. U, K, Rb and REE) accumulates in the residual magma and is incorporated into the late crystallizing silicate phases. Th and U are more abundant in granites and associated accessory minerals than in mafic and ultramafic rocks. There are many minerals in which Th is a major constituent. There are relatively common and they generally occur as accessory minerals.



Common Th minerals are thorianite (ThO2) and thorite (ThSiO4), latter is isomorphic with zircon (because of similar size of cations – 1.10 and 0.87). It concentrates in large amounts in pegmatites of granitoids.

  • Common Th minerals are thorianite (ThO2) and thorite (ThSiO4), latter is isomorphic with zircon (because of similar size of cations – 1.10 and 0.87). It concentrates in large amounts in pegmatites of granitoids.

  • Often substitutes Zr or forms compounds with Zr in magmatic processes. However, the most important commercial mineral of Th is monazite, which is a rare earth phosphate in which Th almost all substitutes for REE.



During weathering of rocks and minerals, Th is by and large retained in the regolith. This results from the association of Th with resistant accessory minerals (e.g. monazite, xenotime) and its chemically reactive nature in solution. Any Th which is solubilized from the host-rocks during weathering is rapidly adsorbed from dissolved phase to the surface of particles (on clay minerals, Fe-Mn oxides/hydroxydes).

  • During weathering of rocks and minerals, Th is by and large retained in the regolith. This results from the association of Th with resistant accessory minerals (e.g. monazite, xenotime) and its chemically reactive nature in solution. Any Th which is solubilized from the host-rocks during weathering is rapidly adsorbed from dissolved phase to the surface of particles (on clay minerals, Fe-Mn oxides/hydroxydes).

  • The concentration of dissolved Th in natural waters is quite low. Some studies in soil profiles indicate that Th is mobilized by organic matter in top soil, but is precipitated in regions of low organic content.





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