1. Manganese, iron, cobalt, nickel, platinum group elements

3. Manganese Universe: 8 ppm (by weight) Sun: 10 ppm (by weight)
Carbonaceous meteorite: 2800 ppm
Earth's Crust: 1100 ppm
Seawater:   Atlantic surface: 1 x 10-4 ppm
Atlantic deep: 9.6 x 10-5 ppm

4. Manganese in magmatic processes
Manganese abundance is 0.112% in ultrabasic rock and 0.096% in granites, so does not shows significant difference. Much more interesting the ratio of Mn:Mg from the ultrabasic to acidic character (from 1:100 till 1:1) or Mn:Fe (from 1:50 till 1:10). Mg, Fe, Mn order the substitution of crystal lattice (ionic radii of 2+ valence states: 0,78, 0,83, 0,91). Its independent phase very rare, rather the Mn2+ substitute in the structure of mafic rock-forming minerals (mainly Fe2+, Mg, Ca substitution) in biotite, tourmaline, ilmenite, magnetite, pyroxenes, amphiboles.

5. Manganese in magmatic processes
However, in post-magmatic processes it forms many independent phases. There are silicates (spessartite), oxides (columbite-Mn, tantalite-Mn), phosphates in pegmatite, wolframites (e.g. hübnerite) in pneumatolithic processes. There are mainly carbonates with Mn-substitution (Mn-bearing calcite, ankerite, siderite, magnesite) and rhodochrosite in hydrothermal or hydrothermal-metasomatic processes. It occurs in rare sulphides such environments, e.g. alabandine (cubic MnS).

6. Manganese in metamorphic processes
There are characteristic Mn silicates in metamorphic environments, such Mn3O4 hausmannite, rhodonite, spessartite, tephroite. It forms mainly from the Mn-rich black shales to metamorphic processes.

7. Manganese in sedimentary processes
It has an oxidation-reduction and coordination chemistry similar to that of iron, but exists naturally in three stable oxidation states +2, +3, +4 in solids and only +2 state when dissolved in natural waters. While Mn2+ is stable at acidic to neutral pH, it is easily oxidized by O2 in basic solutions. The six-coordinate ionic radii (nm) are 0.80 for Mn2+, 0.70 for Mn3+, and 0.60 for Mn4+. The reactivity and cycling of manganese is primarily determined the pH and Eh of associated water: dissolution or precipitation of phases due to oxidation-reduction of manganese ions, solubilization of Mn2+.

9. Manganese in sedimentary processes
It is present in igneous, metamorphic and sedimentary rocks, and it is found in most waters. Manganese can be described by two interrelated global cycles: a terrestrial rock-water cycle and a marine/lacustrine sediment-water cycle. Manganese is supplied to both cycles by igneous rock. Once exposed, igneous manganese is weathered, primarily by oxidation-reduction, acid dissolution, and organic chelators. From solution, manganese is redeposited into fresh or saline waters as oxides, carbonates, silicates and many different adsorbed phases. Manganese movement within each cycle is quite dynamic. Manganese also moves from the terrestrial cycle to the marine/lacustrine cycle by land drainage into the waters.

10. Manganese in sedimentary processes
Microbes are actively involved in manganese cycling by participating in oxidation-reduction, dissolution and precipitation of Mn. Manganese cycles are important because manganese is an important micronutrient to plants and animals but can be toxic at high levels of consumption.

11. Manganese in sedimentary processes
It concetrates in close association with iron in oxidized environments, however it forms independent phases. Strongly adsorbed some metals, such K, Ca, Ba, Ti, Co, Ni, Cu, Zn Pb, and sometimes forms different oxides whith various chemical compounds (cryptomelane, rancieite, romanechite, asbolane, coronadite etc.). It forms carbonates in reductive environments, and it has various substitution of Fe-Mn-Mg-Ca. The Mn origins from volcanic activities in deep-marine sediments. So, there are oxides, oxi-hydroxides, carbonates and sulphates in sedimentary environments.

12. Iron (Fe) Universe: 1100 ppm (by weight) Sun: 1000 ppm (by weight)
Carbonaceous meteorite: 2.2 x 105 ppm  
Earth's Crust: ppm 
Seawater:   Atlantic surface: 1 x 10-4 ppm    
Atlantic deep: 4 x 10-4 ppm

13. Iron in magmatic processes
Iron is a component in all mineral classes (we know about 700 Fe-bearing minerals). It occurs chiefly as reduced, ferrous iron with magnesium in mafic silicates such as olivines, pyroxenes, amphiboles and biotite. It is also present in pyrite, pyrrhotite, magnetite and ilmenite. The abundance of iron (and mafic minerals) is decrease from ultrabasic/basic to acidic rocks. The Fe2+ substitutes Mg2+, the Fe3+ Al3+ in minerals. In post magmatic processes often occur as complex oxides, sulphides, carbonates, and phoshates.

15. Iron in weathering and sedimentary processes
The principal source of iron in the hydrosphere is the weathering of iron minerals from igneous and metamorphic rocks, including the silicates olivine, pyroxenes, amphiboles, and biotite. Sedimentary shales can be significant sources to the extent that they contain pyrite and marcasite. The aqueous geochemistry of iron can be summarized by the two rules: Rule 1: Oxidizing conditions promote the precipitation of iron, reducing conditions promote the solution of iron. Rule 2: Acid conditions generally promote the solution of iron, alkaline conditions promote the precipitation of iron.

16. Iron in weathering and sedimentary processes
The average concentration in seawater is 0.01 mg/l, and it occurs primarily in the ferric (Fe3+) state. Under reducing conditions found near the bottom of some lakes and rivers, where highly soluble ferrous iron is favored over oxidized ferric iron, concentrations may reach several mg/l. Concentrations of iron in groundwater range from 1 to 10 mg/l. Low pH water, produced by industrial waste or sulfide oxidation (chiefly pyrite) associated with mining and natural weathering processes, can contain hundreds to thousands of mg/l iron.The oxidation of iron in aqueous solution can either be driven by biologically mediated reactions involving the genus Thiobacillus or can occur as inorganic process with dissolved oxygen.

17. Iron in weathering and sedimentary processes
The weathering of iron-bearing minerals is driven by the dissolution of CO2 into water (either atmospheric or soil solutions), producing carbonic acid which in turn attacks minerals. These reactions produce cations, silica and bicarbonate in solution. In general, weathering reactions of iron-bearing minerals occur in the same order as they are formed according to Bowen's reaction series. The phases which form at the higher temperatures (e.g. olivine) weather more rapidly than those which form later, at lower temperatures (e.g. biotite). An interesting exception to this order are the iron sulfides pyrite and pyrrhotite, which can form at relatively high temperatures.

18. Iron in weathering and sedimentary processes
The transport of iron in surficial exogenic environments must be either in solution or as detrital particles. Primary iron-bearing phases, which have not as yet chemically weathered, are carried by wind or water. Ferrous iron released by chemical weathering will readily oxidize to form ferric oxides. These ferric oxides can form a discrete phase or, very commonly, coat other solids which are present as detritus. Some iron minerals, such as magnetite, do not chemically weather at an appreciable rate and may be preserved and carried significant distances. Others, such as the sulfides pyrite and pyrrhotite, rarely escape chemical weathering and are almost never found occurring as detrital grains.

19. Iron in weathering and sedimentary processes
Large accumulations of ferric oxides can be produced, forming materials which can be described as banded iron formations. Rates of precipitation reactions indicate that phases such as amorphous ferric hydroxide (ferrihydrite or „limonite”) form first and, with time, dehydrate (lose water) to form the more thermodynamically favored phases such as hematite (Fe2O3), with goethite (FeOOH) as a middle step. Thus, the red beds (hematite) of today may have been the yellow beds (limonite) of ages ago. Ferric oxides in sedimentary environments in which organic matter is abundant, are destabilized with the onset of reducing conditions produced by bacterial degradation of the organic matter.

20. Iron in weathering and sedimentary processes
Simultaneously, sulfate sulfur (the stable form of sulfur in oxidizing conditions) is reduced to sulfide sulfur, which can react with ferrous iron in the low Eh environment to form iron sulfides. However, pyrite to be the stable phase, much as with the ferric oxides precipitates, the initial iron sulfide precipitate is a poorly crystalline iron mono-sulfide form (the kinetically favored phase), which, in time, alters to the thermodynamically favored phase, pyrite (or pyrrhotite). If sulfide sulfur is not present, siderite (FeCO3) may form if pCO2 , pH and the ratio of Fe2+/Ca2+ are relatively high (e.g. a fresh water swamp). If pCO2 is low, but silica is present, iron silicates such as glauconite, berthierine may form.

21. Environmental geochemistry of iron
Iron plays an important role in environmental geochemistry, both degrading and improving the quality of natural waters necessary for humans and many other life forms. The sulfide minerals, particularly pyrite, are more and more a part of the waste and ore stream of modern mining activity. Pyrite is unstable at the Earth's surface (like most other endogenically formed iron minerals) and weathers to form acidic iron sulfate solutions called acid rock drainage (ARD). These acidic waters often carry trace metals with them (i.e. copper, cadmium, arsenic), which are also released to solution on the oxidation of the sulfides.

22. Environmental geochemistry of iron
Ferrous iron which is oxidized to ferric iron readily oxidizes in surficial environments to form amorphous precipitates These precipitates, which may be found in aquatic as well as terrestrial environments, exhibit a strong tendency to scavenge trace metals. Studies of the diagenesis of sediments have routinely showed trace metals to be associated with ferric iron phases. The sorption of metals from aqueous solution by ferric iron precipitates may be approximated by a number of sorption models. The sorption process is affected by pH and ionic strength, with near-neutral pH and low ionic strength favoring maximal adsorption of cations (e.g. Pb2+, Cu2+).

23. Cobalt (Co) Universe: 3 ppm (by weight) Sun: 4 ppm (by weight)
Carbonaceous meteorite: 600 ppm 
Earth's Crust: 20 ppm 
Seawater: Pacific surface: 6.9 x 10-6 ppm    
Pacific deep: 1.1 x 10-6 ppm

24. Nickel (Ni) Universe: 60 ppm (by weight) Sun: 80 ppm (by weight)
Carbonaceous meteorite: ppm 
Earth's Crust: 90 ppm 
Seawater: Atlantic surface: 1 x 10-4 ppm    
Atlantic deep: 4 x 10-4 ppm

25. Cobalt in magmatic processes
Co2+ has an ionic radius in octahedral coordination which is intermediate between Mg2+ and Fe2+ (0.735 A); thus it substitutes for these cations in several silicates. In basaltic rocks, the correlation with Fe and Mg is significant, in granitic and metamorphic rocks the correlation with Mg persists. It shows enrichment in the high temperature post magmatic processes, it forms arsenides, or arsenid-sulphides (e.g. cobalthite – CoAsS, safflorite – CoAs2, skutterudite – CoAs3). Easily substitutes Ni in structure of Ni-bearing minerals, both early differentiations, or post- magmatic processes (e.g. pentlandite – (Fe,Ni)9S8 and pyrrhotite - FeS).

27. Cobalt in weathering and sedimentary processes
Co is easily solubilized during weathering and does not form residual silicate minerals in soils (average Co concentration is 7 ppm). The distribution of Co is mostly determined by the fate of Fe and Mn oxides; complexation by organic substances is of intermediate relevance. The concentration of Co in fresh surface and groundwater varies mostly between 0.04 and 0.35 g/l; higher concentrations occur in contaminated areas (Netherlands, 1-11 g/l) or mineralized zones. In aquatic systems Co is transported both adsorbed to suspended particles and dissolved, with a large portion complexed by organic ligands.

28. Cobalt in weathering and sedimentary processes
For suspended particles, participation of Co in the Mn redox cycle and the possible oxidation of Co2+ to Co3+ on Mn oxy-hydroxide surfaces are as important as direct adsorption to clay particles or indirect adsorption to different particle surfaces through organic substances. In seawater Co concentration shows the behavior of scavenged elements, decreasing with depth from about 0.05 to 0.01 ~ g/1. High Co concentrations are found in deep-sea clays (74 ppm) and Mn-nodules (up to 2%) with maxima occurring in the vicinity of mid-ocean ridges. There are many arsenates/sulphates of cobalt in the oxidation zone of Co-bearing ore deposits (e.g. erytrine, a Co-arsenate).

30. Nickel in magmatic processes
Nickel and iron are the most important components of the Earth's core. In the Earth's mantle, the concentration is quite low (2000 ppm) and even lower in the Earth's crust (105 ppm). Nickel occurs in trace amounts in most rock-forming minerals, especially in olivines. In minerals, Ni2+ is mostly 6-fold coordinated (giving a green or yellow coloration) due to a high crystal field stabilization energy in this site. 4- and 5-coordinated Ni2+ found in silicate glasses and melts. It concentrates to early differenciates as sulphides: pentlandite-pyrrhotite association – (Fe,Ni)9S8 and FeS. Because of similar ionic radii of Ni and Mg (0.78) it substitutes mainly to Mg in phyllosilicates (e.g. chlorites, serpentine minerals).

31. Nickel in magmatic processes
It shows enrichment in high temperature post-magmatic processes, where it forms mainly arsenides, and arsenides-sulphides: nickeline – NiAs, millerite – NiS, gersdorffite – NiAsS, ullmannite – NiSbS. Its largest accumulations are in the five-elements ore deposits (Ni-Co-As-Bi-Ag).

32. Nickel in weathering and sedimentary processes
Nickel is easily mobilized during weathering and it is often co-precipitated with iron and manganese oxides. In tropical rain belt areas the ultramafic rocks are weathered, giving nickel-rich silicate ores, such as garnierite, a mixture of hydrous trioctahedral phyllosilicates. There are many arsenates/phosphates/sulphates of nickel in the oxidation zone of Ni-bearing ore deposits. Among them the most important the annabergite (hydrated Ni-arsenate). In seawater, Ni concentration increases with depth and follows the distribution of silicate and phosphate.

33. Platinum group elements
Platinum, ruthenium, osmium,
palladium, iridium, rhodium

34. Platinum (Pt) Universe: 0.005 ppm (by weight)
Sun: ppm (by weight) 
Carbonaceous meteorite: 0.1 ppm 
Earth's Crust: ppm 
Seawater: Pacific surface: 1.1 x 10-7 ppm    
Pacific deep: 2.7 x 10-7 ppm

35. Platinum group elements in magmatic processes
Platinum is both a siderophile, e.g. native platinum; platinidiridium (Pt,Ir), some Pt-alloys, and a chalcophile, e.g. braggite (Pt,Ni,PdS ), sperrylite (PtAs2) element. Platinum is typically more abundant in ultramafic and mafic rocks than in sedimentary or felsic igneous rocks. Highest concentrations of Pt in ultramafic rocks range from 1 to 30 ppm; the concentrations of Pt in igneous rocks range from 1 to 75 ppb. The PGE form together with chromite and pentlandite-pyrrhotite association in the early differenciated rocks. They miss in the intermedate to acidic magmatics, however show relative enrichment a few special Co-Ni-sulphide associations.

36. Platinum group elements in magmatic processes
Anomalous concentrations of Pt (low ppb) along with Ir are present in approximate chondrite-like proportions in a clay layer marking the Cretaceous/Tertiary boundary, and this is one of the key pieces of evidence for a massive meteorite impact at the Cretaceous/Tertiary boundary.
The main elements of the PGE are platinum and palladium, while rhodium, iridium, rhutenium and osmium comprise about 10% of the total platinum metals.

37. Platina group elements in sedimentary processes
Most of PGE minerals (except sulphides-arsenides) are very stable in weathering, so they move as relicts to the clastic sediments. Platinum anomalies ranging from 48 to 150 ppb have been found in Mississippian black shales. Impact-derived phases were not found in these shales and Pt is believed to have been derived from detritus weathered from nearby ultramafic rocks.