Please enable JavaScript.
Coggle requires JavaScript to display documents.
Iron (Iron in Permian (Bauxite (Fe oxide, aluminium source), Coal…
Iron
Iron in Permian
Bauxite
Fe oxide, aluminium source
Coal
compressed / metamorphosed plant material
Gypsum & halite evaporites
Ironstones
esp important during Jurassic
Bauxite
Aluminium hydroxide
Al = very immobile element
Oxidised aluminium doesnt move in sedimentary environment
Aluminium builds up in position
--> forms bauxite (rock ore)
Iron occurrence
One of most common elements on Earth
Few percent
present in practically all sedimentary rocks
Exceeds 15% in ironstones & iron formations
important Fe reserves
2 valence
states iron
Ferrous iron = divalent Fe2+
Ferric = trivalent Fe3+
Surface chemistry = strong control
behaviour of iron
precipitation of its minerals
Precambrian vs Phanerozoic
Fundamental differences btwn iron deposits
Precambrian - (Banded) Iron Formations
Phanerozoic - Ironstones
Phanerozoic Ironstones
Thin units
usually
Oolitic commonly
Deposited in
localised
areas
Precambrian
Iron Formations
Thick units
Various Fe minerals interbedded with cherts
Deposited in large intercratonic basins
Permian Paleogeog
All continents joined to form Pangaea supercontinent
Located near equator mostly
Tethys Ocean = large
Sediments Influenced by
Latitude
Climate
Ancient sediments encode lots of valuable
info about past envmtal conditions
Geochemical Mobility
Can infer if elements likely to occur
near to sediment source
distally
Expected gradation of occurence as f(mobility)
Bauxite - local occurrence (nr source)
Iron - transitional envmts
Silica - deep sea (distally as v mobile)
Manganese - deep sea
True up to a point
cannot explain everything with this
tho useful consideration
Iron mobility
Ferric Iron (Fe3+)
immobile
oxidised state (rust)
Ferrous Iron (Fe2+)
soluble & mobile
may move away in solution