Phosphorus (P) is an important element in chemostratigraphy for provenance and depositional environment determination. So, which are the element-mineral links of P?
Phosphorus (symbol P; atomic number 15; relative atomic mass 30.973762) [Link to webelements.com/phosphorus]
P has three oxidation states, -3, +3, and +5.
Phosphorus has one naturally occurring isotope (31P).
In geochemical analysis, phosphorus is commonly reported as an oxide, i.e. P2O5, in weight percent.
Common element-mineral links of P
The most common element-mineral links of P are phosphates such as: apatite (Ca5(PO4)3(OH,F,Cl), monazite (Ce,La,Nd,Th,Sm)(P,Si)O4), and xenotime (YPO4).
Zr in siliciclastic rocks
Phosphates such as apatite (Ca5(PO4)3(OH,F,Cl), but also monazite (Ce,La,Nd,Th,Sm)(P,Si)O4) and xenotime (YPO4) are the principal P-bearing minerals in siliciclastic sediments. However, mica and bone material, as well as teeth (e.g. fish bones and teeth) can be additional sources in sediments such as bone-beds.
If P is associated with detrital apatite, it commonly occurs with other heavy minerals, which may be expressed in elevated Zr and Hf (zircon), Ti, Nb, and Ta (rutile and other Ti-heavy minerals), Y and REEs (monazite and xenotime).
Biogenetic phosphates, e.g. in bone-beds, are commonly associated with Y and Ce, Sr, Th, and U.
As a biological component, P may be indicative of organic material, e.g. in up-welling zones/deposits or lagunal settings, principally as biogenetic apatite, as well as through phosphate adsorption onto clay minerals in organic-rich black shales.
High P concentrations in marine sediments may indicate low sedimentation rates resulting in condensed sections.
Apatite is largely insoluble in neutral and alkaline conditions. In acidic environments, however, apatite is quite soluble.
Elevated P concentrations may be indicative for a magic igneous provenance, but this needs to be verified through other element concentrations such as of Cr, Cu, and Ni.
P in carbonate and evaporites rocks
Phosphorus is uncommon in carbonates and evaporite rocks unless induced by detrital input, such as rivers or (wind-blown) dust.
P in igneous rocks
Phosphorus concentrations in igneous rocks vary greatly, but appear to be highest in mafic rocks. Xenotime and monazite are the common P-bearing igneous minerals.