what means the significance of the presence of ankerite in the anoxic sedimentary environment?
Dear Mr. Mahboubi Chikh Younes,
ankerite [Ca(Fe++,Mg,Mn)(CO3)2] , an Fe- and Mn-bearing dolomite, is a typical marker mineral like siderite or Fe-bearing calcite, all of which accommodate bivalent iron in their lattice given anoxic conditions exist (may also be present in an oxidizing regime if the pH value allows it). Trivalent iron present under oxidizing conditions cannot enter the structure of these carbonate minerals and occurs, e.g., as “limonite” or hematite along cleavage planes. For a detailed description of the redox condition in an x-y plot displaying the pH and Eh (mV) you need to know the soluble components such as total sulfur or carbon dioxide activities in the aquatic system as well as the temperature of formation. For a detailed information about this issue consult the classical studies of Garrels & Christ (1965), where you will find the basics good for learning.
With kind regards
H.G.Dill
Mahboubi:
Besides Harald's useful answer, you may also have a look at this link:
Best
Syed
Article Geochemistry of gold-bearing carbonates, Beaconsfield gold m...
The regional carbonate alteration of the crust, usually associated with major shear zones or tectonic lineaments, is observed in many terranes, with little consensus on the origin of the fluids involved. So the dissolution of carbonate minerals has the potential to raise the pH of the pore water to near neutral. Dissolution of carbonate minerals releases calcium, magnesium, manganese, iron, and other cations that are present as solid-solution substitutions or as impurities, and increases the alkalinity of the water. At many sites, the mass of carbonate minerals contained in the mine wastes exceeds that of the sulfide minerals, and the rapid dissolution of carbonate minerals is sufficient to maintain neutral pH conditions through the mines or their waste piles. Neutral pH conditions have been observed in tailings impoundments derived from processing carbonate-bearing vein-type gold deposits (Blowes, 1990; McCreadie et al., 2000), and in open pits derived from gold mining (Shevenell et al., 1999).
Check This page:
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ankerite.
See you
Joel
