Dear Mr. Karbassi,

your question cannot be answered in a simple way as far as the genetic part of your question is concerned. Considering the technical part I suggest the "Chemist´s Workbench" that might be of assistance and help you find a solution to many of your issues in the camp of sedimentology.

The Eh-pH diagrams are valuable tools to describe, e.g., the sedimentary processes under near-ambient conditions, as it is the case with chemical sediments and residues (duricrusts and orecretes = metalliferous duricrusts / see attached file). You can contribute to the paleoclimate, intrastratal solution in soil types and the topmost part of the lithosphere, as well as hydrology. I have attached a file which will help you get an insight into part of this field of study. If you need further information, you might download some papers from the RG server on weathering and sediment-hosted metal deposits. I have always attempted at the end of my studies  to model thermo-dynamically the physical-chemical regime of formation. It is a bit easier in the sedimentary realm than in metamorphic and magmatic rocks where T and P have a stronger say. In sediments, even under near-ambient conditions the temperature should not be cast aside when constructing an Eh-pH-cross plot. It is governed by the climate and the process of oxidation. You may find some information also in this file attached.

Good luck !

H.G.Dill

Dear Mr. Karbassi,

your question cannot be answered in a simple way as far as the genetic part of your question is concerned. Considering the technical part I suggest the "Chemist´s Workbench" that might be of assistance and help you find a solution to many of your issues in the camp of sedimentology.

The Eh-pH diagrams are valuable tools to describe, e.g., the sedimentary processes under near-ambient conditions, as it is the case with chemical sediments and residues (duricrusts and orecretes = metalliferous duricrusts / see attached file). You can contribute to the paleoclimate, intrastratal solution in soil types and the topmost part of the lithosphere, as well as hydrology. I have attached a file which will help you get an insight into part of this field of study. If you need further information, you might download some papers from the RG server on weathering and sediment-hosted metal deposits. I have always attempted at the end of my studies  to model thermo-dynamically the physical-chemical regime of formation. It is a bit easier in the sedimentary realm than in metamorphic and magmatic rocks where T and P have a stronger say. In sediments, even under near-ambient conditions the temperature should not be cast aside when constructing an Eh-pH-cross plot. It is governed by the climate and the process of oxidation. You may find some information also in this file attached.

Good luck !

H.G.Dill

Thank you Dr. Dill. The paper sent by you is exactly what I was looking for. Many many thanks. I also thank Dr. Towe for his suggestion. The diagrams are helpful.

Truly yours

karbassi

Dear Dr. Karbassi,

good to hear, that the file was helpful for you. As uranyl compounds were not included in this paper , I attach another one in which this gap is closed and the application of Eh- and pH values are shown for weathering, hydrology and geomorphology. I like these chemical compounds because they are excellent for physical-chemical calculations of low-temperature processes and they posess a clock inherent to the chemical system. Have a closer look at these uranium minerals.

Good luck !

H.G.Dill

Dear Prof. Dill

Thank you so much for the very useful materials. 

Truly yours

karbassi

An example:

In an estuarine environment, where there is large variation in salinity and pH with tide, the exchangeable and carbonate phases of metals in sediments do get affected. Mobilization of these phases and some time diffusion to water column was observed. When we work in the sediment column in mangrove areas, mobilization of manganese from deeper more anoxic sediments towards surface was observed. The manganese prefers to form oxide in the surface layers.

Dear Dr. Nayak

Thank you for the information on the mobility of Mn. I have worked out on the geochemistry of Mn during my Ph.D thesis when I was a student in India. The mobility of elements and specially Mn can vary from place to place under various environmental conditions. As Prof. Dill has indicated, the Eh and pH can play an important role in this direction.

Truly yours

karbassi

Great. It is nice to look at different phases of metals with respect to pH and Eh instead of total / bulk metal as different phases of a given metal respond differently.

Regards

Nayak

Dear Nayak

Thank you for supporting words.

karbassi