Dear Dr. Kanouo,

do they not belong to the metamorphic panafrican series but are unconformably overlying the panafrican series? Generally I would first try to establish carbonate content, e.g. the form of carbonate present e.g.. (Siderite/Ankerite, Rhodocrosite, Calcite/Dolomite). Very often early diagenetic carbonates have very elevated Fe, Mn contents and a very wide compositional range is possible. For my taste it would be important to establish the depositional/early diagenetic environment both from field evidence and petrographical, mineralogical and geochemical studies. Is it limnic (a stratified tropical freshwater lake basin) or do we have we any hint/indication of marine influence? Are those fish fossils from the same formation? Could we extract microfossils?

Best regards from Hannover,

The attached pictures are that of carbonate nodules from clay-rich sedimentary rocks.

I guess thin section studies may help in deciphering the genesis of calcareous nodules.

Dear Dr. Kanouo:

The key to the lock will certainly lie within the fine –grained matrix based upon which you should come closer to the true environment of formation. Step-by-step analyze the fine-grained host:

1. Perform a separation into different grain size classes < 63 µm, 63 – 300 µm and > 300 µm (concretions)

2. Use the < 63 µm for clay mineralogy

3. Use the 63 – 300 µm fraction for heavy and light minerals

4. Use > 300 µm for thin section examination and biodetritus under the stereomicroscope

During step 4 you can also address the structure and composition of your concretions.

Prior to that you should carefully map the outcrop as to visible textures and structures.

What I can deduce from the photograph of the outcrop is a younger vaguely bedded overburden. A small channel in the foreground reminds me of a valley fill.

Due to my lack of information on the geological setting of these modern sedimentary rocks and of further mineralogical and chemical data, I am reluctant to speculate further on what the nodules might be.

First provide a sound geological and mineralogical database than you will also obtain a tailor-made answer.

I wish you much success H.G.Dill

The sub-sequence succession shows granitic basement overlie by sandstones, and/or claystones with carbonate nodules. These claystones are overlain by alluvial clays

Dear Dr. Kanouo,

I have already touched the mineralogical composition. What do you know about the mineralogy ? With regard to the geological setting there are some fundmental questions. What is the thickness of the sand-clay series like ? Does it strongly vary and within which range according to the granitic paleo-landscape ?

Kind regards

H.G.Dill

Thanks for replying Professor

We have just completed field survey. No analyses have yet been carried out. We are still seeking for funding and laboratory facilities

We have try to map unlithified clay deposits ( alluvial clays and supergenes clays) in the locality (100 km2)

alluvial clays locally alternate with sandy lavels in flats and terraces found in main streams. these alluvial sequences locally overlie claystones, granitic and amphibolite schist basemen.

Dear Dr. Kanouo,

I see that you have not yet crossed the boundary from field to laboratory work. Nevertheless, I am convinced that by means of a meticulous mapping, sectioning and measuring in the field (try and carry out everthing what you cannot do in the lab) you will be able constrain the environment of deposition to a large extent.

If you need basics and literature dealing with argillaceous environments of formation read the following review papers:

DILL, H.G. (2020) A geological and mineralogical review of clay mineral deposits and phyllosilicate ore guides in Central Europe - A function of geodynamics and climate change.- Ore Geology Reviews 119 (on line)

DILL, H.G. (2017) Residual clay deposits on basement rocks: The impact of climate and the geological setting on supergene argillitization in the Bohemian

Massif (Central Europe) and across the globe.- Earth Sciences Reviews 165: 1-58.

DILL, H.G. (2016) Kaolin: soil, rock and ore From the mineral to the magmatic, sedimentary, and metamorphic environments.- Earth Sciences Reviews 161: 16-129.

They are available on the Researchgate server where I have saved all my digital prints. The most easy way is via a request.

I wish you much success

H.G.D.

Thanks Professo,

if possible you can send these good paper to me to this address [email protected]

Please send an official request through RG , because the selection is easier due to an automatic process

HGD

Dear Professor,

i thank you for the interest on our research work. What is lacking for our research on economic mineral exploration and study of localized mineral occurrences and deposits is the absence of laboratory facilities in Cameroon. Funding is also a limited factor as we mainly use our monthly salary to fund field works.

I in particular, is really interested to do good research. Cameroon is mainly a greenfield. We young researchers still have to search and give value to soil and subsoil deposits which can be found in Cameroon.

I am really impressed after visiting your research works in your researchgate. I am really impressed. Congratulation. My dreams are to be able to do what you are doing. Congratulations once more.

Best regards

Dear Dr. Kanouo, when I looked at your two photos in more detail - they looked very friable - this might be due to recent weathering, but could as as well by a primay feature. Plz try to consolidate some subsamples with coloured araldite (or similar) to get thin sections. I'd be in interested in a section from rim to core. Stay safe and best regards! P.S.: (JHU numbers for Kamer were at 255 at 10:00 am).

Good morning Dr Kringle

happy to read your answer. The clay deposits are three types in this locality: “ alluvial“, consolidated clays, and supergenic clays. The pictures show two alluvial clays locally overlying consolidated clay deposits . That is the stratigraphy.

The coronavirus is worrying. Pleace, take care @and stay bless.

Have a nice time in Germany

Best regards

Dear Dr. Kanouo,

may I provide you with some remarks? Alluvial describes the environment of deposition which is part of the supergene zone. It may be clay mud, mud or silt. It is nothing but the non-indurated type of what comes next. Consolidated clays, which can be claystones siltstones or mudstone depending on the content of clay-sized particles, and are also supergene. My suggestion is to provide us with a precise litholog showing the thickness and all the structures and features which you recognized in the field. This will be a step forward and renders you to come closer to the origin of this lithology.

H.G.Dill

I think its belonginging to mother rocks that is weathering

Thanks for your answer