During an examination of outcrops around Wadi Halfa North Sudan we found a discoidal shape grain of Barite Concretions or Sand Barite.
I read an article at geology.com which explains that such barite concretions are not uncommon in sandstone. The crystals of barite grow in between particles of sand and have many different shapes.
Dear Mr. Daoud,
just this type was investigated in the cited paper:
DILL, H.G., BERNER, Z., KAUFHOLD, S., WEBER, B. and METZ, U. (2013) Facies-related baryte mineralization bearing Cu-Zn sulfides in Miocene estuarine deposits of the upper Rhein Graben (Wetterau, Central Germany).- Sedimentary Geology, 296: 55-71.
Abstract: Abstract
Baryte with or without base metal sulfides is quite common in sediments deposited in open marine environments or in continental sedimentary basins. Its precipitation is caused by hydrothermal processes, related to diagenesis, and frequently mediated by biogenic processes. The current study is focused on siliciclastic sandstones of Miocene (Aquitanian) age in an estuarine environment in the Wetterau region of the Rhein Graben, central Germany. In the estuarine environment only the central basin and the landward delta are host to a diagenetic and subsequent hydrothermal mineralization.
Diagenesis took place under near-ambient ( T ≈ 25°C) conditions and resulted in strong pyritization (-0.75 5) in the central basin. Diagenesis is more landward represented by a pervasive silicification (pH < 12) in deltaic sandstones.
Epigenetic mineralization (100°-130°C) with pyrite in the central basins was succeeded by Cu-Zn-(Sb) minerals (0.75 < Eh < 0 / 5 < pH < 11), silicification and kaolinisation (2< pH < 9.5) and eventually by the formation of gibbsite (3
Late but still. Hypergenic barite should also be added to the list of possible genetic types of barite. We have been solving for a long time where barite microparticles come from in the silt fraction of river sediments and soils, until we discovered it as a common component of coatings on weathered aleuropelites in soil profiles and on the outcrops. Hypergenic barite is an overlooked mineral, but due to the very low solubility of BaSO4, its formation is absolutely necessary.
Article Formation of baryte and celestine during supergene processes...
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