engleski

Occurrence of vivianite in alluvial Quaternary sediments in the area of Sesvete (Zagreb, Croatia)

Boreholes Badel-1 and Badel-2, located in Sesvete near Zagreb, were drilled through 71.50 and 84.40 m of Quaternary sediments, respectively. Within these sediments, the occurrence of earthy aggregate and 1-2 mm nodules of the deep blue coloured mineral vivianite was observed. Interpretation of the depositional environment, provenance of the sediments and vivianite occurrence was based on sedimentological, mineralogical and palynological analyses. Three different facies within the alluvial environments were interpreted: 1) gravels and sands typical of alluvial environments 2) structureless beds of silts and clays deposited in oxbow lakes, marshes and floodplains 3) chaotic sediments deposited in the upper part of the alluvial fan. Macroscopically, an earthy aggregate is essentially an occurrence of flattened vivianite crystals grouped in clusters. The studied sediments are the product of intensive weathering of different types of rocks from Medvednica Mt. with a prevalence of green- schists. Rocks from Medvednica Mt. as the source of ferrous iron (Fe2+) and phosphorus (P), and reductive depositional environments can indicate conditions for genesis of vivianite.

vivianite ; Quaternary sediments ; alluvial ; informal Bistra Formation ; Zagreb ; Croatia

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