Identification and source determination of Magnesite in the Maharlou Lake sediments

Category Marine geology
Group GSI.IR
Location The 25 Symposium of Geosciences
Author R.Lak-F.Fayazi
Holding Date 03 July 2007

Maharlou Lake, located in southwest Iran, is an intra-continental sedimentary basin. Its area is about 280 km2 with an average water depth of 1.5m during wet seasons. 13, 80 to 170 cm deep cores taken using plastic tubes, provided 102 sediment samples. The samples were analyzed sedimentologically and mineralogically by running sieve analysis, calcimetry, X- ray difractometry, optical and SEM microscopy, and C14 age dating tests as well as defining major and minor constituent elements. There is very fine lamination in the sediments but three major types of sediments consist of Carbonates, evaporites and siliciclastic was recognized. All of sediments in the center of the lake are evaporits and in the marginal zone are chemical and siliciclastic sediments. siliciclastic sediments consist of Quartz, Calcite, Dolomite, Feldspar, Muscovite and illite. Source of them are rocks of the catchments. These sediments are silt dominated, well sorted, subrounded to rounded and sub spherical to spherical shape. Chemical sediments consist of carbonate and evaporite minerals. Carbonate minerals (calcite, Dolomite, Aragonite and magnesite) precipitate at the beginning of brine evolution after that sulfate and chloride (Gypsum, Halite, Bassanite, Glauberite, polihalite and Bischofite) are precipitate. Distinctive changes in sediment laminae are indicative of Lake water table changes through the time. Where occurrence of delicate with laminea is regarded as Magnesite, a significant with horizon not only in the cores taken from marginal parts of the South of the lake but also in a core provided obtained from a zone located in North west to central parts of the lake. Magnesites in the marginal zone precipitate at the beginning of brine evolution but Source of Magnesite in the center of the lake suggests some bicarbonate type springs.