Genesis of Sedimentary Fluorite in Light of Experimental Data
摘要
Correspondence of the main hypotheses of the sedimentary fluorite genesis with the available experimental data is discussed. Data on the saturation degree of seawater and large continental water basins by CaF2 are summarized. It was established that the fluorite formation at the carbonate–gypsum stages of salinization in evaporite basins with purely marine nourishment is impossible, since this requires an additional supply of fluorine from external sources, exceeding the marine F contribution by at least 1.5–4 times. Authigenic fluorite can also form in arid continental water basins similar to the modern, greatly dried-up Aral Sea. It is shown that interaction of sedimentary carbonate minerals with the seawater leads to the dissolved F removal, which is more than an order of magnitude greater for dolomite than for calcite and aragonite. According to a new physicochemical mechanism proposed for the authigenic fluorite formation, recrystallization of the primary finely dispersed carbonate minerals with a defective crystalline structure (for example, protodolomite) promotes a partial self-purification of the solid phase from incoherent elements, accompanied by the accumulation of dissolved F in pore waters until the CaF2 saturation is achieved and fluorite is deposited.