The REE fractionation of the vein calcite is explained mainly by fractional crystallization, where the initially precipitated epidote in the veins preferentially incorporates most of the light REE (LREE) pool, leaving a residual fluid enriched in the HREE from which calcite precipitated. A noteworthy feature is substantial heavy REE (HREE) enrichment of calcite in the vein system, in contrast to the relatively flat patterns of greisen calcite. This is explained by efficient REE retention in the granite via incorporation in accessory phosphates, zircon, and fluorite and unfavorable conditions for REE partitioning in fluids at the magmatic and early hydrothermal stages. Low calculated в€‘REE concentration for bulk vein (15 ppm) compared to greisen (75 ppm), country rocks (173вЂ“224 ppm), and the intruding granite (320 ppm) points to overall low REE levels in the hydrothermal fluids emanating from the granite. Fluid-inclusion microthermometry reveals that multiple pulses of moderately to highly saline aqueous to carbonic solutions caused greisenization and vein formation at temperatures above 200вЂ“250вЊ and up to 430вЊ at the early hydrothermal stage in the veins.

A temporal and thus genetic link between the granite and the greisen/veins is established via high spatial resolution in situ Rb-Sr dating, supported by several other isotopic signatures ( ОґВівЃґ S, вЃёвЃ· Sr/ вЃёвЃ¶ Sr, ОґВ№вЃё O, and ОґВ№Ві C). The greisen consists of coarse-grained quartz, muscovite, and fluorite, whereas the veins mainly contain quartz, calcite, epidote, chlorite, and fluorite in order of abundance. This study focuses on concentrations and fractionation of rare earth elements (REE) in a variety of minerals and bulk materials of hydrothermal greisen and vein mineralization in Paleoproterozoic monzodiorite to granodiorite related to the intrusion of Mesoproterozoic alkali- and fluorine-rich granite.

Veins of the earth character sheet