Extraction of ore components from mafic magmas by immiscible carbonate and salt melts: evidence from melt and fluid inclusions in minerals

摘要

Melt and fluid inclusions were studied in minerals of two alkaline igneous complexes, Verkhnedunkeldykskii massif in the eastern Pamirs and Gardiner massif in East Greenland. Minerals of the Verkhnedunkeldykskii massif contain silicate and salt (phosphate-sulfate-carbonate) melt inclusions. The early immiscible carbonatitic melts were formed at temperatures higher than 1000℃, and phosphate-fluoride-chloride melts were trapped at 740-570℃. With decreasing temperature, the salt melts evolved into highly saline hydrothermal solutions. Melilite from the melilitolite of the Gardiner complex contain cogenetic silicate and carbonate melt inclusions, which were trapped at 1060-900℃. Crystallization of high-temperature carbonate and salt melts in inclusions gave rise to a variety of minerals including those enriched in trace elements (REE, Ba, Sr).