Pegmatite fluids of different origins and their implications for mineralization

Characteristics of ore-forming fluids as inferred from detailed studies of inclusions indicate that pegmatites may have different origins. For example, the granitic pegmatite at Mufushan is originated from magma differentiation at 1100-200°C, while the No. 3 Pegmatite Vein in Xinjiang may owe its origin to a pegmatitic magma produced via metamorphic anatexis at 1140-200°C. Pegmatite fluids of the above two types are a melt-liquid system and may evolve into a solid-melt or solid-liquid system that would have a critical bearing on metasomatism and intergranular solutions. The Minxi pegmatite, on the other hand, resulted from metamorphic differentiation, with its fluid (formed at 400-180°C) exhibiting many features of metamorphism. Pegmatites of different origins are distributed in tectonic units of different characters and are different both in the nature of ore-forming fluid and in the source of ore- metals. This concept of polygene launches a challenge to the traditional belief that pegmatite is exclusively originated from magma differentiation and may be helpful for the establishment of a new theory of pegmatite genesis.[PUBLICATION ABSTRACT]