The mineralogical characteristics of the hydrothermal types alteration from Nistru ore deposit, Baia Mare metallogenetic district

摘要

The hydrothermal alteration types, which have affected intrusive and volcanic rocks from Nistru ore deposit, are related to fluids composition varied in their evolution within hydrothermal systems. The early stage of the hydrothermal activity has produced extensive propylitisation and potassic alteration (orthoclase, biotite, sericite) associated with the central part of the quartz-micromonzodioritic porphyry stock. The late stage of the fluids differentiation is determined by the hydrogen-ion metasomatism (phyllic alteration, argillic alteration), characterized by a large vertical variation. The hydrogen-ion metasomatism is associated with the bor metasomatism, generated by acid solutions and at a high temperature. The vertical and lateral zoning character of the hydrothermal alterations is related to differences in rock composition and variation in physical-chemical conditions during the periods of subvolcanic intrusion and mineralization.