METALLOGENESIS FOR THE BOLÉO AND CANANEA COPPER MINING DISTRICTS: A CONTRIBUTION TO THE UNDERSTANDING OF COPPER ORE DEPOSITS IN NORTHWESTERN MÉXICO

摘要

Northwestern Mexico is characterized by different metallogenic provinces that are included along the Basin and Range, the Sierra Madre Occidental, and the Baja California geological provinces. With the purpose of contribute to the current understanding of the mineralizing processes, the present study focused on two important copper metallogenic provinces: the Cananea Porphyry District in Sonora, and the Sediment-hosted Stratiform Copper- and Mn-deposits in Baja California Sur. The U-Pb zircon ages from the mineralizing porphyries from Cananea district suggest a continued magmatic activity period of ~6 Ma. Also suggests a period of ~20 Ma for the entire magmatic activity in the district. The Re-Os molybdenite ages demonstrate five well-constrained mineralization events in the district; the main mineralization is constrained over a short period of time (~4 Ma). The new molybdenite age from the Pilar deposit documents the oldest mineralizing pulse, suggesting possibly the initiation of the Laramide mineralization in northern Sonora. A detailed study of Mariquita porphyry Cu and Lucy Cu-Mo deposits in the Cananea district was performed. Four hydrothermal stages were defined in Mariquita, whereas a single hydrothermal pulse characterizes Lucy. Emplacement depths between 1-1.2 km, and temperatures between 430-380ºC characterized the mineralization from Mariquita, whereas deeper emplacement depths and higher mineralization temperatures characterized Lucy. The stable isotope systematic and fluid inclusion data determined that the mineralizing fluids in Mariquita deposit are essentially magmatic during the earlier hydrothermal stages, whereas the last stage is the mixing between magmatic and winter meteoric-waters. The mineralizing fluids from Lucy deposit are magmatic in origin. A comprehensive study was performed in the Cu-Co-Zn-Mn ineralization of the Boléo District, and Mn-oxide mineralization along the eastern coast Baja California Sur. The REE and trace element in the Mn-oxides demonstrated the exhalative nature of the mineralizing hydrothermal fluids, and exclude the hydrogenous nature. The stable isotope systematic in ore and gangue minerals, along with the Cu-isotope data helped to decipher the nature of mineralizing and non-mineralizing fluids. The application of Pb, Sr and Re-Os isotope systems was applied to constrain the nature of the fluids involved during the mineralization processes and that the metal sources.