Formation of giant iron oxide-copper-gold deposits by superimposed episodic hydrothermal pulses.

Iron oxide-copper-gold (IOCG) deposits are a globally important source of copper, gold and critical commodities. Despite their relevance, IOCG deposits remain an ill-defined clan, with a range of characteristics that has complicated development of the general genetic model. Here we focus on the Candelaria IOCG deposit in Chile and reveal that by using micro-textural and compositional variations in actinolite, a common alteration mineral found in many IOCG deposits, we can constrain the evolution of these systems.

Dissecting the Re-Os molybdenite geochronometer.

Rhenium and osmium isotopes have been used for decades to date the formation of molybdenite (MoS), a common mineral in ore deposits and the world's main source of molybdenum and rhenium. Understanding the distribution of parent Re and radiogenic daughter Os isotopes in molybdenite is critical in interpreting isotopic measurements because it can compromise the accurate determination and interpretation of mineralization ages. In order to resolve the controls on the distribution of these elements, chemical and isotope mapping of MoS grains from representative porphyry copper-molybdenum deposits were performed using electron microprobe and nano-scale secondary ion mass spectrometry.