Ph.D. Harvard, 1989
B.Sc. (Honors), Oregon State University, 1983
Dr. Macfarlane studies the processes that form metal ore deposits in the context of the geologic evolution of their regional environment. Research in Peru has centered on clarifying how Andean base and precious metal deposits form and where the ore metals come from. Radiogenic isotope studies have shown that metals in the majority of Andean deposits come mainly from associated igneous rocks. Magmatic processes thus strongly affect the metal budgets of most Andean ore systems. Stable isotope and fluid inclusion systematics have been used to study secular changes in hydrothermal fluid chemistry and temperature. Regional studies of lead isotopes have revealed four distinct lead isotopic provinces in the central Andes of Peru, eastern Bolivia, northern Argentina and Chile. These provinces appear to reflect fundamentally different magma sources in different geologic settings. With the establishment of a new mass spectrometry laboratory in the department, future research will investigate the isotopic systematics of ores and important crustal elements of the Andes, Central America and the Caribbean. These investigations constrain the ages of important geological events in the South American cordillera and the isotopic histories of basement terranes in addition to revealing the sources of elements in magmas and of metals in ores.
In parallel with studies of ore genesis and the geologic sources of ore metals, Dr. Macfarlane is conducting research into the sources of metals in pre-Colombian artifacts from the Andean Altiplano, northern Chile, southern Mexico and Ecuador. Lead isotope data on ore deposits from these regions is directly applicable to investigations of the provenance of copper and bronze artifacts, which reveal how metallurgical technology developed and spread in the Western Hemisphere.
Other research interests include studies of the geochemistry of Precambrian weathering profiles to constrain the chemistry, especially the oxygen content, of the early earth's atmosphere. Isotope geochronology and rare earth element geochemistry of these weathering profiles are used to illuminate their geologic history and the chemical environment of their formation.