Zircon U–Pb and biotite 40Ar/ 39Ar geochronology from the Anzan emerald deposit in Zambia

摘要

Graphical abstractDisplay OmittedHighlights?The age of Muva Supergroup in the Copperbelt Province in Zambia is redeterminated to be greater than or equal to 1966±12Ma.?The ore bodies of Anzan emerald deposit underwent three phases of regional metamorphism at 1853±58Ma, 1344±30Ma and 578.3±2.6Ma respectively, and the emerald deposit was eventually formed at 578.3±2.6 Ma.AbstractThe Kafubu Emerald Area in Zambia is an important producer of gemstone-quality emeralds. The country rocks include carbonatization altered rock and emerald-hosting biotite chlorite schist from the Anzan emerald deposit in the Kafubu area, Zambia. The technique of LA-MC-ICP-MS is used to perform chronology measurements of the country rock and emerald-hosting rock which belong to Muva Supergroup, yielding zircon U-Pb concordia ages of 1966±12Ma in carbonatization altered rock and 1853±58Ma and 1344±30Ma in biotite chlorite schist. Meanwhile, dating of biotite chlorite schist using the biotite40Ar–39Ar method has obtained the plateau age of t=578.3±2.6Ma, isochron age of 577.5±3.0Ma and reverse isochron age of 577.4±3.0Ma. Thus, we have redefined the age of Muva Supergroup in the Copperbelt Province in Zambia to be older than or equal to 1966±12Ma, and found that the ore bodies in the Anzan emerald deposit underwent three phases of metamorphism at 1853±58Ma, 1344Ma±30 and 578.3±2.6Ma and finally accomplished the emerald mineralization. The age of the Anzan emerald deposit is earlier than the Kagem (452.1±16Ma) and the Kamakanga emerald deposits (447±8.6Ma).]]>