Por Martim Chichorro (Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa).
Abstract: Zircon exhibits a remarkable “geologic” memory. However, Zircons also reveal a Hidden Side. Significant details in their zonation patterns can help us interpret multistage growth periods and complex crustal histories. Each in-situ zircon single analysis must be examined with accuracy in order to control the boundaries representative of the zircon forming and altering events, the presence of thermal-activated recrystallization, detect analytical superposition of zircons growths, the influence of inclusions, fractures and defects. The presentation will focus on some contrasting geometric and chemical characteristics of Zircon that allow us to read the pre-Variscan and Variscan cycles related to the building of the Iberia crust. Special attention will be paid to Zircon inheritance, some CL examples, the advantages and the difficulties related to their interpretation. New insights into the comprehension of the Cambrian-to-Ordovician rift-to-drift processes are revisited and an examination is explored taking in account the zircon inheritance. Finally, a key question will be further discussed: - are the Rift-to-Drift tectono-magmatic events a clue for Iberian Terrane individualization?
