A review of the granite concept through time

Abstract

Granitic rocks are ubiquitous worldwide in ancient and active tectonic settings, representing powerful sources of information about the Earth's past and present geodynamic behaviour. Numerous recent milestones fostering our knowledge of granites would have not been possible without a long-lasting, sometimes controversial, discussion on their origin and significance that has taken place over the last two centuries. Here we present a chronological review of how granites have been defined and interpreted in the context of the major theories that have successively governed the history of Earth Science. The main authors, scientific approaches, interpretations, and type-localities that have influenced knowledge about granitic rocks are summarized from the 18th and 19th centuries, when Earth Science was governed by the Neptunism, Plutonism and Uniformitarianism paradigms, to the acceptance of the Plate Tectonics theory and the very end of the magmatism vs. transformism debate in the late 20th century. Some of the most influential scientific advances in Earth Science, such as the invention of the polarizing microscope and the birth of geochemistry, as well as the role of schools of thought in these successive debates, are further discussed. Moreover, we review the recent and ongoing discussions on the mechanisms of magma generation, segregation, ascent and emplacement leading to the formation of granitic batholiths, as well as the observational, analytical, experimental, and numerical modelling approaches currently used for investigating granitic rocks. The history of granite science is classified into different periods of stasis or “normal” science, which were followed by scientific revolutions triggered by a growing number of inconsistencies. Our current understanding of granitic rocks is inevitably influenced by the preceding paradigms and disputes. Consequently, gathering and valuing the chronology, historical milestones, and overall evolution of ideas and theories on what granites are is crucial for the future directions of granite research.