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How to find volcanoes that no longer exist?

Ludmila M. Fonseca Teixeira1

Abstract

Over the last decade, the connection between silicic volcanic and plutonic rocks is therefore of great interest and has received increased attention from the scientific community. Accepting such connection prompts further questions: (1) what should silicic cumulates look like? (2) Which plutons are indeed cumulates, and which plutons should be considered "failed eruptions"? (4) Do all magma reservoirs erupt, and if not, what percentage of them do (i.e. the volcanic-plutonic ratio)? (5) Has the volcanic-plutonic ratio changed through history? Studies on the distinction between silicic volcanics and plutonics are difficult for most systems, as when plutonic rocks are exposed in the Earth's surface, volcanics are often already eroded and no longer available. My presentation offers a solution to this problem by demonstrating how volcanic/plutonic quartz and zircon can be distinguished using Ti-thermometers in detrital sediments. Using Ti distributions in the detrital record allows for separation of volcanic, plutonic, and pegmatitic crystals of quartz and zircon in a given magmatic system -- even when the volcanics have been completely eroded. This technique offers for the first time a possibility to find volcanoes that have been completely eroded, holding potential to further understand the growth and evolution the continental crust throughout Earth's history.