Yin and yang of continental crust creation and destruction by plate tectonic processes

摘要

Earth's continental crust today is both created and destroyed by plate tectonic processes, a balance that is encapsulated by the traditional Chinese concept of yin-yang, whereby dualities act in concert as weli as in opposition. Yin-yang conceptualizations of crustal growth and destruction are mostly related to plate tectonics;;both occur mostly at subduction zones, by arc magmatic creation and by subduction removal. Crust is also created and destroyed by processes unrelated to plate tectonics, including losses by lower crust foundering and additions at hotspots. At present, creation and destruction of continental crust is either in balance (～3.2 km~3/year, or 3.2 AU) or more crust is being destroyed than created;;the uncertainty comes from unknown deep losses of continental crust at collision zones and due to lower crustal foundering. The yin-yang creation-destruction balance changes over a supercontinent cycle, with crustal growth being greatest during supercontinent break-up due to high magmatic flux at new arcs and crustal destruction being greatest during supercontinent amalgamation due to subduction of continental material and increased sediment flux due to orogenic uplift. These conclusions challenge the widely held view that continental crust volume has increased over time due to plate tectonic activity;;it is just as likely that this volume has decreased.