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

Abstract

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 well 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 yinyang 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.

Geodynamic evolution of Upper Cretaceous Zagros ophiolites: formation of oceanic lithosphere above a nascent subduction zone

“…Because the mantle beneath modern fore-arcs is cold and rarely melts, this catastrophic melting must have occurred under very special conditions, most likely when subduction began. A much larger volume of magma is produced when a subduction zone first forms than for mature arcs (Stern & Scholl, 2010). Such voluminous melt generation mostly yields abundant tholeiite magma and harzburgitic residual mantle, sometimes along with boninite.…”

Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

“…However, more recent (Paleozoic) tectonic growth of continents is believed to be from felsic island arcs or modified post-accretion oceanic plateaus (Clift et al, 2009b, a;Stern and Scholl, 2010).) There is observational evidence for modern day subduction of oceanic plateaus and submarine ridges: the Hikurangi oceanic plateau subducting seemingly intact to approximately 65 km depth under New Zealand (Reyners et al, 2006), the Ontong Java Plateau subducting under the Solomon Islands (Mann and Taira, 2004), and the Nazca Ridge under Peru (Hampel et al, 2004).…”

“…Island arcs are the most widely intuited contributor of continental crustal growth (Stern and Scholl, 2010), primarily because the crustal composition is believed to be most similar to the felsic continental crust. Using volume estimates from Condie and Kröner (2013), we project about 13 % of post-Archean accreted terranes are oceanic island arcs and 55 % are continental arcs.…”

“…Terrane accretion is considered to be one of the main contributors to the growth of continental crust (Stern and Scholl, 2010;Clift et al, 2009b;Cawood et al, 2009). Although continental crust is lost by erosion and/or recycled into the mantle at subduction zones, crust is also added to continents at subduction zones by accretion and magmatic events.…”

“…Accreted terranes can be made of tectonically added crustal units of volcanic arcs, oceanic plateaus, continental fragments, seamounts, accretionary prisms, melanges, ophiolites, and flysch. The tectonic accretion of volcanic arcs, oceanic plateaus, and seamounts to continents adds mafic juvenile crust that eventually will mature into felsic compositional continental crust by progressive magmatism and lower crustal foundering (Stern and Scholl, 2010).…”