Physics and Chemistry of Deep Continental Crust Recycling

Continental crust formation at arcs, the arclogite “delamination” cycle, and one origin for fertile melting anomalies in the mantle

“…2b). Given a continuous background magmatic flux imparted by subduction-induced decompression melting in the mantle wedge [53], the garnet pyroxenite layer thickens gradually with time [4,18,54]. Due to the high densities of the garnet pyroxenite cumulates compared to typical peridotitic mantle ( Fig.…”

“…If delamination is a general phenomenon, it should be an important means of recycling lower crust or lithospheric mantle back into the Earth's interior, and hence should have an important influence on the compositional evolution of continental crust and the introduction of compositional heterogeneities into the mantle [5,9,14]. For example, it has been hypothesized that the felsic composition of continental crust may be the result of preferential removal of mafic lower crust by delamination [4,9,11,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. It has also been hypothesized that this delaminated mafic reservoir may partly contribute to the source regions of midplate and ridge magmas [26,31].…”

“…Delamination (used loosely here to describe any foundering or detachment) of lower crust or lithospheric mantle due to compositionally or thermally induced densifications has been suggested to explain a number of geologic observations, such as short-lived uplifts, high heat flow and magmatism, and unusual seismic anomalies [1][2][3][4][5][6][7][8][9][10][11][12]. Such features as uplift and high heat flow are the predicted consequences of having hot asthenospheric mantle upwell passively to replace the ''void'' created by removal of the deep lithosphere or lower crust.…”

Origin of the late Early Cretaceous granodiorite and associated dioritic dikes in the Hongqilafu pluton, northwestern Tibetan Plateau: A case for crust–mantle interaction

“…As an inevitable process during crust accretion-related magmatism, crust-mantle interaction has been the subject of much research. Models have been proposed to characterize crust-mantle interaction such as "underplating", "delamination", "convective removal", "tectonic erosion" (Bergantz, 1989;Clift et al, 2009;Conrad and Molnar, 1997;Kay and Kay, 1993;Lee, 2012;Lee and Anderson, 2015). All these are probable processes, but details of these processes need better understanding.…”

High-Mg adakitic rocks and their complementary cumulates formed by crystal fractionation of hydrous mafic magmas in a continental crustal magma chamber

“…A recently statistical treatment (Chiaradia, 2015) of geochemical data on magmatic rocks from Pliocene-Quaternary arcs around the Earth also suggests that intra-crustal fractionation of mafic magmas is the main parameter controlling the development of adakitic signatures of igneous rocks. If so, there should be abundant complementary cumulates/residues of these adakitic rocks and these might play a significant role in the formation and differentiation of the continental crust (Lee, 2014;Lee et al, 2007;Müntener et al, 2001). However, such cumulate rocks have rarely been observed in nature, either because they may be located deep in the crust, and thus are inaccessible, or they may have delaminated into the mantle.…”