Origin of geochemical mantle components: Role of subduction filter

Abstract

We quantitatively explore element redistribution at subduction zones using numerical mass balance models to evaluate the roles of the subduction zone filter in the Earth's geochemical cycle. Our models of slab residues after arc magma genesis differ from previous ones by being internally consistent with geodynamic models of modern arcs that successfully explain arc magma genesis and include element fluxes from the dehydration/melting of each underlying slab component. We assume that the mantle potential temperature

Origin of geochemical mantle components: Role of spreading ridges and thermal evolution of mantle

“… Evolution of the Earth's crust and mantle through time (bottom axis) and relative ages (top axis), revised from Kimura et al . [, Figure 7]. Differences from that previous figure are the addition of εhf (initial) data for zircons from orogenic eclogites in Figures 5a and 5d–5g.…”

“…Subduction zone processes include metamorphic dehydration and melting of the slab in addition to flux melting of the wedge mantle to form arc magmas [ Kimura et al ., ; Porter and White , ]. We have examined the fate of the processed subduction materials and the origin of enriched mantle components using a holistic numerical model in a separate paper [ Kimura et al ., ]. There we proposed that (1) post‐early‐Archean CC forms mostly from high‐Mg andesite arc magmas in hot Archean to Paleoproterozoic subduction zones and the enriched mantle components evolve from the residues of that subduction; (2) subcontinental lithospheric mantle (SCLM) derives from the residual mantle of arc magma genesis at the top of the mantle wedge; (3) the high‐µ (μ = 238 U/ 204 Pb: HIMU) mantle component derives from residual IOC; (4) the Enriched Mantle 2 (EM2) component derives from the same kind of slab component as in modern arcs (i.e., a ∼95:5 mixture of IOC:SED); and (5) the Enriched Mantle 1 (EM1) component derives from the base of the mantle wedge (MwP) that sits just above the slab during subduction.…”

“…There we proposed that (1) post‐early‐Archean CC forms mostly from high‐Mg andesite arc magmas in hot Archean to Paleoproterozoic subduction zones and the enriched mantle components evolve from the residues of that subduction; (2) subcontinental lithospheric mantle (SCLM) derives from the residual mantle of arc magma genesis at the top of the mantle wedge; (3) the high‐µ (μ = 238 U/ 204 Pb: HIMU) mantle component derives from residual IOC; (4) the Enriched Mantle 2 (EM2) component derives from the same kind of slab component as in modern arcs (i.e., a ∼95:5 mixture of IOC:SED); and (5) the Enriched Mantle 1 (EM1) component derives from the base of the mantle wedge (MwP) that sits just above the slab during subduction. The age of the enriched mantle components (3.0–1.5 Ga) correlates with the major formation period of the CC [ Dhuime et al ., ; Kimura et al ., ; Moyen and Martin , ]. Over half of these enriched components may be stored in two large low‐shear wave velocity provinces (LLSVPs) of the lowermost mantle [ Burke et al ., ; Steinberger and Torsvik , ] from which they occasionally are entrained by strong plume upwelling [ Hofmann and Farnetani , ; Li et al ., ] to form hot spot magmas of ocean island basalt (OIB) [ Hofmann , ; Kimura et al ., ].…”

“…The age of the enriched mantle components (3.0–1.5 Ga) correlates with the major formation period of the CC [ Dhuime et al ., ; Kimura et al ., ; Moyen and Martin , ]. Over half of these enriched components may be stored in two large low‐shear wave velocity provinces (LLSVPs) of the lowermost mantle [ Burke et al ., ; Steinberger and Torsvik , ] from which they occasionally are entrained by strong plume upwelling [ Hofmann and Farnetani , ; Li et al ., ] to form hot spot magmas of ocean island basalt (OIB) [ Hofmann , ; Kimura et al ., ].…”

“…Our companion paper about enriched mantle components [ Kimura et al ., ] discussed (1) the element mass balance at subduction zones using version 4 of the Arc Basalt Simulator (ABS4) numerical model, and (2) the subsequent isotopic evolution of hot subduction zone residues to form enriched mantle components. We used a combined element fractionation and isotope evolution model named ABS_OCR (Ocean Crust Recycling) version 1 (ABS_OCR1) to examine the origin of the enriched mantle.…”