17:15 〜 18:45
[SGC33-P01] Verification of the model to determine the recycling age of oceanic crust
キーワード：物質循環、FOZO、HIMU、リサイクル年代
Crustal material is inferred to be recycled back into the mantle through subduction (e.g., Hofmann and White, 1982; Zindler and Hart, 1986; Weaver, 1991; Stracke et al., 2005; Stracke et al., 2012). As the crustal materials contain high concentrations of incompatible elements, the recycling of crustal materials has a profound impact on the chemical evolution of the Earth.
One of important constrains of the recycling process should be residence time of crustal material in the mantle (recycling age) which could be shown with timescale from formation of oceanic crust at a mid-ocean ridge to remelting of the crust in an uprising plume via deepest mantle. As the oceanic crust was produced by melting of upper mantle, recycling age of oceanic crust basically identical to the model age of the oceanic crust.
Recent study revealed that source materials of FOZO and HIMU type OIB could mainly comprised of depleted MORB mantle (DMM) and recycled oceanic crust (Shimoda and Kogiso, 2019). On the basis of this notion, recycling age of oceanic crust can be determined by combining two-types of model ages. Thus, we estimated recycling age of oceanic crust by using Pb-Pb and Nd model ages. The model successfully estimate recycling age of oceanic crust of which age range was from ca. 0.9 to 2.6 Ga.
The model assumed that source area of OIB comprised of two components (DMM and recycled oceanic crust). Thus, there are two concerns about the model, i.e., the one is the effect of sediment on estimated recycling ages because there should present sediment on the top of the oceanic crust. The other concern is that the effect of primitive component on the determined ages because some researchers inferred that FOZO type OIB included primitive component in their source area. In the present study, we will evaluate effect of sediment and primitive mantle on the estimate recycling age and discuss material cycle in the Earth using estimated recycling ages.
One of important constrains of the recycling process should be residence time of crustal material in the mantle (recycling age) which could be shown with timescale from formation of oceanic crust at a mid-ocean ridge to remelting of the crust in an uprising plume via deepest mantle. As the oceanic crust was produced by melting of upper mantle, recycling age of oceanic crust basically identical to the model age of the oceanic crust.
Recent study revealed that source materials of FOZO and HIMU type OIB could mainly comprised of depleted MORB mantle (DMM) and recycled oceanic crust (Shimoda and Kogiso, 2019). On the basis of this notion, recycling age of oceanic crust can be determined by combining two-types of model ages. Thus, we estimated recycling age of oceanic crust by using Pb-Pb and Nd model ages. The model successfully estimate recycling age of oceanic crust of which age range was from ca. 0.9 to 2.6 Ga.
The model assumed that source area of OIB comprised of two components (DMM and recycled oceanic crust). Thus, there are two concerns about the model, i.e., the one is the effect of sediment on estimated recycling ages because there should present sediment on the top of the oceanic crust. The other concern is that the effect of primitive component on the determined ages because some researchers inferred that FOZO type OIB included primitive component in their source area. In the present study, we will evaluate effect of sediment and primitive mantle on the estimate recycling age and discuss material cycle in the Earth using estimated recycling ages.