[SIT21-P05] The genesis of the basalt-HMA association from Nagasaki in northwest Kyushu, southwest Japan
According to results of high pressure melting experiments, HMA magmas could also be formed by partial melting of relatively anhydrous mantle at pressure lower than 0.6 GPa. Multi-stage partial melting of relatively anhydrous mantle could form HMA magmas at P<0.6 GPa and basalt magmas at P>0.6 GPa along a melting adiabat (Falloon et al., 1988). Multi-stage partial melting model could resolve the thermal problem concerning the genetic relationship between HMAs and associated basalts. In the context of multi-stage partial melting, geochemical features attributed to the subducting slab are explained with the involvement of accreted oceanic material at the base of the crust in the source mantle. It is therefore a critical issue for earth science which forms basalt-HMA associations in subduction zones, flux melting or multi-sage partial melting.
Basalt-HMA associations are distributed in northwest Kyushu, southwest Japan. Seismic observations indicate that the subducting slab does not extend there. The genesis of basalt-HMA associations in NW Kyushu gives us some insights into the debate concerning the HMA magma genesis. In this poster, I discuss the genesis of the basalt-HMA association from Nagasaki in NW Japan.