尚义葛令夭高铬花岗岩(Closepet-like)——新太古代古缝合带的新证据

在华北克拉通北部,太古代麻粒岩古陆核与陆外沉积盆地(红旗营子群)之间已经厘定出一个晚太古代的古洋壳残片(Wang et al., 2009)。此残片南北两侧又发现了低Al₂O₃ 型TTG岩体(2512±19Ma)、富钾高铬的深熔花岗岩(Closepet-like),含Cr 97×10^-6~308×10^-6,以及含大量密集的煌斑岩脉的含石英的二长岩(Sanukitoid-like)等三类在成因上与俯冲带密切相关的岩体。低Al₂O₃型TTG是在角闪麻粒岩亚相条件下由俯冲中的滑片部分熔融所生成。深熔花岗岩是TTG再熔融的产物,而它们的基性化演化和Cr的增高是幔源岩浆与富钾深熔花岗岩经复杂的岩浆混合和交代改造的结果。

Gelingyao high-Cr granite (Closepet-like) in Shangyi: New evidence of Late-Archean suture zone

At northern of North China Craton, between Archean granulite nucleus and extra-continental sedimentary basin (hongqiyingzi Group), a Neoachaean ancient oceanic crust relict has been recognized (Wang et al., 2009). The low Al₂O₃ TTG rocks (2512±19Ma), the anatectic granites (Closepet-like) with rich K and high Cr (97×10^-6~308×10^-6), and quartz monzonites (Sanukitoid-like) with a large number of lamprophyre dykes have been discovered on both sides of the relict, they are closely related to subduction. The low Al₂O₃ TTG rocks were generated by partial melting of subducting slab under an amphibole-granulite subfacies condition. Anatectic granites were products of remelting of the TTG rocks and their basic development with increase in Cr were the results of complex mixed and metasomatism between mantle-derived magma and K-enriched anatectic granites.