摘要
俯冲带除俯冲板片脱水形成的富大离子亲石元素流体、交代地幔楔形成的岛弧钙碱性玄武岩 安山岩 英安岩 流纹岩及相应侵入岩组合外,还存在由俯冲板片熔融形成的埃达克质熔体交代地幔楔形成的埃达克岩 富铌玄武岩 富镁安山岩组合,从而构成了俯冲带的流体交代与熔体交代两大类壳幔相互作用体系及相应的岩石组合。熔体交代作用的显著特点是Mg、高场强元素Nb、Ti、P等含量增加,Nd Sr值增高,而Si、K、Na及La Yb降低。洋壳板片或洋脊俯冲、玄武质岩浆底侵使地壳增厚,或板片断离、撕裂等作用均可产生埃达克质熔体并随之产生熔体交代作用。流体和熔体与地幔橄榄岩的相互作用构成了俯冲带复杂的地球化学体系。
Besides the interaction of fluid derived from the dehydration of subducted slab with the mantle wedge peridotites, the interaction of slab-derived melt with overlying mantle has also been found in the subduction zone. The adakites and associated Nb-enriched basalts and magnesian andesites are the products of interaction of slab-derived melt with mantle peridotites. The interaction of adakitic slab-derived melt with mantle wedge leads to increase of Mg,Nb,Ti,P and Nd/Sr,and decrease of Si,K,Na and La/Yb. Three models have been proposed for the slab melting: 1,subduction of young oceanic slab or oceanic ridge;2,underplating of basaltic magma in lower cruts;3, breaking off or tearing of subducted slab.
出处
《矿物岩石地球化学通报》
CAS
CSCD
2004年第4期277-284,共8页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
国家自然科学基金项目(40373017)
国家重点基础研究发展规划项目(2001CB409803)资助
