摘要
同正常的残余方辉橄榄岩相比,辉南方辉橄榄岩具有异常高的HREE组成和特殊的二次重结晶结构,因此,它们不是上地幔经大程度部分熔融后的残余,而是熔体-岩石反应的结果。倒U型REE分配模式暗示这些样品经历了与玄武质熔体相互作用的历史,并达到了平衡。大量熔(流)体的存在有利于地幔岩石矿物颗粒的增长,从而形成特征的二次重结晶结构。这种“反应”型方辉橄榄岩的形成可能与上涌软流圈对岩石圈地幔的热-化学侵蚀有关。“反应型”方辉橄榄岩形成之后,又受到了类似于碳酸岩或富挥发份小体积熔体的交代。因此辉南地区上地幔经历了多期地幔交代作用。
The harzburgites from Huinan are not residues of partial melting of large degree in the mantle, because they have anomalously high HREE abundance and peculiar secondarily recrystallized texture, when compared to the normal residual harzburgites. Instead, they likely resulted from melt-mantle reaction through clinopyroxene dissolution and olivine precipitation. The convex-upward REE pattern suggests that these samples were in equilibrium with melts with basaltic composition at high melt/rock ratio. The presence of melts/fluids enhanced the grain growth in peridotites, giving rise to the formation of secondarily recrystallized texture, typical of the Huinan harzburgites, The formation of the Huinan harzburgites was probably related to thermo-chemical erosion of the lithosphere mantle by upwelling asthenosphere. These 'reactive' harzburgites were further affected by metasomatism involving carbonate or volatile-rich small volume silicate melts.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2003年第1期19-26,共8页
Acta Petrologica Sinica
基金
国家自然科学基金(编号:49925308
49703042)项目
国家科技部攀登项目(95预选-39)资助成果
