中酸性熔岩及火山碎屑岩.ppt

中酸性熔岩及火山碎屑岩
英安岩（dacite）

2 主要种属及岩相学
安山岩（andesite）
辉石安山岩（andesite）

2 主要种属及岩相学
粗面岩（trachyte）

改造后的洋壳 掉落到地幔深部
岛弧安山岩（洋－陆 and 洋－洋 俯冲带）
ocean to ocean subduction
ocean to continent subduction
Copy right © 1984, by Tasa Graphic Arts, Inc
Copy right © 1984, by Tasa Graphic Arts, Inc
大洋中脊、板内裂谷 安山岩
Ocean - Ocean Divergence
Continent - Continent Rifting
洋中脊
转换断层
Copy right © 1984, by Tasa Graphic Arts, Inc
Copy right © 1984, by Tasa Graphic Arts, Inc
2 流纹岩的成因（与部分花岗岩成因相似）
主要产出于
与俯冲有关的岩浆弧环境
热点和洋中脊
形成环境
陆壳岩石的熔融
基性岩浆FC或AFC作用
岩石成因：大体积的酸性岩浆形成需要地壳物质参与
大陆裂谷的双峰式岩套
安山岩地壳岩石和俯冲沉积物的熔融
陆壳岩石的熔融（C. ANNEN et al.,J Petrol,2005,47(3):505-539)
：
流纹岩成因
Fig. 1. Conceptual representation of a hot zone (not to scale). Sills of mantle-derived basaltic magma are injected at a variety of depths, including
(1) the Moho, (2) the lower crust and (3) the Conrad Discontinuity between lower and upper crust. Sills injected at the Moho displace older sills
into the mantle, creating a contrast between the petrological Moho (base of sill complex) and seismological Moho (top of sill complex). Sills
crystallize from their injection temperature to that of the geotherm, resulting in a wide variety of residual melt fractions at any given time, from
near 100% (newly injected sill near Moho) to 0% (old sill injected into lower crust). The fraction of crustal melt varies throughout the hot zone
according to the age and proximity of the basalt sills. Melts ascend from the hot zone to shallow storage reservoirs, leaving behind dense refractory
cumulates or restites. Residual and crustal melts from different portions of the hot zone may be mixed together prior to ascent or within the
shallow reservoir.
由于上升的玄武岩浆的加热，导致安山岩地壳在低压下（<7mb)的重熔（Tamura & Tatsumi,2002, , 43(6): 1029-1047)，例如，Izu-Bonin大洋弧。
（2）俯冲带新形成的安山岩地壳的重熔融
注意：在下图中，早先形成于浅部的安山岩（3,5)受新侵位的玄武岩浆（9，10）加热，重熔后喷出钙碱性流纹岩。
（3）基性岩浆FC或AFC作用
岩石Rb-Sr含量与成因联系（BACHMANN AND B