Mineral distribution within polymineralic veins in the Sanbagawa belt, Japan: implications for mass transfer during vein formation
Mineral distribution within polymineralic veins in the Sanbagawa belt, Japan: implications for mass transfer during vein formation
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DOI：
10.1007/s00410-008-0288-y
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发表时间：
2008-09-01
影响因子：
3.5
通讯作者：
Tsuchiya, Noriyoshi
中科院分区：
文献类型：
--
作者：
Okamoto, Atsushi;Kikuchi, Taketo;Tsuchiya, Noriyoshi
三巴川变质带泥质片岩中含有多种多矿化矿脉，形成于折返晚期。脉状矿物组合为石英+钠长石+钾长石+绿泥石+/-方解石(I、II类)和石英+钠长石+方解石(III类)。I型矿脉和II型矿脉分别含有石英和钠长石，它们分别具有伸展晶体和细长块状结构。I型脉中的矿物种类随寄主岩石中的成分带而变化。III型脉具正面体-亚面体石英颗粒特征，同心分带，沿脉长分布均匀。在多次裂缝封闭事件中，矿脉纹理因裂缝孔径的不同而不同：I型为0.08 mm，III型为0.5-10 mm。II型矿脉在矿物分布(弱依赖于围岩成分)和表观裂缝孔径(小于1-15 mm)方面显示出介于I型和III型矿脉之间的特征。这些观察结果表明，随着裂隙开度的增加，脉组分的主要输运机制发生了转变，从宿主岩石的扩散转变为沿裂隙的流体平流。
Pelitic schists of the Sanbagawa metamorphic belt contain several types of polymineralic veins that formed during the late stages of exhumation. The vein mineral assemblages are quartz + albite + K-feldspar + chlorite +/- calcite (Type I, II) and quartz + albite + calcite (Type III). Type I and II veins contain quartz and albite with stretched-crystal and elongate-blocky textures, respectively. The mineral species within Type I veins vary with compositional bands within the host rocks. Type III veins are characterized by euhedral to subhedral quartz grains with concentric zoning and a homogeneous distribution along the vein length. The vein textures vary depending on the crack aperture during multiple crack-seal events: < 0.08 mm for Type I, and 0.5-10 mm for Type III. Type II veins show intermediate features between Type I and III veins in terms of mineral distribution (weak dependence on the host rock composition) and apparent crack aperture (less than 1-15 mm). These observations suggest a transition in the dominant transport mechanism of vein components with increasing crack aperture, from diffusion from host rocks to fluid advection along cracks.