Mineralogical and textural variation of silica minerals in hydrothermal flow-through experiments: Implications for quartz vein formation
Mineralogical and textural variation of silica minerals in hydrothermal flow-through experiments: Implications for quartz vein formation
复制标题
热液流通实验中二氧化硅矿物的矿物学和结构变化：对石英脉形成的影响
DOI：
10.1016/j.gca.2010.03.031
复制
发表时间：
2010
影响因子：
5
通讯作者：
N. Tsuchiya
中科院分区：
文献类型：
--
作者：
A. Okamoto;H. Saishu;N. Hirano;N. Tsuchiya
我们在430℃和31 Mpa条件下进行了水热贯通实验，研究了地壳条件下花岗岩上二氧化硅的析出机理。用不同的输入溶液进行了两个实验：单组分硅溶液和含有少量Al、Na和K的多组分溶液。石英的过饱和度Ω=Csi/Csi，Qtz，eq，其中Csi和Csi，Qtz，eq分别表示溶液中的硅浓度和石英在水中的溶解度。实验过程中形成了多种二氧化硅矿物(蛋白石-A、蛋白石-C、玉髓和石英)，它们的赋存状态和模式丰度随着Ω和溶液中添加剂的存在而变化。对于近平衡溶液(Ω<；∼1.2)，在两个实验中，二氧化硅沉淀以一种简单的方式发生，仅限于花岗岩中先前存在的石英表面的过度生长。在较高饱和度时(Ω>；∼1.2)，除石英外，其他表面还沉积了二氧化硅矿物。在单组分实验中，主要的二氧化硅矿物顺序为蛋白石-A→-蛋白石-C-→石英，随着流道中硅浓度的降低而变化。相比之下，在多组分实验中，石英和少量玉髓在整个反应容器中形成。这一发现表明，溶液中的杂质(Na、K和Al)抑制了蛋白石的析出，促进了石英的直接成核。通过成核过程和宏观沉淀动力学考察了亚稳态二氧化硅矿物的系统形貌。我们的实验结果表明，不同的沉淀机制产生了不同的纹理，这反过来又表明，静脉纹理可以作为裂缝内溶液化学的指示器。
We conducted hydrothermal flow-through experiments at 430°C and 31MPa to investigate the mechanism of silica precipitation on granite under crustal conditions. Two experiments were performed using different input solutions: a single-component Si solution, and a multi-component solution with minor Al, Na, and K. The degree of supersaturation with respect to quartz, Ω=CSi/CSi,Qtz,eq, where CSiand CSi,Qtz,eqindicate Si concentration in solutions and the solubility of quartz within water, respectively, decreased from 3–3.5 to <1.1 along the flow path. A variety of silica minerals formed during the experiments (opal-A, opal-C, chalcedony, and quartz), and their occurrences and modal abundances changed in response to Ω and the presence of additives in the solution. For near-equilibrium solutions (Ω<∼1.2), silica precipitation occurred in a simple way in both experiments, being restricted to overgrowths on pre-existing quartz surfaces in the granite. At higher saturation levels (Ω>∼1.2), silica minerals were deposited on other surfaces in addition to quartz. In the single-component experiment, the dominant silica minerals changed in the order of opal-A→opal-C→quartz with decreasing Si concentration along the flow path. In contrast, in the multi-component experiment, quartz and minor chalcedony formed throughout the entire reaction vessel. This finding indicates that impurities (Na, K, and Al) in the solutions inhibited the precipitation of opal and enhanced the direct nucleation of quartz. The systematic appearance of metastable silica minerals were examined by nucleation processes and macroscopic precipitation kinetics. Our experimental results indicate that different precipitation mechanisms yield contrasting textures, which in turn suggests that vein textures can be used as indicators of solution chemistry within the fracture.
影响因子：
3.5
作者：
Okamoto, Atsushi;Kikuchi, Taketo;Tsuchiya, Noriyoshi
通讯作者：
Tsuchiya, Noriyoshi