“老挝石”和寿山都成坑石的“水线”特征对比及成因探讨

Characteristic and Genesis of “Water Line” in “Laos Stone” and “Shoushan Ducheng Pit Stone”

"水线"是寿山都成坑石和特定"老挝石"品种中的典型外观特征。通过肉眼观察、宝石显微镜、偏光显微镜观察、X射线粉末衍射仪、扫描电子显微镜、X射线荧光能谱仪等测试方法对"老挝石"样品和寿山都成坑石样品中"水线"的结构与成分特征进行了研究与对比。结果表明,"老挝石"中"水线"由近平行于"水线"延伸方向紧密堆积的片状地开石颗粒层和无定向排列的地开石颗粒层(其中混有网脉状硫磷铝锶矿)交替形成;寿山都成坑石中"水线"与基质部分的分界清晰,分界处矿物颗粒大小和致密程度变化不明显,"水线"内部不规则排列的地开石颗粒间混有细密的丝缕状硫磷铝锶矿。"老挝石"中"水线"的成因可能与成矿流体的多期活动以及所含矿物组成差异有关,寿山都成坑石"水线"的成因可能与成矿流体分期次的结晶以及所含矿物组成差异有关。

The "water line" inclusion is a typical appearance characteristic of "Laos stone" and "Shoushan Ducheng pit stone". The authors used macroscopic observation, gem microscope, polarizing microscope, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray fluorescence spectrometer (EDS) to study the structure characteristics and chemical compositions of "water line" in "Laos stone" and "Shoushan Ducheng pit stone". The results showed that the mineral particles are larger in some layers of "water line" in "Laos stone" and have clear orientation, all of which are close packing flaky particles arranged in the direction paralleling to the "water line". Densely distributed dickite granules and the vein-like svanbergite compose the other layers of "water line" in "Laos stone". The "water line" and the substrate part of the "Shoushan Ducheng pit stone" define clearly. The size and density of the mineral particles between "water line" and substrate in "Shoushan Ducheng pit stone" do not change obviously. The finer silky svanbergite mixed between dickite particles compose the "water line" in "Shoushan Ducheng pit stone". The cause of the "water line" in "Laos stone" may relate to the multi-phase activities of ore-forming fluids and the differences in mineral composition. The cause of the "water line" in "Shoushan Ducheng pit stone" may relate to the different-period crystallization of ore-forming fluids and the differences in mineral composition.