湖南香花铺钨矿床含钙矿物的稀土元素地球化学

香花铺矿床是湘南地区唯一的萤石-白钨矿型矿床。本文利用高精度LA-ICP-MS对该矿白钨矿和方解石中的稀土元素进行了原位分析。结果表明,该矿的白钨矿表现为LREE富集和正Eu异常特征,方解石则具有LREE富集型和相对平坦型两种稀土配分模式,且均呈现负Eu异常特征。该矿属于与岩浆活动有关的热液矿床,成矿流体在还原环境下的运移过程中,首先结晶出白钨矿和LREE富集型方解石,而后沉淀形成了具有相对平坦型REE模式的方解石。此外,稀土元素在该区矿物中的分布存在明显的不均一现象,在不同微区REE的含量、配分模式以及分异程度等均可能存在差异,其原因除了结晶过程中水动力学条件的变化,还可能与矿物结晶后颗粒外表层受流体作用的改造有关。

Rare-earth element geochemistry in Ca-bearing minerals from the Xianghuapu tungsten deposit, Hunan Province, China

The Xianghuapu tungsten deposit is the rare fluorite-scheelite-type deposit in southern Hunan. In the present contribution, rare earth elements in-situ analyses are performed by LA-ICP-MS on scheelite and calcite samples collected from the Xianghuapu deposit. It reveals that the chondrite-normalized REE pattern of scheelites is LREE-enriched with positive Eu anomaly, whereas calcite samples are characterized by a flat or LREE-enriched pattern and a strong negative Eu anomaly. The studies show that the Xianghuapu deposit is related to magmatic activity in origin, and the ore-forming fluid is transported under reducing conditions, after the crystallization of LREE-rich calcite and scheelite, calcite with flat-type REE patterns were subsequently precipitated. Moreover, the inhomogeneity distribution of REE in scheelite and calcite suggests that there is a various hydrodynamic environment during mineral crystallization. On the other hand, the inhomogeneity may also be affected by later fluid which pollutes the crystal face of some mineral grains.