陕西商洛青岗、玉石坡萤石矿稀土元素特征及找矿方向

Characteristics of rare earth elements and prospecting direction of the Qinggang and Yushipo fluorite deposits in Shangluo, Shaanxi Province

摘要:

为查明萤石矿的成因类型和成矿作用，研究选取陕西省商洛市西部的青岗萤石矿和玉石坡萤石矿，矿体分别赋存于曹坪岩体和沙河湾岩体中，达中型规模，受断裂构造控制。对赋矿花岗岩及萤石开展稀土元素地球化学研究，探究成矿过程，为矿区深边部和外围找矿突破提供依据。研究表明，研究区内至少存在两个成矿期次，赋矿岩浆岩可能为氟元素的主要来源。研究区萤石及赋矿花岗岩稀土元素均表现出LREE相对富集、HREE相对亏损特征，萤石LREE/HREE值介于1.88~10.70，δEu值范围为1.08~1.61（除一件为0.86外），δCe值范围为0.68~0.95。萤石矿形成环境为弱氧化环境，稀土元素及Fe、Cr等杂质含量变化是矿区内萤石致色变色的主要因素。因此，研究区萤石矿成因类型应为中低温热液型矿床，印支期后的构造热液活动是矿区主要的成矿作用。青岗萤石矿、玉石坡萤石矿沿走向和倾向还有继续扩大找矿的潜力，应加强地质工作，以期探获更大资源量。

Abstract:

In order to identify the genetic types and mineralization of fluorite deposits, the Qinggang fluorite deposit and Yushipo fluorite deposit in the western part of Shangluo City, Shaanxi Province were selected for research. The ore bodies are located in the Caoping rock mass and Shahewan rock mass respectively, reaching a medium-sized scale and controlled by faults. This work conducted REE geochemical studies to explore the metallogenic process and provide a basis for prospecting breakthroughs in the mining area. The results show that at least two mineralization periods can be identified, and the ore-bearing magmatic rocks may be the main source of fluorine elements. The fluorite and ore-bearing granite in the study area exhibit a relative enrichment in light rare earth elements (LREE), and a relative depletion in heavy rare earth elements (HREE). The LREE/HREE values of fluorite range from 1.88 to 10.70, with a δEu value of 1.08 to 1.61 (except for one sample, 0.86), and a δCe value of 0.68 to 0.95. The formation environment of fluorite ores is a weak oxidation environment, and changes in the content of rare earth elements and impurities such as Fe and Cr are the main factors causing color change of fluorite in the mining area. Therefore, the genetic type of fluorite deposits in the study area should be of medium to low temperature hydrothermal type, and the tectonic hydrothermal activity after the Indosinian period is the main mineralization process in the mining area. There is still potential for further exploration along the strike and dip of the Qinggang fluorite and Yushipo fluorite deposits. Geological work should be strengthened for exploring greater resources.