川西南雷波安寨坪地区萤石矿成因分析：稀土元素地球化学及流体包裹体的制约
Genetic analysis of fluorite deposit in Anzhaiping area, Leibo County, southwest Sichuan: insights from rare earth element geochemistry and fluid inclusion
-
摘要: 川西南雷波安寨坪地区萤石矿赋存于下寒武统筇竹寺组碎屑岩内，成矿严格受区域近南北向峨边-金阳断裂带控制，矿体以脉状充填式产于构造裂隙中。基于研究区萤石矿的地质调查成果，对萤石矿开展了稀土元素地球化学、流体包裹体研究，探讨了该区萤石矿成矿流体性质、成矿过程及成矿模式。结果表明：萤石稀土元素总含量普遍较低，稀土元素配分模式呈略微右倾、中稀土富集的上凸型特征，普遍具较强Eu正异常（δEu均值1.77）和弱Ce负异常（δCe均值0.83），结合Tb/Ca-Tb/La及Y/Ho-La/Ho图解，认为研究区萤石矿为热液成因，矿床类型为热卤水型，成矿流体来源于同一流体体系，且成矿环境是高氧逸度的开放体系。流体包裹体类型主要为富液相的气液两相包裹体，均一温度范围为80.6~209.1℃，盐度范围为2.1%~21.4%NaCleqv，反映成矿流体属中-低温、低盐度的NaCl-H2O体系。成矿热液流体与围岩发生水-岩反应主要是促使成矿元素F、Ca聚集，而萤石沉淀机制主要为深部卤水、大气降水发生流体混溶和流体降温冷却。盆地热卤水及大气降水萃取地层中Ca、F等成矿元素后，使成矿元素在成矿热液系统中富集，构造和地层压力梯度致使成矿热液沿断裂带向上运移至有利的容矿裂隙中，受下寒武统筇竹寺组细粒碎屑岩封闭盖层的遮挡，随成矿环境条件发生变化沉淀富集形成脉状萤石矿，成矿类型为中低温热液裂隙充填型萤石矿。Abstract: The fluorite deposit exists in the clastic rocks of the Lower Cambrian Qiongzhusi Formation in the Anzhaiping area of Leibo County, southwest Sichuan Province. The mineralization of fluorite is controlled by the Ebian-Jinyang Fault, which is in the near north-south trend, and occurs in the structural fissure in the form of veins. Based on the geological survey results of the fluorite, research was conducted on the rare earth element and fluid inclusions, and discussed the ore-forming fluid, mineralization process and metallogenic model of the fluorite. The results show indicate that the very low total content of rare earth elements, convex feature of the slightly right-leaning pattern of rare earth elements and moderately rare earth enrichment, and with positive Eu anomaly (δEu mean 1.77) and negative Ce anomaly (δCe mean 0.83). Further combined with the Tb/Ca-Tb/La and Y/Ho-La/Ho diagrams, it is considered that the fluorite is of hydrothermal origin and hot brine type. The ore-forming fluid originates from the same fluid system with a high oxygen fugacity and open system environment for the ore-forming processes. The types of fluid inclusions are mainly liquid-rich biphase inclusions with homogenization temperature of 80.6~209.1℃ and salinity of 2.1%~21.4%NaCleqv, which reflecting the ore-forming fluid belongs to the medium-low temperature and low salinity NaCl-H2O system. The water-rock reaction between ore-forming hydrothermal fluid and surrounding rock is mainly to promote the accumulation of ore-forming elements F and Ca, while the mechanism of precipitation is the fluid miscible and fluid cooling of formation brine and meteoric water. The hot brine and meteoric water extracted the Ca and F ore-forming elements from the strata and enriched them in the ore-forming hydrothermal system. The tectonic and stratigraphic pressure gradient caused the ore-forming hydrothermal fluid to migrate to the favorable ore-bearing fissure along the fault, which was blocked by the closed cover of the fine grained clastic rocks of the Lower Cambrian Qiongzhusi formation and precipitated with the change of ore-forming environmental conditions to form a vein fluorite deposit. The ore-forming type belongs to the medium to low temperature hydrothermal fissure filling type fluorite deposit.
-
Keywords:
- fluorite deposit /
- rare earth elements /
- fluid inclusions /
- metallogenic model /
- Leibo area
-
计量
- 文章访问数: 124
- HTML全文浏览量: 0
- PDF下载量: 21
下载:
