太行山北段浮图峪矿田石榴子石环带特征研究

位于华北克拉通中部太行山北段的浮图峪矿田由七个中小型矽卡岩型铜铁矿床和木吉村大型斑岩铜(钼)矿组成。石榴子石是浮图峪矿田矽卡岩型矿床的主要矿物,与矿化关系密切,是展开浮图峪矿田成因研究的一个重要切入点。本文对其中四个典型矽卡岩型矿床中与矿化密切相关的石榴子石进行野外地质调研、岩相学特征研究,运用电子探针分析石榴子石环带的化学成分。研究结果表明,石榴子石成分属钙铁-钙铝榴石系列;从晶体核部到边缘,钙铁榴石与钙铝榴石呈韵律式变化,总体上钙铁榴石组分的质量分数(78.1%~86.2%)大于钙铝榴石(12.91%~16.61%)。根据石榴子石的环带结构及其成分特征,认为石榴子石是在弱酸、较低温度和相对氧化的环境中生成的,指示成岩成矿流体温度、pH、氧逸度和盐度均在不断地发生变化,说明石榴子石不是在一个完全封闭的平衡条件形成的,暗示流体的多期多阶段性,这是矽卡岩型矿床富集金属的前提条件和重要因素。

The Zoning Characteristic of Garnets in the Futuyu Orefield of the Northern Taihang Mountain

The Futuyu orefield is composed of seven small-middle skarn Cu-Fe deposits and Mujicun porphyry Cu-Mo deposit in the northern Taihang Mountain within the Central area of the North China Craton. Garnet is the main mineral of the skarn deposits in the Futuyu orefield, which is closely related to the mineralization and the important mineral to study the genesis of the Futuyu orefield. Combined with a geological investigation and petrographic feature study, the composition of zoning garnet from four ore deposits by using electron microprobe analysis was analyzed. Garnets in this orefield were classified into Andradite-grossularite series, and from core to rim of the crystal, andradite and grossularite show a rhythmic style change. Total content of Andradite component (78.1%-86.2%) is much larger than that of Grossularite (12.91%-16.61%). According to the zoning structure and component feature of garnet, it was generated in the weak acid, low temperature and relatively oxidation environment. According to the changes of temperature, pH, oxygen fugacity and salinity of the ore-forming fluid, garnet was not formed in a completely closed balance environment and the fluid has characteristics of multi-phases and multi-periods, which is the prerequisite and important factor of the enrichment of metal in the skarn deposit.