西藏知不拉矽卡岩铜多金属矿床石榴子石热红外光谱特征及其找矿指示意义

Thermal Infrared Spectral Characteristics of Garnet in the Zhibula Cu Skarn Deposit,Xizang,and Their Implications for Mineral Exploration

近年来,蚀变矿物的光谱和原位成分特征已成为找矿勘查的重要指标之一,如石榴子石的热红外光谱与矽卡岩矿床的Cu富集有关,但对于石榴子石的热红外光谱、颜色及其与成分的关系还不清楚。位于西藏冈底斯成矿带的知不拉矽卡岩铜多金属矿床普遍发育不同颜色的石榴子石,是探讨热红外光谱特征及其找矿指示意义的理想对象。本文对该矿区石榴子石开展了热红外光谱分析、颜色定量分析、能谱分析和X射线荧光光谱仪分析。结果显示,石榴子石端元成分以钙铁-钙铝榴石为主,石榴子石发育3种颜色,为褐红色、黄绿色和绿色,色相值范围为49~106。Fe、Al含量的变化是引起石榴子石热红外光谱主吸收谷位置移动(11200~11600 nm)的最主要因素,石榴子石主吸收谷波长与Fe含量呈正相关关系,与Al含量呈负相关关系。研究表明,石榴子石热红外光谱主吸收谷波长大于11500 nm可以作为知不拉铜矿化的热红外光谱勘查标识。

In recent years,the spectrum and in situ characteristics of altered minerals have become important indicators for mineral exploration.The thermal infrared spectrum of garnet is related to the enrichment of Cu in skarn deposits.There is relatively little research on thermal infrared spectroscopy,color,and its relationship with the composition of garnet.Garnet of different colors is widely developed in the Zhibula Cu Deposit,Gangdese belt,Xizang,and is an ideal object for discussing the thermal infrared spectral characteristics and their prospecting significance.In this study,thermal infrared spectrum analysis,color quantitative analysis,energy spectrum analysis,and X-ray fluorescence spectrometry analysis of garnet from this deposit were carried out.The results show that the garnet of the Zhibula deposit belongs to the andradite-grossularite solid solution series.The garnet develops four colors;andradite is maroon,chartreuse and green,with a hue range of 49-106,and grossularite is light maroon,with a hue range of 71-78.The changes in Fe and Al contents are the most important factor that causes the shift in the main absorption valley position(11200-11600 nm)in the thermal infrared spectrum of garnet.The main absorption valley wavelength of garnet is positively correlated with the Fe content and negatively correlated with the Al content.Research has shown that when the main absorption valley wavelength of the thermal infrared spectrum of pomegranate is greater than 11500 nm,it can be used as a thermal infrared spectral exploration marker for copper mineralization in the Zhibula deposit.