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内蒙古中部碱长花岗岩型铌钽矿床典型岩矿光谱识别特征

Spectral Identification Characteristics of Typical Rocks and Minerals in Alkali Feldspar Granite Type Nb-Ta Deposits in Central Inner Mongolia

  • 摘要: 内蒙古中部地区,位于大兴安岭南段—华北陆块北缘成矿带,因其碱长花岗岩型铌钽矿的广泛分布而备受关注。尽管该地区铌钽矿资源丰富,但对其光谱学特征的系统认识尚不足,在一定程度上制约了矿产资源勘查的精确性和效率。本文以赵井沟大型铌钽矿床为例,利用便携式短波红外及热红外光谱仪对赵井沟典型岩矿样本开展光谱测量与分析,揭示富铌钽钠长花岗岩、天河石化钠长花岗岩、天河石伟晶岩、黑云母二长花岗岩、含黑钨矿石英脉波谱特征,并对其展开对比研究。研究表明:在近红外光谱范围内,与USGS光谱库中的标准钠长花岗岩光谱进行对比分析,发现2360nm处的弱吸收特征可作为天河石化钠长花岗岩与其他岩石及矿物区分的关键波段,此差异推测可能由岩石的蚀变矿化过程引起。在热红外光谱分析中,含黑钨矿石英脉因其显著的高反射率和“三峰”特征而易于区分与识别。尽管富铌钽钠长花岗岩、天河石伟晶岩和黑云母二长花岗岩在光谱形态上具有一定的相似性,但它们在2200nm附近的吸收深度的大小和峰强比的差异,为有效地区分这些矿物提供了重要依据。

     

    Abstract: Located in the central region of Inner Mongolia, within the southern segment of the Daxing’anling-North China Craton metallogenic belt, the area is notable for its widespread distribution of alkaline granite-type niobium-tantalum (Nb-Ta) deposits. Despite the region’s rich Nb-Ta resources, a comprehensive understanding of its spectroscopic characteristics remains inadequate, hindering precise and efficient mineral exploration. This study focuses on the Zhaojinggou large Nb-Ta deposit, employing portable short-wave infrared and thermal infrared spectrometers to analyze typical rock and mineral samples. The research reveals distinctive spectroscopic features of Nb-Ta enriched albite granite, amazonitization albite granite, amazonite pegmatite, biotite monzogranite, and wolframite-quartz vein. Comparative analysis, particularly against the standard sodium granite spectrum from the USGS spectral library, identifies a specific weak absorption feature at 2360nm, crucial for distinguishing amazonitization albite granite from other rocks and minerals, likely attributed to rock alteration and mineralization processes. In thermal infrared spectroscopy, quartz veins containing wolframite are distinguished by their high reflectance and “three-peak” features. Despite their similar spectral shapes, Nb-Ta enriched albite granite, amazonite pegmatite, and biotite monzogranite can be distinguished by the absorption depth and the ratio of absorption peak intensity around 2200nm. These findings provide a foundational dataset for future remote sensing surveys and evaluations of Nb-Ta mineral resources. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202401090001.

     

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