Textures and chemical compositions of muscovite and quartz: Implications for granite-hosted high-purity quartz mineralization and exploration in South China
Yong Zhang, Jiayong Pan, Fei Xia, Haibo Zhao, Zhe Xu, Guoqi Liu, Fujun Zhong, Xiaotian Zhang, Ying Liu, Gaofeng Du, Xuefeng Zhang, Jianjun Zhang, Chunhua Tang
Abstract
High-purity quartz (HPQ) has extremely low total impurity content (<20 ppm, IOTA CG, a HPQ standard of Unimin) and is indispensable to many high-tech optoelectronic industries. Whilst the controlling factors for the granite-hosted HPQ formation are yet to be well resolved, it is generally considered to be related to temperature and pressure, and/or specific purification processes. Here, we analyzed the chemical compositions of quartz and muscovite from various HPQ occurrences in South China. The results indicate that the F content in muscovite and Ti content in quartz provide useful indicators for exploring and characterizing the granite-hosted HPQ. More specifically, we found that granites containing muscovite with ≤0.100 wt% F have the potential to form 4N5-grade (SiO2 ≥99.995 wt%) HPQ, whereas those with 0.1-1 wt% F have the capacity to generate 3N- (SiO2 ≥ 99.900 wt%) to 4N5-grade HPQ. The ideal quartz crystallization temperature (titanium-in-quartz geothermometer (TitaniQ)) to generate 4N- (SiO2 ≥99.990 wt%) grade HPQ is 420 to 490 °C. Higher F content in the granitic melt, which implies higher volatile content, would lower the magma solidus and contribute to the incorporation of impurities such as lattice-bound Ti-Al and fluid inclusions. We propose that in-situ analysis of muscovite and quartz supports rapid assessment of the metallogenic potential of granite-hosted HPQ.