Textures and chemical compositions of muscovite and quartz: Implications for granite-hosted high-purity quartz mineralization and exploration in South China

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 4 N5-grade (SiO2 ≥ 99.995 wt%) HPQ, whereas those with 0.1–1 wt% F have the capacity to generate 3 N- (SiO2 ≥ 99.900 wt%) to 4 N5-grade HPQ. The ideal quartz crystallization temperature (titanium-in-quartz geothermometer (TitaniQ)) to generate 4 N- (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.