Combined ICP-OES and XPS analysis to evaluate the [AlO4]0 concentration in quartz: limiting the formation temperature of quartz

Abstract

A proposed quartz thermometer is based on the concentration of [AlO₄]⁰ tetrahedra determined by combining inductively coupled plasma optical emission spectrometry (ICP-OES) with X-ray photoelectron spectroscopy (XPS) data. The concentration of [AlO₄]⁰ tetrahedra in the quartz lattice (C_[AlO4]⁰/ppm) and the formation temperatures of quartz (T_Q/°C) from agate, gold deposits, and granodiorite are calculated by C_[AlO4]⁰ = C_{Al total} (ppm) × k and T_Q (°C) = 3.6 × C_{Al total} (ppm) × k + 33.0, respectively. Where C_{Al total} is the total Al concentration of quartz measured by ICP-OES and k is the relative percentage of [AlO₄]⁰ tetrahedra in the quartz lattice and can be obtained by fitting the Al(2p) XPS spectrum. The obtained formation temperatures of quartz (T_Q) agree well with the equilibrium formation temperature (T_E) calculated by oxygen isotope data. By comparing the relative positions of the two temperature curves of quartz (T_Q and T_E), the composition of the mineral-forming fluid can be inferred. The proposed quartz thermometer can be applied to quartz formed under equilibrium conditions and in Al-saturated environments over a wide temperature range (152–566 °C). The use of the quartz thermometer effectively eliminates interference from different fluid compositions and satisfies the requirements of convenience and economy.