Evaluating the Potential of Rhyolitic Glass as a Lithium Source for Brine Deposits

Abstract

Lithium is an economically important element that is increasingly extracted from brines accumulated in continental basins. While a number of studies have identified silicic magmatic rocks as the ultimate source of dissolved brine lithium, the processes by which Li is mobilized remain poorly constrained. Here we focus on the potential of low-temperature, post-eruptive processes to remove Li from volcanic glass and generate Li-rich fluids. The rhyolitic glasses in this study (from the Yellowstone-Snake River Plain volcanic province in western North America) have interacted with meteoric water emplacement as revealed by textures and a variety of geochemical and isotopic signatures. Indices of glass hydration correlate with Li concentrations, suggesting Li is lost to the water during the water–rock interaction. We estimate the original Li content upon deposition and the magnitude of Li depletion both by direct in situ glass measurements and by applying a partition-coefficient approach to plagioclase Li contents. Across our whole sample set (19 eruptive units spanning ca. 10 m.y.), Li losses average 8.9 ppm, with a maximum loss of 37.5 ppm. This allows estimation of the dense rock equivalent of silicic volcanic lithologies required to potentially source a brine deposit. Our data indicate that surficial processes occurring post-eruption may provide sufficient Li to form economic deposits. We found no relationship between deposit age and Li loss, i.e., hydration does not appear to be an ongoing process. Rather, it occurs primarily while the deposit is cooling shortly after eruption, with δ18O and δD in our case study suggesting a temperature window of 40° to 70°C.

Biotite as a recorder of an exsolved Li-rich volatile phase in upper-crustal silicic magma reservoirs

“…For bulk-mineral analyses, crystal separates were isolated from the bulk-rock samples, milled, and then analyzed with X-ray diffraction (XRD) using an AXS D8 Advance diffractometer equipped with a Lynxeye superspeed detector at the Institute of Geochemistry and Petrology, ETH Zürich. Oxygen isotope analyses were performed at the University of Cape Town (South Africa) using conventional analyses on bulk samples of 50-100 mg and laser fluorination for biotites following the methods described by Ellis et al (2021). Lithium isotopic measurements were carried out at the Czech Geological Survey in Prague (Czech Republic) following methods outlined in Magna et al (2004).…”

“…The 'Green Revolution' to address current global climate change, and growing demand for energy storage in batteries (e.g., for electric vehicles) have focused attention on the occurrence and global cycling of the elements required for this technology, such as lithium, cobalt, or tellurium. Although lithium (Li) found in economic deposits is generally thought to be sourced from silicic magmatism (Hofstra et al, 2013;Benson et al, 2017;Ellis et al, 2021), the actual mechanisms by which Li is enriched and ultimately removed from these magmas remain poorly constrained. Many economically important metals are concentrated by processes such as partition-ing between silicate melt and magmatic fluids occurring at the magmatic-hydrothermal transition; therefore, understanding these processes has been a topic of intense interest from both experimental perspectives (e.g., Webster et al, 2004;Iveson et al, 2019) and natural samples (Zajacz et al, 2008).…”

Hydrothermal enrichment of lithium in intracaldera illite-bearing claystones

“…In the McDermitt paleo-lake, a Li-rich Mg-smectite neoformed preferentially over pure stevensite because the lake water contained elevated activities of Li + , Rb + , F − , and other solutes due to the relatively high enrichment of these elements in the McDermitt source rhyolitic magma (7). Following the main eruption, the solutes were leached from outflow rhyolitic ignimbrite glass and other volcanic rock (43) during immediately post-eruptive cooling (44) and from the hot, thickly ponded intracaldera tuff during sustained devitrification and degassing (Fig. 4) (9,45).…”

Timing of Rhyolite Intrusion and Carlin-Type Gold Mineralization at the Cortez Hills Carlin-Type Deposit, Nevada, USA

“…Whether hydration was related to Carlin-type alteration is unknown. Hydration of vitrophyres by low-temperature groundwater has long been known to induce substantial Na2O loss commonly accompanied by K2O gain (Jezek and Noble, 1978;Ellis et al, 2022), although hydration by epithermal fluids could also remove Na2O.…”