Gas release systematics of mineral-hosted fluid inclusions during stepwise crushing: implications for 40Ar/39Ar geochronology of hydrothermal fluids

Progressive crushing 40Ar/39Ar dating of gold-bearing quartz vein from the Liaotun Carlin-type gold deposit at the northwest of Guangxi

“…Fluid inclusions in mineral-hosted analysis is one of the most important techniques in modern studies of hydrothermal mineral deposits, as the trapped fossil uids inclusions could directly provide pivotal information on the geochemistry and geochronology of mineralization systems [48][49][50][51] . The key point and the most di culties of uid inclusions geochronological study is how to effectively distinguish and extract the gases from the SFs and PFs respectively 31,[37][38][39]41,52,53 . Just as described by Bodnar 54 , "PFIs are formed during, and as a direct result of, growth of the surrounding host crystal.…”

“…Part of the bigger PFIs which occur along the healed micro-cracks are probably also extracted during the earlier steps. Additionally, experiments show that as long as the crushing times are enough, gases from most of the > 1 µm uid inclusions can be extracted effectively 38,41 .…”

“…The 40 Ar/ 39 Ar in vacuo progressive crushing technique for dating the ages of uid inclusions has been improved and developed for thirty-ve years 31 . This method has been widely applied to constrain the formation ages of hydrocarbon accumulation 32,33 , high-ultrahigh pressure retrograde metamorphism 34,35 , and especial on direct dating of hydrothermal deposit minerals (Cassiterite, sphalerite, wolframite) and gangue minerals like mineralization quartz vein [36][37][38][39][40][41][42][43] . Nevertheless, there is still no successful report by this technique on sediment-hosted Carlin-type gold deposits yet, although mineralization quartz veins with abundant uid inclusions are widely developing in this type of ore deposit.…”

Progressive crushing 40Ar/39Ar dating of a gold-bearing quartz vein from the Liaotun Carlin-type gold deposit, Guangxi, southern China

“…The Ar-isotopic composition of fluids trapped in fluid inclusions carries a signature of the source of the fluid 32 , 35 , 40 , 41 , 48 , 49 . Previous studies have shown that various argon reservoirs are tapped during in vacuo crushing experiments, including PFIs, SFIs, microcracks, crystal defects and mineral interfaces 36 , 40 , 42 , 43 , 48 – 50 . In addition, atmospheric argon trapped in the stainless steel crusher may be released after intense crushing 36 , 48 .…”

“…Fluid inclusion dating is a very important technique in modern studies of hydrothermal mineral deposits, as the trapped fossil fluid inclusions provide pivotal information on the geochemistry and geochronology of mineralization systems 55 – 58 . Critical to obtaining mineralisation ages, and one of the most challenging aspects of the geochronology of fluid inclusions is how to effectively distinguish and extract the gases from primary and secondary fluid inclusions, respectively 31 , 38 – 40 , 42 , 53 , 59 . We follow the definitions of Bodnar 60 , who indicated that fluid inclusions the form during and resulting from growth of the host crystal are considered primary.…”