The volatile contents of silicic crustal magmas inform models for volcanism, degassing behaviour, and hydrothermal ore formation. Volatile saturation pressures of phenocryst-hosted melt inclusions are generally restricted to late-stage, shallow magmas that have typically undergone substantial, ascent-driven degassing of CO₂ and SO₂. As an alternative approach, we directly sample the volatile contents of rhyolitic melt inclusions in the accessory mineral zircon. Our results reveal that zircons grow over an exceptional crustal depth range, from Moho depths (>25 km; deepest melt inclusion 31 km) to the upper crust (~5 km). Significantly, melt inclusions from porphyry copper deposit-related magmas have high melt inclusion CO₂ contents (up to 3970 ppm), indicating CO₂-rich sources (equilibrium fluid molar fraction CO₂ up to 0.95). Deep crustal zircons are transported to shallow levels in silicic melts percolating through transcrustal mush systems and/or in rapidly ascending volatile-charged magmas. 

This will be a hybrid meeting. You can join in G7 or via Zoom:

https://bristol-ac-uk.zoom.us/j/97443036332?pwd=anpDc2s0ZWcwZzJseERFVFVmbU51dz09

Meeting ID: 974 4303 6332

Passcode: 862769