TY - JOUR

T1 - Ascent of volatile-rich felsic magma in dykes: a numerical model applied to deep-sourced porphyry intrusions

AU - Abdullin, R.

AU - Melnik, O.

AU - Rust, A.

AU - Blundy, J.

AU - Lgotina, E.

AU - Golovin, S.

N1 - We thank BHP for financial support. JB acknowledges support from a Royal Society Research Professorship (RP\R1\201048), OM acknowledges support from College de France, PAUSE program (C7H-PUB23A59).

PY - 2024/3/1

Y1 - 2024/3/1

N2 - Dyke propagation is a mechanism for more rapid ascent of felsic magmas through the crust than is possible via diapirs or percolative flow. As it ascends, the magma undergoes complex physical and chemical transformations induced by decompression and cooling. These processes dramatically change the magma density and viscosity, which in turn affect magma ascent rate and the depth at which the dyke arrests. We present a mathematical model of dyke propagation for silicic magmas taking into account the presence of multiple volatile species (H2O and CO2), bubble growth, heat advection and loss, crystallization and latent heat release. We consider conditions for dykes associated with porphyry ore deposits, which may represent an end-member in rapid ascent of felsic magmas from depth. In particular, we simulate the propagation of dykes launched from a deep (900 MPa), volatile-saturated magma source, testing the effects of the magma H2O/CO2 content, temperature and mass on its ascent rate and final emplacement depth. The model predicts short ascent times (hours to days), with a large increase in viscosity at shallow depth, leading to stagnation and solidification of the dyke. Higher initial water content, higher temperature and larger mass of the magma in the dyke promote faster propagation and shallower arrest. Volatile loss from ascending magma remains limited until the stagnation depth, providing a potential mechanism for transfer of deep volatiles to hypabyssal blind intrusions associated with porphyry ore deposits. Our findings are applicable to the problem of silicic magma ascent through the crust more generally.

AB - Dyke propagation is a mechanism for more rapid ascent of felsic magmas through the crust than is possible via diapirs or percolative flow. As it ascends, the magma undergoes complex physical and chemical transformations induced by decompression and cooling. These processes dramatically change the magma density and viscosity, which in turn affect magma ascent rate and the depth at which the dyke arrests. We present a mathematical model of dyke propagation for silicic magmas taking into account the presence of multiple volatile species (H2O and CO2), bubble growth, heat advection and loss, crystallization and latent heat release. We consider conditions for dykes associated with porphyry ore deposits, which may represent an end-member in rapid ascent of felsic magmas from depth. In particular, we simulate the propagation of dykes launched from a deep (900 MPa), volatile-saturated magma source, testing the effects of the magma H2O/CO2 content, temperature and mass on its ascent rate and final emplacement depth. The model predicts short ascent times (hours to days), with a large increase in viscosity at shallow depth, leading to stagnation and solidification of the dyke. Higher initial water content, higher temperature and larger mass of the magma in the dyke promote faster propagation and shallower arrest. Volatile loss from ascending magma remains limited until the stagnation depth, providing a potential mechanism for transfer of deep volatiles to hypabyssal blind intrusions associated with porphyry ore deposits. Our findings are applicable to the problem of silicic magma ascent through the crust more generally.

KW - Buoyancy

KW - Dyke propagation model

KW - Magma viscosity

KW - Porphyry deposits

KW - Volatile exsolution

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85184075140&origin=inward&txGid=4c7ee36e432ceed222741ae78bd3214b

UR - https://www.mendeley.com/catalogue/a4cff4bc-e638-35b4-a3b4-d39752928df5/

U2 - 10.1093/gji/ggae027

DO - 10.1093/gji/ggae027

M3 - Article

VL - 236

SP - 1863

EP - 1876

JO - Geophysical Journal International

JF - Geophysical Journal International

SN - 0956-540X

IS - 3

ER -