RT Journal Article
T1 Chemical interdiffusion between Na-series tephritic and phonolitic melts with different H2O content, temperature, and oxygen fugacity values
A1 González García, Diego
A1 Pohl, Florian
A1 Marxer, Felix
A1 Krasheninnikov, Stepan
A1 Almeev, Renat
A1 Holtz, François
AB The diffusive exchange of major elements in Na-series tephrite–phonolite diffusion couples with compositions relevant to the Canary Islands magmatism was determined at 300 MPa and variable H2O concentrations (0.3 wt % to 3.3 wt %), temperatures (1150 to 1300 °C), and fO2 levels (NNO−1.5 to NNO+1.7). Composition-dependent effective binary diffusion coefficients were determined from concentration–distance profiles. Results show a wide range of diffusivities for different cations, consistently following the sequence Na ≫ Al ≫ K ≥ Mg = Fe = Ca > Si > Ti, with a mild diffusivity contrast (0.2–0.8 log units) between tephritic and phonolitic melts. Na is the fastest component, with diffusivities falling ∼1.0 log units above those of Si for any given condition. An anomalously fast Al diffusion is observed, with DAl falling ∼0.4 log units above Si and ∼0.6 log units below Na, suggesting a prevalence of Al–alkali coupling across our range of run conditions. The relationships between log D and H2O content in melt for all cations in an intermediate composition are strongly nonlinear and can be fitted using an exponential function with a convergence in diffusion coefficients for different temperatures with increasing H2O content. Thus, Arrhenius analyses result in a decrease in activation energies from 222–293 kJ mol−1 at 1.7 wt % H2O to 48–112 kJ mol−1 at 3.0 wt % H2O. These results provide new data on chemical interdiffusion in highly alkaline Na-rich melts and suggest that H2O content plays a key role in increasing the chemical efficiency of magma mixing at low temperatures. The obtained dataset is used to test chemical controls of magma mixing in the El Abrigo ignimbrite, Tenerife, where banded pumices involving basanitic–tephritic to phonolitic magmas are common in several compositionally bimodal ignimbrite units.
PB Copernicus Publications
SN 0935-1221
YR 2024
FD 2024-08-23
LK https://hdl.handle.net/20.500.14352/108256
UL https://hdl.handle.net/20.500.14352/108256
LA eng
NO González-García, D., Pohl, F., Marxer, F., Krasheninnikov, S., Almeev, R., and Holtz, F.: Chemical interdiffusion between Na-series tephritic and phonolitic melts with different H2O content, temperature, and oxygen fugacity values, Eur. J. Mineral., 36, 623–640, https://doi.org/10.5194/ejm-36-623-2024, 2024
NO Alexander von Humboldt Stiftung
NO Deutsche Forschungsgemeinschaft
DS Docta Complutense
RD 7 abr 2025