Low pressure differentiation of basalts at the Mid-Atlantic Ridge near Ascension - Constraints from experiments at controlled volatile and oxygen fugacities

• Applicant: Professor Dr. Francois Holtz
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2003 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5414733

• Final Report Year: 2008

Final Report Abstract

The main goal of the project was to investigate the processes of MORB-magma differentiation along the MAR (7-11°S) near Ascension Island and to provide quantitative information on the influence of small amounts of H2O on crystallization of main minerals in MORB system. In the course of our research project we have developed and applied two independent methodological approaches to simulate conditions of MORB magma crystallization in the presence of small amounts of H2O. As a result of this study we presented pre-emptive characteristics of basaltic magmas beneath Mid-Atlantic Ridge (MAR 7-11°S) east of Ascension Island and reported H2O-bearing conditions of partial crystallization for geochemically enriched segment MORB magmas (segment A3). The role of H2O in liquidus temperatures of the olivine and plagioclase was investigated experimentally at 200 MPa. Experimental data were parameterized in the form of empirical equations, which can be used to predict the drop in liquidus temperature in H2O-bearing basaltic melts.

Publications

• (2004). Calculations of mineral-melt equilibria in tholeittic system: MELTS versus COMAGMAT. Lithos 73(1-2):S1. EMPG-X, Frankfurt, 1-4 April, 2004
  Almeev, R.R, Ariskin, A.A., Pletchov, P.Y.
  
• (2004). Low pressure differentiation of basalts at the MAR near Ascension: Constraints from experiments at controlled volatile and oxygen fugacities. Schwerpunkt SPP "Ridge" Tagung, Etelsen, June 2004
  Almeev, R.R., Holtz, F., Koepke, J.
  
• (2005). Crystallization conditions of the highly H2O-undersaturated basaltic magmas: an experimental study of the MORBs near Ascension island (6°-10°S). In: Berichte der Deutchen Mineralogischen Gesellschaft (N1). DMG-2005 Aachen, Germany, 18-21 September 2005, p 5
  Almeev, R.R., Holtz, F., Koepke, J.
  
• (2005). Depths of MORB partial crystallization and H2O contents of MORB near Ascension (6°-10°S): phase equilibria modeling and experimental study. Schwerpunkt SPP "Ridge" Tagung, Etelsen, 1-4 June 2005
  Almeev, R.R., Holtz, F., Koepke, J., Haase, K.
  
• (2005). Depths of MORB partial crystallization inferred from the major-element chemistry: phase equilibria simulations of basalts at the MAR near Ascension island (6°- 10°S). Russian Ridge 2005, St.Petersburg, May 2005
  Almeev, R.R., Holtz, F., Koepke, and Haase K.M.
  
• (2005). Depths of partial crystallization and H2O contents of MORB interred from glass composition:phase equilibria simulations of basalts at the Mid-Atlantic Ridge near Ascension island (6°-10°S). EGU, Vienna, April 2005. Geophysical Research Abstracts, Vol. 7, 09910
  Almeev R.R., Holtz F., Koepke J., Haase K.M.
  
• (2006). Depths of partial crystallization and water contents of MORB inferred from glass compositions: phase equilibria simulations of basalts at the MAR near Ascension Island. In: Berichte der Deutchen Mineralogischen Gesellschaft (N1). DMG-2006 Hannover, Germany, 25-27 September 2005, p.8
  Almeev, R.R., Holtz, F., Koepke, J., Haase, K. & Devey, C.
  
• (2006). Effect of small amount of H2O on the liquidus of olivine, plagioclase and clinopyroxene: an experimental study at 200 and 500 MPa. EMPG-XI. 11th - 13th September, University of Bristol UK
  Almeev, R. R., Holtz, F., Koepke, J. & Parat, F.
  
• (2006). Evaluating of PT-conditions of MORB magma crystallization: application of new method to MORB near Ascension (7°-11°S). Schwerpunkt SPP "Ridge" Tagung, Etelsen, 1-4 June 2006
  Almeev, R.R., Holtz, F., Koepke, J., Haase, K. & Devey, C.
  
• (2006). Phase equilibria simulations of basalts at the MAR near Ascension Island at 7-11 °S - estimation of partial crystallization pressure and H2O contents. Bremen, DGG-2006
  Almeev, R.R., Holtz, F., Koepke, J., Haase, K.
  
• (2007) The effect of H2O on olivine crystallization in MORB: Experimental calibration at 200 MPa. American Mineralogist, 92(4):670- 674
  Almeev RR, Holtz F, Koepke J, Parat F, Botcharnikov RE
  
• (2007) The effect of minor H2O content on crystallization in MORB: experiments and applications. Geological Department, Utah University, 17 October 2007
  Almeev, R.R.
  
• (2007) The effect of minor H2O content on crystallization in MORB: experiments, model, applications. Petrologietreffen, Kiel University, 19 May 2007
  Almeev, R.R., Holtz, F., Koepke, J., Ariskin A.A., Haase, K. & Devey, C.
  
• (2007). Depths of partial crystallization of H2O-bearing MORB: phase equilibria simulations of basalts at the MAR near Ascension Island (7°-11°S). Schwerpunkt SPP "Ridge" Tagung, Etelsen, 20-24 June 2007
  Almeev, R.R., Holtz, F., Koepke, J., Haase, K. & Devey, C.
  
• (2007). The effect of minor H2O content on crystallization in MORB: experiments, model, applications. Goldschmidt-2007. August 19-24, 2007 Cologne, Germany
  Almeev, R.R., Holtz, F., Koepke, and Ariskin A.A.
  
• (2007). The effect of minor H2O content on crystallization in MORB: experiments, model, applications. Russian Ridge 2007, Moscow, 5-7 June 2007
  Almeev, R.R., Holtz, F., Koepke, and Ariskin A.A.
  
• (2008) Depths of partial crystallization of H2O-bearing MORB: Phase equilibria simulations of basalts at the MAR near Ascension Island (7°-11°S). Journal of Petrology, 49(1):25-45
  Almeev RR, Holtz F, Koepke J, Haase KM, Devey CW