Mechanisms of magma degassing at mid-oceanic ridges and the local volatile composition (4He–40Ar⁎–CO2) of the mantle by laser ablation analysis of individual MORB vesicles
作者： A. Colin , P. Burnard , B. Marty
DOI: 10.1016/J.EPSL.2012.10.022
关键词: Fractionation 、 Igneous differentiation 、 Helium 、 Geology 、 Laser ablation 、 Mantle (geology) 、 Seafloor spreading 、 Pillow lava 、 Mineralogy 、 Mid-ocean ridge
摘要: Individual vesicles in 3 samples of MORB glasses commonly preserve significantly different volatile (He, Ar, CO 2 ) compositions. Five separate glass from ridges were investigated, selectively opening targeted using a 193 nm excimer laser. One sample shows evidence syn-emplacement selective helium loss the rim close to crystallised zone pillow lava, proving that He contents and low He/Ar ratios do not always reflect mantle and/or magmatic processes. However composition three these covers large ranges Ar/CO with linear variations plots ln(He/Ar) vs. ln(Ar/CO which are consistent Rayleigh distillation at equilibrium allow relative abundances volatiles source be estimated by correcting for degassing processes on sample-by-sample basis. This technique presents new tool characterising fractionation have modified initial composition. The results confirm heterogeneous / ratio regions Azores enriched C/ compared N-MORBs. considerable heterogeneity vesicle compositions within such small volume ( requires injection less degassed magma shallow level before eruption. maximum time interval between mixing quenching seafloor is order few hours.
harvard.edu
sci-hub.se 参考文章(82)
P. Burnard, D. Harrison, G. Turner, R. Nesbitt, Degassing and contamination of noble gases in Mid‐Atlantic Ridge basalts Geochemistry Geophysics Geosystems. ,vol. 4, pp. 1- 20 ,(2003) , 10.1029/2002GC000326
J. Matsuda, T. Matsumoto, H. Sumino, K. Nagao, J. Yamamoto, Y. Miura, I. Kaneoka, N. Takahata, Y. Sano, The 3He/4He ratio of the new internal He Standard of Japan (HESJ). Geochemical Journal. ,vol. 36, pp. 191- 195 ,(2002) , 10.2343/GEOCHEMJ.36.191
R.J. Poreda, S. Arnórsson, Helium isotopes in Icelandic geothermal systems: II. Helium-heat relationships Geochimica et Cosmochimica Acta. ,vol. 56, pp. 4229- 4235 ,(1992) , 10.1016/0016-7037(92)90263-I
F. Pineau, M. Javoy, Strong degassing at ridge crests: The behaviour of dissolved carbon and water in basalt glasses at 14°N, Mid-Atlantic Ridge Earth and Planetary Science Letters. ,vol. 123, pp. 179- 198 ,(1994) , 10.1016/0012-821X(94)90266-6
Aude Raquin, Manuel Moreira, Atmospheric 38Ar/36Ar in the mantle: Implications for the nature of the terrestrial parent bodies Earth and Planetary Science Letters. ,vol. 287, pp. 551- 558 ,(2009) , 10.1016/J.EPSL.2009.09.003
W.F. McDonough, S.-s. Sun, The composition of the Earth Chemical Geology. ,vol. 120, pp. 223- 253 ,(1995) , 10.1016/0009-2541(94)00140-4
P.G. Burnard, D.W. Graham, K.A. Farley, Mechanisms of magmatic gas loss along the Southeast Indian Ridge and the Amsterdam ^St. Paul Plateau Earth and Planetary Science Letters. ,vol. 203, pp. 131- 148 ,(2002) , 10.1016/S0012-821X(02)00828-2
Bernard Marty, Nitrogen content of the mantle inferred from N 2 -Ar correlation in oceanic basalts Nature. ,vol. 377, pp. 326- 329 ,(1995) , 10.1038/377326A0
Pete Burnard, The bubble-by-bubble volatile evolution of two mid-ocean ridge basalts Earth and Planetary Science Letters. ,vol. 174, pp. 199- 211 ,(1999) , 10.1016/S0012-821X(99)00254-X
M. D. Kurz, W. J. Jenkins, S. R. Hart, Helium isotopic systematics of oceanic islands and mantle heterogeneity Nature. ,vol. 297, pp. 43- 47 ,(1982) , 10.1038/297043A0