Abstract
Within augite and pigeonite grains of the Skaergaard ferrogabbro 4430, the Ca-poor phases contain only three mole percent of CaSiO3, and the Mg-Fe partition coefficients between the Ca-poor and Ca-rich phases are extremely small with 0.46 for augite and 0.51 for pigeonite grains. These values indicate existence of diffusion within each grain (intragranular diffusion) at considerably low temperatures.
The compositions are slightly but definitely different between the Ca-rich phases in augite and pigeonite grains as well as between the Ca-poor phases in augite and pigeonite grains. This indicates that the diffusion among the grains (inter-granular diffusion) has not taken place under the subsolidus condition of the Skaergaard intrusion.
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Nobugai, K., Tokonami, M. & Morimoto, N. A study of subsolidus relations of the Skaergaard pyroxenes by analytical electron microscopy. Contr. Mineral. and Petrol. 67, 111–117 (1978). https://doi.org/10.1007/BF01046569
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DOI: https://doi.org/10.1007/BF01046569