Volatile elements in alkaline and calc-alkaline rocks from the Colima graben, Mexico: constrains on their genesis and evolution
Por:
Macias J.L., Capaccioni B., Conticelli S., Giannini L., Martini M., Rodriguez S.
Publicada:
1 ene 1993
Resumen:
Based on major element chemical composition, three groups of rocks having different parental magmas can be recognized in the Colima graben region. The most mafic rocks belong to the alkaline group, which display the highest incompatible and compatible element contents among the rocks studied. The second group, the calc-alkaline volcanics have the largest compositional range among the rocks studied due probably to low pressure evolutionary processes. A third group straddles the subalkaline-alkaline field boundary, and has K2O abundances intermediate between alkaline and calc-alkaline volcanics. All the most primitive rocks of the three groups are characterized by comparable low abundances of C and S. Cl is initially relatively low, but tends to increase with the degree of evolution. On the contrary, the most primitive rocks of the three groups have distinctly different F contents. Alkaline rocks have the highest values and calc-alkaline the lowest F contents. Fluorine, as well as chlorine, tends to increase with the degree of evolution in calc-alkaline and high potassium calc-alkaline rocks. -from Authors
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