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Uma abordagem microanalítica dos coeficientes de partição em plagioclásio e clinopiroxênio de soleiras basálticas da Formação Serra Geral, Bacia do Paraná, Brasil

2011; Sociedade Brasileira de Geologia; Volume: 41; Issue: 2 Linguagem: Inglês

2177-4382

Leonardo Cardoso Renner, Léo Afrâneo Hartmann, Wilson Wildner, Hans‐Joachim Massonne, Thomas Theye,

Geochemistry and Elemental Analysis

In the present study, detailed micro-analytical data (major and trace elements) in minerals from sills of Serra Geral Formation represents the fi rst attempt to evaluate the partition coefficient of Sc, Ti, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Mo, Cs, Ba, REE, Hf, Ta, Pb, Th and U among coexisting plagioclase, augite and pigeonite from 12 tholeiitic basaltic sills along the eastern border of the Parana Basin, Brazil. These 12 samples come from Rio Grande do Sul, Parana, Sao Paulo and Goias states. Plagioclase/melt partition coefficients K D were determined in core, intermediate and rim zones using LA-ICP-MS and the results were compared with the variations of the elements Ca, Al, Na and Si in those areas. Partition coefficients of Sr and Eu decrease with the increase of Ca concentration in plagioclase. A reduction in temperature and consequently a rise in Na and Si levels increase the partition coefficients of Sr and Eu at the rim of mineral The K D of Ni and V in clinopyroxene has positive correlations with Mg2+, Ca2++ and Al3+ due to higher concentrations of those elements at the core and lower concentration towards the rim and negative correlations of K D of Sc, Cr, Co, Pb and Lu, due to preferential substitutions by Fe2+ in sixfold coordination. The use of LA-ICP-MS and EPMA made possible the chemical quantification of major and trace elements and the determination of partition coefficients in coexisting plagioclase and clinopyroxene in basaltic melts.