Trace Element and Strontium Isotope Constraints on the Origin and Evolution of Paran Continental Flood Basalts of Santa Catarina State (Southern Brazil)

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Abstract
Forty-five selected samples from two different sequences, and from different sites spread over the Parana Basin have been analysed for major and trace elements and Sr isotope ratios. Results demonstrate the existence of two geochemically and isotopically distinct groups, namely a high phosphorus and titanium (HPT) and a low phosphorus and titanium (LPT) group. HPT rocks are relatively rich in LIL elements and have more homogeneous and markedly lower isotopic Sr ratios than LPT rocks. Since no relationship between the two groups was found, they may derive from different mantle sources, the HPT source being more enriched in most incompatible trace elements except Th, U and Rb than the LPT one. The LPT group, comprising basalts to rhyodacites, displays a large range in Sr isotopic ratios. This is interpreted as a result of a fractional crystallization process occurring at high crustal levels associated with assimilation of crustal material.

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