Concentrations of major and trace elements in soil profiles developed over granites across a climosequence in northeastern Brazil

Abstract

Soils formed from granites are distributed worldwide, therefore, studies regarding their geochemical signature on tropical soils are important to understand key processes of soil weathering and soil chemistry. This paper reports the effect of S- and I-type granitic rocks on the content and distribution of trace and major elements in soil profiles developed across a climosequence in Northeastern Brazil. In general, soils developed from I-types show greater trace and major element concentrations than those originated from S-types, due to their higher proportion of accessory and mafic minerals. Geochemical mass balance and enrichment factor data suggest that climatic effects showed a less evident effect on the distribution pattern of trace and major elements from soil profiles underlain by S-type granitic rocks. The highest enrichment factor results evidenced in soils formed on I-types are explained by the rock mineralogy, which imparts higher CEC values and proportion of clay to soils. Trace elements were less leached than major elements during chemical weathering, except for Al, Fe, and P. Geochemical mass balance showed that, regardless of the granite type, the highest depletion of trace and major elements in the pedosphere took place in the humid zones as a consequence of weathering intensity. In this zone, except for quartz, the primary minerals were altered to form secondary minerals, giving rise to kaolinitic soils. These results can be used as reference contents of trace and major elements developed from different granitic rocks in environments with tropical climate. Besides, this research sheds some light on the effect of contrasting granites and a climosequence on soil geochemistry.