A. Mateus, A. Varajão, F. Oliveira, S. Petit, C. Schaefer
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引用次数: 2
摘要
本文分析了Trindade岛(TI) vulc o do pared组和Morro Vermelho组超基性火山碎屑岩土壤剖面中主、次、微量和稀土元素的地球化学行为。通过两个剖面的质量平衡计算化学元素的损益:一个位于海拔较高(460 m),另一个位于海拔较低(258 m)。在所有剖面中,Al, Fe和Ti由于迁移率低而积累,而Ca, Na, K和Mg则是淋滤最强烈的。海拔较低的土壤由于盐雾的作用,地表K和Mg值较高。稀土元素由高坡向低坡的淋滤作用导致了这些元素在最低海拔(258 m)土壤中的富集,尤其是轻稀土元素,而高海拔剖面由于风化暴露时间较长,呈现Ce正异常。地球化学平衡显示,尽管这些火山岩的性质较年轻,但在土壤形成过程中,Ti、Mn、Fe、Co、Cr、Ni、V、Zr、S的相对富集与流动元素的损失有关。
Geochemical evolution of soils developed from pyroclastic rocks of Trindade Island, South Atlantic
The geochemical behavior of the major, minor, trace and rare earths elements (REEs) in soil profiles from ultramafic volcanoclastic rocks of the Vulcão do Paredão and Morro Vermelho Formation from Trindade Island (TI) was analyzed in this study. Losses and gains of chemical elements were calculated through the mass balance for two profiles along the slope: one located at higher altitude (460 m) and the other at lower altitude (258 m). In all profiles, Al, Fe and Ti accumulate due to their low mobility, whereas Ca, Na, K and Mg are the most intensely leached. Soils located at lower altitude show higher K and Mg values in the surface due to the contribution of saline sprays. Leaching of the REEs from higher to the lower slope led to the enrichment of these elements, especially the light REEs, in the soil at the lowest altitude (258 m). The high altitude profile showed Ce positive anomaly due to longer exposure to weathering. The geochemical balance shows a relative enrichment of Ti, Mn, Fe, Co, Cr, Ni, V, Zr, S related to the loss of mobile elements during the soil formation process, despite the youthful nature of these volcanic rocks.
期刊介绍:
The Brazilian Journal of Geology (BJG) is a quarterly journal published by the Brazilian Geological Society with an electronic open access version that provides an in-ternacional medium for the publication of original scientific work of broad interest concerned with all aspects of the earth sciences in Brazil, South America, and Antarctica, in-cluding oceanic regions adjacent to these regions. The BJG publishes papers with a regional appeal and more than local significance in the fields of mineralogy, petrology, geochemistry, paleontology, sedimentology, stratigraphy, structural geology, tectonics, neotectonics, geophysics applied to geology, volcanology, metallogeny and mineral deposits, marine geology, glaciology, paleoclimatology, geochronology, biostratigraphy, engineering geology, hydrogeology, geological hazards and remote sensing, providing a niche for interdisciplinary work on regional geology and Earth history.
The BJG publishes articles (including review articles), rapid communications, articles with accelerated review processes, editorials, and discussions (brief, objective and concise comments on recent papers published in BJG with replies by authors).
Manuscripts must be written in English. Companion papers will not be accepted.