Bäumler R (2006)
Publication Language: English
Publication Type: Journal article
Publication year: 2006
Publisher: Elsevier
Book Volume: -
Pages Range: -
DOI: 10.1016/j.geoderma.2006.04.017
Within a project studying soil genesis on the southern slopes of the Eastern Himalayas, a comprehensive set of major, trace and rare earth element (REE) contents has been compiled for the first time. Six saprolites and their associated pedons were sampled on metamorphic, migmatitic and leucogranitic parent materials at altitudes ranging from 1520 m to 3770 m. Metamorphic soils are largely illitic, with Si decreasing, and Al and Fe increasing with decreasing degree of metamorphism. The subsoil of a tourmaline-bearing leucogranite is characterised by equally high Si, but higher contents of K and lower Fe, Mg and Ti. A migmatitic profile in southern Bhutan is dominated by hornblende, and is quite distinct from the other lithologies with lower contents of Si and K, but higher Fe, Mg, Ca and Mn. Chondrite-normalised REE patterns compare with post-Archaean materials, with steep light rare earth (LREE) and flat heavy rare earth (HREE) patterns. In comparison to generalised upper crustal composition (UCC), the Bhutanese lithologies show a pronounced Eu anomaly. Whereas the patterns appear rather homogenised in topsoils, the influence of the parent materials causes deviations from the general trend with increasing depth. The occurrence of marine Tethyan sediments is confirmed by a strong positive Ce anomaly in the Central Bhutanese Phobjikha Valley. In the leucogranitic profile, REE depletion is attributed to the presence of monazite, as corroborated by trace element behaviour. Because of the hornblende, REE patterns of the migmatitic profile are flat and without a Eu anomaly. Chemical indices of alteration (CIA) of between 71 and 92 indicate advanced weathering, even at high altitudes. Correlation analyses show that REE are associated with the silt and clay fraction (< 63 μm). At elevations above approximately 3500 m, physical weathering causes passive REE enrichment, however no differentiation of REE concentrations or patterns within the profile is observed. Below 3500 m, increased chemical weathering and leaching appears to be sufficient to release and translocate REEs. In this process, HREE are preferentially translocated, whereas Ce is more refractory than the other lanthanides. This case study confirms that soil weathering and REE behaviour are closely related. © 2006 Elsevier B.V. All rights reserved.
APA:
Bäumler, R. (2006). Geochemical investigation of soils developed in different lithologies in Bhutan, Eastern Himalayas. Geoderma, -, -. https://doi.org/10.1016/j.geoderma.2006.04.017
MLA:
Bäumler, Rupert. "Geochemical investigation of soils developed in different lithologies in Bhutan, Eastern Himalayas." Geoderma - (2006): -.
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