dépôt d'altération

CONT: Les substrats sur lesquels seront érigées les éoliennes sont essentiellement des dépôts d'altération, provenant de la désagrégation ou de la décomposition du substrat rocheux en place, ainsi que de dépôts qui ont été en partie remaniés par les eaux de surface et la gravité (colluvions) [...]
CONT: Les sapinières occupent surtout des versants en pente forte recouverts de dépôts d'altération (altérites) ou d'accumulation de sédiments (colluvions).

CONT: Mineralogy and geology of the Maungaparerua halloysite deposit in New Zealand. ... The halloysite deposit was formed by hydrothermal alteration of rhyolite flow rocks. Superimposed on the hydrothermally altered halloysite is deep intensive surficial weathering resulting from the humid climate on the extreme tip of the North Island. The deposit has been drilled and the cores have been analyzed mineralogically and chemically. Drilling has shown that the ... altered rocks contain about 50% quartz and fine amorphous silica and 50% of a mix of halloysite, kaolinite, and allophane with a small amount of plagioclase feldspar in the coarse fraction. The upper 8-30 m, with an average of 15 m, of the halloysite alteration deposit consists of relatively soft clay.
CONT: Stratigraphy and petrology of hydrothermal alteration deposits related to Strombolian versus Surtseyan activity in Llancanelo Volcanic Field, Mendoza-Argentina.
CONT: Magnesite (magnesium carbonate - MgCO3) occurs as bedded sedimentary deposits, replacement deposits or alteration deposits with minor amounts of limestone, silica and iron.