Searle (1985), "Distribution of Calcrete
in Holocene Coastal Sands in Relationship to Climate, Southwestern Australia," Journal of Sedimentary Research 55, 86-95.
The Barns calcrete
geochemical anomaly, together with an aerial photo of the prospect, is shown on Figure 2.
Paleocene lignite related sandstones and calcretes
in the adjacent Thar Desert are likely the hosts for leachable uranium.
Estas facies en muchas partes y en ambos lados de la quebrada, se alternan con depositos de calcrete
de conglomerado (Khadkikar, 1999), los cuales forman como especies de acantilados que sobresalen por ser mas resistentes a la erosion.
Uranium mineralisation has been detected both in calcrete
and alaskite rocks.
layers are evident in the swales in the sand plains, and in some areas of Winton Formation outcrop, e.
Na Zona de Baixa Restricao encontram-se as estruturas rochosas praticamente impermeaveis como os aquicludes e aquitardes da Formacao Santa Maria Membro Alemoa, constituida por rochas sedimentares de cor avermelhada, sem textura, de carater argiloso a siltico (lamito) com pequena ocorrencia de depositos de caliche e calcrete
Both of these mountains form impressive topographic landmarks that can be seen from many kilometers away, rising high above the surrounding Namib Desert calcrete
Its origin is uncertain but may represent the degraded and weathered calcrete
core of a fossil dune.
The leach solution is then partially neutralised, using 1 Mt/y of calcrete
slurry, and feeds to the hydrogen sulphide (35,000 t/y) precipitation unit where nickel, cobalt and some impurities are precipitated as a mixed sulphide filter cake.
Between the dunes are the vlei (dry calcrete
pans) each with a crust of mineral mud crazed into attractive mosaics.
Most of the materials dated were calcrete
with some organic carbon and/or shell fragments (Thomas and Shaw 1991).
It is likely that further commercially viable diamond pipes will eventually be located, although prospecting is hampered by the Kalahari sand, and calcrete
layer which covers much of Botswana.
Discusses the main duricrusts, including calcrete
, laterite and silcrete
The presence of calcitc in some of the coarse fractions of the soils and calcrete
observed in the field, coupled with the low Ca and Mg contents of the local groundwater (Smedley 2004), suggest that plant availability of these elements may be poor.