Nondestructive measurement of water content and moisture migration of unsaturated red clays in South China

To reveal the moisture migration mechanism of the unsaturated red clays, which are sensitive to water content change and widely distributed in South China, and then rationally use them as a filling material for highway embankments, a method to measure the water content of red clay cylinders using X-ray computed tomography (CT) was proposed and verified. Then, studies on the moisture migrations in the red clays under the rainfall and ground water level were performed at different degrees of compaction. The results show that the relationship between dry density, water content, and CT value determined from X-ray CT tests can be used to nondestructively measure the water content of red clay cylinders at different migration time, which avoids the error reduced by the sample-to-sample variation. The rainfall, ground water level, and degree of compaction are factors that can significantly affect the moisture migration distance and migration rate. Some techniques, such as lowering groundwater table and increasing degree of compaction of the red clays, can be used to prevent or delay the moisture migration in highway embankments filled with red clays.

Grain size and mineral compositions of Pacific red clays

Hypotheses of origin of ocean deep red clays are under discussion. On an example of the Pacific Ocean grain size, mineralogy and chemical composition of clays are considered. It is shown that they formed from atmospheric dust and andesite pyroclastics. Accumulation of the clays occurred through deposition particle-by-particle and by pellet transport.

Chemical variability in clays and pottery from a traditional cooking pot production village: Testing assumptions in Pereruela

This paper explores analytically the contemporary pottery-making community of Pereruela (north-west Spain) that produces cooking pots from a mixture of red clay and kaolin. Analyses by different techniques (XRF, NAA, XRD, SEM and petrography) showed an extremely high variability for cooking ware pottery produced in a single production centre, by the same technology and using local clays. The main source of chemical variation is related to the use of different red clays and the presence of non-normally distributed inclusions of monazite. These two factors induce a high chemical variability, not only in the output of a single production centre, but even in the paste of a single pot, to an extent to which chemical compositions from one"workshop", or even one"pot", could be classified as having different provenances. The implications for the chemical characterization and for provenance studies of archaeological ceramics are addressed.

(Table 3, page 264), Composition of a manganese micronodule found in a fossil red clay bed from Western Timor

Chemical analyses are presented for two Cretaceous clays from Noil Tobee, Timor. Mineralogical examination has shown that they consist principally of quartz, feldspar, illite and chlorite, together with minor amounts of montmorillonite. Both chemically and mineralogically the clays are very similar to the recent argillaceous deep-sea sediments of the Pacific and Indian Oceans, which confirms Molengraaff's theory (1921) that they are of deep-sea origin. Further confirmation of this theory is provided by comparison of the composition of micromanganese nodules, separated from one of these clays, with that of manganese nodules from the Pacific Ocean.

Mesozoic sequence of Fuerteventura (Canary Islands): Witness of Early Jurassic sea-floor spreading in the central Atlantic

The Fuerteventura Jurassic sedimentary succession consists of oceanic and elastic deposits, the latter derived from the southwestern Moroccan continental margin. Normal mid-oceanic-ridge basalt (N-MORB) flows and breccias are found at the base of the sequence and witness sea-floor spreading events in the central Atlantic. These basalts were extruded in a postrift environment (post-late Pliensbachian), We propose a Toarcian age for the Atlantic oceanic floor in this region, on the basis of the presence higher up in the sequence of the Bositra buchi filament microfacies (Aalenian-Bajocian) and of elastic deposits reflecting tectono-eustatic events (e.g,, late Toarcian to mid-Callovian erosion of the rift shoulder). The S-l sea-floor oceanic magnetic anomaly west of Fuerteventura is therefore at least Toarcian in age. The remaining sequence records Atlantic-Tethyan basinal facies (e.g., Callovian-Oxfordian red clays, Aptian-Albian black shales) alternating with elastic deposits (e.g., Kimmeridgian-Berriasian periplatform calciturbidites and a Lower Cretaceous deep-sea fan system). The Fuerteventura N-MORB outcrops represent the only Early Jurassic oceanic basement described so far in the central Atlantic. They are covered by a 1600 m, nearly continuous sedimentary sequence which extends to Upper Cretaceous facies.

Clay mineral and geochemical composition of Cenozoic paleosol in the Eastern Alps (Austria)

Red clays from Cenozoic palaeosols of the Eastern Alps record periods of stagnating uplift and decrease of relief. Tropical to sub-tropical weathering of a crystalline substratum formed dominant or abundant kaolinite, reflecting Paleogene and Early Miocene conditions, respectively. Abundant illite and chlorite, but a lack of kaolinite in red clays on the plateaus of the Northern Calcareous Alps reflects feldspar-poor compositons of the Cenozoic siliciclastic cover. The presence of high Ba/Sr and Rb/Sr ratios and vermiculite in these red clays indicates high precipitation and temperate weathering conditions, respectively, during the Late Miocene and Early Pilocene on the uplifting plateaus of the Northern Calcareous Alps.

Análise do comportamento de queima de argilas e formulações para revestimento cerâmico

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeitos da composição mineralógica e distribuição de partículas na formulação de massas: pólo cerâmico de Santa Gertrudes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)