نتایج جستجو برای: clay minerals

تعداد نتایج: 41990  

Journal: :Astrobiology 2012
Dirk Schumann Hyman Hartman Dennis D Eberl S Kelly Sears Reinhard Hesse Hojatollah Vali

The potential role of clay minerals in the abiotic origin of life has been the subject of ongoing debate for the past several decades. At issue are the clay minerals found in a class of meteorites known as carbonaceous chondrites. These clay minerals are the product of aqueous alteration of anhydrous mineral phases, such as olivine and orthopyroxene, that are often present in the chondrules. Mo...

2006
J. Morkel S. J. Kruger M. K. G. Vermaak

Kimberlite is described as a diverse and complex hybrid rock in the literature. It is also described as volatile rich, potassic, ultrabasic, igneous rocks that occur as volcanic pipes, dykes and sills1. The minerals present in kimberlites vary widely and can include from trace to predominance any of the following minerals: apatite, calcite, chlorite, diopside (pyroxene), magnetite, monticellite...

2012
P. Blanc P. Vieillard H. Gailhanou

The thermodynamic properties of clay minerals, which control the stability of these minerals in solution, are still a matter of debate in spite of recent advances (Gailhanou et al., submitted). This is especially the case for the minerals that may structurally include trace elements and potential radionuclides such like Ni, Cd, Co, Cr, Mn, Pb, ... The usual methods developed in order to predict...

Journal: :Science 2006
Martin Kennedy Mary Droser Lawrence M Mayer David Pevear David Mrofka

An enigmatic stepwise increase in oxygen in the late Precambrian is widely considered a prerequisite for the expansion of animal life. Accumulation of oxygen requires organic matter burial in sediments, which is largely controlled by the sheltering or preservational effects of detrital clay minerals in modern marine continental margin depocenters. Here, we show mineralogical and geochemical evi...

2006

Clay minerals may be si<j'nifieant indieatoi's of earth processes. They form throufrh a range which involves at one extreme the action of compressed water vapor at a temperature of several hundred degrees centigrade, and at the other extreme, the action of atmospheric agencies at an ordinary temperature. Not recognized as original products of magmatic crystallization, clay minerals are prima fa...

2006
Tim J. Tambach Edo S. Boek Berend Smit

Nanocomposites of clay minerals and surfactants are of practical importance in many fields. Beside the use of these systems for pollution removal from waste water, they can also be used as catalysts, to stabilize clay formations while drilling for hydrocarbons, or for improving the strength of polymers. The nanocomposites are obtained through exchange of natural counter ions by ionic surfactant...

Journal: :journal of agricultural science and technology 2013
s. s. hashemi m. baghernejad m. najafi ghiri

this study investigated the relationship between clay minerals and different soil moisture regimes in gypsiferous soils of fars province in southern iran. the overall climate of the province is arid and semi-arid and, under this condition, parent material is the most important factor affecting clay minerals distribution. beside this factor, climate conditions have determining role too. palygors...

2017
L. J. Wooldridge R. H. Worden J. Griffiths A. Thompson P. Chung

The presence of clay-sized particles and clay minerals in modern sands and ancient sandstones has long presented an interesting problem, because primary depositional processes tend to lead to physical separation of fineand coarse-grained materials. Numerous processes have been invoked to explain the common presence of clay minerals in sandstones, including infiltration, the codeposition of floc...

Journal: :Environmental toxicology and chemistry 2009
Dongmei Zhang Dongqiang Zhu Wei Chen

Nitroaromatic compounds are produced and used in large quantities worldwide and are frequently detected contaminants in the environment. Sorption is one of the fundamental processes controlling the transport and availability of nitroaromatics, but previous studies have focused mainly on sorption to model clay minerals, whereas little attention has been paid to the sorptive interactions with nat...

2015
Swarup Kumar Naveen Kumar

Shales are defined as fine-grained terrigenous sediments and rocks that contain 50% or more of terrigenous, and generally argillaceous, clastic components less than 0.062 mm in size. In the shales, clay-size components often dominate their rock properties, such as density, plasticity, parting, compatibility and swelling. Generally the size boundary between clay and silt is 4μm, but most clay mi...

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