The x-ray identification and crystal structures of clay minerals

Advances in the Crystal Chemistry of Sepiolite and Palygorskite

The residual soil overlying a talc deposit, which occurs as a lens between gneiss and serpentinite in Lancaster County, Pennsylvania, contains talc in all size fractions studied (10 μm to less than 2 μm) and in unfractionated samples. A study of soil samples, obtained by auger drilling, indicates that small amounts of talc can be detected by X-ray diffraction in samples obtained over a large area when the X-ray samples are prepared so that the clays are well oriented. Randomly oriented X-ray samples, in which the level of detection of talc is much poorer, also were successfully used to determine the presence of the talc body by means of quantitative measurements. In addition, the latter procedure was found to be superior in determining the actual size and location of the ore body. It is proposed that such procedures might be used in exploration for similar talc deposits.

methods

Mineralogy of residual soils overlying a talc deposit

The publication of The Clay Mineralogy of British Sediments by Perrin in 1971 collated several decades of clay mineral research in the British Isles and for the first time presented all the data in a stratigraphical framework. While it quickly became a useful source of information for geologists, engineers and soil scientists, it also revealed many gaps in clay mineral data through the geological succession, stimulating further research. Within ten years of publication, a successor to Perrin's book was under discussion by the Clay Minerals Group. Inevitably, the enthusiasm for the concept of the project gave way to the patience of a long gestation. A successor to Perrin (1971) became a standing item on the agenda of Clay Minerals Group Committee meetings, and the bane of many a Chairman's three years in office. By the mid-1990s the project began to show real progress, gathering momentum from the success of an international series of 'Cambridge clay mineral diagenesis conferences' (1981, 1984, 1986, 1989, 1993, 1998) that were supported by the oil industry. A timely injection of financial support from the Joint Association for Petroleum Exploration Courses (JAPEC) ensured a successful conclusion for the project. The cost of publication has been borne by three sponsors: the Clay Minerals Group, JAPEC (UK: training), and the Mineralogical Society. Consequently, the financing of this Special Volume of Clay Minerals is entirely independent of the usual costs of publishing the journal. We owe our particular thanks to Kevin Murphy, Editorial Manager, for his care and humour in guiding Clay minerals in onshore and offshore strata of the British Isles through publication.

Clay minerals in onshore and offshore strata of the British Isles: origins and clay mineral stratigraphy

Steigerung der Nachweisempfindlichkeit von quellungsfähigen Dreischichttonmineralen in Gemengen

The mineralogy and geochemistry of the fine and clay fractions oftill in different moraine types and in different bedrock areas innorthern Finland have been studied. A total of 250 till samples from 140test pits were studied mineralogically and geochemically. X-raydiffraction, differential thermal and thermogravimetric analyses,transmission electron microscopy, X-ray fluorescence and atomicabsorption spectrometry were used as analytical methods. In the clay fraction of till quartz, plagioclase, microcline andamphibole are the primary minerals occurring. The clay minerals properinclude vermiculite, chlorite, illite, swelling-lattice vermiculite andmixed-layer clay minerals. Kaolinite occurs most abundantly in the clayfractions of till in the Kittilä, Jerisjärvi, Kaaresuvanto and Puljuareas. In the clay fraction of Kittilä and Jerisjärvi illite isdioctahedral type, but in their of other study areas both diandtrioctahedral types occur. Kaolinite and dioctahedral illite areevidence of the mixing of the weathered bedrock material into the tillmatrix. In the fine fraction of till most abundant minerals are primaryminerals and clayminerals are in a minor role. In the clay fraction of till the content of primary minerals areat higher and secondary minerals are at lower level in the Granitic andArchaean gneiss areas than in the Greenstone Belt, Svecokarelian schistsand gneiss and Granulite areas. Amphibole, microcline and plagioclaseoccur in very low amounts or are totally destroyed by chemicalweathering in the clay fraction of the till in the Kittilä area. Themineral composition of fine and clay fractions in the tills of northernInari gives an indication that there occur much more mafic volcanitesthan is known today. The mineralogical compositions of fine fraction ofthe tills correlates quite well with the underlying bedrock in all studyareas, but clay fraction does not. Geochemical results are in accordance with the mineralogicalcomposition of both fractions. In the fine fraction of the till Si, Caand Na contents are higher than in the clay fraction. Clay fraction isenriched in Al, Fe, Mg, K and trace elements as compared to the finefraction. Present study material points out that the distribution ofchemical elements in the clay fraction of the till does not correlatewith the composition of the underlying bedrock, but fine fraction doesso with a few exceptions. The chemical composition of till inKaaresuvanto and Inari does not fully correspond to the composition ofthe underlying bedrock as known today. In northern Inari and Kittilä theresults give an indication that there are more mafic volcanites and/orsulphide mineralizations occurring in these areas than is known at thepresent time. The most important factors controlling the mineralogical andgeochemical composition of the fine and clay fractions of the tills innorthern Finland are the composition of the bedrock and the possibleoccurrence of an old weathering crust. The final grain size compositionof the tills and consequently the quantitative proportions of thedifferent minerals are often related to the last glacial quarrying andsorting processes; therefore the mineralogical composition of the tillsis to a certain extent bound also to the respective moraine type.

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The x-ray identification and crystal structures of clay minerals

Citations

Advances in the Crystal Chemistry of Sepiolite and Palygorskite

Mineralogy of residual soils overlying a talc deposit

Clay minerals in onshore and offshore strata of the British Isles: origins and clay mineral stratigraphy

Steigerung der Nachweisempfindlichkeit von quellungsfähigen Dreischichttonmineralen in Gemengen

Mineralogy and geochemistry of the fine and the clay fractions of till in northern Finland

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