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This programme deals with the problems of sampling and analysing rocks. Professor I.G, Gass introduces the programme by showing a terrestrial basalt and an oceanic basalt. Optically they appear sim...ilar and chemically, as far as an analysis of major oxides is concerned, they again appear to be the same. If differentiamtion is to be based on an analysis of trace elements the sample must be representative. John B. Wright, Reader in Earth Sciences explains how to collect a representative sample from outcrops of igneous, metamorphosed and sedimentary rocks in the field and from under the sea. He then points out some of the problems of contamination during the laboratory preparation of the sample for analysis. Dr. Richard Thorpe, lecturer in Geochemistry demonstrates one of the x-Ray techniques for rock analysis x-Ray fluorescence or XRP. The two basalts mentioned earlier in the programme are analysed for trace elements and are found to be significantly different.
Metadata describing this Open University video programme
Item code: S2-2; 01
First transmission date: 01-07-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:25:00
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Producer: Penny Crompton
Contributors: Ian Gass; John Wright
Publisher: BBC Open University
Keyword(s): Basalts; Contamination; Differentiation; Igneous, metamorphosed and sedimentary; Representative samples; Rock sampling and analysis; X-Ray fluorescence
Footage description: Ian Gass introduces the programme. He has with him a sample of terrestrial and a sample of oceanic basalt. Both samples look alike. Shots of each sample under the microscope. They still look alike. Gass shows a graph on which the major oxides of the above are plotted. This graph shows where the two basalts are significantly different. (Trace elements are not shown on the graph) Gass introduces section on sampling technique for rock specimen. John Wright examines the problem of getting samples of rocks which are really representative of the rocks in that area. He uses a picture of a granite tor as an aid. Wright next shows a picture of an outcrop of pillow lava. He again examines the problem of getting representative samples. Wright next shows a picture of stratigraphic rock formations and continues his discussion ending with a picture of a piece of rock. Wright begins a discussion on the problem of sampling under the sea. Film sequence shows deep sea drilling for rock samples. The technique is explained in the commentary. Wright begins the discussion on the preparation of rock samples for chemical analysis. He has a rock sample with him. The process of preparing the sample is explained by Wright. Shots of machinery which crushes and grinds rock samples. Wright crushes a small sample. He sieves the results. The process is repeated until the sample is reduced to a fine powder. Spoonfuls of this can be used for analysis. Wright demonstrates how the powder can be put into solution. I.G.Gass introduces the section on use of x-ray techniques for rapid analysis. Gass lists the advantages of x-ray over classical technique. R.S.Thorpe explains x-ray, fluorescence technique for chemical analysis of rocks (XRF). He demonstrates the principles of the technique using a simple model. Thorpe uses the model to show how an analysis for silicon would be performed. Gass examines the bar chart for the two samples of basalt, shown at the beginning of the programme. Major element oxides are again shown. The bar chart shows values for the averages of a number of basalt samples. Bar chart of 4 trace elements of basalts. Gass points out the differences between the two samples. He discusses the significance of some of the differences in chemical composition.
Master spool number: 6LT/70272
Production number: 00521_2158
Videofinder number: 1643
Available to public: no