The value of measurements of density in the study of dolerites
- 1 January 1964
- journal article
- research article
- Published by Taylor & Francis in Journal of the Geological Society of Australia
- Vol. 11 (1), 133-140
- https://doi.org/10.1080/00167616408728564
Abstract
The value of density measurements in the study of differentiated dolerite sills is discussed. It is shown that density measurements correspond closely with the results of chemical and modal analyses. There is a considerable statistical fluctuation in measured values of the density from relatively close specimens, and a similar fluctuation is to be expected in the results of chemical or modal analyses. Because of their speed, it is possible to make a large number of density measurements and take mean values over fifty foot intervals to indicate trends. The density in a moderately thick tholeiite sheet normally increases linearly from the lower contact to a maximum several hundred feet above it, and then decreases to a minimum at the most silicic region which usually occurs several hundred feet below the upper contact. For a sheet of uniform thickness, the variation of density with depth appears to be roughly the same at all points. The density remained constant in a horizontal tunnel at a constant height above the lower contact, but irregular changes in density, possibly associated with changes in level of the roof or flow can occur, and a remarkable case of a rapid horizontal variation in density is discussed in some detail.Keywords
This publication has 5 references indexed in Scilit:
- Differentiation of the great lake dolerite sheet, TasmaniaJournal of the Geological Society of Australia, 1964
- THREE-DIMENSIONAL SPECIFIC-GRAVITY VARIATION IN THE GLEN ALPINE STOCK, SIERRA NEVADA, CALIFORNIAGSA Bulletin, 1962
- Rock Magnetism and the Differentiation of Dolerite SillJournal of the Geological Society of Australia, 1954
- Differentiation of the Dolerites of Tasmania. IThe Journal of Geology, 1942
- Differentiation of the Palisade diabase, New JerseyGSA Bulletin, 1940