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| Titel: |
Rock magnetism and the differentiation of dolerite sill |
| Auteur: |
Jaeger, J. C. Joplin, Germaine |
| Verschenen in: |
Australian journal of earth sciences |
| Paginering: | Jaargang 2 (1954) nr. 1 pagina's 1-19 |
| Jaar: |
1954 |
| Inhoud: |
Measurements of intensity of magnetization and susceptibility have been made at intervals of 5 ft. on some bore cores from Tasmanian tholeiites of Jurassic age. In all cases the direction of magnetization was nearly vertical. One sill appears to have its upper 700 ft. magnetized normally and its lower part reversed. The magnetic properties vary very rapidly and show a structure in which narrow regions with high values are superposed on a general increase to a maximum at about 300 ft. from the top of the sill. This coincides with a minimum of the density and a maximum of normative magnetite and total iron and also in the size of the areas of mesostasis. It is suggested that this behaviour is due to differentiation and that magnetic measurements form an extremely sensitive tool for the study of this process. An attempt is made to show that differentiation by the settling of individual crystals through the sill is impossible in thick sills in which convection does not occur, and that the mechanism must be one of roof stoping in which large blocks of mixed crystals and residual magma fall from the roof to the floor of the sill. The regions with exceptionally high magnetic values which have been observed are regarded as composed of magma trapped between these blocks. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
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