Daly, Reginald A., Barth, Tom F. W. (1930) Dolerites Associated with the Karroo System, South Africa. Geological Magazine, 67 (3) 97-110 doi:10.1017/s001675680009899x
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Dolerites Associated with the Karroo System, South Africa | ||
| Journal | Geological Magazine | ||
| Authors | Daly, Reginald A. | Author | |
| Barth, Tom F. W. | Author | ||
| Year | 1930 (March) | Volume | 67 |
| Page(s) | 97-110 | Issue | 3 |
| Publisher | Cambridge University Press (CUP) | ||
| DOI | doi:10.1017/s001675680009899x | ||
| Mindat Ref. ID | 245783 | Long-form Identifier | mindat:1:5:245783:7 |
| GUID | be9a9237-a760-4dc5-9e1b-69cc7f05573c | ||
| Full Reference | Daly, Reginald A., Barth, Tom F. W. (1930) Dolerites Associated with the Karroo System, South Africa. Geological Magazine, 67 (3) 97-110 doi:10.1017/s001675680009899x | ||
| Plain Text | Daly, Reginald A., Barth, Tom F. W. (1930) Dolerites Associated with the Karroo System, South Africa. Geological Magazine, 67 (3) 97-110 doi:10.1017/s001675680009899x | ||
| In | (1930, March) Geological Magazine Vol. 67 (3) Cambridge University Press (CUP) | ||
| Abstract/Notes | Summary—The field impression of a high degree of uniformity in the composition of the intrusive Karroo dolerites over a vast area is confirmed by new chemical and microscopical studies. The pyroxene characteristic of the dolerites is a typical pigeonite, which, however, does not display any twinning on (100). The plagioclase is potash-free, usually a labradorite, but it has been observed that a homogeneous crystal of plagioclase may be in twin position to another homogeneous crystal of a very differently composed plagioclase. The close resemblance of the doleritic liquid to the artificial liquid taken by Bowen to represent basaltic liquid is noted, and his conclusion that pyroxene and feldspar should crystallize simultaneously in natural basaltic liquid is confirmed.Conceivably the doleritic liquid was quite original and not a differentiate of any earlier liquid. However, analogies like those with the tholeiites and similar hypabyssal rocks of Great Britain suggest that in South Africa, as in Great Britain, the liquids of these hypabyssal rocks were derived from the slightly more femic plateau-basalt.On that assumption the question of the mode of differentiation arises. The fractional crystallization of plateau-basalt, as now described by Bowen and other leaders, does not appear competent to explain the abnormally low soda of one of the analyzed dolerites, nor the excess of soda and total alkalies in plateau-basalt respectively over the soda and total alkalies of the Karroo dolerite. Further, the settling-out of early olivine does not explain the excess of (total) FeO in plateau-basalt over the (total) FeO in the Karroo dolerite. The actual relations indicate the need of renewed examination of the theory of magmatic differentiation by crystal-fractionation. In any case many more data are required before it is possible to decide upon the precise relation of the Karroo dolerite to a parental magma. Possibly such additions to knowledge may annul present difficulties in the way of accounting for the composition of the dolerite. | ||
References Listed
These are the references the publisher has listed as being connected to the article. Please check the article itself for the full list of references which may differ. Not all references are currently linkable within the Digital Library.
| Washington (1922) Bull. Geol. Soc. America xxxiii, 797 | |
| Winchell (1900) Amer. Geol. xxvi, 199 | |
| (1921) Miner. Mag. xix, 139 | |
| Bowen (1928) The Evolution of the Igneous Rocks , 66 | |
| Fenner (1929) Amer. Journ. Science xviii, 238 | |
| Bailey (1924) Mem. Geol. Survey Scotland Tertiary and Post-Tertiary Geology of Mull, etc. , 31 | |
| Bowen (1928) The Evolution of the Igneous Rocks , 75 | |
| Prior (1910) Ann. Natal Museum ii | |
| Not Yet Imported: American Journal of Science - journal-article : 10.2475/ajs.s5-18.105.225 If you would like this item imported into the Digital Library, please contact us quoting Journal ID 4057 | |
| du Toit (1926) The Geology of South Africa , 283 | |
| Winchell (1927) Elements of Optical Mineralogy , 181 |
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