Dewar, G. J. (1970) The geology of Adelaide Island. British Antarctic Survey Scientific Reports 57. British Antarctic Survey
| Reference Type | Report (issue) | ||
|---|---|---|---|
| Title | The geology of Adelaide Island | ||
| Report | British Antarctic Survey Scientific Reports | ||
| Authors | Dewar, G. J. | Author | |
| Year | 1970 | ||
| Issue | < 57 > | ||
| Publisher | British Antarctic Survey | Place | Cambridge |
| URL | |||
| Download URL | https://nora.nerc.ac.uk/id/eprint/509252/1/The%20geology%20of%20Adelaide%20Island%20-%20BAS%20Scientific%20Report%2062.pdf?reftype=.pdf | ||
| Classification | Not set | LoC | Not set |
| Mindat Ref. ID | 19883628 | Long-form Identifier | mindat:1:5:19883628:7 |
| GUID | 0 | ||
| Full Reference | Dewar, G. J. (1970) The geology of Adelaide Island. British Antarctic Survey Scientific Reports 57. British Antarctic Survey | ||
| Plain Text | Dewar, G. J. (1970) The geology of Adelaide Island. British Antarctic Survey Scientific Reports 57. British Antarctic Survey | ||
| In | British Antarctic Survey - British Antarctic Survey Scientific Reports | ||
| Abstract/Notes | Some aspects of the geology of Adelaide Island and adjacent islands are described and discussed. A flatlying succession of volcanic, sedimentary and mixed strata has been intruded by many superstructure plutons of the Andean Intrusive Suite, and mafic dykes have been intruded both before and after the Andean plutons. In the stratified rocks, which are probably of Upper Jurassic age, a succession of lavas separates two successions of volcaniclastic and sedimentary rocks; about 10,000 ft. (3,050 m.) of the stratified rocks are exposed on Adelaide Island. The lavas are spilitic in parts. A succession of devitrified rhyolites is exposed in north-eastern Square Peninsula but similar rocks have not been found elsewhere. Some conglomerates in a sedimentary succession contain boulders of ancient plutonic and metamorphic rocks which have not been found in situ in the Adelaide Island area. The Andean intrusive rocks, which range from olivine-gabbro to adamellite and appear to have been intruded strictly in that order, have not forcibly displaced the stratified rocks. Although the effects of thermal metamorphism are not noticeable in the field, recrystallization and some redistribution of minerals have taken place in the country rocks near Andean plutons. A number of these plutons are heterogeneous and are composed of rocks ranging from gabbros to granodiorites, although there are no contacts within them. These rocks are not otherwise abnormal, because geochemical investigations have shown that they follow the variation trends which are typical of the Andean Intrusive Suite. Assimilation may have been an important process in the emplacement of these heterogeneous plutons. Analyses of four dark gabbros from the Adelaide Island area show that they, like other gabbros from the Antarctic Peninsula, have crystallized from two contrasting magmas; three have crystallized from a parental magma which has been enriched in cumulative olivine and the other one from a magma from which cumulative plagioclase has been removed. Three separate post-Andean phases of mafic dyke intrusion have been distinguished on Jenny Island, where also an unusual hypabyssal intrusion of a low-temperature suspension of lithic fragments has been emplaced at the contacts between two Andean gabbros and the stratified country rocks. Another unusual hypabyssal complex on Square Peninsula contains both tholeiitic and alkaline basalts; the latter is the earlier and it contains pyroxenite inclusions. The two basalts are separated by harrisitic layers. In southern Square Peninsula restricted exposures are of sedimentary and volcaniclastic rocks which are rich in introduced magnetite. Block-faulting has had an important structural influence in the Adelaide Island area, and the most prominent faults strike parallel to the local trend of the Antarctic Peninsula. Joints, common to both the Andean intrusive rocks and the Jurassic stratified rocks, have formed on the removal of overburden. | ||
Locality Pages
| Locality | Citation Details |
|---|---|
| Adelaide Island, West Antarctica, Antarctica |
Mineral Occurrences
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