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A Late Mesozoic island arc in the southern Andes, Chile

Published online by Cambridge University Press:  01 May 2009

M. Suárez
M. Suárez
Affiliation:
Instituto de Investigaciones Geológicas, Agustinas 785–6° Piso, Santiago, Chile
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Summary

The Hardy Formation, a sequence of Upper Mesozoic volcanic rocks exposed in Peninsula Hardy (Isla Hoste) in the southernmost archipelago of Chile represents, at least in part, the island-arc assemblage of an island-arc-marginal-basin system related to an eastward dipping subduction zone. This island arc was founded on South American continental crust and is also represented in the island of South Georgia 2000 km to the E. The island-arc assemblage includes pyroclastic rocks, characterized by a high proportion of vitric material, and lava intercalations ranging in composition from rhyolite to basalt. These rocks underwent zeolite and prehnite-pumpellyite facies metamorphism and are gently folded, in contrast with the intense folding exhibited by the rocks exposed to the north of Peninsula Hardy. Silicic volcanics assigned to this assemblage underlie pillow lavas, and are intruded by dolerites and gabbros probably related to a Late Jurassic-Early Cretaceous ophiolite magmatism associated with the generation of a quasioceanic marginal basin. Volcanic turbidites (Yahgan Formation) were deposited into the marginal basin.

It is suggested that in pre-marginal basin times the Hardy Formation interfingered towards the Atlantic with the silicic volcanics of the Tobifera Formation. However, recent geochemical work on the Tobifera Formation suggest an origin by continental crust anatexis in a volcano-tectonic rift zone related to upper mantle diapirism, whereas an island arc origin is favoured for at least the andesitic and basaltic components of the Hardy Formation. Therefore, the geology of Peninsula Hardy as presented here, confirms early assumptions of the splitting apart of a Middle–Upper Jurassic volcanic terrain along the Pacific margin of South America during the generation of a marginal basin. The spreading axis of the latter seems to have been located at the boundary of two somewhat overlapping petrotectonic assemblages: and island arc on the Pacific side and a silicic volcano-tectonic rift zone towards the Atlantic. A probably Cenozoic volcanic complex discordantly overlies the Yahgan and Hardy formations.

Type
Articles
Information
Geological Magazine , Volume 116 , Issue 3 , May 1979 , pp. 181 - 190
Copyright
Copyright © Cambridge University Press 1979

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References

Bruhn, R. L. & Dalziel, I. W. D. 1977. Destruction of the Early Cretaceous marginal basin in the Andes of Tierra del Fuego. In Maurice Ewing Series, vol. 1: Island Arcs, Back-arc Basins and Deep Sea Trenches (ed. Talwani, M. and Pitman, W. C.), pp. 395–405. American Geophysical Union.Google Scholar
Bruhn, R. L., Stern, Ch. R. & de Wit, M. (in the press). New field and geochemical data bearing on the development of a Mesozoic volcano–tectonic rift zone and back-arc basin in southernmost South America. Earth Planet. Sci. Lett.Google Scholar
Dalziel, I. W. D. 1974. Evolution of the margins of the Scotia Sea. In The Geology of Continental Margins (eds Burk, C. A. & Drake, C. L.), pp. 567–79. New York: Springer-Verlag.CrossRefGoogle Scholar
Dalziel, I. W. D. (in the press). The Early (pre-Middle Jurassic history of the Scotia Arc region: a review and progress report. In Proceedings on Antarctic Geology and Geophysics (ed. C., Craddock). Madison: University of Wisconsin.Google Scholar
Dalziel, I. W. D. & Cortés, R. 1972. Tectonic style of the southernmost Andes and the Antarctandes. 24th Int. geol. Congress, Montreal, sect. 3, pp. 316–27.Google Scholar
Dalziel, I. W. D., de Wit, M. J. & Palmer, K. F. 1974. Fossil marginal basin in the southern Andes. Nature, Lond. 250, 291–4.CrossRefGoogle Scholar
Dalziel, I. W. D., Dott, R. H. Jr, Winn, R. D. & Bruhn, R. L. 1975. Tectonic relations of South Georgia island to the southernmost Andes. Bull. geol. Soc. Am. 86, 1034–40.2.0.CO;2>CrossRefGoogle Scholar
Dalziel, I. W. D., de Wit, M. J. & Ridley, W. I. 1975. Structure and Petrology of the Scotia Arc and the Patagonian Andes: R/V HERO cruise 75–4. Antarct. J. U.S. 10 307–10.Google Scholar
Dott, R. H. Jr., Winn, R. D., de Wit, M. J. & Bruhn, R. L. 1977. Tectonic and sedimentary significance of Cretaceous Tekenika Beds of Tierra del Fuego. Nature, Lond. 266, 620–22.CrossRefGoogle Scholar
Dott, R. H. Jr., Winn, R. D. & Smith, C. H. L. (in the press). Relationship of Late Mesozoic and Early Cenozoic sedimentation to the tectonic evolution of the southernmost Andes and Scotia Arc. In Proceedings on Antarctic Geology and Geophysics (ed. C., Craddock). Madison: University of Wisconsin.Google Scholar
Fiske, R. S. & Matsuda, T. 1964. Submarine equivalents of ash flows in the Tokiwa Formation, Japan. Am. J. Sci. 262, 76–106.CrossRefGoogle Scholar
González, O. 1972. Distribution, migration and tectonic control of Upper Cenozoic volcanism in west Antarctica and South America. In Antarctic Geology and Geophysics (ed. Adie, R. J.), pp. 173–79. Oslo Universitetsforlaget.Google Scholar
Halle, T. G. 1913. Plant-bearing deposit at Bahia Tekenika, Tierra del Fuego. K. svenska VetenskAkad. Handl. 51, 1–58.Google Scholar
Halpern, M. 1973. Regional geochronology of Chile south of 50° latitude. Bull. geol. Soc. Am. 84, 2407–22.2.0.CO;2>CrossRefGoogle Scholar
Katz, H. R. 1972. Plate tectonics and orogenic belts in the south-Pacific. Nature, Lond. 237, 331–2.CrossRefGoogle Scholar
Katz, H. R. 1973. Contrasts in tectonic evolution of orogenic belts in the south-east Pacific. J. R. Soc. N.Z. 3, 333–61.CrossRefGoogle Scholar
Katz, H. R. & Watters, W. A. 1966. Geological investigation of the Yahgan Formation (upper Mesozoic) and associated igneous rocks of Navarino Island, southern Chile. N.Z. Jl. Geol. Geophys. 9, 323–59.CrossRefGoogle Scholar
Kranck, E. H. 1932. Geological investigations in the Cordillera of Tierra del Fuego. Acta geogr., Helsingf. 4.Google Scholar
Mortimore, R. N. (in the press). Distal and proximal turbidites at Nilse Hullet, western South Georgia. Bull. Br. Antarct. Surv.Google Scholar
Pearce, J. A. & Cann, J. R. 1973. Tectonic setting of basic volcanic rocks determined by using trace element analysis. Earth Planet. Sci. Lett. 19, 290–300.CrossRefGoogle Scholar
Saunders, A. D., Tarney, J., Stern, C. R. & Dalziel, I. W. D. 1978. Geochemistry of Mesozoic marginal basin floor igneous rocks from Southern Chile. Bull. geol. Soc. Am. 10.Google Scholar
Stern, C. R., de Wit, M. J. & Lawrence, J. R. 1976. Igneous and metamorphic processes associated with the formation of the chilean ophiolites and their implications for ocean floor metamorphism, seismic layering and magnetism. J. geophys. Res. 81, 4370–80.CrossRefGoogle Scholar
Storey, B. C., Mair, B. F. & Bell, C. M. 1977. The occurrence of Mesozoic ocean floor and ancient continental crust on South Georgia. Geol. Mag. 114, 203–8.CrossRefGoogle Scholar
Suárez, M. 1977. Aspectos geoquimicos acerca del Batolito Patagónico. Rev. Geol. Chile 4, 15–33.Google Scholar
Suárez, M. & Pettigrew, T. H. 1976. An Upper Mesozoic island-arc system in the southern Andes and South Georgia. Geol. Mag. 113, 305–28.CrossRefGoogle Scholar
Tanner, P. W. G. (in the press). Geological evolution of South Georgia. In Proc. Antarct. Geol. Geophys (ed. C., Craddock). Madison: University of Wisconsin.Google Scholar
Tarney, J. Saunders, A. D. & Weaver, S. D. 1977. Geochemistry of island arc and marginal basin volcanics in the Scotia Arc. In Maurice Ewing Series, Vol 1. Island arcs, Back-arc Basins and Deep Sea Trenches (ed. M., Talwani and Pitman, W. C.), pp. 367–77. American Geophysical Union.Google Scholar
Watters, W. A. 1965. Prehnitization in the Yahgan Formation of Navarino Island, southernmost Chile. Mineralog. Mag. 34, 517–27.Google Scholar