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The Iglesia Irca intrusion and the role of gas brecciation in the emplacement of the Coastal Batholith of Peru

Published online by Cambridge University Press:  01 May 2009

M. A. Bussell  and
W. J. McCourt
M. A. Bussell
Affiliation:
Department of Biology and Geology, The Polytechnic of North London, London N7 8DB
W. J. McCourt
Affiliation:
Institute of Geological Sciences, Murchison House, West Mains Road, Edinburgh.
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Summary

In the Iglesia Irca intrusion early undifferentiated pulses of granitic magma were emplaced at pressures of approximately 1 kb as narrow dykes of vesicular felsite. These dykes are associated with penecontemporaneous burst breccias and gas breccias and are themselves sometimes brecciated. Subsequently a large dyke of granophyre, representing a more fractionated composition, was emplaced by subsidence and stoping along the line of earlier microbreccias, explosion breccias and felsites. The dyke cooled relatively slowly at low structural levels and retained its volatiles while at higher levels more rapid cooling accompanied the greater escape of volatiles. This resulted in marked potassium enrichment of the upper levels of the dyke and the country rocks of the hanging wall. It is argued that the Iglesia Irca intrusion provides an example of the association of gas brecciation with vesiculating and volatile-rich magma which is atypical of the Coastal Batholith as a whole.

Type
Articles
Information
Geological Magazine , Volume 114 , Issue 5 , September 1977 , pp. 375 - 387
Copyright
Copyright © Cambridge University Press 1977

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References

Atherton, M. P. & Brenchley, P. J. 1972. A preliminary study of the structure, stratigraphy and metamorphism of some contact rocks of the western Andes, near the Quebrada Venado Muerto, Peru. Geol. J. 99, 161–78.CrossRefGoogle Scholar
Barker, D. S. 1970. Composition of granophyre, myrmekite and graphic granite. Bull. geol. Soc. Am. 81, 3339–50.CrossRefGoogle Scholar
Barrington, J. & Kerr, P. F. 1961. Breccia pipe near Cameron, Arizona. Bull. geol. Soc. Am. 72, 1661–74.CrossRefGoogle Scholar
Bennet, F. D. 1974. On volcanic ash formation. Am. J. Sci. 274, 648–61.CrossRefGoogle Scholar
Bowes, D. R. & Wright, A. E. 1960. An explosion breccia complex at Back Settlement, near Kentallen, Argyll. Trans. Edinb. geol. Soc. 18, 293–314.CrossRefGoogle Scholar
Brown, G. M. 1963. Melting relations of Tertiary granitic rocks in Skye and Rhum. Mineralog. Mag. 33, 533–62.Google Scholar
Bussell, M. A. 1976. Fracture control of high level plutonic contacts in the Coastal Batholith of Peru. Proc. Geol. Ass. 87, 237–46.CrossRefGoogle Scholar
Bussell, M. A., Pitcher, W. S. & Wilson, P. A. 1976. Ring complexes of the Peruvian Coastal Batholith: a long standing sub-volcanic regime. Can. J. Earth Sci. 13, 1020–30.CrossRefGoogle Scholar
Carmichael, I. S. W., Turner, F. J. & Verhoogen, J. 1974. Igneous Petrology. McGraw-Hill.Google Scholar
Cobbing, E. J. & Pitcher, W. S. 1972(a). The Coastal Batholith of Central Peru. Jl geol. Soc. Lond. 128, 421–60.CrossRefGoogle Scholar
Cobbing, E. J. & Pitcher, W. S. 1972(b). Plate tectonics and the Peruvian Andes. Nature, Lond. 240, 51–3.Google Scholar
Dunham, A. C. 1965. The nature and origin of the groundmass textures in felsites and granophyres from Rhum, Inverness-shire. Geol. Mag. 102, 8–23.CrossRefGoogle Scholar
Dunham, A. C. 1967. The felsites, granophyre, explosion breccias and tuffisites of the north-east margin of the Tertiary igneous complex of Rhum, Inverness-shire. Q. Jl geol. Soc. Lond. 123, 327–52.CrossRefGoogle Scholar
Gates, O. 1959. Breccia pipes in the Shoshone range, Nevada. Econ. Geol. 54, 790–815.CrossRefGoogle Scholar
Higgins, M. W. 1971. Cataclastic rocks. Prof. Pap. U.S. geol. Surv. 687, 1–97.Google Scholar
Hughes, C. J. 1960. The Southern Mountains igneous complex, Isle of Rhum, Q. Jl geol. Soc. Lond. 116, 111–31.CrossRefGoogle Scholar
Hughes, C. J. 1971. Anatomy of a granophyre intrusion. Lithos 4, 403–15.CrossRefGoogle Scholar
Jahns, R. H., Martin, R. F. & Tuttle, O. F. 1969. Origin of granophyre in dikes and sills of tholeitic diabase. Trans. Am. geophys. Un. 50, 337.Google Scholar
Jahns, R. H. & Tuttle, O. F. 1963. Layered pegmatite—aplite intrusives. Spec. Pap. Mineral. Soc. Am. 1, 78–92.Google Scholar
James, R. S. & Hamilton, D. L. 1969. Phase relations in the system NaAl—Si3O8—KAlSi3O8—.CaAl2Si2O8—SiO2 at I kilobar water vapour pressure. Contrib. Mineral. Petrol. 21, 111–41.CrossRefGoogle Scholar
Knox, G. J. 1974. The structure and emplacement of the Rio Fortaleza centred acid complex, Ancash, Peru. Jl geol. Soc. Lond. 130, 295–308.CrossRefGoogle Scholar
Lacey, E. D. 1960. Melts of granitic composition, their structure, properties and behaviours. 21st Int. geol. Cong. Norden Pt. 14, 7–15.Google Scholar
Myers, J. S. 1975. Cauldron subsidence and fluidisation: mechanisms of intrusion of the Coastal Batholith of Peru into its own volcanic ejecta. Bull. geol. Soc. Am. 86, 1209–20.2.0.CO;2>CrossRefGoogle Scholar
Orville, P. M. 1960. Petrology of several pegmatites in the Keystone district, Black Hills, South Dakota. Bull geol. Soc. Am. 71, 1467–90.CrossRefGoogle Scholar
Schloemer, H. 1964. Synthetic hydrothermal co-crystallisation of orthoclase and quartz. Geochemistry, Wash. 3, 578–612.Google Scholar
Stewart, J. W., Evernden, J. F. & Snelling, N. J. 1974. Age determinations from Andean Peru: a reconnaissance survey. Bull. geol. Soc. Am. 85, 1107–16.2.0.CO;2>CrossRefGoogle Scholar
Vogt, J. H. L. 1921. Magmatic differentiation in igneous rocks. J. Geol. 29, 318–50.CrossRefGoogle Scholar