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The Miocene plutonic event of the Patagonian Batholith at 44° 30′ S: thermochronological and geobarometric evidence for melting of a rapidly exhumed lower crust

  • M. A. Parada (a1), A. Lahsen (a1) and C. Palacios (a1)


The Patagonian Batholith was formed by numerous plutonic events that took place between the Jurassic and the Miocene. North of 47° S, the youngest plutons occupy the axial zone adjacent to the Liquiñe-Ofqui Fault Zone, which is a major intra-arc strike-slip fault system active since the Miocene. The Queulat Complex, located at 44° 30′ S, includes two Miocene plutonic units: the Early Miocene Queulat diorite (QD) and the Late Miocene Puerto Cisnes granite (PCG). The QD includes hornblende + clinopyroxene diorites and tonalites, whereas the PCG includes slightly peraluminous garnet ± sillimanite granites and granodiorites.

Eleven mineral Ar–Ar ages and three apatite fission track ages were obtained from the Queulat Complex and surrounding host rocks. Hornblende and biotite Ar–Ar ages of c. 16-18 Ma and 9-10 Ma, respectively, were obtained for the QD. The youngest ages of the QD are similar to the age of emplacement of the PCG as previously determined. Ar–Ar ages for muscovites and biotites of 6·6 ± 0·3 Ma and 5·6 ± 0·1 Ma, respectively, were obtained for the PCG. Biotites and muscovites from mylonites and pelitic hornfelses adjacent to the PCG yielded Ar—Ar ages between 5·1 Ma and 5·5 Ma. The apatite fission track ages of the QD and PCG overlap within the error margin (2•2 ± 1·1-3·3 ± 1·4 Ma).

The Al-in-hornblende geobarometer yielded pressures for the QD emplacement equivalent to depths in the 19-24 km range, which is substantially higher than the 10 km depth estimated previously for the PCG emplacement. Exhumation rates (v) up to 2·0mm/yr were calculated for the time elapsed between the QD and PCG emplacements. A v value of 1·0mm/yr was calculated for the PCG subsequent to its emplacement. Using the silica—Ca-tschermak-anorthite geobarometer, we estimate the QD magma generation to be at c. 33 km, which is similar to the current crustal thickness. Melting of mafic and metapelitic lower crust was possible at > 30km depth during a period when v was between 1·0mm/yr and 2·0mm/yr.



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Anderson, J. L.& Smith, D. R. 1995. The effect of temperature and oxygen fugacity on Al-in-hornblende barometry. American Mineralogist 80, 549–59.
Beck, M. E. 1992. Some thermal and paleomagnetic consequences of tilting a batholith. Tectonics 11, 297302.
Bourgois, J., Martin, H., Lagabrielle, Y., Le Moigne, J.& Frutos Jara, J. 1996. Subduction-erosion related to ridge-trench collision: Taitao Peninsula (Chile margin triple junction area). Geology 24, 723–26.
Cande, S. C.& Leslie, R. B. 1986. Late Cenozoic tectonics of the southern Chile trench. Journal of Geophysical Research 91, 471–96.
Cembrano, J., Schermer, E., Lavenue, A., Hervé, F., Barrientos, S., McClelland, B.& Arancibia, G. 1996. Nature and timing of Cenozoic intra-arc deformation, southern Chile. Third International Symposium on Andean Geodynamics, StMalo, France, Actas 1, 311–14.
Cloos, M. 1993. Lithospheric buoyancy and collisional orogenesis: Subduction of oceanic plateaus, continental margins, island ares, spreading ridges and seamounts. Geological Society of America Bulletin 105, 715–37.
DeLong, S. E., Schwarz, W. M.& Anderson, R. N. 1979. Thermal effects of ridge subduction. Earth and Planetary Science Letters 44, 239–46.
Drummond, M. S., Defant, M. J.& Kepezhinskas, P. K. 1996. The petrogenesis of slab-derived trondhjemite-tonalite-dacite/adakite magmas. Transactions of the Royal Society of Edinburgh: Earth Sciences 87, 205–16.
Duffield, W. A.& Dalrymple, G. B. 1990. The Taylor Creek rhyolite of New Mexico: A rapidly emplaced field of lava domes and flows. Bulletin of Volcanology 52, 475–87.
England, P.& Molnar, P. 1990. Surface uplift, uplift of rocks and exhumation of rocks. Geology 18, 1173–7.
Fleischer, R. L., Price, P. B.& Walker, R. M. 1975. Nuclear Tracks in Solids: Principles and Applications, 605. Berkeley, CA: University of California Press.
Forsythe, R. D., Nelson, E. P., Carr, M. J. Kaeding, M. E., Hervé, M., Mpodozis, C. M., Soffia, M. J.& Harambour, S. 1986. Pliocene near trench magmatism in southern Chile: A possible manifestation of ridge collision. Geology 14, 2327.
Green, T. H. 1982. Anatexis of mafic crust and high pressure crystallization of andesite. In Thorpe, R. S. (ed.) Andesites, 465–87. Chichester: John Wiley.
Hammarstrom, J. M.& Zen, E-an. 1986. Aluminum in hornblende, an empirical igneous geobarometer. American Mineralogist 71, 1297–313.
Hervé, F., Godoy, E., Parada, M. A., Ramos, V., Rapela, C., Mpodozis, C.& Davidson, J. 1987. A general view on the Chilean–Argentine Andes with emphasis on their early history. In Monger, J. W. H.& Francheteau, J. (eds) Circum-Pacific Orogenic Belts and the evolution of the Pacific Ocean Basin. American Geophysical Union Geodynamic Series 18, 97113. Boulder, Colorado: American Geophysical Union.
Hervé, F., Pankhurst, R. J., Drake, R., Beck, M. E.& Mpodozis, C. 1993. Granite generation and rapid unroofing related to strikeslip faulting, Aysén, Chile. Earth and Planetary Science Letters 120, 375–86.
Hervé, F.& Ota, Y. 1993. Fast Holocene uplift rates at the Andes of Chiloé, southern Chile. Revista Geológica de Chile 20, 1523.
Hickey-Vargas, R., Abdollahi, M. J., Parada, M. A., López-Escobar, L.& Frey, F. A. 1995. Crustal xenoliths from Calbuco Volcano, Andean Southern Volcanic Zone: implications for crustal composition and magma-crust interaction. Contributions to Mineralogy and Petrology 119, 331–44.
Holland, T.& Blundy, J. 1994. Non-ideal interactions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry. Contributions to Mineralogy and Petrology 116, 433–47.
Hurford, A. J.& Green, P. F. 1982. A useŕs guide to fission track dating calibration. Earth and Planetary Science Letters 59, 343–54.
Hurford, A. J.& Green, P. J. 1983. The zeta calibration of fission track dating. Chemical Geology (Isotope Geoscience Section) 1, 285317.
Hutton, D. H. W.& Reavy, R. J. 1992. Strike-slip tectonics and granite petrogenesis. Tectonics 11, 960–67.
Hyndman, D. W.& Foster, D. A. 1988. The role of tonalites and mafic dikes in the generation of the Idaho Batholith. Journal of Geology 96, 3146.
Jäger, E. 1979. Introduction to geochronolgy. In Jäger, E.& Hunziker, J. C. (eds) Isotope Geology, 112. Berlin: Springer.
Johnson, M. C.& Rutherford, M. J. 1989. Experimental calibration on aluminum-in-hornblende geobarometer with application to Long Valley caldera (California) volcanic rocks. Geology 17, 837–41.
Kay, S. M., Ramos, V. A.& Marquez, M. 1993. Evidence in Cerro Pampa volcanic rocks for slab-melting prior to ridge-trench collision in Southern South america. Journal of Geology 101, 703–14.
Liu, M.& Furlong, K. P. 1993. Crustal shortening and Eocene extension in the southeastern Canadian Cordillera: Some thermal and rheological considerations. Tectonics 12, 776–86.
López-Escobar, L. Cembrano, J.& Moreno, H. 1995a. Gechemistry and tectonics of the Southern Andes basaltic Quaternary volcanism (37° 46° S). Revista Geológica de Chile 22, 219–34.
López-Escobar, L., Parada, M. A., Hickey-Vargas, R., Frey, F., Kempton, P.& Moreno, H. 1995b. Calbuco Volcano and minor eruptive centers distributed along the Liquine-Ofqui Fault Zone, Chile (41°-42°S): contrasting origin of audesitic and basaltic magma in the Southern Volcanic Zone of the Andes. Contributions to Mineralogy and Petrology 119, 345–61.
Martin, H. 1999. Adakitic magmas: modern analogues of Archaen granitoids. Lithos 46, 411–29.
McCarthy, T. C.& Patiño Douce, A. E. 1998. Empirical calibration of the silica—Ca-tschermak's—anorthite (SCAn) geobarometer. Journal of Metamorphic Geology 16, 675–86.
Mpodozis, C.& Kay, S. M. 1992. Late Paleozoic to Triassic evolution of the Gondwana margin: evidence from Chilean Frontal Cordilleran batholiths (28° S to 31° S). Geological Society of America Bulletin 104, 9991014.
Murdie, R. E. 1994. Seismicity and neotectonics associated with the subduction of an active Ocean Ridge-transform system in southern Chile. Unpublished Ph.D. Thesis, University of Liverpool.
Nabelek, P. I.& Liu, M. 1999. Leucogranites in the Black Hills of the South Dakota: The consequence of shear heating during continental collision. Geology 27, 523–6.
Nelson, E. P.& Forsythe, R.D. 1989. Ridge collision at convergent margins: implications for Archean and post-Archean crustal growth. Tectonophysics 161, 307–15.
Pankhurst, R. J., Weaver, S. D., Hervé, F.& Larrondo, P. 1999. Mesozoic-Cenozoic evolution of the North Patagonian Batholith in Aysén, southern Chile. Journal of the Geological Society, London 156, 673–94.
Parada, M. A., Nyström, J. O.& Levi, B. 1999 Multiple sources for the Coastal Batholith of central Chile (31-34° S): geochemical and Sr-Nd isotopic evidence and tectonic implications. Lithos 46, 505–21.
Pardo-Casas, F.& Molnar, P. 1987. Relative motion of the Nazca (Farallon) and South American plates since Late Cretaceous time. Tectonics 6, 233–48.
Patiño Douce, A. E.& Beard, J. S. 1995. Dehydration melting of biotitegneiss and quartz amphibolite from 3 to 15kbarar. Journal of Petrology 36, 707–38.
Petford, N.& Atherton, M. 1996. Na-rich partial melts from newly underplated basaltic crust: the Cordillera Blanca batholith, Peru. Journal of Petrology 36, 891931.
Ramos, V.& Kay, S. M. 1992. Southern Patagonian plateau basalts and deformation: backarc testimony of ridge collisions. Tectonophysics 205, 261–82.
Rapp, R.& Watson, E. B. 1995. Dehydration melting of metabasalt at 8-32 kbarar: Implications for continental growth and crust-mantle recycling. Journal of Petrology 36, 891931.
Schmidt, M. W. 1992. Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al-in-hornblcnde barometer. Contributions to Mineralogy and Petrology 110, 304–10.
Sial, A. N., Toselli, A. J. Saavedra, J., Parada, M. A.& Ferreira, V. P. 1999. Emplacement, petrological and magnetic susceptibility characteristics of diverse magmatic epidote-bearing granitoid rocks in Brazil, Argentina and Chile. Lithos 46, 367–92.
Spear, F. S.& Cheney, J. T. 1989. A petrogenetic grid for pelitic schists in the system SiO2-Al2O3-FeO-MgO-K2O-H2O. Contributions to Mineralogy and Petrology 101, 149–64.
Stern, C. R.& Kilian, R. 1996. Role of the subducted slab, mantle wedge and continental crust in the generation of adakites from the Austral Volcanic Zone. Contributions to Mineralogy and Petrology 123, 263–81.
Strong, D. F.& Hanmer, S. K. 1981. The leucogranites of southern Brittany: origin by faulting, frictional heating, fluid flux and fractional melting. Canadian Mineralogist 19, 163–76.
Stüwe, K.& Barr, T. D. 1998. On uplift and exhumation during convergence. Tectonics 17, 80–8.
Thiele, R., Hervé, F., Parada, M. A.& Godoy, E. 1986. La megafalla Liquiñe-Ofqui en el Fiordo Reloncaví (41° 30' S), Chile. Comunicaciones 37, 3147.
Thompson, A. B.& England, P. C. 1984. Pressure-temperature-time paths in regional metamorphism II. The significance and interpretation using mineral assemblages in metamorphic rocks. Journal of Petrology 25, 929–55.
Zeitler, P. K.& Chamberlain, C. P. 1991. Petrogenetic and tectonic significance of young leucogranites from the northwestern Himalaya, Pakistan. Tectonics 10, 729–41.



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