W. C. B. Masero and S. L. Fontes, “Geoelectrical Studies of the Col?nia Impact Structure, Santo Amaro, State of S?o Paulo—Brazil,” Revista Brasileira de Geofísica, Vol 10, No. 5, 1992, pp. 25-41.

has been cited by the following article:

• TITLE: Evidence of Shock Metamorphism Effects in Allochthonous Breccia Deposits from the Colônia Crater, São Paulo, Brazil

  AUTHORS: Victor F. Velázquez, Claudio Riccomini, José M. Azevedo Sobrinho, Mikhaela A. J. S. Pletsch, Alethéa E. Martins Sallun, William Sallun Filho, Jorge Hachiro

  KEYWORDS: Colônia Crater; Polymictic Allochthonous Breccia; Shock Metamorphism Effects

  JOURNAL NAME: International Journal of Geosciences, Vol.4 No.1A, January 29, 2013

  ABSTRACT: The 3.6 km-diameter Colonia impact crater, centred at 2352'03"S and 4642'27"W,lies 40 km to the south-west of the S?o Paulo city. The structure was formed on the crystalline basement rocks and displays a bowl-shaped with steeper slope near the top that decreases gently toward the centre of the crater. Over recent years were drilled two boreholes inside the crater, which reached a maximum depth of 142 m and 197 m. Geological profile suggests four different lithological associations: 1) unshocked crystalline basement rocks (197 - 140 m); 2) fractured/brecciated basement rocks (140 - 110 m); 3) polymictic allochthonous breccia deposits (110 - 40 m); and 4) post-impact deposits (40 - 0 m). Petrographic characterisation of the polymictic allochthonous breccia reveals a series of distinctive shock-metamorphic features, including, among others, planar deformation features in quartz, feldspar and mica, ballen silica, granular texture in zircon and melt-bearing impact rocks. The occurrence of melt particles and very high-pressure phase transformation in suevite breccia suggest a shock pressure regime higher than 60 GPa.