Grenvillian (?) suture zones identified in the northern portion of the Cuyania terrane, Argentina: geophysical evidence.

CHERNICOFF, C.J., VUJOVICH, G.I.

Mendoza

Conferencia; Gondwana 12 "Geological and Biological Heritage of Gondwana"; 2005

Academia Nacional de Ciencias

In the northern portion of the Cuyania terrane there is geophysical evidence for the occurrence of two ancient (Grenvillian ?) WNW-oriented suture zones, corresponding to the Guandacol and Vinchina lineaments (Chernicoff and Nash, 2001; Chernicoff and Vujovich, 2004a, 2004b). The location of these sutures is consistent with the presence of analogous structures in Laurentia, in the region of the Ouachita embayment, from where the Cuyania terrrane is though to have been rifted and drifted, before colliding with Gondwana; see e.g. Thomas and Astini, 2003). The said structures assemblage pre- (or early) Grenvillian cratonic nuclei in the Ouachita embayment area (cf. Mosher, 1998; Bickford et al., 2000); in that zone the Grenville orogen is parallel to the WNW orientation. It is argued that the WNW transform faults pertaining to the Ouachita rift would have developed as a result of a reactivation of compressional structures (thrust belts) of identical orientation associated to the accretion of ancient terranes (comparing figures 1 and 2 of Thomas, 1991, it becomes apparent that the Alabama-Oklahoma transcurrent fault resulted from the reactivation of the Ouachita thrust belt, responsible for the juxtaposition of rock units of contrasting tectonic environments at the end of the Proterozoic and beginning of the Palaeozoic). The Guandacol and Vinchina lineaments stand out as major pattern breaks in the aeromagnetic and gravimetric data. Ongoing geophysical investigation tends to confirm the physical continuity between the latter lineaments and the analogous megastructures in the Ouachita embayment. Finally, the interpretation of the Guandacol and Vinchina lineaments as Grenvillian suture zones would add more complexity to the Cuyania terrane, with respect to what has been described up to now, i.e. they would precede the amalgamation of the Pie de Palo and Precordillera basement blocks (constituents of the Cuyania composite terrane; Ramos et al., 1998).   Bickford, M.E., Soegaard, K., Nielsen, K.C., and McLelland, J.M., 2000, Geology and geochronology of Grenville-age rocks in the Van Horn and Franklin Mountains area, west Texas: Implications for the tectonic evolution of Laurentia during the Grenville: Geological Society of America, Bulletin, v. 112, p. 1134-1148. Chernicoff, C.J., and Nash, C.R., 2001, Geological interpretation of Landsat TM imagery and aeromagnetic survey data, northern Precordillera region, Argentina: Journal of South American Earth Sciences, v. 15, p. 813-820. Chernicoff, C.J., and Vujovich, G.I., 2004a, Megaestructuras identificadas en el sector septentrional del basamento del terreno Cuyania a partir de datos geofísicos: su interpretación como antiguas (¿1000-1200 Ma?) zonas de sutura: 22 Reunión Científica de Geofísica y Geodesia, Article. 5 pp. Chernicoff, C.J., and Vujovich, G.I., 2004b, Zonas de sutura grenvilianas identificadas en la porción septentrional del terreno Cuyania, República Argentina, a partir de datos geofísicos: 4 Congreso Uruguayo de Geología. Article No. 5. 9 pp. Mosher, S., 1998, Tectonic evolution of the southern Laurentian Grenville orogenic belt: Geological Society of America, Bulletin, v. 110, p. 1357-1375. Ramos, V.A., Dallmeyer, D., and Vujovich, G.I., 1998, Time constraints on the Early Palaeozoic docking of the Precordillera, central Argentina, in Pankhurst, R.J., and Rapela, C.W., eds., The Proto-Andean Margin of Gondwana: Geological Society of London, Special Publication 142, p. 143-158. Thomas, W.A., 1991, The Appalachian-Ouachita rifted margin of the southwestern North America: Geological Society of America Bulletin, v. 103, 415-431. Thomas, W.A., and Astini, R.A., 2003, Ordovician accretion of the Argentine Precordillera terrane to Gondwana: a review: Journal of South American Earth Sciences, v. 16, p. 67-79.