The Hercynian basement: a review

Carboniferous Orogenic Gold Deposits at Pataz, Eastern Andean Cordillera, Peru: Geological and Structural Framework, Paragenesis, Alteration, and 40Ar/39Ar Geochronology

“…19B), with evidence of additional deformation toward the Devonian-Carboniferous boundary ("Eohercynian" orogen in Mégard, 1978;Dalmayrac et al, 1980); (3) a Mississippian-early Pennsylvanian postcollisional environment, characterized successively by voluminous calcalkaline plutonism that gave rise to the Pataz batholith, molasse sedimentation in transtensional basins, and a late period of uplift tectonics ( Fig. 19C-E; Laubacher and Mégard, 1985); and (4) a late Pennsylvanian to Triassic progressive development of intracontinental rifts ( Fig. 19F; Noble et al, 1978;Kontak et al, 1985;Sempere et al, 2002), resulting in the break-up of much of the Gondwana foreland and all the seaward terranes and superimposed early to middle Paleozoic arcs, and most likely the removal of the northwestern part of the Arequipa-Antofalla terrane.…”

“…2;Laubacher and Mégard, 1985). It intrudes the Upper Proterozoic to Lower Cambrian polymetamorphic phyllite basement and its overlying CambroOrdovician volcaniclastic and turbiditic cover sequences along a north-northwest-striking fracture system (Fig.…”

“…A geotectonic interpretation of the proto-Andean margin of northern Peru has been presented by Haeberlin and Fontboté (2004) on the basis of field observations in the Pataz area and the available geologic literature on the Eastern Andean Cordillera (Mégard, 1978;Noble et al, 1978;Dalmayrac et al, 1980;Kontak et al, 1985;Laubacher and Mégard, 1985;Sempere et al, 2002). They propose that the present-day configuration of northern Peru, and particularly the absence in this area of lower and middle Paleozoic arc and fore-arc sedimentary sequences and plutons and allochthonous Paleozoic-accreted terranes north of the Arequipa-Antofalla terrane (i.e., north of 13°S), can be explained by a scenario during which part of the Gondwana fore-arc composed of terranes accreted prior to the Devonian was rifted away from South America during the late Paleozoic (Fig.…”

Evidence of Early to Middle Ordovician arc volcanism in the Cordillera Oriental and Altiplano of southern Peru, Ollantaytambo Formation and Umachiri beds

“…Regional syntheses of potential tectonic settings and the evolution of the Paleozoic basin are based essentially on the cited stratigraphic data and scarce additional sedimentological information. The Early Paleozoic basin in northern Bolivia and southern Peru has been interpreted as an intracontinental and epeiric sea located at the western margin of Gondwana (Dalmayrac et al, 1980;Laubacher and Mégard, 1985;Gohrbrandt, 1992). The plate tectonic setting of this basin is unclear; it has been variably interpreted as an aulacogen, a backarc rift, or a passive margin (Sempéré, 1995;Gohrbrandt, 1992;Keppie and Ramos, 1999).…”

“…In southern Peru, the Ordovician-Devonian successions reach thicknesses of more than 10,000 m (Laubacher and Mégard, 1985). Volcanic rocks are abundant in the Early Ordovician of northwestern Argentina and northern Chile and in the Late Carboniferous and Permian successions of these regions and the entire Carboniferous of southern Peru (Kontak et al, 1985;Bahlburg, 1990;Suarez Soruco, 1992;Sempéré, 1995;Breitkreuz and Van Schmus, 1996;Coira et al, 1999;Zimmermann and Bahlburg, 2003).…”