Geodynamic evolution of the Early Paleozoic Gondwana margin in southern Peru and northern Bolivia – sedimentary facies and provenance analysis of the Ordovician basin in Cordillera Oriental and…

The Early Paleozoic sedimentary basins of southern Peru developed between the Arequipa Massif basement block in the west and the Amazon craton to the east. Even though it has recently been established that the Orodivician basin evolved behind an arc on the Arequipa Massif, a number of questions considering the plate tectonic evolution of this part of the Gondwana margin remain unresolved: There is no known “post-Grenville” Neoproterozoic geochronologic record contained in the Arequipa Massif, therefore its geodynamic history between 1000 and 470 Ma is unknown. The stratigraphic evidence of Ordovician volcanism is limited, outcrops and known ages of intrusive rocks are few, the duration of Ordovician magmatism is ill defined. Likewise, there is no evidence of Devonian volcanism, dated intrusive rocks are very scarce, and the tectonic setting of the coeval basin is undetermined.- Information addressing these problems is stored in the detritus of the Ordovician to Devonian siliciclastic strata. We will apply LA-ICP-MS analysis of detrital zircons to establish a better defined geochronological record of the activity or absence of Neoproterozoic and Early Paleozoic magmatism in southern Peru. The geochemical anlysis of detrital rutiles will help to discriminate between metamafic and metapelitic source rocks, and to further evaluate the influence of variable recycling paths on the composition of the studied deposits. The combination of data will result, for the first time, in a data-based determination of the evolution of the Neoproterozoic and Early Paleozoic Gondwana margin in southern Peru in plate-tectonic terms.