Multi-sample detrital zircon provenance variation within a single turbidite complex – The Ordovician Puna Turbidite Complex in the Puna retroarc foreland basin of northwestern Argentina

Bahlburg, H; Zimmermann, U

Abstract

The Ordovician Puna retroarc foreland basin in northwestern Argentina accommodated the c. 3500 m thick Puna Turbidite Complex consisting of the Lower and Upper Turbidite systems. The turbidites accumulated in the Middle Ordovician over 15 Myr. 744 new detrital zircon U-Pb ages obtained from seven medium and fine-sand turbidite layers of the Puna Turbidite Complex reflect a South American provenance from the Terra Amazonica and the early Terra Australis orogens between 2000 Ma and 440 Ma. The most abundant detrital zircon age group consists of Ordovician ages representing the Famatinian orogenic cycle (520-410 Ma), followed by those of the preceding Olmos-Pampean orogenic cycle (650-520 Ma), the Neoproterozoic rifting phase connected to Rodinia dispersal (1000-650 Ma) and the Sunsás orogenic cycle (1200-1000 Ma). The age distributions of fine and medium sand turbidite layers are statistically almost identical and do not display significant effects of sorting. Subchondritic εHf(t) values of Ordovician zircon emphasize crustal recycling and reworking as the most significant processes during the Famatinian Orogenic cycle. Hf(TDM2) indicate that crustal material mostly formed as juvenile crust in Mesoproterozoic time, during the Rȏndonia-San Ignacio and Sunsás orogenic cycles. Detrital zircon d18O data obtained from syndepositional Ordovician zircon are elevated and range between 6.5 and 8.8 ‰. Combined with similar data from the literature on intrusive and orthometamorphic rocks of the Famatinian magmatic arc these data indicate that crustal recycling and reworking of supracrustal rocks played a major role in the evolution of the Famatinian arc in the southern central Andes.