He–Pb double dating of detrital zircons from the Ganges and Indus Rivers: Implication for quantifying sediment recycling and provenance studies

Provenance of Pleistocene Rhine River Middle Terrace sands between the Swiss–German border and Cologne based on U–Pb detrital zircon ages

“…We therefore conclude that in the Middle Pleistocene, input to the Rhine system of zircons younger than 200 Ma should be expected and should be registered at the sampled localities at least in small numbers. The fact that there are none in all studied samples along the Rhine River between Freiburg and Bonn, and bearing in mind the example from the Himalayas (Campbell et al 2005), allows for the speculation that there may not have been such a supply to the Rhine River at this particular time. This, then, makes it very likely that the detritus representing the so-called A. spectrum in the Rhine River sediments in fact originates from sources outside the Alps, which prominently include the Black Forest and Vosges mountains, and the Molasse basin sediments.…”

“…It is interesting to note in this context that detrital zircon age spectra obtained from modern sediments of the Indus and Ganges Rivers, which drain the axial zone of the Himalaya collisional orogen to a larger extent than the Rhine River does the Alps, contain a few percent of ages younger than 55 Ma, the time of the India-Eurasia collision (Campbell et al 2005;Rino et al 2008). The youngest U-Pb zircon age is 19.8 ± 0.7 Ma (Campbell et al 2005). This (2000), *4 from the compilation of Zeh et al (2001).…”

“…Paleogeography of the Gondwanan continental plates after Unrug (1996) Int J Earth Sci (Geol Rundsch) (2013) 102:917-932 927 demonstrates that the denudation of such collisional orogens proceeds fast and deep enough to supply ''young,'' syncollisional zircons from axial zones to draining river systems. Furthermore, for both the Himalaya and Alps cases, (U-Th)/He and fission track ages, respectively, show that detrital zircon grains, dated by the U-Pb method, of river sediments were frequently polycyclic and were exhumed und supplied to river transport since c. 30 Ma ago in both cases (Bernet et al 2004;Campbell et al 2005). We therefore do not exclude the possibility that the axial zone, at least theoretically, could have supplied young zircons to the river system via recycling pathways.…”

“…9 Map of the Alps and the adjacent foreland basins. External massifs: AR Aiguilles Rouge, Mo Montblanc, Go Gotthard after Schlunegger (1999) grains as young as 20 Ma (Campbell et al 2005). There the lag time between formation and deposition gets as low as 20 Ma, an order of magnitude smaller than in the case of the Rhine River.…”

Crustal redistribution, crust–mantle recycling and Phanerozoic evolution of the continental crust

“…For example, despite the deformation and melting associated with collision U-Pb dating of zircon crystallization (>750°C) from the granites of the Greater Himalaya shows no Cenozoic grains, but only early Paleozoic and Precambrian ages (Macfarlane, 1993;Parrish and Hodges, 1996; DeCelles et al, 2000; Campbell et al, 2005). Instead collision events provide several methods by which continental crust may be returned to the upper mantle.…”