Quantitative characterization of orogens through isotopic mapping

Abstract

The relationship between orogens and crustal growth is a fundamental issue in the Earth sciences. Here we present Nd isotope mapping results of felsic and intermediate igneous rocks from eight representative and well-studied Phanerozoic orogens. The results illustrate the distribution of isotopic domains that reflect the compositional architecture of the orogens. We calculated the areal proportion of juvenile crust and divided the orogens into five types: (i) highly juvenile (with >70% juvenile crust); (ii) moderately juvenile (70–50%; e.g., the Altaids with ~58% and the North American Cordillera with ~54%); (iii) mixed juvenile and reworked (50–30%; e.g., the Newfoundland Appalachians with ~40% and the Lachlan Orogen with ~31%); (iv) reworked (30–10%); (v) highly reworked (<10%; e.g., the Tethyan Tibet (~3%), Caledonides (~1%), Variscides (~1%), and the Qinling-Dabie Orogen (<1%)). This study presents an approach for quantitatively characterizing orogens based on compositional architecture through isotope mapping, and for investigating the relationships between orogenesis and continental growth.