Nd-Hf isotopic mapping based on a large archive of age data reveals voluminous continental growth of the Altaids and its control on metallogeny

Abstract

The Altaids, or the Central Asian Orogenic Belts, is generally considered to be the largest Phanerozoic accretionary orogen on Earth, but it is unclear if it was associated with extensive continental crustal growth and whether there is a link between the crustal growth and ore mineralization. This study, based on 5507 whole-rock Nd and 39514 (2443 samples) zircon Hf isotope data of felsic-intermediate-mafic igneous rocks as well as associated 1830 ore deposit data for the Altaids, presents Nd + Hf isotopic contour maps for this region. The maps highlight the three-dimensional (3D) lithospheric compositional architecture of the Altaids and make it possible to quantitatively evaluate the crustal growth and its relationship to ore deposits. The Altaids hosts ~4,107,350 km2 and ~184,830,750 km3 (assuming a crustal thickness of 40-50 km) juvenile crust (εNd(t) > 0), accounting for 58% by isotope-mapped area (~7,010,375 km2) of almost all outcrops of the Altaids (~8,745,000 km2) and formed during 1000–150 Ma (mainly 600–150 Ma). Therefore, the Altaids can be viewed as the largest storage area and most typical "fossils" of the juvenile crust in orogens worldwide. Our results are applicable to other types of orogens, particularly to the final continental collision and its control on mineralization. The juvenile crustal, slightly juvenile-reworked crustal, and slightly reworked crustal provinces controlled the Cu-Au, the Pb-Zn-Ag, and the Li-Be, Nb-Ta, and W-Sn ore deposits. According to the crustal architecture and background of deep compositions, we propose that the ore deposits can be grouped into three types: juvenile crust-related, mixed source (or slightly juvenile crust)-related, and reworked crust-related. This highlights the close relationship between accretion, continental growth, and mineralization and will facilitate exploration for specific ore deposit types in the Altaids.