Spatial–temporal evolution, zircon Hf-O isotope characteristics of Yanshanian magmatism and their control on ore deposits in the southeast coast of China

Abstract

The southeast coast of China (SCC) is an essential component of the Circum Pacific Tectonic Metallogenic Domain with huge amount of Yanshanian magmatic rocks and related Cu-Au-Mo-W-Sn deposits. The relationship between regional deep crust component and mineralization is still not very clear. In this study, we present 27 new zircon U-Pb and Lu-Hf isotopic, 111 whole-rock major and trace element, and 11 zircon oxygen isotopic data for Yanshanian granitoid from the SCC, combining with data from literature, to display the spatial–temporal evolution of the granitoid, particularly to trace the components of the deep crust, and to delineate the crustal architecture by Hf isotopic mapping. A total of 295 zircon U–Pb ages show four phases (194 to 184, 176 to 153, 153 to 124, and 122 to 80 Ma) of magmatic rocks. These rocks characterized by continental margin arc magma were formed during the Paleo-pacific subduction and rollback. Zircon Hf isotopic mapping of these granitoids yield three Hf isotopic provinces (I, II, III), which distributed successively from the Interior Cathaysia Block (ICB) to the Coastal Cathaysia Block (CCB). Province III is the oldest, followed by province II and province I. These provinces combining with zircon O isotopic data display that the ICB is dominated by old deep crust (TDMC = 1.85 – 1.60 Ga) with a few juvenile crust, the average εHf (t) changes from -11.5 to -7.1, δ18O = 6.68 – 8.84 ‰, while the CCB is dominated by juvenile crust (TDMC= 1.35 – 1.10 Ga) with a few old deep crust, with the average εHf (t) = -3.4 to + 4.7, δ18O = 5.52 – 7.78 ‰. However, the deep crust composition along the Zhenghe-Dapu fault is complex, which is probably due to the strong crust-mantle interaction. The Hf isotopes mapping reveals temporal-spatial correlations between the composition of deep crust and spatial distribution of ore deposits, demonstrating that the architecture, nature, and composition of the crust controlled mineralization and the distribution of ore deposits. The porphyry Cu-Au deposits are exclusively located in regions with juvenile crust, granite-related W-Sn deposits cluster in the oldest crustal regions or developed along the margin of the old crustal block. This study suggests that the deep crust component can be imaged by Hf isotope mapping and it can provide significant information on mineralization with deep crust component and architecture and on strategic ore-prospecting in a region.