Petrogenesis of Late Cretaceous granites and implications for W-Sn mineralization in the Youjiang Basin, South China

Abstract

Five Late Cretaceous tungsten-tin ore clusters (Gejiu, Dulong, Bainiuchang and Dachang tin deposits and Damingshan tungsten deposit) have been identified in the Youjiang Basin, South China. However, litter attention has been paid to such W-Sn metallogenetic specialization in the Youjiang Basin, as well as the geodynamic setting of mineralization and related magmatism. This study presents petrographical, geochronological, zircon Lu-Hf isotopic and whole-rock geochemical analyses for the Kunlunguan (KLG) biotite granites from the Damingshan ore cluster in the eastern part of the Youjiang Basin, and synthesizes previously published data from other ore clusters. The KLG granites yield crystallization ages of ∼ 100.2–98.6 Ma, and are characterized by high SiO2 and low A/CNK, Rb/Sr and 10000*Ga/Al, belonging to metaluminous to weakly peraluminous unfractionated I-type granite. The granites have initial 87Sr/86Sr ranging from 0.70919 to 0.71133 and εNd(t) from −9.3 to −6.8 with zircon εHf(t) ranging from −13.2 to −3.1, Eu/Eu* from 0.18 to 0.42 and Ce/Ce* from 7.43 to 254. Such signatures suggest that the KLG granites originated from partial melting of lower crustal mafic rocks with a minor mantle component. Overall, the W-Sn metallogenic specialization in the Youjiang Basin was first-order controlled by crustal sources of ore-host granites. The metallogenic age of the W-Sn deposits (∼97–75 Ma) is similar to the crystallization age of the granites (∼100–77 Ma), and the ages of mineralization and granites in the west of the Youjiang Basin are relatively younger than those in the east. The Late Cretaceous W-Sn mineralization system in the Youjiang Basin belongs to a part of an EW-trending Sn-W-Cu mineralization belt from Myanmar to Guangdong (South China), forming in an extensional setting caused by the Neo-Tethys oceanic slab roll-back.