U-Pb ages, Hf-O isotopes and trace elements of zircons from the ore-bearing and ore-barren adakitic rocks in the Handan-Xingtai district: Implications for petrogenesis and iron mineralization

摘要

The petrogenesis of the Early Cretaceous adakitic intrusions in the Handan-Xingtai district, central North China Craton (NCC), and their genetic association with iron mineralization still remain controversial. Here, we present an integrated study of zircon U-Pb ages and Hf-O isotopes, as well as their trace elements for the ore-bearing and ore-barren complexes in the Handan-Xingtai district. Both of the ore-bearing and ore-barren complexes were emplaced contemporaneously (Early Cretaceous). Zircon epsilon(Hf)(t) and delta O-18 values of ore-barren complex range from - 16.0 to - 13.3 and from 6.3 parts per thousand to 7.1 parts per thousand, respectively, whereas those of ore-bearing complexes have variable delta O-18 (5.7 parts per thousand to 8.3 parts per thousand) and much lower epsilon(Hf)(t) values (- 24.3 to - 18.3). Furthermore, the ore-bearing complexes also have lower Ti-in-zircon temperatures but higher water contents and oxygen fugacity than those of ore-barren complexes. The zircon Hf-O isotopes, as well as their trace element data, indicate that the parental magma of ore-bearing complexes was a mixture of melts that derived from the enriched lithospheric mantle and ancient lower continental crust, whereas the ore-barren complex was most likely generated by partial melting of the enriched lithospheric mantle. We proposed that the high oxidation states and high water contents of magma, as well as the lower crustal materials may have played key roles in iron mineralization of Handan-Xingtai district.