Discovery of Late Cretaceous Baoshan Porphyry Copper Deposit in Dayaoshan, Qinhang Metallogenic Belt:Constraints from Zircon U-Pb Age and Hf Isotope
Bi Shijian
Yang Zhen
Li Wei
Liang Pei
Tang Kefei
Abstract：The Qinzhou Bay-Hangzhou Bay suture zone is an important porphyry copper metallogenic belt in southern China. Previous studies suggest that the ages of regional diagenesis and mineralization are mainly concentrated in the Late-Middle Jurassic (180-155 Ma),and the ore-bearing granite porphyry shows distinctly crust-mantle contamination.The Baoshan cop-per deposit is a porphyry-type Cu deposit newly discovered in the Dayaoshan region in the southwestern of the Qinhang metallo-genic belt in recent years.The granite porphyry is dominated as small stock into Sheshan granodiorite,including two out-cropped and one concealed magmatic emplacement.And the copper ore body is all hosted in the Baoshan concealed granite por-phyry.In this paper,laser ablation (MC)-ICPMS U-Pb dating and Hf isotopic compositions of zircons from three granite por-phyry samples in the Baoshan copper deposit are presented.Highly precise U-Pb results indicate that zircons from one con-cealed and two outcropped granite porphyries give weighted mean 206 Pb/238 U age of 91.1±0.6 Ma (1σ),91.3±0.8 Ma (1σ) and 90.1±1.0 Ma (1σ),respectively.And the zircons crystallized in the late Yanshannian granites giveεHf (91 Ma)values ran-ging from -8.74 to -5.13 and Hf model ages (TDM2 )of 1 210-1 394 Ma.U-Pb and Hf isotopic data can be interpreted as the crystallization time of these granites and the mineralization age,indicating it was formed in the ~91 Ma and may be developed by reworking of Mesoproterozoic crust closely related to partial melting.Together with other published geochronological data, it is proposed that the late Yanshannian magmatite and related Cu (Au)-W-Mo deposit are widely developed in the Dayaoshan and its adjacent areas.Moreover,two epochs of porphyry copper mineralization are confirmed in this study,including the Mid-dle-Late Jurassic and the Late Cretaceous,in the Qinhang metallogenic belt,and it is concluded that Late Cretaceous minerali-zation possibly resulted from the post-collisional crustal extension setting in the continental margin of the South China.
Keywords：Qinzhou Bay-Hangzhou Bay metallogenic beltDayaoshanBaoshan copper depositgranite porphyryLate Creta-ceous mineralizationgeochemistry
Publication Date：2015-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：22( 1458-1479 )