| Abstract:Characteristic pattern of the lead isotopic compositions of feldspar and ore from the Mesozoic granitoids and hydrothermal ore deposits obtained by using the plumbotectonic model of Doe and Zartman(1979)have defined five discrete provinces in Eastern China. The lead isotopic composition within each province reflects the age and geochemical behavior of the source materials. North China platform province In the province, granitic rocks and ore lead are least radiogenic(206Pb/204Pb being 16.089—16.852,207Pb/204Pb 14.990一15.470 and 208Pb/204Pb 35.565—37.420) and have the lowestμvalues. With a considerably wide range of isotope composition, indicating an Archeo-zoic lower crustal source. The granitic rocks are closely related to Mo, Au, (Cu) mineralizations. Qinling province In the province, the Mesozoic granitic rocks and ore lead are less radiogenic (206Pb/204Pb being 17.199—18.019, 207Pb/204Pb 15.392—15.601, and 208Pb/204Pb 37.447—38.509) and have lowerμvalues. With remarkably broad range of isotope composition, suggesting a mixture of upper mantle or/and lower crustal material with upper crustal sedimentary rocks. The granitic rocks are considered to be the parent rocks of Mo, (Au, Cu, Fe, W)mineralizations. The Lower Yangtze province It contains lead derived from early to middle Proterozoic basement rocks. In the province, both the feldspar and ore lead are variable in isotope composition and μvalues, with 206Pb/204Pb being 17.062—18.124, 207Pb/204Pb 15.302一15.676 and 208Pb/204Pb 36.980—38.800. It is worth noticing that the initial 87Sr/86Sr ratio(from 0.704 to 0.712)and δ18O values(from +8 to +12‰) of the Mesozoic granitic rocks have obvious variance too. These data suggest that the source materials of the migmatitic granite may be basement rocks with different buried depths and compositions. The granitoids in the Lower Yangtze province have close relation with Fe, Cu, Pb, Zn, Au, Ag, W, Mo, U mineralizations. Nanling province It contains lead derived principally from middle Proterozoic upper crustal metasedimentary rocks and connected intimately with rocks of Lower Banxi Group and Sibao Group exposed in Jiangnan old land. The isotopes of feldspar in the granite rocks are most radiogenic (206Pb/204Pb being 18.386—20.712，207Pb/204Pb 15.589—17.434 and 208Pb/204Pb 38.438—43.343) and have the highest F values. In the province, the Mesozoic granitic rocks are closely associated with W, Sn, Li, Be, Nb, Ta, U, Bi, (Pb, Zn), REE mineralizations.Southeast coastal province In the province, feldspar lead and ore lead both have a quite uniform isotope composition(206Pb/204Pb 18.6±,207Pb/204Pb 15.6±, and 208Pb/204Pb 38.8±). This coastal belt is confined where subducted pelagic sediments and/or basalts of the oceanic crust could recently supply a substantial amount of lead.The granites and volcanic rocks are closely connected with Pb, Zn, Cu, Mo, (W, Sn)mineralizations. |
