FEATURES OF Pb ISOTOPIC COMPOSITION OF ORES AND EVOLUTION OF CONTINENTAL CRUST OF CHINA

来源 :Science in China,Ser.B | 被引量 : 0次 | 上传用户:woshiwl0000
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Based on the Pb isotopic features, the ore leads in the continent of China can be dividedinto four types: (i) single-stage lead of low μ value derived from mantle, (ii) homogeneouslead of crustal source with high μ value, (iii) modern mixing lead between mantle andcrust, and (iv) residual lead of crustal source. As the leads from mantle had possessed single-stage features (μ = 7.8) before the Proterozoic, the ages of continental crust can be calculatedbased on the mixing Pb of type (iii). The results hidicate that the continental crust of Chinawas mainly generated during the Archaean, and the growth rates of crust reached the max-ima by the ages of 3.3-3.4, 2.6 and 1.6-1.7 b.y. The occurrences of residual crust Pbwith high ~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb anomalies were associated with the remelting andreconstruction of crust since 1.6 b.y. ago. The lead sources in the continent of China showhigher Th/U ratios (3.3-6.5) and ~(207)Pb anomalies than those in other continents, indicationthe conti Based on the Pb isotopic features, the ore leads in the continent of China can be dividedinto four types: (i) single-stage lead of low μ value derived from mantle, (ii) homogeneouslead of crustal source with high μ value, (iii ) the mixing of mantle and crustal from (iv) residual lead of crustal source. As the leads from mantle had possessed single-stage features (μ = 7.8) before the Proterozoic, the ages of continental crust can be calculated based on mixing of Pb of type (iii). The results hidicate that the continental crust of Chinawas mainly generated during the Archaean, and the growth rates of crust reached the max-ima by the ages of 3.3-3.4, 2.6 and 1.6-1.7 by The occurrences of residual crust Pb with high ~ (207) Pb / ~ (204) Pb and ~ (208) Pb / ~ (204) Pb anomalies were associated with the remelting and reconstruction of crust since 1.6. The lead sources in the continent of China showhigher Th / U ratios (3.3-6.5) and ~ (207) Pb anomalies than those in other continents, i ndicationthe conti
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