【摘要】 扬子地台南缘早震旦世、古生代和晚三叠世海相碳酸锰矿石的ε_Nd（T）值分别是—4.6～—5.5,—8.1～—9.0和—3.5～—4.2.Z₁—C₁期间,它们的Nd模式年龄T_2DM平均为1931±46Ma,ε_Nd（T）-T演化线与亏损地幔演化线交点年龄为1950Ma,d（T）/dτ=0.96.Nd同位素组成特征表明:华南陆壳晋宁期前的增生作用主要发生在早元古代的1931±46Ma前;晚元古代地壳增生作用的影响范围有限;晋宁期后至印支运动前华南陆壳增生作用不明显.晚三叠世扬子地台西南缘海相碳酸锰矿石的ε_Nd（T）值升高,T_2DM年龄τ_sed降低,d（T）/dτ=—2.84,表明这个时期在拉张裂陷作用下,地幔组分大量分出,地壳增生活跃.这个时期锰矿床中约30%的成矿组分来源于地幔.更多还原

【Abstract】 The εNd(T) values of the marine carbonate Mn ores in Early Sinian and Palaeozoic and Late Triassic on the southern margin of the Yangtze platform are-4. 6-- 5. 5,- 8. 1--9. 0 and-3. 5--4. 2 respectively. During Z1-C1, their Nd model ages T2DM are1842-2009 Ma, with a mean age of 1931±46Ma. The data of the Z1-C1 carbonate Mn ores in εNd(T)-T coordinate diagram fit a straight line with a correlation coefficient of 0. 97, that intersects the evolution curve of the depleted mantle at 1950 Ma. The data of Hyolithes fossils and collaphana from the Early Cambrian in Mesuchum Section, Yunan, and the Early Sinian Toushantuo Formation in southern China fall exactly into this correlation line. Similarly, the data of the Z1-C1 seawater sediments in the continental crustal residence age(τrned) versus the deposition age(T)coordinated diagram also fit a straight line with a slope d(T)/dτ of 0. 96, approximate to 1. All Nd isotopic evidences indicate that the main pre-Jinning accretion of the continental crust took place only at 1931±46Ma ago in Early Proterozoic and was undistinguished in Meso-Neo Proterozoic accretion of the crust in Yangtze platform. The continental crust in southern China is substantially stable between the Jinning stage and In-dosinian stage without evident crustal growth and subduction. The effect of the Caledonian erogeny is only internal reset of the continental crustal material, but not related to the mantle. The εNd (T) of the Late Triassic seawater in the west-southern margin of the Yangtze platform, which is higher than golbal average. is another characteristics. Their data are located above the Z1-C1 correlation line in εNd(T)-T diagram and their Nd model age T2DM and crustal residence ages are reduced to 1371-1431Ma and 1156-1216 Ma, respectively, with a slope d(T)/dτ of-2.84 in τsed-(T) diagram. These evidences indicate that the continental crustal of southern China was transformed during the Indosinian stage in Late Triassic. New crustal growth occurred remarkably attributing to large amount of depleted mantle components differentiated out from the upper mantle. About 30% of the metallogenetic components of the Indosinia stage Mn deposit in the west-southern margin of the Yangtze platform were derived from the depleted mantle.更多还原