华夏古陆古元古代高度亏损地幔的Nd同位素证据

NEODYMIUM ISOTOPIC EVIDENCE FOR EXTREMELY DEPLETED MANTLE IN PALEOPROTEROZOIC IN CATHAYSIA BLOCK

华夏古陆闽浙地区古元古代晚期（（１７６６±１９）Ｍａ）斜长角闪岩的εＮｄ（ｔ）值变化范围为＋５．６～＋８．５，表明其母岩浆来自高度亏损的地幔源，同时其εＮｄ（ｔ）明显高于世界上其他地区同时代亏损地幔的εＮｄ值，而与澳大利亚中部ＨａｒｔｓＲａｎｇｅ地区１７６７Ｍａ的高度亏损地幔源（＋６．９～＋８．２）相当．华夏古陆闽浙地区和澳大利亚中部ＨａｒｔｓＲａｎｇｅ地区１．７７Ｇａ前高度亏损地幔的存在，表明多阶段幕式增长模式可更好地反映亏损上地幔的演化趋势．

The Paleoproterozoic amphibolite of (1766±19)Ma in the SW Zhejiang and NW Fujian provinces, the Cathaysia block, has ε Nd ( t ) values ranging from +5.6 to +8.5. These ε Nd ( t ) values are significantly higher than those proposed in models for the contemporaneous depleted mantle, but coincident with those for the extremely depleted mantle revealed by the 1.77Ga meta_tholeiites from the Harts Range meta_igneous complex of central Australia. Existence of such extremely depleted mantle in the Paleoproterozoic from both Cathaysia and central Australia indicates that Nd isotopic evolution of the depleted mantle can be better explained by the episodic rapid crustal formation extracted from an increasing volume of depleted mantle.