对董树文“长江中下游地壳物质构造动力调整作用”一文的商榷

A DISCUSSION ON DONG SHUWEN'S ARTICLE "TECTONODYNAMIC ADJUSTMENT OF CRUSTAL MATERIALS IN THE MIDDLE-LOWER REACHES OF THE YANGTZE RIVER"

董树文提出长江中下游铁铜矿带成岩系列和成矿物质源于中生代华北地块和扬子地块的碰擅重熔。本文根据许多基本地质事实,分析了成矿带与缝合带的关系;华北地块和扬子地块基底重熔的地球化学约束,Nd同位素比值与上地幔性质问题;Pb同位素信息等,以对董文提出的长江中下游铁铜矿带成岩成矿物质来源于大陆碰撞重熔说提出质疑。

Dong Shuwen holds that the metallogenic magma in the iron-copper metallo genic belt of the middle-lower reaches of the Yangtze River was produced by anatexis of crustal materials during the collision between the North China block and the Yangtze block in the Mesozoic. The authors consider that the grounds of Dong's paper are insufficient. First, Dong proposed two sutures, one of which is the Dabie Mrs. suture. In fact this suture does not exist; for there were neither two metallogenic magma series nor the iron-copper metaUogenic belt there. As for the other suture—the Yangtze 'suture' which is considered by Dong as a the magmatic metallogenic belt, no evidence for the existence of a Mesozoic collision-orogenic belt can be found there. This shows that the collision has no relation to the rock and ore formation. Secondly, Dong's suggestion that iron-forming rock series was formed by anatexis of the basement of the North China block and the copperforming rock series by anatexis of the Yangtze basement want geochemical evidence. In composition, iron-forming rock series and copper-forming rock series are more basic than basement of the North China block and basement of the Yangtze block, respectively; furthermore; the content of fusible components tend to be lower and that of the refractory components higher. These are in contradiction with anatexis. Third, the proposed Nd(T)=6.5 to 9.2 serving as the evidence of anatexis of the continental crust is refutable at the prerequisite of the unclear mantle nature, because intermediat-acid magmatic rocks with Nd(T)=-8 or so can also be derived from primitive mantle or enriched mantle.