下扬子断陷带中壳幔混源型产铀花岗岩的地质地球化学特征

THE GEOLOGICAL AND GEOCHEMICAL CHARACTERISTCS OF THE MIXED CRUST-MANTLE DERIVATION TYPE URANIUM-BEARING GRANITOIDS IN THE LOWER YANGZI FAULT DEPRESSION ZONE

对安庐石英正长岩带(AL)及姚村钾长花岗岩体(YC)的岩体地质、矿物岩石学,岩石化学,稀土元素、以及Sr、Pb、O同位素组成等一系列特征的研究表明,下扬子断裂坳陷带内花岗岩体的初始物质来源较深,系上地幔部分熔融产生的贫水偏碱岩浆沿深断裂上升侵位过程中同化混染了部分陆壳物质而成。据锶、铅同位素的二元混合模型计算,安庐岩带和姚村岩体的成岩物质中地幔组分分别占57％和52.8％,地壳组分分别为43％和47.2％。它们的成因系列应归属于壳幔混源型。

On the basis of research on geology, petrology, mineralogy, petrochemistry, geochemistry, REE and Sr, Pb, O isotope compositions in Anlu quartz syenite belt(AL) and Yaocun potash feldspar granite massif, it is shown that the initial rock-forming material derived from more depth and the magmas, which were rich in alkaliand poor in water, were derived from the mantle through partial melting and contaminated by the crustal materials in the process of movement upward and emplacement along the deep faults. According to the crust-mantle mixing model for Sr and Pb isotopes, it is calculated that 57% and 52.8% of the materials were derived from the mantle for Yaocun massif and Anlu rock-belt respectively, i. e., 43% and 47.2% of materials from the crust respectively. The genetic series of these granitic rocks may belong to that of mixed crust-mantle derivation.