河北东坪金矿区水泉沟岩体的地球化学特征

GEOCHEMISTRY CHARACTERISTICS OF SHUIQUANGOU ROCK BODY IN DONGPING GOLD ORE DISTRICT,HEBEI PROVINCE

水泉沟岩体主要由二长岩构成。主要矿物是碱性长石和斜长石，它们的含量高达８０％以上。石英不多见，暗色矿物含量少。副矿物主要是磁铁矿、石榴石、榍石和锆石。交代结构发育，蚀变现象普遍。主要化学组分和微量元素含量及δ１８Ｏ值变化范围大。该二长岩体是由老片麻岩经热液碱交代作用而成。

Shuiquangou monzonite rock body and gold ore deposit are controlled by the great westeast rift of Shangyi-Chongli-Chicheng. Lithological characters are nonhomogeneous. Major minerals are alkali-feldspar and plagioclase. Content of quartz and mela-mineral are very little. Major accessory minerals are magnetite, garnet, titanite,zircon. Metasomatic texture develops. Alteration is widespread. Under the condition of intense sodium metasomatisin, albite rock can be formed in some areas. Under the condition of intense potassium metasomatism, giant crystal potash feldspar vein can be formed.The dominant chemical component and the content of trace element of monzonite change greatly. This reflect difference of metasomatism intense degree. In monzonite SiO2, Na2O, K2O, Rb are high and add compositions, Fe2O3, FeO, MgO, CaO, Sr REE are low and release compositions. Although Na2O - K2O exceeds 11% in monzonite, but the small amount of feldspathoid and mela-alkaline minerals in monzonite proves that it isn't alkaline rock. This rock is not magma intrusive monzonite, because its SiO2 is higher than that of magma intrusive monzonite (52-66%).There appears a lot of gneiss restites at one side of monzonite rock body which contacts with gneiss, and that δ18O values of monzonite are similar to gneiss. These facts show that gneiss is primary rock of metasomatic monzonite. The formation of Shuiquangou monzonite rock body is a long and complicatedly process of hydrothermal alkali-metasomatism of gneiss.