西范坪斑岩铜矿钾硅酸盐化作用的地球化学研究

ELEMENT′S MOBILITY DURING POTASSIUM-SILICATE ALTERATION OF MONZONITE-PORPHYRY:EVIDENCE FROM XIFANPING PORPHYRY COPPER DEPOSIT

西范坪铜矿是我国近年来新发现的斑岩型铜矿床。伴随铜矿化发生了强烈的钾硅酸盐化。蚀变作用使成矿主岩的 Si O2 ,K2 O增加 ,Ca O,Na2 O,Fe2 O3 减少 ;大离子亲石元素含量降低 ;L REE减少 ,L a N/ Yb N 比值升高 ,δEu值降低。通过研究认为 ,西范坪铜矿成矿母岩是富钠 (Na2 O>K2 O)斑岩 ,而不是富钾 (K2 O>Na2 O)岩石 ,这说明相对富钠的斑岩也能成矿。

Xifanping porphyry copper deposit is located in southwest of Sichuan province. In this paper we compare the element′s content of the altered rock and monzonite porphyry . It has been proved that K 2O and SiO 2 is increased; and CaO,Na 2O and Fe 2O 3 is decreased, during potassium silicate alteration .The concentration of LREE and LIL, especially La,Ce,Eu,Sr is decreased. The mobility of these elements are caused by minerelization fluids. Because the ore body is hosted in sodium silicate altered monzonite porphyry , these geochemistry characteristics of the monzonite porphyry can be used for outlining the location of the ore body. There are many porphyry copper deposits in Jinshajiang Ailaoshan monzonite porphyry . It has been reported that most of the host rocks of these deposit are rich in potassium (K 2O>Na 2O).But the host rocks of this deposit are rich in sodium (Na 2O>K 2O). So the host rock which is rich in sodium may be a new kind type of rock bearing copper.