矾山碱性岩体磷铁矿床金的地球化学

河北矾山钾质碱性岩体，由３期侵入岩和脉岩正长岩组成。第１期岩石为层状超镁铁质岩系，具韵律层结构。层状岩系中赋存巨大磁铁磷灰石矿床。碱性岩体全岩２２５个样品平均含金为７．８×１０－９。矾山岩体金的丰度为６．１×１０－９，是地壳金丰度（３．５×１０－９）的１．７４倍。第１期岩石平均金含量为８．８×１０－９，第２期岩石为５．１×１０－９，第３期岩石为７．４×１０－９，正长岩为４．２×１０－９。第１期侵入岩中辉石岩平均金含量为９．３１×１０－９，黑云辉石岩平均为７．７８×１０－９，伟晶正长黑云辉石岩为７．４０×１０－９，间隙状正长辉石岩为８．００×１０－９，磁铁磷灰石岩为１３．７８×１０－９，磷灰石岩和黑云磷灰石岩为１１．８０×１０－９，黑云母岩为１８．６３×１０－９。在垂直层状岩系的剖面上，岩石金含量呈韵律性变化。在东矿区，岩石金含量由西向东趋于降低。在岩浆液相分离过程中，金倾向富集在含铁、镁、钙和磷的熔体相中，而在岩浆结晶分异过程中，金可能富集在流体相中。

Gold Geochemistry of the Fanshan Alkaline Igneous Complex and Apatite-Magnetite Deposit in Hebei Province

The Fanshan potassic alkaline complex was formed by three periods of intrusive rocks,which were all penetrated by vein rocks. The first period intrusive rocks are layered ultramafic rocks that have rhythmic structure. Gigantic apatite-magnetite deposits occur in layered rocks.he main types of first period intrusive rocks are pyroxenite, biotite pyroxenite, pegmatoid orthoclase-biotite pyroxenite, magnetite apatite rock, apatite rock and interstitial orthoclase pyroxenite; the second period intrusive rocks might be divided into three rock types, viz., coarse- grained orthocalse pyroxenite, coarse-grained pyroxene syenite, and coarse-grained schorlomite-orthoclase pyroxenite; the main types of the third period rocks include trachytoid pyroxene syenite, fine-grained orthoclase pyroxenite, fine-grained pyroxene syenite and porphyroid pyroxene syenite. The three kinds of vein rocks are syenite, hornblende syensite and carbonatite.Au abundance (6.1×10-9) of the Fanshan complex is 1.74 times that of the crust (3.510-9). The determination of rocks of different intrusive periods suggests that the average Au content of the first, second, third period rocks and vein rock syenite are 8.8×10-9, 5.1× 10-9, 7.4×10-9and 4.2×10-9, respectively. In addition, Au content of various rocks of the irst period was determined: pyroxenite 9.31×10-9, biotite pyroxenite 7.78×10-9, pegmatoid orthoclase-biotite pyroxenite 7.40×10-9, interstitial orthoclase pyroxenite 8.00×10-9,magnetite apatite rock 13.78×10-9, apatite rock and biotite-apatite rock 11.80×10-9, and biotite rock 18.63×10_9. These data suggest that Au content shows vertical rhythmic variation in the profile of the layered rocks, and decreases from west to east. These phenomena imply that Au tended to concentrate in the melt with high content of Fe, Mg, Ca and P during the primary magmatic differentiation and then became richer in the fluid due to magmatic fractional crystallization.