河北省燕山超基性岩带的岩体类型及其成矿作用

THE ROCK TYPES AND METALLOGENESIS OF YANSHAN ULTRABASIC ROCK BELTS,HEBEI PROVINCE, CHINA

燕山超基性岩带位于华北地台北缘,形成于中、晚元古代,属阿拉斯加型环带状镁质—铁质超基性岩。岩带中发育两种主要岩体类型;纯橄岩(橄榄岩)—透辉岩(闪辉岩)型和透辉岩(闪辉岩)—角闪岩(辉闪岩)型。两类超基性岩体系上地幔岩深部熔融分异不同期次侵入地壳的块体,第一类岩体含铬铁矿床,与纯橄岩相关系密切,矿石富铁贫铝,与豆荚状铬铁矿和层状铬铁矿有明显差异;第二类岩体含铂族矿床和铜镍铂钯硫化物矿床,与透辉岩相和闪辉岩相关系密切。上述三类矿床的成矿阶段和成矿作用不同,分别受岩浆熔离作用、晚期岩浆结晶作用和岩浆期后热液作用的控制。

Yanshan ultrabasic rock belt, which were formed at Middle-Late Proterozoic period, locates in thenorth margin of the North China Platform consisting of Alaska concentric Zoned type rock bodies.Zone patterns are: dunite (peridotite)-diopsidte (amphibole pyroxenite), diopsidite (amphibole pyrox-enite)-amphiboite (pyroxen amphibolite). All the ultrabasic rocks are the partial remelting ptoductsof upper mantle material. Chromite deposits generally occur, closely related to dunite, in the massiveswith the first zone patern. Ores are quite different from podiform and layered form Cr-deposits. Theyare charactered by high Fe and Low Al. Evedences Show that Pt-Pd concentrations and Cu-Ni-Pt-Pd sulfide ore deposits might occur about phase of diopsidite and amphibole pyroxenite in the mas-sives with second zone patern. The mentioned mineralizations may be controlled by magmatic segregn-tion. late magmatic crystalization and post-magma hydrothermal processes respectively.