中天山白石泉镁铁-超镁铁质岩体岩石学与矿物学研究

白石泉地区镁铁一超镁铁质岩体处于塔里木板块前缘活动带与中天山地块接合部位，是中天山地块华力西中期岩浆活动的产物。主要岩石类型有辉石橄榄岩（斜方辉石橄榄岩、斜长二辉橄榄岩）、橄榄辉石岩、橄长岩、辉长岩及角闪辉长岩等，主要造岩矿物为橄榄石、斜方辉石、单斜辉石、角闪石、斜长石及黑云母。橄榄石均为贵橄榄石，其Fo值（78-85）位于含铜镍硫化物矿橄榄石的Fo值范围之内；辉石主要有顽火辉石、古铜辉石、紫苏辉石、透辉石等；斜长石的环带构造较为发育；角闪石的FeO含量随着岩浆的演化逐渐增加。它们与造山带环境中的东疆型镁铁一超镁铁杂岩中的造岩矿物具有相同的特征。这些特征表明了白石泉地区的镁铁一超镁铁质岩体的原始岩浆为高镁的拉斑玄武质岩浆。

Petrography and mineralogy of Baishiquan Cu-Ni-bearing mafic-ultramafic intrusions in Xinjiang

The Baishiquan mafic-ultramafic intrusions associated with magmatic Cu-Ni-PGE sulfide deposits are located in central Tianshan block of northern Xinjiang. They are Late Permian mafic-ultramafic rocks which intruded into the Mid-Proterozoic sequences comprising schists, gneisses and marbles. They display ellipse and irregular forms in plan, and are basin-shaped in the cross section. The Baishiquan intrusions are comtposed of pyroxene peridotite, olivine pyroxenite, troctolite, hornblendite, gabbro, hornblende-gabrro and diorite. Peridotite and pyroxenite are main rock types hosting Cu-Ni-PGE ores. The rock-forming minerals are comtposed of the assemblage of olivine, orthopyroxene, clinopyroxene, hornblende, plagioclase ly surrounded by orthopyroxene, clinopyroxene and plagioclase oikocrystals with and biotite. Olivine is normal- Fo being 80--85, which overlap minerals of the magmatic Cu-Ni-PGE sulfide deposits. Pyroxene is dominated by bronzite, endiopside ands- mall amounts of hypersthene and diopside. Plagioclase is usually characterized by rhythmic and reverse zones, consisting of An ranging from 50 to 70. Hornblende was formed at the last stage and enclosed olivine, pyroxene and plagioclase. According to these characteristics, the primary magma of such mafic-ultramafic intrusions must have been mantle-derived tholeiitic magma.