【作者】 王硕；

【导师】 钱壮志；

【作者基本信息】 长安大学 ， 矿物学、岩石学、矿床学， 2011， 硕士

【摘要】 新疆北部发育一套时代相近、空间相邻、跨构造单元分布并且彼此之间在演化程度上可出现过渡类型的基性一超基性杂岩体。此类岩体因含有铜镍硫化物(Cu-Ni-PGE)矿床(如黄山、黄山东等)和(钒)钛磁铁矿(V-Ti-Fe)矿床(如尾亚、香山西,牛毛泉等)而倍受地质学家关注。牛毛泉基性杂岩体位于准噶尔古陆块北天山弧盆带博格达—哈尔里克晚古生代岛弧东段,岩体赋存磁铁矿体。本文选择牛毛泉基性杂岩体作为研究对象,通过野外地质调查、岩石学、矿物学、岩石地球化学等方法,对杂岩体的岩石组合类型、岩浆源区及原生岩浆性质、岩浆演化过程进行系统的研究,取得以下研究成果：1、牛毛泉基性杂岩体具有明显成层性和韵律构造特征；岩石主要类型有橄榄辉长岩、含橄榄辉长岩、辉长岩和角闪辉长岩,岩石多见蚀变,球状风化现象显著；主要造岩矿物为橄榄石、辉石、斜长石和角闪石,其中低品位磁铁矿产于中粗粒辉长岩中。2、主量元素地球化学特征表明岩石属拉斑玄武岩系列,主要经历了橄榄石、单斜辉石和斜长石的分离结晶作用,岩石的m／f值(m/f=(Mg2++Ni2+)/(Fe2++Fe3++Mn2+)原子数比值)介于0.65-1.44之间,为铁质基性—超基性岩；稀土元素总含量相对较低,轻重稀土元素之间分馏程度较强,轻稀土元素之间分馏弱。大多样品具不同程度的正铕异常；样品普遍富集大离子亲石元素(Rb、Ba、Sr、U),相对亏损高场强元素,大部分样品有明显的Nb、Ta负异常和弱的Ti正异常。3、利用橄榄石中最高Fo值(76)计算得出岩体原生岩浆中Mg0=7.3%;Fo=76的橄榄石不能代表与原生岩浆平衡的最初的液相线,所以,MgO=7.3%的岩浆只能约束原生岩浆MgO含量的下限。4、Nd-Sr同位素组成特征表明岩浆源区具有OIB型源区特征,受消减板片影响,具有向EM I演化的趋势,因此,推断源区为受俯冲流体交代改造的富集岩石圈地幔。5、新疆北部地区在早二叠世(290Ma-270Ma)出现大规模的后碰撞幔源岩浆活动,表现为众多镁铁质—超镁铁质岩体成带分布,如喀拉通克岩带、东天山黄山岩带,形成了—系列铜镍硫化物矿床和钒(钛)磁铁矿床。牛毛泉岩体可能是在后碰撞伸展背景下,拆沉的富集岩石圈地幔被软流圈加热后发生部分熔融并上侵的产物。更多还原

【Abstract】 There are series of basic-ultrabasic complex which were formed in similar era,adjacent in space and cross-tectonic units in the northen of Xinjiang province with transitional types exist among them.For they contains Cu-Ni-PGE deposits(such as Huangshan, Huangshandong) and V-Ti-Fe deposits(such as Weiya,Xiangshanxi and Niumaoquan),they have got much attentions from geologists who come from domestic and abroad. Niumaoquan complexs located in the eastern of late paleozoic Harlik arc in Junggar plate, open-pit mining has been carried out in it, therefore, we select Niumaoquan complex as theobject of research in this paper.Based on field investigation, petrography,mineralogy,geochemistry and other manners,we analyze the hybrid combination, source of magma and nature of primary magma,prosess of magmatic evolution.Based on these researches we get some achievements as follows:1.Niumaoquan complex have obviously layered property and rhythmical tectonic characteristics, the main rock types include olivine gabbro,olivine-bearing gabbro,gabbro and hornblende gabbro. Alteration are common in complex and the phenomenons of spherical weathering are significant.The main rock-forming minerals are olivine,chrome spinel, pyroxene and amphibole,low-grade magnet occurs in coarse-grained gabbro.2. Major elements indicate that Niumaoquan complex belong to tholeiite series which have experienced the fractional crystallization of olivine clinopyroxene and plagioclase. The m/f values (m/f=(Mg2++Ni2+)/(Fe2++Fe3++Mn2+) of most rocks range from 0.65 to 1.44,so Niumaoquan complex belong to ferruginous rocks.The concentrations of rare earth elements is relatively low,heavy rare earth elements and the whole rare earth elements’fractionation are slightly stronger,light rare earth elements’ fractionation are weak,positive Eu anomalies are showed in most rocks.The diagram of trace element which normalized by primitive mantle demonstrate that rocks are enriched large ion lithophile elements(Rb,Ba,Sr,U).The loss of Nb,Ta and high field strength elements(Zr,Hf) are displayed in most rocks with weak enrichment of Ti.3. It can be obtained the MgO content of primitive magma through the Fo molecular of olivine in Niumaoquan complex is 7.3%,but Fo value(76) is not high enough to represent the balance of the original magma liguidus initial phase,so 7.3% of MgO content can only bound it’s lower limit.4.Nd-Sr isotopic characteristics indicate that magma derived from the OIB-type source region which was affected by reduction plate,with the evolutionary trend to EMI,therefore,it is inferred that the magmatic source are enriched lithospheric mantle with transformation by subduction fluid.5.Large-scale post-collisional mantle-derived magmatism occurs in the northern of Xinjiang in early Permian(290Ma-270Ma),the symbol of it is a number of mafic-ultramafic rocks array as belts,such as Kalatongke belt,Huangshandong belt in the east of Tianshan,which formed a series of Cu-Ni-PGE and V-Ti-Fe deposits;Niumaoquan complex formed in the postcollisional extension setting background. Delamination of lithospheric mantle is partial melting due to be heated by asthenospheric material.At the same time,the material of enriched lithospheric mantle moved upward though the space which formed by delamination of the lithosphere.更多还原