文档介绍：Geochemical Characteristics and Petrogenesisof the ErhongwaMafic-UltramaficIntrusion,XinjiangA Dissertation Submitted for the Degree of MasterCandidate:Zhang RuiSupervisor:Prof. Qian ZhuangzhiChang’an University, Xi’an, ChinaI摘要东天山黄山镁铁-超镁铁质岩带位于新疆北天山造山带东段。二红洼岩体位于该岩带的西段,该带因发育大量镁铁质-超镁铁质岩石而倍受地学界广泛关注。其中,香山、黄山、黄山东、葫芦、图拉尔根等岩体已产出有工业矿床,在二红洼、黄山南岩体中也发现了不同程度的铜镍硫化物矿化。近年来,多位学者在该带上的大型矿床做了诸多深入研究,相对而言,二红洼等弱矿化岩体研究尚不深。本文通过对二红洼镁铁-超镁铁质岩体的岩石学、矿物学、地球化学以及同位素年代学等多方面进行了系统研究,论述了岩体的地质特征与原生岩浆性质,探讨了岩浆演化过程与同化混染作用,分析了成岩地质背景等,取得的主要成果如下:1岩体由南、北两个岩体组成,呈北东-南西向展布,,呈耳状;南岩体呈椭圆形,。岩体分为两个侵入期次,第一侵入期次岩性为含长二辉橄榄岩和橄榄辉长岩;第二侵入期次岩性为辉长苏长岩和淡色辉长岩,岩石球状风化现象显著。主要造岩矿物有橄榄石、辉石和斜长石。2、岩体的岩石化学和地球化学特征表明,各类岩石的m/~,为铁质超基性岩;稀土元素丰度很低,呈弱轻稀土富集型;微量元素中相对富集Ba、Th等元素,大多数都具有Nb、Ta等元素的负异常。3、利用橄榄石中最高Fo值()%,为苦橄质岩浆;Fo= ,所以,MgO=%的岩浆只能约束原生岩浆Mgo含量的下限。岩相学、岩石化学和矿物晶体化学特征表明,岩体在岩浆演化过程中主要发生了橄榄石、斜方辉石、单斜辉石和斜长石的分离结晶作用。4、Hf-Sr-Nd同位素特征显示二红洼镁铁-超镁铁质岩体的原生岩浆具有亏损型地幔特征,并在上升过程中加入了7-32%的新生岛弧地壳物质,上升到较老上地壳之后发生了小于5%的混染作用。5、La-ICP-MS锆石U-Pb测年结果显示,橄榄辉长岩年龄为283±,同黄山岩带上的黄山、黄山东、葫芦、香山、图拉尔根等岩体年龄基本一致。二红洼镁铁超镁铁质岩体形成于早二叠世,是东天山后碰撞伸展环境的产物。关键词:二红洼,镁铁质-超镁铁质岩体,岩石学,地球化学,岩浆源区IIAbstractThe Erhongwa mafic-ultramafic intrusion is at the western part of the Huangshan mafic-ultramafic rock beltwhich is located at the eastern part of the north Tianshan orogenic belt, It develops a series of regional mafic -ultramafic rocks and highly concerned by geologists. Xiangshan intrusion,Huangshan intrusion,Huangshandong intrusion,Hulu intrusion,Tulaergen intrusion have magmatic sulphide deposits; Erhongwa intrusion and Huangshannan intrusion develops Ni-Cu sulphide mineralization. In recent years, many geologists have done a lot of research on large deporsits of the Huangshan pared to Erhongwa intrusion. This paper study systematically Ehongwa mafic-ultramafic intrusion through research on the petrology, mineralogy, geochemical and isotope c