【作者】 孙丽；

【导师】 李胜荣；

【作者基本信息】 中国地质大学（北京） ， 矿物学， 2003， 硕士

【摘要】 西藏尼木-曲水地区地处世界三大主要斑岩成矿域的特提斯——喜马拉雅成矿域，其大地构造位置属冈底斯-念青唐古拉构造带的冈底斯陆缘火山-岩浆弧中部，发育有多期次、大规模的中酸性侵入岩及火山岩。西藏尼木-曲水一带目前已发现众多铜、金矿化点，但大型原生矿床除厅宫和冲江2处铜矿床外，金矿床一直没有突破，目前总的矿产形势还呈现只见星星少见月亮的态势。已有的工作表明，本区矿床和矿化点（Au,Cu）与中酸性岩浆岩有关，但迄今尚未对其成矿潜力进行过研究，特别是还未从成因矿物学角度进行研究。本文从这一空白领域入手进行研究，以图对本区与花岗岩类有关矿产的找矿勘查工作提供矿物学依据。 通过对本区花岗岩类样品进行显微观察研究，知其主要的岩石类型为花岗闪长岩、石英二长闪长岩，其中的岩石包体主要为二长闪长岩，其造岩矿物为钾长石、斜长石、角闪石、黑云母、石英、磁铁矿、榍石、磷灰石和绿帘石等，长石中环带现象比较常见，黑云母、榍石等暗色矿物颜色较深，表明其氧化程度较高。 对本区花岗岩类样品进行了全岩主量元素、稀土元素及微量元素分析，对角闪石和黑云母单矿物进行了化学成分分析，对钾长石、斜长石、角闪石、黑云母、及石英、磁铁矿、磷灰石和榍石进行了电子探针和X射线粉晶衍射分析。通过对测试数据的分析与综合研究，并同中国和世界一般花岗岩类以及中国主要金、铜成矿岩体的花岗岩类进行对比，得出本区花岗岩类岩石具有以下特征：属磁铁矿-Ⅰ型或同熔型花岗岩，其岩浆物质具壳幔混源特征：主要由熔融态岩浆经结晶分异作用，通过多期变速上侵而形成；其分异演化程度较低；寄主岩基和包体具有同源性；岩石的形成温度范围约为500℃-700℃，压力大约为2.50GPa-4.35Gpa，氧逸度值1gfo₂为-15.53—14.00；该岩带主要形成于板块碰撞前消减的活动板块边缘期，为燕山至喜马拉雅早期的大陆边缘火山弧环境的产物。 将本区花岗岩类与金、铜矿有关的花岗岩类的矿物学、岩石学和地球化学特征进行对比，结果表明尼木-曲水地区的花岗岩类富Fe、Mg和Ca，Na₂O／K₂O＞0.8，ANKC＜1.10，DI＜88，Fm为0.50-0.80，Eu亏损不强烈，δEu＞0.3，La／Yb＞10，上述特征为有利于金、铜矿形成的标志。 通过与胶东郭家岭地区的花岗岩类的矿物学进行对比，可知本区花岗岩类矿物结晶时处于氧化状态，具有富含挥发分的特征，碱质含量高，造岩矿物及副矿物表现出Ⅰ型花岗岩特征，具有壳幔混源物质，表现出有利于金、铜矿形成的花岗岩类的矿物特征。更多还原

【Abstract】 The area of Nimu-Qushui in Tibetan Plateau lies in Tethyan-Himalaya metallogenic belt, which is one of three main porphyry metallogenic belts. It is in the middle of marginal volcanic-magmatic arc of Gandise tectomagmatic belt. Multiphase and large-scale medium-acid intrusive and volcanic rocks have well developed in this area. Many Cu and Au mineralized spots have been discovered along Nimu-Qushui area. But large-scale Cu ore deposits have been found only in Tinggong area and there is no breakthrough in large primary Au ore deposit prospecting. It has been proved that large-area medium-acid magmatic rocks have well developed in this area and had close relation with some Au or Cu ore deposits and mineralized spots. But till now little research has been done for mineralization potentiality of medium-acid magmatic rocks, especially in the aspect of genetic mineralogy. In order to know the mineralization potentiality of medium-acid magmatic rocks in the area of Nimu-Qushui in Tibetan Plateau, this thesis focuses on the studies of genesis and prospecting potentiality of the intrusive rocks from the point of view of genetic mineralogy. This will provide some information for prospecting.The microscopical observation proves that the main types of granitoid rocks are granodiorite and quartz monzodiorite, and the enclave is mainly monzodiorite. The rock-forming minerals are mainly k-feldspar, plagioclase, amphiboie, biotite, quartz, magnetite, titanite, apatite, epidote, etc. The zonation of the feldspars is very popular. The dark-colored minerals, such as biotite and titanite, have been highly oxidized.The main element analysis of whole rocks, the REE analysis and the trace element analysis have been done for the granitoid samples in this area. The chemical composition analysis has been done for the amphiboie and biotite minerals. The EPMA and x-ray powdered crystal diffraction have been done for k-feldspar, plagioclase, amphiboie, biotite, quartz, magnetite, titanite. and apatite. By these analyses and comparison with general granite both in China and the world and with the granite in other Au or Cu belt in China, the characteristics of the granite in this area are concluded as follows. It belongs to magnetite-I or syntectic granite and has crust-mantle mixed characteristics; it was formed mainly by crystallization differentiation of melting magma and multiphase varied intrusion; the degree of differentiation evolvement is not high; the granite and its enclaves p.re congenetic; the range of temperature is about 500 -700 , the range of pressure is about 2.50 Gpa-4.35 Gpa,and the range of oxygen fugacity (lg fo2) is -15.53--14.00; most granite bodies formedbefore the collision of plates, and few formed after the collision of plates.Compared with the granite from other areas in mineralogy, petrology, and geochemistry, the granitoid in Nimu-Qushui has a high content of Fe, Mg and Ca. The value of Na2O/K2O is over 0.8, ANKC is under 1.10, and DI is under 88. Its Fm is 0.50-0.80, 5 Eu>0.3 and La/Yb > 10. The characteristics above mentioned are the signs profitable for formation of Au and Cu ore deposites.Comparing with the granitoid from Jiaodong Guojialing in mineralogy, the minerals in the granitoid in Nimu-Qushui granitoid crystallized in the environment of oxidization, the granitoid has a characteristic of rich volatile components and a high content of alkali, the rock-forming minerals and accessory minerals have a characteristic of I-type granite, and the granite shows a characteristic in favor of An and Cu ore formation.更多还原