【作者】 吕立娜；

【导师】 赵元艺；

【作者基本信息】 中国地质科学院 ， 矿物学、岩石学、矿床学， 2012， 硕士

【摘要】 班公湖-怒江成矿带位于西藏境内,是我国19个重要成矿区(带)之一,也是研究程度最低的一个。在成矿带西段分布的典型矿床有材玛中型矽卡岩型富铁矿床、尕尔穷中型矽卡岩型铜金矿床、嘎拉勒小型矽卡岩型金(铜)矿床和多不杂大超大型斑岩型铜金矿床。在系统的收集前人资料及野外地质调查的基础上,研究这该4个典型矿床的岩矿相学特征、岩石地球化学特征和同位素地球化学等,建立矿床模型,进一步建立区域成矿模型,研究成矿带西段构造演化,为进一步找矿提供理论依据。论文取得的成果主要有：(1)材玛矽卡岩型富铁矿区至少存在三期的岩浆活动,第一期介于早侏罗世-晚期-中侏罗世早期,第二期为中侏罗世晚期-晚侏罗世早期,第三期发生在早白垩世。其中第二期岩浆活动与成矿关系最为密切。成矿流体盐度主要介于4%-4.5%,成矿温度分为120-180℃、200-300℃、360-380℃、400-750℃四个阶段。(2)尕尔穷矿区成矿期次分为内生期(矽卡岩形成阶段-硫化物形成阶段-金形成阶段)和表生期(孔雀石、蓝铜矿、褐铁矿)。成矿与成岩几乎同时进行,介于85.9-95.3Ma之间。矿区岩石样品的气液包裹体的完全均一温度介于87-356℃,出现两个峰次,反应了成矿作用的两个阶段,盐度介于7%-7.5%区间的最多,属于中温中盐度成矿流体。(3)嘎拉勒矽卡岩型铜金矿床形成在晚白垩世,不存在岩矿时差。矿区存在两期的岩浆活动：第一期是东侧早白垩世早期岩浆的侵入作用,此阶段不具有成矿的地质条件,形成非成矿岩体；第二期是西侧晚白垩世成矿岩体的形成。嘎拉勒矿床与尕尔穷矿床成矿岩体在更深处存在同一岩基。(4)多不杂矿集区成矿与成岩几乎同时进行,成岩成矿时代介于115.54-122.45Ma。在波龙矿区钻孔采取的侏罗纪围岩地层中发现了大量的电气石,有的是存在于后期的石英脉中,有的为细小颗粒,聚集于斑点板岩的斑点中,为镁电气石-铁电气石系列,并且随深度增加,电气石中的铁减少,直到变为镁电气石。因此波龙矿区的成矿作用可能受到富硼气成热液蚀变作用的影响,在其他矿区是否存在气成热液的影响待进一步研究。(5)4个典型矿床的成矿作用发生在成熟的元古宙基底之上,并且材玛、尕尔穷和嘎拉勒为俯冲带岛弧环境成矿,尕尔穷和嘎拉勒矿区成矿岩体形成时幔源物质贡献较大,材玛和多不杂矿区岩体为壳源。缝合带向东多不杂矿区洋盆在早白垩世晚期已经闭合,进入陆-陆碰撞造山过程。由各矿床的成矿作用及成矿背景得知班公湖-怒江洋盆西段在晚侏罗世向北部的羌塘地块俯冲,晚白垩世早期向南部的拉萨地块俯冲,晚于晚白垩世早期闭合。更多还原

【Abstract】 Bangong Co-Nujiang suture in Tibet, is one of China’s19major metallogenic areas (or belts). But it also has the lowest grade of research. Multiple skarn-type and porphyry-type iron-copper metal deposits are distributed in the western part of the suture zone. And the typical deposits in the area are Caima medium skarn-type iron deposit, Gaerqiong medium skarn-type copper-gold deposit, Galale small skarn-type gold (copper) deposit and Duobuza super-large porphyry-type copper-gold deposit. On the basis collecting previous data systematically and field geological investigation, this thesis has studied the petrography and mineralography feature, geochemical characteristics and isotope geochemistry of the four typical deposits, established four mineralization model, further established a regional metallogenic model of the western section of the Bangong Co-Nujiang suture zone. Then we research the tectonic evolution in the western part of the suture zone, and provide a theoretical basis for further prospecting.(1) In Caima skarn-type iron ore district, there are at least three stages of magmatic activity. The first stage is between the early period of Early Jurassic and the early period of Middle Jurassic. The second stage is between the late period of Middle Jurassic and the early period of Late Jurassic. The third stage occurred in the early Cretaceous. And the second stage of magmatic activity is most affinitive to the mineralization. Ore-forming fluid salinity ranged from4%to4.5%,and the ore-forming temperature is divided into120～180℃,200～300℃,360～380℃,400～750℃in four phases.(2) In Gaerqiong skarn-type copper-gold ore district, the mineralization epochs conclude endogenesis(skarn-sulfide-gold)and surface(malachite, azurite, limonite)stages. The mineralization and diagenesis almost occured simultaneously, between85.9Ma and95.3Ma. The homogenization temperature of V-L inclusions is between in87～356℃,and it suggested that the deposit may have experienced two stages of mineralization. The salinity is mostly between in7%-7.5%,and it belong to mesothermal and medium-salinity ore fluid.(3) Galale skarn-type copper-gold deposit formed in Late Cretaceous, and there is no rock and mineral jet lag. There are two stages of magmatic activity in ore district. The first stage is the magmatic intrusion of the east side in the early period of Early Cretaceous, in which there was not ore-forming geological conditions, resulting in formation of non-ore-forming rock. The second stage is intrusion of ore rock in late Cretaceous in west side. In deeper place in Galale and Gaerqiong deposits, it maybe the same batholith. (4)In Duobuza ore concentrated area, the mineralization and diagenesis almost occured simultaneously, between115.54Ma and122.45Ma. A large number of tourmaline was found in the surrounding rock(the Jurassic)sampled in the drilling of Bolong ore district. Some exist in the late quartz veins, and some exist in the spots of spot slate in the form of fine particles. They belong to dravite-iron tourmaline series, and tourmaline iron reduction increase with depth until it turn to dravite. Therefore it is speculated that the mineralization in Bolong ore district may be subject to the impact of the boron-rich gaseous hydrothermal alteration, and the existence of the impact of of gaseous hydrothermal fluids in other ore districts is to be further studied.(5) The mineralization of four typical deposits occurred above the mature Proterozoic basement. And the mineralization of Caima, Gaerqiong and Galale occurred in subduction zone island arc setting. In Gaerqiong and Galale ore districts, mantle source material made greater contribution to the formation of ore-forming rock. The rock mass in Caima and Duobuza ore districts belong to crustal source type. In Duobuza ore district to the east of Suture zone, ocean basin have been closed in the late period of Early Cretaceous, and turn to the continent-continent collision orogenic process. On the basis of mineralization and metallogenic background of deposits, it can be concluded that the western part of Bangong Co Nujiang oceanic basin subduced to Qiangtang block in northern in Late Jurassic, subducted to Lhasa block in southern in the early period of Late Cretaceous, and closed later than the early period of Late Cretaceous closure.更多还原