西藏拉萨地体西北部革吉地区两期早白垩世岩浆作用——锆石U-Pb年龄、Hf同位素和地球化学特征

邦巴岩体位于拉萨地块西部革吉地区,由主体花岗岩、花岗闪长岩、闪长质包体及一系列近平行、南北向展布的花岗斑岩脉体组成。野外地质调查和LA-MC-ICP-MS锆石U-Pb定年表明,革吉地区白垩纪的两期岩浆活动分别发生在131~132Ma和127Ma。早期岩浆作用形成主体花岗岩、花岗闪长岩及闪长质包体,具有以下特征:(1)明显富集K、Cs等大离子亲石元素,亏损Nb、Ti、Zr等高场强元素;(2)具有明显的负Eu异常(Eu/Eu*=0.49~0.61)及负Ce异常;(3)具负εHf(t)值(-3.2~-0.3)及古老的地壳模式年龄(1.210~1.399Ga);(4)初始Sr同位素比值为0.70424~0.71472,εHf(t)值为-5.70~-5.54。晚期岩浆作用形成花岗斑岩脉体,具有以下特征:(1)富集K、Cs等大离子亲石元素,强烈亏损Nb、Ta、Ti等高场强元素;(2)基本不具有负Eu异常或具有轻微的负Eu异常(Eu/Eu*=0.74~0.87);(3)具有更老的Hf同位素地壳模式年龄(1.226~1.576Ga)及更负的大范围变化的εHf(t)值(-6.1~-0.7)。晚期岩浆作用锆饱和温度(777~796℃)及轻稀土元素不饱和温度(794~812℃)均高于早期岩浆的锆饱和温度(661~762℃)及轻稀土元素不饱和温度(750~769℃)。上述特征表明,两期岩浆作用均为中拉萨地块古老基底部分与地幔物质混染部分熔融的产物,随着岩浆作用的持续进行,岩浆中的古老地壳组分增加,熔体温度也增加,可能与南向俯冲的班公-怒江洋壳回转驱动的地幔岩浆活动向北迁移有关。     

西藏玛圭铅锌多金属矿成矿地质特征及找矿远景

西藏玛圭铅锌多金属矿在冈底斯铅锌银成矿带已发现的矽卡岩型多金属矿床中处于最西段。通过目前的预查工作,在矿区内共发现有14条矿体,初步预测可达到中-大型矿床规模。冈底斯中东段目前研究程度已较高,而西段与之具有相同的良好的矽卡岩型多金属矿成矿地质条件,但发现的矿床却很少。玛圭矿床的发现为该成矿带向西延伸和扩大规模提供了依据,并增加了进一步向西寻找同类型矿床的信心。     

Immobilization of copper under an acid leach of colloidal pyrite waste rocks by a fixed-bed column

Colloidal pyrite waste rocks (CPWR) which are mainly composed of colloidal pyrite and siderite widely deposit in sulfide mines in the middle and lower reaches of the Yangtze River belt, China, especially in Tongling City, Anhui Province, China. In this paper, a fixed-bed column was used to investigate the weathering and oxidation of CPWR and its role in immobilizing low-concentration Cu (10 mg L^?1) under weakly acidic leach (pH = 5.0). The experimental results indicated that the breakthrough capacity was around 14.0 mg Cu g^?1 CPWR when Cu²⁺ breakthrough concentration was 0.5 mg L^?1. Sequential extraction of Cu and dithionite–citrate–bicarbonate extraction of free iron in the used CPWR after the column breakthrough indicated that Cu removal by CPWR consisted of the following processes: oxidation of pyrite and dissolution of siderite in CPWR, ferrous oxidation, and adsorption of Cu on ferric (hydr)oxides. This study shows the potential application of CPWR as an effective sorbent for the removal of low-concentration Cu from acid mine drainage.