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青海省祁漫塔格-都兰成矿带是以铁铜多金属为主的成矿带,其矿产丰富但研究程度较低。双庆铁矿床是该成矿带上十分典型的矿床,目前尚未系统开展矿物地球化学研究。笔者采用电子探针、电感耦合等离子质谱仪(ICP-MS)等测试手段,对磁铁矿进行主(常)量元素、微量元素地球化学特征进行研究,辅以磁铁矿氧同位素数据,以期为矿床成因提供地球化学证据。磁铁矿主量元素的Ti O2-Al2O3-(Mg O+Mn O)三角成因图解揭示,形成双庆铁矿床的磁铁矿为接触交代作用的夕卡岩型磁铁矿。微量元素特征表明其成矿物质来源较深,Ni/Co比值揭示磁铁矿为火山热液交代的岩浆成因的来源特征,而Pb、Zn质量分数相对较高,表明有后期的热液叠加作用。稀土元素呈不对称的“V”字形配分模式,轻重稀土发生一定程度的分异作用,无明显δEu和δCe异常,稀土总量低;磁铁矿的氧同位素特征表明其成矿物质来源属于幔源,流体来源为花岗质岩浆水。
Qimantag-Dulan metallogenic belt in Qinghai Province is a metallogenic belt dominated by iron, copper and polymetallic, which is rich in mineral resources but less studied. Shuangqing iron deposit is a very typical deposit on the metallogenic belt, and mineral geochemistry has not been systematically studied at present. The author uses the electronic probe, inductively coupled plasma mass spectrometry (ICP-MS) and other testing methods, the main (normal) amount of elemental and trace element geochemical characteristics of magnetite study, supplemented by magnetite oxygen isotope data, with a view to Geochemical evidence for the genesis of the deposit. The genesis of the Ti O2-Al2O3- (MgO + MnO) trigonometries of the major elements of magnetite reveals that the magnetites forming the Shuangqing iron deposit are skarn-type magnetites with contact metasomatism. The characteristics of trace elements indicate that they have a deep source of mineralization. The Ni / Co ratio reveals that the magnetite is a source characteristic of volcanic hydrothermal metasomatism, while the Pb and Zn mass fractions are relatively high, indicating the late superimposition of hydrothermal fluids . The REE shows an asymmetric “V ” pattern with a slight degree of differentiation of light and heavy rare earths with no obvious δEu and δCe anomalies and a low total amount of rare earths. The oxygen isotopic characteristics of magnetite indicate its source of mineralization Belongs to the mantle source, the fluid source is granitic magmatic water.