湘南地区锡石结晶控制因素——来自阴极发光图像、微量元素和年龄的证据

湘南是南岭有色、稀有多金属成矿带的重要组成部分，发育多种类型锡多金属矿床，目前对于不同类型锡石的流体来源、成分和物理化学条件差异，尚不清楚。选择湘南地区香花岭、芙蓉和红旗岭锡多金属矿床，采集接触矽卡岩型、远端矽卡岩型、云英岩型、绿泥石脉型和石英脉型5种不同类型锡石，开展阴极发光（CL）显微结构、年龄、原位微量元素等研究，探讨不同类型锡石结晶过程控制因素。红旗岭钨锡矿床锡石LA-ICP-MS U-Pb年龄为153.7±2.4 Ma。湘南不同类型锡石CL图像颜色变化主要与Ti和Nb、Ta相对含量有关，含CL激发剂Ti含量高则CL图像颜色浅，含CL抑制剂Nb、Ta高则CL图像颜色较深。不同类型锡石的Zr/Hf值反映了围岩地层的同化混染和流体演化程度。其中矽卡岩型和石英脉型锡石Zr/Hf值高于成矿岩体，受地层的影响较大，云英岩型和绿泥石脉型锡石Zr/Hf值则低于成矿岩体，表明其具有较高的流体演化程度；绿泥石脉型和石英脉型锡石原生与次生结构发育完全相反的Fe、W、U含量及Zr/Hf值变化趋势，可能分别代表了大气水加入和脉冲式岩浆流体。

Controls on crystallization of cassiterite from the southern Hunan: Evidence from cathodoluminescence,trace elements and geochronology

Distinct types of tin polymetallic mineral deposits were formed in the southern Hunan as an important section of the Nanling non-ferrous and rare metallogenic belt. It is still not fully understood about the fluid source, composition and physicochemical state of various tin deposits. Five types of tin ores, including proximal skarn, distal skarn, greisen, chlorite vein and quartz vein from the Xianghualing, Furong and Hongqiling deposits, were taken as the cases to discuss controls on the crystallization process of cassiterite based on the analysis of microstructure, chronology and in-situ trace element.LA-ICP-MS cassiterite U-Pb dating of in the Hongqiling tungsten-tin deposit yielded an age of 153.7±2.4 Ma. The color change of CL images of different types of cassiterite from southern Hunan is mainly related to the relative content of Ti, Nb and Ta. The color of CL images is lighter when the content of Ti is high, while the color of CL images is darker when the content of Nb and Ta is high. The Zr/Hf ratio of cassiterite is interpreted as assimilation of wall rock and fractional degree of the ore-forming fluid. Cassiterites from skarn and chlorite vein have a higher Zr/Hf ratio than its ore-bearing granite, which is related to the strata. On the contrary, cassiterites from greisen and chlorite vein show a low Zr/Hf ratio indicating a highly fractionated fluid. The primary and secondary texture developed in cassiterites from chlorite veins and quartz veins demonstrates an opposite change of Fe, W, U content and Zr/Hf ratio, probably implying addition of meteoric water and plused magmatic fluid, respectively.