| 其他摘要 | 中亚造山带是世界上最大的显生宙增生造山带之一，具有显生宙大陆增生、强烈的壳幔相互作用、最大的大陆成矿域和强烈的大陆改造与成矿作用等显著特征。阿尔泰造山带伟晶岩集中分布于中、南阿尔泰构造单元中。在区内呈北西-南东向展布，在大约2×104 Km2的范围内，已发现的伟晶岩脉有近十万余条，90%以上的伟晶岩脉集中分布于38个伟晶岩田内。石英作为伟晶岩的主要矿物之一，与造岩矿物长石、云母相比，石英显示较高稳定性，不易受晚期热液蚀变及表生地球化学过程的影响，不同地质背景下形成的石英其晶格中的微量元素类型及含量存在显著的差异，石英作为一种可靠标型矿物用于火成岩物源示踪、伟晶岩岩浆-热液演化以及热液矿床的成矿过程。本文开展可可托海3号脉及卡鲁安-阿祖拜矿田中五条伟晶岩脉的石英微量元素组成研究，旨在示踪伟晶岩的岩浆-热液演化过程及形成物源，确定伟晶岩中岩浆成因石英形成温度，以及建立伟晶岩型Li矿床找矿的地球化学指标。主要获得以下重要认识：（1）石英阴极发光结果显示，研究的6条伟晶岩脉的石英以暗色为主、裂隙发育明显、未见环带、色度均匀。这些特征表明石英形成于单一环境，不存在多期次结晶或重结晶现象，其内微量元素含量均匀。（2）6条伟晶岩脉中发育的石英中主要类质同象置换为：Al3++Li+→Si4++ 、Al3++P5+→2Si4+，其中Al3++Li+→Si4++ 是最主要的置换方式，石英晶体的生长速度对石英中Al、Li、P的含量变化起到决定性作用。（3）石英Ti温度计计算结果表明，TiO2溶解度所得温度高于TitaniQ公式计算所得，TiO2 的溶解度计算获得的早期岩浆成因石英形成温度与花岗岩低共熔温度接近。此外，由于aTiO2的难以确定，限制了TitaniQ温度计在伟晶岩中的运用，这也是计算出伟晶岩温度较低的原因。（4）在伟晶岩演化方面，可以用Ge、Ti、Al、Li作指示。Ge/Ti与Ge关系表明，可可托海3号脉的岩浆阶段和岩浆-热液阶段具有相似地球化学行为和演化趋势。Ti-Ge图解、Al/Ti-Ge/Ti图解中微量元素含量及比值特征，很可能指示VIII 带中晶出的石英形成于截然不同于I-VI 带中石英的形成环境，VIII 带极有可能是热液阶段形成。（5）所研究的6条伟晶岩脉具有相似的Li与Al相关性，表明它们存在物源或演化上的联系。阿祖拜328号脉、528号脉具有相似的Ge/Ti与Ge变化趋势，表明二者的具有相同的物源。随着演化的进行，伟晶岩中石英中Ti含量逐渐降低而Ge逐渐增大的演化趋势，据此可以推断卡鲁安-阿祖拜伟晶岩岩浆由低到高演化序列为：阿祖拜528 号脉?阿祖拜328号脉?卡鲁安806号脉?卡鲁安807号脉?库卡拉盖650号脉。（6）综合考虑可可托海3号脉的主要Li矿化带和库卡拉盖650号脉中石英中的微量元素组成特征，结合无Li矿化阿祖拜伟晶岩中石英中微量元素组成特征，确定伟晶岩石英中含有>28 ppm Li、>104 ppm Al、>3.5 ppm Ge以及<50 ppm P、<1 ppm Ti可作为伟晶岩型Li矿床找矿的地球化学指标。; The Central Asian Orogenic Belt is one of the largest proliferating orogenic belts in the world. It has significant characteristics such as metamorphic continental growth, strong crust-mantle interaction, largest continental metallogenic field and strong continental transformation and mineralization. The Altai orogenic pegmatite are concentrated in the middle and southern Altai tectonic units. In the area, the Altai orogenic belt is northwest - south east. In the range of about 2×104 Km2, there have been more than 100,000 of pegmatite veins, and more than 90% of the pegmatite veins are distributed in 38 pegmatite fieldQuartz is one of the main minerals of pegmatite. Compared with feldspar and mica, quartz shows higher stability and is less susceptible to late hydrothermal alteration and epigenetic geochemical processes. There are significant differences in the types and contents of trace elements in the lattice of quartz formed in different geological backgrounds. Quartz as a reliable standard mineral, can be used for the igneous source of igneous rocks, magmatic - hydrothermal evolution of pegmatite and metallogenic processes of hydrothermal deposits.In this paper, we study the composition of quartz trace elements in five pegged veins in the Kalu'an-Azubai orefield and the Koktokay No.3 pegmatite vein, aiming at tracing the magmatic-hydrothermal evolution process and the formation source of the pegmatite, determine the forming temperature of magma quartz in the pegmatite, and establishment of geochemical index for prospecting of pegmatite type Li deposit. Mainly gain the following important understanding: (1) Cathode light emission results of quartz show that six studied pegmatite veins of the quartz to dark, fissure developed significantly, no ring, chroma uniform. These characteristics show that quartz is formed in a single environment, there is no multi-stage crystallization or recrystallization phenomenon, the trace elements within the uniform.(2) The main types of quartz in the six pegged veins are replaced by Al3++ Li+ → Si4++ ?, Al3++ P5+→ 2Si4+. Al3++ Li+ → Si4++ ? is the major way. The growth rate of quartz crystal plays an important role in the content of Al, Li and P in quartz.(3) The calculated results of quartz Ti-thermometer show that the temperature obtained by TiO2 solubility is higher than that calculated by TitaniQ formula. The results show that the formation temperature of quartz is close to the eutectic temperature of the granite. In addition, due to the difficult to determine aTiO2, limiting the TitaniQ thermometer in the use of pegmatite, which is to calculate the lower peg crystal temperature reasons.(4) In the evolution of pegmatite, Ge, Ti, Al, Li can be used as an indication. The relationship between Ge/Ti and Ge shows that the magmatic stage and magmatic-hydrothermal stage of the cocoa-taihai veins have similar geochemical behavior and evolution trends. Ti-Ge diagram and Al/Ti-Ge/Ti figure, it is likely to indicate that the formation environment of the quartz in the VIII zone is different from that of the I-VI zone. The VIII zone is likely to be formed in the hydrothermal stage. (5) The 6 pegmatite veins have similar Li and Al correlation, indicating that they exist in the source or evolution of the link. Azubai 328 veins and 528 veins have similar Ge/Ti and Ge trends, indicating that the two have the same source. With the evolution of the progress, the Ti content in the quartz of the pegmatite gradually decreases and the Ge gradually increases. It can be deduced from the low-to-high evolutionary sequence of the Kaluan-Azubai pegmatite from the low-to-high evolutionary sequence: Azubai 528 vein ? Azubai 328 vein ? Kaluan 806 vein ? Kaluan 807 vein ? Kukalagai 650 vein。 (6) Considering the characteristics of trace elements in the main Li mineralization zone of the Koktokay No.3 pegmatite vein and the Kukalagai 650 vein, c ombined with the composition of trace elements in quartz without Li mineralization. The geochemical indicators, > 2 ppm Li, > 104 ppm Al, > 3.5 ppm Ge and<50 ppm P, <1 ppm Ti, can be used as prospector for pegmatite Li deposits. |
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