西藏龙根铅锌矿床矽卡岩矿物学特征及其地质意义

Mineralogical Characteristics of Longgen Skarn-Type Pb-Zn Deposit in Tibet and Its Geological Significance

龙根铅锌矿床位于念青唐古拉铅锌多金属成矿带西段,目前该矿床的矿物学特征研究较为薄弱。以主要矽卡岩矿物为研究对象,利用电子探针技术对其矿物学特征进行了研究。龙根铅锌矿床是由深部岩浆结晶分异产生的成矿流体从深部向上运移过程中,在温度与压力的驱动下沿灰岩和花岗斑岩的岩性分界面选择性交代形成,属于岩浆热液接触交代型矿床。研究结果表明:龙根铅锌矿床从花岗斑岩至灰岩矽卡岩矿物分布具有良好的空间分带性,矿床从早到晚可划分为2个成矿期、5个成矿阶段;成矿环境由早期的弱酸性、中低温、高氧逸度转变为晚期的碱性、较低温度、较高氧逸度;矿床不限于铅锌矿化,深部可能有Cu-Mo矿的成矿潜力,下一步矿区勘探工作应该围绕岩体接触带进行布置,继续往深部进行勘查。

The Longgen Pb-Zn deposit is located in the west of the Nyainqentanglha Pb-Zn polymetallic metallogenic belt. Currently, its mineralogical characteristics are not quite identified. This paper investigates its mineralogical characteristics by using electron microprobe technology with skarn minerals as the study object. The Longgen Pb-Zn deposit is a process in which the ore-forming fluids produced by the deep magma crystallization gradient move up from the deep, and are selectively formed by the temperature and pressure along the lithologic interface between limestone and granite porphyry. The Longgen Pb-Zn deposit belongs to the magmatic hydrothermal contact metasomatism type deposit. The study results indicate that the Longgen Pb-Zn deposit has a good spatial zoning distribution from granite porphyry to limestone skarn minerals. The deposit can be divided into two metallogenic phases and five mineralization stages. The metallogenic environment changes from weak acidity, low temperature, high oxygen fugacity to alkaline, lower temperature, and higher oxygen fugacity from early stage to late stage. The deposit is not limited to Pb-Zn mineralization, and there may be potential for the formation of Cu-Mo deposits in the deep. The exploration should be arranged around the contact belts of the rock in the deep in the following work.