西藏次玛班硕斑岩铜矿蚀变-矿化样式及找矿潜力

次玛班硕矿床是近年来在冈底斯西段新发现的斑岩型铜矿，距朱诺超大型斑岩铜矿床西南约10 km，周围分布着北姆朗、落布岗木、懂师布等矿床，为朱诺铜多金属矿集区的重要组成部分.为了进一步明确次玛班硕找矿潜力及勘查方向，本次对该矿床开展了系统的锆石U-Pb年代学和锆石微量元素分析、精细的岩芯蚀变-矿化编录以及详细的岩相学观察.研究发现次玛班硕铜矿主成矿期中新世岩体为一套复式杂岩体，分别由细粒二长花岗斑岩（F斑岩:16±0.30 Ma）、粗粒二长花岗斑岩（C斑岩:15.89±0.06 Ma）、含角闪石二长花岗斑岩（H斑岩:15.81±0.06 Ma）、闪长玢岩和二长花岗岩（15.51±0.07 Ma）组成，且不同期次岩浆沉淀Cu金属量差异较大.锆石Ce4+/Ce3+（平均值190）和10 000×（Eu/Eu*）/Y（平均值13）比值指示次玛班硕中新世各岩体，氧逸度和含水性均高于朱诺矿床.次玛班硕热液演化可划分为4个阶段和14种脉体，根据次玛班硕矿床蚀变-矿化对应关系，铜主要沉淀于钾硅酸盐化阶段，特别是与黑云母化密切相关，青磐岩化阶段亦沉淀部分的铜，绢英岩化阶段沉淀最少.与经典的斑岩铜矿蚀变-矿化分带模式不同，次玛班硕铜矿表现出深部钾硅酸盐化被青磐岩化强烈叠加和部分高温脉体穿插低温蚀变的反常特征，证明存在多期次岩浆-热液过程，为成矿提供了源源不断的热动力、成矿物质和成矿流体，形成了各种蚀变相互叠加的复杂热液系统.分布于次玛班硕矿区北部的F斑岩为主要致矿岩体.矿区北部蚀变-矿化作用强而南部较弱，且深部发育强烈的青磐岩化蚀变.综合分析认为，次玛班硕矿床还具有较大的找矿潜力，下一步勘查方向应以矿区深部和北部为主，重点关注F斑岩和C斑岩且发育钾硅酸盐化的部位. 

Alteration-Mineralization Style and Prospecting Potential of Cimabanshuo Porphyry Copper Deposit in Tibet

The Cimabanshuo is a newly discovered porphyry copper deposit in the western part of the Gangdese belt in Tibet. It is located about 10 km southwest of the super-large Zhunuo porphyry copper deposit, which is surrounded by the Beimulang, Luobugangmu, and Dongshibu deposits. These deposits are an important part of the Zhunuo copper ore-concentrated district. To further clarify the prospecting potential and exploration direction of the Cimarbanshuo, a systematic zircon U-Pb geochronology analysis and zircon trace element analysis, elaborate alteration-mineralization cataloging of the drilling, and detailed petrographic observations were carried out for the deposit. The study shows that the Miocene intrusions of the main ore-forming period of the Cimabanshuo copper deposit were a composite pluton, consisting of fine-grained monzonite granite porphyry (F porphyry: 16±0.30 Ma), coarse-grained monzonite porphyry (C porphyry: 15.89±0.06 Ma), hornblende monzonite granite porphyry (H porphyry: 15.81±0.06 Ma), diorite porphyry, and monzonitic granite (15.51±0.07 Ma). Different magmas contribute variously to mineralization. The ratios of zircon Ce4+/Ce3+ (average 190) and 10 000×(Eu/Eu*)/Y (average 13) indicate that the oxygen fugacity and water content of the Miocene rocks in the Cimabanshuo are higher than those in the Zhunuo deposit. The hydrothermal evolution of the Cimabanshuo can be divided into 4 stages and 14 types of veins. According to the correspondence between alteration and mineralization at Cimabanshuo, it concludes that copper mainly precipitates in the K-silicate alteration stage, especially closely related to biotite alteration. Propylitic alteration also contributes to part of the copper and phyllic alteration stage contains the least amount of Cu. Compared with the classic alteration-mineralization zoning model of porphyry copper systems, the Cimabanshuo exhibits some abnormal characteristics, such as a strong superposition of deep K-silicate alteration by propylitic alteration and the low-temperature alteration was cutting by high-temperature veins, indicating that there are multiple stages of magma-hydrothermal processes, which provide a steady stream of thermodynamics, ore-forming materials, and ore-forming fluids for mineralization. The F porphyry is the main mineralizing intrusion, which is distributed in the northern part of the Cimabanshuo deposit.The alteration-mineralization in the north of the mining area is stronger than that in the south, and the deep development of strong propylitization alteration. In conclusion, it believes that the Cimabanshuo deposit also has great prospecting potential. The next step of the exploration should be the deeper levels and northeast direction of the mining area, focusing on the F porphyry, C porphyry, and the zones of K-silicate alteration.