摘要
本文对西藏厅宫大型铜矿进行了详细研究,矿床详细的地质岩相学-蚀变以及典型剖面填图表明,矿区存在2个岩浆事件高峰,即始新世的钾长花岗岩（~50 Ma）和中新世的斑状二长花岗岩、英云闪长斑岩及闪长玢岩（约13~17 Ma）。野外和室内研究发现,厅宫矿区存在2期重要的矿化事件,即始新世（~50 Ma）铜矿化及中新世（~15Ma）的铜钼矿化。始新世含矿岩体为钾长花岗岩,其最主要的特点是其成矿岩体结构的特殊性,表现在该矿床的成矿岩体没有典型的斑状结构,而是独特的细晶-似伟晶结构,说明含矿岩浆发生过骤冷,可能是流体突然逃逸,矿物结晶的固相点发生漂移所致。同时,该岩体还发育大量显微文象结构、显微晶洞构造等,均说明岩浆曾经富水,并且曾经流体饱和;中新世含矿岩体为具有埃达克岩特征的斑状二长花岗岩,主要以脉状的铜、钼矿化为主。该矿床蚀变分带类似于冈底斯带其他斑岩矿床。时间上,分别为早期的钾硅酸盐化、转换阶段的青磐岩化、随后的绢英岩化及最晚期的泥化蚀变;空间上,以含矿岩体为中心向外依次为钾硅酸盐化、绢英岩化、青磐岩化,最晚期的泥化呈补丁状或条带状叠加早期各类蚀变。铜矿化主要发生在始新世的黑云母化阶段和中新世的绢英岩化阶段,而钼矿化主要发生在中新世的钾硅酸盐化和绢英岩化的转换阶段。
Tinggong is a large porphyry Cu deposit located in the western segment of the Gangdise porphyry Cu belt in southern Tibet. It contains 1.49 Mt of Cu with an average grade of 0.362 % and 0.04 Mt of Mo with an average grade of 0.018% . The deposit consists of both collisional and post-collisional stage porphyry-type Cu systems, which are genetically associated with the early Eocene coarse-and fine-grained granite and the Miocene monzogranite porphyry stock, respectively. It is the most important deposit in the Gangdise porphyry Cu belt, but geology of the deposit remains poorly constrained. In this paper, the authors conducted a detailed study of geological features of the deposit, so as to （1） document the geological characteristics （e. g., alteration and min- eralization） of the deposit; （2） investigate intrusive sequences and magma source of main intrusions in the de- posit;（3） investigate tectonic control of intrusion emplacement, alteration and mineralization; （4） track fluids evolution process; and （5） determine genesis of the deposit. On such a basis, the authors formulated a genetic model for the Tinggong deposit. The authors surveyed the petrography-alteration of the Tinggong copper de- posit, and exactly determined the distribution of formations and magmatites. In combination with zircon U-Pb isotope dating results of other researchers, the authors built up a detailed series of magma evolution. It is shown that there existed two peaks of magmatic events, i.e., K-feldspar granite in Eocene （ --50 Ma） and porphyritic monzonite granite, tonalite porphyry and diorite porphyry in Miocene （ 13 -- 17 Ma）. Through field and lab re- search, the authors have come to the conclusion that there occured two phases of mineralization events in the Tinggong deposit, i.e., copper mineralization in Eocene （ --50 Ma） and Cu-Mo mineralization in Miocene （ 15 Ma）. Moyite formed in Eocene, which has a particular texture, i.e., it has no classical porphyritic texture but shows unique fine grain-like pegmatite texture. This suggests the existence of sudden cooling of the ore-bear- ing magma, which might have been caused by the sudden escape of fluids. There also exist large quantities of micro graphic texture, quartz eyes and some other textures. These special textures imply that the magma was rich in water and the fluid was once in a saturation state. Porphyritic monzonite granite was associated with Cu- Mo mineralization in Miocene. The alteration zoning of the deposit is similar to that of other porphyry deposits in Gangdise. In term of time, the alteration was potassic alteration in early period, propylitization occurred in a transitional phase, followed by phyllic alteration and argillization. In term of space, from the core to the outer part there are potassic alteration, phyllic alteration, and propylitization. The latest argillization exhibits patch or banded form, superimposed upon other alterations of earlier time. The authors described all kinds of alterations, mineral assemblages and associated veins in detail and dealt with the evolution process of the fluid as well as the source and accumulation mechanism of metals.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2015年第4期447-474,共28页
Acta Petrologica et Mineralogica
基金
国土资源部行业科研专项(201011011)
国家基础研究规划"973"项目(2011CB403104)
地质调查资助项目(1212011220908)
关键词
蚀变分带
岩浆演化序列
斑岩铜矿床
厅宫
冈底斯
西藏
alteration zoning
magma evolution sequence
porphyry Cu deposit
Tinggong
Gangdise
Tibet
作者简介
杜等虎（1986-），男，汉族，硕士研究生，矿物学、岩石学、矿床学专业，E-mail：dudenghu@126．com；
通讯作者：杨志明（1978一），男，汉族，副研究员，主要从事斑岩铜矿研究，E-mail：zm．yang@hotmail．com。
