Geological characteristics and prospecting of the Bada Cu-Au deposit in Mangkang County, East Tibet

doi:10.13745/j.esf.sf.2020.4.12

Abstract

Abstract:

The Bada Cu-Au deposit, a newly discovered large Cu-Au deposit, is located in the southern part of the alkali-rich porphyry belt in East Tibet. The metallogenic features of the Bata Cu-Au deposit are not yet clear. Based on detailed field observation, geological logging and systematic microscopic examination, we studied the geological characteristics of the Bada Cu-Au deposit. The deposit developed within the quartz monzonite porphyry intrusion while the surrounding sandstones are controlled by a NW-striking thrust fault. We identified the alteration types, including potassic, phyllic and propylitic alterations, and delineated the alteration zones. We also found small quantity of localized secondary minerals such as kaolinite, opal and montmorillonite. The Cu-Au orebody mainly occurs in the potassic and phyllic alteration zone, showing positive correlation between Cu and Au mineralization. Copper mineralization mainly produces chalcopyrite, while gold occurs primarily as fine Ag-Au grains in dolomite±quartz+pyrite±chalcopyrite vein. Both alteration and mineralization are centralized along the NW-striking thrust fault. Unlike typical porphyry and epithermal deposit, mineralization in the Bada Cu-Au deposit mainly occurs in dolomite±quartz+pyrite vein, resembling the low temperature alteration assemblage. The alteration and mineralization associated minerals, such as carbonate, illite, sericite, galena, pyrite, chalcopyrite and tetrahedrite, are found in the ore district, consistent with intermediate sulfidation epithermal deposits. Moreover, hematite is ubiquitous, indicating an alkaline porphyry system. Thus, we conclude that the Bada Cu-Au deposit belongs to alkali-rich porphyry related epithermal deposit. Its metallogenic mechanism can be used to guide the next prospecting exploration.

Key words: Bada Cu-Au deposit, epithermal deposit, intermediate sulfidation, alkali-rich porphyry belt in East Tibet, description model

CLC Number:

YANG Fucheng, LI Wenchang, ZHU Xiangping, JIANG Xiaojun, LIU Jun, LIAO Zhongli, LIU Hongfei, YANG Houbin, LI Yong. Geological characteristics and prospecting of the Bada Cu-Au deposit in Mangkang County, East Tibet[J]. Earth Science Frontiers, 2020, 27(4): 232-243.

Figures/Tables 8

References 46

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蚀变类型	主要矿物	少量矿物	蚀变强度和类型	产出位置	矿石组成
青磐岩化	绿泥石、绿帘石	赤铁矿、磁铁矿	弱—强,绿帘石局部交代辉石,绿泥石主要沿角闪石解理或颗粒边部发生局部交代	普遍发育,分布于浅部—深部石英二长斑岩中
钾硅酸盐化	钾长石、黑云母	磁铁矿	弱—强,主要呈脉体晕的形式产于白云石±石英脉两侧,局部由正长石沿钾长石边部向核部进行近完全交代	中部—深部石英二长斑岩中	自然金、银金矿、黄铁矿、黄铜矿
绢英岩化	绢云母、伊利石、石英	黄铁矿	中等—强,主要呈脉体晕的形式产于浅绿色白云石+石英+黄铁矿脉两侧,其次为绢云母-伊利石局部交代长石	中部—深部石英二长斑岩中	自然金、银金矿、黄铜矿、黄铁矿、方铅矿
高岭土化	高岭土		中等—强,钾长石近完全蚀变为高岭土,叠加深部钾硅酸盐化	浅部和深部石英二长斑岩中

蚀变类型	主要矿物	少量矿物	蚀变强度和类型	产出位置	矿石组成
青磐岩化	绿泥石、绿帘石	赤铁矿、磁铁矿	弱—强,绿帘石局部交代辉石,绿泥石主要沿角闪石解理或颗粒边部发生局部交代	普遍发育,分布于浅部—深部石英二长斑岩中
钾硅酸盐化	钾长石、黑云母	磁铁矿	弱—强,主要呈脉体晕的形式产于白云石±石英脉两侧,局部由正长石沿钾长石边部向核部进行近完全交代	中部—深部石英二长斑岩中	自然金、银金矿、黄铁矿、黄铜矿
绢英岩化	绢云母、伊利石、石英	黄铁矿	中等—强,主要呈脉体晕的形式产于浅绿色白云石+石英+黄铁矿脉两侧,其次为绢云母-伊利石局部交代长石	中部—深部石英二长斑岩中	自然金、银金矿、黄铜矿、黄铁矿、方铅矿
高岭土化	高岭土		中等—强,钾长石近完全蚀变为高岭土,叠加深部钾硅酸盐化	浅部和深部石英二长斑岩中