藏东芒康县巴达铜金矿床地质特征及找矿方向研究

doi:10.13745/j.esf.sf.2020.4.12

地学前缘 ›› 2020, Vol. 27 ›› Issue (4): 232-243.DOI: 10.13745/j.esf.sf.2020.4.12

藏东芒康县巴达铜金矿床地质特征及找矿方向研究

杨富成¹(), 李文昌¹^,²^,³^,^*(), 祝向平²^,³, 江小均⁴, 刘俊³, 廖忠礼³, 刘鸿飞⁵, 杨后斌⁴, 李勇³

1.中国地质大学(北京) 地球科学与资源学院, 北京 100083
2.成都理工大学地球科学学院, 四川成都 610059
3.中国地质调查局成都地质调查中心, 四川成都 610081
4.昆明理工大学国土资源工程学院, 云南昆明 650093
5.西藏自治区地质调查院, 西藏拉萨 850000

收稿日期:2020-01-05 修回日期:2020-03-27 出版日期:2020-07-25 发布日期:2020-07-25
通信作者: 李文昌
作者简介:杨富成(1994—),男,博士研究生,矿物学、岩石学、矿床学专业。E-mail: 446369580@qq.com
基金资助:
国家自然科学基金项目(41272091);云南省科学技术杰出贡献奖项目(2017001);中国地质调查局地质调查项目(DD20160016);中国地质调查局地质调查项目(DD20179604)

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

YANG Fucheng¹(), LI Wenchang¹^,²^,³^,^*(), ZHU Xiangping²^,³, JIANG Xiaojun⁴, LIU Jun³, LIAO Zhongli³, LIU Hongfei⁵, YANG Houbin⁴, LI Yong³

1. School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China
2. School of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China
3. Chengdu Geological Survey Center, China Geological Survey, Chengdu 610081, China
4. School of Land and Resources Engineering, Kunming University of Science and Technology, Kunming 650093, China
5. Tibet Institute of Geological Survey, Lhasa 850000, China

Received:2020-01-05 Revised:2020-03-27 Online:2020-07-25 Published:2020-07-25
Contact: LI Wenchang

摘要/Abstract

摘要：

巴达铜金矿位于藏东富碱斑岩带南段,是藏东地区近年来新发现的大型铜金矿。虽然对巴达铜金矿开展了大量勘查工作,但对该矿床的成因尚未取得共识。本文基于详细的野外调研、岩心与坑道编录及系统的镜下鉴定,对巴达铜金矿床地质特征进行研究。巴达矿床主要产于石英二长斑岩中,局部产于斑岩和砂岩地层的接触带内。矿床发育的围岩蚀变主要为青磐岩化、钾化、绢英岩化,高岭土化、蛋白石化、蒙脱石化次之,蚀变分带从内向外依次为钾硅酸盐化带、绢英岩化带、青磐岩化带、高岭土化带,铜金矿体主要赋存于钾硅酸盐化和绢英岩化带内,铜矿化主要以黄铜矿形式产出,金矿化主要以银金矿形式产于白云石±石英+细粒黄铁矿±黄铜矿脉中,铜矿化与金矿化呈正相关,矿体的产出受北西向逆冲断层的控制。与典型斑岩和浅成低温热液矿床不同,巴达铜金矿化主要产于白云石±石英+黄铁矿脉中;矿床内既发育碳酸盐、伊利石、绢云母和黄铁矿、黄铜矿、方铅矿、黝铜矿、低FeS闪锌矿等一套中硫型浅成低温热液矿床的蚀变矿物组合,又发育符合碱性斑岩系统的特征矿物赤铁矿。基于以上特征判断,巴达铜金矿矿床成因类型应为与富碱斑岩有关的浅成低温热液矿床,巴达铜金矿矿床成因的厘定,为下一步找矿提供了理论指导。

关键词: 巴达铜金矿床, 浅成低温热液矿床, 中硫型, 藏东富碱斑岩成矿带, 描述模型

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

中图分类号:

杨富成, 李文昌, 祝向平, 江小均, 刘俊, 廖忠礼, 刘鸿飞, 杨后斌, 李勇. 藏东芒康县巴达铜金矿床地质特征及找矿方向研究[J]. 地学前缘, 2020, 27(4): 232-243.

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.

图/表 8

图1 昌都—芒康成矿带区域地质图(据文献[20]修编)

Fig.1 Geological map of Changdu-Mangkang metallogenic belt. Modified from [20].

图2 巴达铜金矿地质简图(a)和A-B勘探线剖面蚀变分带图(b) (据文献[15])

Fig.2 Geological map (a) and alteration zoning of A-B exploration line profile (b) in Bada Cu-Au deposit. Adaped from [15].

图3 巴达铜金矿岩浆岩照片 a—石英二长斑岩,斑状结构,斑晶以钾长石、斜长石、角闪石、黑云母为主;b—石英二长斑岩钾长石、斜长石、角闪石、黑云母镜下(正交偏光)特征;c,d—二长斑岩,斑状结构,斑晶以钾长石、斜长石为主;e—云母煌斑岩,煌斑结构,斑晶成分以黑云母为主;f—云母煌斑岩黑云母镜下(正交偏光)特征。Kf—钾长石;Pl—斜长石;Bt—黑云母;Am—角闪石。

Fig.3 Photomicrographs of magmatic rocks specimen from the Bada Cu-Au deposit

图4 巴达铜金矿典型蚀变、脉体特征 a,b—青磐岩化宏观和镜下照片;c—石英脉、石英+白云石脉;d,e—钾化宏观和镜下照片;f—白云石脉穿切白云石+石英+钾长石+黄铁矿±黄铜矿脉;g,h—绢英岩化宏观照片;i—白云石脉穿切白云石+石英+方铅矿+黄铁矿±黄铜矿脉;j—高岭土化叠加钾化;k—蛋白石化;l—蒙脱石化。Ep—绿帘石;Chl—绿泥石;Dol—白云石;Kf—钾长石;Bt—黑云母;Ser—绢云母;Kaol—高岭土;Opal—蛋白石;Mont—蒙脱石;Q—石英;Py—黄铁矿;Cp—黄铜矿;Gn—方铅矿。

Fig.4 Photos and photomicrographs of wall rock specimens from the Bada Cu-Au deposit showing typical alterations and veins

表1 巴达铜金矿床蚀变矿物组合特征

Table 1 Characteristics of altered mineral assemblages of the Bada Cu-Au deposit

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

图5 巴达铜金矿3号坑道内F5断层含矿脉体产出特征

Fig.5 Photos of ore specimens (top) and schematic diagram (bottom) illustrating the characteristics of the ore-bearing veins of the F5 fault in the No.3 tunnel in the Bada Cu-Au deposit

图6 巴达铜金矿矿化特征 a—白云石-石英-黄铜矿脉;b—黄铜矿和方铅矿共生的显微照片;c—产于长石石英砂岩中的粗粒黄铁矿(PyI);d—粗粒黄铁矿显微照片;e—细粒黄铁矿(PyII)和方铅矿共生;f—黄铜矿、细粒黄铁矿和方铅矿共生的显微照片;g—细粒黄铁矿与毒砂、脆硫锑铅矿共生的扫描电镜照片;h—细粒黄铁矿和石英颗粒间分布的粒间金的扫描电镜照片;i—白云石+石英+细粒黄铁矿±黄铜矿脉中分布的包体金的扫描电镜照片。 PyI—自形-半自形粗粒黄铁矿;PyII—细粒黄铁矿;Cp—黄铜矿;Gn—方铅矿;Au(Ag)—银金矿;Jm—脆硫锑铅矿;As—毒砂;Q—石英。

Fig.6 Photos and photomicrographs of ore specimens from the Bada Cu-Au deposit displaying mineralization characteristics

图7 巴达铜金矿床成矿预测模型

Fig.7 A metallogenic prediction model for the Bada Cu-Au deposit

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藏东芒康县巴达铜金矿床地质特征及找矿方向研究

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

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