老挝班康姆铜金矿床“岩浆核杂岩”隆起-拆离带构造控矿特征

doi:10.19657/j.geoscience.1000-8527.2024.097

摘要/Abstract

摘要：

老挝班康姆铜金矿床位于东南亚思茅—彭世洛地块南缘构造活跃带,是与中生代岩浆岩有关的大型铜金矿床。该区具有巨大的资源潜力,但地质研究程度相对较低,其成矿模式和演化规律等理论问题尚未完全解决。本文通过对成矿岩体分布特征、断裂构造变形特征和拆离带构造成矿特征的研究,揭示矿床岩浆核杂岩隆起特征与拆离带构造特征,认为班康姆矿床受控于“岩浆核杂岩”及其边界的隆起-拆离带构造,为岩浆核杂岩隆起-拆离带构造热液铜金矿床。班康姆矿床“岩浆核杂岩”构造由“岩浆杂岩体核、拆离带构造和火山-沉积岩”三个部分组成,岩浆杂岩体核主要由花岗闪长岩组成。花岗闪长岩与安山岩和灰岩接触带下盘发育有似片麻理构造,片理产状以核部花岗闪长岩为中心,呈现外倾的特征,推断为岩浆岩上侵过程中受到区域挤压剪切应力的作用形成。磁法和激电测量结果,反映班康姆矿床矿化蚀变带和岩浆核杂岩的分布关系,结合地质实测的岩体分布信息,推测深部存在隐伏岩体。拆离带构造发育于下盘花岗闪长岩体与上盘火山-沉积岩之间,是铜金矿化的集中地段,且拆离带构造中矿化蚀变岩的形成年龄(244~251 Ma),晚于杂岩体侵位年龄(264±10 Ma)。通过对拆离带构造及两侧小型构造观测与分析,可知拆离带构造剖面上呈上陡下缓的“铲”式形态学特征,具有明显的早期韧性变形、晚期脆性变形的特点,其上盘的主运动方向为NWW向。本文提出班康姆铜金矿床的东南部同样具有“岩浆核杂岩”隆起-拆离带构造成矿模式的特征,为有利的找矿靶区。

关键词: 班康姆铜金矿床, 岩浆核杂岩隆起, 拆离带构造, 成矿特征

Abstract:

The Bankangmu copper-gold deposit, located in the tectonically active zone at the southern margin of the Simao-Phetchabun block in Southeast Asia, is a large copper-gold deposit associated with Mesozoic magmatism.Despite the significant resource potential of this area, some key geological questions remain unresolved, such as those related to ore-forming models and evolutionary processes.This paper investigates the distributions of ore-forming intrusions, fault structure deformation features, and ore-forming characteristics within the detachment zone to reveal the uplift features of the magmatic core complex and the structural characteristics of the deposit in this zone.This study posits that the Bankangmu deposit is controlled by the structure of the “magmatic core complex” and its boundaries within the uplift-detachment zone, categorizing it as a hydrothermal copper-gold deposit formed in this magmatic core complex uplift-detachment zone.The magmatic core complex structure of the Bankangmu deposit consists of three parts: the magmatic complex core, the detachment zone structure, and the volcanic-sedimentary rocks.The magmatic complex core is mainly composed of granodiorite.At the contact zone between the granodiorite-andesite and limestone in the footwall, a gneiss-like texture has developed.The foliation, centered on the core granodiorite, exhibits an outward dip and is inferred to have formed under regional compressive shear stress during the magmatic intrusion processes.Magnetic and induced polarization measurements reveal the relationship between the mineralized zone and the magmatic core complex in the Bangkangmu deposit.Combined with geological survey data on the distribution of intrusions, we suggest that there is a concealed intrusion deeper whithin the structure.The detachment zone structure, developed between the footwall granodiorite and the hanging wall volcanic-sedimentary rocks, is the focal area for copper-gold mineralization.The formation age of the mineralized alteration rocks in the detachment zone (244-251 Ma) is younger than the emplacement age of the complex (264±10 Ma).Observations and analyses of the detachment zone structure and small-scale structures on both sides indicate that the detachment zone exhibits a shovel-shaped morphology in cross-section.It is characterized by distinct early ductile deformation followed by later brittle deformation, with the main movement direction of the hanging wall being NWW.Consequently, this paper suggests that the southeastern part of the Bankangmu copper-gold deposit also exhibits characteristics of the magmatic core complex uplift-detachment zone ore-forming pattern, making it a potential target for exploration.

Key words: Bankangmu copper-gold deposit, magmatic core complex uplift, detachment zone structure, ore-forming characteristics

中图分类号:

赵俊宏, 杨人毅, 吕古贤, 赵延朋, 康铁锁, 陈晓峰. 老挝班康姆铜金矿床“岩浆核杂岩”隆起-拆离带构造控矿特征[J]. 现代地质, 2024, 38(04): 1067-1075.

ZHAO Junhong, YANG Renyi, LÜ Guxian, ZHAO Yanpeng, KANG Tiesuo, CHEN Xiaofeng. Ore-controlling Structural Characteristics of the Bankangmu Copper-Gold Deposit in Laos: Magmatic Core Complex Uplift-Detachment Zone[J]. Geoscience, 2024, 38(04): 1067-1075.

图/表 6

图1 老挝班康姆铜金矿床地质简图 (a)研究区范围图;(b)图中:1.石炭系—二叠系灰岩;2.矽卡岩化大理岩;3.石炭系—二叠系泥质砂岩;4.二叠系—三叠系安山质凝灰岩;5.花岗闪长岩;6.二叠系—三叠系安山质火山岩;7.剖面铜金矿化体;8.平面图铜金矿化体及编号;9.岩浆核杂岩推断范围;10.拆离带构造;11.糜棱岩带;12.正断层;13.似片麻理;14.研究区范围;15.物化探工作范围;16.地质和勘探剖面;17.地质观测点及产状

Fig.1 Simplified geological map of the Bankangmu copper-gold deposit in Laos

图2 老挝班康姆铜金矿床花岗闪长岩似片麻理照片 (a)花岗闪长岩体东部似片麻理照片;(b)花岗闪长岩体北部似片麻理照片;(c)花岗闪长岩体西部似片麻理照片

Fig.2 Photographs of gneiss-like granodiorite from the Bankangmu copper-gold deposit in Laos

图3 老挝班康姆铜金矿床高精度磁异常和激电异常平面图 1. 石炭系—二叠系地层;2.花岗闪长岩;3.二叠系—三叠系安山岩;4.金矿体及编号;5.断层及编号

Fig.3 High-resolution magnetic and induced polarization anomaly map of the Bankangmu copper-gold deposit in Laos

图4 老挝班康姆铜金矿床19-100号勘探剖面图(剖面位置见图1)[10] 1. 石炭系、二叠系灰岩;2.石炭系、二叠系砂岩;3.石炭系、二叠系大理岩; 4.二叠系—三叠系安山岩; 5.花岗闪长岩; 6.挤压片理;7.铜金矿体;8.断层及编号

Fig.4 Exploration section 19-100 of the Bankangmu copper-gold deposit in Laos (location of section shown in Fig.1)[10]

图5 老挝班康姆铜金矿床物化探剖面图 (a)Au、Cu元素化探测量剖面;(b) 磁法和激电测量剖面

Fig.5 Geophysical and geochemical survey profiles of the Bankangmu copper-gold deposit in Laos

图6 老挝班康姆铜金矿床拆离带构造两侧构造现象照片 (a)小型褶皱;(b)S-C组构;(c)糜棱岩条带;(d)矿化角砾岩;(e)碎裂岩;(f)阶步擦痕构造

Fig.6 Photographs of structural features on both sides of the detachment zone in the Bankangmu copper-gold deposit in Laos

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