摘要
液压致裂是整个地壳−岩石圈范围内一种重要的变形破裂方式,也是一些热液矿床的重要含矿构造。通过分析液压致裂构造的形成机制和液压成因含矿构造的类型(液压致裂型和液压撑开型),以华南地区典型热液钨、铀矿为例,基于野外精细调查,明确了包括石门寺钨矿、行洛坑钨矿和邹家山铀矿等的液压成因含矿构造的基本特征。新生性液压致裂含矿构造的主要特征表现为形态复杂(有弧形、分叉树枝形、放射状、菊花形和蟹腿状等)、规模较小、宏观力学性质以张性破裂为主、走向和倾向多变、方向性不明显、仅局部区域发育优势方位、常伴生有热液隐爆角砾岩;因此,可以从弧形分叉或不规则形态、总体较小规模、产状多向性、分布不均匀性和伴生热液隐爆角砾岩这5个标志来识别液压致裂含矿构造。对比分析液压致裂含矿构造与应力致裂含矿构造的差异认为,液压致裂含矿构造发育比较局限,而液压撑开型含矿构造相对普遍,热液蚀变分带与该含矿构造是液压致裂还是应力致裂无明显相关性;压性成因构造在成矿期表现出的张性力学性质有些是成矿流体超压作用的结果,而并非区域构造应力场的改变;液压致裂导致的断裂末端的扩展破裂与成矿流体的耦合作用为成矿末端效应的构造控制机制。
[Objective]Hydraulic fracturing is a vital deformation and fracture mode in the whole crust-lithosphere range.The related structures are also critical ore-bearing structures of some hydrothermal deposits.Clarifying the main characteristics and identification marks of hydraulic fracturing ore-bearing structures aids in conducting detailed structural analyses of ore fields.[Methods]The article introduces the formation mechanism of hydraulic fracturing structures and classifies the hydraulic ore-bearing structures into two types,namely,hydraulic fracturing and hydraulic spreading.Taking typical hydrothermal tungsten and uranium deposits in South China as examples,the study,based on detailed field investigations,analyzes the essential characteristics of hydraulic fracturing ore-bearing structures,including the Shimensi tungsten deposit,Xingluokeng tungsten deposit and Zoujiashan uranium deposit.[Results]The study suggests that hydraulic fracturing ore-bearing structures are characterized by complex shapes(arc-shaped,branched,radial,chrysanthemum-shaped,etc.),relatively small scale,predominantly tensional macro-mechanical properties,variable trends and dips,indistinct directionality with dominant orientations in only local areas,and often accompanied by hydrothermal crypto-explosive breccia.Meanwhile,five typical marks of the hydraulically fractured ore-bearing structures have been identified,including arc bifurcation or irregular shape,overall small scale,multi-directional occurrence,uneven distribution,and associated hydrothermal crypto-explosive breccia.[Conclusion]After comparing and analyzing the similarities and differences between hydraulic fracturing ore-bearing structures and stress-induced ore-bearing fracturing,the study concludes that hydraulic fracturing ore-bearing structures are relatively limited in development.In contrast,hydraulic spreading fracturing ore-bearing structures are relatively common.There is no apparent correlation between the hydrothermal alteration zoning and whether the ore-bearing structure is due to hydraulic fracturing or stress-induced fracturing.Tensional structural features exhibited by compressional genesis structures during the mineralization period are attributed to overpressure from mineralizing fluids rather than changes in regional tectonic stress fields.Although the orebearing structures of compressive origin show tensional macro-mechanical properties during the metallogenic period,some result from the overpressure of ore-forming fluids rather than the change in the regional tectonic stress field.[Significance]As an important ore-bearing structure type,hydraulic fracturing enriches the connotation of ore field structure.The coupling effect between the extensional fracturing of fracture ends caused by hydraulic fracturing and ore-forming fluids is an essential mechanism of structural control of the ore-forming end effect,which will enhance the theory of structural ore control and contribute to breakthroughs in prospecting strategies.
作者
陈柏林
CHEN Bailin(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China)
出处
《地质力学学报》
CSCD
北大核心
2024年第1期15-37,共23页
Journal of Geomechanics
基金
国家重点研发项目(2016YFC0600207,2017YFC0602602)
中国地质科学院地质力学研究所基本科研业务费项目(JYYWF20180602)。
关键词
液压致裂构造
含矿构造
裂隙形态
热液隐爆角砾岩
鉴别标志
华南热液矿床
hydraulic fracturing structure
ore-bearing structure
fracture morphology
hydrothermal cryptoexplosive breccia
identification mark
hydrothermal deposits in South China
