摘要
砂岩型铜矿床(沉积岩容矿层状铜矿床)作为一种重要的铜矿床广泛发育于滇西兰坪盆地内。经典的砂岩型铜矿床成因模式认为该类矿床形成于伸展背景下的沉积盆地内,但兰坪盆地内的砂岩型铜矿床则产出于挤压背景下的陆-陆碰撞造山带内,其成矿与地壳缩短密切相关。通过详细构造解析揭示成矿与构造变形的时空关系是理解挤压背景下铜成矿过程的基础。本文基于12.5万区域地质调查,详细分析了白洋厂砂岩型铜矿床的区域构造、矿体与构造的空间关系。构造分析结果显示,矿区白垩系经历了中新世东西向挤压变形,形成近南北走向逆断层+近东西走向掀斜-走滑断层构造组合;地壳缩短期间,在主要逆断层前锋(下盘)形成中新世含石膏层的小型周缘前陆盆地。铜多金属矿化发生在逆断层主破碎带或上盘次级破碎带内,赋矿围岩皆为白垩系。基于构造-盆地-矿体这一空间关系,结合矿石结构、区域地质特点,我们提出成矿金属元素主要源自中新世周缘前陆盆地卤水,还原硫来自隐伏于白垩系之下的晚三叠统三合洞组中的还原性流体。始于中新世早期的地壳缩短在晚三叠世、白垩纪地层中形成破裂构造,使得中新世周缘前陆盆地中的卤水下渗、保存于晚三叠世地层中的还原性流体上升,而当两种流体在主要断裂破碎带内发生混合时,则发生硫化物沉淀成矿。
Sedimentary rock-hosted stratiform copper deposits(sandstone-type Cu-deposit),one of the most important Cu-deposit types,are widespread in the Lanping Basin,the SE Tibetan Plateau.Traditionally,sandstone-type Cu-deposit is believed to be formed in sedimentary basins in an extensional setting.However,in contrast to the classical sandstone-type deposits elsewhere in the world,the Cu-deposits in the Lanping Basin developed in foreland basins due to crustal shortening.As a result,available metallogenic models of classical sandstone-type Cu-deposit cannot explain the mineralization features of those in the Lanping Basin.The first step to understand mineralization process of a Cu-deposit formed in a contract tectonic background is to reveal the spatial relationship between the structures and the ore-bodies.On the basis of 1/25,000 regional geological mapping,we conducted detailed structural analysis in the Baiyangchang Cu-deposit district to reveal the structures and the spatial relationship between the structures and the Cu-ore bodies.The Cretaceous strata of the Baiyangchang Cu deposit experienced E-W compression,which gives rise to a series of S-N-trending reverse faults.These reverse faults are cut across by numerous E-W-trending tear faults.These faults form typical thrust-and-tear fault associations.A few small-scale peripheral foreland basins with gypsum horizons developed upon the footwalls of some reverse faults during E-W compression.Cu-mineralization occurred solely in the fracture-zones along the main fault planes or other sites of the hanging walls of the reverse faults.Such a spatial distribution of the ore-bodies,combined with textures and mineral assemblages of the ore-bodies as well as other regional geological data,suggests that the metals were likely sourced from brine fluid of the Miocene foreland basin,while reduced fluid probably came from the foot-wall Upper Triassic Sanhedong Formation.Since the Early Miocene,E-W compression led to numerous fractures or faults in the Cretaceous and Late Triassic
作者
信迪
杨天南
梁明娟
廖程
董猛猛
王维
刘靖坤
XIN Di;YANG TianNan;LIANG MingJuan;LIAO Cheng;DONG MengMeng;WANG Wei;LIU JingKun(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Geological Museum of Guizhou,Guiyang 550081,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China;Department of Earth Sciences,Kunming University of Science and Technology,Kunming 650093,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第11期3515-3530,共16页
Acta Petrologica Sinica
基金
自然资源部深地动力学重点实验室自主研究课题(J1901-4)
国家自然科学基金项目(92055206、42163007、41373049、42163007)联合资助.
关键词
白洋厂砂岩型铜矿床
构造解析
逆断层-掀斜走滑断层组合
地壳缩短
构造控矿
Baiyangchang sandstone Cu-deposit
Structural analysis
Thrust-and-tear fault associations
Crustal shortening
Structural ore control
