甘肃省阳山金矿控矿构造分析及其意义

Ore-control Structure Analysis and Significance of the Yangshan Gold Deposit,Gansu Province,China

阳山金矿产于勉阳-略阳板块缝合带中,经历了以逆冲推覆构造为主的复杂构造改造。通过构造研究把阳山金矿内的构造分出四期。第一期构造变形表现为由北向南逆冲,为韧性变形,构造置换明显、完全,形成透入性面理,剪切褶皱、无根褶皱、S-C组构、压力影、旋转碎斑、多米诺骨牌、石香肠等构造发育,构造岩为糜棱岩、超糜棱岩、构造片岩,并伴随有大规模的花岗岩岩浆活动,形成于三叠纪末-早侏罗世。第二期构造变形为由南向北的伸展构造,主要表现对第一期面理的改造和再利用,多为韧性变形,可见剪切褶皱、旋转碎斑等构造,构造岩为糜棱岩,顺层张性石英脉的发育,并伴随有大规模的岩浆活动,形成于侏罗纪末-早白垩世早期。第三期构造为脆韧性变形,为由南向的北逆冲推覆构造,主要表现为对先期构造的改造,使阳山金矿区南部面理产状发生倒转,形成膝折构造,构造岩为糜棱岩、初糜棱岩,形成于早白垩世晚期。第四期构造为表层次脆性的由南向北的伸展构造,形成构造角砾岩、碎裂岩等脆性构造岩,同时有石英脉和方解石脉顺断层侵入,本期构造形成于古近纪。

Located at Mianyang-Lueyang plate suture zone, Yangshan gold deposit experienced the transforma-tion of the complex structural system that the main structural features were the thrust-nappe structures. According to route geological survey and drill core record, we divided the structural period of Yanshan gold deposit based on the research of small structure and identified four structural periods. Faults were the main structure and folds were subordinate structure in Yangshan gold deposit.The first period of structural deformation was ductile defor-mation and thrusted form north to south.There were obvious and complete transposition structures , and a lot of ductile deformed structures, such as shear folds, rootless folds, S-C fabrics, pressure shadows,rotating mortar sys-tems, domino structures, and boudinage. The first deformed period formed in Late Triassic- Lower Jurassic , which tectonites were mylonites, ultramylonites and tectonic schists as well as massive granite magmatism.The structural deformation of the second period was extensional structure, trending north to south direction,which changed and reuseed the first period foliation structures. The structures of two period were small-angle cross-cut-ting or parallel output. The structures of the second period showed ductile deformation that formed shear folds, fo-tating mortar systems,which tectonites was mylonites. Bedding tensional quartz veins developed as well as mas-sive granite magmatism. The second period structures formed in Late Jurassic-early Lower Cretaceous. The struc-tures of the third period were brittle-ductile deformation showed thrust-nappe structure inverse rushed form south to north. The structures mainly showed the transformation of the early structures, and specific performed the re-verse of the foliation attitude in the southern area of Yanshan gold deposit, （i. e. foliation tendency changed from north to south）, formed kink structures. The third deformed period formed in the late period of Lower Cretaceous, which tectonites were mylonites and protomylonites. The structures of the fourth period were surface-level brittle deformation,which was extensional structure trending south to north direction. Structural breccias cataclasites, bedding tensional quartz veins and calcite veins along the period faults formed . The structures of the fourth peri-od formed in the Paleogenecentry.