陕西省镇安县庙沟口一带梅子垭组构造期次划分及其与金矿化关系

RELATIONSHIP BETWEEN TECTONIC STAGES AND GOLD MINERALIZATION OF THE MEIZIYA FORMATION IN MIAOGOUKOU,ZHEN′AN COUNTY OF SHAANXI PROVINCE

镇安庙沟口一带梅子垭组为主要含矿地层,其主要岩性为绢云母千枚岩、碳质千枚岩、粉砂质千枚岩,少量硅质岩、变砂岩,极少量灰岩。梅子垭组经历了加里东期、华力西期、印支期以及燕山期等多期构造变形,明显可识别出四幕构造变形:第一幕为华力西期伸展构造体制形成的韧性折叠层变形,发育假塑性流变构造群;第二幕为南秦岭印支期挤压造山构造体制形成的叠加构造变形,形成了本区基本构造格架;第三、四幕为南秦岭微板块板内调整构造体制形成的浅层脆性构造变形,以脆性断裂和节理构造变形为特征,对本区金矿体具有破坏作用。其中第二幕构造变形晚期形成的韧—脆性剪切带同时形成了本区的金矿体。

Meiziya Formation in Miaogoukou area of Zhen′an is the main ore-bearing stratum,which is manly composed by sericite phyllite,carbonaceous phyllite,silty phyllite,a small amount of siliceous rock,metasandstone and a small amount of limestone.The Meiziya Formation experienced Caledonian,Variscan,Indosinian and Yanshanian structural deformation,from which four episodes of structural deformation can be identified obviously.The first episode is the deformation of the ductile fold layer formed by the Variscan extensional structural system,in which pseudoplastic rheological structural group developed;The second is the superimposed structural deformation formed by the Indosinian compressional orogenic structural system of the South Qinling Mountains,forming the basic structural framework in this area;The third and fourth episodes are the shallow brittle structural deformation formed by adjusting the structural system in the South Qinling microplate,which is characterized by brittle fracture and joint structural deformation and has destructive effect on the gold ore bodies in this area.In the second episode,gold mineralization formed in the ductile brittle shear zones in the late stage of structural deformation in this area.