摘要
胶东型金矿床受断裂构造控制,断裂控矿规律一直是地质勘查和研究的重点问题。为深入研究断裂对金成矿的控制作用,本文基于大量矿床勘查和地质调查资料,通过对典型断裂剖面和断裂与矿体空间关系的构造解析,判断了成矿期断裂的性质和应力状态,讨论了断裂产状变化的控矿机理,提出了胶东型金矿新的构造成矿模式。将胶东主要控矿断裂分为Ⅰ级缓倾角断裂、Ⅱ级陡倾角断裂和Ⅲ级陡倾角张裂脉,三者分别控制了破碎带蚀变岩型、复合类型和石英脉型金矿床。金矿体主要赋存于断裂产状转折部位,蚀变岩型矿体赋存于断裂的倾角变缓部位,石英脉型矿体赋存于断裂倾角变陡部位。缓倾角断裂控制的矿体具有总体侧伏角小、富矿柱侧伏角大的“双向”侧伏特征。矿体产状与断裂产状的关系指示,三山岛、焦家和招平三条控矿断裂成矿期均属右行正滑或右行张扭性,金牛山断裂具有左行正滑特征。根据金矿体产状分析的胶西北金成矿小区区域构造应力场σ1为294°∠82°和269°∠78°,焦家断裂的σ1为300°∠67°、311°∠78°和321°∠81°,招平断裂北段σ1为130°∠65°和138°∠69°,反映了胶西北玲珑花岗岩体分布区域总体以垂向主压应力为主,其东、西两侧的边界断裂处的主压应力方位分别沿SE向和NW向指向岩体,成矿期断裂处于NW—SE向拉张状态。胶东东部邓格庄金矿田的σ1为287°∠0°,以水平主压应力为主。综合分析认为,产状变化的具张扭性质的断裂是金的有利赋矿构造,断裂的产状变化对金矿体具有明显的控制作用,断裂结构和流体性状的变化是金矿阶梯成矿的关键因素,断裂沿走向和倾向的产状转折联合控制了金矿体的侧伏。胶东地区早白垩世深部大量岩浆岩快速侵位,导致地壳强烈隆升产生伸展构造,来自不同深度和层次岩浆房及不同源区的岩浆梯次上侵,为深部含金流体活化、迁移提供了热动力条件和流动通道,含金流体到达地壳浅部在断裂产状变化的减压扩容空间卸载成矿。
The Jiaodong type gold deposits are controlled by a faulted structure. Structural control of ore deposition has always been the focus of geological exploration and research. For expanding the study on the fault control of gold mineralization based on a large number of ore deposits exploration and geological survey data, through the structural analysis of typical faults sections and the spatial relationship between faults and ore bodies, this paper determined the properties of the faults and stress state in metallogenic period, and discussed the ore-controlling mechanism by fault attitude change, and proposed a new structural metallogenic model of the Jiaodong type gold deposits. The main ore-controlling faults in the Jiaodong Peninsula are divided into grade I gently dip fault, grade Ⅱ steeply dip fault, and grade Ⅲ steeply dip tensile veins, which controlled the fracture altered rock type gold deposits, composite type gold deposits and quartz vein type gold deposits respectively. Gold ore bodies mainly occur at the turning part of the fault attitude. Altered rock type ore bodies occur at the part where fault dip angle decreases. However, quartz vein type ore bodies occur in the part where fault dip becomes steeper. Ore bodies controlled by the gently dipping fault have the characteristics of “double pitch” where the overall pitch angle is small and pitch angle of ore shoot is large. The relationship between the ore bodies attitude and the fault attitude indicates that the Sanshandao, the Jiaojia and the Zhaoping ore-controlling faults all belong to dextral normal slip fracture or right-lateral transtensional fault during mineralization, while the Jinniushan fault has the characteristics of left-lateral normal slip. The σ1(regional tectonic stress field) of the Jiaoxibei gold metallogenic district, the Jiaojia fault and northern section of the Zhaoping fault is 294°∠82°and 269°∠78°;300°∠67°, 311°∠78° and 321°∠81°;and 130°∠65° and 138°∠69°, respectively. These indicate that the distribution area of the Linglong granitic pluton in the northwest of Jiaodong Peninsula is mainly dominated by vertical principal stress, while the principal stress orientation of the boundary faults on the east and west sides is along the SE—NW direction to the pluton, and the faults are in NW—SE extensional state during mineralization. The σ1 of the Denggezhuang gold field in eastern Jiaodong is 287°∠0°, and is dominated by horizontal principal stress. It is concluded that the faults with variable occurrence and tensional property are favorable ore-hosting structures for gold deposits, and the change of fault attitude has obvious control on gold ore bodies. The key factor of stepped mineralization of gold deposit is the change of fault and fluid properties. The attitude transition of fault along strike and dip jointly controls the pitch of gold ore bodies. The rapid emplacement of a large number of deep magma during the Early Cretaceous in the Jiaodong Peninsula resulted in strong crustal uplift that generates extensional structure. Magma from different depths and source regions intruding in echelon provide thermodynamic conditions and flow channels for activation and migration of deep gold-bearing fluid. The gold-bearing fluid arrived at the shallow crust and mineralization occurred in the decompression and expansion space of fault attitude change.
作者
宋明春
丁正江
刘向东
李世勇
李健
董磊磊
魏绪峰
鲍中义
王斌
张琪彬
张亮亮
刘洪波
贺春艳
SONG Mingchun;DING Zhengjiang;LIU Xiangdong;LI Shiyong;LI Jian;DONG Leilei;WEI Xufeng;BAO Zhongyi;WANG Bin;ZHANG Qibin;ZHANG Liangliang;LIU Hongbo;HE Chunyan(Shandong Provincial No.6 Exploration Institute of Geology and Mineral Resources,Weihai,Shandong 264209,China;Shandong Institute of Geophysical and Geochemical Exploration Jinan,Shandong 250013,China;College of Resources and Environmental Engineering,Shandong University of Technology,Zibo,Shandong 255000,China;University of Science and Technology Beijing,Beijing 100083,China;Shandong Provincial No.3 Exploration Institute of Geology and Mineral Resources,Yantai,Shandong 276006,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2022年第5期1774-1802,共29页
Acta Geologica Sinica
基金
国家自然科学基金项目NSFC-山东联合基金“胶东深部金矿断裂控矿机理”(编号U2006201)资助的成果。
关键词
控矿断裂
胶东型金矿床
主应力
断裂性质
阶梯成矿
热隆-伸展构造
ore controlling fault
Jiaodong type gold deposits
principal stress
fracture properties
stepped mineralization
thermal doming-extension
作者简介
宋明春,男,1963年生。博士,研究员,构造地质专业,主要从事地质矿产勘查及相关研究。E-mail:mingchuns@163.com。
