胶西北断裂构造蚀变分带及其铲式分布特征

胶东是全球最大的与中生代花岗岩有关的热液交代蚀变金矿集中区,其成矿与断裂及蚀变作用有关。以焦家断裂和招平断裂为典型,开展构造变形蚀变岩剖面实测和地质填图,研究控矿断裂铲式分布的地质特征。研究发现:(1)断裂蚀变带的宽度不是以往认为的几十米,而是达到几百米,或超过千米,蚀变的规模和强度控制了成矿作用;(2)断裂产状上陡下缓,浅部-200 m以上倾角在70°左右,深部-400 m以下倾角20°到30°,形成铲式断裂;(3) 铲式断裂显示上盘下滑的运动特征,应力应变特征表明成矿作用发生于应力松弛阶段;(4)断裂的倾向控制矿化带的侧伏方向,焦家断裂带倾向北西而其中矿体向南西侧伏;招平断裂倾向南东则矿体为北东向侧伏。

Structural Alteration Zone and Listric Distribution Characteristics in Northwest Jiaodong Peninsula

Jiaodong is the world’s largest Mesozoic granite-related hydrothermal/metasomatic gold province, and the gold mineralization is related to faulting and alteration. In this paper, the Jiaojia and Zhaoping faults are taken as typical examples to study the geological characteristics of the listric ore-controlling fault distributions, through measuring the deformation and alteration profile and geological mapping. The results revealed that: (1) the fault alteration zone is hundreds of meters to over kilometers wide, instead of meters as previously suggested. The scale and intensity of alteration control the gold mineralization. (2) Orientation for the upper and lower part of the fault is steep and gentle, respectively. Dip angle for the shallow (above -200 m) and deeper (below -400 m) parts of the fault is around 70° and 20°-30°, respectively. The fault morphology is listric. (3) The listric fault indicates motion characteristic of sliding hanging wall, and the stress-strain features show that the mineralization occurred in the regional stress relaxation stage. (4) Dip direction of the fault controls the lateral trend of the mineralized zone. The Jiaojia fault dips to the NW, and the associated mineralization zone trends SW; the Zhaoping fault dips to the SE, and the associated mineralization zone trends NE.