冀东“长城式”金矿的成因探讨

The Origin of the "Changcheng Type" Gold Deposits in East Hebei

区域构造和成矿特征研究表明 ,进入燕山期 ,华北地区开始了幔枝构造活动期 ,沿冀东茅山 金厂峪 肖营子EW向韧性剪切带与NNE向迁安 青龙韧性剪切带强烈活动。特别是 2条韧性剪切带交汇部位的肖营子一带 ,岩浆大规模侵入 ,形成了以肖营子斑状花岗岩为主体的一系列大小侵入体。并带动变质围岩一起强烈隆升 ,中上元古界盖层则向外大幅度拆离滑脱 ,以致于轴部岩浆 变质杂岩呈揭顶式裸露 ,冷口 清河沿岩块就是由于受冷口断裂或反向铲状断裂活动影响 ,而残留在岩浆 变质杂岩之上的中元古界岩块。在岩块拆离滑脱过程中所形成的主拆离滑脱带、次级拆离滑脱带及层间滑动断裂成为较发育的构造扩容空间。主成矿期含矿流体沿构造扩容带贯入、聚集和成矿 ,形成一系列构造蚀变岩型、脉型矿体。新房子金矿的深部钻孔已证实了这种认识。矿体顶部的变宽及变富则是隆升过程中崩塌及风化淋滤造成的浅部表现。因此 。

Based on geologic characteristics, ore forming material sources and modes of occurrence of 'Changcheng type' gold deposits, this paper deals mainly with the genetic mechanism of such deposits. Studies of regional geological and metallogenic features show that North China region entered the stage of mantle branch structure activity in Yanshanian period, and strong activation occurred along EW striking Maoshan Jinchangyu Xiaoyingzi ductile shear zone and NNE striking Qianan qinglong ductile shear zone in East Hebei. Large scale magmatic intrusion took place at the intersection of the two ductile shear zones, forming Xiaoyingzi porphyritic granite as well as a series of big and small intrusive bodies. At the same time, intensive uplifting of this area resulted in the outcropping of the magmatic metamorphic complex along the axis and the detachment of Mid-Upper Proterozoic covers. The activity of Lengkou fault or reversed listric faults formed fault step and caused the Lengkou Qingheyan fault block to remain as the Mid Upper Proterozoic remnant block over magmatic metamorphic complexes. The main and second detachment belts as well as interformational faults were formed during the gliding of rock masses, and became well developed structural expanding space. Therefore, the ore bearing fluids migrated up, injected and aggregated along these structural expanding belts during the main metallogenic stage, forming a series of structural altered type and vein type deposits. This recognition has been confirmed by deep drill holes in the Xinfangzi gold field. The widening and enrichment phenomena at the top of the orebody is the shallow expression resulting from collapse and leaching during the upward migration. Thus, special attention should be paid to the search for deep orebodies.