岩脉的侵位机制对成矿作用的约束 ———以内蒙古大井锡多金属矿床为例

摘 要] 岩脉的侵位机制对理解岩脉和矿脉的侵位过程有着重要的意义。本文详细介绍了岩脉 的侵位机制,并以大井锡多金属矿床为例初步探讨了矿区内岩脉与矿脉的关系。研究表明,区域上主要 受NW-SE 向的挤压应力,在海西期向燕山期转变阶段,区域应力场并没有发生变化,只是林西断块发 生了顺时针转动的结果。矿区范围内,同样受NW-SE 向挤压应力作用,块体也发生了相应的变化,推测 矿区西南向北东方向挤压应力逐渐减小,隆升剥蚀量也随之减小。整体上,岩脉侵位于先存裂隙,矿脉 侵位于岩脉形成的构造空间,局部具有互相穿插的现象。通过岩脉和矿脉的侵位过程,认为矿区西部寻 找斑岩型矿床潜力较大。

Constraints of Dike Emplacement Mechanism on Metallogenesis: An example from the Dajing Tin-polymetallic Deposit,Inner Mongolia

Abstract:Mechanism of dike emplacement is significant to understanding intrusion processes of dikes and ore veins. This paper describes the mechanism of dike emplacement,and takes the Dajing ore deposit as an example to discuss the relationship between dikes and ore veins. Our study shows that dikes and ore veins in the region are mainly under the NW-SE directed compressive stress. During the period from the Hercynian to the Yanshanian,the regional stress field remained unchanged,while the block Linxi had a clockwise rotation. Within the Dajing ore deposit area,the NW-SE directed compressive stress was also dominated,and a similar rotation occurred. Thus,we infer that the magnitude of compressive stress declined from SW to NE in the Dajing ore deposit area,and that the amount of uplift and erosion also decreased in this direction. In the whole,dikes intruded into the existing fissures and ore veins took the space of dikes,with local intercalation between dikes and ore veins. We suggest that the western portion of this ore field has a greater potential in search for porphyry-type deposits.