内蒙古大井铜锡多金属矿成矿物质来源及成矿作用探讨

Source of ore-forming materials and mineralization of the Dajing Cu-Sn polymetallic deposit, Inner Mongolia

大井铜锡多金属矿以矿床规模大、伴生元素多、矿脉展布窄而密集、品位较高而著称。但是,矿区范围勘探并没有发现燕山期岩体,矿床成因众说纷纭。笔者从幔枝构造视角研究认为,矿区位于大兴安岭幔枝构造核部,地幔热柱多级演化沟通了深部含矿流体,并沿途萃取部分成矿物质,在有利的成矿构造裂隙中集聚成矿。而成矿控矿裂隙的方向性则与成矿阶段区域构造应力场密切相关。至于在矿区内部的Sn、Cu、Au、Ag、Pb、Zn成矿元素的分带性,应与成矿作用及成矿物质结晶温度有关,结晶温压条件较高的Sn、Cu、Au等元素矿化多位于矿区中部,而结晶温压条件较低的Ag、Pb、Zn等元素矿化则多位于矿区的外围。

The Dajing Cu-Sn polymetallic deposit is characterized by its large size, many associated elements, narrow and dense ore veins and high grades. However, no Yanshanian intrusions were found within the limits of the ore field, so the genesis of the deposit is in controversy. From a viewpoint of mande branch tectonics, the deposit is situated at the core of the Da Hinggan Mountains mande branch, and the multiple evolution of the mande hot plume linked up the deep hydrothermal ore fluids. The ore fluids extracted some ore materials on the way, which concentrated in favorable structural fractures and formed the deposit. The orientation of ore- controlling fractures is closely related with the regional structural stress field during mineralization. The zoning of the ore-forming elements Sn, Cu, Au, Ag, Pb and Zn within the deposit should be related to mineralization and crystallization temperatures of ore materials. The mineralizations of the elements such as Sn, Cu and Au, which crystallized under higher P-T conditions, are in the center of the ore field; whereas the mineralizations of the elements such as Ag, Pb and Zn, which crystallized under lower P-T conditions, were mostly localized in the surroundings of the deposit.