燕辽坳拉槽古—中元古代裂谷盆地演化及其对锰矿沉积的控制作用*

燕辽坳拉槽中元古界高于庄组桑树鞍亚组底部为锰富集层段,虽然对于锰质来源、锰矿成因及形成环境存在认识分歧,但多数学者均认为高于庄组锰矿的形成与燕辽坳拉槽的盆地裂谷背景有着密不可分的联系。在搜集前人锰矿勘查资料的基础上,重点对典型锰矿床——迁西秦家峪锰矿进行了矿床地质特征、矿石类型及元素地球化学分析,结果显示其锰质主要来源于海底热液。通过分析主要锰矿点分布与燕辽裂谷盆地主要断裂之间的关系,发现在裂谷盆地内北东向主断裂与北西向传递断裂的交汇处,或被断裂所围限的闭塞、深水滞流环境,是高于庄组锰矿形成的最有利部位,矿层厚度大,品位相对较高。该研究表明燕辽坳拉槽裂谷盆地结构对高于庄组锰矿的形成具有重要的控制作用,且同沉积断裂作为热液活动的通道,为成锰盆地提供了主要的矿质来源。

Evolution of Yanliao aulacogen in the Paleo-Mesoproterozoic and its control on manganese deposit

It is found that the bottom of Sangshu'an subgroup,which belongs to the Mesoproterozoic Gaoyuzhuang Formation located at the Yanliao aulacogen,is rich in manganese. Although there are still different viewpoints on the origin of manganese and the formation environment of manganese deposits,most scholars believe that the manganese is closely related with the extensive rifting background of the Yanliao aulacogen. In this paper,based on the analysis of exploration data on many manganese ores,the Qinjiayu manganese deposit located at Qianxi belonging to the Yanliao aulacogen,is selected. The manganese ore characteristics,ore types,and element geochemistry are analyzed. The results show that manganese mainly comes from submarine hydrothermal fluids. By analyzing the relationship between the distribution of main manganese deposits and the tectonic faults in the Yanliao aulacogen,it is found that the manganese ore of Gaoyuzhuang formation mainly concentrates at the intersections of the northeast-trending main fault and the northwest-trending transverse fault,and the relatively blocked,deep-water stagnant environment surrounded by faults,where the ore layers are thick and show a relatively high grade. It shows that the structure of the Yanliao aulacogen plays an important role in controlling the formation of Gaoyuzhuang manganese deposits. The syn-depositional faults act as channels for hydrothermal activity,providing a major source of minerals for the manganese-forming basins.