黑龙江五道岭组地层时代划分及其与钼矿的关系

五道岭组是黑龙江重要的与成矿关系密切的陆相火山岩地层,长期以来对它的地质时代存在不同认识.本文依据近几年新取得的同位素测年数据,结合与五道岭组紧密伴生的花岗岩类的时代研究,以及对五道岭组火山岩类与伴生花岗岩类的地球化学特征对比研究,提出五道岭组地层时代属于晚三叠世—早侏罗世的新认识.论述了五道岭组火山岩类、晚三叠世—早侏罗世花岗岩类和与前二者关系密切的钼矿是在大体相同的地质时代依次相继形成.较早的陆相火山喷发形成五道岭组火山岩地层,随后发生多阶段的花岗岩类侵入,而钼矿在同源岩浆演化到更晚阶段形成.五道岭组火山岩类和晚三叠世一早侏罗世花岗岩类具有相同的岩浆起源,它们分别是同源岩浆在不同演化阶段和不同深度的产物,因而在时空关系、岩石化学、微量元素、稀土配分和同位素组成等方面表现了明显的一致性.五道岭组地层与钼矿及花岗岩类的密切时空关系和成因联系可用于评价钼矿成矿远景区.

THE STRATIGRAPHIC AGE AND RELATIONSHIP WITH MOLYBDENUM OF THE WUDAOGOU FORMATION IN HEILONGJIANG PROVINCE

The Wudaoling Formation,which is closely related to mineralization,is a set of significant continental volcanic strata in Heilongjiang Province. Arguments have long existed about its geological age. Based on new isotopic data,with geochronological study on the granitoids that are closely associated with the Wudaoling Formation,as well as the geochemical comparison of the volcanic rocks and associated granites,this paper proposes a new recognition that the Wudaoling Formation can be defined from Late Triassic to Early Jurassic epoch. It is also identified that the molybdenum deposits in the area were formed closely related to the volcanic rocks of Wudaoling Formation and the Late Triassic-Early Jurassic granites in an approximately same geologic period. The Wudaoling volcanic formation was formed by earlier continental volcanic eruption,followed by multistage intrusion of granitoids,and then the molybdenum deposits were formed in the later stages of comagmatic evolution. The volcanic rocks of Wudaoling Formation and the Late Triassic-Early Jurassic granitoids are products of a single source at different evolution periods and depths. Therefore,there is a clear consistency in the space-time relationship,petrochemistry,trace elements,REE patterns and isotopic composition between them. The close space-time and genetic relationship between the Wudaoling Formation,the associated granitoids and the molybdenum deposits can be applied in the assessment for molybdenum metallogenic prospective areas.