辽东硼成矿带研究进展

Research progress of the boron mineralization belt in the Liaodong Peninsula

辽东地区是我国重要的硼矿资源产地,赋存硼矿的胶-辽-吉带古元古时期处于活动陆缘环境。辽东硼矿成因为沉积变质再造矿床,硼物质源于蚀变洋壳、俯冲沉积物、蛇纹石化地幔楔等俯冲洋壳系统的富硼地体,在洋壳向克拉通俯冲过程中,硼质在弧前释放进入岛弧火山系统参与热液循环,通过海底热泉等热液方式汇集于火山盆地形成含水硼酸盐初始矿层并被随后的火山沉积覆盖保存。在区域变质变形过程中,含水硼酸盐脱水重结晶并就位于变形构造形成的有利部位富集成矿。辽东硼同位素组成特征反应了对源区储库重硼的继承性,因此,用于探讨矿床成矿地质环境更具意义,而非用于海相和非海相沉积简单的对比。同产于含硼岩系中的含铜硫铁矿矿床沉积时间稍晚于硼矿床,两者空间上呈错位产出,据此可辅助找矿预测工作。区域上虎皮峪-红石砬子-清河复式背斜是辽河旋回多幕变形作用叠加形成的,宏观上控制含硼岩系硼矿床的空间分布。通过总结以往工作,建立了辽东硼矿床成矿模式和找矿模型,分析了找矿方向,特别指出的是,部分盖县岩组地层出露地区,深部具有寻找隐伏硼矿的探索空间,未来找矿前景可期。

The Liaodong Peninsula(LP)is an important metallogenic region of boron in China.The Jiao-Liao-Ji Paleoproterozoic orogenic belt/active belt(JLJ)adjacent to the LP hosts boron deposit formed in a continental active margin setting.The boron deposits in the LP are considered to be resulted from sedimentary-metamorphic reworking mineralization.The boron materials in the LP originated from altered seafloor,subducted sediments,serpentinized mantle wedge in the boron-enriched subducted oceanic system.The boron materials were released from the subducted units at sub-arc depth and were transported upward into the upper mantle and island arc volcanic system.The pristine borate beds in the volcanic basin were enriched by the submarine hot spring,and were isolated by subsequent volcanic-sedimentary covers.The mineralization of borate was associated with the regional metamorphism and deformation.The hydrous borates underwent metamorphic dehydration and re-crystallization and then precipitated in deformation-developed regions.The boron isotopes of boron deposits in the LP strongly inherit from the heavy B isotopic source reservoirs,and thus provide insights into the metallogenic environment of the boron deposits.The copper-bearing pyrite deposits posterior to the boron deposits are located adjacent to the volcanic feeders,whereas the boron deposits formed in the volcanic basin.Accordingly,the boron prospecting is suggested to taking into account of the paleogeographic study by combining the spatiotemporal relations between pyrite deposits and boron deposits.The Hupiyu-Hongshilazi-Qinghe acticlinoria,as a result of multiple and superimposed deformation in the Liaohe tectonic cycling,broadly controlled the spatial patterns of the boron deposits.In conclusion,we established the metallogenic and prospecting models of boron deposits in the LP,and analyzed prospecting criteria of boron deposits in the LP.It is emphasized that the stratum areas partially covered by the Gaixian Formation have the potential for prospecting the concealed boron deposits in future.