长江中下游地区铜地球化学块体时间属性——来自碎屑锆石LA-ICP-MS U-Pb定年的证据

Temporal Distribution of Copper Geochemical Blocks in the Middle–Lower Yangtze River Region:Evidence from Detrital Zircon LA-ICP-MS U-Pb Dating

利用水系沉积物地球化学组合数据在长江中下游地区共圈定出6个铜地球化学块体,首次利用碎屑锆石LA-ICP-MS U-Pb定年技术对地球化学块体的时间属性进行了研究。在铜矿床最为发育的Cu1、Cu2和Cu6三个块体内的碎屑锆石样品中清楚地识别出4个年龄峰值,分别对应古元古代、新元古代、早古生代和中生代。表明地球化学块体是跨时代存在的,物质来源于多期地质事件。新元古代和中生代地质体对研究区铜地球化学块体的形成也具有重要影响。研究还发现,成矿物质经后期的风化分散作用会进入到水系沉积物中,通过水系沉积物采样能够捕获成矿信息。

A total of six copper geochemical blocks in the Middle–Lower Yangtze River region were delineated on the basis of composite stream sediment geochemical data.The detrital zircon LA-ICP-MS U-Pb dating technique was used to study the temporal properties of geochemical blocks for the first time.Four age peaks were identified in detrital zircon samples sampled in Cu1,Cu2 and Cu6 geochemical blocks,corresponding to Paleoproterozoic,Neoproterozoic,Early Paleozoic,and Mesozoic,respectively.The authors have reached the conclusion that geochemical blocks exist across the time,and substances in the range of geochemical blocks came from multiple geological events.It is believed that Neoproterozoic and Mesozoic geological bodies had important influence on the formation of copper geochemical blocks.It is shown that the ore-forming materials might have been transported into stream sediments through later weathering and dispersion.Mineralization information could be extracted by sampling stream sediments.