中国北部陆架海碎屑锆石U- Pb年龄和钾长石主微量元素物源示踪研究

渤海湾盆地每年沉积大量的河流碎屑物质，但其中的砂级物质能否迁移扩散到胶东半岛海湾内一直不清楚。锆石和钾长石分别是河流沉积物中常见的副矿物和主要造岩矿物之一，由于各自的U- Pb年龄和地球化学元素组成在不同区域内存在显著差异，是进行物源示踪研究的理想矿物。基于此，本文利用激光剥蚀电感耦合等离子质谱仪 (LA- ICP- MS) 对渤海湾盆地主要注入河流和胶东半岛的威海湾和银滩湾的海岸砂开展碎屑锆石 (n=438) 和钾长石 (n=160) 微区原位U- Pb年龄、Th/U比值和主微量元素分析，结果表明威海湾和银滩湾内的砂级沉积物的碎屑锆石以具有典型的新元古代峰值年龄 (697~735 Ma)，缺乏古元古代和新太古代峰值年龄为特征，Th/U比值和胶东基岩接近，结合Kolmogorov- Smirnov 统计方法的多维判别图 (MDS)，说明这些砂级碎屑物质的源区主要是以胶东半岛为源区的近源物质。而黄河口的碎屑钾长石原位(in situ) Na2O、K2O、Al2O3和Rb、Sr、Ba、Pb元素含量变化与刘公岛和银滩的海砂样品截然不同，进一步验证了上述碎屑锆石的研究结果。因而将碎屑锆石和钾长石原位地球化学分析相结合有助于精准判定物源关系，在今后中国北部陆架海物源示踪研究、渤海湾盆地盆山耦合研究中将具有良好的应用前景。

Detrital zircon U- Pb ages and K- feldspar main and trace elements provenance studying from fluvial to marine sediments in northern China

Zircon is a widely occurring accessory mineral in the fluvial sediments, and is more representative in source tracing studies. Due to its high closed temperature, differences in U- Th- Pb ages, and trace element composition, it preserves source information even after long- distance river transportation. The study on provenance tracer of debris in the Bohai Bay Basin is of great significance in understanding the evolution of this basin, the uplift and erosion process of peripheral orogenic belts, and the material diffusion in the continental shelf sea in eastern China. In this paper, we use the laser ablation inductively coupled plasma mass spectrometry (LA- ICP- MS) to in situ analyze the U- Th- Pb age, and trace element geochemical analysis from the detrital zircon grains of river sediments around the Bohai Bay Basin. Combining previously reported research results with our new results, we show that the age of the Proterozoic zircons in the Yellow River, and the zircon Pb, Th and U element content are different from the other five rivers, and can be used as the source tracer indicators of characteristics of the Bohai Bay Basin. The geochemical signatures characteristic of zircon from the Taihang Mountain can be recognized in the Hutuohe River from the Nb and Y, Pb and Ta element two- dimensional scatter diagram. In future, provenance tracer studies in the Bohai Bay Basin, the U- Th- Pb age of detrital zircons can be combined with trace element changes to accurately determine the potential provenance area.