康滇古陆东缘筇竹寺组地球化学特征及意义

云南省昭通市昭阳区锌厂沟位于康滇古陆东缘，在剖面测量及样品系统采集分析基础上，建立了该区下寒武统筇竹寺组泥页岩地球化学剖面，为该区筇竹寺组沉积环境、物源分析提供了定量的地球化学数据。研究结果显示:1）筇竹寺组物源主要来自康滇古陆中元古界东川群、会理群砂泥岩、海相玄武岩，并可能有少许同时代花岗岩，形成于康滇古陆东缘大陆坡或边缘海，自西向东呈康滇古陆—潮坪—浅水陆棚—深水陆棚—水下隆起有序变化，工区位于浅水陆棚相；2）稀土元素δCe值、δEu值及微量元素Mo、V含量、（V）_N/（V+Ni）_N比值、（Cu）_N/（Zn）_N比值反映筇竹寺组底部为深水陆棚环境，上部总体为浅水陆棚沉积环境，局部水体加深为深水陆棚沉积环境。总体上该区以浅水陆棚为优势相，并具酸性还原环境特点；3）微量元素Rb、Ba、Ga、V、Zn、Mo、Cd、Sn、Zr有明显的富集。主量元素（SiO₂）_N/（Al₂O₃）_N比值及微量元素Ba、U含量、Zn-Ni-Co三角图、U/Th比值、Co/Zn比值表明有生物或热水作用的参与。

Geochemical Characteristics and Significance of the Qiongzhusi Formation on the Eastern Margin of the Ancient Kangding-Yunnan Land:Taking the Xinchanggou section of Zhaoyang district,Zhaotong city,Yunnan province as an example

Xincchanggou， Zhaoyang district， Zhaotong city， Yunnan province， is located in the eastern margin of the ancient Kangding-Yunnan land. Based on the profile measurement， sample collection， and analysis， a geochemical profile for the mud and shale of the Lower Cambrian Qiongzhusi Formation is established in this area， which provides quantitative geochemical data for the sedimentary environment and provenance analyses of the Qiongzhusi Formation. The research conclusions are as follows: （1） the characteristic parameters of the principal elements （Al）_N/（A+Fe+Mn）_N， （Si）_N/（Si+Al+Fe）_N， the MnO/TiO₂，（Al₂O₃）N/（Al₂O₃+Fe₂O₃）_N，（Al₂O₃）/（Al₂O₃+Fe₂O₃）-Fe₂O₃/TiO₂ discrimination diagram， and the relationship diagram of rare-earth elements La/Yb-Ce/La indicate that the provenance of the Qiongzhusi Formation mainly comes from the sand-mudstone and marine basalt of the Dongchuan Group and Huili Group of the Middle Proterozoic， and there may be a few contemporary granites in provenance. It was formed on the continental slope or marginal sea of the eastern margin of the ancient land of Kangdiing-Yunnan. From west to east， it presented an orderly change of the ancient land of Kangding-Yunnan， tidal flat， shallow water shelf， deep water shelf， and underwater uplift， and the work area was located in the shallow water shelf facies； （2） the δCe and δEu values of rare earth elements， the Mo and V contents， the（V）_N/（V+Ni）_N ratio， and the （Cu）_N/（Zn）_N ratio of trace elements reflect that the bottom of the Qiongzhusi Formation is a deep-water shelf environment， the upper part is generally a shallow water shelf sedimentary environment， and the water body occasionally deepens into a deep-water shelf sedimentary environment in the upper part. On the whole， the shallow-water shelf is the dominant facies in this area， and it has the characteristics of an acid reduction environment； （3） the trace elements Rb， Ba， Ga， V， Zn， Mo， Cd， Sn， and Zr were significantly enriched. The main element （SiO₂）_N/（Al₂O₃）_N ratio， trace element Ba，U content， Zn-Ni-Co trigonometric diagram，U/Th ratio， and Co/Zn ratio indicate that biological or hot water action is involved.