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云南思茅盆地白垩纪—古新世地层包括曼岗组(K_1m)、扒沙河组(K_1p)、勐野井组(K_2me)、等黑组(E_1d),主要由砂岩及砂泥岩组成。对盆地江城二官寨—和平寨—扒沙河道班剖面19件碎屑岩样品及江城勐野井矿区SHK4孔17件细碎屑岩样品的主量元素、稀土元素和微量元素进行了分析。结果显示:碎屑岩样品中δCe和δEu、δCe与∑REE、化学蚀变指数(CIA)与Th/U、CIA与Th/Sc不具有相关性,说明研究区白垩纪—古新世沉积物碎屑成分主要受控于源岩特征,不受化学风化作用及氧化-还原条件的影响;稀土元素配分模式基本相同,LREE/HREE值较高且负Eu异常明显,表明白垩纪—古新世沉积物具有相同的物源,岩石以亲花岗岩、长英质岩为主。Hf-La/Th、La/Sc-Co/Th、REE-La/Yb、Hf-Co-Th判别图解也反映了相似的物源特征。勐野井组至等黑组地层沉积期间,CaO含量、Gd含量、ICV值和(Gd/Yb)N值突然增加,表明源区自晚白垩世勐野井组沉积开始,构造活动性突然加强,整体上处于快速隆升、剥蚀阶段。研究为云南思茅盆地白垩纪—古新世沉积物物源属性的判别提供了一定的地球化学依据。
The Cretaceous-Paleocene strata of the Simao Basin in Yunnan Province consist of K_1m, K_1p, K_2me and E_1d, and are mainly composed of sandstone and sandstone and mudstone. The main elements, rare earth elements and trace elements of 19 samples of clastic rocks in the section of Gangguan-Hepingzhai-Shasha Channel of the Jiangcheng area and 17 samples of finely-divided clastic rocks of SHK4 in the Jiangmen Mengnojing Mine Area were analyzed. The results show that there is no correlation between δCe, δEu, δCe and ΣREE, chemical alteration index (CIA) and Th / U, CIA and Th / Sc in the clastic rocks, indicating that the Cretaceous-Paleocene sediments The detrital components are mainly controlled by the source rock characteristics, and are not affected by chemical weathering and oxidation-reduction conditions. The REE patterns are basically the same with high LREE / HREE values and obvious negative Eu anomalies, indicating that the Cretaceous-Paleocene The sediments have the same provenance. The rocks are mainly pro-granite and feldspathic rocks. Hf-La / Th, La / Sc-Co / Th, REE-La / Yb and Hf-Co-Th discriminant maps also reflect similar provenance characteristics. The CaO content, Gd content, ICV value and (Gd / Yb) N value suddenly increase during the formation of strata from Mengyejing Formation to the ishigant formation, indicating that the tectonic activity suddenly strengthened since the Late Cretaceous Mengyejing Formation, On the rapid uplift, erosion stage. The study provided some geochemical evidences for distinguishing the provenance properties of Cretaceous-Paleocene sediments in the Simao Basin, Yunnan Province.