通过博格达山北麓白杨河剖面芦草沟组页岩的地球化学特征的综合研究,讨论了芦草沟组页岩的元素富集特征和沉积环境以及源区物源特征和构造背景。结果表明: ① 研究区页岩P元素极为富集,这受控于页岩中凝灰质火山灰夹层的广泛发育; ② 对比于世界页岩微量元素分布,白杨河页岩相对富集Li、B、Pr、Tb、Dy、Ho、Er、Tm和Lu元素,其他元素相对亏损; ③ 白杨河剖面页岩地化参数揭示芦草沟组自下而上气候由温湿向干热转变,进而引起水体由淡水向咸水的转变和还原程度的进一步加强; ④ 物源区遭受低级-中等风化程度,物源类型主要为长英质火成岩,其次为铁镁质火成岩; ⑤ 物源区大地构造背景以大陆岛弧-活动大陆边缘构造背景为主。
英文摘要:
Based on the comprehensive research on geochemical characteristics of shale of Lucaogou Formation along the Baiyanghe profile in the northern Bogda Mountain in Xinjiang,the authors investigated the elements distribution and depositional environment of shales of Lucaogou Formation,source characteristics and tectonic setting of the source area. Some conclusions have been reached: ① Baiyanghe shale is evidently enriched in phosphorus, which is ascribed to the development of the volcanic ash,as indicated by the tuffaceous composition of the interbedded mudstone and carbonate layers. ② In comparison with the average concentrations of worldwide shales,the Baiyanghe shale is enriched mainly in Li,B,Pr,Tb,Dy,Ho,Er,Tm and Lu,and depleted in other elements relative to their average values. ③ Geochemical characteristics reveal that there occurred climate change from warm humidity to dry heat from the bottom to top of Lucaogou Formation,which caused the change from freshwater to saltwater and strengthened gradually the reducing environment from the bottom to top of Lucaogou Formation. ④ The source area was under the low-moderate chemical weathering condition. The provenance of shales was mainly felsic igneous rock,followed by femic igneous rock. ⑤ The tectonic setting of the source area was a continental island arc-active continental margin.