| 思茅盆地MK-3井上盐段成盐期前后微量元素地球化学特征及其古环境指示意义 |
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| 引用本文：宋高,苗忠英,杜少荣,李新民.2022.思茅盆地MK-3井上盐段成盐期前后微量元素地球化学特征及其古环境指示意义[J].地球学报,43(4):584-592. |
| DOI：10.3975/cagsb.2022.011201 |
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| 基金项目:中国地质调查局地质大调查项目“思茅盆地中生代海相钾盐资源调查评价”(编号: DD20201115) |
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| 中文摘要:本文通过对比分析思茅盆地MK-3钻孔上盐段成盐期前后碎屑沉积物微量元素及稀土元素的地球化学特征, 探讨了思茅盆地中生代盐层形成前后的气候环境变化规律。结果表明, 主要微量元素中除Mn元素之外, 其余元素在成盐期之前的平均含量均大于成盐期之后, 指示微量元素富集有利于盐矿床的形成。以球粒陨石标准化样品稀土元素的相对含量, 结果显示轻稀土元素相对富集、重稀土元素相对亏损, 标准化曲线呈现左高右低的“L”型, 表明其物质来源主体为陆源。MK-3钻孔29个岩心样品的δCe值均大于0.9, 均值约为1.0, 结合岩芯样品主体呈现棕红色, 应指示一种弱氧化的沉积环境。综合沉积物的Rb/K和Sr/Cu比值分析, 我们认为在成盐期之前, 该区气候炎热干旱、蒸发强烈, 水体盐度为半咸水, 具备析盐、成钾的古气候和古环境条件。成盐期之后, 该区古盐度处于淡水-咸水交替的状态, 伴有三段温暖湿润期和三段极端炎热干旱期。后期淡水补给持续增强, 导致沉积盆地内在上盐段蒸发析盐之后只发育碎屑岩。 |
| 中文关键词:思茅盆地 碎屑岩 微量元素 地球化学 古环境 |
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| Geochemical Characteristics of Trace Elements before and after the Upper Salt Forming Period of the MK-3 Core, Simao Basin and Their Paleoenvironmental Implications |
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| Abstract:We discuss the paleoenvironment changes before and after the Mesozoic salt forming period in the Simao Basin by comparing the geochemical characteristics of trace elements in clasolite along the upper salt section of the MK-3 core. The average contents of major trace elements, except Mn, were higher before the salt forming period than after it, indicating that the enrichment of trace elements is beneficial for the formation of salt deposits. The chondrite normalized relative content of rare earth elements show a pattern of light rare earth element enrichment with an incline to the right, suggesting that the main material source is terrigenous. δCe values of all 29 samples in MK-3 are greater than 0.9, with an average value of 1.0. Considering the brownish red core lithology, this possibly indicates a weak oxidative sedimentary environment. On the basis of the ratios of Rb/K and Sr/Cu, we believe that before the salt forming period, a brackish water environment with hot climate and high evaporation existed, which provided necessary conditions for salt and potash deposition. After the salt forming period, fresh and saline water conditions alternated, characterized by three warm and humid stages and three extreme hot and drought stages. The continuous freshwater supply resulted in well-developed clasolite after the upper salt layer in the basin. |
| keywords:Simao Basin clasolite trace elements geochemical paleoenvironment |
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