The alkaline lake source rocks of the Fengcheng Formation are developed in the Mahu Sag of the Junggar Basin. Different from traditional continental fresh water and saltwater lake source rocks, alkaline lake source rocks lack targeted evaluation criteria, and it is unknown whether their hydrocarbon generation models are consistent with traditional models. Therefore, in the present study, evaluation standards and hydrocarbon generation models of alkaline lake source rocks are discussed based on geological and organic geochemical data and a systematic summary of the geochemical characteristics of the Fengcheng Formation source rocks. The Fengcheng Formation source rocks are mainly diamictite with mixed argillaceous rock and dolomite; most total organic carbon (TOC) values range from 0.2–1.4%; and the kerogen is primarily oil-prone type II, reaching low- to high-maturity stages. Based on the types of organic matter in source rocks and the relationships between organic matter abundance parameters, the evaluation standard of alkaline lake source rocks is proposed. The Fengcheng Formation is mainly composed of good to excellent source rocks (55.5%) with high hydrocarbon generation potential. The single-peak hydrocarbon generation model of the Fengcheng Formation is similar to that of traditional freshwater or saltwater lakes, with a high hydrocarbon generation rate, two to five times that of the traditional model; its main particularity is in the formation of naphthenic crude oil from the kerogen of bacteria and algae. A new understanding of the hydrocarbon generation potential and model of alkaline lake source rocks in the Fengcheng Formation can provide support for tight oil and shale oil exploration in the Mahu Sag.

中文翻译：

---

二叠系碱性湖泊烃源岩评价及生烃模式——以准噶尔盆地玛湖凹陷凤城组为例

准噶尔盆地玛湖凹陷凤城组碱性湖烃源岩发育。与传统的陆相淡水和咸水湖烃源岩不同，碱性湖烃源岩缺乏针对性评价标准，其生烃模型与传统模型是否一致尚不清楚。因此，本研究基于地质和有机地球化学资料，系统总结凤城组烃源岩地球化学特征，探讨碱性湖源岩评价标准和生烃模式。凤城组烃源岩以混积岩为主，混有泥质岩和白云岩；大多数总有机碳 (TOC) 值范围为 0.2–1.4%；干酪根主要是油性 II 型，达到低成熟阶段。根据烃源岩有机质类型及有机质丰度参数之间的关系，提出碱性湖源岩评价标准。凤城组主要为优质至优良烃源岩（55.5%），生烃潜力高。凤城组单峰生烃模式与传统淡水湖或咸水湖相似，生烃率高，是传统模式的2～5倍；它的主要特点是由细菌和藻类的干酪根形成环烷原油。