松辽盆地嫩江组草莓状黄铁矿及其古环境意义  

Analysis of pyrite framboids in Nenjing Formation,Songliao Basin,and implications for the redox conditions of paleolake

作　　者：王天天[1,2] 黄永建 张之辉[1,3] 王成善 WANG Tiantian;HUANG Yongjian;ZHANG Zhihui;WANG Chengshan(State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Beijing 100083,China;Institute of Earth Sciences,China University of Geosciences,Beijing 100083,China;Schoolof Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质大学(北京)生物地质与环境地质国家重点实验室,北京100083 [2]中国地质大学(北京)科学研究院,北京100083 [3]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《山东科技大学学报（自然科学版）》2021年第5期1-9,共9页Journal of Shandong University of Science and Technology(Natural Science)

基　　金：国家自然科学基金项目(41790451,41772096)。

摘　　要：白垩纪是典型的温室气候时期,对白垩纪陆相系统古环境和古气候的研究有助于对现今升温的地球上陆相气候系统未来气候变化做出更好的预测。松辽盆地是我国大型陆相白垩纪沉积盆地,保存了近乎完整的白垩纪陆相沉积记录。晚白垩世嫩江组二段的黑色页岩是松辽盆地重要的烃源岩,并记录了湖泊缺氧事件、海侵事件和白垩纪超静磁期结束等重大地质事件。为恢复当时古湖泊水体的氧化还原状态,本研究对松辽盆地松科1井北孔嫩江组一段顶部到嫩江组二段(Santonian-Campanian期)泥岩中草莓状黄铁矿的粒径和分布进行测量、统计和研究。结果表明,嫩江组一段顶部和嫩江组二段样品中普遍存在草莓状黄铁矿,呈星散状分布。草莓状黄铁矿颗粒的粒径大小和分布统计结果表明,在嫩江组一段顶部到嫩江组二段沉积期间湖泊水体环境发生过变化。嫩江组一段顶部和嫩江组二段底部,草莓状黄铁矿的粒径大小数据指示了硫化的沉积环境,嫩江组二段中上部草莓状黄铁矿的平均粒径较大,且变化范围较大,指示了贫氧-氧化的水体环境。草莓状黄铁矿从嫩江组一段顶部开始含量增加可能与海水入侵造成的水体硫酸盐含量增加相关。Cretaceous is a period of typical greenhouse climate.The study of the Cretaceous terrestrial sedimentary records helps to better forecast how the continental ecosystems responded to climate fluctuations in the warming Earth.As a large Cretaceous continental sedimentary basin,the Songliao Basin of Northeast China preserves a near-complete Cretaceous terrestrial succession.The black shales of Member 2 of Nenjiang Formation are the dominant source rocks in Songliao Basin.Moreover,several major geologic events,such as the Lake Anoxic Event,seawater incursion event,and the termination of the Cretaceous Normal Superchron occurred during the deposition of Member 2 of Nenjiang Formation.In order to reconstruct the redox conditions of the paleolake at that time,a detailed study of the size and distribution of pyrite framboids from Member 2 to the top of Member 1 of Nenjiang Formation was conducted.The results show that the pyrite framboids widely exist and are scattered far and wide in both samples.The statistics of the grain size and distribution of the pyrite framboids indicate that great changes had taken place to the lake water environment during the period from the top of Member 1 to Member 2 of Nenjiang Formation.The grain size data of the pyrite framboids indicate the sulfuretted sedimentary environment in the interval from the top of Member 1 to Member 2 of Nenjiang Formation.In the middle to upper part of Member 2 of the Nenjiang Formation,the average grain diameters of the pyrite framboids are larger with wide ranges,suggesting dysoxic-oxic conditions.The increase of the pyrite framboids from the top of Member 1 of the Nenjiang Formation probably resulted from the extra sulfate injection due to seawater incursion event at that time.

关 键 词：草莓状黄铁矿 松辽盆地 嫩江组 氧化还原状态 古湖泊 

分 类 号：P572[天文地球—矿物学]