安徽巢湖凤凰山栖霞组臭灰岩段黄铁矿结核的地球化学  

Geochemistry of nodular pyrites occurred in the odorous limestone of the Early Permian Qixia Formation from Fenghuang Hill of Chaohu City,Anhui Province

作　　者：陈健[1,2,3] 李洋 齐啸威[1,2,3] 李秀丽 王嘉怡 张鑫迪 冯敏 谢婉秋 CHEN Jian;LI Yang;QI Xiaowei;LI Xiuli;WANG Jiayi;ZHANG Xindi;FENG Min;XIE Wanqiu(School of Earth and Environment,Anhui University of Science and Technology,Huainan,Anhui 232001,China;Key Laboratory of Mine Geological Disaster Prevention and Environment Protection of Anhui Higher Education Institutes,Huainan,Anhui 232001,China;National Key Laboratory of Deep Coal Safety Mining and Environmental Protection,Huainan,Anhui 232001,China)

机构地区：[1]安徽理工大学地球与环境学院,安徽淮南232001 [2]矿山地质灾害防治安徽省高校重点实验室,安徽淮南232001 [3]深部煤炭安全开采与环境保护全国重点实验室,安徽淮南232001

出　　处：《地质学报》2024年第8期2486-2498,共13页Acta Geologica Sinica

基　　金：国家自然科学基金面上项目(编号42372189);矿山地质灾害防治安徽省高校重点实验室开放基金(编号2022-MGDP-05);安徽省杰出青年科学基金项目(编号1908085J14)联合资助的成果。

摘　　要：沉积黄铁矿的地球化学是认识重金属汇、矿床金属来源、古海洋化学及环境条件的重要途径。巢湖北郊凤凰山上石炭统黄龙组至下二叠统栖霞组臭灰岩段揭露良好,臭灰岩中黄铁矿结核普遍,集中产出于碳质页岩上2~3 m的沥青质灰岩中,其地球化学特征及成因不清。为查明黄铁矿结核的地球化学特征,分析臭灰岩段的沉积环境,推断早二叠世早期古环境演化,厘清碎屑岩段与臭灰岩的关系,从该剖面采集10个黄铁矿结核和灰岩样品,采用偏光显微镜、X射线荧光光谱仪和电感耦合等离子体质谱仪分析测试其矿物成分和主微量元素组成。结果表明:凤凰山下二叠统栖霞组臭灰岩段下部普遍发育的黄铁矿结核呈块状和微晶粒状,与灰岩界线清晰,并未切割或破坏有机质纹层,为成岩孔隙水交代生物而成。臭灰岩中SO_(3)和Fe_(2)O_(3)显著富集,分别与高含量有机质和与下伏碎屑岩段一致的陆源供应有关。与上陆壳相比,臭灰岩中Se、Mo和Cd富集,黄铁矿结核中Cr、Ni、As、Se、Mo、Cd、Sb和Hg富集。碎屑岩-臭灰岩的岩性组合、黄铁矿结核的分布范围及其主微量元素地球化学特征均表明臭灰岩和黄铁矿结核沉积于受部分陆源物质影响的稳定大陆边缘缺氧强还原海相环境。The geochemistry of sedimentary pyrite provides valuable insights into heavy metal sinks,sources of metals for ore deposits,and the chemistry and environmental conditions of ancient oceans.The Pennsylvanian Huanglong Formation and the Lower Permian Qixia Formation are well-exposed in Fenghuang Hill,northern Chaohu City,Anhui Province.Pyrite nodules are commonly found within the odorous limestone of the lower member of the Qixia Formation,particularly in the 2~3 meter thick bituminous limestone layer overlying the carbonaceous shale member.Despite their prevalence,the geochemistry and genesis of these pyrite nodules are still not reported.This study investigates the geochemical characteristics of pyrite nodules,the depositional environment of the odorous limestone,the paleoenvironmental evolution during the Early Permian,and the relationship between the underlying clastic rocks and the odorous limestone.Ten pyrite nodule and limestone samples were collected for analysis.Mineral identification was performed using polarizing microscopy,while major element oxides and trace element concentrations were determined using X-ray fluorescence spectrometry and inductively coupled plasma-mass spectrometry,respectively.Results indicate that the pyrite nodules,widely distributed in the lower Qixia Formation odorous limestone,mainly occur as massive or microcrystalline grains with a distinct boundary between the nodules and the host limestone.The pyrite nodules do not cut or disrupt the surrounding organic-rich laminae,suggesting that it was precipitated from the diagenetic porewater via organisms replacement.The odorous limestone samples exhibit significant enrichment in SO_(3)and Fe_(2)O_(3),likely related to the high organic matter content and a similar terrestrial input as the underlying clastic rock member,respectively.Compared to the upper continental crust,the Chaohu odorous limestone samples are enriched in Se,Mo,and Cd,while the pyrite nodule samples show elevated concentrations of Cr,Ni,As,Se,Mo,Cd,Sb,and Hg.The lithol

关 键 词：微量元素 稀土元素 黄铁矿结核 栖霞组 臭灰岩 巢湖 

分 类 号：P595[天文地球—地球化学] P578.292[天文地球—地质学]