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铁建造和鲕铁岩是地史上两类主要的富铁沉积,不仅记录了地球大气与海洋氧化还原状态和化学条件演变,而且也反应了构造运动、岩浆活动和生物的相互作用过程.过去对铁建造已有深入研究,而有关前寒武纪铁岩成因与古海洋和构造背景研究甚少.运用扫描电镜(scanning electronic microscopy,简称SEM)、X射线衍射(X-ray diffraction,简称XRD)、能谱(energy dispersive spectroscopy,简称EDS)技术分析铁鲕的微组构、矿物成分和化学组成,讨论华北串岭沟组(1.65~1.64Ga)鲕铁岩的成因环境及其与Columbia超大陆裂解的关系.研究表明,铁鲕主要由赤铁矿和少量高岭石组成,贫陆源碎屑和Al2O3;鲕包壳由微片状赤铁矿构成的致密和疏松纹层交互组成;Fe-Al呈明显的负相关性,表明铁主要源于缺氧富铁深海水体而非陆源风化.鲕铁岩集中在快速海进和低陆源输入引起的沉积饥饿期,发育于氧化还原界面附近的潮下贫氧环境.与超大陆裂解伴生的岩浆活动、基底沉降和快速海侵是促进鲕铁岩形成的重要因素.串岭沟组底部铁岩是华北地台响应Columbia超大陆裂解而发生构造与环境转化的重要沉积记录.
Iron build-up and oolitic rock are two major types of iron-rich sediments in geo-history, which not only record the evolution of redox state and chemical conditions in the Earth’s atmosphere and ocean, but also reflect the interaction between tectonic movement, magmatic activity and living things. The research on iron construction has been studied in depth, and the research on the genesis and paleoceanic and tectonic setting of the Precambrian iron rocks is rare.Using scanning electronic microscopy (SEM) and X-ray diffraction (XRD) (EDS) technique was used to analyze the micro-structure, mineral composition and chemical composition of the iron oolites. The genesis of the oolitic rock in the northern strata (1.65 ~ 1.64Ga) and its relationship with the cracking of the Columbia supercontinent The results show that the iron oolites are mainly composed of hematite and a small amount of kaolinite, poor terrigenous detritus and Al2O3; the shell of the oolitic shell is composed of dense and undulate layers composed of microflake hematite; Fe-Al Significant negative correlation indicates that the iron is mainly derived from the anoxic and iron-rich deep sea water rather than the land-source weathering.The alluvial rocks are concentrated in the deposition-hungry period caused by rapid sea-entry and low-terrestrial input and developed at the redox interface The magmatic activity, basement subsidence and rapid sea transgression associated with the supercontinental pyrolysis are the important factors that promote the formation of the oolitic rock.The bottom irons of the Chuanlinggou Formation occur in response to the cracking of the Columbia supercontinent in the North China platform Important sedimentary records of tectonic and environmental transformations.