Simulation of iron mineral diagenesis in ancient iron formations by P/T-treatment of biogenic and abiogenic iron minerals

前寒武纪带状铁组（BIFs）是由二氧化硅和铁矿物组成的古老沉积矿床。最古老的BIFs （bbbb3 Gyr）的沉积是由蓝藻氧（O2）对溶解铁（II）的化学氧化导致非生物源铁（III）矿物的形成，还是最古老的铁地层是无氧光养铁（II）氧化细菌（导致生物源铁（III）矿物）的直接产物，这是一个激烈的争论。区分这两种过程的一种可能方法是研究铁（III）矿物在地质时期的转化，因为与非生物成因的铁（III）矿物相比，生物成因的铁（III）矿物与微生物细胞直接相关。该项目的目的是研究生物成因和非生物成因铁矿物的成岩过程，并确定生物成因和非生物成因铁矿物的成岩矿物特征。为此，我们打算将由光养性铁（II）氧化剂产生的铁矿物和细胞-铁矿物聚集体暴露于bif所经历的温度和压力下，并将其与矿物鉴定、铁同位素和有机生物标志物分析相结合。该研究将有助于限制生物流化床沉积过程，并将提高我们对现代环境中铁生物地球化学的认识。

Precambrian Banded Iron Formations (BIFs) are ancient sedimentary deposits consisting of silica and iron minerals. It is heavily debated whether the deposition of the oldest BIFs (>3 Gyr) are a result of chemical oxidation of dissolved iron(II) by cyanobacterial oxygen (O2) leading to the formation of abiogenic iron(III) minerals or whether the oldest iron formations are a direct product of anoxygenic phototrophic Fe(II)-oxidizing bacteria (leading to biogenic iron(III) minerals). A possible approach to distinguish these two processes is to study the transformation of iron(III) minerals over geological time, since in contrast to abiogenic iron(III) minerals, biogenic iron(III) minerals are directly associated with microbial cells. The goal of this project is to study diagenetic processes of biogenic and abiogenic iron minerals and to identify features in the diagenetic mineral products indicative for either biogenic or abiogenic iron minerals. To this end we intend to expose iron minerals and cell-iron-mineral aggregates produced by phototrophic Fe(II)-oxidizers to temperatures and pressures experienced by BIFs and couple this to mineral identification, Fe-isotope and organic biomarker analysis. This study will help to constrain the processes with regard to BIF deposition and will improve our understanding of iron biogeochemistry in modern environments.