辽宁清原地区小莱河条带状铁建造和围岩 地球化学特征及其地质意义.

Earlier Cambrian banded iron construction (BIF) type iron ore is the most important source of iron in China, accounting for more than 60% of the country's iron reserves, of which the BiF type iron ore in the late Neo-Archean period in North China is the most typical. Detailed petrology, geochemistry and isotopic studies were carried out on the Bif and surrounding rocks of the Xiaolai River in the Qingyuan region of Liaoning Province, northeast of Craton, North China, aiming to provide constraints on the source area and tectonic environment. Xiaolaihe BIF is mainly composed of magnetite, quartz and silicates (such as iron perilla pyroxene, etc.), and the SiO and all-iron (FeO) content of the samples varies widely. The AlO content (mass fraction, the same below) in a small number of Xiaolai River BIF samples was higher (>1%), indicating the presence of an input of land-based clastic material during the sedimentation process. The BIF samples, which were not contaminated with clastic substances, showed typical seawater characteristics, including low alO, high field strength elements and transition metal elements, relative loss of light rare earth elements, and enrichment of heavy rare earth elements and Eu positive anomalies. The simulation results showed that the sample matched the PAAS standardized rare earth element dispensing pattern of the seabed high temperature hydrothermal and seawater 1:100 mixed solution, indicating that the hydrothermal activity on the seabed provided heat and substances to the BIF. The mineralization of the Bif of the Xiaolai River comes from the base-super-bedrock rock at the bottom of the Qingyuan greenstone belt leached with high temperature hydrothermal fluid. The surrounding rocks of the Xiaolai River BIF are mainly metamorphic volcanic rocks of the Stone Shed Subgroup and a small amount of metamorphic clastic sedimentary rocks. The geochemical characteristics of clastic sedimentary rocks are controlled by the composition of complex source regions with medium-low degree of weathering under the island arc system (such as Aochang granite, Yingyun diorite and a small amount of bedrock), which is similar to the source area of the Xiaolai River BIF. Based on the geological, geochemical, isotopic, chronological and other characteristics of the deposit, it is believed that the Xiaolai River BIF system was formed in the Post-Arc Basin of the Algoma-type BIF [ABSTRACT FROM AUTHOR]