Abstract
The aim of the present study is to reconstruct sedimentary conditions of Middle Jurassic rocks that contain siderites to identify the mineral composition of the inserbeds and to recognize the origin of the siderite. Thin inserbeds of siderite rocks occur most frequently within Bajocian siliciclastic deposits and, more rarely, Aalenian and Bathonian. The research material comes from 11 boreholes located in the north and northeastern margins of the Holy Cross Mountains. The research methods included sedimentological analyses, and studies in polarizing and scanning electron microscopes, staining of carbonates, cathodoluminescence, X-ray structural analysis, and stable carbon and oxygen isotopic determinations were used. Middle Jurassic sideritic rocks are most often represented by clayey siderites, which also include muddy and sandy varieties and siderite sandstones. There are also local occurrences of coquinas, claystones, mudstones, and siderite conglomerates. The main component of sideritic rocks is sideroplesite. Berthierine, pistomesite, calcite, and ankerite are important components, too. The action of diagenetic processes of cementation, compaction, replacement, and alteration within the Middle Jurassic deposits was most intense during the eo- and mesodiagenesis. The sedimentological analysis showed that most of the studied siderites were formed in a low-oxygenated marine environment, mainly in the transition zone between the normal and storm wave bases and in the lower and middle shoreface zones. The results of the petrographic, mineralogical, and geochemical studies indicated the origin of the sideritic rocks mainly in the marine environment, with the participation of meteoric water. There were slight differences in the chemical composition of sideroplesite depending on the environment it crystallized in. There was no correlation between the values of the carbon isotope determinations in the sideroplesite and the environmental conditions of its crystallization. Slight differences were visible in the case of the average values of δ18O in the sideroplesite.
Highlights
Research on the Middle Jurassic siderite iron ores in the northern margin of the HolyCross Mountains was initiated by Kuźniar [1,2]
Interpretation of the sedimentary environments was made based on the vertical sequence of lithofacies in individual wells in conjunction with the interpretation of their mechanism of deposition
A correlation of environments between the boreholes was Determination of the oxygen and carbon isotopes was performed in the calcite cement of sideritic sandstone of the Wyszmontów 1 borehole
Summary
Research on the Middle Jurassic siderite iron ores in the northern margin of the Holy. Cross Mountains was initiated by Kuźniar [1,2]. His most extensive publication concerned the siderite iron ore deposit in Parczów [3], the exploitation of which started in the 1920s. The initiated siderite research was abandoned, because the production of ores appeared unprofitable. In the 1920s, research on iron deposits was carried out and continued after World War II in the Czestochowa region [4,5]. In the Łeczyca region, Kujawy and Znosko [6,7] documented an iron ore deposit composed of sideritic coquinas.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
