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Geoscience ›› 2025, Vol. 39 ›› Issue (02): 294-311.DOI: 10.19657/j.geoscience.1000-8527.2024.075

• Stratigraphy, Paleontology and Paleoenvironment • Previous Articles     Next Articles

Genesis and Environmental Response of Siliceous Rocks in the First Member of Longjiayuan Formation of Mesoproterozoic, Western Henan

LI Qianqian(), ZHENG Deshun(), SUN Fengbo, WANG Xin   

  1. School of Resources and Environment, Henan Polytechnic University, Jiaozuo, Henan 454000, China
  • Online:2025-04-10 Published:2025-05-08
  • Contact: ZHENG Deshun

Abstract:

Siliceous rocks in different geological periods have complex genesis, and their sources of silica are influenced by various factors such as microorganisms, terrestrial debris, seawater conditions, and hydrothermal fluids.Siliceous rocks serve as important indicators of sedimentary environments at different stages of tectonic evolution.The concentration of dissolved form of silicic acid is high in the Precambrian ocean, but the silica source of the siliceous rocks and the formation process of siliceous sediments in the southern margin of the North China Craton have not been extensively studied.The siliceous rocks of the first member of the Longjiayuan Formation in the Mesoproterozoic Guandaokou Formation in Western Henan are of various types and show continuous development.Based on their petrological characteristics and combined with analyses of major and trace elements, the silica sources, formation processes, and mechanisms of the Longjiayuan siliceous rocks were studied.The results show that the Longjiayuan siliceous rocks are uniformly distributed in the section and can be classified into bedding-banded, deformed stratified, nodule-massive, and chrysanthemum-like forms.Geochemical analyses including discriminant diagrams of Al/(Al+Fe+Mn) values as well as Ce/Ce* and Eu/Eu* values suggest two sources of silica components: hydrothermal and dissolved silica from seawater.The formation process of the siliceous rocks can be divided into three stages: sedimentary, early diagenetic, and diagenetic stages.During the sedimentary stage, silica components in seawater are mainly deposited in the form of siliceous colloids.During the early diagenetic stage, unconsolidated siliceous sediments aggregate in low-lying areas under the influence of gravity, forming some storm-induced siliceous rocks under the action of external forces such as storms.During the diagenetic stage, siliceous sediments are gradually consolidated under the pressure of diagenesis, forming layered siliceous rocks in gently sloping areas and massive siliceous rocks in low-lying areas.The siliceous rocks of the first member of the Longjiayuan Formation record the Mesoproterozoic sedimentary environment of the southern North China Craton, indicating a stable, open shallow marine setting in western Henan, conducive to silica enrichment and preservation.

Key words: siliceous rock, siliceous source, siliceous rock genesis, Western Henan, Mesoproterozoic

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