Hematite concretions form by precipitation of iron oxide from iron-rich solutions. Hematite nodules are often formed in sedimentary rocks like limestone by oxidation of pyrite or marcasite (iron sulfide) crystals.

2011年1月1日 · Iron oxide concretions form in porous sandstone by chemical reduction and solution of iron minerals, transport of Fe 2+ in solution, and precipitation of hydrous ferric oxide by oxidation.

The concretions were created by the precipitation of iron, which was dissolved in groundwater. The iron was originally present as a thin film of iron oxide surrounding sand grains in the Navajo Sandstone. Groundwater containing methane or petroleum from underlying rock beds reacted with the iron oxide, converting it to soluble reduced iron.

2015年9月12日 · As the iron precipitated, it acted as a glue or cement to bind sandstone into round concretions. Some are small, dense and dark, ranging in size from peas to baseballs, and are colloquially referred to as hematite or iron nodules, iron sandstone balls and Moki marbles.

2015年6月30日 · The proposed Ostwald ripening mechanism is consistent with iron isotopic measurements from Navajo Sandstone, which indicate that iron oxide nodules formed through simple mineral dissolution...

2013年5月1日 · Iron-oxide coloration and deposits in sandstone are significant indicators of the mobility of solutes (Fe 2+ and O 2) in groundwater, mainly controlled by host-rock porosity and permeability.

Widespread iron oxide precipitation from groundwater in fine-grained red beds displays various patterns, including nodulation, banding and scallops and fingers. Hematite nodules have been...

For example, it was the distribution of rinded, iron oxide-cemented concretions in the Navajo Sandstone that allowed Loope et al. (2010) to delineate the pathways of late-diage-netic, CO2-enriched and CH4-enriched fluids through porous and permeable strata and to reconstruct the timing of subsequent pore-water oxygenation.

2016年5月23日 · In this study, concretions in the Oligocene sandstones, which cover a wide range of exposure in the Denizli Basin, have been examined. The sandstones are consisted predominantly of quartz,...

2021年2月26日 · Iron oxide concretions occur in the Dhandraul Sandstone of Manikpur Formation, Kaimur Group, Vindhyan Supergroup (figure 1). Its formation history involves varying sedimentary environments including fluvial, aeolian, and nearshore (Chakraborty 1996).