Silicification

Silicified fossil shells

In geology, silicification is a petrification process in which silica-rich fluids seep into the voids of Earth materials, e.g., rocks, wood, bones, shells, and replace the original materials with silica (SiO2). Silica is a naturally existing and abundant compound found in organic and inorganic materials, including Earth's crust and mantle. There are a variety of silicification mechanisms. In silicification of wood, silica permeates into and occupies cracks and voids in wood such as vessels and cell walls.[1] The original organic matter is retained throughout the process and will gradually decay through time.[2] In the silicification of carbonates, silica replaces carbonates by the same volume.[3] Replacement is accomplished through the dissolution of original rock minerals and the precipitation of silica. This leads to a removal of original materials out of the system.[3][4] Depending on the structures and composition of the original rock, silica might replace only specific mineral components of the rock. Silicic acid (H4SiO4) in the silica-enriched fluids forms lenticular, nodular, fibrous, or aggregated quartz, opal, or chalcedony that grows within the rock.[5] Silicification happens when rocks or organic materials are in contact with silica-rich surface water, buried under sediments and susceptible to groundwater flow, or buried under volcanic ashes. Silicification is often associated with hydrothermal processes.[1] Temperature for silicification ranges in various conditions: in burial or surface water conditions, temperature for silicification can be around 25°−50°; whereas temperatures for siliceous fluid inclusions can be up to 150°−190°.[6][7] Silicification could occur during a syn-depositional or a post-depositional stage, commonly along layers marking changes in sedimentation such as unconformities or bedding planes.[5][8]

  1. ^ a b Akahane, Hisatada; Furuno, Takeshi; Miyajima, Hiroshi; Yoshikawa, Toshiyuki; Yamamoto, Shigeru (July 2004). "Rapid wood silicification in hot spring water: an explanation of silicification of wood during the Earth's history". Sedimentary Geology. 169 (3–4): 219–228. Bibcode:2004SedG..169..219A. doi:10.1016/j.sedgeo.2004.06.003. ISSN 0037-0738.
  2. ^ Sigleo, Anne C. (September 1978). "Organic geochemistry of silicified wood, Petrified Forest National Park, Arizona". Geochimica et Cosmochimica Acta. 42 (9): 1397–1405. Bibcode:1978GeCoA..42.1397S. doi:10.1016/0016-7037(78)90045-5. ISSN 0016-7037.
  3. ^ a b Götz, Annette E.; Montenari, Michael; Costin, Gelu (2017). "Silicification and organic matter preservation in the Anisian Muschelkalk: implications for the basin dynamics of the central European Muschelkalk Sea". Central European Geology. 60 (1): 35–52. Bibcode:2017CEJGl..60...35G. doi:10.1556/24.60.2017.002. ISSN 1789-3348.
  4. ^ Liesegang, Moritz; Milke, Ralf; Kranz, Christine; Neusser, Gregor (2017-11-06). "Silica nanoparticle aggregation in calcite replacement reactions". Scientific Reports. 7 (1): 14550. Bibcode:2017NatSR...714550L. doi:10.1038/s41598-017-06458-8. ISSN 2045-2322. PMC 5673956. PMID 29109392.
  5. ^ a b S.K. Haldar and Josip Tišljar (2014). Introduction to Mineralogy and Petrology. Elsevier. p. 198. ISBN 978-0-12-408133-8.
  6. ^ Klein, Robert T.; Walter, Lynn M. (September 1995). "Interactions between dissolved silica and carbonate minerals: An experimental study at 25–50°C". Chemical Geology. 125 (1–2): 29–43. Bibcode:1995ChGeo.125...29K. doi:10.1016/0009-2541(95)00080-6. ISSN 0009-2541.
  7. ^ You, Donghua; Han, Jun; Hu, Wenxuan; Qian, Yixiong; Chen, Qianglu; Xi, Binbin; Ma, Hongqiang (2018-02-19). "Characteristics and formation mechanisms of silicified carbonate reservoirs in well SN4 of the Tarim Basin". Energy Exploration & Exploitation. 36 (4): 820–849. doi:10.1177/0144598718757515. ISSN 0144-5987. S2CID 135282628.
  8. ^ Sugitani, Kenichiro; Yamashita, Fumiaki; Nagaoka, Tsutomu; Yamamoto, Koshi; Minami, Masayo; Mimura, Koichi; Suzuki, Kazuhiro (June 2006). "Geochemistry and sedimentary petrology of Archean clastic sedimentary rocks at Mt. Goldsworthy, Pilbara Craton, Western Australia: Evidence for the early evolution of continental crust and hydrothermal alteration". Precambrian Research. 147 (1–2): 124–147. Bibcode:2006PreR..147..124S. doi:10.1016/j.precamres.2006.02.006. ISSN 0301-9268.