Advances in Earth Science ›› 2006, Vol. 21 ›› Issue (8): 857-862. doi: 10.11867/j.issn.1001-8166.2006.08.0857

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Dolomite Problem and Precambrian Enigma

Wang Yong   

  1. Northwest University, Xi′an 710069, China
  • Received:2005-10-26 Revised:2006-07-24 Online:2006-08-15 Published:2006-08-15

Wang Yong. Dolomite Problem and Precambrian Enigma[J]. Advances in Earth Science, 2006, 21(8): 857-862.

The origin of dolomites is a research topic attracting great attention in sedimentology. Many dolomitization models have been invoked to interpret the origination of virious diagenetic dolomites. However, the genesis of early-formed dolomites has long been an enigma in sedimentology, often referred to as the "Dolomite Problem". This problem arises from the fact that scientists have not yet been successful in the laboratory in precipitating perfectly ordered dolomite at the normal temperatures and pressure that occur at Earth's surface. The recent field and laboratory experiments show that some microbes play important roles in precipitation of dolomite under conditions of Earth's surface. For example, the direct mediation of sulfate-reducers and methanogens can overcome the kinetic barrier to dolomite nucleation, and that they may play an active role in the formation of this mineral in natural environments. In these anaerobes involved system, neither extremely Mg-rich fluids nor highly supersaturated conditions are required for the nucleation and precipitation of dolomite. This integrating microbiology into the carbonate sedimentology opens a new research direction and also throws a new light on the “Dolomite Problem”. Mimetic dolomization, where the precursor fabrics are excellently preserved, has important implications on interpreting the genesis of dolostone with original fabrics preserved. The “Precambrian enigma” refers to the scarcity of calcified cyanobacteria in Precambrian stromatolites. There have been subsequent changes in the composition stromatolite biota through Earth's history. Smaller eubacteria may have greater involvement than cyanobacteria in stromatolite formation in the Precambrian, and cyanobacteria may enter stromatolite building biota until the latest Neoproterozoic.

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