Zoning (geology)

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Sketch of the operating principle in zoning using the example of a corridor storage facility (after)

When zoning (also: zonality ) is, one in the geology , the mineralogy and economic geology used term. In a broader sense, zoning refers to the spatial distribution of postmagmatic mineral paragenesis . A zoning exists when ore deposit at a magmatogenen ( transition -, or Imprägnations- Skarnlagerstätte ) more or less concentric, centering on the erzspendenden igneous body zones same Erzmineralgehaltes are present. The individual ore parageneses form a vertical sequence. These zones are a reflection of the geothermal conditions prevailing at the time of ore formation and were areas of previously equal temperatures. They allow the reconstruction of geo-isotherms and conclusions about the location of the ore-producing magma body, provided that it is not part of the deposit itself. Zoning can affect the deposit to varying degrees. The following subdivision is made here (with example deposits):

  • "Regional Zoning ": Zoning on a small scale (Southern Piedmont, USA [Au], ore deposits of the Cordillera Belt)
  • " District Zoning ": Zoning in an enclosed area of ​​the deposit or deposit. Common form in the world-famous ore deposits ( Butte , Montana , USA [Cu]; Cornwall , England [Sn]; Tonopah , Nevada , USA [Ag])
  • " Orebody Zoning ": Zoning over the entire deposit area including the minor mineralization (most " Massive Sulphide " deposits ; "Kuroko Bodies", Japan; Red Mountain , Colorado , USA [Pb, Ag]; Kongsberg , Norway [Ag]).

Based on this, LIPP differentiates between polyascendent and monoascendent zonality for the German-speaking research area, based on research results from KUTINA and on the basis of systematic investigations in the area of ​​the Schneeberg deposit area :

  • Polyascending zonality : spatially separated occurrence of individual vein formations in a deposit area
  • monoascendent zonality : spatial separation of the sequences or the mineralizations within a duct formation

If the geo-isotherms, such as in the case of near-surface intrusions, are very close to one another (or in one another), the term "telescoping" is used instead.

In some sources the term is also used for non-metallic deposits such as kaolin and coal deposits. However, the zonality does not exclusively refer to the chemical composition of the useful components. With kaolin , vertical color changes and with coal deposits different degrees of metamorphosis (both horizontal and vertical) are described with zoning or zonality.

literature

Individual evidence

  1. ↑ a b L. Baumann, IL Nikolskij, M. Wolf: Introduction to geology and exploration of deposits. VEB German publishing house for basic industry, 1979, DNB 800371623 .
  2. ^ JM Guilbert, FP Charles Jr.: The Geology of Ore Deposits. WH Freemann and Company, New York 1986, ISBN 0-7167-1456-6 .
  3. ↑ U. Lipp (with additions from S. Flach): Bismuth, cobalt, nickel and silver ores in the northern part of the Schneeberg deposit district. Mining monograph. Saxon State Office for Environment, Geology and Agriculture, Sächsisches Oberbergamt, Freiberg 2003, DNB 96891585X .
  4. ↑ J. Kutina: A contribution to the classification of zoning in ore veins. In: Geological. Volume 3, Universitas Carolina, 1957, pp. 197-225.
  5. ↑ J. Kutina: The concept of monoascendent and polyascendent zoning, Symp. Problem. postmagm. ore deposits. II, Praha 1965, pp. 47-55.