Earth Science Frontiers ›› 2012, Vol. 19 ›› Issue (3): 7-18.

• Article • Previous Articles     Next Articles

Global Geochemical Baselines: Understanding the past and predicting the future.

WANG  Xue-Qiu   

  1. Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang 065000, China
  • Received:2012-03-12 Revised:2012-04-26 Online:2012-05-25 Published:2012-05-25


In  order to recognize  the evolution of the Earth and global changes,  it is necessary to set up  consistent Globalscale Geochemical Baselines as a reference. “Geochemical Baseline” is known as the database and the accompanying  element distribution maps by systematically documenting the concentration and spatial distribution of chemical elements and compounds  on the Earths surface, which can be applied to quantified  the  future humaninduced or natural changes in the chemistry of the present Earth and the past chemical evolution induced by geological processes. China Geochemical Baselines (CGB), as a part of  the Global Geochemical Baselines, is to document both concentrations and spatial distribution of nearlyall chemical elements across  whole China. China Geochemical Baseline Networks  are  designed based on 1∶200000 map sheets of 1°(lng.)×40′ (lat.), approximately 1500 grids covering all over China. Approximately 10000 rock samples for primary lithosphere baselines and 6000 soil samples for secondary pedosphere had been collected across the China land surface. Eightyone geochemical indicators including 78 chemical elements are determined by ICPMS/AES following 4acid digestion and by XRF following fusion as backbone methods combined with other 10 analytical methods. Analytical quality is under strict control by using standard reference samples to obtain harmonious highquality data. In the present paper the author shows  some of the examples for the  use of preliminary results of the spatial distribution of elements to understand the past and to predict the future. Ir geochemical anomalies have been discovered in the suspected Cretaceous and Tertiary (KT) boundary ranging from 0.2×10-9 to 0.8×10-9 whereas Ir concentration baselines in Cretaceous and Tertiary rocks are less than 0.02×10-9. It is likely that the Iridium in the suspected boundary is of extraterrestrial origin, providing us with understanding  the extinction of dinosaurs due to the impact of an earthcrossing asteroid. It has been found that  the dramatic changes of CaO distribution occurred in the past 15 years from 1994 to 2009. The average concentration decreases from 0.53% to 0.41%, the  area of CaO<1% extends from 872000 km2 to 1073000 km2, increased 23%  as compared to that in 1994, due to the leaching of CaCO3 by acid rains caused by human activities.

Key words:  , Geochemical Baselines; lithosphere; pedosphere; past evolutions; future changes

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