ABSTRACT: Recognition in Typomorphic Geochemical Associations and Their Mapping in Bottom Formation of the World Ocean
Alexandr I. Ainemer, Boris C. Vanstein
By Clark-Vernadsky's law on the common occurrence of chemical elements in rocks and sediments, their occurrence is governed by the predominance of some elements (or their groups) over the others. This fact is taken into account by the compilation of geochemical maps where geochemically distinct rocks are inferred only from high (relative or absolute) contents of various elements. At the same time, the internal characteristics of rocks and minerals are governed by bond strengths of chemical elements and their degree co-variability. The idea of a geochemical association presupposing the presence of element groups whose concentrations in rocks are process dependent is used as a basis for the association of chemical elements. Our model uses a linear paragenesis, i.e., a posit ve linear correlation relationship. Factor analysis is the best method for recognition of associations and their role in the formation of sedimentary rocks. The obtained factor associations are interpreted with allowance made for element bond stability, different sedimentation environments, and physiochemical conditions. Similar factor associations allow distinction of typomorphic parageneses, while calculated factor values help to map the associations. The predominance of a typomorphic association relevant to the major factor in a plot is shown by different colors on the maps of geochemical associations. Sharp transitions from positive to negative factor values and boundaries of different factors reflect changes in physiochemical sedimentation environments and may be interpreted as geoc emical barriers. In interpreting these maps, all the available geological data should be used (sediment distribution, topography, tectonic structures, etc.). The proposed method for distinguishing and mapping typomorphic geochemical associations was used by the compilation of multielement geochemical maps of Fe-Mn nodules and enclosing sediments of the Pacific. Their interpretation allows us to recognize major composition variations of Fe-Mn nodules and to establish zones of the most intense chemical element redistribution related to global and local inhomogeneities of the ocean, including tectonic, climatic, and hydrodynamic differences.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990