Interpretation of Na-Cl-Br systematics in sedimentary basin brines; comparison of concentration, element ratio, and isometric log-ratio approaches

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doi: 10.1007/s11004-012-9436-z
Authors:Engle, Mark A.; Rowan, Elisabeth L.
Author Affiliations:Primary:
U. S. Geological Survey, Reston, VA, United States
Volume Title:Mathematical Geosciences
Source:Mathematical Geosciences, 45(1), p.87-101. Publisher: Springer, Dordrecht, Netherlands. ISSN: 1874-8961
Publication Date:2013
Note:In English. 32 refs.; illus., incl. 2 tables
Summary:Mathematicians and geochemists have long realized that compositional data intrinsically exhibit a structure prone to spurious and induced correlations. This paper demonstrates, using the Na-Cl-Br system, that these mathematical problems are exacerbated in the study of sedimentary basin brines by such processes as the evaporation or dissolution of salts owing to their high salinities. Using two published datasets of Na-Cl-Br data for fluids from the Appalachian Basin, it is shown that log concentration and Na/Br versus Cl/Br methods for displaying solute chemistry may lead to misinterpretation of mixing trends between meteoric waters (for example shallow drinking water aquifers) and basinal brines, partially due to spurious mathematical relationships. An alternative approach, based on the isometric log-ratio transformation of molar concentration data, is developed and presented as an alternative method, free from potential numerical problems of the traditional methods. The utility, intuitiveness, and potential for mathematical problems of the three methods are compared and contrasted. Because the Na-Cl-Br system is a useful tool for sourcing solutes and investigating the evolution of basinal brines, results from this research may impact such critical topics as evaluating sources of brine contamination in the environment (possibly related to oil and gas production), evaluating the behavior of fluids in the reservoir during hydraulic fracturing, and tracking movement of fluids as a result of geologic CO2 sequestration. Copyright 2012 International Association for Mathematical Geosciences
Subjects:Alkali metals; Basins; Brines; Bromine; Calcite; Carbonates; Carboniferous; Chemical composition; Chemical ratios; Chlorides; Chlorine; Clastic rocks; Concentration; Connate waters; Data processing; Fluid phase; Graphic display; Ground water; Gypsum; Halides; Halite; Halogens; Hydrochemistry; Interpretation; Lower Pennsylvanian; Mathematical methods; Metals; Meteoric water; Mixing; Paleozoic; Pennsylvanian; Pottsville Group; Quantitative analysis; Salinity; Sandstone; Sea water; Sedimentary basins; Sedimentary rocks; Sodium; Solute transport; Solutes; Statistical analysis; Sulfates; Transport; Appalachian Basin; North America; Oak Ridge National Laboratory; Tennessee; United States; West Virginia; Cl/Br; Eastern Tennessee; Log-ratio; Na/Br
Coordinates:N355200 N360200 W0841000 W0842500
Record ID:2013019870
Copyright Information:GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data supplied by Springer Verlag, Berlin, Federal Republic of Germany
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