Geochemistry of stream sediment from the state of Colorado using NURE data

Naser Yousif, University of Texas at El Paso

Abstract

The present study used univariate, bivariate, and multivariate statistics together with GIS techniques to investigated the possible abnormal geochemical patterns, or geochemical anomalies in a geochemical data set for Colorado. The elements used on this analyses included twenty four elements are selected which are Al, Ba, Ca, Ce, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Na, Nb, Ni, Pb, Sc, Sr, Th, Ti, U, V, and Zn. The study found that the high positive kurtoses show that very high values in the data are rare, may be associated with rare processes such as mineralization. For example Al, Na and K have fairly small kurtoses, showing that these values are more evenly distributed within the data ranges. The spatial distribution of the elements is presented in the forms of five types of maps those were (1) point map of raw data, (2) IDW grid map of the raw data, (3) geologic polygons of the raw data, (4) hydrologic polygons of the raw data, and (5) point map of the outlier values. The geochemistry of the studied element was controlled by the bed rock chemistry with minor anthropogenic sources. The identified physiographic provinces include: (1) Great Plains, (2) Rio Grande rift system, (3) Rocky Mountains, (4) Colorado Plateau, and (5) Pioance Basin; their impacts on metal distribution were assessed.^ The main factors affecting the distribution and associations of the investigated metals are: (a) Factor (1) accounts for 22% of the total variance, and contains a high loading of Al, Co, Cr, Cu, Fe, Mg, Mn, Ni, Sc, Ti, and V, and subdivided into subfamilies, such as the mafic trace elements with the presence of Co, Cr, Fe, Sc, Ni, and V, ultramafic rocks with the presence of Cr, Co, Ni, and Cu, mafic rocks with the presence of Ti, V, and Sc, laterites with the presence of Ni, Cr, and V, (b) Factor (2) accounts for 12% of the total variance, and contains a high loading of Ba, Na, and Ti. These elements have high concentrations in felsic igneous rocks, and they may stay in resistate minerals in sediments, (c) Factor (3) accounts for 10% of the total variance, and contains a high loading of (Ce, La and U), (Ca and Mg). This group suggests the rare earth element pegmatite type composition with the presence of Ce, La, and U, and carbonate elements with the presence of Ca and Mg, but the Mg and Ca have negative scores. Ca and Mg association is related to naturally occurring carbonate signatures, commonly found in limestones (CaCO3) and dolomites (Ca/Mg) CO3, (d) Factor (4) accounts for 8% of the total variance, and contains a high loading of K and Li. These two elements are the alkali metals in the first group of the periodic table, and (e) Factor (5) accounts for 6% of the total variance, and contains a high loading of Pb with a value of 0.93.^ The study found that minerals in the lithological units of CMB has incompatible elements (i.e., K, Rb, Sr, Ba, Zr, Th, Rb, Sr, Nd and other rare earth elements that do not easily fit into the crystal lattice structures of mantle minerals such as olivine, pyroxene, spinel, and garnet. Thus weathering product is expected to be depleted in these elements. The study also reported several applications of the investigated dataset and recommended further studies. ^

Subject Area

Geology|Statistics|Geochemistry

Recommended Citation

Yousif, Naser, "Geochemistry of stream sediment from the state of Colorado using NURE data" (2007). ETD Collection for University of Texas, El Paso. AAI3273991.
http://digitalcommons.utep.edu/dissertations/AAI3273991

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