3. Calibration of an X-ray Diffraction Method to Determine Relative Mineral Abundances in Bulk Powders Using Matrix Singular Value Decomposition: a Test from the Barbados Accretionary Complex

X-ray diffraction methods are used routinely to identify detrital and authigenic minerals in bulk powders of marine sediment. Semiquantitative bulk XRD analysis, however, is difficult. We employed a mathematical technique using matrix singular value decomposition to solve for reliable normalization factors, thereby allowing accurate conversion of XRD data to relative mineral abundances. Calibration was achieved through measurements of laboratory mixtures with known abundances of mineral standards. Error analysis demonstrates that this method is superior to other common shipboard procedures used by the Ocean Drilling Program; the errors from known standards fall within the range of analytical reproducibility and are better than 3%.