Three independent errors affect X-ray diffraction estimates of dolomite in pre-Cenozoic carbonates. When using calcite/dolomite [104] peak ratios, each 1% of excess calcium in the dolomite lattice causes approximately a 2% overestimate of the amount of dolomite. Use of the [113] peak ratios avoids the stoichiometry problem; however. if quartz is present, the interference between the [102] quartz peak ( d = 2.282 A) and the [113] calcite peak ( d = 2.285 A) can cause a serious underestimate of the dolomite proportion. In addition, error will occur if the crystallite size in the powdered standards used to prepare X-ray calibration curves differs significantly from the crystallite size in the sample unknowns. All these errors can be avoided or corrected; however, point count or visual estimation of stained thin sections is a simple, reliable technique and is preferable for routine analysis of visibly crystalline, lithified, sediment.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.