Application of total-reflection X-ray fluorescence (TXRF) to study authigenic carbonates in planktonic foraminifera

Abstract

In this study we present results showing the elemental composition of diagenetic coatings on foraminiferal tests by total-reflection X-ray fluorescence (TXRF) within N. pachyderma diagenetic shells from the Holocene sediments in the Okhotsk Sea. The method includes direct deposition of individual foraminifera of micro-size on the quartz carrier and digestion by 2 N nitric acid on it. The investigation of the specimen prepared shows its suitability for TXRF analysis based on its thickness and the distribution of particles within. The quantification of elements is based on the standardless method, but the elements with atomic number Z < 13 were not determined since the measurement is made in air. Since the total composition of the sample was not calculated, the element concentrations were accepted only as relative. Precision values did not exceed 10 % for all elements. 14 types of foraminifera shells (129 samples in total) were analyzed by the TXRF method and the following elements were determined: Cl, K, Ca, Mn, Fe, Zn, Sr. Application of principal component analysis showed the difference among samples with a respect to diagenetic alternation degree. The results of diagenetic studies were confirmed by literature data.