Original paper

The occurrence and geochemistry of huntite from Neogene lacustrine sediments of the Yalvac-Yarikkaya Basin, Isparta, Turkey

Yavuz, Fuat; Kirikoğlu, Mehmet Sezai; Özden, Gökhan

Abstract

Huntite-magnesite assemblages were formed as a result of Neogene tectonic activity in a shallow lacustrine YalvaçYarikkaya basin in the Isparta Bend, southwestern Turkey. The study area hosts two sediment-hosted magnesite occurrences where extremely white huntite levels up to 2 meter-thick were formed intercalated with dolomite. The basement comprises dolomitic and ultrabasic rocks that were thought the primary source of magnesium-rich formations. The huntite occurs both as massive form and void-fillings in dolomite. SEM studies show that the Yalvaç huntite is composed of randomly oriented fine-grained platy crystals (< 6μm), which were seen in the form of face-to-face aggregates. the icp-es analyses indicate that the mgo contents of huntite range between 30.29 to 36.05 wt.% with an average of 32.70 wt.%. on the other hand, the cao contents of huntites vary relatively in a wide range (9.57 to 18.82 wt.%) with an average of 13.84 wt.%. the yalvaç huntites are characterized by relatively high as (9.20 –118.00 ppm), sr (363.30 – 654.40 ppm), b (130 – 223 ppm), li (16.30 – 33.50 ppm), ba (71.15 –148.00 ppm), and zr (2.00 –17.40 ppm) contents. it was designated that in a measured vertical lithological unit consisting of entirely dolomite, magnesite, huntite, and to a lesser extent calcite, the trace elements such as as, b, li, zr, sb, and co were preferentially concentrated within the huntite zones. the icp-ms analyses point out that the amount of rare-earth elements in huntite is significantly low (Σ ree = 0.34 to 4.19 ppm) and, in most cases, close to the detection limits. huntites show marked negative ce and eu anomalies in chondrite-normalized ree patterns. combined dta and tga curves of the yalvaç huntite show two characteristic endothermic peaks at 618.6 and 811.1 °c that resulted from the decompositions of mgco3 and CaCO3 components, respectively with a 40 % weight loss on heating 1200 °C. The Mg/Ca mole ratios of huntite range between 2.04 and 3.85 with an average of 2.77.

Keywords

huntitelacustrinetrace elementrare-earth elementdifferential thermal analysisthermogravimetrysouthwestern turkey