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Keywords

carbonatite formation

Abstract

Geothermal activity such as hot springs are known to precipitate calcium carbonate (CaCO3) minerals, producing rocks such as tufa, travertine and sometimes associated with carbonatite. The precipitation of CaCO is caused by the reduction of CO, which is less soluble in warmer waters. Geothermal heating of water in natural springs drives this precipitation of CaCO3 in areas of Arkansas including Magnet Cove. Magnet Cove, Arkansas is an alkalic igneous rock complex that is composed of a series of ring dikes post-Mississippian in age. These dikes have intruded into faulted and folded Paleozoic sedimentary rocks. One of these igneous dikes is carbonatite, a rare carbonate-rich igneous rock. The formation of carbonatite remains unclear to this day. It may form from magmatic solutions, hydrothermal metasomatism, or a combination of both. If carbonatite is formed through hydrothermal metasomatism, then it likely formed through repeated events of redeposition and recrystallization. On the other hand, if carbonatite is formed through magmatic means, then its parental magma must be some type of alkalic composition. In this study, a carbonate-rich core sample was taken from Magnet Cove at the depth range of 10 feet to 55 feet below ground. Five samples were processed for analysis at every 10 feet. Petrographic and X-Ray Diffraction (XRD) analysis was conducted on each sample to investigate the mineralogy and better understand the chemical alterations the area experienced. Samples one, two, and five were primarily calcite, while Sample four contained calcite with some apatite. Sample three was unique, containing calcite, natrolite, epidote, and chlorite, suggesting hydrothermal alteration. The presence of these minerals raises the possibility that carbonatite, if sample Three is indeed carbonatite, may form through hydrothermal processes.

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