Low Temperature Illitization through Illite-Dioctahedral Vermiculite Mixed Layers in a Tropical Saline Lake Rich in Hydrothermal Fluids (Sochagota Lake, Colombia)

Gabriel Ricardo Cifuentes,Juan Jiménez-Millán,Rosario Jiménez-Espinosa,Claudia Patricia Quevedo,Javier Cuadros,Fernando Nieto

doi:10.3390/min11050523

Gabriel Ricardo Cifuentes, Juan Jiménez-Millán + Show 4 more

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https://doi.org/10.3390/min11050523

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Abstract

In this investigation, we showed that high salinity promoted by hydrothermal inputs, reducing conditions of sediments with high content in organic matter, and the occurrence of an appropriate clay mineral precursor provide a suitable framework for low-temperature illitization processes. We studied the sedimentary illitization process that occurs in carbonaceous sediments from a lake with saline waters (Sochagota Lake, Colombia) located at a tropical latitude. Water isotopic composition suggests that high salinity was produced by hydrothermal contribution. Materials accumulated in the Sochagota Lake’s southern entrance are organic matter-poor sediments that contain detrital kaolinite and quartz. On the other hand, materials formed at the central segment and near the lake exit (north portion) are enriched in organic matter and characterized by the crystallization of Fe-sulfides. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and energy dispersive X-ray spectrometry (EDX) data allowed for the identification of illite and illite-dioctahedral vermiculite mixed layers (I-DV), which are absent in the southern sediments. High humidity and temperate climate caused the formation of small-sized metastable intermediates of I-DV particles by the weathering of the source rocks in the Sochagota Lake Basin. These particles were deposited in the low-energy lake environments (middle and north part). The interaction of these sediments enriched in organic matter with the saline waters of the lake enriched in hydrothermal K caused a reducing environment that favored Fe mobilization processes and its incorporation to I-DV mixed layers that acted as mineral precursor for fast low temperature illitization, revealing that in geothermal areas clays in lakes favor a hydrothermal K uptake.

Highlights

IntroductionThere is increasing evidence that fast clay mineral reactions can act as important element sinks in sedimentary and diagenetic processes
The mineral precursor is detrital mixed-layer illite-dioctahedral vermiculite mixed layers (I-DV) incorporated into the lake by the El Salitre River, which discharges to the south of the lake

Summary

Introduction

There is increasing evidence that fast clay mineral reactions can act as important element sinks in sedimentary and diagenetic processes. High concentration of cations and biological activity are frequently due to specific sediment composition, hydrology, and climatic conditions, such as those that can be generated in saline lakes or mangrove soils [6,7,8,9]. In these environments with hydrologically restricted conditions, clays of detrital origin interact with high salinity waters, producing phase authigenesis

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