Discovery of Gold Nanoparticles in Marcellus Shale

Abstract

A high density of gold (Au) nanoparticles has been observed on the surfaces of the coexisting opal nanospheres in kerogen-bearing shales from the Marcellus Formation. Our analyses of the Au nanoparticles and associated minerals indicate that this represents a new formation type of colloidal gold nanoparticles. Additionally, the opal nanospheres are a new kind of natural opal-A that is characteristic of the mesoporous texture formed through oil-in-water emulsion processes. High-resolution transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy analysis directly reveals spherical gold nanoparticles and gold nanorods associated with mesoporous opal nanospheres. Our newly found textures indicate that opal nanospheres may have facilitated the co-precipitation of pure gold nanoparticles in organic-bearing, reduced environments. Furthermore, our TEM observations provide distinct images of the initial phase of colloidal gold and silica, which may contribute to the formation of Au deposits involving “invisible” gold, secondary supergene enrichments, or high-grade gold accumulations. The discovery of Au nanoparticles in hydrocarbon-rich shale formations such as Marcellus (which contains 0.6–4.1 wt % gold/opal) suggests a potential for co-production of both gas/oil and goldtwo valuable commodities.

Predicting Destabilization in Salt-Containing Aqueous Reverse Micellar Colloidal Systems

“…7−9 New insights on the formation of particles, as disparate as atmospheric aerosols that begin as microlayer droplets at sea surface and mesoporous opal nanoparticles in shales from the Marcellus Formation, have been gained by making comparisons to microemulsion systems created in laboratories. 10,11 A critical intersection of natural phenomena and human engineering, reverse micellar water-in-oil (w/o) microemulsions, has been used in the creation of multilayered nanoparticles called earthicles, created specifically to mimic the structure and composition of the earth's layers at a much smaller scale. 12−14 Thus, with colloidal chemistry reaching into so many aspects of earth and environmental science and engineering, continually deepening our understanding of the structure and stability of colloidal systems has an equally farreaching impact on our ability to predict natural phenomena and chemical behaviors in complex environments.…”

“…A variety of important relationships intersecting natural phenomena and human engineered systems can be found within the field of colloid and emulsion science. For example, the flow of contaminants such as lead, mercury, and chromium in natural water sources occurs through colloidal transport processes. − Emulsions and microemulsions impact crude oil spills on natural water sources, − guiding engineers to develop methods to separate oil from water after these disasters occur. − New insights on the formation of particles, as disparate as atmospheric aerosols that begin as microlayer droplets at sea surface and mesoporous opal nanoparticles in shales from the Marcellus Formation, have been gained by making comparisons to microemulsion systems created in laboratories. , A critical intersection of natural phenomena and human engineering, reverse micellar water-in-oil (w/o) microemulsions, has been used in the creation of multilayered nanoparticles called earthicles, created specifically to mimic the structure and composition of the earth’s layers at a much smaller scale. − Thus, with colloidal chemistry reaching into so many aspects of earth and environmental science and engineering, continually deepening our understanding of the structure and stability of colloidal systems has an equally far-reaching impact on our ability to predict natural phenomena and chemical behaviors in complex environments.…”