Abstract
The minerals in the hydrothermal and cold seep system form at different temperatures and show responses to the laser power to varying degrees. Here, we focus on the heat-induced by laser to study thermal transformations of the chalcopyrite, covellite, pyrite, barite, and aragonite based on Raman spectroscopy. Chalcopyrite mainly transforms into hematite, and covellite mainly transforms into chalcocite with the increase of laser power. Interestingly, comparing with the previous study, the pyrite can transform to the marcasite firstly, and form hematite finally. We also find that high-temperature opaque chalcopyrite is more likely to occur thermal transformations due to the smaller absolute energy difference (|ΔE1|) based on the frontier orbital theory. In contrast, the oxysalt minerals won’t transform into new components under high laser power. However, the structure of the barite has been destroyed by the high laser power, while the more transparent aragonite is not affected by the high laser power due to the laser penetrates through the transparent aragonite crystal and causes little heat absorption. Finally, we established the minimum laser power densities for thermal transformations of these minerals formed under different environments. The above study provides a simple way to study the thermal transformations of minerals by the local heat-induced by laser and also enlightens us to identify the minerals phases precisely.
Highlights
The hydrothermal and cold seep system is one of typical extreme environments in the deep-sea.The shocking discoveries of deep-sea hydrothermal in the 1970s have been crucial for the formation of ore resources, the supply of exotic deep-sea ecosystems, and even for the origin of life [1,2]
The samples are mainly composed of sulfide and oxysalt minerals
The effects of laser power on samples formed at different temperatures show obvious differences, especially in sulfide minerals from samples formed at different temperatures show obvious differences, especially in sulfide minerals the hydrothermal system
Summary
The hydrothermal and cold seep system is one of typical extreme environments in the deep-sea. Sulfides are typical mineral resources, provide important evidence of hydrothermal activity, and reflect different physicochemical environments [3,4,5]. The minerals from hydrothermal and cold seep system form at different temperatures reflect different physicochemical environments. The study of the formation and transformations process of sulfide and oxysalt mineral is conducive for identifying theses minerals, indicating the fluid activities and assessing the ore resources precisely. Whether the heat caused by high laser energy affects the transformation process of hydrothermal sulfides and carbonate minerals is worthy of studying. There is a lack of systematic research comparing the thermal transformations of minerals formed at different temperatures in the hydrothermal and cold seep system. We focus on the thermal transformations of typical sulfides and oxysalt minerals formed at different temperatures based on the heat-induced by laser. We can deepen the cognition of optical characteristics of minerals via the responses of different minerals to laser energy
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