Nanominerals and petrogenetic-metallogenic processes in the Earth sphere system

<sec><p indent="0mm">Nanominerals are widely distributed within the interior and surface environments of the Earth, including mineral phases that are stable only at the nanoscale <sc>(1–100 nm),</sc> nanoparticles of macroscopic mineral phases, and particles with special nanoscale effects at the submicron scale. Nanominerals have extremely high specific surface area and proportion of surface atoms and thus exhibit unique chemical, physical, and electrical properties distinct from those of their macroscopic counterparts. This paper summarizes the characteristics of minerals formed at the nanoscale and submicron scales in deep-and shallow-Earth environments, and their significance in finely recording and indicating rock-forming and mineralization processes. </sec><sec> The formation of nanominerals involves diverse geological processes in deep-and shallow-Earth environments, including crystallization, dynamic mechanical action, weathering, and biomineralization. In a deep-Earth environment, nanominerals crystallize from highly reduced fluids and melts and occur as inclusions within diamond, chromite, and other minerals. These nanominerals include Qingsongite, coesite pseudomorphs after stishovite, and Ca-Si perovskite, forming an assemblage characteristic of the deep mantle. In the Sulu-Dabie ultrahigh-pressure metamorphic belt, rapid subduction and exhumation induced submicron monalbite and nanoscale omphacite exsolution in jadeite. The dislocations and microtwin domains in omphacite and garnet record micro-deformation mechanisms of continental deep subduction. In shallow surface environments, variable physicochemical conditions, active weathering processes, and microbial activity promote the decomposition of primary minerals and the formation of secondary nanominerals. Reactions among gas, liquid, and solid phases in the atmosphere, seawater spray evaporation, and the organic matter-and microbial-mediated regulation of mineral crystal faces can all generate nanoparticles. Fault friction, slow crystallization in soils and water, and impurity constraints also led to the formation of some mineral particles at the nanoscale. </sec><sec> Nanominerals provide critical microscopic evidence for revealing metallogenic mechanisms. Nanoscale exsolution structures in the Panzhihua V-Ti magnetite deposit record magma-cooling pathways. In hydrothermal deposits, alteration of amphibole produces nanoscale chlorite and zeolite, documenting the chemical evolution of the fluid. Nano-gold in Carlin-type deposits occurs within pyrite, which is controlled by the Au/As ratios of fluids. The gold-bearing nanoparticles in volcanic vapor and geothermal systems associate with amorphous silica and carbon and are controlled by redox conditions. Moreover, the deformation of pyrite promotes the migration of Au-Ag clusters and further forms nanoparticles. In weathering deposits, nanoscale REE minerals on clay surfaces reflect supergene enrichment. These characteristics provide irreplaceable constraints for reconstructing metallogenic conditions. </sec><sec> Nanominerals exhibit multidimensional growth characteristics, with pyrite displaying one-dimensional whiskers, two-dimensional lamellae, and three-dimensional granular morphologies that can transform among each other. Experimental results demonstrate that pyrite tends to form {210} and {111} faces at medium-high temperatures, favoring gold adsorption and precipitation, whereas {100} faces have low surface reactivity, which is unfavorable for gold precipitation. The existence of framboidal pyrite indicates reducing depositional environments, while whisker morphologies reflect gas-liquid phase transitions. In ion-adsorption REE deposits, rare Earth elements are enriched through adsorption by nanoscale clay minerals, and the formation of REE nanominerals, e.g, goethite, is controlled by fluid pH value. In addition, ascending geogas can transport nanometal particles from concealed ore bodies to the surface. Collecting and analyzing these nanoparticles enables effective prediction of deep-seated mineralization. </sec><sec> In summary, various types of nanominerals can provide new mineralogical evidence for the study of the mobilization, migration, and enrichment of elements. These nanoscale records offer essential insights into ore-forming processes, provide indicators for exploring concealed deposits and deep prospecting, and provide a theoretical basis for the comprehensive utilization of ore resources. </sec>