地质科技通报 (Sep 2022)
Geological process and carbon cycle significance of graphite carbon material in faults and subduction zones
Abstract
Carbon is a common element in nature that exists in various forms, including single minerals (e.g., graphite and diamond), compounds (e.g., carbonate and carbon dioxide) and organic carbon in organisms. Graphitized carbonaceous materials often form or appear in the rocks of fault zones or subduction zones at different crustal depths and are especially abundant in some large earthquake fault zones. Previous studies have shown the significant role and status of graphitized carbonaceous materials in rock deformation behavior and geological evolution processes. This reveals that the texture of graphite crystals is sensitive to temperature. In the geological process, the crystalline order of carbonaceous materials, that is, the graphitization process, is irreversible, so that the peak metamorphic temperature can be recorded quantitatively. Graphite crystals also have other special structural and physical mechanical properties. Duringthe deformation process, it can effectively reduce the strength of rock and promote plastic deformation. The graphite material in the crust can weaken the rock strength and cause seismic fault slip, which plays an important role in thesolid lubricant and rheological weakening process of faulting or deformation in the fast-sliding or seismic sliding plane. Graphitic carbonaceous materials have low solubility and low mobility and often exist in the deep crust as carbon sinks. On the geological time scale, once carbon and graphitization participate in the rocks together, some major geological processes, such as subduction, faulting, weathering and erosion, as well as biological processes, can cause graphite carbonaceous materials to enrich or release carbon to the earth's surface (atmosphere) through the formation and destruction process, which will significantly affect the carbon cycle.
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