Massive formation of early diagenetic dolomite in the Ediacaran ocean: Constraints on the "dolomite problem"

Quantitative Characterization of Inorganic Pores in Sinian Doushantou Dolomitic Shale Based on FIB-SEM in Western Hubei Province, China

Unlike traditional shale gas reservoirs, where organic matter pores dominate, inorganic pores are the primary reservoir space in the Sinian (Ediacaran) high-maturity Doushantou dolomitic shale in western Hubei Province, China. The inorganic pore characteristics of Doushantuo shale and its influence on shale gas aggregation were investigated by examining the TOC content, thermal maturity, mineralogical composition, and field-emission scanning electron microscopy (SEM) and focused ion beam scanning electron microscopy (FIB-SEM) of drill cores. The results show that the shale mineral composition in the study area is primarily dolomite and plate-shaped interparticle-intercrystalline pores associated with dolomite are widespread inorganic pores in dolomitic shale. Interparticle-intercrystalline pores account for 75% of the total pores, with a pore size distribution mainly between 50 and 300 nm, as extracted from the 3D pore network model (PNM). Compared with organic pores, interparticle-intercrystalline pores provide greater space for gas storage and have a strong coupling relationship with the hydrocarbon generation and evolution of organic matter. Therefore, the inorganic pores in the Doushantuo Formation play a vital role in the enrichment and accumulation of shale gas. This study aims to establish a scientific basis for understanding the enrichment mechanism of shale gas in Doushantuo dolomitic shale and other inorganic pore-dominated shales in southern China.

Dissolution enables dolomite crystal growth near ambient conditions

Crystals grow in supersaturated solutions. A mysterious counterexample is dolomite CaMg(CO3)2, a geologically abundant sedimentary mineral that does not readily grow at ambient conditions, not even under highly supersaturated solutions. Using atomistic simulations, we show that dolomite initially precipitates a cation-disordered surface, where high surface strains inhibit further crystal growth. However, mild undersaturation will preferentially dissolve these disordered regions, enabling increased order upon reprecipitation. Our simulations predict that frequent cycling of a solution between supersaturation and undersaturation can accelerate dolomite growth by up to seven orders of magnitude. We validated our theory with in situ liquid cell transmission electron microscopy, directly observing bulk dolomite growth after pulses of dissolution. This mechanism explains why modern dolomite is primarily found in natural environments with pH or salinity fluctuations. More generally, it reveals that the growth and ripening of defect-free crystals can be facilitated by deliberate periods of mild dissolution.

Eco-engineering approaches for ocean negative carbon emission

The goal of achieving carbon neutrality in the next 30-40 years is approaching worldwide consensus and requires coordinated efforts to combat the increasing threat of climate change. Two main sets of actions have been proposed to address this grand goal. One is to reduce anthropogenic CO₂ emissions to the atmosphere, and the other is to increase carbon sinks or negative emissions, i.e., removing CO₂ from the atmosphere. Here we advocate eco-engineering approaches for ocean negative carbon emission (ONCE), aiming to enhance carbon sinks in the marine environment. An international program is being established to promote coordinated efforts in developing ONCE-relevant strategies and methodologies, taking into consideration ecological/biogeochemical processes and mechanisms related to different forms of carbon (inorganic/organic, biotic/abiotic, particulate/dissolved) for sequestration. We focus on marine ecosystem-based approaches and pay special attention to mechanisms that require transformative research, including those elucidating interactions between the biological pump (BP), the microbial carbon pump (MCP), and microbially induced carbonate precipitation (MICP). Eutrophic estuaries, hypoxic and anoxic waters, coral reef ecosystems, as well as aquaculture areas are particularly considered in the context of efforts to increase their capacity as carbon sinks. ONCE approaches are thus expected to be beneficial for both carbon sequestration and alleviation of environmental stresses.

A critical review of mineral-microbe interaction and coevolution: mechanisms and applications

The mineral-microbe interactions play important roles in environmental change, biogeochemical cycling of elements, and formation of ore deposits. Minerals provide both beneficial (physical and chemical protection, nutrients, and energy) and detrimental (toxic substances and oxidative pressure) effects to microbes, resulting in mineral-specific microbial colonization. Microbes impact dissolution, transformation, and precipitation of minerals through their activity, resulting in either genetically-controlled or metabolism-induced biomineralization. Through these interactions minerals and microbes coevolve through Earth history. The mineral-microbe interactions typically occur at microscopic scale but the effect is often manifested at global scale. Despite advances achieved through decades of research, major questions remain. Four areas are identified for future research: integrating mineral and microbial ecology, establishing mineral biosignatures, linking laboratory mechanistic investigation to field observation, and manipulating mineral-microbe interactions for the benefit of humankind.