The efficient recovery of critical minerals, such as nickel (Ni) and manganese (Mn) from the subsurface, is of vital importance, given their role in modern technologies ranging from energy storage to advanced alloys. This study presents a chelation-driven strategy to enhance critical mineral recovery from ultramafic rocks under ambient pressures and systematically evaluates key controls on extraction processes for the first time. Using EDTA and 1,3-PDTA as model chelating agents, we show that the stability of the metal-ligand chelate exerts first-order control of mineral-fluid interfacial reactivity and ring strain with metal and, consequently, net dissolution rates. To further highlight the ability for optimization, fluid exchange and variation of the fluid-to-rock ratio experiments were conducted, revealing tunable controls for engineering recovery. Under optimized conditions, Ni and Mn extraction efficiencies reach ∼ 95% and ∼ 80%, respectively. When extrapolated to the Twin Sisters Formation in the United States, these results correspond to recovering over 26 times the current global Ni production, and ∼ 1.5 times of the current global Mn production, even if only 5% of the formation were reacted. From both in situ and ex situ mining perspectives, this work demonstrates that chelation chemistry provides a tunable, transformative pathway for unlocking mineral extraction from unconventional resources while mitigating supply chain vulnerabilities.

The Earth's crust contains reactive, igneous reservoirs that can be utilized to turn atmospheric CO2 into new carbonate minerals. Carbon mineralization technology relies on the reactions between crustal reactants (rock, water, and biota) and injected CO2 to release divalent cations that can participate in the precipitation of new carbonate minerals. Field CO2 injection tests in mafic-ultramafic lithologies around the world have opened a window into the reactive potential of the subsurface. Knowledge and technology gained from the decades of carbon mineralization research will push forward efforts in unlocking innovative ways to approach subsurface critical mineral resources, hydrogen generation, geothermal energy, water resource management, waste storage, gas storage, and hydrocarbon extraction. Our review describes a holistic view of subsurface mafic-ultramafic reservoirs, carbon mineralization reactions, field tests, and future opportunities for using the subsurface Earth as a Reactor.

Belite-rich cement is a promising low-carbon material, yet the limited hydraulic reactivity of its primary component, dicalcium silicate (/i-Ca2SiO4), still poses a challenge. This study introduces a new approach to examining the reaction kinetics and acceleration strategies for low-reactivity materials like /i-Ca2SiO4 using quasi in situ X-ray diffraction (XRD). By simultaneously analyzing pre-cured and fresh samples, the method reduces measurement time at the expense of lowering temporal resolution. Applying this technique to hydrating /i-Ca2SiO4 pastes from 21 to 80 degrees C provides insight into the underlying temperature-dependent dissolution process and its apparent activation energy (AAE). The estimated AAE of 49 +/- 3 kJ/mol aligns with existing data and supports the view that the rate-limiting step of belite hydration may change based on the physical properties of the material. By offering phase-specific and time-resolved data, this method serves as a useful tool in devising science-informed strategies to accelerate hydration of belite-rich cements.

Abstract The global demand for critical minerals and materials (CMM) is rapidly outpacing conventional supply chains. This Perspective presents a paradigm shift by demonstrating that mature U.S. sedimentary basins are not merely depleting fuel reservoirs but are vast, accessible repositories of mineral wealth. By integrating in-situ mining (ISM) chemistries into existing oil and gas infrastructure, we can leverage billions of dollars in sunk capital to address modern supply chain bottlenecks while simultaneously enhancing energy recovery. Our analysis of 13 U.S. hydrocarbon reservoirs identifies 15 critical elements, including titanium, vanadium, nickel, cobalt, etc., ubiquitous within the sedimentary matrix. We highlight that 1% enhanced recovery rate of hydrocarbon from the existing reservoirs and 1% recovery rate of CMM from 5% of these accessible formation volumes could yield over 530 million barrels of oil, 6 Tcf natural gas, and 500 million metric tons of CMM, providing scale context for the potential energy and material significance of sedimentary coproduction. Future research should focus on optimizing selective lixiviants that maintain reservoir integrity while maximizing yields of CMM and hydrocarbons within a closed-loop system. Redefining the Earth as a Reactor offers a pragmatic and low-footprint pathway to secure national industrial competitiveness and advance technological leadership.

The Tamarack ultramafic intrusion in Minnesota, USA, may be suited to host concurrent CO2 injection and critical mineral recovery. These dual capabilities are vital to manage emissions and supply metals (e.g., nickel) necessary for rapidly upscaling energy and data technologies. To understand subsurface carbonation reaction pathways and assess mineralization potential in the Tamarack Intrusive Complex (TIC), we reacted a suite of Tamarack Bowl intrusion olivine (BIO) samples with aqueous-dissolved and liquid or supercritical CO2 (scCO2) at 90 bar and 21-90 degrees C. Samples were characterized pre- and postreaction with multiple geochemical and mineralogical techniques, and results indicate mineral dissolution followed by magnesite precipitation. Pseudo in situ Identical Location Transmission Electron Microscopy (IL-TEM) experiments revealed that a carbonation reaction of TIC BIO peridotite with water-saturated scCO2 formed aragonite nanocrystals on an altered plagioclase surface and induced dissolution of nickel-bearing forsteritic olivine. The presence of nanoscale-resolved carbonation products identified by IL-TEM, coupled with carbonate transformation rates quantified in batch reactions, suggests that the TIC BIO resource can conservatively store 320-1,070 million metric tonnes (MMT) of CO2 via mineralization while mobilizing 0.9-3.1 MMT of nickel if only 5% of the TIC rock volume is accessed.

Double carbonates are minerals with a calcite-type structure with alternating cation layers composed of Ca and Mg/Fe coordinated by carbonate groups. While the perfectly ordered AB-stacked crystal is the thermodynamically most stable configuration, natural mineral formation pathways can leave signatures through kinetically trapped disorder, such as AB antisite cation substitutions. This study probes the degree of cation ordering in naturally occurring double-carbonate samples. In particular, the dependence of structural order on the distribution of Fe A and B crystallographic sites (the A site is the Ca layer, and the B site is the Mg/Fe layer) is examined. Mössbauer, X-ray diffraction, X-ray absorption spectroscopies (both the X-ray absorption near edge structure, XANES, and extended X-ray absorption fine structure, EXAFS), and energy-dispersive X-ray spectroscopy were used to collect a comprehensive experimental data set, which we interpret using density functional theory to elucidate the structural effects of cation disorder. Our results show that the A (nominally Ca) site can host a relatively high Fe fraction. We discuss the implications in terms of mineral formation.

The global demand for critical minerals and materials (CMM) is rapidly outpacing conventional supply chains. Traditionally, CMM extraction and hydrocarbon production have operated as segregated industries, with the former often requiring energy-intensive mining of greenfield sites. This Perspective presents a paradigm shift by demonstrating that mature U.S. sedimentary basins are not merely depleting fuel reservoirs but are vast, accessible repositories of mineral wealth. By integrating in-situ mining (ISM) chemistries into existing oil and gas infrastructure, we can leverage billions of dollars in sunk capital to address modern supply chain bottlenecks while simultaneously enhancing energy recovery. Our analysis of thirteen major unconventional U.S. hydrocarbon reservoirs identifies a robust endowment of fifteen critical elements, including titanium, vanadium, nickel, cobalt, etc., ubiquitous within the sedimentary matrix. We highlight that 1% enhanced recovery rate of hydrocarbon from the existing reservoirs and 1% recovery rate of CMM from 5% of these accessible formation volumes could yield over 5 billion barrels of oil, 60 Tcf natural gas, and 500 million metric tons of CMM, contextually sufficient to revolutionize energy landscapes and advanced manufacturing. Future research must focus on optimizing selective lixiviants that maintain reservoir integrity while maximizing yields of CMM and hydrocarbons within a closed-loop system. Redefining the subsurface as an integrated factory (earth as a reactor) offers a pragmatic and low-footprint pathway to secure national industrial competitiveness and advance technological leadership.

The Tamarack Intrusive Complex (TIC), located in Minnesota, USA, is a globally unique ultramafic lithology consisting primarily of poorly consolidated peridotite. CO2 enhanced mineral recovery (CO2-EMR) strategies may be implemented in deep ultramafic formations, including in the Tamarack Bowl intrusion olivine (BIO), to store injected carbon while recovering critical minerals. To better understand the TIC BIO's unique potential for carbon mineralization and critical mineral mobilization, samples from a Tamarack BIO borehole were analyzed with a suite of geochemical and mineralogical tools. We employed micro-X-ray fluorescence spectroscopy mapping and X-ray photoelectron spectroscopy to understand elemental distributions and quantify spatially resolved chemical compositions on olivine grain surfaces. We captured samples' bulk mineralogy with X-ray diffraction and scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. This analysis reveals that Tamarack BIO is rich in nickel-bearing forsteritic olivine, suggesting critical mineral extraction via nickel mobilization may be achieved during carbon mineralization-driven dissolution. The non-reactive carbon storage potential in the Tamarack BIO resource ranges from 0.85-117 million metric tonnes (MMT) of CO2 based on our various reservoir property estimations. Results of our geochemical analyses for the Tamarack site indicate that if only 5% of the BIO was accessed with CO2-EMR, fluid-rock reactions could enable recovery of up to 4.1 MMT Ni and 1.2 MMT Co and permanently mineralize 1.4 billion metric tonnes of CO2. Given the significant revenue potential of critical mineral export, the TIC exhibits unique potential both as a domestic critical mineral source and a gigaton-scale carbon storage site in the United States.

Rare earth elements (REE) are critical to technological advancements, yet elevated concentrations as seen in the few known conventional deposits are uncommon. Understanding the distribution of REE in sedimentary systems is important to securing REE resources from unconventional deposits. Studies addressing the mobilization of REE in sedimentary basins focus on a single fluid phase rather than multiphase fluid, oil-water systems. We strategically chose the Phosphoria Total Petroleum System (PTPS) in the Intermountain West of the United States to investigate mobilization and partitioning of REE between oil, water, source rock, and reservoir rock. The PTPS has REE-enriched source rock from which hydrocarbons have undergone large-volume, long-distance migration. Our data show REE concentrations are five orders-of-magnitude higher in source rock than in oil and are an average of six times greater in oil than in water. We report a near 100:1 ratio of lighter mass REE in oil relative to water decreasing to ~1:1 for the heavier mass REE, suggesting mobilization, preferential partitioning, and redistribution of REE by hydrocarbons. Such redistribution of critical minerals by hydrocarbons may represent an underrecognized link between carbon and metal cycling in sedimentary basins, with implications for metal fate and transport, unconventional critical mineral resources, and sustainable subsurface energy systems globally.

In a global emergency on the supply chain of critical minerals, ultramafic rocks from Duke Island Complex in southeastern Alaska and Kenai Complex in southcentral Alaska provide promising new information on the prospect of acquisition of Ni and Co. Olivine [Mg, Fe)2SiO4] in wehrlite and olivine clinopyroxenite rocks from Duke Island contains from 152 to 749 ppm of Ni and from 254 to 520 ppm of Co. Olivine in dunite from Kenai contains Ni between 798 and 4518 ppm and Co up to 288 ppm. In both locations, Ni shows a positive correlation with forsterite mol.% of olivine, as dictated by fractional crystallization of parental magmas, but Co shows a negative relationship. Using a new CO2-enhanced mineral recovery technique on a hypothetical 1 km3 of ultramafic rock, representative of each rock-type at Kenai and Duke Island, and assuming a 5% reaction rate of olivine it is calculated that up to 460,000 metric tons of Ni can be obtained from Kenai and up to 36,000 metric tons of Co can be recovered from Duke Island. These results indicate that a large group of ultramafic rocks in southern Alaska possess powerful potential for the extraction of Ni and Co.

Cracking fundamentally limits the durability of cementitious materials, while most self-healing strategies rely on encapsulated agents or high additive loadings that restrict repeatability, scalability, or mechanical performance. Here we report a cement composite incorporating an ultra-low polymer concentration (<0.15 wt%) that enables autonomous, multi-cycle crack healing without capsules or vascular networks and with minimal impact on hydration, setting, or workability. The system forms an in-situ poly(acrylic acid)/poly(ethylene oxide)/branched poly(ethylene imine) complex that establishes reversible electrostatic and hydrogen-bonding interactions with both itself and cement hydration products, creating a molecular-scale "Velcro" network. High-resolution X-ray computed tomography and optical microscopy reveal rapid polymer redistribution and crack sealing, including closure through a ~ 2 mm-deep fracture within ~4 h, corresponding to healing rates of ~10 mm·day⁻¹. Time-resolved confocal Raman spectroscopy identifies bi-exponential kinetics with characteristic times of ~10 min and ~9 h, consistent with multi-stage polymer transport and interfacial reorganization, and corroborated by identical-location SEM-EDS observations. Mechanical testing under a severe post-peak loading protocol (20% strength loss beyond the maximum) shows strength recovery of up to 62% in compression and 59% in direct tension, with sustained recovery across multiple damage-healing cycles. These results demonstrate that reversible polymer-cement interactions coupled with efficient pore-scale transport enable rapid, repeatable self-healing at exceptionally low additive concentrations, providing a scalable pathway toward longer-lived and more sustainable concrete infrastructure.

Global demands to secure critical mineral supply chains, manage water resources, and store energy long-term require innovative resource management strategies. Subsurface basalt reservoirs potentially offer an unconventional dual-purpose approach to mining and energy storage, where compressed air energy storage can be coupled with water remediation strategies for the extraction of economically important and environmentally relevant elements. This study utilizes static batch experiments conducted on Columbia River Basalt Group samples to evaluate long-term fluid-rock interactions relevant to coupled subsurface applications. Samples were reacted under elevated temperature and pressure conditions, for 296 and 4061 days, providing a unique data set to assess geochemical evolution, element partitioning, and aqueous chemistry over decadal time scales. The alteration was dominated by silicate, aluminosilicate, and oxide phases. Progressive hydrothermal alteration increased the cation exchange capacity through the formation of secondary minerals (e.g., clays and zeolites), influencing solute retention, ion exchange behavior, and aqueous chemistry. Grain-scale and bulk analyses revealed selective cation release and retention patterns, establishing a mechanistic baseline for predicting element mobility. These geochemical constraints inform the prospective use of enhanced metal recovery for critical resources (e.g., Mn, Mg, Ti, and Fe) and associated water quality impacts, providing a foundation for the design and management of engineered fluid-rock systems in unconventional basalt reservoirs.

Subsurface injection of carbon dioxide (CO2) into mafic-ultramafic rocks for permanent storage via mineralization is being studied to reduce emissions. We investigated the carbonation products of enstatite (MgSiO3) to assess its efficiency in sequestering CO2 for safe and permanent storage as carbonate minerals. This was accomplished by conducting variable temperature carbonation reactions with samples of differing crystallinities and surface chemistries. Reaction progress was monitored utilizing in situ X-ray diffraction, and the presence of carbonate products was confirmed using additional techniques, such as thermogravimetric analysis coupled with mass spectrometry and scanning electron microscopy with energy dispersive spectrometry. Our results show that crystalline enstatite produces small amounts of the anhydrous form of MgCO3 (magnesite), while amorphous MgSiO3, which was used to simulate mafic glass, more readily converts to the hydrated/hydroxylated hydromagnesite [Mg5(CO3)4(OH)24H2O]. These results, supplemented with dynamic vapor sorption experiments, suggest that surface properties play a significant role in the pathway and degree of carbonation. These developments concerning the reactivity of CO2 with reactive mafic phases will help further our understanding of the reactivity of these mafic-ultramafic minerals with implications for permanent carbon storage and other subsurface engineering scenarios involving reactive reservoirs.

Carbon mineralization in humidified carbon dioxide offers a promising route to mitigate anthropogenic emissions in a world stressed by water security. Despite its technological importance, our understanding of carbonation in water-poor environments lags, as traditional dissolution-precipitation pathways struggle to explain the adsorbed water nanofilm-mediated reactivity. Here, we utilize in operando X-ray diffraction (XRD) and advanced molecular simulations to investigate nanoconfined reactions driving forsterite carbonation, the magnesium-rich olivine. By examining magnesium ion dissolution and transport in atomistic simulations of the forsterite-water-carbon dioxide interface and comparing these with the in operando XRD activation energies, we identify both processes as rate-limiting at saturation. Our simulations reveal a mechanistic view of interfacial carbonation, where dissolution and precipitation are mediated by anomalous quasi two-dimensional diffusion. The transport process involves intermittent diffusive hopping in the desorbed state, separated by crawling events that are spatially short but temporally long. This understanding transcends carbon mineralization, with implications for understanding the transport of contaminants in geosystems, the design of multifunctional materials, water desalination, and molecular recognition systems.

The transition towards green energy requires both carbon dioxide removal and consistent supplies of energy-critical minerals. Injection and mineralization of supercritical CO2 at active mafic and ultramafic-hosted mines provides a potential avenue to achieve both, through the stable geologic storage of carbon and subsequent mobilization of critical metals. A sample from the Eagle occurrence, an ultramafic-hosted sulfide deposit in Michigan, USA that is the only active Ni mine in the United States, was characterized both before and after reaction with supercritical CO2 at elevated pressure and temperature. We present the changes in mineralogy, feature relocation, and potential for carbon mineralization and critical mineral recovery based on the comparison of pre- and post-reaction datasets. Herein, we present evidence of dissolution-precipitation reactions leading to carbon mineralization and critical mineral mobilization driven by water-saturated supercritical CO2 fluids, including the formation of aragonite and dissolution-reprecipitation of Ni phases Collectively, these results will improve fate and transport models for carbon storage in ultramafic rocks, increase understanding of new unconventional sources for critical minerals, and provide a foundation for future studies on CO2 enhanced mineral recovery (CO2-EMR).