Obruks, as giant collapse dolines caused by hypogenic karstification in central Anatolia, Turkey: Analysis of likely formation processes

Understanding the development of collapse dolines is crucially important because sudden formation of these landforms threatens property and life. Obruks are mega collapse dolines developed in the lacustrine Neogene carbonates of the Konya Closed Basin in central Turkey. These landforms with diameters and depths reaching several hundreds of meters are characterized by their cylindrical or inverted truncated cone shaped surface morphology and contain lakes if they intersect the local water table. Evaluations based on geological, geophysical, hydrogeological data and the groundwater’s chemical and isotopic compositions suggest a hypogenic mechanism for the development of obruks. This process seems to be driven by the upward migration of a deep-seated carbon dioxide flux from an intrusive magmatic body. Presence of volcanogenic elements (i.e. Li and F) and remarkably high dissolved carbon dioxide (logPCO₂?=?10^?1 atm) in fresh groundwater, hydrothermal springs with elevated He contents (R/Ra?=?4.77), highly enriched carbon-13 isotopic composition of total dissolved inorganic carbon (¹³C_TDIC?=??1.12 ‰ V-PDB) in the regional groundwater and presence of widespread carbon dioxide discharges, constitute apparent evidence for the hypogenic fluid migration into the Neogene aquifer where enhanced dissolution due to mixing between the shallow-fresh and deep-saline groundwaters gives rise to obruk formation.     

Physical and numerical simulations of the presence of a forsterite transitional zone at high temperature and pressure: insight for scCO2 geological storage

Geological sequestration is one of the most effective ways to reduce greenhouse gases, such as carbon dioxide (CO₂). The deep oceanic crust dominated by ultrabasic rock could store CO₂ permanently. However, the storage mechanism has not been thoroughly understood because of the limited amount of research and experiments conducted. This study explored the reactive mechanisms of water–rock–gas in an ultrabasic system under different conditions. Forsterite, the most dominant mineral found in ultrabasic reservoirs, was used to conduct laboratory physical simulation experiments. Two experimental systems were designed including an scCO₂–forsterite–water system and an N₂–forsterite–water system. All experiments were performed for 1000 h at an experimental temperature of 150°C and a pressure of 150 bar, respectively, to mimic the geological conditions. The liquid products from the experiments were analysed by inductively coupled plasma-optical emission spectrometry, whereas the solid samples were analysed by scanning electron microscopy with energy disperse spectroscopy. Results showed that: (1) in the early stage during scCO₂/N₂–forsterite–water interaction, forsterite was dissolved with a reactive transitional zone forming on the surface, which caused H⁺ to enter into the silicate framework and accelerated the reaction; (2) in the N₂ system, the dissolution of forsterite was inhibited by the Mg²⁺ concentration after reaching its saturation in the late stage; and (3) in the scCO₂ system, magnesite was precipitated as a secondary mineral during the late stage, which promoted the dissolution of forsterite. As a result, the degree of dissolution of forsterite in the scCO₂ system was far higher than in the N₂ system. The experimental results are consistent with the numerical simulation using TOUGHREACT, a geochemical simulation procedure, which showed that CO₂ promotes the dissolution of forsterite greatly at high temperature and pressure.     

Convective mixing influenced by the capillary transition zone

Convective mixing of dissolved carbon dioxide (CO₂) with formation brine has been shown to be a significant factor for the rate of dissolution of CO₂ and thus for determining the viability of geological CO₂ storage sites. In most previous convection investigations, a no-flow boundary condition was used to represent the interface between an upper region with CO₂ and brine and the single-phase brine region beneath. However, due to interfacial tension between the phases, the water phase is partly mobile in the upper region and advection may occur. Based on linear stability analysis and numerical simulations, we show that advection across the interface leads to considerable destabilization of the system. In particular, the time of onset of instability is reduced by a factor of two and the rate of dissolution is enhanced by a factor of two for three of four formations we consider, and by 40 % for the fourth formation. It is found that exponential decay of the relative permeability away from the interface provides a useful approximation to the real system. In addition, the exponential decay also simplifies the linear stability analysis. Interestingly, formations with large absolute permeability and small porosity have the largest impact from the transition zone, despite the fact that the relative permeability decays quickly above the interface in these formations. This is because the length-scale of instability is smallest in these formations.     

CFD modeling of high-pressurized CO2 released from onshore pipeline leakages

Safe pipeline transportation of carbon dioxide is a critical issue in the developing field of carbon capture and storage technology. Inadequate fluid thermo- and regimes for on- and offshore transport through high-pressurized pipelines can induce pipe material obsolescence or even pipeline rupture. In such cases, CO₂ (Carbon dioxide) will be released and dispersed in the ambient medium. The dispersion is influenced by the total amount of released fluid, jet pressure and direction, the released concentrations, leakage hole size, ambient material properties and is also affected by the dynamical conditions of the environmental medium. The goal of this study is the hydrodynamical characterization of carbon dioxide jet expansion and dispersion in the ambient atmosphere in case of onshore pipeline accidental leaks. Numerical simulations were carried out by means of a 3D turbulent CFD (computational fluid dynamics) code which includes multi-component flow treatment. The influence of the jet release pressure and size of the leakage hole on harmful CO₂ concentration distances will be analyzed.     

Oxygen solubility and speciation in sulphide-rich mattes

Sulphide-rich liquids are common in magmatic environments forming over a wide range of temperature, pressure, fO₂ and fS₂. They are economically important because they sequester valuable metals such as Cu, Ni, Au and Pt from silicate melts. The presence of accessory amounts of primary oxides associated with sulphide mineralisations is often ignored or unexplained. Experimental work has shown that large amounts of oxygen can dissolve into mattes at fO₂ typical of terrestrial environments. At the quartz-fayalite-magnetite fO₂ buffer, the molar fraction of O in the matte exceeds that of S, placing the composition of the matte to the magnetite side of the mss (monosulphide solid solution)-magnetite join in the Fe-S-O system. However, sulphides crystallise before magnetite in most sulphide mineralisations and are much more abundant. Moreover, the speciation of O in a matte is not well known. Here we report the results of an experimental study of the solubility of O in mattes as a function of fS₂, fO₂, temperature, and composition. We confirm previous observations that Ni and Cu have a negative effect on the solubility of O in mattes. We show evidence for the existence of FeSO as a structural constituent of mattes in the Fe-S-O system. We present a simple parameterisation of the amount of O dissolved in mattes under relevant geological conditions, and use this parameterisation to discuss mechanisms for the crystallisation of primary spinels associated with sulphides in the Kambalda massive sulphide deposit (Western Australia) and the Sudbury Igneous Complex (Ontario, Canada).     

Solubility of CO2 in a Ca-rich leucitite: effects of pressure,temperature, and oxygen fugacity

The solubility of carbon dioxide in a Ca-rich leucitite has been investigated as a function of pressure (0.1–2.0 GPa), temperature (1200–1600°C), and oxygen fugacity. The experiments were done in a rapid-quench internally-heated pressure vessel (0.1 GPa) and a piston cylinder (0.5–2.0 GPa). The leucitite glass, previously equilibrated at NNO, and silver oxalate were loaded in Fe-doped Pt capsules (oxidized conditions) and graphitelined Pt capsules (reduced conditions). Secondary Ion Mass Spectrometry and bulk carbon analyses were used to determine the amount of dissolved carbon. Speciation of carbon was characterized by Fourier transform microinfrared spectroscopy. At oxidized conditions, only CO₃ ^2- is observed as a dissolved species. The solubility is high with CO₂ contents in the melt attaining 6.2 wt% at 2.0 GPa and 1350°C. The solubility increases with pressure and shows a significant negative temperature dependence. An excellent correlation is obtained when the data are fit to a model, based on the simplified solubility reaction CO₂ ^(vapor)+O^2-(melt)CO₃ ^2-(melt), which describes the solubility of CO₂ as a function of pressure, temperature and fCO₂. At reduced conditions, the amount of carbon dissolved is significantly lower, and CO₃ ^2- is still the only species present in the melt. If the solubility model established at oxidized conditions is applied, the carbon dissolved appears to be essentially a function of fCO₂ alone although divergence increases in a consistent manner with pressure and temperature. This could suggest a low but significant solubility of CO with a positive temperature dependence or a departure of the calculated fluid compositions determined by the equation of state from the actual ones. The strong preferential solubility of carbon in its oxidized C⁴⁺ form, even at reduced conditions, implies that ascending melts with high CO₂ solubility can experience significant oxidation through degassing. This could reconcile the oxidized nature of some Ca-rich alkaline magmas with more reduced mantle source regions.     

On the efficient estimation of small failure probability in slopes

The random finite element method (RFEM) combines the random field theory and finite element method in the framework of Monte Carlo simulation. It has been applied to a wide range of geotechnical problems such as slope stability, bearing capacity and the consolidation of soft soils. When the RFEM was first developed, direct Monte Carlo simulation was used. If the probability of failure (p _f ) is small, the direct Monte Carlo simulation requires a large number of simulations. Subset simulation is one of most efficient variance reduction techniques for the simulation of small p _f . It has been recently proposed to use subset simulation instead of direct Monte Carlo simulation in RFEM. It is noted, however, that subset simulation requires calculation of the factor of safety (FS), while direct Monte Carlo requires only the examination of failure or non-failure. The search for the FS in RFEM could be a tedious task. For example, the search for the FS of slope stability by the strength reduction method (SRM) usually requires much more computational time than a failure or non-failure checking. In this paper, the subset simulation is combined with RFEM, but the need for the search of FS is eliminated. The value of yield function in an elastoplastic finite element analysis is used to measure the safety margin instead of the FS. Numerical experiments show that the proposed approach gives the same level of accuracy as the traditional subset simulation based on FS, but the computational time is significantly reduced. Although only examples of slope stability are given, the proposed approach will generally work for other types of geotechnical applications.     

On persistent primary variables for numerical modeling of gas migration in a nuclear waste repository

Numerical simulation of gas migration driven by compressible two-phase partially miscible flow in porous media is of major importance for safety assessment of deep geological repositories for long-lived high-level nuclear waste. We present modeling of compositional liquid and gas flow for numerical simulations of hydrogen migration in deep geological radioactive waste repository based on persistent primary variables. Two-phase flow is considered, with incompressible liquid and compressible gas, which includes capillary effects, gas dissolution, and diffusivity. After discussing briefly the existing approaches to deal with phase appearance and disappearance problem, including a persistent set of variables already considered in a previous paper (Bourgeat et al., Comput Geosci 13(1):29–42, 2009), we focus on a new variant of the primary variables: dissolved hydrogen mass concentration and liquid pressure. This choice leads to a unique and consistent formulation in liquid saturated and unsaturated regions, which is well adapted to heterogeneous media. We use this new set of variable for numerical simulations and show computational evidences of its adequacy to simulate gas phase appearance and disappearance in different but typical situations for gas migration in an underground radioactive waste repository.     

Optimal use of a dome-shaped anticline structure for CO2 storage: a case study in the North German sedimentary basin

Structural traps like anticline structures are preferred for carbon dioxide sequestration as they limit lateral spreading of CO₂ and thus provide localized storage. This study, therefore, assesses strategies for maximizing storage of CO₂ using as hypothetical but realistic storage site a typical anticline structure in the North German sedimentary basin. Scenario simulations are performed to investigate the effects of well number, location, spacing and alignment, using fracture pressure and containment of CO₂ within the anticline as constraining factors. Scenarios are ranked by stored CO₂ mass, pressure increase due to injection and CO₂ immobilized by dissolution or residual trapping. It is found that pressure overlap from different injectors influences CO₂ migration considerably, limiting the storable amount to about 150 Mt, which represents half of the static capacity estimate.     

Thermal decomposition process in algaenan of Botryococcus braunii race L. Part 2: Molecular dynamics simulations using the ReaxFF reactive force field

This paper reports ReaxFF MD simulation results on pyrolysis of a molecular model of the algaenan Botryococcus braunii race L biopolymer, specifically, ReaxFF predictions on the pyrolysis of prototypical chemical structures involving aliphatic chain esters and aldehydes. These preliminary computational experiments are then used to analyze the thermal cracking process within algaenan race L biopolymers. The simulations indicate that the thermal decomposition of the algaenan biopolymer is initiated by the cleavage of a C–O bond in the ester group, followed by the release of carbon dioxide. We also observe a significant, strongly temperature dependent, release of ethylene. This degradation mechanism leads to products similar to those observed in pyrolysis experiments, validating this computational approach.     

Vanadium partitioning between orthopyroxene,spinel and silicate melt and the redox states of mantle source regions for primary magmas

The partitioning of V between orthopyroxene-liquid and spinel-liquid has been investigated in synthetic and natural mafic and ultramafic compositions as a function of temperature and oxygen fugacity (fO₂) at 100 kPa and in one experiment at higher pressure. The purpose of the experiments was to understand redox relationships for V in silicate melts with a view to deriving an empirical oxygen barometer for geochemically altered mafic and ultramafic magmas in the geologic record. Partitioning data for both orthopyroxene-liquid and spinel-liquid show profound changes at an fO₂ approximately 3 orders of magnitude below the nickel-nickel oxide (NNO) buffer, suggesting changes in the dominant valence state of V in silicate liquids from V³⁺ to V⁴⁺, near this fO₂.The results of the experiments on orthopyroxene-liquid are combined with published data for olivine-liquid and are applied to suites of mafic and ultramafic magmas that have equilibrated with a harzburgite residue in the mantle. The results show that Archean alumina-undepleted komatiites could have formed at fairly high oxygen fugacities, near ΔNNO ∼ 0, somewhat higher than Cretaceous komatiites and related picrites in the Caribbean region (between ΔNNO ∼ −1 to −3), and plume-related picrites from West Greenland (ΔNNO ∼ − 3). Picrites and boninites from convergent margins record the highest fO₂’s by this method, (ΔNNO = +1 to +2), consistent with other petrological estimates of their redox states. The approach developed in this study can thus provide estimates for the redox states of altered, mantle-derived magmas in the geological record, to which more conventional methods of oxygen barometry cannot be applied.     

Numerical simulation of the origin of red sandstone and Cu accumulation in pore solutions

Interaction of igneous rocks with river (rain) water in the systems granite-water, basalt-water, and dunite-water open with respect to carbon dioxide (PCO₂ = 10^?4, 10^?3, and 10^?2 bar) and oxygen (PO₂ from 10^?81 to 10^?1 bar) is numerically simulated at 25 and 50°C and a mass ratio of water and rock R/W ≤ 10. Equilibrium simulations indicate that, first, the differences in the mineralogical composition of the transformation products of the igneous rocks are insignificant, and second, Cu extraction from minerals of the rocks is optimal at Eh from +200 to ?100 mV. Simulations of the systems with regard for the dissolution rates of minerals indicate that the chemical weathering time of the rocks is few hundred thousands years.     

Determination of hydrogen ion concentration in softwater lakes using carbon dioxide equilibria

A strategy for determining the hydrogen ion content of fresh waters is proposed that involves total dissolved inorganic carbon (DIC or σCO₂) and CO₂ partial pressure (P_CO2) measurements rather than pH electrode measurements. This recommendation derives from discrepancies between pH and carbon dioxide equilibria measurements made on several softwater lakes at the Experimental Lakes Area, northwestern Ontario. The pH calculated from DIC, P_CO2, and the first dissociation constant of carbonic acid (K₁) data was consistently higher than that directly measured with a pH electrode. Similarly, calculation of P_CO2 of surface waters from pH, DIC, and K₁ data gave values up to twice that of atmospheric saturation despite repeated equilibrations with atmospheric P_CO2. Laboratory experiments demonstrated that the high dissolved organic carbon content of these waters appears to alter the electrode response yielding pH values lower than the true values. Furthermore, the uptake of protons by weak organic acid anions appear to be the cause of the measured difference between total (Gran) and carbonate (DIC — dissolved CO₂) alkalinity. Therefore bicarbonate ion concentration must be calculated from the difference between the total dissolved inorganic carbon content and uncharged dissolved CO₂ content. These procedures should provide more accurate and consistent results in the pH trend in surface waters and hence yield a solid baseline against which the effects of acid precipitation can be assessed.     

Quantification of photosynthetic inorganic carbon utilisation via a bidirectional stable carbon isotope tracer

The amount of bicarbonate utilised by plants is usually ignored because of limited measurement methods. Accordingly, this study quantified the photosynthetic assimilation of inorganic carbon (CO₂ and HCO₃ ^?) by plants. The net photosynthetic CO₂ assimilation (P _N), the photosynthetic assimilation of CO₂ and bicarbonate (P _N’), the proportion of increased leaf area (f _LA) and the stable carbon isotope composition (δ¹³C) of Orychophragmus violaceus (Ov) and Brassica juncea (Bj) under three bicarbonate levels (5, 10 and 15 mm NaHCO₃) were examined to determine the relationship among P _N, P _N’ and f _LA. P _N’, not P _N, changed synchronously with f _LA. Moreover, the proportions of exogenous bicarbonate and total bicarbonate (including exogenous bicarbonate and dissolved CO₂-generated bicarbonate) utilised by Ov were 2.27 % and 5.28 % at 5 mm bicarbonate, 7.06 % and 13.28 % at 10 mm bicarbonate, and 8.55 % and 17.31 % at 15 mm bicarbonate, respectively. Meanwhile, the proportions of exogenous bicarbonate and total bicarbonate utilised by Bj were 1.77 % and 3.28 % at 5 mm bicarbonate, 2.11 % and 3.10 % at 10 mm bicarbonate, and 2.36 % and 3.09 % at 15 mm bicarbonate, respectively. Therefore, the dissolved CO₂-generated bicarbonate and exogenous bicarbonate are important sources of inorganic carbon for plants.     

CO2 geological storage: The environmental mineralogy perspective

Geological storage of carbon dioxide (CO₂) is one of the options envisaged for mitigating the environmental consequences of anthropogenic CO₂ increases in the atmosphere. The general principle is to capture carbon dioxide at the exhaust of power plants and then to inject the compressed fluid into deep geological formations. Before implementation over large scales, it is necessary to assess the efficiency of the process and its environmental consequences. The goal of this paper is to discuss some environmental mineralogy research perspectives raised by CO₂ geological storage.     

The role of near-surface cavities in the carbon dioxide cycle of karst areas: evidence from the Carburangeli Cave Natural Reserve (Italy)

Hydrological, chemical and meteorological data collected during the years 2006–2007 at Carburangeli Cave (Italy) have provided new insights on the near-surface cycle of carbon dioxide, particularly concerning the role played by fractures and karst conduits. Carbon dioxide is trapped in the underground atmosphere essentially when its temperature is lower than the outer one. By contrast, convective air circulation disperses all the excess CO₂ in the external environment when the thermal differential is inverted. The network of fractures and karst conduits then works, in the vadose zone, as a re-circulator of CO₂ from the soil to the atmosphere. The total amount of CO₂ fixed in the underground is controlled, during the wet season, by the amount of infiltrating waters, which act as the main carrier of CO₂ in the subsoil. By contrast, during the dry season, gravitational drainage is responsible for the accumulation of carbon dioxide in the underground voids. The quantitative balance demonstrated that the degassed CO₂ amounts are one order of magnitude higher than the dissolved CO₂. In light of this, if the near-surface outgassing processes are not taken into account, CO₂ budgets may be affected by significant errors.     

Solution behavior of C-O-H volatiles in FeO-Na2O-Al2O3-SiO2 melts in equilibrium with liquid iron alloy and graphite at 4 GPa and 1550°C

In order to elucidate the solution behavior of carbon and hydrogen in iron-bearing magmatic melts in equilibrium with a metallic iron phase and graphite at oxygen fugacity (fO₂) values 2–5 orders of magnitude below the iron-wustite buffer equilibrium, fO₂ (IW), experiments were carried out at 4 GPa and 1550°C with melts of FeO-Na₂O-SiO₂-Al₂O₃ compositions. Melt reduction in response to an fO₂ decrease was accompanied by a decrease in FeO content. The values of fO₂ in the experiments were determined on the basis of equilibrium between Fe-C-Si alloy and silicate liquid. Infrared and Raman spectroscopy showed that carbon compounds are formed in FeO-Na₂O-SiO₂-Al₂O₃ melts: CH₄ molecules, CH₃ complexes (Si-O-CH₃), and complexes with double C=O bonds. The content of CO₂ molecules and carbonate ions (CO ₃ ^2? ) is very low. In addition to carbon-bearing compounds, dissolved hydrogen occurs in melt as H₂ and H₂O molecules and OH^? groups. The spectral characteristics of FeO-Na₂O-SiO₂-Al₂O₃ glasses indicate the occurrence of redox reactions in the melt, which are accompanied at decreasing fO₂ by a significant decrease in H₂O and OH^?, a slight decrease in H₂, and a significant concomitant increase in CH₄ content. The content of species with the double C=O bond increases considerably at decreasing fO₂ and reaches a maximum at ΔlogfO₂(IW) = ?3. According to the obtained IR spectra, the total water content (OH^? + H₂O) in the glasses is 1.2–5.8 wt % and decreases with decreasing fO₂. The high H₂O contents are due largely to oxygen release related to FeO reduction in the melt. The total carbon content at high H₂O (4.9–5.8 wt %) is approximately 0.4 wt %. The carbon content in liquid iron alloys depends on silicon content and, probably, oxygen solubility and ranges from 0.3 to 3.65 wt %. Low carbon contents were observed at a significant increase in Si content in liquid iron alloy, which may be as high as ～13 wt % at fO₂ values 4–5 orders of magnitude below fO₂(IW).     

Oxygen fugacity regime in the upper mantle as a reflection of the chemical differentiation of planetary materials

Oxygen fugacity (fO₂) in the Earth’s mantle has a bearing on the problems of the chemical differentiation of the Earth’s materials and formation of the chemical and phase state of its shells. This paper addresses some problems concerning changes in the redox state of the upper mantle over geologic time and through its depth and the possible influence of fO₂ stratification in the interiors on geochemical processes. Among these problems are the formation of fluids enriched in H₂O, CO₂, CH₄,and H₂; the possible influence of reduced fluid migration from mantle zones with low fO₂ values on reactions in the lithosphere; and the formation of films of silicate liquids with high H₂O and CO₂ contents, which could be responsible for metasomatic transformations in rocks. The formation of a metallic core and accompanying large-scale melting of the silicate part of the Earth are the early mechanisms of the chemical differentiation of the mantle that must have had an effect on the redox state and the composition of volatile components in planetary materials. The molten metallic and silicate phases were prone to gravitational migration, which affected the formation of the metallic core. Volatile components had to be simultaneously formed in the zones of large-scale melting of the early Earth. The composition of these volatiles was largely controlled by the interaction of hydrogen and carbon, the two major gas-forming elements in the mantle, with melt under low fO₂ values. A remarkable feature is that, despite fairly low fO₂ values imposed by the presence of a metallic phase, both reduced (CH₄ and H₂) and oxidized species of hydrogen and carbon (H₂O, OH^? and CO ₃ ^?2 ) are stable in the melt. This peculiarity of carbon and hydrogen dissolution in reduced melts may be crucial for the elucidation of mechanisms for the formation of initial amounts of CO₂ and H₂O connected with incipient melting in the reduced mantle.     

Determination of carbon dioxide solubility in oil during interaction with a compound gaseous phase

A thermodynamic method for the determination of the solubility of a mixture of carbon dioxide and hydrocarbon gases in oil is elaborated on the basis of stage-oil separation. A method for the calculation of Henry’s constants for gases that are dissolved in oil and their temperature extrapolation are shown. Effective thermodynamic properties are estimated for carbon dioxide and C₁–C₈ hydrocarbon gases dissolved in oil. A thermodynamic model that satisfactorily describes the separation of gas from oil is created and may be included in a more complex calculation model of carbonate scaling during the exploitation of oil deposits.     

On type B CAI formation: experimental constraints on fO2 variations in spinel minor element partitioning and reequilibration effects

We report data from a series of dynamic crystallization experiments that focus on determining the partition coefficients (D’s) for V and Ti in the spinel + liquid system of an average type B1 CAI bulk composition for three different fO₂ conditions. Partitioning data for Ca and Si are also obtained. We show that the D’s for V and Ti are fO₂ dependent with D_Ti decreasing at low oxygen fugacity due to the presence of Ti³⁺. D_V is essentially 0 in air, rises to 2.2 at the Fe-FeO buffer and drops to 1.4 at the C-CO buffer. This indicates that V³⁺ is highly compatible in spinel and that higher and lower valence states are much less compatible. We also report data from isothermal experiments that determine diffusion times for V and Ti in same system at a temperature close to the T_max for type B1 CAIs. Diffusion of these elements between spinel and liquid is surprisingly rapid, with essentially total equilibration of Ti and V between spinel and liquid in 90 h run duration. Lack of equilibration of Cr, Si, and Ca shows that the Ti and V equilibration mechanism was diffusion and not dissolution and reprecipitation. Our experimental run durations set an upper limit of a few tens of hours on the time that type B1 CAIs were at their maximum temperature. Based on our data we argue that subsolidus reequilibration between spinel inclusion and host-silicate phases within type B CAIs likely explains the observed range of V and Ti concentrations in spinels which are inclusions in clinopyroxene.