Crystal Interiors Research Articles

The Molecular Nature of Redox-Conductive Metal-Organic Frameworks.

ConspectusRedox-conductive metal-organic frameworks (RC-MOFs) are a class of porous materials that exhibit electrical conductivity through a chain of self-exchange reactions between molecularly defined, neighboring redox-active units of differing oxidation states. To maintain electroneutrality, this electron hopping transport is coupled to the translocation of charge balancing counterions. Owing to the molecular nature of the redox active components, RC-MOFs have received increasing attention for potential applications in energy storage, electrocatalysis, reconfigurable electronics, etc. While our understanding of fundamental aspects that govern electron hopping transport in RC-MOFs has improved during the past decade, certain fundamental aspects such as questions that arise from the coupling between electron hopping and diffusion migration of charge balancing counterions are still not fully understood.In this Account, we summarize and discuss our group's efforts to answer some of these fundamental questions while also demonstrating the applicability of RC-MOFs in energy-related applications. First, we introduce general design strategies for RC-MOFs, fundamentals that govern their charge transport properties, and experimental diagnostics that allow for their identification. Selected examples with redox-active organic linkers or metallo-linkers are discussed to demonstrate how the molecular characteristics of the redox-active units inside RC-MOFs are retained. Second, we summarize experimental techniques that can be used to characterize charge transport properties in a RC-MOF. The apparent electron diffusion coefficient, Deapp, that is frequently determined in the field and obtained in large perturbation, transient experiments will be discussed and related to redox conductivity, σ, that is obtained in a steady state setup. It will be shown that both MOF-intrinsic (topology, pore size, and apertures) and experimental (nature of electrolyte, solvent) factors can have noticeable impact on electrical conductivity through RC-MOFs. Lastly, we summarize our progress in utilizing RC-MOFs as electrochromic materials, materials for harvesting minority carriers from illuminated semiconductors and within electrocatalysis. In the latter case, recent work on multivariate RC-MOFs in which redox active linkers are used to "wire" redox catalysts in the crystal interiors will be presented, offering opportunities to independently optimize charge transport and catalytic function.The ambition of this Account is to inspire the design of new RC-MOF systems, to aid their identification, to provide mechanistic insights into the governing ion-coupled electron hopping transport mode of conductivity, and ultimately to promote their applications in existing and emerging areas. With basically unlimited possibilities of molecular engineering tools, together with research in both fundamental and applied fields, we believe that RC-MOFs will attract even more attention in the future to unlock their full potential.

The evolution of Archean crust undisturbed for three billion years: A case study from the Bahalda Pluton, Singhbhum Craton, eastern India

The Archean Bahalda Pluton (Singhbhum Craton, eastern India) is an I-type mafic granodiorite, surrounded by Paleoarchean TTG and TTG-derived granites of the Singhbhum Suite. The Singhbhum Suite is highly unusual amongst Eo- and Paleo-Archean terranes because most of the Singhbhum Craton escaped post-Archean deformation and metamorphism. The Bahalda granodiorite contains accessory zircon, titanite, and fluorapatite, which are rarely studied together but are a powerful tool for exploring magmatic and post-magmatic processes. U-Pb zircon and titanite dating indicate a ca. 3.35 Ga emplacement age of the Bahalda granodiorite. Subsequent ca. 3.27–3.05 Ga U-Pb fluorapatite ages are interpreted as recording low-grade metamorphic or hydrothermal event(s). The Bahalda fluorapatite and titanite are LREE-enriched compared to the HREE. The complex zonation of fluorapatite suggests that primary igneous fluorapatite was recrystallised with the removal of REE and overgrown by REE-depleted rims. This is in agreement with the apatite trace element systematics which imply fluorapatite cores are of mafic I-type granitoid affinity, with rims of low- and medium-grade metamorphic / metasomatic affinity. No textural evidence of titanite alteration was detected, but some domains have minor REE depletion compared to crystal interiors. The titanite and fluorapatite data display similar trends in LREE vs Sr/Y space due to metamorphic/hydrothermal alteration. The evolution of the Bahalda Pluton, which did not exceed greenschist facies for 3 Gyr, invites comparison with other stabilized cratons from the Mesoarchean.

Chemical abrasion: the mechanics of zircon dissolution

Abstract. Chemical abrasion is a technique that combines thermal annealing and partial dissolution in hydrofluoric acid (HF) to selectively remove radiation-damaged portions of zircon crystals prior to U–Pb isotopic analysis, and it is applied ubiquitously to zircon prior to U–Pb isotope dilution thermal ionization mass spectrometry (ID-TIMS). The mechanics of zircon dissolution in HF and the impact of different leaching conditions on the zircon structure, however, are poorly resolved. We present a microstructural investigation that integrates microscale X-ray computed tomography (µCT), scanning electron microscopy, and Raman spectroscopy to evaluate zircon dissolution in HF. We show that µCT is an effective tool for imaging metamictization and complex dissolution networks in three dimensions. Acid frequently reaches crystal interiors via fractures spatially associated with radiation damage zoning and inclusions to dissolve soluble high-U zones, some inclusions, and material around fractures, leaving behind a more crystalline zircon residue. Other acid paths to crystal cores include the dissolution of surface-reaching inclusions and the percolation of acid across zones with high defect densities. In highly crystalline samples dissolution is crystallographically controlled with dissolution proceeding almost exclusively along the c axis. Increasing the leaching temperature from 180 to 210 ∘C results in deeper etching textures, wider acid paths, more complex internal dissolution networks, and greater volume losses. How a grain dissolves strongly depends on its initial radiation damage content and defect distribution as well as the size and position of inclusions. As such, the effectiveness of any chemical abrasion protocol for ID-TIMS U–Pb geochronology is likely sample-dependent. We also briefly discuss the implications of our findings for deep-time (U-Th)/He thermochronology.

Ultrasensitive Photodetectors Based on Strongly Interacted Layered-Perovskite Nanowires.

Metal-halide layered perovskites, self-assembled quantum wells with alternating insulating interlayer organic cations, and conductive perovskite layers boost the incorporation of multiple functionalities into a single-phase material. Optoelectronic performances in layered perovskites are more sensitive to crystallinity than their 3D counterparts due to the traps and insulating barriers introduced by interlayer cations. Here, we combine the capillary-bridge lithography method for the fabrication of single-crystalline nanowire arrays with strongly interacted layered perovskites for the enhancement of crystallinity and crystallographic orientation purity. Due to regulated nucleation and growth of layered perovskites in capillary bridges and the sulfur-sulfur interaction between interlayer cations, nanowires with pure (101) orientation are realized for underpinning insulating crystal interiors and photoconductive layer edges. Based on these nanowires, ultrasensitive photodetectors are reached with an ultralow dark current of below 10-12 A, an average responsivity of 7.3 × 103 A W-1, an average specific detectivity of 3.9 × 1015 Jones, and a 3 dB bandwidth of 10.3 kHz.

Metamictization and fluid-driven alteration triggering massive HFSE and REE mobilization from zircon and titanite: Direct evidence from EMPA imaging and LA-ICP-MS analyses

The major and trace element composition of the main HFSE-bearing phases from highly evolved miaskitic syenites has been investigated to assess their stability, an important control on HFSE retention and mobility during post-magmatic hydrothermal activity. The major HFSE carrier, abundant zircon (up to 5 vol%), has undergone intensive metamictization, caused by high initial U and Th along with the presence of early magmatic U-thorite inclusions. Subsequent to metamictization, zircon experienced pervasive fluid-driven alteration, as evidenced by strong depletion in Zr and Si, enrichment in non-formula elements (Ca, Fe, Al, P), deficient EMPA analytical totals, high porosity, and low BSE-intensities of strongly altered crystal interiors. Element maps suggest that extensive HFSE remobilization from altered zircon was controlled by interaction with oxidized aqueous solutions circulating through abundant microfractures that formed by volume expansion due to zircon metamictization. Enhanced HFSE mobility in hydrothermal fluids is reflected by the presence of a hydrated amorphous Zr-Th-U-Si-phase, filling microveinlets intimately associated with metamict zircons. In addition to HFSE remobilization from altered zircon, titanite released a significant amount of REE during interaction with the hydrothermal fluids that concurrently caused a fractionation of Eu in titanite, producing increased EuN/EuN* (4.16–22.2) in altered crystals. Extensively altered titanite grains with elevated EuN/EuN* are considerably depleted in ∑REE + Y compared to unaffected crystals, showing that degree of positive Eu anomalies, relating to post-magmatic metasomatic overprint, appears to be a sensitive indicator for an intensity of hydrothermal alteration and even the total amount of released incompatible elements. Pronounced LREE enrichment accompanied by HREE depletion in the strongly altered crystals indicates greater LREE retention in titanite and higher HREE mobility in the hydrothermal system probably caused by complexing with fluoride ligands. Fluorine was most likely supplied through amphibole and biotite chloritization, as suggested by notably low F in the mafic silicates along with the formation of secondary F-rich titanite at the expense of altered biotite. Moreover, the dissolution of zircon and titanite and resistance of apatite to pervasive alteration indicates that remobilization of HFSE and REE from these phases occurred under alkaline conditions (pH 8–12), presumably controlled by potassium-dominated complexes transporting HFSE along with REE over long distances, as indicated by a close spatial linkage of syenite outcrops with U-mineralization. Our results clearly demonstrate: (1) extensive chemical dissolution of zircon controlled by its self-induced radiation damage; (2) high solubility of titanite and metamict zircon under alkaline conditions; (3) enhanced mobility and long-distance transport of HFSE and REE in alkali- and F-rich hydrothermal systems.

The Origin of Rhyolitic Magmas at Krafla Central Volcano (Iceland)

AbstractWe present a detailed petrologic study of rhyolites from seven eruptions spanning the full (∼190 ky) history of rhyolitic volcanism at Krafla volcano, northeast Iceland. The eruptions vary widely in size and style, but all rhyolites are crystal-poor (<6 modal%: plagioclase + augite ± pigeonite ± orthopyroxene ± titanomagnetite ± fayalite) and have similar evolved compositions (73.7–75.8 wt% normalized whole-rock SiO2) and trace element patterns. Macrocryst rim compositions from each eruption cluster within a narrow range and are appropriate for equilibrium with their carrier melt. Crystal cores and interiors display complex growth patterns and commonly host resorption surfaces, but compositional variations are slight (e.g. typically <10 mol% An for plagioclase, Mg# <10 for pyroxene), and consistent with an overall trend of cooling and differentiation by crystal fractionation. Although most crystal core and interior compositions are broadly appropriate for equilibrium with melts similar to their host whole-rock, variable growth histories, juxtaposition of grains with distinct trace element compositions, and scatter in melt inclusion compositions indicate mixing of antecrysts from compositionally similar evolved melts and/or assimilated felsic mush or intrusions before final rim growth. Evidence for mafic recharge (e.g. coupled increases in An and Fe in plagioclase) is absent in most crystals; rhyolite storage and fractionation thus occurred largely in isolation from the underlying mafic system. Comparison of observed matrix glass compositions with published experimental work on melting of altered (meta)basalts casts doubt on previous models favouring rhyolite generation by partial melting of hydrothermally altered basalts, instead supporting recent isotopic and modelling arguments for a crystallization-driven process [Hampton, R. L. et al. (2021). Journal of Volcanology and Geothermal Research 414, 107229]. MELTS fractional crystallization and assimilation-fractional crystallization (AFC) models at 1 kbar predict liquid major and trace element compositions similar to Krafla rhyolites after ∼60–70 vol% crystallization of a quartz tholeiite melt representative of the evolved crystal-poor basalts commonly erupted within Krafla caldera. We thus suggest that stalling and crystallization of these evolved basalts at shallow depth forms crystal mushes from which evolved (broadly dacitic to rhyolitic) melts are extracted. These melts ascend and mix with other compositionally similar melt bodies and/or assimilate felsic intrusive material in the uppermost crust. The Daly gap between ∼57 and 71 wt% SiO2 at Krafla is consistent with preferential extraction of evolved melts from quartz tholeiite mushes in the ∼50–70% crystallinity window. Residual solid (cumulate) compositions predicted by MELTS are exclusively mafic, hence efficient silicic melt extraction from quartz tholeiite mushes may also explain the apparent compositional bimodality in some Icelandic plutonic suites.

Zircon geochronology suggests a long-living and active magmatic system beneath the Ciomadul volcanic dome field (eastern-central Europe)

Ciomadul is the youngest volcano in eastern-central Europe. Although its last eruption occurred at ca. 30 ka, there are independent indications for a high-crystallinity magma reservoir persisting beneath the volcano until present. In order to further test the hypothesis of long-lived melt presence and to better constrain the nature and timescales associated with the subvolcanic magma storage system, over 500 zircon U-Th and U-Pb spot ages (crystal interiors and outer surfaces) were interpreted from dacitic rocks of the most productive eruptive period (the Young Ciomadul Eruptive Period; YCEP, 160-30 ka). Zircon surface ages from lava dome and pumice samples range from ca. 600 ka up to the youngest eruption event at 30 ka. They form a continuous age distribution and some single crystals reveal significant age zonation (>150 kyr difference from core to rim). The oldest zircon ages of YCEP overlap with the last eruption events of the Old Ciomadul Eruptive Period (1000–330 ka). The zircon age spectra, combined with textural data, point to a prolonged (several 100's kyr) residence in a highly crystalline mush state. The range in zircon crystallization temperature (from ∼750°C to the solidus at ∼680°C) is consistent with the results of thermometry on amphibole and plagioclase from felsic crystal clots, which represent crystal mush fragments. To maintain magma reservoir for such a long time above solidus, continuous magma input by deeper recharge is required. Zircon crystallization model calculations constrained by thermal modelling imply an average rate of magma input of about 1.3 × 10−4 km3/yr over 2 Myr. Such estimate allows us to calculate an extrusive/intrusive ratio of 1:25–1:30. The model calculations suggest that a crystal mush zone of about 35 km3 is still present within the subvolcanic magma reservoir. Importantly, the Ciomadul plumbing system thus remains thermally primed and renewed magma injection could lead to rapid reawakening and eruption of the apparently inactive volcano.

Repeated Rhyolite Eruption From Heterogeneous Hot Zones Embedded Within a Cool, Shallow Magma Reservoir

AbstractDespite the hazard posed by explosive silicic eruptions, the magma storage conditions and dynamics that precede these events remain controversial. The Laguna del Maule volcanic field, central Chile, is an exceptional example of postglacial (younger than ca. 20,000 years) rhyolite volcanism and sustained unrest driven by a large, shallow, active silicic magma system. New zircon petrochronologic data reveal that compositionally distinct domains developed concurrently within the Laguna del Maule magma reservoir, which produced two episodes of concentrated rhyolitic eruptions at 23–19 and 8–2 ka. Zircon crystallization ages record 160 kyr of magma emplacement resulting in a several hundreds of cubic kilometers reservoir that has been imaged geophysically. The average magma emplacement rate inferred from the zircon geochronology and tomographically defined magma volume is consistent with those required by thermal models to maintain a shallow silicic system. Ti‐in‐zircon temperatures of crystal cores and rims and hiatuses in crystal growth indicates most of this volume persisted in a near‐solidus state. However, consistent patterns of trace element zoning in crystal interiors and crystallization rates derived from a model of diffusion‐limited zircon growth suggest the erupted rhyolite magma batches originated from long‐lived hot zones of extractable mush embedded within the larger, cool reservoir of rigid mush. These contrasting, coeval magma storage conditions obviate a simple hot versus cold storage dichotomy for large silicic magma systems.

Computational analysis of mesoscale thermomechanical ignition behavior of impacted LLM-105 based explosives.

LLM-105 (2,6-diamino-3,5-dinitropyrazine-1-oxide) is an insensitive high explosive crystal which has performance between that of HMX and TATB. An elastoviscoplastic dislocation model is developed for LLM-105 crystal, which accounts for the dislocation evolutions at the crystal interior and crystal wall and strain-rate dependent work hardening. Three different crystal morphology (cubic, icosahedral, rodlike) of LLM-105 based explosive computational models were constructed and subjected to an impact velocity of 200 m s−1 and 500 m s−1. Effects of crystal morphology and initial dislocation density on thermomechanical ignition behavior of LLM-105 based explosives were analyzed. Dislocation density of both crystal interiors and crystal walls in the rodlike LLM-105 based explosive increases slower than that in the cubic and icosahedral explosives. Both the volume averaged and localized stress and dislocation density are the lowest for the rodlike explosive. At the impact velocity of 500 m s−1, a temperature rise due to volumetric work, plasticity work and chemical reaction is sufficiently high to lead to the ignition of the cubic explosive, which shows that the rodlike explosive is the least sensitive among the three explosives. Moreover, with the increase of initial dislocation density, the corresponding volume averaged and localized stress and temperature increase as well. Results presented bridge the macroscale thermomechanical ignition response with the mesoscale deformation mechanisms, which is essential for better understanding the ignition mechanisms and guiding the design of LLM-105 based formulations.

Extra strengthening and work hardening in gradient nanotwinned metals.

Gradient structures exist ubiquitously in nature and are increasingly being introduced in engineering. However, understanding structural gradient-related mechanical behaviors in all gradient structures, including those in engineering materials, has been challenging. We explored the mechanical performance of a gradient nanotwinned structure with highly tunable structural gradients in pure copper. A large structural gradient allows for superior work hardening and strength that can exceed those of the strongest component of the gradient structure. We found through systematic experiments and atomistic simulations that this unusual behavior is afforded by a unique patterning of ultrahigh densities of dislocations in the grain interiors. These observations not only shed light on gradient structures, but may also indicate a promising route for improving the mechanical properties of materials through gradient design.

Stronger copper through twin power

Metallurgy Materials with structural gradients often have unique combinations of properties. Gradient-structured materials are found in nature and can be engineered. Cheng et al. made a structural gradient by introducing gradients of crystallographic twins into copper. This strategy creates bundles of dislocations in the crystal interiors, which makes the metal stronger than any of the individual components. This method offers promise for developing high-performance metals. Science , this issue p. [eaau1925][1] [1]: /lookup/doi/10.1126/science.aau1925

Growth and comparison of single crystals and polycrystalline brownmillerite Ca2Fe2O5

Brownmillerite Ca2Fe2O5 is a mixed ionic electronic material with interesting electrical properties. In this report, the properties of Ca2Fe2O5 single crystals are compared with bulk polycrystalline Ca2Fe2O5 samples. Powder X-ray diffraction (PXRD), Scanning electron microscopy, Optical microscopy and Energy dispersive X-ray spectroscopy (EDX) have been performed on the as prepared samples. XPS full survey spectra confirm the presence of constituent elements and reveal the peak binding energy of calcium, iron and oxygen. EDX was also used to trace the distribution of constituent elements. Images of crystal surfaces and interiors by polarized optical microscopy have been presented.

Deciphering magmatic processes in calc-alkaline plutons using trace element zoning in hornblende

Hornblende in the Kuna Crest lobe (KCL) of the Tuolumne Intrusive Complex (TIC) and the upper zone of the Wooley Creek batholith (WCB) precipitated over a temperature range of ~835 to 700 °C, and thus has the potential to record magmatic processes. We measured trace element concentrations in hornblende from the WCB, from the KCL of the TIC, and from one sample from an adjacent interior unit of the TIC to compare and contrast magmatic processes in these two mid-crustal intrusions. In both systems the magmatic amphibole is magnesiohornblende in which Ti, Zr, Hf, Nb, Sr, Ba, and rare earth elements (REE) typically decrease from crystal interiors to rims, an indication of compatible behavior of these elements, and the size of the negative Eu anomaly decreases. In the Kuna Crest lobe, hornblende from individual mapped units differs in trace element abundances and zoning trends. Some samples contain at least two distinct hornblende populations, which is particularly evident in the shapes of REE patterns. In contrast, compositions of hornblende from all structural levels of the upper WCB and related dacitic roof-zone dikes form a single broad array and the REE patterns are essentially indistinguishable, regardless of rock type, from quartz diorite to granite. In the WCB, Zr/Hf ratios in hornblende are consistent with crystallization from a melt with chondritic Zr/Hf values. In contrast, most hornblende in the KCL has Zr/Hf values lower than expected from crystallization from a melt with chondritic values, suggesting that zircon fractionation occurred before and during crystallization of the hornblende. Simple fractional crystallization models indicate that REE, high field strength elements, Sr, and Ba were compatible in KCL and WCB magmas as hornblende grew; these trends require removal of hornblende + plagioclase + zircon ± ilmenite ± biotite. The uniform variations of trace element concentrations and patterns in the upper WCB and roof-zone dikes indicates crystallization from a large magma body that was compositionally uniform; probably stirred by convection caused by influx of mafic magmas at the base of the zone (Coint et al. 2013a, 2013b; cf. Burgisser and Bergantz 2011). In contrast, in the KCL, each analyzed sample displays distinct hornblende compositions and zoning patterns, some of which are bimodal. These features indicate that each analyzed sample represents a distinct magma and that individual magmas were variably modified by fractionation and mixing. Hornblende trace element contents and zoning patterns prove to be powerful tools for identification of magma batches and for assessing magmatic processes, and thereby relating plutonic rocks to hypabyssal and volcanic equivalents.

Zircon U–Pb and trace element zoning characteristics in an anatectic granulite domain: Insights from LASS-ICP-MS depth profiling

Understanding the geochemical characteristics of metamorphic zircon, and how they may be modified by recrystallization processes, is fundamental to defining the timescales of tectonic processes affecting continental lithosphere. We utilize laser ablation split-stream (LASS)-ICP-MS depth-profiling analysis to obtain a continuous rim-to-core record of the U–Pb ages and trace-element composition preserved within variably recrystallized zircon from different rock types within a well-studied granulite domain in the western Grenville Province, Canada. Detailed analysis of the depth-resolved signal enables definition of chemically distinct (homogeneous) internal domains and heterogeneous intervening zones that can generally be correlated with textural features observed in CL. Three age populations have been distinguished within the ~35μm deep profiles that correlate well with the established timing of protolith formation, granulite-facies metamorphism, and amphibolite-facies shearing, respectively. The U–Pb isotopic system and Th/U ratios in much of the crystal interiors have undergone considerable modification, as evidenced by a linear correlation between 207Pb/206Pb age and Th/U ratio. Interior and rim domains commonly contain blurred or faded oscillatory zoning patterns, suggesting that solid-state recrystallization is at least partially responsible for the modified U–Th–Pb composition. A number of systematic trends in trace element composition are also observed between interior domains and recrystallized rims, including 1) decreased Th/U (to ~0.1), 2) tighter clustering of Hf concentrations, 3) decreased total REE, 4) unchanged Eu anomalies, and 5) a widened spread of HREE enrichment values (YbN/GdN). Both YbN/GdN vs. Th/U and U/Ce vs. Th plots show increasing degree of compositional differentiation from protolith zircon as a function of metamorphic reworking processes (i.e. sample type). The transition zones between interior and rim domains exhibit textural features consistent with solid-state recrystallization and migration of a transgressive recrystallization front. The main compositional characteristics of the transition zones are 1) spikes in U and Ta, 2) steady to abrupt increases in Hf toward maximum values in the rims, 3) steady to abrupt decreases in Th toward minimum values in the rims, and 4) variable REE patterns that include spikes, troughs, and montonic decreases. Most of these characteristics are consistent with the purging of larger ions from the crystal lattice during recrystallization, with local bands of high concentration associated with recrystallization fronts.

Age of theLavaCreek supereruption and magma chamber assembly at Yellowstone based on40Ar/39Ar andU‐Pb dating of sanidine and zircon crystals

AbstractThe last supereruption from the Yellowstone Plateau formed Yellowstone caldera and ejected the >1000 km3of rhyolite that composes the Lava Creek Tuff. Tephra from the Lava Creek eruption is a key Quaternary chronostratigraphic marker, in particular for dating the deposition of mid Pleistocene glacial and pluvial deposits in western North America. To resolve the timing of eruption and crystallization history for the Lava Creek magma, we performed (1)40Ar/39Ar dating of single sanidine crystals to delimit eruption age and (2) ion microprobe U‐Pb and trace‐element analyses of the crystal faces and interiors of single zircons to date the interval of zircon crystallization and characterize magmatic evolution. Sanidines from the two informal members composing Lava Creek Tuff yield a preferred40Ar/39Ar isochron date of 631.3 ± 4.3 ka. Crystal faces on zircons from both members yield a weighted mean206Pb/238U date of 626.5 ± 5.8 ka, and have trace element concentrations that vary with the eruptive stratigraphy. Zircon interiors yield a mean206Pb/238U date of 659.8 ± 5.5 ka, and reveal reverse and/or oscillatory zoning of trace element concentrations, with many crystals containing high U concentration cores that likely grew from highly evolved melt. The occurrence of distal Lava Creek tephra in stratigraphic sequences marking the Marine Isotope Stage 16–15 transition supports the apparent eruption age of ∼631 ka. The combined results reveal that Lava Creek zircons record episodic heating, renewed crystallization, and an overall up‐temperature evolution for Yellowstone's subvolcanic reservoir in the 103−104year interval before eruption.

Sulfur evolution of the 1991 Pinatubo magmas based on apatite

Using electron microprobe (EMP) and laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to collect major and rare-earth elements (REE), respectively, from apatites from the 1991 Mt. Pinatubo juvenile eruption products, we have determined that two statistically distinct populations of apatite exist. One population crystallized from the juvenile basaltic melt (basalt apatites) and the other population crystallized from the main dacitic magma body (silicic apatites). Both populations contain high-S apatites (>0.7wt.% SO3). Apatite has previously been shown to be a potential monitor for magmatic sulfur contents via numerous proposed coupled substitutions of P5+ for S6+. However, simple apatite/melt partitioning cannot account for high-S silicic apatites, which grew from a silicic melt with an apparent maximum S concentration of ~80ppm. Disparate apatite morphology (i.e. skeletal and acicular for basalt apatites and euhedral for silicic apatites) as well as compositional evidence reveal that high-S silicic apatites were not inherited from the juvenile basalt during mingling/mixing prior to eruption. Sulfur gain from neighboring anhydrite phenocrysts can also be ruled-out as a source of high sulfur. EMP sulfur mapping of silicic apatites shows highly irregular patterns of sulfur enrichment that do not correspond with adjacent anhydrite and can be found within apatites hosted by other minerals (e.g. hornblende and Fe–Ti oxides). With these data in mind, we propose high-S silicic apatites from Pinatubo and other sulfur-rich systems achieved elevated sulfur concentrations during high sulfur fluxing events that originated from underplated basalt during degassing of a SO2-rich fluid phase. That basalts were indeed sulfur rich and oxidized is here indicated by high S contents of apatites growing in basalt. The predominant location of S-rich areas of silicic apatite is crystal interiors of apatite inclusions in other mineral phases, while large apatite microphenocrysts surrounded by groundmass glass have low sulfur contents. This is evidence for placing sulfur-fluxing periods long before events that ultimately led to the 1991 eruption.

Two diffusion pathways in quartz: A combined UV-laser and RBS study

The diffusive behavior of argon in quartz was investigated with three analytical depth profiling methods: Rutherford Backscattering Spectroscopy (RBS), 213 nm laser ablation, and 193 nm (Excimer) laser ablation on the same set of experimental samples. The integration of multiple depth profiling methods, each with different spatial resolution and sensitivity, allows for the cross-checking of methods where data ranges coincide. The use of multiple methods also allows for exploration of diffusive phenomena over multiple length-scales. Samples included both natural clear rock crystal quartz and synthetic citrine quartz. Laser analysis of clear quartz was compromised by poor coupling with the laser, whereas the citrine quartz was more easily analyzed (particularly with 193 nm laser). Diffusivity measured by both RBS and 193 nm laser ablation in the outermost 0.3 μm region of citrine quartz are self-consistent and in agreement with previously published RBS data on other quartz samples (including the clear quartz measured by RBS in this study). Apparent solubilities (extrapolated surface concentrations) for citrine quartz are in good agreement between RBS, 213 nm, and 193 nm laser analyses. Deeper penetration of argon measured up to 100 μm depth with the 213 nm laser reveal contributions of a second, faster diffusive pathway, effective in transporting much lower concentrations of argon into the crystal interiors of both clear and citrine quartz. By assuming such deep diffusion is dominated by fast pathways and approximating them as a network of planar features, the net diffusive uptake can be modeled and quantified with the Whipple–LeClaire equation, yielding δD b values of 1.32 × 10 −14 to 9.1 × 10 −17 cm 3/s. While solubility values from the measured profiles confirm suggestions that quartz has a large capacity for argon uptake (making it a potentially important sink for argon in the crust), the slow rate of lattice diffusion may limit its capability to take up argon in shorter lived geologic environments and in experiments. In such shorter-lived systems, bulk argon diffusive uptake will be dominated by the fast pathway and the quartz lattice (including natural isolated defects that may also be storing argon) may never reach its equilibrium capacity.

Episodic growth and homogenization of plutonic roots in arc volcanoes from combined U–Th and (U–Th)/He zircon dating

Tracing the fate of unerupted magma is challenging because plutonic roots of young volcanoes are largely inaccessible. Here we develop the use of zircon age spectra to determine crystal provenance and source rocks for volcanic products, in analogy to detrital crystals in sediments. U–Th zircon crystallization ages for the Soufrière Volcanic Complex, Saint Lucia (Lesser Antilles) frequently predate their eruption as determined from combined U–Th and (U–Th)/He zircon dating. The oldest dated eruptions are 273±15ka and 264±8ka (1σ uncertainty) for Morne Bonin dacite and Bellevue pumice deposit, respectively. The most recent eruptions formed morphologically pristine domes in the center of the Qualibou depression (Belfond: 13.6±0.4ka; Terre Blanche: 15.3±0.4ka). U–Th (U–Pb) zircon crystallization ages determined for crystal rims and interiors range between near-eruption ages to ∼600ka. Older xenocrysts are absent. Zircon crystallization age distributions are complex, yet systematic: crystal rim ages in the most recently erupted volcanic rocks match those of co-erupted plutonic inclusions, whereas crystal interiors are equivalent to the cumulative distribution of zircon ages from older eruptions. This is evidence that silicic lava domes and pyroclastic flows share a common source that is located underneath the Qualibou depression, where the intrusive roots of this long-lived arc volcanic system became homogenized through thermal and mechanical reprocessing of individual batches of unerupted magma from earlier volcanic episodes within timescales of <100ka.

Modulation of Calcium Oxalate Dihydrate Growth by Selective Crystal-face Binding of Phosphorylated Osteopontin and Polyaspartate Peptide Showing Occlusion by Sectoral (Compositional) Zoning

Calcium oxalate dihydrate (COD) mineral and the urinary protein osteopontin/uropontin (OPN) are commonly found in kidney stones. To investigate the effects of OPN on COD growth, COD crystals were grown with phosphorylated OPN or a polyaspartic acid-rich peptide of OPN (DDLDDDDD, poly-Asp(86-93)). Crystals grown with OPN showed increased dimensions of the {110} prismatic faces attributable to selective inhibition at this crystallographic face. At high concentrations of OPN, elongated crystals with dominant {110} faces were produced, often with intergrown, interpenetrating twin crystals. Poly-Asp(86-93) dose-dependently elongated crystal morphology along the {110} faces in a manner similar to OPN. In crystal growth studies using fluorescently tagged poly-Asp(86-93) followed by imaging of crystal interiors using confocal microscopy, sectoral (compositional) zoning in COD was observed resulting from selective binding and incorporation (occlusion) of peptide exclusively into {110} crystal sectors. Computational modeling of poly-Asp(86-93) adsorption to COD {110} and {101} surfaces also suggests increased stabilization of the COD {110} surface and negligible change to the natively stable {101} surface. Ultrastructural, colloidal-gold immunolocalization of OPN by transmission electron microscopy in human stones confirmed an intracrystalline distribution of OPN. In summary, OPN and its poly-Asp(86-93) sequence similarly affect COD mineral growth; the {110} crystallographic faces become enhanced and dominant attributable to {110} face inhibition by the protein/peptide, and peptides can incorporate into the mineral phase. We, thus, conclude that the poly-Asp(86-93) domain is central to the OPN ability to interact with the {110} faces of COD, where it binds to inhibit crystal growth with subsequent intracrystalline incorporation (occlusion).

Age and nature of eclogites in the Huwan shear zone, and the multi-stage evolution of the Qinling-Dabie-Sulu orogen, central China

In situ LA-ICPMS U-Pb, trace element, and Hf isotope data in zircon demonstrate a Carboniferous age for eclogite-facies metamorphism in Siluro-Devonian protoliths in the Huwan shear zone, Dabie Mountains, Central China. This age contrasts with the more prevailing Triassic age for high- to ultrahigh pressure (HP to UHP) metamorphism in the Qinling-Dabie-Sulu orogen. Metamorphic zircon in two eclogite samples from Sujiahe is characterized by low Th/U ratios, small negative Eu anomalies, flat HREE patterns, and low 176Lu/ 177Hf ratios. These geochemical signatures suggest that the zircon crystallized in the presence of garnet and in the absence of plagioclase feldspar. Furthermore, temperatures of ~ 655 and ~ 638 °C, calculated using the Ti content of zircon, are consistent with their formation during eclogite-facies metamorphism. The weighted mean 206Pb/ 238U age of 309 ± 4 Ma (2δ) for this zircon improves previous age estimates for eclogite-facies metamorphism in the Huwan shear zone, ranging from 420 to 220 Ma. Metamorphic zircon from one eclogite sample from Hujiawan, most likely formed during prograde metamorphism, yields an equivalent age estimate of 312 ± 11 Ma. Magmatic zircon cores in the three samples yield ages for the magmatic protoliths of the eclogites ranging from 420 ± 7 to 406 ± 5 Ma, and post-dating the middle Paleozoic collision of the North China and the Qinling terrain. The zircon crystals in the three eclogite samples display a large variation of ε Hf (t) values of − 4.9 to 21.3. The metamorphic zircon overgrowths show the same range of ε Hf (t) values as those of the inherited magmatic crystal interiors. This suggests that the metamorphic zircon overgrowths may have formed by dissolution-reprecipitation of pre-existing magmatic zircon thereby preserving their original Hf isotopic composition. The high ε Hf (t) values suggest that the protoliths were derived from depleted mantle sources, most likely Paleotethyan oceanic crust; while the low ε Hf (t) values are attributed to crustal contamination. Some eclogites in the Huwan shear zone have a distinctive signature of continental crust most probably derived from the Yangtze Craton. The coexistence of Paleozoic oceanic crust and Neoproterozoic continental crust with similar metamorphic ages in the Huwan shear zone implies that Paleozoic Paleotethyan oceanic crust was produced within a marginal basin of the northern Yangtze Craton. The opening of the Paleo-Tethyan ocean was slightly younger than the collision of the North China Craton and the Qinling terrain during the Late Paleozoic in the Qinling-Dabie-Sulu orogen. Subduction of the Paleo-Tethyan oceanic crust and associated continental basement resulted in the 309 ± 2 Ma (2σ) eclogite-facies metamorphism in the Huwan shear zone. The subsequent Triassic continent-continent collision led to the final coalescence of the Yangtze and Sino-Korean cratons. Amalgamation of the Yangtze and North China cratons was, therefore, a multistage process extending over at least 200 Ma.