Zinc systematics quantify crustal thickness control on fractionating assemblages of arc magmas

AbstractUnderstanding the processes leading to the broad chemical variability of arc magmas is an essential, yet not fully elucidated, issue in Earth Sciences. Here, I show that Zn–MgO–SiO2 systematics of magmatic arc rocks correlate significantly with arc thickness. Because Zn–MgO–SiO2 systematics are mostly controlled by fractionation of different mineral phases, this suggests a systematic change in the proportions of fractionating mineral assemblages depending on arc thickness. Using a mass balance model with a Monte Carlo approach, I show that Zn–MgO–SiO2 systematics can be quantitatively explained by a continuous transition from plagioclase-dominated fractionating assemblages in thin arcs to amphibole-garnet-magnetite-dominated assemblages in increasingly thicker arcs. Most likely, such a systematic change results from the increase of average depth of magma differentiation that is ultimately controlled by arc thickness. Results presented have implications on the causes of different geochemical trends in arcs, the role of arcs as H2O filters, and their association with porphyry deposits.

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Zinc Systematics Quantify Crustal Thickness Control on Fractionating Assemblages of Arc Magmas

10.21203/rs.3.rs-591162/v1 ◽

2021 ◽

Author(s):

M. Chiaradia

Keyword(s):

Balance Model ◽

Systematic Change ◽

Continuous Transition ◽

Porphyry Deposits ◽

Magmatic Arc ◽

Arc Magmas ◽

Mineral Phases ◽

Chemical Variability ◽

Mineral Assemblages

Abstract Understanding the processes leading to the broad chemical variability of arc magmas is an essential, yet not fully elucidated, issue in Earth Sciences. Here, I show that Zn-MgO-SiO2 systematics of magmatic arc rocks correlate significantly with arc thickness. Because Zn-MgO-SiO2 systematics are mostly controlled by fractionation of different mineral phases this suggests a systematic change in the proportions of fractionating mineral assemblages depending on arc thickness. Using a mass balance model with a Monte Carlo approach, I show that Zn-MgO-SiO2 systematics can be quantitatively explained by a continuous transition from plagioclase-dominated fractionating assemblages in thin arcs to amphibole-garnet-magnetite-dominated assemblages in increasingly thicker arcs. Such a systematic change results from the increase of average depth of magma differentiation that is ultimately controlled by arc thickness. Results presented have implications on the causes of different geochemical trends in arcs, the role of arcs as H2O filters, and their association with major porphyry deposits.

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The role of sulphur on the melting of Ca-poor sediment and on trace element transfer in subduction zones: an experimental investigation

Journal of Petrology ◽

10.1093/petrology/egab005 ◽

2021 ◽

Author(s):

Anne-Aziliz Pelleter ◽

Gaëlle Prouteau ◽

Bruno Scaillet

Keyword(s):

Trace Element ◽

Partial Melting ◽

Subduction Zones ◽

Sediment Flux ◽

Arc Magmas ◽

Trace Element Contents ◽

The Stability ◽

Element Transfer ◽

High Sediment

Abstract We performed phase equilibrium experiments on a natural Ca-poor pelite at 3 GPa, 750-1000 °C, under moderately oxidizing conditions, simulating the partial melting of such lithologies in subduction zones. Experiments investigated the effect of sulphur addition on phase equilibria and compositions, with S contents of up to ∼ 2.2 wt. %. Run products were characterized for their major and trace element contents, in order to shed light on the role of sulphur on the trace element patterns of melts produced by partial melting of oceanic Ca-poor sediments. Results show that sulphur addition leads to the replacement of phengite by biotite along with the progressive consumption of garnet, which is replaced by an orthopyroxene-kyanite assemblage at the highest sulphur content investigated. All Fe-Mg silicate phases produced with sulphur, including melt, have higher MgO/(MgO+FeO) ratios (relative to S-free/poor conditions), owing to Fe being primarily locked up by sulphide in the investigated redox range. Secular infiltration of the mantle wedge by such MgO and K2O-rich melts may have contributed to the Mg and K-rich character of the modern continental crust. Addition of sulphur does not affect significantly the stability of the main accessory phases controlling the behaviour of trace elements (monazite, rutile and zircon), although our results suggest that monazite solubility is sensitive to S content at the conditions investigated. The low temperature (∼ 800 °C) S-bearing and Ca-poor sediment sourced slab melts show Th and La abundances, Th/La systematics and HFSE signatures in agreement with the characteristics of sediment-rich arc magmas. Because high S contents diminish phengite and garnet stabilities, S-rich and Ca-poor sediment sourced slab melts have higher contents of Rb, B, Li (to a lesser extent), and HREE. The highest ratios of La/Yb are observed in sulphur-poor runs (with a high proportion of garnet, which retains HREE) and beyond the monazite out curve (which retains LREE). Sulphides appear to be relatively Pb-poor and impart high Pb/Ce ratio to coexisting melts, even at high S content. Overall, our results show that Phanerozoic arc magmas from high sediment flux margins owe their geochemical signature to the subduction of terrigenous, sometimes S-rich, sediments. In contrast, subduction of such lithologies during Archean appears unlikely or unrecorded.

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Evaluation of Chemical Variability of Cured Vanilla Beans (Vanilla tahitensis and Vanilla planifolia)

Natural Product Communications ◽

10.1177/1934578x0900401016 ◽

2009 ◽

Vol 4 (10) ◽

pp. 1934578X0900401 ◽

Cited By ~ 1

Author(s):

Christel Brunschwig ◽

François Xavier Collard ◽

Jean-Pierre Bianchini ◽

Phila Raharivelomanana

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Dry Matter ◽

Monounsaturated Fatty Acids ◽

Vanilla Planifolia ◽

Chemical Variability ◽

Total Fatty Acids ◽

Curing Method ◽

Fatty Acid Compositions

In order to establish a chemical fingerprint of vanilla diversity, thirty samples of V. planifolia J. W. Moore and V. tahitensis G. Jackson cured beans from seven producing countries were examined for their aroma and fatty acid contents. Both fatty acid and aroma compositions were found to vary between vanilla species and origins. Vanillin was found in higher amounts in V. planifolia (1.7-3.6% of dry matter) than in V. tahitensis (1.0-2.0%), and anisyl compounds were found in lower amounts in V. planifolia (0.05%) than in V. tahitensis (1.4%-2.1%). Ten common and long chain monounsaturated fatty acids (LCFA) were identified and were found to be characteristic of the vanilla origin. LCFA derived from secondary metabolites have discriminating compositions as they reach 5.9% and 15.8% of total fatty acids, respectively in V. tahitensis and V. planifolia. This study highlights the role of the curing method as vanilla cured beans of two different species cultivated in the same country were found to have quite similar fatty acid compositions.

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The effect of the trisulfur radical ion on molybdenum transport by hydrothermal fluids

10.5194/egusphere-egu21-3318 ◽

2021 ◽

Author(s):

Maria A. Kokh ◽

Clement Laskar ◽

Gleb S. Pokrovski

Keyword(s):

Composition Range ◽

Ion Pairs ◽

Primary Source ◽

Econ Geol ◽

Hydrothermal Conditions ◽

Earth Planet ◽

Porphyry Deposits ◽

Experimental And Theoretical Studies ◽

Partitioning Behavior

Knowledge of molybdenum (Mo) speciation under hydrothermal conditions is a key for understanding the formation of porphyry deposits which are the primary source of Mo. Existing experimental and theoretical studies have revealed a complex speciation, solubility and partitioning behavior of Mo in fluid-vapor-melt systems, depending on conditions, with the (hydrogen)molybdate (HMoO4-, MoO42-) ions and their ion pairs with alkalis in S and Cl-poor fluids [1-3], mixed oxy-chloride species in strongly acidic saline fluids [4, 5], and (hydrogen)sulfide complexes (especially, MoS42-) in reduced H2S-bearing fluids and vapors [6-8]. However, these available data yet remain discrepant and are unable to account for the observed massive transport of Mo in porphyry-related fluids revealed by fluid inclusion analyses demonstrating 100s ppm of Mo (e.g., [9]). A potential missing ligand for Mo may be the recently discovered trisulfur radical ion (S3&#8226;-), which is predicted to be abundant in sulfate-sulfide rich acidic-to-neutral porphyry-like fluids [10]. We performed exploratory experiments of MoS2 solubility in model sulfate-sulfide-S3&#8226;--bearing aqueous solutions at 300&#176;C and 450 bar. We demonstrate that Mo can be efficiently transported by S3&#8226;--bearing fluids at concentrations ranging from several 10s ppm to 100s ppm, depending on the fluid pH and redox, whereas the available data on OH-Cl-S complexes cited above predict negligibly small (<100 ppb) Mo concentrations at our conditions. Work is in progress to extend the experiments to wider T-P-composition range of porphyry fluids and to quantitatively assess the role of S3&#8226;- in Mo transport by geological fluids.<ul><li>1. Kudrin A.V. (1989) Geochem. Int. 26, 87&#8211;99.</li> <li>2. Minubayeva Z. and Seward T.M. (2010) Geochim. Cosmochim. Acta 74, 4365&#8211;4374.</li> <li>3. Shang L.B. et al. (2020) Econ. Geol. 115, 661&#8211;669.</li> <li>4. Ulrich T. and Mavrogenes J. (2008) Geochim. Cosmochim. Acta 72, 2316-2330.</li> <li>5. Borg S. et al. (2012) Geochim. Cosmochim. Acta 92, 292&#8211;307.</li> <li>6. Zhang L. et al. (2012) Geochim. Cosmochim. Acta 77, 175&#8211;185.</li> <li>7. Kokh M.A. et al. (2016) Geochim. Cosmochim. Acta 187, 311&#8211;333.</li> <li>8. Liu W. et al. (2020) Geochim. Cosmochim. Acta 290, 162&#8211;179.</li> <li>9. Kouzmanov K. and Pokrovski G.S. (2012) Soc. Econ. Geol. Spec. Pub. 16, 573&#8211;618.</li> <li>10. Pokrovski G.S. and Dubessy J. (2015) Earth Planet. Sci. Lett. 411, 298&#8211;309.</li> </ul>

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Chapter 23: Alteration, Mineralization, and Age Relationships at the Kışladağ Porphyry Gold Deposit, Turkey

10.5382/sp.23.23 ◽

2020 ◽

pp. 467-495

Author(s):

T. Baker ◽

S. Mckinley ◽

S. Juras ◽

Y. Oztas ◽

J. Hunt ◽

...

Keyword(s):

Volcanic Rocks ◽

White Mica ◽

Western Anatolia ◽

Low Grade ◽

Porphyry Deposits ◽

Magmatic Arc ◽

Argillic Alteration ◽

Metamorphic Basement ◽

Slab Tear ◽

Roll Back

Abstract The Miocene Kışladağ deposit (~17 Moz), located in western Anatolia, Turkey, is one of the few global examples of Au-only porphyry deposits. It occurs within the West Tethyan magmatic belt that can be divided into Cretaceous, Cu-dominant, subduction-related magmatic arc systems and the more widespread Au-rich Cenozoic magmatic belts. In western Anatolia, Miocene magmatism was postcollisional and was focused in extension-related volcanosedimentary basins that formed in response to slab roll back and a major north-south slab tear. Kışladağ formed within multiple monzonite porphyry stocks and dikes at the contact between Menderes massif metamorphic basement and volcanic rocks of the Beydağı stratovolcano in the Uşak-Güre basin. The mineralized magmatic-hydrothermal system formed rapidly (<400 kyr) between ~14.75 and 14.36 Ma in a shallow (<1 km) volcanic environment. Volcanism continued to at least 14.26 ± 0.09 Ma based on new age data from a latite lava flow at nearby Emiril Tepe. Intrusions 1 and 2 were the earliest (14.73 ± 0.05 and 14.76 ± 0.01 Ma, respectively) and best mineralized phases (average median grades of 0.64 and 0.51 g/t Au, respectively), whereas younger intrusions host progressively less Au (Intrusion 2A: 14.60 ± 0.06 Ma and 0.41 g/t Au; Intrusion 2 NW: 14.45 ± 0.08 Ma and 0.41 g/t Au; Intrusion 3: 14.39 ± 0.06 and 14.36 ± 0.13 Ma and 0.19 g/t Au). A new molybdenite age of 14.60 ± 0.07 Ma is within uncertainty of the previously published molybdenite age (14.49 ± 0.06 Ma), and supports field observations that the bulk of the mineralization formed prior to the emplacement of Intrusion 3. Intrusions 1 and 2 are altered to potassic (biotite-K-feldspar-quartz ± magnetite) and younger but deeper sodic-calcic (feldspar-amphibole-magnetite ± quartz ± carbonate) assemblages, both typically pervasive with disseminated to veinlet-hosted pyrite ± chalcopyrite ± molybdenite and localized quartz-feldspar stockwork veinlets and sodic-calcic breccias. Tourmaline-white mica-quartz-pyrite alteration surrounds the potassic core both within the intrusions and outboard in the volcanic rocks. Tourmaline was most strongly developed on the inner margins of the tourmaline-white mica zone, particularly along the Intrusion 1 volcanic contact where it formed breccias and veins, including Maricunga-style veinlets. Field relationships show that the early magmatic-hydrothermal events were cut by Intrusion 2A, which was then overprinted by Au-bearing argillic (kaolinite-pyrite ± quartz) alteration, followed by Intrusion 3 and late-stage, low-grade to barren argillic and advanced argillic alteration (quartz-pyrite ± alunite ± dickite ± pyrophyllite). Gold deportment changes with each successive hydrothermal event. The early potassic and sodic-calcic alteration controls much of the original Au distribution, with the Au dominantly deposited with feldspar and lesser quartz and pyrite. Tourmaline-white mica and argillic alteration events overprinted and altered the early Au-bearing feldspathic alteration and introduced additional Au that was dominantly associated with pyrite. Analogous Au-only deposits such as Maricunga, Chile, La Colosa, Colombia, and Biely Vrch, Slovakia, are characterized by similar alteration styles and Au deportment. The deportment of Au in these Au-only porphyry deposits differs markedly from that in Au-rich porphyry Cu deposits where Au is typically associated with Cu sulfides.

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Race for Social Justice in Higher Education

10.4018/978-1-7998-8532-0.ch009 ◽

2022 ◽

pp. 138-156

Author(s):

Bryan Q. Patterson

Keyword(s):

Higher Education ◽

United States ◽

Social Justice ◽

High Education ◽

Mission Statements ◽

Colleges And Universities ◽

Systematic Change ◽

Institutions Of Higher Education ◽

New Model

In the last decade, there has been a greater focus on social justice concerns in United States. These concerns include addressing situations of racism, microaggressions, and racial injustices. As a result of these concerns, the need for social justice has become more apparent for institutions of higher education to adjust and rethink how they become more inclusive and provide more equitable opportunities for all stakeholders. Institutions of higher education are being pushed into unfamiliar territory, and the role of academics and high education institutions will need to be redefined in a new model of true systematic change and policy overhaul. How do institutions of higher education (colleges and universities) become more accountable in reshaping their purpose and mission statements through the lens of social justice and inclusivity? This chapter will generate insights and illuminate ongoing institutional conversations regarding the successful adoption of social justice frameworks and practices in the foundations of higher education.

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Role of Aspartic and Polyaspartic Acid on the Synthesis and Hydrolysis of Brushite.

Journal of Functional Biomaterials ◽

10.3390/jfb10010011 ◽

2019 ◽

Vol 10 (1) ◽

pp. 11 ◽

Cited By ~ 5

Author(s):

Katia Rubini ◽

Elisa Boanini ◽

Adriana Bigi

Keyword(s):

Aspartic Acid ◽

Octacalcium Phosphate ◽

Physiological Solution ◽

Cooperative Action ◽

Phosphate Dihydrate ◽

Mineral Phases ◽

Carboxylate Groups ◽

Hydrolysis Of ◽

Thermal Stability Of

Dicalcium phosphate dihydrate (DCPD) is one of the mineral phases indicated as possible precursors of biological apatites and it is widely employed in the preparation of calcium phosphate bone cements. Herein, we investigated the possibility to functionalize DCPD with aspartic acid (ASP) and poly-aspartic acid (PASP), as models of the acidic macromolecules of biomineralized tissues, and studied their influence on DCPD hydrolysis. To this aim, the synthesis of DCPD was performed in aqueous solution in the presence of increasing concentrations of PASP and ASP, whereas the hydrolysis reaction was carried out in physiological solution up to three days. The results indicate that it is possible to prepare DCPD functionalized with PASP up to a polyelectrolyte content of about 2.3 wt%. The increase of PASP content induces crystal aggregation, reduction of the yield of the reaction and of the thermal stability of the synthesized DCPD. Moreover, DCPD samples functionalized with PASP display a slower hydrolysis than pure DCPD. On the other hand, in the explored range of concentrations (up to 10 mM) ASP is not incorporated into DCPD and does not influence its crystallization nor its hydrolysis. At variance, when present in the hydrolysis solution, ASP, and even more PASP, delays the conversion into the more stable phases, octacalcium phosphate and/or hydroxyapatite. The greater influence of PASP on the synthesis and hydrolysis of DCPD can be ascribed to the cooperative action of the carboxylate groups and to its good fit with DCPD structure.

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Solubility of the nadorite group minerals: implications for mobility of Sb and Bi in oxidised settings

Environmental Chemistry ◽

10.1071/en17076 ◽

2017 ◽

Vol 14 (4) ◽

pp. 224

Author(s):

Adam J. Roper ◽

Peter Leverett ◽

Timothy D. Murphy ◽

Peter A. Williams

Keyword(s):

Redox Potential ◽

Significant Role ◽

Stability Studies ◽

Secondary Minerals ◽

Relative Stabilities ◽

Mineral Phases ◽

Minor Part ◽

A Minor

Environmental contextThe dispersion of antimony in the environment has been misunderstood over the last few decades. Investigating the solubility of naturally forming mineral phases such as nadorite resulted in determination of its limited role in Sb dispersion, providing evidence that nadorite can only limit antimony dispersion in mildly oxidising conditions. Nadorite can only play a significant role in Sb immobilisation in a particular redox window, which forms only a minor part of the framework of Sb dispersion. AbstractAs part of a study of the control that secondary minerals exert on the dispersion of antimony and bismuth in the supergene environment, syntheses and stability studies of nadorite (PbSbO2Cl) and perite (PbBiO2Cl) have been undertaken. Solubilities in aqueous HNO3 were determined at 298.2K and the data obtained used to calculate values of ΔGfθ(298.2K). The ΔGfθ(s, 298.2K) values for PbSbO2Cl (–622.0±2.8kJmol–1) and PbBiO2Cl (–590.0±1.3kJmol–1) have been used in subsequent calculations to determine relative stabilities and relationships with other common secondary Sb and Bi minerals. While the role of nadorite in immobilising Sb is dependent upon the prevailing redox potential such that SbIII is stable, perite may be a significant phase in limiting the dispersion of Bi in certain supergene settings.

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The role of N transformations in the formation of acidic subsurface layers in stock urine patches

Soil Research ◽

10.1071/sr03109 ◽

2004 ◽

Vol 42 (2) ◽

pp. 221 ◽

Cited By ~ 10

Author(s):

J. R. Condon ◽

A. S. Black ◽

M. K. Conyers

Keyword(s):

Soil Surface ◽

Urea Hydrolysis ◽

Balance Model ◽

Urea Solution ◽

Nitrogen Transformations ◽

N Transformations ◽

Soil Layers ◽

Subsurface Layers ◽

Dominant Process

This study examines the role of nitrogen transformations in the acidification of soil under stock urine patches, specifically the formation of acidic subsurface layers. These are horizontal planes of acidity several centimetres below the soil surface. Glasshouse studies were conducted to relate nitrogen transformations to measured pH changes in soil treated with urine or urea solution (simulated urine). Acidic subsurface layers formed in both urine- and simulated urine-treated soil. With the development of a H+ balance model, the contribution of nitrogen transformations to changes in the H+ concentrations in simulated urine patches was determined.During the first 9 days following treatment, urea hydrolysis and NH3 volatilisation dominated changes in H+ concentration. After that, net immobilisation contributed to H+ changes; however, nitrification was the dominant process occurring. Downward movement of NH4+ originating from urea hydrolysis allowed more nitrification to occur in lower soil layers. The net result of these processes was net acidification of the 4–6, 6–8, and 8–10 cm layers by approximately 0.7, 0.6, and 0.3 pH units, respectively. Thus nitrogen transformations were responsible for the formation of acidic subsurface layers in simulated stock urine patches within 6 weeks of application.

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