Apatite Content Research Articles

Raman Spectroscopic Analysis of Molecular Structure and Mechanical Properties of Hypophosphatasia Primary Tooth.

Mild hypophosphatasia (HPP) can be difficult to distinguish from other bone disorders in the absence of typical symptoms such as the premature loss of primary teeth. Therefore, this study aimed to analyze the crystallinity of hydroxyapatite (HAp) and the three-dimensional structure of collagen in HPP teeth at the molecular level and to search for new biomarkers of HPP. Raman spectroscopy was used to investigate the molecular structure, composition, and mechanical properties of primary teeth from healthy individuals and patients with HPP. The results showed that the crystallinity of HAp decreased and the carbonate apatite content increased in the region near the dentin-enamel junction (DEJ) of HPP primary teeth. X-ray diffraction (XRD) analyses confirmed a decrease in HAp crystallinity near the DEJ, and micro-computed tomography (CT) scanning revealed a decrease in mineral density in this region. These results suggest incomplete calcification in HPP primary dentin and may contribute to the development of diagnostic and therapeutic agents.

Magmatic degassing and fluid metasomatism promote compositional variation from I-type to peralkaline A-type granite in the late Cretaceous Fuzhou felsic complex, SE China

Abstract A-type granites generally have much lower water, higher temperature, and incompatible element concentrations than I-type granitoids. Yet it remains unclear why I-A-type granitic complexes occur in convergent plate margins. Here we conduct geochemical analyses on apatite and mafic minerals from the late Cretaceous I-A-type granitic complex in Fuzhou area, SE China, aiming to decipher differentiation, fluid metasomatism, and degassing that primarily control the compositional diversity of felsic magmas. Apatites in both rock types are F-rich and show large H2O and δD variations, i.e., 341–3892 ppm H2O and –325 to +336‰ δD in I-type granitoids; 67–1366 ppm H2O and –251 to +1439‰ δD in A-type granites. H2O in apatite is negatively correlated with La/Sm and Sr/Y in the I-type granitoids, whereas it is positively correlated with Ce and total rare earth element (REE) concentrations in the A-type granites. Once H2O increases up to hundreds of ppm, both rock types show a rapid decrease of H2O/Ce, an increase of F/Cl, and extensive H isotope fractionation. Arfvedsonite occurs as a late crystallizing mineral in the A-type granite and has much higher contents of Na2O, K2O, F, and high field strength elements (HFSE) than hornblende in the I-type granitoids, indicating the addition of F-HFSE-rich alkaline fluids during its magmatic evolution. The consumption of arfvedsonite and formation of aegirine further indicate the role of fluid metasomatism and H2 degassing via a reaction of 3Na3Fe5Si8O22(OH)2 + 2H2O = 9NaFeSi2O6 + 2Fe3O4 + 6SiO2+5H2. The combined geochemical data demonstrate that the systematic differences in mineral assemblage, whole-rock composition, magma temperature, H2O content, and δD of apatite between the I- and A-type granites are likely attributed to varying degrees of differentiation, fluid metasomatism and magmatic degassing. The I-type granitoids experienced hornblende, biotite, plagioclase, K-feldspar, and apatite fractionation and close-system degassing. The A-type granite was likely formed from the I-type monzogranitic magma that was metasomatized by the mantle-derived F-HFSE-rich alkaline fluids to produce the peralkaline magma, which further experienced K-feldspar + plagioclase + biotite + apatite fractionation and open-system degassing. Further numerical estimation indicates that the primary magma of Fuzhou granitic complex contained ~3.0 wt% H2O, and the lower water content of A-type granite was likely attributed to strong degassing during its emplacement. Our results indicate that some peralkaline A-type granites can be generated from relatively water-poor I-type granitic magmas by fluid metasomatism and degassing.

Inorganic phosphorous availability and mobility in a manufactured soil

Manufactured soils, created by combining various organic and inorganic waste materials and byproducts, may be tailored to specific applications, providing an alternative to the extraction of natural soils. It is important for them to be capable of supporting plant growth without the need for significant management or fertiliser applications, the over-application of which can have adverse environmental effects.We examined the dynamics of phosphorus (P) transformations within a manufactured soil and the implications for nutrient cycling. A freshly prepared manufactured soil (32.5 % composted green waste, 32.5 % composted bark, 25 % horticultural grit, and 10 % lignite clay) was studied over one year in temperature and moisture controlled mesocosms. Leachate was collected to achieve high-resolution monitoring of leached phosphate concentrations.Initially, leached dissolved inorganic phosphorus (DIP) concentrations were low (0.02 ± 0.01 mg P L−1), before increasing by 160 μg P L−1 d−1 over the first 42 days to 5.57 ± 1.23 mg P L−1. After reaching a maximum concentration, DIP concentrations remained relatively consistent, varying by only 1.67 mg P L−1 until day 270. The increase in leached DIP was likely driven by soil organic matter mineralisation and the cleavage of carbon‑phosphorus bonds by the soil microbes to satisfy carbon demand with mineralogical influences, such as a decrease in apatite content, also contributing. Sorption and desorption from soil particles were the processes behind the P loss from the soil, which was followed by slow diffusion and eventual loss via leaching. The fertiliser application on phosphate dynamics resulted in increased DIP leaching.P concentrations observed in the manufactured soil were within the range considered sufficient to support plant growth. However, the mean leached phosphorus concentrations were higher than reported eutrophication thresholds suggesting that these soils may pose a risk to surface waters in their current form.

Diverse apatite geochemical compositions in early Paleozoic granitoids of the North Qinling orogen, China: Insights into their petrogenesis and magma sources

Apatite geochemistry in granitoids is controlled primarily by the original melt compositions and partition coefficients. However, additional factors (e.g., post-crystallization effects, mineral crystallization sequences, and crustal assimilation) can also contribute to variations in apatite compositions. In this study, we collected three groups of early Paleozoic granitoids from the North Qinling Orogen and obtained in situ geochemical data for apatite. The granitoids were formed by partial melting of oceanic arc crust (group A), recycling of ancient crust (group B), and melting of the lithospheric mantle and extensive fractionation (group C). Trace element and Nd isotope data show the apatite from the Taiping and Manziying plutons (group A) were affected by post-crystallization processes and crustal assimilation, respectively. In addition, crystallization of plagioclase/allanite and apatite resulted in the variable Eu anomalies and rare earth element contents of apatite in the group A granitoids. In contrast, apatite compositions in group C were controlled primarily by the fractionation of hornblende. However, the decoupling of Eu anomalies of apatite and their host rocks, particularly for group B, cannot be easily explained by the aforementioned factors. As such, the redox state may also have been an important factor. We used a ternary diagram (10 × [Eu/Eu*]N–V–Ga) to constrain the redox state from the apatite data, and provide insights into the types and petrogenesis of the host granitoids. Combined with the whole-rock and zircon geochemical data, we found that the apatite from the rocks derived from continental crust (group B and cratonic adakites) is generally reduced, whereas apatite from the mafic rocks and high BaSr granitoids is highly oxidized. The highest degree of oxidation was found for the altered apatite from the group A granitoids and unaltered apatite in the orogenic adakites, possibly due to interactions with fluid derived from oceanic crust. Moreover, unaltered group A granitoids exhibit a transitional trend from an oxidized to a reduced state. Apatite geochemistry can be used to constrain the redox state of adakitic rocks and whether they have a continental or oceanic crustal origin. The high Sr contents of high BaSr granitoids are inherited from their mantle source.

The Lac à l'Orignal phosphate deposit and constraints on high-quality phosphatic ore in massif-type anorthosite, Grenville Province, Canada

Phosphate is an indispensable component in the fertilizer industry. It has recently become a critical part of the green energy transition because of the demand for lithium ferro phosphate in rechargeable batteries. A significant amount of phosphate ore (∼90 %) is globally produced from sedimentary rocks. High-quality phosphate ore containing low amounts of toxic elements, however, is mostly produced from igneous carbonatite.The Lac à l'Orignal deposit (∼1069–993 Ma), Canada, in the central Grenville Province, contains a large amount of fluorapatite (≤ 20 %) hosted in oxide-bearing norite-gabbronorite-anorthosite layered intrusions. The deposit is hosted in the Vanel Anorthosite (1080 ± 2 Ma) near the northern border of the Mattawa Anorthosite (1016 ± 2 Ma). The major host rock oxide-apatite-gabbronorite (OAGN) is primarily composed of plagioclase, orthopyroxene, clinopyroxene, fluorapatite, ilmenite, and magnetite. The Al contents of the OAGN orthopyroxene indicate that the magmatic deposit was emplaced at mid-low crustal levels (∼2.0–3.6 kbar) and reverse zoning in the OAGN plagioclase suggests <2.5 kbar of pressure change during their crystallization. An overall increase of REE + Y concentrations in the OAGN fluorapatite with decreasing their fluorapatite contents indicates that the magma went through fractional crystallization. This study suggests that high abundances (ca. > 8 %) of fluorapatite in some OAGN were produced from crystal avalanching after initial crystal settling. Antithetic correlation between the Cl content of fluorapatite and the Mg# [Mg/(Mg + Fe2+)] of coexisting orthopyroxene suggests that phosphate ores with low Cl contents are expected for OAGN that formed at the initial stages of magma crystallization. Therefore, the Mg# of the OAGN orthopyroxene provides an exploration tool for targeting phosphate ore with low Cl content, which is preferred in the production of phosphoric acid, a major intermediate feedstock for the fertilizer and green energy industries. Apatite contents in carbonatite and average P2O5 content in carbonatite melt are generally similar to those of the Lac à l'Orignal OAGN. The average concentrations of REE, and toxic metals, such as Pb, Th, and U, in the OAGN fluorapatite are, however, lower than those in apatite from carbonatite worldwide. Therefore, the apatite of the OAGN appears to be of high quality and more environmentally-friendly as a source of phosphate ore.

Apatite-rich zones in the Uppermost Upper Zone, Northern Limb, Bushveld Complex: Possible non-conventional source of REE and TiO2

The uppermost Upper Zone of the Bushveld Complex is known as a potential host of significant apatite-ilmenite resources. Recent exploration studies have delineated two apatite-rich zones representing a huge potential resource of phosphate. A detailed mineralogical and geochemical study of the two apatite-rich zones is undertaken to demonstrate that in addition to phosphate, apatite and ilmenite could be important saleable by-products for REE and Ti. In the Lower Apatite Zone (LAZ), the average concentrations of apatite, ilmenite, and titano-magnetite are 11%, 6%, and 18%, respectively. Grades of about 30 wt% combined apatite, ilmenite, and titano-magnetite can be recovered from the Upper Apatite Zone (UAZ), of which apatite and granular ilmenite constitute 9 and 10%, respectively. There is an association between diamagnetic (apatite), paramagnetic (mostly silicates and ilmenite), ferromagnetic (titano-magnetite) minerals and, to a lesser extent, sulphides. In addition, the majority of the targeted minerals; apatite, ilmenite, and titano-magnetite are relatively coarse, with a median value ranging between 270 μm and 931 μm. In-situ trace element data obtained on apatite demonstrate an increase in Light Rare Earth Elements (LREE) stratigraphically, grading from an average of 3180 ppm Total Rare Earth Elements (TREE+Y) in the LAZ to an average of 4068 ppm TREE+Y in the UAZ, indicating a sub-economic potential of REE that may be economically viable as by-product to phosphate. Preliminary resource estimations show that ~1,405,560 t and ~1,798,056 t of TREE can be exploited from the LAZ and UAZ, respectively. The discrete ilmenite grains are an attractive additional by-product considering their higher average >50% TiO2 and lower concentration of impurities such as <1.06% MgO, <1.21% MnO, <0.08% Al2O3, <0.02% V2O5 and <0.01% Cr2O3. These results suggest that apatite-rich layers in mafic layered intrusions are viable prospects for economic extraction of REE in conjunction with titanium as other by-products that can be recovered from phosphate rocks.

Processes controlling rare earth element distribution in sedimentary apatite: Insights from spectroscopy, in situ geochemistry and O and Sr isotope composition

ABSTRACTIn phosphorites, the content and distribution of rare earth elements are linked to the environment of phosphogenesis. This paper focuses on the question of sources and processes controlling the rare earth element content of apatite from Belgian phosphorites formed during three major phosphogenic events in the Lower Palaeozoic, Late Cretaceous and Cenozoic. To constrain sources and processes, new data include petrological, mineralogical (including cathodoluminescence and Raman spectroscopy) and in situ trace element and Sr and O isotope analyses of apatite. Fluorapatite from Lower Palaeozoic P‐rich conglomerates has the greatest rare earth element enrichment. It is affected by metamorphism that led to deformation of apatite nodules and formation of garnet porphyroblast inclusions. The role of Fe‐oxyhydroxides in element scavenging is highlighted by some apatite nodules that maintain their primary middle rare earth element enrichment, while others are characterized by altered rare earth element patterns resulting from competition for these elements between co‐crystallizing minerals during deformation. A systematic shift towards lower δ18O and radiogenic Sr isotopic composition compared to contemporaneous seawater indicate interaction with 18O‐depleted meteoric fluids and a crustal component. By contrast, carbonate‐rich fluorapatite from the Late Cretaceous phosphatic chalk mostly keeps its primary trace element and isotopic signatures (close to seawater), although an external rare earth element addition is noted, as well as rare earth element redistribution induced by diagenetic alteration. Cenozoic carbonate fluorapatite nodules mostly present flat rare earth element patterns that are indicative of a detrital influence. Slight changes in rare earth element distribution are assigned to post‐depositional alteration, which also led to an increase in radiogenic Sr, with unchanged δ18O compared to seawater. The methodology followed here efficiently helps in deciphering the processes that modified the chemistry of apatite in the frame of major phosphogenic events.

Cathodoluminescence and geochemical characteristics of Apatite: Implications for mineral exploration in the Xiongcun District, Tibet, China

Apatite grains from the No. 2 porphyry Cu–Au deposit in the Xiongcun district of Tibet, China, have a range of physical and compositional features. This study investigates the potential use of apatite associated with hydrothermal alteration as a tool for mineral exploration. In situ textural, cathodoluminescence (CL), and chemical analyses were performed on thin sections containing apatite from various alteration zones in the deposit. No clear variation was seen in apatite from rocks of the potassic, sodic–calcic, chlorite–sericite, phyllic, and propylitic alteration zones using visible light and scanning electron microscopy; however, distinct variations were observed in optical cathodoluminescence (OP-CL) (dark yellow to green, orange to green, yellow–brown to green, yellow-orange to brown, and light yellow–brown to green luminescence for the respective zones). The alteration-related differences in luminescence were a result of the interaction between Fe and Mn; the Na and Cl contents; and depletion in total heavy rare earth elements (ΣHREE) and Y. The variations in the REE contents of apatite from different types of altered rock record reactions with Cl- and F-rich fluids. The partitioning behavior of Cl between apatite and hydrothermal fluids is influenced by pressure, temperature, pH, and fluid composition, whereas the partitioning of F between apatite and fluids is dependent on the fluid composition and not the temperature. At high temperatures, Eu3+ is reduced to Eu2+, which results in negative Eu anomalies in apatite from the potassic-altered rocks and propylitic-altered rocks. Apatite grains in the sodic–calcic-altered rocks and chlorite–sericite-altered rocks show a similar enrichment in light REEs (LREEs) that resulted from REE and Y incorporation as follows: Na+ + (Y + REE)3+ = 2Ca2+. Apatite grains in the phyllic-altered rocks are enriched in the middle REEs. This study confirms that the luminescence, chemical composition (including Fe, Mn, Na, Cl, ΣHREE, and Y contents), and REE patterns of apatite can be affected by hydrothermal alteration; therefore, these results may be used to constrain the evolution of ore-forming hydrothermal fluids and may offer an effective tool for mineral exploration.

Variations in water saturation states and their impact on eruption size and frequency at the Aso supervolcano, Japan

The exsolution of a magmatic volatile phase in the plumbing systems of volcanoes plays a key role in controlling growth dynamics of subvolcanic reservoirs and eruptive styles. By using common petrological proxies found in volcanic deposits, such as melt inclusions and apatite crystals, the presence of such an exsolved magmatic volatile phase can be traced, specifically the exsolution of water from silicate melt. To monitor variations in the water saturation state of magmas from the Aso volcanic complex (Kyushu, Japan) prior to and during the catastrophic Aso-4 caldera-forming event (at ∼86 ka BP), we investigate a set of pre-Aso-4 and Aso-4 deposits, combining volatile budgets (F, Cl, OH, S) of melt inclusions, matrix glasses, and apatite crystals, with sulfur isotope signatures in apatite. F-Cl-OH partitioning in apatite along with melt inclusion data from pre-Aso-4 units indicate water-undersaturated conditions during magma evolution until around 10 ka prior to the Aso-4 event. In contrast, eruptions occurring within the last ∼10 ka prior to the Aso-4 event indicate the presence of a water-rich exsolved magmatic volatile phase in the eruptible portions of the subvolcanic reservoir. Likewise, sulfur systematics in apatite and melt inclusions from the Aso-4 event suggest the exsolution of a water-rich magmatic volatile phase at some point prior to the caldera-forming event. Recharge of mafic magmas shortly before the Aso-4 eruption induced chemical hybridization in the resident upper crustal mush, bringing the reservoir back to less evolved compositions and water-undersaturated conditions. This hybridization event is recorded by volatile contents of both apatite and matrix glasses from late-erupted, crystal-rich products of the Aso-4 event, all yielding water-undersaturated signatures. During this hybridization event, chemical dilution and partial redissolution of the exsolved volatile phase reduced the magma compressibility significantly, so that additional magma influx from depth might have allowed a sharply increasing overpressurization in the subvolcanic reservoir and served as a potential trigger for the cataclysmic Aso-4 eruption. Drawing from our observations made on Aso, we propose that recharging of large silicic upper-crustal reservoirs with increased volumes of drier and more mafic melts can influence their water saturation states and associated physical properties. Such changes could contribute to the triggering of large-scale caldera-forming events.

Катодолюминесценция конодонтовых элементов

Conodont elements are used as a geochemical archive of seawater. Some compositional features of conodont elements reflect conodont ecology and trophic structure of Palaeozoic pelagic ecosystems. However, the screening of conodont elements prior to geochemical and/or isotopic studies is a real problem. This study evaluates SEM cathodoluminescence (SEM-CL), which is very sensitive to the REE and Mn content of apatite, for the detection of traces of secondary transformation in the composition of conodont bioapatite. The SEM-CL of conodont elements is similar to that of unaltered shark teeth (blue-violet), but differs significantly from that of fossil vertebrate teeth (orange-red). Thermal alteration has little effect on the SEM-CL. Elements with a CAI of 1—1.5 show a redder and more intense CL than elements with a CAI of 5. In the case of corrosion of the conodont element surface in carbonate host rocks, the CL of the outer parts of the conodont element become reddish due to invasion of the carbonate material. Conodont elements from the clay host rock show deep purple SEM-CL. Thus, SEM-CL allows detection of the results of secondary processes in conodont mineralised tissues, including enrichment by REE and/or Mn, corrosion and contamination by carbonate material. This method can be used to screen significantly altered samples prior to chemical and isotopic analyses.

Integrated Technology for Processing of Apatite Concentrate

Integrated Technology for Processing of Apatite Concentrate

Interactions between rare-earth zirconates (RE2Zr2O7) and CMAS silicate melts

Rare-earth zirconates (RE2Zr2O7) are potential thermal barrier coatings (TBCs) candidates exhibiting excellent thermal insulation property to protect underlying superalloy substrate. These coating materials, however, are subjected to degradation caused by molten silicon-containing sand dust and volcanic ash whose main compositions are CaO-MgO-AlO1.5-SiO2 (brief to CMAS) at higher operating temperatures (> 1200ºC). Here, we have studied the thermochemical interactions between three RE2Zr2O7 (Sm2Zr2O7, Gd2Zr2O7 and Yb2Zr2O7) and CMAS with three different compositions (referred to as CMAS-1, CMAS-2 and CMAS-3, respectively) at 1300ºC/30 min. Both the diversities of the REO1.5 identity and CMAS composition result in the precipitation of apatite with varying stoichiometry. For an equivalent CMAS case, there is a linear correlation between the apatite content and the RE cation radius. In CMAS-1, the Ca:RE ratio of apatite observed in the Sm2Zr2O7 case is ∼0.31, larger than that of Gd2Zr2O7 (∼0.30) and Yb2Zr2O7 (∼0.20). Additionally, the RE3+ solubility in equilibrium with apatite decreases with the increased CaO content from CMAS-3 to CMAS-1 for a given RE2Zr2O7 material, facilitating the apatite precipitation within a short time. For example, in Sm2Zr2O7 case the Sm3+ solubility decrease from ∼3.18 at % to ∼0.70 at % as the CaO content increases from 19 mol % ( in CMAS-3) to 33 mol % ( in CMAS-1). Also, the composition of residual CMAS melt changes as the interaction proceed, which can impact its flow property and infiltration propensity. These finds may advance the design of current and next-generation TBCs material and development of effective strategies to mitigate the CMAS-induced coating failure.

Applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in Rcrust

Phase equilibria modelling techniques can constrain the equilibrium conditions of major rock-forming minerals, however current thermodynamic databases and activity-composition models do not accommodate minor and trace elements as chemical components in modelled systems. This paper presents the integration of trace element partitioning routines between melt and solid phases in the thermodynamic modelling tool Rcrust in order to effectively estimate the trace element composition of stable phases when melt is present. Since trace elements occur in large abundances in accessory phases for which we do not currently have activity-composition models this paper further presents the integration of accessory phase saturation routines for apatite and monazite, two commonly occurring accessory phases in granitic rocks.This provides a novel methodology for approximating trace element distribution among thermodynamically constrained phases with thermodynamically unconstrained accessory phases, apatite and monazite. A case study of the Peninsula Pluton granodiorite, South Africa, is used to validate the use of accessory phase saturation and trace element partitioning with phase equilibria modelling. The results highlight the importance of major element components that also contribute to accessory phase formation such as calcium in apatite (which can accommodate a non-trivial quantity of the available calcium) and the resultant effect on phase equilibria of major phases. Saturating apatite can alter phase equilibria, mainly for calcium-bearing phases, that is equivalent to up to 20°C change in temperature. Modelling results for the Peninsula Pluton predicts LREE concentrations of apatite and monazite that match the natural samples at temperatures below 725°C, corroborating previous findings for emplacement P-T constraints. However, phase assemblages predicted through phase equilibria modelling show that the rock equilibrated to P-T below the emplacement estimates of previous studies. By modelling both major and accessory phases we provide constraints on the formation and crystallisation of crustal magmas which has important implications on geothermobarometry and thermochronology in the crust.

Apatite geochemistry as a proxy for porphyry-skarn Cu genesis: a case study from the Sanjiang region of SW China

In view of the importance of the magmatic oxidation state and volatile composition (H2O-S-Cl) in porphyry Cu mineralization, identification of magmatic information has become the basis for the evaluation of the Cu-mineralization potential of porphyries. Apatite, as a common accessory mineral in porphyry, is recognized as an effective petrogenetic and metallogenic indicator. In this study, we analyze the in situ major and trace elements and Nd isotope content of apatite from four granitic plutons in the Yidun Terrane, SW China, in order to provide new insights into the identification of the magmatic features of Cu-mineralized plutons. The plutons investigated in this study are a Cu-mineralized pluton (Hongshan) and three non-mineralized plutons (Cilincuo, Rongyicuo, and Hagela). Chemical composition and textural analysis indicate that the apatites are all of magmatic origin and have not been altered. Our results show that apatite δCe values rather than δEu and Ga values are more valid indicators of the magma oxidation state of the four plutons. Based on apatite δCe values and zircon compositions, the parental magma of the Hongshan pluton is identified as having been more oxidized than those of the other three plutons. Moreover, the higher Cl content (0.06–0.23 wt%) in the Hongshan apatite compared to that in apatite from the other three plutons (0.01–0.09 wt%), indicates that the parental magma of the former pluton was more enriched in Cl. Apatite from the Hongshan pluton contains more SO3 (average 0.05 wt%) than that from the other three plutons (SO3 content mostly lower than the detection limit of electron probe micro-analysis), which may be related to higher magmatic oxygen fugacity of the Hongshan pluton. In addition, the Nd isotopic composition of apatite [εNd(t): −13.6−5.9] demonstrates that the Cu-mineralized and non-mineralized plutons were derived from the melting of ancient lower crust. Furthermore, based on the geochemical signature of adakite revealed by apatite Sr/Y and δEu values, the Hongshan pluton can be considered to have been produced as the result of partial melting of the thickened lower crust. Finally, an index system consisting of apatite δCe, Sr/Y, and F/Cl values is established to distinguish between the Cu-mineralized and non-mineralized plutons.

Contraints on Petrogenesis and Fe Fertility of Intrusive Complexes in the Han–Xing Region, North China Craton from Apatite Geochemistry

The Han–Xing (Handan–Xingtai) region is famous for its endowment of skarn iron deposits in China. These deposits are mainly spatially and genetically associated with diorite rocks, but these rocks show different Fe ore potential. Major and trace elements composition of apatite from the Kuangshan and Fushan diorite complexes were investigated to explore the potential of apatite as a proxy of petrogenesis and Fe fertility of these rocks. All the investigated apatite grains are identified as fluorapatite, which is typical for magmatic apatite. The Sr, Y, Mn, and Heavy Rare Earth Elements (HREE) contents of apatite in the Kuangshan diorite complex are positively correlated with the increase of melt SiO2 content compared to that in the Fushan diorite complex. Apatite geochemistry indicates that magmas of the Fushan complex mainly experienced the fractional crystallization of hornblende in the deep crustal reservoirs, whereas the Kuangshan complex has experienced the fractional crystallization of hornblende in the deep and the shallow plagioclase fractional crystallization. The F, Cl and S content of the Kuangshan complex estimated by apatite volatile (F = 2632 ppm, Cl = 4100 ppm, SO3 = 140 ppm) is significantly higher than that of the Fushan complex (F = 2488 ppm, Cl = 3400 ppm, SO3 = 90 ppm). The Eu, Ce anomalies, Mn, and SO3 contents of apatite show that both of the two complexes have higher oxygen fugacity (Δ FMQ), but the oxygen fugacity of the Kuangshan complex calculated by Mn and SO3 content (Δ FMQ + 2.41) is higher than that of the Fushan complex (Δ FMQ + 1.77), which may also be one of the reasons for the great difference in ore-forming scale between the two complexes. Our results suggest that the high volatile contents and oxidation states of magma estimated by apatite, as well as the lower Sr/Y in apatite reflect favorable conditions for skarn iron mineralization. Therefore, our study shows that magmatic apatite geochemistry may be a useful tool to distinguish the Fe fertility of plutonic rocks related to skarn deposits.

APATITE VOLATILE CONTENTS OF PORPHYRY Cu DEPOSITS CONTROLLED BY DEPTH-RELATED FLUID EXSOLUTION PROCESSES

Abstract Porphyry Cu deposits are formed by Cu- and volatile (e.g., Cl, S)-rich fluids exsolved from underlying magma reservoirs. Intuitively, higher magmatic Cl and S contents likely correspond to higher magma fertility. However, the Cl contents of syn-ore magmatic apatite, one of the major Cl-bearing mineral phases in magmas, are highly variable among deposits (from &amp;lt;0.1 to &amp;gt;2 wt %). These variations may be controlled by different timing of apatite crystallization relative to fluid saturation among deposits, but the causes of these different relative timings remain obscure. Here we compile existing chemical data of magmatic apatite and amphibole phenocrysts from 25 porphyry Cu deposits worldwide and use these data to calculate magmatic physical-chemical conditions, such as water contents and magma reservoir depths. We find that the porphyry Cu deposits associated with deeper magma reservoirs are characterized by systematically higher magmatic H2O contents and apatite Cl, but lower apatite F contents and F/Cl ratios compared to shallower deposits. These correlations are best explained by early fluid exsolution and Cl loss that predate apatite crystallization in shallower porphyry Cu systems, which leads to elevated apatite F/Cl ratios. This is supported by the common occurrence of primary fluid inclusions in apatite from shallower systems. Postsubduction porphyry Cu deposits are normally associated with lower apatite Cl contents and shallower magma reservoirs, which is attributed to their formation under relatively extensional tectonic regimes. Our results demonstrate that the magma reservoir depth exerts an important control on the timing of fluid exsolution and accompanying Cl loss. In contrast, relatively high and constant apatite S content among deposits is minimally affected by fluid exsolution, possibly due to buffering of early-saturated sulfate in oxidized and S-rich magmas, and therefore might be used as a better potential fertility indicator than Cl.

Separation of Rare Earth Elements from Phosphogypsum Obtained from the Processing of Apatite Concentrate from the Chadormalu Mine by Acid Leaching

Separation of Rare Earth Elements from Phosphogypsum Obtained from the Processing of Apatite Concentrate from the Chadormalu Mine by Acid Leaching

Apatite and Biotite in Syenitic Intrusions, Archean Karari Gold Deposit: Evidence for an Oxidized Magma and Oxidized Subsolidus Potassic (Biotite) Alteration

Abstract Apatite and biotite from syenitic intrusions at the Karari gold deposit, Kurnalpi Terrane, Archean Yilgarn Craton, Western Australia, were targeted for microprobe and LA-ICP-MS analyses in order to determine some parameters (e.g., temperature, oxygen fugacity) during magmatic crystallization and potassic (biotite) hydrothermal alteration. The understanding of magmatic conditions is limited by the almost complete hydrothermal modification of magmatic minerals but made possible by the analysis of refractory magmatic apatite and rare relics of Ba-rich biotite. The SO3 contents of apatite cores (up to 1 wt.%) indicate that the syenitic magmas were strongly oxidized (fO2 &amp;gt; NNO +1) and contained approximately 1360 ppm S. The Cl contents of apatite are very low, suggesting crystallization from a low-Cl magma resulting from early separation of a volatile phase that sequestered Cl from the magma. Trends defined by wt.% SO3, at constant XF/XCl, are consistent with partitioning of oxidized S into the volatile phase during apatite crystallization. Early potassic alteration of the syenitic intrusions produced fine-grained seams of hydrothermal biotite and compositional modifications of igneous biotite phenocrysts. The magnesian composition of the hydrothermal biotite (mg# &amp;gt; 0.5) suggests that oxidized magmatic conditions persisted during potassic alteration. Provinciality of compositional data for different intrusion samples suggests that potassic alteration took place at low fluid:rock ratios. The potassic hydrothermal fluid modified the rims of igneous apatite crystals, depleting them in F, light rare earth elements, Mn, and S. The rare earth elements were rapidly redeposited, as monazite, in the apatite rims or surrounding groundmass. The depletion of S in apatite rims indicates that the potassic (biotite) alteration fluid was under-saturated in S. Application of the biotite-apatite geothermometer suggests potassic (biotite) alteration took place at temperatures of about 660 °C. The results of this study suggest the syenitic magmas at Karari were strongly oxidized, similar to Canadian examples of syenite-associated gold deposits, and therefore potentially fertile for hydrothermal gold.

Age and petrogenesis of Ni-Cu-(PGE) sulfide-bearing gabbroic intrusions in the Lausitz Block, northern Bohemian Massif (Germany/Czech Republic)

The Lausitz Block, located in the northernmost part of the Bohemian Massif, hosts a large number of dike- to stock-shaped gabbroic intrusions that mainly comprise brown hornblende-poor (Group I; i.e. olivine gabbronorite, olivine gabbro, gabbro and diorite) and subordinately brown hornblende-rich lithologies (Group II; i.e. olivine-hornblende gabbro and hornblende gabbro). Several of these intrusions host small-scaled magmatic Ni-Cu-(PGE) sulfide accumulations. The intrusions are part of interconnected mafic–(ultramafic) plumbing systems that intruded Cadomian granodiorites of Lausitz Block in the Middle to Late Devonian during the early stages of the Variscan Orogeny. The previously inferred Devonian age of the intrusions is refined by biotite Ar-Ar dating that yield ages between 389.1 ± 3.9 Ma and 372.2 ± 3.7 Ma (2σ). Group I and Group II lithologies differ in their mineralogical and geochemical composition. Compared to the Group I lithologies those of Group II are characterized by higher modal contents of primary brown hornblende, Fe-Ti oxides and apatite, by Ti- and Al-enriched clinopyroxene and by lower contents of SiO2 and increased contents of TiO2, P2O5, LILE, HFSE and LREE. The differences suggest at least two different magmatic series where Group I rocks are linked to tholeiitic basaltic magmas with low to moderate Ti and volatile contents, whereas Group II rocks are derived from Ti- and volatile-enriched alkaline basaltic magmas. The magmas experienced clinopyroxene fractionation during their crustal ascent and storage, but were only minor affected by crustal contamination (< 5%) according to Sr-Nd-Pb isotope systematics. The tholeiitic and alkaline basaltic magmatism could be explained by a tectonic environment between a subduction and intraplate setting. Group II rocks have an intraplate chemical signature and their parental magmas are clearly originated from a deeper-seated mantle source with melting of garnet peridotite, likely associated with an asthenospheric upwelling. By contrast, precursor magmas of Group I rocks are originated from partial melting of a less-enriched source, presumably spinel peridotite, from a subduction-related environment. Trace elements systematics suggest that both groups at least partly resulted from an interaction (mixing) of the alkaline and tholeiitic magmas. Partial melting estimates for both groups vary between 5 and 20%. The proposed tectonic setting could have been related to a subduction slab retreat within the framework of the Variscan orogeny, which led to an upwelling of the asthenospheric mantle. Cu/Zr ratios <1 of gabbroic rocks from several intrusions suggest a previous segregation of magmatic sulfides in other sections of the magmatic plumbing system and give rise for a vertical and lateral Ni-Cu exploration potential.

The Phosphorus Budget of the Silicate Earth Based on an Updated Estimate of the P/Nd Ratio

AbstractCalculating the phosphorus (P) budget of the bulk silicate Earth (BSE) is necessary to understand the global P cycle and the origin and evolution of life. Covariations of P and neodymium (Nd) contents suggest that P is 1.1–1.4 times more incompatible than Nd during mantle melting and magmatic differentiation. As such, the P/Nd ratios of mantle sources can be estimated using inverse modeling, and the P budget of the BSE can be calculated from the P/Nd ratios of the continental crust, mid‐ocean ridge basalts (MORBs), and ocean island basalts (OIBs). The P/Nd ratios for the MORB and OIB mantle sources and continental crust are 62.5 ± 0.8 (2σm), 57.0 ± 0.5 (2σm), and 28.4 ± 12.0 (2σm), respectively. These reservoirs have different P/Nd ratios due to subduction, magmatic differentiation, and mineralogy. Subduction can significantly affect the global P and Nd cycles. Magmatic differentiation, especially in the continental crust, may redistribute P by changing the contents of garnet, apatite, and other minerals. The fractional contributions of these global reservoirs suggest the modern BSE has a P/Nd ratio of 57.7 ± 3.0 (2σm), equating to ∼3.1 × 1020 kg of P in the BSE.