Secondary Phosphate Minerals Research Articles

Phosphate sequence study of Boqueirão pegmatite (Rio Grande do Norte state, Brazil)

O pegmatito Boqueirão localiza-se naProvíncia Pegmatítica daBorborema, no estado do Rio Grande do Norte (Nordeste do Brasil), encontra-se encaixado em metaconglomerados de idade neoproterozóicada Formação Equador. Trata-se de um pegmatito zonado concentricamente, exibindo diferentes zonas caracterizadas por suas mineralogias. As zonas de contato e de parede são compostas essencialmente por quartzo, microclina e moscovita exibindo muitas vezes texturas esqueléticas e gráficas, e,tendo como minerais acessórios a turmalina e a granada. A zona intermediária é dividida em duas subzonas distintas e mostra uma mineralogia diversa exibindo uma complexa associação de fosfatos, berilo, columbita-tantalita e zircão. A zona mais interna é principalmente constituída por um núcleo de quartzo. Além disso, observa-se corpos de substituição típicos, constituídos por albita,situados na parte oriental do corpo. Litofilita - triplilita representa a fase de fosfato mais abundante exibindo exsoluções de sarcopsida e substituição por sicklerita, resultante da alteração por Li- lixiviação, mais conhecida como Série de Quensel-Mason. A ausência de membros da série heterosita-purpurita é notável. Fosfatos primários, tais como montebrasita e triplita são também observados. Subsequentemente, a presença de alluaudita e varulita sugere que o pegmatito foi submetido a metassomatismo sódico.Toda esta assembléia de minerais sofreu uma extensa alteração que levou a cristalização de fosfatos secundários. Dados de microssonda eletrônica em trifilita-litiofilita revelam razões Mn/(Mn + Fe) entre 0,21-0,24 e também até 0,72 que sugerem um magma de origem pouco fracionado; consequentemente, a ferrisicklerita mostra valores de Mn/(Mn + Fe)entre 0,69-0,77, característicos de elevado grau de evolução, sugerindo que o pseudomorfismo foi produzido por uma elevada interação entre rocha/fluido. Alluaudita e varulita também revelam conteúdos de Mn e Fe até 0,71 semelhantes aos fosfatos precursores. Além disso, oito diferentes fosfatos secundários foram identificados substituindo fases primárias, quer como pseudomorfos ou cortando-as. Ocorrem como cristais euédricos de grã fina, esferulíticos ou maciços, com cores vivas facilmente identificados. As fases secundárias ricas em Mn são hureaulita, eosphorita, whiteita, jahnsita e serrabrancaita, enquanto que lipscombita, phosphosiderita e mitridatita correspondem a associação secundária rica em ferro (Fe). A origem supergênica tardia e a entrada fluidos ricos Ca, K e Mg procedentes da rocha hospedeira são sugeridos como responsáveis pela formação destes fosfatos. Não há quaisquer feições que os correlacionem a cristalização do pegmatito. O conteúdo de Háfnio (Hf) de zircões encontrados na zona intermediária tem sido analisado por microssonda eletrônica, e, usado como um poderoso indicador do grau de evolução do pegmatito, juntamente com o conteúdo de Mn dos fosfatos. O conteúdo Hf obtido é baixo chegando até 5% em peso de HfO2, que revela um magma pegmatítico pouco fracionado. Além disso, a presença de silicatos ferromagnesianos que constituem a mineralogia de zonas do pegmatito, como a turmalina rica em Fe, a granada e o berilo verde está de acordo com esta hipótese. Portanto, o Pegmatito Boqueirão corresponde a um pegmatito de elementos raros subtipo berilo-columbita-fosfato.

Restrictions of Weathering on Phosphorus Migration and Enrichment of the Lower Cambrian Phosphorus-Bearing Rock Series in Eastern Guizhou.

Phosphorite deposits in eastern Guizhou belong to a typical type of marine sediments. Phosphorus-bearing layers are distributed at the bottom of the Lower Cambrian Niutitang Formation. Generally, the average content of P2O5 in phosphorite deposits is 13.01%. In this study, significant P enrichment on or near the phosphorite deposit surface was found, and the average content of P2O5 reached 24.76%. However, the migration and enrichment mechanisms of P in the supergene environment still lack in-depth research. Therefore, in this work two representative phosphorite deposits, namely, primary sedimentary and weathered phosphate ores, were analyzed. The deposits were examined by polarized light microscope observation, X-ray diffraction analysis, scanning electron microscope observation, energy spectrum analysis, and NMR analysis. Major, trace, and rare earth elements in the deposits were detected by geochemical tests. The results showed that, compared with the primary phosphate ore, the porosity of the weathered phosphate ore was significantly increased. The NMR T 2 spectrum showed that the number of micropores increased, the pore size was enlarged, and more mesopores and macropores appeared in the weathered phosphate ore. The weathered phosphate ore had a lighter color than the primary phosphate ore. Under the action of aqueous acid, the primary phosphate minerals (collophosphate and apatite) and Al-bearing rocks transformed into a typical weathered mineral, sasaite. Carbonate minerals were dissolved, and pyrite was oxidized to limonite. K, Si, and Al in silicate minerals precipitated to form secondary clay minerals, such as kaolinite. The weathered phosphate ore developed recrystallized, pisolitic, and pseudomorphic textures and nodular, oriented, and metacolloidal structures, features specific to a weathered mineral. In the supergene environment, soluble components such as carbonate minerals in the primary rock were leached out, while residual P2O5 with relatively stable chemical properties was enriched in situ. Phosphorus migration and enrichment were restricted by such factors as primary rock/ore composition, primary rock/ore texture and structure, climatic conditions, topography, geological structure, and hydrogeological conditions. A three-stage enrichment model was established after mechanical crushing of the primary rock/ore, carbonate mineral dissolution, and secondary phosphate mineral formation.

Ornithogenesis and soil-landscape interplays at northern Harmony Point, Nelson Island, Maritime Antarctica.

Understanding the influence of soil-forming factors and processes in ornithogenic soils is important to predict impacts of climate change on Antarctic ecosystems. Herein, we analyzed the soil-landscape interplays and development of ornithogenic soils at Harmony Point (HP), Nelson Island. We collected, described, and classified 24 soil profiles, combined with vegetation and landforms descriptions. Geoprocessing techniques were employed for mapping. Soil physical, chemical, geochemical, and mineralogical analyses were applied. Patterned ground, "Ornithogenic"/Typic Gelorthent, and moss carpets were the dominant landform, soil and vegetation classes, respectively. Soils from rocky outcrops were more structured, acidic, with higher organic carbon, organometallic complexes, and secondary phosphate minerals, due to former bird influence. Soils from cryoplanated platforms presented higher water pH, base saturation, clay content, and secondary silicate minerals. Soils from marine terraces presented high exchangeable bases, phosphorous, and amorphous phosphate minerals. Soil chemical weathering is enhanced by ornithogenesis and widespread in HP. Besides ornithogenesis, organic matter accumulation, cryoturbation, and cryoclastic processes are also important to pedogenesis of ornithogenic soils. The soils of the cryoplanated platforms exhibited a gradient of pedogenetic development corresponding to increasing biota influence and distance from glacier. In contrast, soils of rocky outcrops were more developed even close to the glacier, due to ornithogenesis.

Organophosphorus Compound Formation Through the Oxidation of Reduced Oxidation State Phosphorus Compounds on the Hadean Earth.

Reduced oxidation state phosphorus compounds may have been brought to the early Earth via meteorites or could have formed through geologic processes. These compounds could have played a role in the origin of biological phosphorus (P, hereafter) compounds. Reduced oxidation state P compounds are generally more soluble in water and are more reactive than orthophosphate and its associated minerals. However, to date no facile routes to generate C-O-P type compounds using reduced oxidation state P compounds have been reported under prebiotic conditions. In this study, we investigate the reactions between reduced oxidation state P compounds-and their oxidized products generated via Fenton reactions-with the nucleosides uridine and adenosine. The inorganic P compounds generated via Fenton chemistry readily react with nucleosides to produce organophosphites and organophosphates, including phosphate diesters via one-pot syntheses. The reactions were facilitated by NH4+ ions and urea as a condensation agent. We also present the results of the plausible stability of the organic compounds such as adenosine in an environment containing an abundance of H2O2. Such results have direct implications on finding organic compounds in Martian environments and other rocky planets (including early Earth) that were richer in H2O2 than O2. Finally, we also suggest a route for the sink of these inorganic P compounds, as a part of a plausible natural P cycle and show the possible formation of secondary phosphate minerals such as struvite and brushite on the early Earth.

Supergene Turquoise and Associated Phosphate Minerals of the Porphyry-Lode System at Butte, Montana, USA

ABSTRACTWeathering processes superimposed onto exhumed hydrothermal ore deposits in western North America have developed secondary mineral assemblages that inform the near-surface evolution of these systems within the context of Basin and Range extension. The occurrence of the secondary phosphate mineral turquoise [CuAl6(PO4)4(OH)8·4H2O] in the weathering profile of Laramide porphyry copper deposits is widely documented, although previous studies on the composition and distribution of turquoise are largely restricted to the archaeological literature. In this study, we use the world-class Butte porphyry-epithermal system to study the occurrence, paragenesis, and mineral chemistry of turquoise and related phosphates in the weathering profile of the deposit. Field observations, mineral textures by optical microscopy, electron microprobe analyses, and geochemical modeling show that blue, Al-endmember turquoise formed exclusively at or immediately below the pre-mining water table, within the chalcocite enrichment blanket and in the absence of significant FeIII. At higher structural levels above the pre-mining water table, green FeIII-bearing turquoise [Cu(Al,FeIII)6(PO4)4(OH)8·4H2O] is commonly intergrown with jarosite and/or tinticite at the micron scale. We show that jarosite, tinticite, and FeIII-bearing turquoise formed at the expense of pre-existing, Al-endmember turquoise after extensional faulting caused a relative lowering of the water table in the eastern fault block of the deposit. The low solubility of the FeIII-phosphates tinticite and strengite in the leach cap environment suggests that it is unlikely that these minerals formed directly from oxidized meteoric water. Electron probe microanalysis documented the presence of As and F in blue Al-endmember turquoise and Cl in green FeIII-bearing turquoise. The presence of Cl in FeIII-bearing turquoise may represent an evaporitic signal associated with basin development as the Butte district was exhumed. The paragenesis of Cu- and Fe-phosphate minerals provides another tool with which to interrogate spatial and temporal relationships in the near-surface evolution of porphyry copper systems.

New secondary phosphate mineral occurrences and their crystal chemistry, at the Hagendorf Süd pegmatite, Bavaria

Abstract. First occurrences from the Hagendorf Süd pegmatite of the secondary phosphate minerals kenngottite, Mn32+Fe43+(PO4)4(OH)6(H2O)2; allanpringite, Fe33+(PO4)2(OH)3 ⚫ 5H2O; iangreyite, Ca2Al7(PO4)2(PO3OH)2(OH,F)15 ⚫ 8H2O; and nizamoffite, MnZn2(PO4)2(H2O)4, are reported with characterisation of their crystal chemistry and phase associations. A synchrotron single-crystal structure refinement for kenngottite shows that it has the same level of disordering (75 %/25 %) of Fe3+ in adjacent octahedra along the 5 Å axis as for type-locality kenngottite from Krásno, Czech Republic. This is explained in terms of 1 : 1 fine-scale mixing of domains of ordered kenngottite-type and souzalite-type structures. Allanpringite occurs in an unusual epitaxial relationship to associated strunzite. The epitaxy is explained by the close metrical and structural match of common planes in the two minerals, (010) for allanpringite and (100) for strunzite. Iangreyite occurs in close association with perhamite in 30 µm spheroids. The characterisation results support a paragenesis of iangreyite from perhamite by selective leaching of silica from the layer structure of perhamite and rejoining of the layers by fusion of AlO4 tetrahedra from adjacent layers into AlO2(OH)3 trigonal bipyramids.

Tomsquarryite, NaMgAl3(PO4)2(OH)6 ● 8H2O, a new crandallite-derivative mineral from Tom's phosphate quarry, Kapunda, South Australia

Abstract. Tomsquarryite, NaMgAl3(PO4)2(OH)6 ⚫ 8H2O, is a new secondary phosphate mineral from Tom's phosphate quarry, Kapunda, South Australia. It occurs as colourless, talc-like hexagonal platelets, with diameters of a few tens of micrometres when formed from the decomposition of minyulite and as thicker (∼ 10 µm) hexagonal crystals when formed from alteration of gordonite. Associated minerals are penriceite, elliottite, minyulite, angastonite and wavellite. The calculated density is 2.22 g cm−3. Tomsquarryite crystals are uniaxial (+) with ω=1.490(3), ε=1.497(3) (white light). Dispersion was not observed. The partial orientation is Z≈c. Electron microprobe analyses of the holotype specimen give the empirical formula Na1.02K0.02Ca0.08Mg1.26Al2.86(PO4)2.00(OH)3.82F2.48 ⚫ 7.70H2O, based on 22 anions. Tomsquarryite belongs to the trigonal crystal system, space group R–3m, with hexagonal unit-cell parameters a=6.9865(5) Å, c=30.634(3) Å and V=1294.9(4) Å3 and with Z=3. The crystal structure was refined using single-crystal diffraction data; R1=0.069 for 303 reflections with I>2σ(I) to a resolution of 0.80 Å. The crystal structure is a derivative of the crandallite structure, with Ca2+ cations replaced by hydrated magnesium ions, [Mg(H2O)6]2+, resulting in an expansion of the interlayer separation from 5.4 Å in crandallite to 10.2 Å in tomsquarryite. The results for tomsquarryite are compared with those for the chemically and structurally related minerals penriceite and elliottite.

The phase transformation of microbial induced struvite and its Cd(II) immobilization mechanism

The research and development of high-efficiency biological mineral materials for the treatment of heavy metal pollution is key to the remediation of heavy metal pollution. Biogenic struvite (BS) was synthesized using microbial culture technique, and a batch adsorption experiments and mineral characterization methods were performed to evaluate the immobilization effect of BS on Cd(II) and the phase transformation in this process. The results show that Bacillus velezensis can regulate the synthesis of irregular BS containing about 14.21% organic matter in Luria-Bertani medium. The adsorption of BS on Cd(II) can be better fitted by the Langmuir equation (R2 = 0.9990), Qmax = 282.96 mg/g. The adsorption kinetics and hermodynamics show that the adsorption of Cd(II) by BS is a spontaneous exothermic chemisorption process with increased chaos. The adsorption capacity of BS on Cd(II) is always maintained at about 174.35 mg/g with pH ≥ 3. Furthermore, the part of Cd(II) combines with organic functional groups on the BS to form Cd-containing complexes or chelates, and another part of Cd(II) partially displaces Mg2+ and NH4+ from struvite crystals to form Cd-bearing phosphate minerals. In summary, the superior immobilization capacity of BS on Cd(II) is attributed to the organic-inorganic structure of BS, complexation or chelation effect, crystal ion exchange, phase transformation, and the formation of secondary phosphate minerals, which makes it difficult to desorb Cd(II). The results offer new ideas for the research and development of new materials for heavy metal pollution remediation.

The crystal structure and chemistry of natural giniite and implications for Mars

AbstractInvestigations of planetary processes using phosphate minerals often focus on igneous, recrystallized, or potentially metasomatized minerals, likely as a result of the minerals commonly available for study within meteorites and lunar samples. However, Mars is a relatively phosphorus-rich planet and possesses abundant evidence of past aqueous surface interactions. Therefore, secondary phosphate phases may be important on the martian surface. Giniite [Fe2+Fe43+(PO4)4(OH)2·2H2O] is a secondary phosphate mineral that has been suggested as a potentially significant phase at locations in Gusev Crater and Meridiani Planum on Mars. Although relatively rare as a natural mineral on Earth, giniite has gained attention as an important mineral in industry and technology, especially the lithium battery industry, and the ferrian version of the mineral is often synthesized. This suggests giniite may be important as an in situ resource utilization (ISRU) target for future extended human missions to Mars. Despite this, there are few data available on the natural mineral and the last characterization of the structure was over 40 years ago. There has also been confusion in the literature as to whether giniite is orthorhombic or monoclinic. In this work we revisit and document the chemistry and crystal structure of natural giniite from the type locality at the Sandamab pegmatite in Namibia using updated techniques. Our results refine and update what was previously known regarding the structure and chemistry of giniite and support the potential of the mineral as a possible martian scientific and resource target for further study to aid future missions.

Magnesiobermanite, MgMn3+2(PO4)2(OH)2⋅4H2O, the Mg analogue of bermanite: Description and crystal structure

ABSTRACTMagnesiobermanite, MgMn3+2(PO4)2(OH)2⋅4H2O, is a new secondary phosphate mineral and the Mg analogue of bermanite found in a granitic pegmatite at the White Rock No.2 quarry situated in the Bimbowrie Conservation Park, South Australia, Australia. Magnesiobermanite occurs as aggregates of twinned, bladed to tabular crystals, up to 1.2 mm across. Individual crystals are up to 0.3 mm in length. The crystals are orange–red to brownish red, with a vitreous lustre and a salmon-pink streak. The mineral is brittle with a conchoidal fracture and a good cleavage on {100}. The mineral is biaxial (–), with α = 1.690(2), β = 1.719(2) and γ = 1.734(2) (white light). The calculated 2V is 70.4°. Electron microprobe analyses provided: MgO 9.59, Mn2O3 27.41, Fe2O3 8.84, Al2O3 0.18, P2O5 33.27, H2O 20.94, total 100.23 wt.%. The empirical formula (based on 14 O atoms) is: Mg1.02(Mn3+1.49Fe3+0.47Al0.02)1.98(PO4)2.01(OH)1.95⋅4.01H2O. Magnesiobermanite is monoclinic, space group P21, with the unit-cell parameters: a = 5.4215(11), b = 19.072(4), c = 5.3889(11) Å, β = 110.21(3)°, V = 522.89(18) Å3 and Z = 2. The crystal structure was refined to an R1 index of 2.43% based on for 3222 observed reflections with Fo > 4σ(Fo). Magnesiobermanite is isostructural with bermanite, Mn2+Mn3+2(PO4)2(OH)2⋅4H2O, from which it derives its name. The structure is based upon a sheet of the form [(M(OH)2(PO4)2] in the (010) plane. Sheets are linked in the b direction by [M3(H2O)4O2] octahedra and by hydrogen bonds.

Crystal structure determination of orthorhombic variscite2Oand its derivative AlPO4 structure at high temperature

AbstractVariscite [Al(PO4)·2H2O] is an uncommon secondary phosphate mineral but is important in a variety of environmental and technological applications. It exists in at least one monoclinic (metavariscite) and two orthorhombic polymorphs (“Lucin-type” and “Messbach-type”), but the fine-grained nature of the “Messbach-type” variscite has hampered the determination of its crystal structure. The crystal structure of the latter from Tooele County, Utah, was solved and refined using laboratory powder X-ray diffraction (XRD) data, charge-flipping, and the Rietveld method. Both variscite modifications belong to the family of framework 3D MT structures in which octahedra (M) and tetrahedra (T) are linked by bridging O atoms. Topological analysis reveals that the two structures are polytypes. Based on our results and our structural interpretations, we refer to “Lucin-type” variscite as variscite1O and the “Messbach-type” as variscite2O, to be consistent with modern polytype terminology. The similarity of these two structures suggests that 1O-2O interstratifications may exist in nature, which is consistent with observed broadening of diffraction peaks of the Tooele material. 31P and 27Al MAS/NMR measurements are consistent with the XRD-determined crystal structure, and they show distinct signals for each of the two independent P and Al positions in variscite2O.High-temperature XRD, thermal analyses, and NMR measurements were applied to study the nature of the transformation of variscite2O to a derivative AlPO4 structure above 473 K. Charge-flipping analysis showed that the crystal structure of the new anhydrous AlPO4 phase (AlPO4-var2O in analogy to its parent structure) can be described as a 3D framework of alternating AlO4 and PO4 tetrahedra linked by bridging O atoms. Thermogravimetric analyses revealed almost complete dehydration above ~450 K, and NMR results were consistent with tetrahedral Al and P atoms.

Structural, chemical and isotope evidence for secondary phosphate mineralization of grasping spines of Early Palaeozoic chaetognaths

Microscope, cathodoluminescence, chemical and oxygen isotope studies have been conducted to determine the original mineralogy and diagenetic alteration of phosphatic grasping spines of Cambrian chaetognaths. The obtained data, along with a comparison to the composition of conodont apatite, show the presence of a few generations of diagenetic phosphate phases. A thin, outer layer of the spines is composed of very early diagenetic phosphate, which incrusted the original cuticle layer contributing to the preservation of an original shape and structural details of the fossils. This process can be linked to the ‘Orsten’-type phosphatization mainly known from Lower Palaeozoic strata. Successive phosphate generations are observed within the middle and inner layers as well as internal cavities of the spines. Plastic deformations and diagenetic features of the spines show that they were originally composed of slightly flexible chitinous organic matter similar to that of modern chaetognaths. This conclusion is substantiated by rare findings of purely organic remnants of Cambrian chaetognath grasping spines.

Rare Earth elements in rocks and soil profiles of a tropical volcanic archipelago in the Southern Atlantic

Rare earth elements (REEs) concentration and signature in soils are influenced by parent material and pedogenesis, but little information is available on the potential of REEs to trace pedogenetic processes in tropical volcanic soils. The archipelago of Fernando de Noronha, Brazil, represents a mostly pristine environment with a diversity of parent materials varying from ultrabasic igneous to sedimentary rocks. Here, we collected nine soil profiles to study the parent materials' petrography and the chemistry of soils from the archipelago to interpret the signature and fractionation of REEs in soils along a volcanic lithosequence. Besides, soil guideline values (SGVs) for REEs were established in the soils of the archipelago. REEs in the rocks were found mainly in mafic and accessory minerals such as apatite, allanite, monazite, nepheline, clinopyroxene, and olivine. Owing to the higher amounts of mafic minerals in the ultrabasic rocks, the total REE content in the parent materials followed the order: basanite / ankaratrite > ankaratrite > phonolite > sedimentary deposits of marine origin. Likewise, the REE mean contents in soil profiles diminished in the order: Cambisols (339 mg kg−1) > Vertisols (227 mg kg−1) > Arenosol (68 mg kg−1). The SGVs for REE (mg kg−1) were Ce (165.7), La (83.1), Nd (55.0), Pr (17.0), Sm (11.2), Dy (9.9), Gd (4.3), Ho (2.9), Er (2.4), Tb (1.8), Yb (1.6), and Lu (0.6). Although the composition of parent materials was crucial for the differentiation of REEs, pedogenesis altered the accumulation and distribution of REEs in soils substantially. Thus, REE signatures of parent rocks were maintained in the soils, but concentration and stability of secondary phosphate minerals and iron oxides controlled the REE fractionation in the soil profiles.

Cycling phosphorus on the Archean Earth: Part II. Phosphorus limitation on primary production in Archean ecosystems

Several lines of evidence point to low rates of net primary production (NPP) in Archean oceans. However, whether Archean NPP was limited by electron donors or nutrients, particularly phosphorus (P), and how these factors might have changed over a billion years of recorded Archean history, remains contentious. One major challenge is to understand quantitatively the biogeochemical cycling of P on the early Earth. In Part I of this series (Hao et al., 2020), we estimated the weathering flux of P to the oceans as a function of temporally increasing continental emergence and elevation through Archean time. In Part II, we conduct thermodynamic and kinetic simulations to understand key processes of P cycling within the Archean ocean, including seafloor weathering, recycling of organic P, the solubility and precipitation of secondary phosphate minerals, and the burial diagenesis of P precipitates. Our calculations suggest low solubilities of apatite minerals in Archean seawater, primarily due to nearly neutral pH and high levels of Ca. This low solubility, in turn, implies a negligible contribution of apatite dissolution to P bioavailability in Archean seawater.We also simulate the solubility limits of common secondary P-bearing minerals, showing that vivianite would have been the least soluble P mineral in ferruginous Archean seawater (0.1–0.3 µM), even at moderate supersaturation states (Ω = 100 or 1000). If vivianite precipitation was kinetically favorable by microbial activities and mineral adsorption, the sinking flux of P as vivianite in Archean seawater could have reached the modern sinking flux, implying that vivianite precipitation was a potentially major sink for P in Archean oceans. During burial diagenesis, however, vivianite in porewater would have become less stable than Ca-phosphates of lower solubility. At elevated temperatures (>100 °C) associated with burial diagenesis and low-grade metamorphism, vivianite is predicted to react irreversibly with calcite to form apatite.Optimistic assumptions about the recycling efficiency of P on the Archean Earth lead us to estimate that by the end of the eon the total flux of P (continental weathering + recycling) could have supported NPP at levels up to 7% of the modern. The total flux of P would have been much lower on the early and middle Archean Earth, whereas fluxes of electron donors could have been higher, suggesting very low productivity and P-limitation of marine ecosystems during much of the eon. Comparing our estimates of NPP as limited by P supply with the estimate by Ward et al. (2019), in which NPP was limited by electron donors and metabolic efficiency, there could have been a transition between P-limited productivity in the early to middle Archean to electron donor-limitation closer to the eon’s end (assuming no oxygenic photosynthesis). Once oxygenic photosynthesis reached ecological significance, probably near the end of the Archean, our estimated flux of P would allow rapid oxidation of atmosphere.

Mineralogy and genesis of rare Al-phosphate minerals in weathered itabirite and iron ore from the Quadrilátero Ferrífero, Minas Gerais, Brazil

Phosphorus is a major deleterious element in iron ore where it occurs as primary apatite in hypogene ore, and adsorbed into Mn-, Fe-hydroxides and forming secondary phosphates in supergene ore. Secondary phosphate minerals have been formed during a long history of weathering of itabirite and hypogene iron ore in the Quadrilátero Ferrífero (QF), ongoing since the end of the Cretaceous (~70 Ma). The distribution and genesis of these secondary phosphates are poorly documented in the literature. The purpose of this study was to investigate the mineralogy, mineral chemistry and formation of rare secondary phosphate minerals found in P-bearing concretions hosted in the iron ore at the Serra do Curral, QF. Detailed mineralogical investigation revealed that three generations of secondary phosphates were formed by weathering of carbonate veins hosted within fracture zones of itabirite and iron ore. Turquoise, augelite and senegalite comprise the bulk of the secondary phosphates whereas remnants of Ca-, Ba-, Ce- and Sr-bearing minerals (crandallite, gorceixite, florencite and goyazite) are subordinated. Sulphate members of aluminium-phosphate-sulphate (APS) minerals are absent, likely due to low SO42− activities in the weathering solution. Apatite hosted within unweathered itabirite and carbonate veins was the source of P to the weathering solutions whereas Cu, Zn and Ba were released from sulphides hosted in carbonate veins and Al2O3 from country rocks. The link between the secondary phosphates to hydrothermal breccias and carbonate veins highlights the significance of hydrothermal fluids as a source of P in iron ore deposits. Furthermore, it brings attention to the structural control imposed on P-bearing minerals in these deposits. Geochemical modelling shows that the secondary phosphates were formed in response to changes in pH of the weathering fluids, providing an additional example to the literature about the application of secondary phosphate minerals as valuable trackers of paleoenvironmental weathering conditions.

TAPHONOMY OF THE LOWER JURASSIC KONSERVAT-LAGERSTÄTTE AT YA HA TINDA (ALBERTA, CANADA) AND ITS SIGNIFICANCE FOR EXCEPTIONAL FOSSIL PRESERVATION DURING OCEANIC ANOXIC EVENTS

ABSTRACTKonservat-Lagerstätten provide the most complete snapshots of ancient organisms and communities in the fossil record. In the Mesozoic, these deposits are rarely found in marine facies outside Oceanic Anoxic Event (OAE) intervals, suggesting that OAEs set the stage for exceptional fossil preservation. Although anoxia does not guarantee survival of non-biomineralized tissues or articulated skeletons, other OAE phenomena may promote their conservation. Here, we test this hypothesis with a taphonomic analysis of the Konservat-Lagerstätte in the black shales and siltstones of the Jurassic Fernie Formation at Ya Ha Tinda (Alberta, Canada). This deposit contains crustacean cuticles, coleoid gladii with ink sacs and mantle tissues, and articulated skeletons of fish, crinoids, and ichthyosaurs. The fossils were preserved in the Pliensbachian and Toarcian (Early Jurassic) when euxinic conditions were common in the area, in part, due to the ∼183 Ma Toarcian OAE. Some of the fossils contain carbonaceous material, but the majority consists of apatite minerals, and phosphatic gladii demonstrate that some animals were preserved through secondary phosphate mineralization. Phosphatization generally occurs within phosphate-rich sediment, but oceanic anoxia causes sediment to release phosphorus and prevents animals from colonizing seafloor habitats. Accordingly, we propose that the animals were preserved during brief episodes of bottom water oxia and/or dysoxia, when the environment would have been most favorable to benthic communities and phosphate mineralization. In this setting, phosphatization may have been fueled by phosphate delivery from continental weathering in response to climatic warming, ocean upwelling of eutrophic water, and/or nutrient trapping by anoxia in the basin.

Connoisseur's Choice: Tarbuttite, Skorpion Mine, Lüderitz District, Namibia

Tarbuttite, Zn2(PO4)(OH), is a relatively rare secondary phosphate mineral that, according to Mindat.org (accessed April 2018), is currently known from only eight localities worldwide. From a conno...

Secondary Zn-bearing phosphate minerals associated with alteration of phosphophyllite at Hagendorf-Süd, Bavaria

Secondary Zn-bearing phosphate minerals associated with alteration of phosphophyllite at Hagendorf-Süd, Bavaria

Batagayite, CaZn2(Zn,Cu)6(PO4)4(PO3OH)3·12H2O, a new phosphate mineral from Këster tin deposit (Yakutia, Russia): occurrence and crystal structure

Batagayite, CaZn2(Zn,Cu)6(PO4)4(PO3OH)3·12H2O, is a new secondary phosphate mineral from the Kester deposit, Arga-Ynnykh-Khai massif, NE Yakutia, Russia. It is monoclinic, P21, a = 8.4264(4), b = 12.8309(6), c = 14.6928(9) A, β = 98.514(6)o, V = 1571.05(15) A3 and Z = 2 (from single-crystal X-ray diffraction data). Batagayite crystals are blades up to 2 mm long, flattened on {001} and elongated on [100]; blades often grow in radial aggregates. Associated minerals are arsenolite, native copper, epifanovite, fluorapatite, libethenite, Na-analogue of batagayite, pseudomalachite, quartz, sampleite, tobermorite, and Mg-analogue of hopeite. The streak is white and the luster is vitreous. The mineral is brittle and has a perfect cleavage on {001}, no parting was observed. The Mohs hardness is 3. Density, determined by the float-sink method in Clerici solution, is 2.90(3) g/cm3, and the calculated density is 3.02 g/cm3 (using the empirical formula and single-crystal unit-cell parameters). Batagayite is biaxial, optically negative, α = 1.566 ± 0.002, β = 1.572 ± 0.002, γ = 1.573 ± 0.002 at 589 nm. 2V meas. = 40(5)°, 2V calc = 44.3°. Optical orientation: Z is perpendicular to (001), further details unclear. No dispersion or pleochroism were observed. The mean chemical composition determined by electron microprobe is: Na2O 0.31, MgO 1.39, Al2O3 0.55, SiO2 0.48, P2O5 34.37, K2O 0.17, CaO 2.76, MnO 1.03, CuO 5.80, ZnO 35.62, CdO 0.24 wt%. The H2O content estimated from the crystal-structure refinement is 16.83 wt%, giving a total of 99.55 wt%. The empirical formula calculated on the basis of P + Si = 7 is (Zn6.22Cu1.04Ca0.70Mg0.49Mn0.21Al0.15Na0.14K0.05Cd0.03)Σ9.03(P6.89Si0.11)Σ7.00O24.91(OH)3.09·12.10H2O. The mineral easily dissolves in 10% room-temperature HCl. The eight diagnostic lines in the X-ray powder-diffraction pattern are (I-d[A]-hkl): 100-14.59-001, 25-6.34-012, 11-6.02-111, 37-4.864-003, 13-4.766-112, 20-3.102-1 $$\overline {2} \:\overline {4}$$ , 11-2.678-2 $$\overline {3} \:\overline {3}$$ , 16-2.411-044. The crystal structure of batagayite was solved by direct methods and refined to R 1 = 0.069 for 3847 independent reflections with F o > 4σ(F o). It is based upon complex heteropolyhedral [M 8(PO4)4(PO3OH)3(H2O)9]2− layers parallel to the (001) plane. The layer can be considered as consisting of three sublayers, one A and two B. The central A layer has the composition [M 4(PO4)4(H2O)4]4− and consists of the zigzag chains of edge-sharing (MO6) octahedra running parallel to the a axis and linked into layers by sharing peripheral O atoms. The (PO4) tetrahedra are attached above and below the holes created by the linkage of zigzag octahedral chains. The B sublayer consists of chains of (ZnO4) and (PO3OH) tetrahedra. The interlayer space is occupied by the Ca2+ cations and H2O molecules. Batagayite is a secondary low-temperature mineral formed as a result of alteration of primary minerals such as native copper and fluorapatite. On the basis of its structural complexity calculated as 1058.257 bits/cell (taking into account contributions from H atoms), batagayite should be considered as a very complex mineral. The high complexity of batagayite is due to its high hydration state and the modular character of its structure, which contains both octahedral-tetrahedral layers and tetrahedral chains.

Trace element composition and U-Pb age of zircons from Estherville: Constraints on the timing of the metal-silicate mixing event on the mesosiderite parent body

Mesosiderites are a group of stony-iron meteorites, which are thought to be the result of mixing of silicates with Fe-Ni metal. In this study, we combined textural observations with geochemical and chronological studies of two zircon grains found in the Estherville mesosiderite. One of the zircons (Zrc1) occurs with pyroxene, plagioclase, troilite, and silica, and the other (Zrc2) is located at a boundary between Fe-Ni metal and a silicate part mainly composed of pyroxene and plagioclase. The textural observations demonstrate that Zrc1 is relatively homogenous, whereas Zrc2 is composed of at least two chemically distinct domains. Trace element analyses of Zrc2 resolve large concentration gradients within this single grain with variations that are an order of magnitude for rare earth elements (REE) and two orders of magnitude for U and Th. The lowest trace element concentration in Zrc2 is more than an order of magnitude lower than those of lunar and eucritic zircons. However, it is similar to those of Zrc1 and a zircon from the Vaca Muerta mesosiderite. The calculated REE composition of the melt in equilibrium with Zrc2 shows that Zrc2 and perhaps also Zrc1 did not crystallize from a melt that was produced by fractional crystallization of the primary magmatic mineral assemblages. The zircons with low REE, U, and Th concentrations can be interpreted to have formed in a residual melt after incorporation of large amounts of REE, U, and Th into secondary phosphate minerals, which formed during the metal-silicate mixing event. The large concentration gradients observed in Zrc2 suggest significant heterogeneities in the melt from which the zircon crystallized. Alternatively, either mixing or diffusion between a relict zircon and a newly formed zircon could explain the observed concentration gradients. However, the REE patterns of Zrc2 cannot be explained by mixing or diffusion between the two distinct generations of zircons. These considerations suggest that Zrc1 and Zrc2 formed during a high-temperature reheating event, which is probably related to the metal-silicate mixing event. The weighted average 207Pb-206Pb age obtained by SIMS from both zircons is 4521±26Ma (2σ). This age is younger than that of a primary magmatic zircon from Vaca Muerta (4563±15Ma) and probably corresponds to the timing of the metal-silicate mixing event or a later impact event.