Rare Earth Elements In Apatite Research Articles

Geochemistry of color-zoned apatite from the Chadormalu iron oxide-apatite deposit, Central Iran: Insights into REE mobility during hydrothermal alteration

Apatite in the ‘Kiruna-type’ iron deposits is known as potential resource of rare earth elements (REEs). The present study describes large color-zoned apatite crystals in the Chadormalu magnetite-apatite deposit, Central Iran, to obtain insights into the behavior of REEs and trace elements during apatite mineralization and subsequent hydrothermal alteration. The zoned apatite consists of a beige-colored core and surrounding reddish and white polycrystalline domains. The beige-colored core is optically single crystals, but shows a replacement texture of the early-stage apatite (Ap-I) by the later-stage apatite (Ap-II) with abundant monazite inclusions. Ap-I is characterized by higher REEs, Y, Na, Si, S and Cl contents than Ap II. Both Ap II and reddish/white polycrystalline domains show similar compositions with very low contents of REEs and trace elements. These textural and chemical relations suggest that initial apatite mineralization (Ap-I) was followed by an intensive hydrothermal event, which has resulted in dissolution of Ap-I and precipitation of Ap-II and surrounding polycrystalline domains. REEs in Ap-I were leached into the fluid and precipitated as monazite inclusions in Ap-II and interstitial monazite in the reddish domain of polycrystalline apatite. Parts of REEs leached in the fluid are also incorporated into cores of the polycrystalline apatite. It is concluded that, although the later hydrothermal event remobilized REEs, it did not significantly affect the total REE budget of the investigated apatite-magnetite ore deposit.

Lanthanum Diffusion in Fluorapatite at 400 °C, 50 MPa and 4–16 wt %

Apatite is an important carrier of rare earth elements (REEs) and phosphorite is a potential REEs resource. However, the influence of hydrothermal fluids on the migration and enrichment of REE in apatite remains controversial. The experimental study of the interaction between REE-bearing fluid and apatite is one of the essential ways to understand the chemical behavior of rare earth elements in apatite. In this study, we conducted the fluid–mineral reaction experimental study (at 400 °C, 50 MPa and 4–16 wt %) between high lanthanum (La) content hydrothermal solution and low REE content to reveal the influence of different salinities on the diffusion of rare earth elements in fluorapatite. Based on in situ geochemical analyses of experimental products, we show that the diffusion coefficients of La in fluorapatite are between 3.24 × 10−15 and 5.88 × 10−15 m2/s. The salinity of the fluid has a great influence on the diffusion coefficient, with the increase of salinity, the diffusion coefficient increase.

Laser-induced time-resolved luminescence in analysis of rare earth elements in apatite and calcite

Laser-induced time-resolved luminescence was used to study rare earth element (REE) containing natural apatite and calcite minerals. The luminescence from 400 nm to 700 nm in the minerals was analyzed with excitation ranges 210–340 nm and 405–535 nm. As an outcome, several useful excitation wavelengths to detect one or more REE from apatite and calcite are reported. The feasibility of selected excitations in e.g. avoiding the disturbance of intense Mn2+ luminescence band, results was demonstrated with a non-gated detector.

Geochemical characteristics and significance of apatite from the Koktokay pegmatitic rare-metal deposit, Altay, Xinjiang

磷灰石可以记录和保存岩浆和热液活动的信息。可可托海伟晶岩型稀有金属矿床磷灰石发育，为研究该矿床伟晶岩成岩成矿过程提供了优良的条件。已有对可可托海伟晶岩型稀有金属矿床磷灰石的研究集中在其稀土元素特征，较少讨论其对伟晶岩成岩成矿过程的制约。本文选取可可托海伟晶岩型稀有金属矿床富矿伟晶岩脉（3号脉）和相对贫矿伟晶岩脉（1号、2b号和3a号脉）中的磷灰石作为研究对象，进行磷灰石岩相学和地球化学研究。岩相学分析表明，磷灰石主要与钠长石、石英、白云母、锰铝榴石等伴生。EPMA分析显示，磷灰石F含量为3.67%~4.41%，Cl含量小于0.67%，较低的Cl含量表明伟晶岩熔体出溶的流体Cl含量较低；大部分磷灰石MnO含量为4.67%~8.71%，但2b号脉磷灰石MnO含量变化较大（1.23%~14.28%），这是由于2b号脉磷灰石具有分带结构，暗示其遭受后期热液作用，促使磷灰石溶解-再沉淀，导致MnO含量发生较大变化。LA-ICP-MS分析显示，贫矿伟晶岩脉磷灰石的稀土元素含量较低（<180×10^-6）；相反，富矿伟晶岩脉磷灰石的稀土元素含量较高（>700×10^-6），并具有明显的四分组效应（TE_1-3平均值为1.7）。1号脉和3a号脉磷灰石均显示轻稀土元素富集，反映其形成过程中有含Cl热液的参与。3号脉磷灰石显示强烈Eu负异常和Ce正异常，而2b号脉磷灰石显示强烈Ce负异常和中等Eu负异常，这种Eu、Ce异常的差异可能与岩浆-热液阶段大量流体出溶密切相关。磷灰石的沉淀将导致热液中HF含量的降低，促使磷灰石周围铌钽矿结晶和Nb、Ta进入磷灰石中。可见，在伟晶岩形成过程中，磷灰石并非保持稳定，其分带结构和主微量成分变化记录了后期热液活动，暗示后期热液活动对伟晶岩的成矿具有重要作用。;Apatite records and preserves the information of magmatic and hydrothermal processes. There is much apatite in Koktokay pegmatitic rare-metal deposit, which provides excellent conditions for studying the diagenetic and metallogenic process of pegmatite in the deposit. Previous studies on apatite from the deposit have focused on the characteristics of rare earth elements, and less on its constraints on the diagenesis and mineralization of pegmatite. In this paper, apatite from rare-metal enriched pegmatite (No.3) and relatively barren pegmatite (No.1, No.2b, and No.3a) of the Koktokay pegmatitic rare-metal deposit is selected as the research object to study their petrography and geochemistry. Petrographic analysis shows that the apatite is mainly associated with albite, quartz, muscovite, and spessartine. EPMA analysis shows that the F content of apatite is 3.67%~4.41%, and the Cl content is less than 0.67%. The low Cl content indicates that the Cl content of the fluid exsolved from pegmatite melt is low; The MnO content of most apatite is 4.67%~8.71%, but the MnO content of apatite from No.2b pegmatite changes greatly (1.23%~14.28%), which is due to the zoning structure of the apatite, suggesting that it was affected by later hydrothermal process, which promoted apatite dissolution and reprecipitation, resulting in great changes in MnO content. LA-ICP-MS analysis shows that the rare earth element content of apatite from the relatively barren pegmatite is low (<180×10^-6); On the contrary, the content of rare earth elements in apatite of the enriched pegmatite is high (>700×10^-6) and has obvious REE tetrad effect (the average value of TE_1-3 is 1.7). The apatite from No.1 and No.3a pegmatite shows enrichment of light rare earth, reflecting the participation of bearing Cl hydrothermal fluid in their formation. The apatite of No.3 pegmatite shows extreme negative Eu anomaly and positive Ce anomaly, while the apatite of No.2b pegmatite shows strong negative Ce anomaly and medium negative Eu anomaly. The difference between Eu and Ce anomalies may be closely related to a large number of fluids dissolved by the melt in the magmatic-hydrothermal stage. The precipitation of apatite leads to the decrease of HF content in hydrothermal fluid, promotes the crystallization of columbite-tantalite group mineral around apatite, and the entry of Nb and Ta into apatite. Therefore, apatite is not stable during the formation of pegmatite, and its zoning structure and changes of major and trace composition record the later hydrothermal process, suggesting that the process plays a vital role in the mineralization of pegmatite.

Do concentrations of Mn, Eu and Ce in apatite reliably record oxygen fugacity in magmas?

Apatite is a common accessory mineral in igneous rocks, and its ability to readily accommodate a wide range of trace elements means that it may provide a useful record of magmatic composition and magmatic processes. Relative abundances of redox sensitive elements in apatite could also provide a much-needed probe of magmatic oxygen fugacity, fO2. Here, examination of a large data set of apatite and whole rock compositions is used to assess the recently proposed, and increasingly used, Mn-in-apatite oxybarometer. Correlation of apatite-whole rock Mn partition coefficients with whole rock SiO2, and calculated melt polymerisation and aluminosity, support a model where apatite Mn content is largely dependent on melt structure. In more evolved systems, a decrease in availability of non-bridging oxygens in silicate melts drives Mn from being incompatible, to an increasingly compatible element in apatite. Magmatic fO2 calculated from Ce concentrations in zircon also shows no discernible correlation with apatite Mn content. Mn content of apatite clearly does not record magmatic fO2, although it may be useful in indicating the extent of melt evolution. In contrast, concentrations of other trace elements in apatite have a much weaker, or no discernible dependence on melt structure and composition, supporting the assertion that apatite records key aspects of magmatic composition.Eu and Ce anomalies in chondrite-normalised Rare Earth Element (REE) data provide an alternative means of using apatite to probe magmatic fO2. A new method for more reliably comparing the extent of Eu and Ce anomalies in apatite REE data is used to assess controls on Eu and Ce content. Apatite Eu content shows a strong dependence on whole rock composition, indicating that Eu anomalies often reflect feldspar crystallisation. Ce anomalies in apatite are much smaller and vary from weakly positive to weakly negative. Predicted strong, negative Ce anomalies in apatite data are not observed, implying smaller differences in Ce3+ and Ce4+ compatibility in apatite than in minerals such as zircon. The cause of small positive Ce anomalies in apatite data is unclear. Comparison of apatite and zircon data suggests that fO2 may have some control on apatite Ce content. However, the narrow range of Ce anomalies in apatite data, and lack of an identifiable control of fO2, limit the extent to which apatite Ce records magmatic fO2. As such, REE contents of apatite also cannot currently be used to reliable indicate trends in magmatic fO2.

Caught in the act: A case study on microscopic scale physicochemical effects of fossilization on stable isotopic composition of bone

Geochemical zoning in a partially fossilized Pleistocene artiodactyl metapodial was contrasted with a fully fossilized Cretaceous ceratopsian femur as distinct stages along the fossilization process to investigate the physicochemical effects of fossilization and fossilization mechanisms. Bone fragments were analyzed via laser ablation ICP-MS, FT-IR, and stable isotope microanalysis to determine zoning patterns in trace elements, relative carbonate content and collagen contents, and stable isotopes of both the CO3 and PO4 components (δ13CCO3, δ18OCO3, and δ18OPO4). The Pleistocene sample shows a pronounced step in U concentration from high values (up to 90 ppm) within 1 mm of the outer bone surface and inner medullary cavity to ppb-level concentrations typical of in-vivo bone in the interior (inner ∼6 mm). High U broadly coincides with reduced collagen, higher δ13CCO3, and lower δ18OCO3. Rare earth elements (REE), however, show typical exponential decreases from bone edges inward, and δ18OPO4 shows no clear trend. The Cretaceous bone shows high REE and U contents throughout, a complete absence of collagen, and relatively uniform isotope compositions. The Pleistocene data, especially U zoning, implicate a diffusion-reaction (DR) fossilization mechanism, in which collagen degradation facilitates a recrystallization front that propagates as a front towards the bone interior, reducing OH-site CO3 content, and shifting δ13CCO3, δ18OCO3, and δ18OPO4. Disequilibrium O-isotope partitioning between the CO3 and PO4 components in the interior of the Pleistocene bone suggests that both the CO3 and PO4 components have exchanged with diagenetic waters, likely through abiotic and microbially-induced exchange, respectively. Strong partitioning between apatite and soil water, coupled with uptake of REE in apatite from surrounding sediment matrix during fossilization, leads to exponential decreases in concentrations, which are passively recorded in apatite in the bone interior. The Cretaceous data do not implicate a unique fossilization mechanism but instead reflect the consequences of protracted fossilization and the final state that the Pleistocene bone might eventually have reached had the bone not been excavated. That is, the Cretaceous bone fossilization history resulted in no collagen, reduced or no OH-site CO3, and more uniform isotopic compositions. The multi-analytical methods employed in this study may benefit studies of diagenetic alteration of other apatitic tissues, e.g., tooth enamel.

Composition and structural features of two Permian parareptile (Deltavjatia vjatkensis, Kotelnich Site, Russia) bone fragments and their alteration during fossilisation

The Kotelnich vertebrate fossil site, one of the richest of the Permian period, is characterised by the excellent preservation of fossil remains due to their burial in a silty anaerobic environment similar to modern peat bogs. The aim of the work is to carry out a comprehensive study of the composition and structure of bone fragments of the Permian parareptile Deltavjatia vjatkensis, as well as that of its embedding rocks, to support further paleoecological and fossilisation reconstructions. Fossil bones and their surrounding strata were investigated using optical and scanning electron microscopy, Raman spectroscopy, X-ray diffraction and inductively coupled plasma mass spectrometry (ICP-MS). The carbonate-rich composition of the sediment was found to favour the preservation of the bone apatite. The mineral phase of the bone tissue corresponds to fluorapatite. Organic matrix vibration bands arising on the Raman spectra correspond to CH vibrations of lipids and proteins and possibly cholesterol. The obtained data indicate a high degree of integrity of both bone mineral phase and its organic proteinaceous residue. White blood cell (WBC)-like structures were detected, which possibly could be interpreted as leukocytes. Elemental mapping of fossil bones was used to reveal element distribution features (uniform or with zones of apparent enrichment-depletion) and secondary mineralisation zones. Ca, P, Mg, Mn and S are uniformly distributed through the bone; conversely, elevated quantities of Fe are assigned to cracks and large pores formed as a consequence of the decomposition of organic materials. As compared to bone apatite, the authigenic calcite filling of bone porosities is significantly depleted in terms of microelements. The apatite rare earth element (REE) composition of bone tissue, which is inherited from seawater, can be used for paleoreconstructions of redox conditions and water composition. La/Sm ratios (0.4–0.5), high Y/Ho ratios, high uranium content and high La/Yb ratios (2–3) in the bone apatite indicate the absence of recrystallisation during the late stages of diagenesis. A positive cerium anomaly detected in the bones indicates the presence of an oxidising and possibly alkaline environment during the early stages of diagenesis in shallow coastal basin of the Kotelnich paleolocality. It is shown that 10 to 20% of REE in bone apatite is derived from seawater absorption (hydrogenous source), with the remainder having been derived from host rock (lithogenic) sources.

Archaean phosphates: a case study of transformation processes in apatite from the Barberton greenstone belt

Multiple tools have been used to determine the sensitivity of phosphates from the early Archaean Barberton greenstone belt to transformation. The assessment of the degree of transformation is crucial for verifying data about the parameters of the paleo-environment. From the obtained results, three generations of phosphates can be distinguished. Group A is observed in cherts and banded iron formation BIF early-generation fluor-hydroxyapatite that precipitated from seawater. It is characterized by flat rare earth element (REE) patterns with a positive Eu anomaly and high Y/Ho ratio in the range of 54–70. Apatites in this group lack any visible indicators of secondary alterations at the micro- and nanoscales. Fourier transform infrared spectra indicate that these apatites are relatively rich in water, and, due to cationic substitution, their OH-stretching regions exhibit complex ordering and numerous component bands. The characteristics observed in the cherts and silicified felsic volcaniclastics of group B imply advanced metasomatic alteration. They exhibit light and heavy REE depletion and an absence of water in the halogen site. Nanoscale investigations reveal cracks, pores, nanofluid inclusions and nanochannel-like structures, as well as inclusions. Group C is represented by igneous-derived apatites that partially reflect their igneous origin. The phosphates are predominantly fluorapatite with typical magmatic apatite REE distribution patterns. Imaging at the micro- and nanoscales indicates that they partially preserve the signature of igneous origin. It seems that some of the analyzed apatite partially preserved their primordial features; therefore, they might be used for the reconstruction of Archaean abiotic systems.

Sources of Extraterrestrial Rare Earth Elements: To the Moon and Beyond

The resource budget of Earth is limited. Rare-earth elements (REEs) are used across the world by society on a daily basis yet several of these elements have &lt;2500 years of reserves left, based on current demand, mining operations, and technologies. With an increasing population, exploration of potential extraterrestrial REE resources is inevitable, with the Earth’s Moon being a logical first target. Following lunar differentiation at ~4.50–4.45 Ga, a late-stage (after ~99% solidification) residual liquid enriched in Potassium (K), Rare-earth elements (REE), and Phosphorus (P), (or “KREEP”) formed. Today, the KREEP-rich region underlies the Oceanus Procellarum and Imbrium Basin region on the lunar near-side (the Procellarum KREEP Terrain, PKT) and has been tentatively estimated at preserving 2.2 × 108 km3 of KREEP-rich lithologies. The majority of lunar samples (Apollo, Luna, or meteoritic samples) contain REE-bearing minerals as trace phases, e.g., apatite and/or merrillite, with merrillite potentially contributing up to 3% of the PKT. Other lunar REE-bearing lunar phases include monazite, yittrobetafite (up to 94,500 ppm yttrium), and tranquillityite (up to 4.6 wt % yttrium, up to 0.25 wt % neodymium), however, lunar sample REE abundances are low compared to terrestrial ores. At present, there is no geological, mineralogical, or chemical evidence to support REEs being present on the Moon in concentrations that would permit their classification as ores. However, the PKT region has not yet been mapped at high resolution, and certainly has the potential to yield higher REE concentrations at local scales (&lt;10s of kms). Future lunar exploration and mapping efforts may therefore reveal new REE deposits. Beyond the Moon, Mars and other extraterrestrial materials are host to REEs in apatite, chevkinite-perrierite, merrillite, whitlockite, and xenotime. These phases are relatively minor components of the meteorites studied to date, constituting &lt;0.6% of the total sample. Nonetheless, they dominate a samples REE budget with their abundances typically 1–2 orders of magnitude enriched relative to their host rock. As with the Moon, though phases which host REEs have been identified, no extraterrestrial REE resource, or ore, has been identified yet. At present extraterrestrial materials are therefore not suitable REE-mining targets. However, they are host to other resources that will likely be fundamental to the future of space exploration and support the development of in situ resource utilization, for example: metals (Fe, Al, Mg, PGEs) and water.

Rare earth elements in conodont apatite: Seawater or pore-water signatures?

Rare earth element (REE) compositions of Lower Palaeozoic conodont microfossils from different sites in Laurentia are presented and compared to modern pore-water REE compositions reported in the literature. These data are modelled to account for matrix-induced fractionation of REEs during uptake by apatite. The apatite-water partition co-efficients (Kd) for adsorption of REEs are applied to a range of modern pore-water compositions (i.e. Pore-waterN×Kd), the resultant data being similar to Palaeozoic conodont apatite compositions. Similar resemblances to modern pore-water REE compositions are shown by palaeofluids derived from conodonts using the inverse relationship in REE adsorption kinetics (i.e. Bioapatite/Kd), with rare low concentration samples yielding HREE-enriched patterns. These results clearly show the importance of matrix effects and hence the post-mortem physico-chemical processes by which elemental uptake occurs in fossil biogenic minerals, which are crucial to consider when interpreting geochemical signatures. Furthermore, the similarities between apatite REE compositions of conodonts and those derived from modern pore-waters challenge prior hypotheses of seawater REE evolution inferred directly from conodont apatite, and question the reliability of conodont apatite as archives of seawater REE chemistry. These outcomes likely have broader implications for fossil bioapatites in general given the physico-chemical processes occurring within marine sediments and the inherent behaviour of apatite-REE systematics.

Rare earth elements in apatite as a monitor of magmatic and metasomatic processes: The Ilímaussaq complex, South Greenland

Textural and compositional variations of apatite from the plutonic Ilímaussaq complex in South Greenland and its surrounding country rocks track magmatic and metasomatic processes. Detailed back-scattered electron (BSE) imaging reveals various types of apatite textures including (i) growth zonation (concentric, oscillatory as well as sector zonation) formed during magmatic differentiation, (ii) resorption and overgrowth textures due to fluid/melt induced metasomatic overprint of precursor apatite and (iii) replacement textures indicating the destabilization of apatite in favor of monazite.In the least evolved rocks of the Ilímaussaq complex, apatite incorporates rare earth elements and Y (REY) mainly via the coupled substitution Ca2++P5+=REY3++Si4+. In the more evolved peralkaline rocks and in metasomatically overprinted rocks, however, the coupled substitution 2 Ca2+=REY3++Na+ becomes increasingly relevant, and apatite incorporates successively more LREE compared to HREE as shown by increasing (La/Gd)N and (Gd/Yb)N ratios. Similarly, at the contact between the Ilímaussaq rocks and the granitic country rocks, the metasomatic effect of the emplacement of the Ilímaussaq melts is preserved in partly resorbed precursor apatite, which is overgrown by REY-enriched apatite with higher (La/Gd)N and (Gd/Yb)N ratios compared to apatite from granites more distant from the contact.This study shows, that apatite textures and compositions are suitable to track both primary magmatic and later fluid-present metasomatic processes. The incorporation of REY in apatite is not only dependent on the amount of REY present but also depends largely on Na activity in the apatite-precipitating melts and fluids.

Rare earth element abundances in apatite in the Bushveld Complex—A consequence of the trapped liquid shift effect: REPLY

The concentrations of the rare earth elements (REEs) in apatite from a 600-m-thick sequence toward the top of the Bushveld Complex, South Africa, have previously been published; they show two ranges of compositions in a lower section and an upper section. The data were interpreted in terms of liquid immiscibility. The evidence for this model is reassessed, and an alternative explanation offered that involves the trapped liquid shift effect. In this process, the true cumulus phase compositions reequilibrated with trapped liquid as it solidified, and REE abundances in apatite were variably increased. The extent of the change depends on the relative proportions of cumulus apatite and trapped liquid. Calculations show that if there was 5% apatite and 10% trapped liquid, as found in the lower section, the REE abundance in the final apatite would have only increased marginally relative to the original cumulus composition. However, in the upper section where there was only 2% apatite and 25% trapped liquid, the REE abundances were increased by a factor of 3. Most of the REEs are essentially incompatible in the other cumulus phases except apatite, and the other phases have little influence on the final concentrations of REEs in apatite. However, for Eu, which partitions into plagioclase, this mineral acts as a major buffering influence and relatively less Eu than the other REEs entered apatite during the solidification process. As a result, the calculated final apatite in the upper section developed a large negative Eu anomaly, as observed in the actual mineral analyses. The concept of large-scale liquid immiscibility in the upper part of the Bushveld Complex based on REEs in apatite is challenged, and an interpretation involving the trapped liquid shift effect is considered more plausible.

Late Wenlock sequence and bentonite stratigraphy in the Malvern, Suckley and Abberley Hills, England

The Late Wenlock Series (Homerian Stage) of the central Midland Platform occupies an area stretching from Ledbury to the Malvern, Suckley and Abberley Hills. Based upon the establishment of a sequence stratigraphic framework for the Much Wenlock Limestone Formation, and the immediately under- and over-lying Coalbrookdale and Lower Elton Formations, comparisons can now be made with key sections across the northern Midland Platform and beyond. These correlations have been strengthened by the determination of apatite rare earth element (REE) geochemical signatures obtained from four volcanic ash layers (bentonites) at Whitman's Hill Quarry (Herefordshire), which allow for comparisons with published coeval sections at Wren's Nest Hill (West Midlands) and Wenlock Edge (Shropshire), as well as with bentonites described from the Island of Gotland (Sweden).Across the study area fifteen parasequences associated with two pronounced regressive episodes, separated by a marked transgression, can be identified. The lithological responses to these relative sea-level changes are the same as those reported from the West Midlands, including the threefold division of the Much Wenlock Limestone Formation into Lower Quarried Limestone, Nodular Beds and Upper Quarried Limestone Members. Apatite REE geochemical signatures from Whitman's Hill Quarry identify three bentonites which probably originated from a granodiorite magmatic source, while a fourth bentonite has a distinctively mafic composition, more akin to that of a gabbro or syenite. This distinctively mafic bentonite is preserved on a marked flooding surface within the Nodular Beds Member and appears compositionally and stratigraphically equivalent to a bentonite at Wren's Nest Hill (West Midlands). Furthermore in both sections this bentonite is of notable thickness (120–200mm) allowing for its identification in other sections across the region. Comparisons with Gotland identify three closely spaced bentonites of a similar mafic composition to the bentonite described from the Midland Platform. While similarities in stratigraphic position and composition do not, at present, allow for the identification of a single ash fall event covering both the Midland Platform and Gotland, they are indicative of a shared source region, which may offer the possibility for future bentonite correlation between these regions.

Apatite Composition: Tracing Petrogenetic Processes in Transhimalayan Granitoids

Apatites crystallized from different types of igneous rocks show significant variations in the abundances of some minor and trace elements. In this study, electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry were used to determine the concentrations of 25 minor and trace elements in apatite separated from three principal rock types of theTranshimalayan igneous plutonic suite: S-type granites, the I-type Gangdese batholith and postcollisional adakites. F, Mn, Sr and rare earth elements (REE) in apatite vary systematically with the composition of the host magma and thus have high potential as petrogenetic tracers. More specifically, the F and Mn contents of apatite can be used as an indicator of magma aluminosity or differentiation index. Combined with Sr and REE data, which show significant variations in apatite from different rock types, these elements are useful for constructing ‘discrimination diagrams’. This study also reveals that apatite has the capacity to retain geochemical information about the host magma through the course of magmatic evolution. Systematic variations of Sr and REE in apatite with bulk-rock aluminosity are the results of partition competition with pre-existing and coexisting major and accessory minerals in silicate melts, and thus are useful for more detailed investigations of petrogenetic processes such as fractional crystallization and magma mixing, which is signaled by inconsistent Eu anomalies, Sr abundances and REE patterns relative to bulkrock compositions.

A fast method for apatite selective leaching from granitic rocks followed through rare earth elements and phosphorus determination by inductively coupled plasma optical emission spectrometry

Rare earth elements (REE) and phosphorus (P) in apatite were determined using inductively coupled plasma optical emission spectrometry (ICP-OES) after partial dissolution of the granitic rocks and pure apatite. The dissolution was performed with nitric acid in an open system and the matrix elements were separated by a cation exchange procedure. Samples of pure apatite from granitic rocks were dissolved with, 0.14 mol L −1 nitric acid. The results showed that the release of REE is due to apatite leaching because it could be assessed by comparing the chondrite-normalised pattern corresponding to the rocks and the pure apatite. Similar results were found for absolute REE abundance from the partial dissolution of the rocks and pure apatite. This simple and rapid method can be applied for the determination of REE in apatite as an indicator for mineral exploration, although its use in petrology could be possible.

Isotopic composition of recent shark teeth as a proxy for environmental conditions

The O, C, and Sr isotope compositions of teeth from ten species, belonging to five families, and three orders of sharks were measured to determine the influence of habitat, diet, and possible species-specific fractionation effects on the isotopic composition of biogenic phosphate from fish. The sharks were recently caught in subtropical waters off the KwaZulu-Natal (KZN) coast of South Africa, as well as from cold waters in Prince William Sound (PWS), Alaska, and Victor Bay (VB), Nunavut, Canada. δ 18O values of tooth phosphate (δ 18O P) range from 20.9 to 23.5‰ for the KZN sharks. For most species the range in measured δ 18O P values is about 0.6‰, but it may be as high as 1.1‰ for different teeth from a single shark. Dentine and enameloid within individual teeth have no apparent differences in δ 18O P values. The δ 18O P values of the KZN shark teeth reflect the typical habitat of the studied species, primarily the thermal structure of the water column off KZN at depths between 20 and 280 m. The δ 18O P values of teeth from different Greenland sharks from VB and Pacific sleeper sharks from PWS are very homogeneous, averaging 25.8 and 24.7‰, respectively. These values appear to be in equilibrium with deep (>500 m) ocean waters in each case at temperatures of about −0.3°C or less. There is little discernable evidence for species-specific fractionation effects for the oxygen isotope composition of phosphate in the studied marine fish. The oxygen isotope composition of carbonate in apatite averages about 9.1‰ higher than corresponding δ 18O P values, in agreement with equilibrium fractionation between carbonate and phosphate, but with a large variance (1σ = ±1.5‰). δ 18O C values also vary by up to 1‰ between enameloid and dentine within single teeth, but in a non-systematic way. Differences in δ 13C values between carbonate in enameloid and dentine is also large (up to 8‰) but the δ 13C values vary systematically. Enameloid is always enriched in 13C compared to dentine and the 13C content increases with developmental stage of the teeth. δ 13C values measured for enameloid (1.6 to 4.8‰) appear to approach equilibrium with dissolved inorganic carbon in seawater. In contrast, δ 13C values for dentine range from −6.4 to −2.3‰ for KZN sharks, and −9.0 to −10.8‰ for the cold-water sleeper sharks, and are compatible with a predominantly dietary carbon source. The 87Sr/ 86Sr ratios of teeth from KZN sharks as well as those from PWS and VB are uniform, averaging 0.709167. Sr content varies from 1270 to 2100 ppm, a range that is similar to that in well preserved fossilized teeth. Seawater Sr is thus clearly incorporated in vivo. Concentrations of Sm and Nd are in the ppb range and contrast the ppm range in fossilized teeth, indicating a postmortem incorporation of rare earth elements in apatite of the teeth.

Rare earth elements in apatite: Uptake from H 2O-bearing phosphate-fluoride melts and the role of volatile components

The partitioning of rare earth elements (REEs) between fluorapatite (FAp) and H 2O-bearing phosphate-fluoride melts has been studied at about 700 and 800°C and 0.10–0.15 GPa. REE uptake patterns, i.e., plots of D(REE:FAp/melt), are convex upwards and peak near Nd for single-REE substituted FAp at minor (0.03–0.25 wt% REE 2O 3) abundances, and binary(LREE + HREE)-substituted FAp, and hexa-REE-substituted FAp at minor to major (0.25–7.8 wt% REE 2O 3) abundances. Partition coefficients for minor abundances of REE and depolymerized phosphate melts are about 5, 8, and 1 for La, Nd, and Lu, respectively and broadly comparable to those for early fluorapatite in the fractionation of melts of basaltic composition. The Ca2 site exerts marked control on the selectivity of apatite for REE because it preferentially incorporates LREE and its effective size varies with substitution of the A-site volatile anion component (F, Cl, OH). Using simple crystal-chemical arguments, melt(or fluid)-normalized REE patterns are predicted to peak near Nd for fluorapatite and be more LREE-enriched for chlorapatite. These predictions are consistent with data from natural rocks and laboratory experiments. The wide variation in D(REE:apatite/melt) in nature (from <1 for whitlockite-bearing lunar rocks to about 100 for evolved alkalic rocks) is attributed largely to the influence of the volatile components.

Luminescence of uranium and rare-earth elements in apatite of fossil fish teeth

Time-delayed laser-induced luminescence of uranium and rare-earth elements (REE) in apatite of fossil fish teeth from the phosphorites of the Senonian Mishash Formation, Israel, were investigated before and after thermal treatment. The unheated samples show luminescence of UO2+2. Luminescence of REE3+ (Sm, Eu, Pr) is observed only after heating the samples at 1100 K in air. The spectral properties indicate that UO2+2 in the unheated samples is located in two different positions, as aqua-complexes of uranyl-ions and associated with organic matter. The REE in the unheated samples are accommodated in non-luminescent form. After heating the REE3+ (Sm, Eu, Pr) are located in the Ca2+ II site presumably due to thermal diffusion.

Rare earth elements in apatite and magnetite in Kiruna-type iron ores and some other iron ore types

An investigation of the content and distribution of REE in apatite and magnetite in the iron ores of Kiruna type and some other iron ores is presented. REE in apatite and magnetite in different ore types show characteristic patterns which are related to different modes of formation of the ores. The magnetite-apatite iron ores of the world can be divided into two types: (a) Kiruna iron ores proper which occur in volcanic rocks, and (b) iron ores connected with deuteric processes and/or related to intrusive rocks. Apatite of the Kiruna ores proper in Fennoscandia (e.g. Kiirunavaara, Malmberget and Grängesberg) shows a common pattern with 2000–7000 ppm REE, a weak to moderate LREE/HREE fractionation and negative Eu anomalies. In the Kiruna area, apatite of the main, P-poor ores and of the later, hydrothermal-exhalative P-rich ores, have the same REE distribution which indicates a common source. There is a similar REE distribution in magnetite-apatite trachytic-rhyodacitic host rock which confirms a close magmatic relationship. Apatite in phosphorites (such as the Paleoproterozoic Påläng deposit in northern Sweden) has a different composition (< 1000 ppm REE with Ce depletion) which excludes a sedimentary origin of the Kiruna apatite. Apatite in other volcanogenic magnetite-apatite ores outside Fennoscandia differ by a stronger LREE/HREE fractionation and by a medium to large Eu depletion, partly indicating a relationship to alkaline intrusions. The Avnik apatite, Turkey, shows a weak differentiation in combination with a pronounced negative Eu anomaly, indicating provenance from silicic magmatic sources. The REE pattern of apatite in the deuteric-hydrothermal apatite-bearing iron ores is in general similar to that of apatite in the Kiruna iron ores proper. The similarity indicates a common process of formation for both ore types. The apatite-iron ores of the Kiruna type proper were formed by a late-magmatic differentiation. The ores of the Kiruna area are, in similarity with some other magnetite-apatite ores, emplaced along regional fracture-fault lines and close to an older basement. In general the REE pattern of apatite in the different deposits shows an affinity to alkaline or sub-alkaline magmas, indicating a rifting environment. The alkaline, trachytic volcanics hosting the Kiruna ores in northern Sweden are clearly related to an extensional setting where rifting was important. A probable source for this large-scale ore-forming process was partial melting of deep-seated rocks. The ores evolved in an intracontinental setting with magma generation caused by underplating of older crust. The process giving rise to magnetite-apatite ores of the Kiruna type has occurred during the time span from Paleoproterozoic to Tertiary. The Proterozoic ores occur mainly in cratonized areas, whereas the younger ones occur in fold belts. The amount of ore formed in post-Proterozoic time is as large as that formed in Proterozoic time.

Determination of light rare earth elements in apatite by x-ray fluorescence spectrometry after anion exchange extraction

The results of an investigation, the purpose of which was to study the feasibility of analysis of La, Ce, Pr, and Nd in apatite minerals, utilizing x-ray fluorescence spectrometry (XRF), are discussed. After sample dissolution in HNO/sub 3/, rare-earth elements (REEs) are separated by a mixed solvent anion exchange using the batch extraction technique. The anion exchanger employed is the strongly basic resin Dowex 1X8, 100 to 200 mesh (nitrate form). REEs are fixed on the resin from a medium consisting of 95% CH/sub 3/OH-5% 7 M HNO/sub 3/ (v/v). The dried resin is uniformly spread over a disk of self-adhesive foil backed with a cellulose support. The thin resin film formed is then used for XRF analysis. Synthetic standards prepared following the same procedure are employed for calibration. Analytical results of two apatite samples are presented. Good correlation is obtained between XRF and neutron activation analysis data. Limits of detection, precision, and accuracy of the results are discussed.