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Nanocrystals of apatitic calcium phosphate impart the organic-inorganic nanocomposite in bone with favorable mechanical properties. So far, the factors preventing crystal growth beyond the favorable thickness of ca. 3 nm have not been identified. Here we show that the apatite surfaces are studded with strongly bound citrate molecules, whose signals have been identified unambiguously by multinuclear magnetic resonance (NMR) analysis. NMR reveals that bound citrate accounts for 5.5 wt% of the organic matter in bone and covers apatite at a density of about I molecule per [(2 nm).sup.2], with its three carboxylate groups at distances of 0.3 to 0.45 nm from the apatite surface. Bound citrate is highly conserved, being found in fish, avian, and mammalian bone, which indicates its critical role in interfering with crystal thickening and stabilizing the apatite nanocrystals in bone. nanocrystal stabilization | nanocomposite | organic-inorganic interface | bone composition | solid-state NMR doi/ 10.1073/pnas.1009219107

Low-OH apatite of the compositional range [Ca.sub.4.99-5.06][(P[O.sub.4]).sub.2.98-3.00 [F.sub.0.51-0.48][Cl.sub.0.38-0.36]O[H.sub.0.14-0.12] was synthesized and characterized structurally by synchrotron-based single-crystal X-ray diffraction (XRD), and multiple nuclear magnetic resonance (NMR) spectroscopic techniques. The average structure is hexagonal with space group [P6.sub.3]/m. The presence of scattering in the single-crystal diffraction data set, which is incommensurate within the average hexagonal structure, suggests the presence of localized short-range monoclinic domains. Complex lineshapes in the [sup.31]P and [sup.19]F MAS NMR spectra are also consistent with the presence of an incommensurate phase. No evidence was detected for splitting of the Ca2 site into two distinct sites (as had been previously reported for hexagonal ternary apatites). Structure refinement and [sup.19]F {[sup.35]Cl} TRAPDOR NMR experiments verified intercolumnal neighboring of F and Cl atoms (inter-column distance of 2.62 [Angstrom]) within this low-OH- apatite suggesting that long-range neighboring ofF and Cl within the apatite anion channels is feasible. Keywords: Apatite, NMR spectroscopy, single-crystal XRD, Mars, Moon, PGE, synthesis

Individual detrital apatite grains from the Esplanade, Coconino, and Moenkopi Formations in the Grand Canyon region of the Colorado Plateau yield (U-Th)/He dates from 104 to 5 Ma. The range of dates within each unit far exceeds analytical uncertainty, but correlates with both He concentration [He] and effective U concentration [eU]. These dates are all significantly younger than the sandstone units, indicating partial to complete He loss following deposition. Recently published laboratory diffusion data suggest that He retentivity in apatite increases with radiation damage. Forward models predict that the consequences of this effect will be manifested most clearly as a correlation between (U-Th)/He dates and the [He] and [eU] in suites of apatites that (1) are characterized by a large span of [eU], and (2) had thermal histories in which sufficient time elapsed for the apatite He diffusion kinetics to diverge prior to reheating and partial resetting. Apatites in the sedimentary units investigated fit these criteria. Using geologically reasonable deposition, burial, and unroofing histories, simulations that include the effect of radiation damage on apatite He retentivity can reproduce the observed distributions of apatite dates and correlations with parent and daughter concentrations. These results suggest that a span of (U-Th)/He dates positively correlated with [eU] may provide important information regarding a sample's thermal history. Keywords: (U-Th)/He, apatite, radiation damage, Colorado Plateau, He diffusion kinetics, thermo-chronometry, Grand Canyon.

The Kenya rift valley is the classic example of an active continental rift zone. We report the rift flank cooling history based on a combination of previous apatite fission track (AFT) and new (U-Th)/He (AHe) data. Our results corroborate the Late Cretaceous rapid cooling episode of continent-wide significance revealed previously by AFT dating. Post-Cretaceous cooling of the eastern rift flank was slow with net cooling of 3400 m in central Kenya. This timing also largely coincides with the uplift of the Western Rift flanks in Uganda and Congo and with the change toward drier conditions and grassland-dominated vegetation in East Africa. We propose that the regional morphotectonic evolution of the Kenyan rift flanks contributed to late Cenozoic environmental change in East Africa, thus superimposing a pronounced local effect on global climate change at that time. Keywords: Kenya rift valley, thermochronology, apatite (U-Th)/He analysis, late Neogene, climate change.

Due to the scarcity of datable chronostratigraphic markers and the related difficulties of quantifying depths of erosion in cratonic landscapes, conceptual models of tropical pediplain and etchplain evolution commonly lack time and vertical elevation scales. Here, we present the first quantitative study of relief development in South India based on in situ-produced [sup.10]Be dating aided by previously acquired apatite fission-track data. Erosion rates measured on the summits of inselbergs concur with the perception of inselbergs as islands of low erosion, but they also reveal a critical contrast between slowly evolving ([less than or equal to]2 m/m.y.) higher-relief landforms and more rapidly eroding (8-12ndm.y.) lower-relief landforms. This relationship is independent of lithology and climate but suggests that erosion rates on the surrounding plain, which are controlled by fluvial incision rates into the plateau surface, feed back on inselberg dynamism. A discussion on the most suitable sites for dating bedrock landforms highlights the problems of sampling design, the difficulties of linking measured erosion rates to the minutiae of process, and the limitations of both single- and multiple-chronometer denudation chronologies in low-energy cratonic environments. Keywords: inselberg, cosmogenic nuclide dating, erosion rate, backwearing, downwearing, etchplain, India.

[1] Although the structural geometry of the Cenozoic Altiplano-Puna plateau in the central Andes is well defined, the temporal evolution of this contractile deformation is poorly constrained. To address this shortcoming, we used apatite fission track thermochronology (AFT) to quantify the cooling and exhumation history along a transect at 21[degrees]S in southern Bolivia, through the deformed intermontane Altiplano basin, the doubly vergent thrust belt of the Eastern Cordillera and the inner foreland thrust belt east of the plateau (Interandean Zone). Thermal history modeling combined with published balanced cross sections and stratigraphic data constrain exhumation histories. Exhumation started during the late Eocene (40-36 Ma) in the central Eastern Cordillera, possibly due to bivergent thrusting and Cretaceous rift structure inversion. During the early Oligocene (33-27 Ma), exhumation spread across the study area as the current boundary thrusts of the Eastern Cordillera were activated. The inner west vergent thrust system became active in irregular order until circa 20 Ma, whereas the east vergent Interandean thrust belt formed by eastward propagating deformation since circa 30 Ma. Plateau exhumation continued at ~0.2 mm/yr until shortening terminated by 11-7 Ma. Shortening within the plateau since circa 30 Ma did not evolve by lateral accretion of thrust wedges; the propagating deformation style is spatially confined to the foreland thrust belt, which initiated coeval to plateau deformation (Interandean Zone) but propagated mainly after circa 10 Ma (Subandean Zone). Early Oligocene plateau-wide tectonically driven exhumation suggests that subduction-related processes had already thermally weakened the continental lithosphere prior to the 2725 Ma onset of volcanic activity. Citation: Ege, H., E. R. Sobel, E. Scheuber, and V. Jacobshagen (2007), Exhumation history of the southern Altiplano plateau (southern Bolivia) constrained by apatite fission track thermochronology, Tectonics, 26, TC1004, doi: 10.1029/2005TC001869.

The oxygen isotope composition of fossil fish teeth, a paleo-upper ocean temperature proxy exceptionally resistant to diagenetic alteration, provides new insight on the evolution of the low- to middle-latitude thermal gradient between the middle Cretaceous climatic optimum and the cooler latest Cretaceous period. The new middle Cretaceous low to middle latitude thermal gradient agrees with that previously inferred from planktonic foraminifera [[delta][sup.18]]O recovered from Deep Sea Drilling Project and Ocean Drilling Program drilling sites, although the isotopic temperatures derived from [[delta][sup.18]]O of fish teeth are uniformly higher by ~3-4 [degrees]C. In contrast, our new latest Cretaceous thermal gradient is markedly steeper than those previously published for this period. Fish tooth [delta][sup.18]O data demonstrate that low- to middle-latitude thermal gradients of the middle Cretaceous climatic optimum and of the cooler latest Cretaceous are similar to the modern one, despite a cooling of 7 [degrees]C between the two periods. Our new results imply that no drastic changes in meridional heat transport are required to explain the Late Cretaceous climate. Based on climate models, such a cooling without any change in the low to middle latitude thermal gradient supports an atmospheric C[O.sub.2] decrease as the primary driver of the climatic evolution recorded during the Late Cretaceous. Keywords: Cretaceous, climate, oxygen isotopes, apatite.

We present new apatite fission-track (AFT) data from the central western Alps that confirm the synchronicity and high cooling rates during Latest Miocene-Pliocene final exhumation of the External Crystalline Massifs but also provide evidence for diachronous Neogene evolution along and across the internal arc. To the SE of the Pelvoux Massif, across the front of the internal arc (Penninic Frontal Thrust), the jump in AFT ages (c. 22 Ma) and in final cooling rates is significantly larger than further north. This difference results from reversal of movement along a major Oligocene thrust. In its hanging wall, the western Brianconnais Zone provides a mean AFT age of c. 27 Ma, which is older than further north. Early cooling in the southern Brianconnais Zone would result from rapid erosion of the compressional tan structure built during the Oligocene. Across the entire Brianconnais and Piemont nappe stack, with the exception of the Dora-Maira Massif, AFT ages young eastward and span the entire Miocene, a period during which this structure underwent extension. Further north a reverse gradient with ages younging northwestward has been described, prompting the question of the asymmetry of the internal western Alpine arc during its late-stage tectonic and morphological evolution.

Phosphohedyphane, [Ca.sub.2][Pb.sub.3][(P[O.sub.4]).sub.3]Cl, space group P[6.sub.3]/m, a = 9.857(1), c = 7.130(2) [Angstrom], V = 599.9(2) [[Angstrom].sup.3], Z = 2, is a new mineral from the Capitana mine, Copiapo, Atacama Province, Chile and has been identified from numerous other deposits world-wide. At the Capitana mine, it occurs as transparent, colorless, tapering hexagonal prisms, as individuals up to about 0.5 mm in length and 0.1 mm in diameter, which are commonly doubly terminated. Crystals often occur in subparallel intergrowths and irregular clusters. Phosphohedyphane forms as a secondary mineral in the oxidized zone of the Capitana mine, a Cu-Pb-Ag deposit, where it closely associated with quartz, duftite, and bayldonite. Crystals exhibit core-to-rim chemical zonation and electron analyses of cores/rims yielded CaO 9.24/7.76, PbO 67.60/69.35, [P.sub.2][O.sub.5] 18.40/17.00, [As.sub.2][O.sub.5] 2.73/3.68, Cl 3.32/3.22, -O = Cl-0.75/-0.73, total 100.54/100.28 wt%. The name phosphohedyphane is for the relationship of the mineral to hedyphane. The mineral has an apatite structure with ordering of Ca and Pb in the two non-equivalent large cation sites, as in hedyphane. The structure refinement indicates that the Ca2(6h) site is completely occupied by Pb and the Cal(4f) site is occupied by 92% Ca and 8% Pb. The tetrahedral site refines to 91% P and 9% As. The refinement indicates the 0,0,0 position to be fully occupied by Cl. The ordering of Ca and Pb in phosphohedyphane has important implications with respect to the chlorapatite-pyromorphite solid solution series. An analysis of compositions of natural members of the pyromorphite-mimetite-turneaureite-chlorapatite system suggests the existence of complete solid solution among pyromorphite, mimetite, hedyphane, and phosphohedyphane. No stable solid solutions appear to exist between the joins phosphohedyphane-hedyphane and chlorapatite-turneaureite in natural systems. Keywords: Phosphohedyphane, new mineral, crystal structure, chemical analysis, solid solution, pyromorphite, apatite group

X-band electron paramagnetic resonance (EPR) spectra of gamma-irradiated crystals of carbonate-bearing fluorapatite from the Levant mine, Cornwall, England, revealed the presence of two previously characterized centers (i.e., an [O.sup.-] defect and an [O.sup.-][[].sub.F] defect, where [[].sub.F] represents a vacancy at the F site), a C[O.sup.-.sub.2] radical, and a new oxygen-associated hole-like center in the anion column. The [O.sup.-][[].sub.F] center in carbonate-bearing fluorapatite is stable at room temperature, whereas in carbonate-free fluorapatite the stability of this radical is shifted to lower temperatures ( Keywords: EPR spectroscopy, fluorapatite, C[O.sup.-.sub.2] radical, new [O.sup.-] center, carbonate ions

The North Atlantic continental margins have been subject to widespread exhumation, although the timing, magnitude and causes of this uplift and erosion are debated. Exhumation is thought to be most severe across the Irish Sea basin system (Western UK), and recent years have seen an increasing emphasis on the role of Palaeogene underplating as the primary mechanism of uplift. We present a study of palaeothermal and compaction data from the Mochras borehole (NW Wales). Located near the presumed locus of exhumation, Mochras penetrated thick successions of Lower Jurassic and Oligo-Miocene sediments. Our results indicate that both these successions experienced considerably deeper burial prior to early Cretaceous and Neogene exhumation, respectively. Apatite fission-track analysis (AFTA) and vitrinite reflectance data from the borehole reveal evidence for exhumation-related cooling episodes beginning during the Cretaceous (150-80 Ma) and Cenozoic (50-0 Ma). Regional AFTA results and stratigraphic constraints refine the timing estimates to the early Cretaceous (120-115 Ma) and Neogene (20-0 Ma). Estimates of exhumation magnitudes during these episodes based on palaeothermal and compaction data are c. 2.5 km and c. 1.5 km, respectively. Palaeothermal data provide no evidence for elevated Palaeogene palaeotemperatures indicative of deeper burial, and thus question the basis of Palaeogene exhumation. Keywords: Irish Sea, apatite fission-track analysis, vitrinite reflectance, compaction, exhumation.

Researchers from London and Scotland evaluated the ability of crystalline apatite to remediate toxic metals in contaminated soils and reduce the bioavailability of metals through metal phosphate formation. Sample soils were taken from the Parys Mountain, Leadhills and Wanlockhead in the United Kingdom.

Activation energy and apatite surface area are important when controlling the phosphorus flux from marine net ecosystem production in geologic time. This conclusion was derived through a kinetic treatment of existing data used in a weathering model.

Two metabentonite suites occur within the Wenlock limestones and marls of Gotland, one within the Slite Formation (M. belophorus to the C. ellesae biozones) and the other in the Mulde Formation (G. nassa-M, dubius Biozone). Their geochemical characteristics based on rare-earth element (REE) distributions in apatite crystals separated from the metabentonites suggest origins from three separate volcanic sources. One of these sources has an alkaline affinity, reflected in relatively high levels of Th, Nb and Zr, which suggests that it may have lain over thickening continental crust during the waning stages of the closure of the Tornquist Sea, while the other two represent calc-alkaline magmas. The source of the volcanic ash is placed some 400 km to the southwest of Gotland, on the Tornquist-Teysseyre Zone, which is the northernmost expression of the Trans-European Suture Zone. Distinctive differences in REE distribution in apatite from these metabentonites should assist in future correlation studies in Wenlock stratigraphy, both within the Baltic region and further afield.

Rietveld refinements using 12 sets of X-ray diffraction powder data from milligram samples of human dental enamel provide detailed information about the structure and composition of enamel apatite. The principal difference in atomic parameters between enamel apatite and Holly Springs hydroxylapatite is in O2, which is reflected in a reduction in the P-O2 bond length of 0.085 [Angstrom] and P[O.sub.4] volume by 3.6%. Modeling the hexad axis scattering with a single OH- ion gives a 0.089 [Angstrom] shift of the ion further away from the mirror plane at z = 1/4. The known distributed electron density along the hexad axis in enamel has been confirmed by direct comparison with synthetic hydroxylapatite. Although the [Mathematical Expression Omitted] ion position could not be determined directly, evidence for partial replacement of [Mathematical Expression Omitted] by [Mathematical Expression Omitted] ions came from an 8% diminution of the P site occupancy compared with that in stoichiometric hydroxylapatite. The observed reduction in the P-O2 bond length and P[O.sub.4] volume in enamel is also consistent with this substitution. The loss of negative charge caused by [Mathematical Expression Omitted] replacing [Mathematical Expression Omitted] ions and loss of OH- ions is compensated by loss of [Ca.sup.2+] ions from Ca2 sites. The calculated density from the X-ray results is 3.021 g/[cm.sup.3], in agreement with deductions from previous chemical analyses.

In the southern Oman Mountains, high-pressure metamorphic rocks of continental origin crop out beneath the Cretaceous Samail ophiolitic nappe. We collected 14 samples from 15 to 1200 m above sea level and at various structural levels that show apatite fission-track ages between 40 [+ or -] 7 and 55 [+ or -] 5 Ma. The mean confined track lengths vary from 13.08 to 13.70 [[micro]meter]. Fission-track data optimization shows that the subophiolitic units cooled slowly below 60 [degrees] C at ca. 53 Ma, then remained at low temperature until ca. 19 Ma, i.e., during the weak postorogenic subsidence of the obduction belt. The subophiolitic basement was reheated to [approximately]70-80 [degrees] C at ca. 7-4 Ma, before final cooling. The reheating event is correlated with the late Miocene-Pliocene (Zagros) compressional phase. Post-Oligocene heating up to 80 [degrees] C is also documented by stable isotope study of the post-nappe Eocene-Oligocene onlap. Both the Paleocene and the Pliocene-Quaternary denudation rates are close to 0.3 mm/yr, and compatible with isostatically assisted erosion processes.

Analyses of the Nd isotopic composition and REE distribution in biogenic apatite (organophosphatic brachiopods and conodont elements) from the Cambrian and Ordovician sequences of the Baltic plate give new insights into the development of the southeastern segment of the continental margin bounding the Iapetus ocean. The Nd isotope analyses show [[Epsilon].sub.Nd(t)] of [approximately] -8.0 for the Cambrian, indicating that the main source of the sedimentary deposition came from weathered sedimentary rocks of Vendian and Cambrian age. The increase of [[Epsilon].sub.Nd(t)] to [approximately]-5.0 for the Early Ordovician indicates the appearance of a new source of radiogenic Nd in the surrounding area - most likely a volcanic arc along the western borderland of Baltic plate from Arenigian time. Samples of Cambrian biogenic apatite show significantly lower total amounts of REE than do the Ordovician samples, and this is probably due to a shorter exposure to seawater before burial during Ordovician sedimentary accumulation in Baltoscandia. These preliminary results suggest that biogenic apatite from the Baltoscandian basin preserves geochemical signatures of the water masses that will be important for understanding the evolution of the Iapetus ocean during the early Paleozoic.

A technique to estimate the age of topographic relief using the ages of apatites determined from uranium, thorium and helium content is described. The results from the sierra Nevada, California, suggest that the sierra developed an Andean size topography between 185 Myr and 70-80 Myr. This coincided with crustal thickening. A gradual reduction of mean crestal elevation is inferred.

Over much of its length, the Andean orogen is characterized by a generally east-vergent geometry and a progressive eastward (cratonward) migration of individual arc-orogenic elements. A departure from this model occurs in the Sierras Pampeanas region of central western Argentina where a terrane of active basement uplifts is currently developing to the east of the main Cordillera. Apatite fission-track data from uplifted Precambrian and Phanerozoic basement rocks of the Sierras Pampeanas constrain the tectonic development of this terrane and indicate that deformation associated with exhumation may have propagated broadly westward since the late Miocene. Two pre-Andean cooling events - during the Carboniferous-Permian (ca. 300-280 Ma) and the early Jurassic-middle Jurassic (ca. 200-174 Ma) - have been identified. The onset of Andean deformation is represented by a cooling event during the late Paleocene-middle Eocene. This cooling was followed by a period of middle Miocene-late Miocene reheating, during foreland basin-style sedimentation. Exhumation, and possible westward migration of the exhumation 'front' in the Sierras Pampeanas, commenced during the late Miocene-Pliocene to the east of the dominantly east-vergent Precordillera fold-and-thrust belt. The apparent convergence of deformation in these two terranes and the progressive closure of Miocene-Pliocene intermontane basins in the Sierras Pampeanas may reflect the early stages of Andean plateau uplift. The relative timing of plateau development along strike suggests that lateral thickening of the orogen is progressing southward at least from the latitude of central Bolivia (ca. 20[degrees]S). Furthermore, the time-space coincidence between basement uplift and flattening of the subducted slab beneath the Sierras Pampeanas suggests that a relationship exists between westward displacement of the terrane and the dynamics of plate interaction.

Forty-seven drillcore samples from the Peace River Arch Region, Western Canada sedimentary basin were subjected to apatite fission track (AFT) analysis. The time-temperature data from measured AFT parameters were derived using the controlled random search algorithm. Results reveal regionally consistent coherent paleotemperature field in the samples. Results also suggest that the paleotemperatures are due to thermal disturbances in the region during the end of the Laramide Orogeny.

An apatite fission track thermal annealing model was examined and implemented in a controlled random search algorithm. The algorithm was found to provide an accurate parameter-space search scheme and exhibit the ability to include constraints on thermal histories and the ability to identify global minimum despite the presence of local minima. The use of prior constraints and the interpretation of solution sets should be done carefully to prevent over-interpretation.

Apatite crystals from two types of samples were analyzed by electron microprobe for 15 major and trace elements: (1) apatite in [H.sub.2]O- and S-saturated experimental charges of the 1982 El Chichon trachyandesite and (2) apatite in volcanic rocks erupted from 20 volcanoes. The S[O.sub.3] contents of the experimental apatite increase with increasing oxygen fugacity ([f.sub.[o.sub.2]]), from [less than[0.04 wt% in reduced charges buffered by fayalite-magnetite-quartz (FMQ), to 1.0-2.6 wt% in oxidized charges buffered by manganosite-hausmanite (MNH) or magnetite-hematite (MTH). The S[O.sub.3] contents of MNH- and MTH-buffered apatite also generally increase with increasing pressure from 2 to 4 kbar and decreasing temperature from 950 to 800 [degrees] C. The partition coefficient for S[O.sub.3] between apatite and oxidized melt increases with decreasing temperature but appears to be independent of pressure. Apatites in volcanic rocks show a wide range of S[O.sub.3] contents (

Single crystals of natural F-rich apatite and 800 keV [Kr.sup.2+] ion-beam-amorphized apatite were irradiated by an electron beam in a transmission electron microscope over a range of beam energies and beam currents. Irradiation of crystalline apatite using a high current density (16 A/[cm.sup.2]) caused the precipitation of cubic CaO from the crystalline apatite matrix. Using a lower beam current (1.6 A/[cm.sup.2]), the formation of nanometer-sized voids was observed, but CaO did not crystallize even after prolonged irradiation. Amorphous apatite crystallized to a coarse-grained polycrystalline assemblage of apatite crystallites at 85-200 keV. Increasing the beam current through the sample caused the formation of fine-grained cubic CaO, and the crystallization of apatite was not observed, even at high doses. In each case, many beam-induced bubbles formed and were typically larger at the edge of the beam. Thermal annealing at 450 [degrees]C resulted in epitaxial crystallization from the thick portions of the TEM foil and resulted in a single crystal with a high defect density. Electron-beam irradiations at 300 [degrees]C confirmed that the difference in microstructural evolution as a function of current density is driven by dose-rate effects. In fact, temperature and dose rate are competing effects in the precipitation of CaO.

Crystals of binary (LREE+HREE)-bearing fluorapatite [La,Gd-FAp, Ce,Dy-FAp, Pr, ErFAp, Eu,Lu-FAp; [Ca.sub.10-x-2y][Na.sub.y][REE.sub.x + y][([P.sub.1-x][Si.sub.x][O.sub.4]).sub.6][A.sub.2], with x = 0.12-0.20, y = 0.260.42; [P6.sub.3]/m] have been grown from [H.sub.2]0-rich phosphate-fluoride melts, and their structures refined at room temperature with single-crystal X-ray intensities to R = 0.017-0.022. These binary-REE-substituted fluorapatite samples have REE site-occupancy ratios (REECa2/REE-Cal) of 2.32, and 2.32, 2.03, 1.71, respectively, which are 0.47-0.16 smaller than corresponding ratios calculated using data for reference single-REE-substituted fluorapatite. Discrepancies in intracrystalline partitioning between multiple-REE-substituted apatites and single-REE-substituted fluorapatite decrease with a decrease in REE concentration, becoming negligible at 0.2-0.3 total REE cations pfu in synthetic binary-REE-substituted fluorapatite and at trace abundances of REE in natural apatites. However, quantitative transference of laboratory REE site preferences to natural apatites is frustrated by the compositional complexity in nature. In the synthetic fluorapatite, there is a profound change in the spatial accommodation of REE in the apatite structure at about the position of Nd in the 4f transition-metal series, corresponding to the peak in the experimental uptake curve. Discrepancies in intracrystalline partitioning between binary-REE- and single-REE-substituted fluorapatite are attributed to non-ideal mixing of LREE and HREE that results in contraction of the Cal coordination sphere.

The Central Range of New Guinea is an orogenic belt up to 100 km wide and more than 1300 km long with numerous peaks over 3 km high. The orogen was generated since the middle Miocene by the collisional underthrusting of the northern passive margin of the Australian continent into a north-dipping subduction zone beneath the Melanesian island arc. South of Puncak Jaya, the highest peak in New Guinea, Pliocene-Pleistocene uplift and unroofing have exposed Tertiary carbonates and Mesozoic clastic rocks of a rift and passive-margin sequence above unmetamorphosed Paleozoic strata and green-schist-facies slates probably of Precambrian age. Eight magmatic apatite samples from Pliocene intrusions of intermediate composition in the Gunung Bijih (Ertsberg) mining district at the crest of the Central Range in Irian Jaya, Indonesia, yield pooled fission-track ages ranging between 3.7 [+ or -] 0.9 and 2.0 [+ or -] 0.3 Ma ([+ or -]1[Sigma]). Long etchable mean track lengths (>14 [[micro]meter]) and narrow track length distributions indicate rapid cooling, as expected for shallow-level intrusions. These track-length data and the observation that the Grasberg pluton was emplaced into its own volcanic cover indicate that

Natural apatites used in fertilizer industries often contain trace amounts of Cd, which may reach concentrations of several tens to a few hundred parts per million. Cd is not eliminated during the production of phosphate fertilizers, and its. concentration in the final product can exceed environmental norms. Knowledge of the chemical state of Cd in apatite ores is a prerequisite for the design of technical processes of extraction. In the present study, Cd K-edge EXAFS spectroscopy was used to investigate the structural environment of Cd present in sedimentary apatite ores from West Africa. These apatites are fluorinated and contain goethite, quartz, and crandallite as ancillary phases detected by X-ray diffraction or EXAFS spectroscopy. Cd K-edge EXAFS spectra for two natural samples were analyzed and compared with those for Cd-containing reference minerals, including hydroxylapatite, goethite, otavite, and crandallite. A good spectral resemblance was observed between natural products and synthetic apatite containing small amounts of Cd. This spectral likeness indicates that the majority of Cd atoms are diluted in the apatitic framework and do not form [Cd.sub.10][(P[O.sub.4]).sub.6][(OH, F).sub.2] clusters. This finding was confirmed by quantitative analysis of the EXAFS spectra, which indicated that Cd atoms are surrounded by nearest O atoms at 2.33 [angstrom], next-nearest P atoms at [approximately]3.53 [angstrom], and a third-nearest shell of Ca atoms at [approximately]4.02 [angstrom]. A comparison of these data with those obtained for synthetic apatites allowed us to assess that Cd occupies both Ca crystallographic sites with a slight preference for the Ca2 site.

A series of potassium- and carbonate-containing apatites were prepared by solid state reactions at high temperature, keeping the CO2 atmosphere dry. Analyses of physical and chemical properties showed that the samples are single phase and contain 4-12 wt percent carbonate. The differences in the size of the K+ and Na+ is probably responsible for small differences in the physical properties of K+- and Na+-containing carbonated apatites.

The stoichiometry and the thermal stability of apatites containing K+ and CO(sub 3)(super 2-) were investigated. The apatites have been obtained by the hydrolysis of monetite. The results showed the apatites started to lose carbonate at temperatures below 400 degrees C. The predominant substitution mechanisms for the stoichiometry of the precipitated samples are discussed.

Substitution of Mn5+ for V5+ in apatite crystals results in a laser material operating near 1,200 nm, as confirmed by absorption and emission spectra. The emission occurs from 1E state, making Mn:Sr5(Vo4)3F a three-level system. Strong absorption bands are obtained with an emission cross section of 1 X 10 to the power of minus 19 square cm.

Analysis of the samples produced by the heating of apatites containing Na+ and CO(sub 3)(super 2-), generated by the hydrolysis of monetite, reveals that heating at 400 degrees Celsius removes all the water molecules, without inducing significant constitutional changes. Experimental data enable the determination of the unit cell composition of these apatites. Experimentally determined composition suggests the involvement of two major substitution mechanisms along with a minor mechanism.

Synchrotron x-ray fluorescence microanalysis reveals the heterogeneous distribution of trace elements in apatite crystals that show intrasectoral and sectoral zoning. The sharp compositional differences agree with face symmetry. During growth, the surface structure exhibits a significant influence on the differential partitioning of trace elements into apatite and on the ordering of atoms generating dissymmetrization in apatite. Llallagua apatite samples exhibit optical anomalies that correspond directly to the different sectors and subsectors.