Recrystallization Of Apatite Research Articles

In situ U-Pb dating of Jurassic dinosaur bones from Sichuan Basin, South China

Abstract Direct dating of vertebrate fossils is difficult due to complex postburial diagenetic processes and the often low and heterogeneous concentration of radioisotopes (e.g., U) in fossilized bone material. Here, we demonstrate a novel approach to dating vertebrate fossils via laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of early diagenetic calcite cements precipitated within bone cavities of a Jurassic sauropod from the Sichuan Basin, South China. Early diagenetic calcite yielded a U-Pb age of 165.3 ± 3.6/5.6 Ma, in agreement with a maximum depositional age of 165.8 ± 1.0 Ma from detrital zircon ages of the surrounding rocks, suggesting that diagenesis occurred shortly after the death of the sauropod. This new age demonstrates that the best-known Jurassic large sauropod faunas in South China are much older than those in North America and Africa, suggesting the geographical isolation of South China. Authigenic apatite U-Pb dating on the fibrolamellar bones from the same sauropod gave a distinctly younger age, indicating more complex U-Pb system behavior, possibly due to U uptake by residual organic matter and recrystallization of apatite after early diagenesis. Our findings demonstrate that U-Pb dating of calcite cements within bone cavities has significant potential for constraining the burial age of vertebrate fossils, which could aid in constructing a more robust temporal framework for the radiation and evolution of vertebrates.

Bone diagenesis in the medieval cemetery of Vratislavs’ Palace in Prague

Diagenetic modifications in human bones from the early-medieval cemetery discovered in the garden of Vratislavs’ Palace, in the central Mala Strana district of Prague, have been investigated combining histological analysis and instrumental analysis with X-ray diffraction, infrared, and 31P NMR spectroscopy. A total of 15 ribs samples were collected for the study. One sample belonged to a child, whereas, of the other samples from adults, 7 belonged to males, 5 to females, and for 2 the sex attribution was uncertain. A diagenetic pathway common to most of the studied samples was considered the result of a burial environment characterized by a nearly static water regime, with limited temperature excursions, moderately oxic to suboxic, and with pH fluctuations around the limit of apatite recrystallization window, in agreement with the fine textured clay-rich soil, its low hydraulic conductivity, and the measured soil pH. A second pattern, related to variations in the microenvironment, interested a limited number of samples with poorer histological preservation. This was interpreted as the result of higher pH and a better oxygenated environment, which favoured mineral recrystallization. Further reactivation of deterioration processes probably occurred later in some of the graves perturbed by works conducted in the seventeenth century. This work highlights the complementarity of the information obtained from the adopted techniques in order to gain insights into the post-mortem fate of the human remains and their sedimentary environment. In this respect, the quantification of the amount of phosphorus in the amorphous hydrated layer of apatite provided a unique type of information on the mineral component of bone and its reorganization during diagenesis, revealing that a relevant fraction can survive diagenesis, at variance with what previously supposed.

Geochronologic constraints on deformation and metasomatism along an exhumed mylonitic shear zone using apatite U-Pb, geochemistry, and microtextural analysis

Directly dating and characterizing deformation and metasomatism in fault zones is critical to understanding fault zone processes and lithospheric evolution. Integrated apatite U-Pb geo-thermochronometry, geochemistry, and microtextural analysis has potential to directly date and characterize deformation and fluid-rock interactions in shear zones using a single mineral phase. Integrated apatite U-Pb, microtextural, and trace and rare earth element results from an exhumed mylonitic shear zone, the Main Mylonitic Band in the Northern Pyrenees, constrain timing of deformation and metasomatism along the shear zone as Early Cretaceous, synchronous with ductile deformation and exhumation of middle-lower crustal gneisses in the footwall, and significant mineralization and metasomatism in the brittle hanging wall. Samples from the hanging wall preserve magmatic apatite U-Pb crystallization ages that overlap with zircon and monazite U-Pb ages of ∼300 Ma, granitic geochemical trends, and primary magmatic growth zoning. Footwall samples below the MMB record dynamic recrystallization of apatite associated with mylonitization and exhumation of the gneisses in the Early Cretaceous. Apatite along the MMB record partial recrystallization via dissolution-reprecipitation associated with shearing and circulation of deeply sourced fluids along the shear zone evident by mixed ages (300-100 Ma), geochemical signatures enriched in light rare earth elements, and patchy microtextures. The MMB likely acted as a conduit for deeply sourced fluids that affected the brittle-ductile transition, strain localization, and fluid pathways through the continental crust. This study demonstrates that the integration of apatite U-Pb geo-thermochronology, geochemistry, and microtextural analysis is a powerful approach to dating deformation and metasomatism, characterizing grain scale deformation and (re)crystallization processes, and geochemically characterizing fluid-rock interactions in exhumed middle crustal shear zones.

Recrystallization and chemical changes in apatite in response to hypervelocity impact

Abstract Despite the wide utility of apatite, Ca5(PO4)3(F,Cl,OH), in the geosciences, including tracing volatile abundances on the Moon and Mars, little is known about how the mineral responds to the extreme temperatures and pressures associated with hypervelocity impacts. To address this deficiency, we here present the first microstructural analysis and chemical mapping of shocked apatite from a terrestrial impact crater. Apatite grains from the Paasselkä impact structure, Finland, display intragrain crystal-plastic deformation as well as pervasive recrystallization—the first such report in terrestrial apatite. A partially recrystallized grain offers the opportunity to investigate the effect of shock recrystallization on the chemical composition of apatite. The recrystallized portion of the fluorapatite grain is depleted in Mg and Fe relative to the remnant non-recrystallized domain. Strikingly, the recrystallized region alone hosts inclusions of (Mg,Fe)2(PO4)F, wagnerite or a polymorph thereof. These are interpreted to be a product of phase separation during recrystallization and to be related to the reduced abundances of certain elements in the recrystallized domain. The shock-induced recrystallization of apatite, which we show to be related to changes in the mineral’s chemical composition, is not always readily visible in traditional imaging techniques (such as backscattered electron imaging of polished interior surfaces), thus highlighting the need for correlated microstructural, chemical, and isotopic studies of phosphates. This is particularly relevant for extraterrestrial phosphates that may have been exposed to impacts, and we urge the consideration of microstructural data in the interpretation of the primary or secondary nature of elemental abundances and isotopic compositions.

Nd and Sr Isotope Composition in the Tooth Enamel from Fe–Mn Nodules of the Cape Basin (Atlantic Ocean): Age and Sources

Abstract—The Nd and Sr isotope compositions were determined for the first time in biogenic apatite sampled throughout the tooth section (from the base to tip) of predatory fish in the nucleus of Fe–Mn nodules from the Cape Basin. The results showed that diagenetic recrystallization of apatite does not affect the 87Sr/86Sr ratio in the tooth enamel, but leads to the decrease of Sr content. The age of tooth was determined using Sr isotope stratigraphy at 5.2 ± 0.2 Ma for sample 2188/4 and 6.6 ± 0.3 Ma for sample 2188/5. The calculated growth rate of Fe and Mn oxyhydroxide layers varies within 0.4–2.8 mm per 1 Ma. The 143Nd/144Nd ratio in the tooth enamel varies within single station and depends on the local Nd sources in pore water. The value of eNd varies from –5.2 to –6.9 in the enamel of tooth 2188/4 and remains constant at –8.7 ± 0.1 in sample 2188/5. A change of Nd isotope composition in sample 2188/4 likely reflects temporal variations of Nd fraction from bottom and pore waters that penetrated inside the enamel during REE diffusion. The value of eNd in the oxyhydroxide layers of Fe–Mn nodule 2188/4 (from –7.8 to –7.9) is homogenous for the external and internal parts of the tooth. In order to use eNd in apatite enamel and authigenic Fe and Mn oxyhydroxides in sediments for paleoreconstructions of thermohaline water circulation, it is necessary to develop additional criteria for selecting diagenetically unaltered matter.

DIAGENETIC HISTORY OF WOOLLY MAMMOTH (MAMMUTHUS PRIMIGENIUS) SKELETAL REMAINS FROM THE ARCHAEOLOGICAL SITE CRACOW SPADZISTA STREET (B), SOUTHERN POLAND

Skeletal remains of woolly mammoths have been studied using polarizing microscopy, SEM, XRD, and FTIR to characterize their diagenetic history. Formation of different secondary minerals in the bones is related to changing conditions of chemical diagenesis, both in the sediment and in the bone itself. Bone voids are commonly infilled with calcite and/or carbonate sediment, and dentinal tubules are coated or infilled with secondary apatite. The latter may have formed during the life of the organism. Some osteocyte lacunae were observed to be coated with Fe-Mn (hydroxy)oxides. The average hydroxylapatite Ca/P ratios are higher (1.78–2.10) than in stoichiometric hydroxylapatite. Hydroxylapatite crystallinity indices are generally low at 0.06–0.12, as expected for the young bones. Some of the bones are partly altered by microbial attack. Different postdepositional events affecting the bones (recrystallization of apatite, bacterial alterations, mineral and sediment infillings and cracking) were distinguished and their succession proposed.

THE ROLE OF BACTERIALLY MEDIATED PRECIPITATION IN THE PERMINERALIZATION OF BONE

Bone fossilization is generally thought to be predominantly slow and geochemically controlled, whereas soft-tissue preservation is rapid and microbially enhanced. Microbial destruction of bone has been well researched, but potential preservational influences of microbes on bone are relatively unstudied. Building on previous work, this study examined evidence for microbially induced mineralization of bone buried in a simulated terrestrial setting using an actualistic, experimental approach designed to allow both biotic and abiotic precipitation to occur. Four trials were conducted in 2002 by burying bleached fresh bone cubes in river sand through which calcium carbonate saturated water was percolated. A “natural” trial used unmodified river sediment with natural bacterial populations. Two trials were run with bleach or sodium azide to reduce or eliminate bacterial populations. A fourth trial used washed, bleached sediment with reintroduced bacteria. After one week, the natural trial showed signs of mineral precipitation that cemented sand grains to the bone cubes. Bones from both the natural and washed trials were completely covered by adherent sediment after six weeks. After twelve weeks, cancellous bone in the nonsterile trials was permineralized while antiseptic trials and compact bone showed no indications of permineralization. Nonsterile trials also exhibited partially calcified fungal hyphae and possible lithified bacteria. This study provides additional experimental evidence that microbes are important agents of fossilization for bone as well as soft tissue. It also supports the inference that microbially induced mineral precipitation can play a significant role in bone fossilization by enhancing bone survival through early permineralization until apatite recrystallization occurs.

Polystage apatite recrystallization and svanbergite formation during weathering in an acid karstic environment

AbstractA Devonian weathering profile was developed near the contact of Riphean dolostone containing disseminated carbonate-fluorapatite and intensively pyritized black shales. Samples from the profile were investigated by XRF, SEM, electron microprobe and ion microprobe. Rock-forming minerals are apatite, diaspore, chlorite and kaolinite, while accessory minerals are svanbergite, anatase, pyrite and zircon.Primary marine carbonate-fluorapatite is represented by extremely weathered crystals concentrated near the footwall. Dissolution of apatite and pyrite provided an acidic environment that is expressed in the formation of S-rich apatite and svanbergite. The environment allowed Ti migration which formed anatase in weathered apatite grains. Coupled substitution Na+ + S6+ = Ca2+ + P5+ is suggested in S-rich apatite. A large volume of dissolved carbonate rocks was a source of Sr necessary for svanbergite formation. Apatite of the third generation formed at the final stage of weathering is represented by small (10—30 μm) very well shaped crystals.

Protein release behavior from carbonate apatite hydrogel

Incorporation of protein in poorly crystalline carbonate apatite hydrogel, the protein release behavior from the cake and the dissolution of the cake in aqueous solution were studied. Poorly crystalline apatite was prepared by precipitation of saturated solution of calcium and phosphate in air or under N 2 atmosphere. The carbonate content and particle size of obtained hydrogel depends on the maturation period and atmospheric condition. The mixture of apatite hydrogel and protein was dried for 4 days in air at 40% of relative humidity to yield cakes. The quantity of loaded cytochrome c in apatite hydrogel formed in air was 0.490 wt.%, while that in apatite hydrogel formed under N 2 atmosphere was 0.305 wt.%. But the quantity of loaded albumin in apatite hydrogel formed in air was less than that in apatite hydrogel formed under N 2 atmosphere. For the cakes containing protein immersed in aqueous solution, the protein release was less than the decrease in weight of apatite cake, which may be associated with apatite recrystallization and protein re-incorporation. The quantity of released protein may depend on the quantity of loaded protein in apatite hydrogel.

Rare earth element evolution of Phanerozoic seawater recorded in biogenic apatites

Rare earth element (REE) contents of marine biogenic apatites have been shown to record seawater compositions. A data base of available and newly acquired rare earth element (REE) contents of marine biogenic apatites has been created to assess the past seawater REE compositions. To ensure that this data base contains only the pristine REE signals, altered samples, characterized by very low (La/Sm) N ratios (where N stands for REE ratios normalized to the NASC composition; Gromet et al., 1984, Geochim. Cosmochim. Acta 48 (1984) 2469) acquired during apatite recrystallization, are not included in the database. These data reveal a change in the Tethyan seawater composition between 110 and 80 Ma. After the end of the Cretaceous, the REE chemistry of seawater remains constant until present-day. This seawater composition change is likely due to concurrent changes in REE scavenging processes. A strong correlation between decreasing (Sm/Yb) N ratios and increasing Ce anomalies for samples deposited during the 80–110 Ma period is observed. As Ce anomalies are attributed to ocean water redox conditions, changes in REE scavenging could reflect an evolution from stratified and poorly oxygenated waters towards well-mixed and oxygenated waters. This could have resulted from changing current patterns stemming from the contemporaneous opening of the Atlantic Ocean. A major change in Middle and Late Cretaceous oceanic circulation linked to plate tectonics would have favored the colonization of pelagic environments.

Surface reactivity of calcium phosphate based ceramics in a cell culture system.

Surface reactivity of Calcium Phosphate materials--Hydroxyapatite (HA), Tricalcium Phosphate (beta-TCP), Hydroxyapatite-Tricalcium Phosphate (HA-TCP) were elucidated in a cell culture system. MG-63 osteoblast-like cells were seeded onto the ceramic discs to evaluate changes in the cell morphology and functionality with respect to the different substrates. The dissolution and re-precipitation of calcium phosphate phases on the surface of the discs in the culture medium was found to be prominent on beta-TCP when compared with HA. Low calcium (Ca), magnesium (Mg) and alkaline phosphatase (ALP) levels and high phosphorous (P) levels in the medium of beta-TCP were observed. This indicated that P must have leached out into the medium from beta-TCP and Ca in turn deposited from the medium onto beta-TCP resulting in the apatite phase transformation. The low ALP activity in beta-TCP medium is however an indication of low osteoblastic activity. Under the phase contrast microscope, the osteoblast cells around HA material were found to be confluent and viable, while in the vicinity of beta-TCP only cellular debris was observed. In the case of HA-TCP, only a few viable cells surrounded the material amidst the debris. Scanning electron microscopy revealed numerous cells on the surface of HA showing different cell behaviour like anchorage, attachment, adhesion and spreading in the early time period as the surface was only slightly disturbed with re-crystallisation. But with time the entire surface of HA had changed due to precipitation and re-crystallization which did not support cell behaviour while the cells surrounding the material showed normal growth. On the contrary, cells were scarcely observed on the entirely changed surface of beta-TCP and HA-TCP even from the earlier days of the culture and the morphology of cells surrounding the material too started changing. These results establish that HA promoted the activity of osteoblast cells. HA surface remained unaltered for some time, while the surface of beta-TCP underwent dissolution of surface ions and resulted in the re-crystallization of apatite over the surface. The resulting changes in the surrounding milieu of beta-TCP with high phosphate and low Ca levels probably was responsible for the death of the cells.

Conodont color (CAI) versus microcrystalline and textural changes in upper triassic conodonts from Northwest Germany

Scanning Electron Microscopy on conodonts from the Middle Triassic “Trochitenkalk” from Northwest Germany with CAI values ranging from 1 to 5 revealed structural alterations during progressive diagenesis. Conodonts with low CAI values of 1.5 already show syntaxial recrystallization of apatite on the conodont surface. Aggrading crystallization of the internal structure occurs in conodonts with CAI=5. The usually short-prismatic and blocky syntaxial crystallites become increasingly longer and an overall increase in crystallite size takes place. Conodonts from the telemagmatically heated sediments overlying the intrusive body of the Vlotho Massiv are often corroded, i.e., they have pocked, frosted to pitted surfaces with dolomite rhomb overgrowths, indicating contact with ascending dolomitizing brines.

Moderate pressure metamorphism and anatexis due to anorthosite intrusion, western Adirondack Highlands, New York

Garnet-sillimanite-biotite gneiss near Port Leyden, in the western Adirondack Highlands, New York, contains mineral assemblages and textures that formed during high temperature metamorphism and anatexis at mid-crustal pressures. Evidence for melting includes thin, plagioclase-rich veins, sieve textures in biotite, and the presence of small, euhedral garnet neoblasts. Hercynite-silicate equilibria in combination with the solidus for biotite dehydration melting indicate metamorphic pressure was between 4 and 6.4 kbar at the temperature of melting (ca. 735° C). The gneiss is intruded by a small, discordant Fe-Ti oxide-apatite (nelsonite) dike. Reported field occurrences of nelsonite demonstrate its common association with anorthosite plutons. Although no anorthosite bodies are exposed in the Port Leyden region, the presence of nelsonite is evidence of anorthositic magmatism in the western Adirondacks. Post-intrusion metamorphism has caused partial apatite recrystallization and produced a weak foliated texture in the dike. U-Pb ages from zircon and monazite from both the gneiss and the nelsonite dike indicate that these rocks experienced a complex, polymetamorphic history that we interpret to reflect two thermal episodes. An older event is recorded by discordant zircons in the gneiss, which indicate a minimum age of 1129±6 Ma. A linear best fit to the data yields an upper intercept at 1166±53 Ma. This range of ages coincides with anorthosite-suite magmatism in the Adirondacks. A minimum zircon age of 1104±3 Ma was obtained from the nelsonite dike. Lead-loss or late zircon crystallization at about 1020 Ma affected the U-Pb systematics of zircon in the dike. Monazite ages from both rocks also indicate high temperature metamorphism (>700° C) between 1040 and 960 Ma. The older zircon ages and textural relations in the metapelite are viewed as evidence for anatexis at ca. 1150 Ma, and the presence of nelsonite suggests that the intrusion of anorthosite was coincident with partial melting in the gneiss. P-T estimates of metamorphism, therefore, imply that anorthosite was emplaced to about 15 km depth in the western Adirondack Highlands.

Diagenesis of Strontium in Fossil Bone: A Reconsideration of Nelson et al.(1986)

In experiments on marine animal fossils that had been buried in terrestrial sediments, Nelson et al.(1986, Geochimica et Cosmochimica Acta 50:1941-1949) reported that the strontium (Sr) of prehistoric bone had nearly completely exchanged with that of the burial environment, and therefore cannot be used for paleodietary reconstruction. However, Sealy et al.(1991, Journal of Archaeological Science 18:399-416), using a solubility profile procedure, reported that it was possible to remove diagenetic Sr and obtain biologically meaningful Sr. Nevertheless, the Nelson et al.study is often cited as evidence that a biological signal is irretrievable. Here infra-red spectrometry, XRD spectrometry and elemental analyses were used to compare the effects of the Nelson et al.protocol with the solubility profile protocol on the crystal structure and crystallinity of the bone and fossil specimens. The results show that the procedures used by Nelson et al., which include a preliminary ashing step, result in severe recrystallization of apatite both before and during the leaching step, which deleteriously affects any attempt to recover biological Sr. By contrast no observable recrystallization takes place in the solubility profile procedure. The results imply that the conclusions reached by Nelson et al.are primarily artefacts of the specific methods used in their study, rather than due to any inherent mechanism of diagenesis.