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Abstract: An occurrence of diagenetic fluorapatite cement is documented within the Cambro-Ordovician Keeseville Formation, Potsdam Group, near Chateaugay in New York State. The fluorapatite cement occurs as stratiform layers within [...]

Measurement of detrital zircon U-Pb ages has become the method of choice for single crystal--based investigations of provenance for both modern and ancient sediments. Recent studies, however, demonstrated the failure of zircon to record major tectonic events in source terranes, revealing the need for a more robust provenance methodology. A direct comparison between the utility of crystallization ages of detrital zircon and monazite as provenance indicators has been made using modern river alluvium derived from known sources. While detrital zircon does not fully record the multiple coilisional phases that are the hallmark of the Appalachian orogen, detrital monazite accurately records all the major tectonic events. The physical and petrogenetic differences between zircon and monazite are the primary factors for differing detrital age spectra. Zircon, owing to its extreme refractory nature, skews detrital age spectra toward older ages and limits its ability to record low-grade thermotectonic events in orogens. Monazite recrystallizes over a broader range of metamorphic conditions than does zircon. Consequently, monazite has the potential to record metamorphic events that might otherwise be absent from the detrital zircon record, thus providing a more accurate record of source terranes in regions characterized by moderate thermal events. doi: 10.1130/G30265.1

We investigated dehydration processes in uranyl phosphate minerals of the meta-autunite group that consist of uranyl phosphate sheets and interlayer cations, and water molecules. Meta-autunite [Ca[(U[O.sub.2]P[O.sub.4]).sub.2]-6[H.sub.2]0], metasaleeite [Mg[(U[O.sub.2]P[O.sub.4]).sub.2] * 8[H.sub.2]O], and metatorbernite [Mg[(U[O.sub.2]P[O.sub.4]).sub.2] * 8[H.sub.2]O] were selected for our study. The change in basal spacing between two adjacent uranyl phosphate sheets with temperature was examined by temperature-controlled X-ray diffraction (XRD) analysis from room temperature (RT) to 300 [degrees]C to determine structurally distinct, dehydrated phases. Thermogravimetric and differential thermal analyses (TG/DTA) were also performed under conditions similar to those used for the XRD analysis to clarify the hydration states of the dehydrated phases. Retention of the structure of the uranyl phosphate sheets under a high vacuum, equivalent to 300 [degrees]C, was confirmed by transmission electron microscopy. Meta-autunite, metasaleeite, and metatorbernite decreased their basal spacings by losing water molecules. Comparison of the TG/DTA and XRD results indicates that the changes in basal spacings of the dehydrated phases with temperature are as follows: 8.32 [Angstrom] (6 [H.sub.2]O per unit formula) at RT, 7.31 (? [H.sub.2]O) and 6.68 [Angstrom] (? [H.sub.2]O) at 75 [degrees]C, 6.34 [Angstrom] (2 [H.sub.2]O) at 120 [degrees]C, and 5.81 [Angstrom] (1 [H.sub.2]O) at 300 [degrees]C for meta-autunite; 8.29 (8 [H.sub.2]O) and 7.73 [Angstrom] (? [H.sub.2]O) at RT, 6.62 [Angstrom] (probably, 2 [H.sub.2]O) at 40 [degrees]C, 6.54 [Angstrom] (2 [H.sub.2]O) at 160 [degrees]C, and 5.52 [Angstrom] (1 [H.sub.2]O) at 300 [degrees]C for metasaleeite; and 8.61 (8 [H.sub.2]O) at RT, 8.07 [Angstrom] (4 [H.sub.2]O) at 100 [degrees]C, 6.58 [Angstrom] (2 [H.sub.2]O) at 200 [degrees]C, and 5.60 [Angstrom] (1 [H.sub.2]O) at 300 [degrees]C for metatorbernite. The dehydration processes revealed by XRD and TG/DTA under similar experimental conditions are slightly different from those obtained by previous studies. Our results clearly demonstrate the presence of previously unknown dehydrated phases of the meta-autunite group minerals with basal spacings less than 6 [Angstrom] that may have distinct thermodynamic properties.

Abstract Nitrogen (N) is the main fertiliser input to tea plantations because of the large removal of this element with regular harvests of young shoots in the field. The form [...]

Coal combustion by-product (CCBP; a wallboard-quality gypsum), limestone, and cellulose had been found to influence the dissolution of North Carolina phosphate rock (NCPR) in an acid Lily loam soil (fine-loamy, siliceous, mesic Typic Hapludult). Laboratory and incubation experiments were carried out in this study to elucidate the mechanisms responsible for the reduced dissolution of NCPR from CCBP application. The major factors responsible for the reduced PR dissolution were (i) an increase in exchangeable Ca + Mg derived from the CCBP, (ii) an increase in soil pH from the small amounts of CaC[O.sub.3] in the CCBP material; and (iii) sulfate released from the CCBP resulting in a decrease in P sorption capacity of the amended soil due to competitive sorption between sulfate and phosphate. The further reduction in NCPR dissolution by limestone addition was probably due to the increase in pH and exchangeable Ca relative to CCBP application alone. An increased NCPR dissolution from cellulose addition probably reflected an accelerated depletion of labile P by the cellulose-induced microbial growth and, hence, biomass production. The four kinetic dissolution parameters, i.e., the half-life ([t.sub.1/2]) from a first-order rate equation, the initial dissolution rate- and the average dissolution rate-related constants (A and b) from an Elovich equation, and the potential maximum dissolution of phosphate rock from a Langmuir equation were significantly correlated with pH, the content of exchangeable (Ca + Mg), and P sorption capacity of the CCBP-amended soil. The [t.sub.1/2] and A of NCPR in the acid soil could be predicted with 95% confidence by the three soil variables, i.e, soil pH, P sorption capacity, and exchangeable (Ca + Mg). Both [t.sub.1/2] and A could serve as an indicator of the NCPR dissolution potential in soils.

Phosphate rock (PR), coal combustion by-product (CCBP), limestone, and organic materials are promising amendments for low P, acid soils, and two or more of the amendments are commonly applied to improve crop yields in acid soil. However, the interactions between these amendments in acid soil are not fully understood. The effects of CCBP, limestone, and cellulose application on dissolution of North Carolina phosphate rock (NCPR) in an acid Lily loam (fine-loamy, siliceous, mesicTypic Hapludult) from West Virginia were examined in an incubation study. Based on the [Delta]P-NaOH estimation method, [approximately equal to]30% of the added NCPR was dissolved after 60 d of incubation. The NCPR dissolution decreased drastically with increasing rate of CCBP, particularly when it was applied together with limestone, whereas cellulose addition tended to enhance NCPR dissolution. Dissolution of NCPR was well described by first-order, Elovich, and Langmuir kinetic equations. The average [r.sup.2] values between the experimental data of NCPR dissolution and the three models were [0.829.sup.*], [0.851.sup.**], and [0.930.sup.**], respectively, for 17 soil samples with and without amendments. Half-life ([t.sub.1/2]) from the first-order reaction could be employed as a simple measure of the NCPR dissolution rate. Constants A and b derived from the Elovich equation were related to the initial and average dissolution rate of NCPR. The potential maximum dissolution of PR from the Langmuir equation provided an estimate of the dissolution extent of NCPR. All four kinetic parameters, particularly [t.sub.1/2] and A, were closely correlated with CCBP application rates. These parameters appeared useful in evaluating the effects of CCBP application on NCPR dissolution in the acid soil and might also be applicable to predicting PR dissolution for a wide range of soils with different properties.

Microfacies analysis (using optical and backscattered electron imagery) has been undertaken on 37 samples from the Cleveland Ironstone Formation, Staithes, Yorkshire, UK. Four lithofacies were encountered: clay-rich mudstones, silt-rich mudstones, sand-rich mudstones and concretionary carbonates (two types: berthierine/siderite-rich ironstones and apatite-rich concretionary horizons). Successive units were found to stack systematically into upward-coarsening units on a small (0.1-1.0m) scale. Upward-coarsening and upward fining packages were also found on a larger (1.0-3.0 m) scale. The small-scale upward-coarsening units are interpreted to be parasequences; while the large scale upward-fining and upward-coarsening packages are interpreted to be retrogradational and progradational parasequence sets respectively. The ironstones occur at the level where the stacking patterns change from being overall progradational to retrogradational, while the apatite-rich concretionary units occur at the level where the stacking patterns change from being retrogradational to progradational. The concretionary carbonates are interpreted to have formed close to/at major stratal surfaces. The ironstones are interpreted to be either the correlative equivalent of sequence boundaries or part/all, of the forced regressive system tract; while the apatite-rich units are interpreted to have precipitated close to/at maximum flooding surfaces (condensed sections) and/or major transgressive surfaces. Keywords: United Kingdom, mudstone, ironstone, phosphate rocks, sequence stratigraphy.

Quantitative estimation of the enhancement effect of water-soluble P on P availability from phosphate rock (PR) has not been reported. The objective of this study was to use radioactive 32P as a tracer to distinguish P availability from soil, PR, and TSP so that P uptake by crops from PR in the presence of TSP could be estimated. Three sets of 4-kg soil samples of an acid Hartsells silt loam (fine-loamy, siliceous, thermic Typic Hapludult, pH 4.8) were mixed with the following treatments: (i) 32P solution and central Florida PR (CFPR), (ii) 32P-tagged TSP, and (iii) 32P-tagged TSP and CFPR at a P ratio of 50:50. The rates of P applied were 0, 12.5, 25, 50, 100, and 200 mg P [kg.sup.-1]. For treatment (iii), an additional rate of 400 mg P [kg.sup.-1] was also prepared. Maize (Zea mays L.) and cowpea (Vigna unguiculata [L.] Walp. ssp. unguiculata) were planted and harvested at 42 d after planting for maize and 45 d for cowpea. The effectiveness of P sources in terms of increasing dry-matter yield and P uptake followed the order of TSP [greater than or equal to] (CFPR + TSP) > CFPR for maize and TSP = (CFPR + TSP) > CFPR for cowpea. Phosphorus uptake from CFPR in the presence of TSP was higher than P uptake from CFPR applied alone, indicating an enhancement effect of TSP on the effectiveness of CFPR. The increase in P uptake from CFPR due to TSP influence, across all the PR rates applied, was 3.48 mg P [pot.sup.-1] for maize and 1.38 mg P [pot.sup.-1] for cowpea. With respect to P uptake from CFPR applied alone, the corresponding relative increase in P uptake from CFPR due to TSP influence was 165% for maize and 72% for cowpea.

A greenhouse experiment was conducted to study the influence of Fe and Al oxide in phosphate rocks (PR) on partially acidulated phosphate rock (PAPR) effectiveness and to evaluate compaction of PR with soluble phosphates as an alternate method of utilizing PR with high Fe and Al oxide. Five PR with Fe + Al oxide ranging from 19 to 320 g [kg.sup-1] were acidulated with 50% of the H2SO4 (PAPR, 50% required to fully convert the PR to triple superphosphate (TSP) or were compacted with TSP so that 50% of the total P was in TSP form (PR + TSP). They were applied to Hartsells silt loam (fine-loamy, siliceous, thermic Typic Hapluduh, pH 4.8) at rates 50, 100, 200, and 300 mg P [kg.sup-1]. Two successive crops of maize (Zea mays L.) and one of rice (Oryza sativa L.) were grown. Biomass yield of the first crop from PAPR-treated soils decreased from 86% of that from TSP to 16% and P uptake from 72 to 12% with increasing Fe and Al oxide from 1.9 to 32%. The decrease in effectiveness of PAPR was directly related to a decreage in water-soluble P in PAPR with increasing Fe and Al oxide content. The compacted PR = TSP were 86 to 104% as effective as TSP in increasing biomass yield and 78 to 94% as effective in increasing P uptake. There were no great differences between PAPR and the compacted PR + TSP in terms of residual effect on the second crop of maize, except for Matongo PR. The difference in residual effectiveness between PAPR and compacted PR + TSP was not as pronounced for rice as for maize.

Phosphate rock (PR) and pyrite deposits, indigenous to many African countries, may be useful to resource-poor farmers for increasing the P and S fertility of highly weathered tropical soils. Combination of PR and pyrite was examined as a means to increase the availability of P from five PR of African origin. Pyrite and PR were combined in several ratios (P/S) and incubated. Mixtures were periodically leached on a vacuum extractor with 0.01 M KC1 for a 6-mo period. Soluble P and pH of the leachate were measured. The pH of the leachates decreased with increasing levels of pyrite. In all cases, soluble P measured in the leachate increased with increasing levels of pyrite. Soluble P measured in the leachate was greatest from Togo and Uganda PR mixtures, much less from Zimbabwe PR, and virtually nil in all but the highest pyrite treatments for both Tanzania and Malawi PR mixtures. Citrate-soluble P was a less reliable predictor of P release than total P and the percentage of [CO.sib.2], A1, and Fe in the PR and associated minerals. High pyrite levels with low-quality rocks generated P release comparable with that from untreated high-quality rocks. The addition of Fe from the pyrite apparently did not lead to precipitation of substantial amounts of P as it was released from PR. The rocks responded very differently to the pyrite treatment. Although the method is promising for some rocks (Togo and Uganda), it is obviously not useful for other rocks Malawi).

Phosphogenesis is major sink for phosphorus (P) in the modern ocean, and the deposition of ancient phosphorites appears to have been an important sink for P in past oceans. To evaluate the importance of P burial we combined published estimates (along with our data for one section of the Monterey Formation, California) of P inventories, areal extent, and time intervals of deposition for three well-studied major phosporite deposits to calculate P accumulation and burial rates. Phosphorus accumulation and burial rates of major phosphorite deposits are comparable to those of the modern Peru margin. Though phosphorite deposition probably requires favorable sedimentological, tectonic, and/or oceanographic conditions, it does not appear to be a geochemically anomalous phenomenon when compared to modern oceanic conditions.

The dissolution of two types of phosphate rock (PR) of different chemical reactivity in two systems was compared, and the effect of calcium (Ca) released from the phosphate rock on cation movement in soils was documented. Open-leaching systems provided a higher degree of dissolution for both PR materials than closed-incubation systems. This was attributed to removal of ionic calcium by leaching with near-complete dissolution of Christmas Island A phosphate rock. The Ca released from PR occupies exchange sites in the soil, thus increasing soil pH and cation-exchange capacity.

The enormous phosphorite deposits of the southeastern United States indicate intense upwelling but contain small amounts of organic carbon. We propose that deposition of organic-rich sediment on continental shelves in the southeastern United States and elsewhere during marine transgressions in the late Oligocene and early to middle Miocene resulted in global positive [delta sup.13]C shifts and the formation of early diagenetic phosphorite. Multiple reworking and supergene weathering from subaerial exposure during Miocene marine regressions oxidized most of the organic carbon and resulted in the return of [delta sup.13]C to its preexcursion value. The estimated phosphorite content of the southeastern United States requires sufficient organic carbon burial ([>10 sup.15] kg carbon) to support a 1 0/00 [[delta] sup.13]C excursion. We believe that our hypothesis may explain the relation among [[delta] sup.13]C excursions, sea-level fluctuations, organic carbon burial, phosphogenic episodes, and possibly global cooling during the Cenozoic.

The coast of Namibia is dominantly made up of shell fragments of the inarticulate brachiopod Discinisca. The situation is analogous to the occurrence of similar organisms in the phosphate-rich Obolus Conglomerate unit of the Ordovician Kallavere Formation in northern Estonia. Occurrence of phosphorite deposits in the Namibian coast is attributed to the upwelling of phosphite-rich water, the Benguela system, which encourages the abundance of organisms secreting phosphate rich shells. A similar paleo-upwelling system is being postulated to explain the Estonian deposits.

In a series of timed experiments, monazite inclusions are induced to form in the Durango fluorapatite using 1 and 2 N HC1 and [H.sub.2]S[O.sub.4] solutions at temperatures of 300, 600, and 900 [degrees]C and pressures of 500 and 1,000 MPa. The monazite inclusions form only in reacted areas, i.e. depleted in (Y+REE)+Si+Na+S+Cl. In the HC1 experiments, the reaction front between the reacted and unreacted regions is sharp, whereas in the [H.sub.2]S[O.sub.4] experiments it ranges from sharp to diffuse. In the 1 N HC1 experiments, Ostwald ripening of the monazite inclusions took place both as a function of increased reaction time as well as increased temperature and pressure. Monazite growth was more sluggish in the [H.sub.2]S[O.sub.4] experiments. Transmission electron microscopic (TEM) investigation of foils cut across the reaction boundary in a fluorapatite from the 1 N HCI experiment (600[degrees]C and 500 MPa) indicate that the reacted region along the reaction front is characterized by numerous, sub-parallel, 10-20 nm diameter nano-channels. TEM investigation of foils cut from a reacted region in a fluorapatite from the 1 N [H.sub.2]S[O.sub.4] experiment at 900[degrees]C and 1,000 MPa indicates a pervasive nano-porosity, with the monazite inclusions being in direct contact with the surrounding fluorapatite. For either set of experiments, reacted areas in the fluorapatite are interpreted as replacement reactions, which proceed via a moving interface or reaction front associated with what is essentially a simultaneous dissolution-reprecipitation process. The formation of a micro- and nano-porosity in the metasomatised regions of the fluorapatite allows fluids to permeate the reacted areas. This permits rapid mass transfer in the form of fluid-aided diffusion of cations to and from the growing monazite inclusions. Nano-channels and nano-pores also serve as sites for nucleation and the subsequent growth of the monazite inclusions.

Apatitic rock phosphates (RP) are commonly calcined to remove impurities and to increase phosphorus (P) concentration but calcination decreases the agronomic effectiveness of RPs used for direct application to soils. This study investigated the effect of calcination on 6 apatite RPs (Christmas Island A-ore, Egypt, Morocco, North Carolina, Queensland, and Sechura). RPs were uncalcined (25 ° C) and calcined at 500 ° C, 900 ° C, and 1100 ° C. They were evaluated by X-ray diffraction (XRD) and BET-[N.sub.2] surface area technique. P dissolution in 2% citric acid with a 128 h extraction time was measured. Chemical results were compared with those from a plant growth experiment, where wheat was fertilised with the calcined RP products. Calcination at 1100 ° C reduced the agronomic effectiveness of apatite RPs by about 90%, by altering the crystal properties and the particle size of the RPs. Unit-cell a dimension increased from values of 9.3249.375 Å to approximately 9.38 Å, indicating that the carbonate containing apatite RPs altered to less-soluble fluorapatite. Apatite average crystal size (coherently diffracting zone) more than doubled and BET-[N.sub.2] specific surface area decreased by 95%, due to crystal growth and sintering. Consequently, the extent of dissolution in 2% citric acid and agronomic effectiveness decreased substantially. Calcination at 500 ° C and 900 ° C produced similar but smaller changes in mineral properties. It is concluded that beneficiation of apatitic RP by calcination will adversely affect the agronomic effectiveness of RP used for direct application to soils., Introduction Most rock phosphates (RPs) are apatite-bearing rocks that contain enough phosphorus (P) to be utilised for the manufacture of fertilisers, elemental P, and/or phosphoric acid (Gary et al. 1974). [...]

The Meishucun Section (Yunnan Province, South China) is considered to be an important Precambrian-Cambrian boundary section, primarily because of its rich small shelly fossil record. In this article, we report the results of a sulphur isotope study of phosphate-bound sulphate from the Meishucun Section and several correlative sections in South China. Forty clastic, granular phosphorites from Meishucun yield tightly grouped [Delta]34S values averaging 33[per thousand] (CDT), which agree well with published evaporite data for the lower Cambrian of Siberia and elsewhere. We argue that these strongly positive values reflect the sulphur isotopic composition of ambient seawater, confirming further the existence of uniquely high [Delta]34S values in the earliest Cambrian oceans. This novel use of trace-sulphate in phosphate to constrain seawater [Delta]34S represents the first time that sulphate [Delta]34S data for this period have been given precise biostratigraphic assignments. Superimposed on the overall trend are short-term, stratigraphic variations, which might reflect local variations in the sedimentary and early diagenetic environment. Our data, together with other published data, indicate that seawater sulphate [Delta]34S rose from low values (15-20%o) during the pre-750 Ma Proterozoic to possibly all-time high values (>32%o) by the earliest Cambrian. We argue that this rise may, in part, relate to increases in the amount of sulphur isotopic discrimination during microbially mediated sulphate reduction as a result of increased sulphide reoxidation. On the other hand, the Neoproterozoic trend to high [Delta]34S values appears to mirror a trend to decreasing seawater [Delta]13C towards the Proterozoic-Phanerozoic transition, implying progressive increases in the efficiency of organic carbon recycling, which would normally be coupled with real increases in sulphate reduction on the global scale. We consider that both these changes in biogeochemical cycling derive ultimately from the introduction of macrofauna around this time and, in particular, from the influence of bioturbation on early diagenesis. Precise constraints on S-isotopic evolution during the Neoproterozoic require additional trace sulphate studies. Keywords: Cambrian, China, S isotopes, seawater, phosphorites.