Lithologic, mineral, chemical and isotopic compositions of altered rocks with increasing distance across the eastern flank of the Juan de Fuca Ridge, ODP Leg 168 data

During ODP Leg 168, 10 sites were drilled across the eastern flank of the Juan de Fuca Ridge (JdFR), to examine the conditions of fluid-rock interaction in three distinct hydrothermal regimes (referred to as the Hydrothermal Transition (HT), Buried Basement (BB) and Rough Basement (RB) transects), extending over a ~120 km linear transect perpendicular to the spreading ridge. This was carried out in an attempt to constrain the conditions and processes that control the location, style and magnitude of low temperature (<150°C) fluid-rock interaction within this setting. This paper presents new data on the petrology, mineral chemistry and whole rock strontium and oxygen isotopic compositions of basalts from the eastern flank of the JdFR, in order to investigate the extent, style and sequence of low-temperature hydrothermal alteration and to establish how the hydrothermal regime evolved with time. Throughout the flank, a progressive sequence of low-temperature hydrothermal alteration has been identified, marked by changes in the dominant secondary mineral assemblage, changing from: chlorite+chlorite/smectite; to iron oyxhydroxide+celadonite; to saponite+/-pyrite; culminating at present with Ca- to CaMg(+/-Fe,Mn)-carbonate. The changes in secondary mineralogy have been used to infer a series of systematic shifts in the conditions of alteration that occurred as the basement moved off-axis and was progressively buried by sediment. In general, hydrothermal alteration of the uppermost oceanic crust commenced under open, oxidative conditions, with interaction between unmodified to slightly modified seawater and basaltic crust, to a regime in which circulation of a strongly modified seawater-derived fluid was more restricted, and alteration occurred under non-oxidative conditions. Across the flank, petrological observations and microprobe analyses indicate that the observed ranges in secondary mineral composition are directly related to changes in the geochemical and textural characteristics of the basement, as well as to interaction between fluids and phases from the four stages of alteration. This is suggestive of an increase in fluid-rock increased with time. Whole rock 87Sr/86Sr and d18O analyses of basalts from across the eastern flank of the JdFR reinforce petrological observations, with 87Sr/86Sr and d18O values slightly elevated above accepted pristine MORB values for this region. These results are consistent with an increase in the amount of fluid-rock interaction with time. Across the flank, enrichment in the 87Sr/86Sr and d18O relative to MORB, is influenced by a number of factors, including: local and regional variations in the crustal lithology and structure; the age of the crust; the extent of bulk rock alteration; and theoretically, the relative abundance of different isotopically-enriched secondary mineral phases in the crust.

Geochemistry and Fe/(Ti + Ti), x, Curie temperature, and oxidation parameter z at DSDP Hole 597C

Electron microprobe and thermomagnetic analyses of selected basalt samples from Hole 597C were performed. The main purpose of this work was to investigate and estimate the degree of oxidation of the samples using the ratios of Fe to Ti and the Curie temperatures obtained from thermomagnetic curves. The results show that the magnetic properties of samples from Hole 597C change at a sub-bottom depth of 100 m, and that low-temperature and high-temperature oxidation processes prevailed above and below 100 m, respectively.

Geochemistry of basement basaltic rocks of ODP Hole 131-808C

Major- and trace-element analyses, mineral chemistry, and Sr-Nd isotopic determinations were obtained on representative igneous rocks drilled from the Nankai accretionary complex (Site 808) during Ocean Drilling Program Leg 131. For the first time, the oceanic basement of the subducting plate below an accretionary prism has been reached. The Nankai Trough basement was encountered at a depth of 1289.9 mbsf and a total of 37.1 m of igneous rocks, middle Miocene (15.6 Ma) in age, was penetrated. Two main lithological units have been distinguished from the top downward; sill-like rocks (Unit I: Cores 105, 106, 107) and pillow lavas (Unit II: Core 108). Basalts are predominantly nonvesicular, hypocrystalline, aphyric to slightly phyric with intersertal to intergranular textures. Alteration is generally slight to moderate. All the basaltic rocks are cut by ramifying veins of varying widths. Secondary mineral assemblages (including vein fillings) are typical of submarine alteration and zeolite to low greenschist facies metamorphism. The order of crystallization of primary minerals is: olivine, plagioclase, clinopyroxene. This, together with mineral chemistry, characterized by forsteritic olivine (Fo 84-85), highly anorthitic Plagioclase (up to An 90), and in particular the composition of clinopyroxene, are typical of normal mid-ocean ridge basalts (MORB). In terms of Zr/Y (2.9-3.8) and Zr/Nb (21-58), all the analyzed samples plot in the normal MORB field. The chondrite-normalized REE patterns confirm the close affinity with normal MORB type (LaN/SmN: 0.6-0.8). Note that such magmatism does not reveal any evidence of subduction-related geochemical components. The 87Sr/86Sr isotopic ratios range from 0.70339 in pillow lavas to 0.70317 in the least-altered basalts of sill units (ratios reduced to 0.70265-0.70271 by HC1 2.5 N hot leaching), whereas 143Nd/144Nd ratios are 0.51314-0.51326. These values conform with those of normal MORB. Stratigraphy, petrography, and geochemistry of the basaltic rocks recovered at Site 808 appear very similar to those from the Shikoku Basin basement (particularly Sites 442 and 443, DSDP Leg 58), analogously identified as normal MORB.

Geochemistry in the mid Atlantic Ocean ridge basalts

The main objective of Leg 82 of the Glomar Challenger was to document mantle heterogeneity in the vicinity of, and away from, a so-called hot spot: the Azores Triple Junction. One of the geochemical tools that permits, at least in part, the recognition of mantle heterogeneities uses hygromagmaphile elements, those elements that have an affinity for the liquid. This tool is presented in terms of an extended Coryell-Masuda plot, which incorporates within the rare earth elements the hygromagmaphile transition elements Th, Ta, Zr, Hf, Ti, Y, and V. The extended Coryell-Masuda plot is used to summarize our knowledge of mantle heterogeneity along the ridge axis at zero-age. It is also used by choosing those hygromagmaphile elements that can be analyzed on board by X-ray fluorescence spectrometry to give preliminary information on the enriched or depleted character of recovered samples. Shore-based results, which include analyses of most of the hygromagmaphile elements measured either by X-ray spectrometry or neutron activation analysis, confirm the shipboard data. From the point of view of comparative geochemistry, the variety of basalts recovered during Leg 82 provides a good opportunity to test and verify the classification of the hygromagmaphile elements. Analyses from Leg 82 provide new data about the relationship between extended rare earth patterns (enriched or depleted) that can be estimated either by La/Sm ratio or Nb/Zr (or Ta/Hf) ratios: samples from Hole 556 are depleted (low Nb/Zr ratio) but have a high 206Pb/ 204Pb (19.5) ratio; in Hole 558 a moderately enriched basalt unit with a La/Sm (= Nb/Zr) ratio (chondrite normalized) of 2 has a high 206Pb/204Pb (20) ratio. One of the most interesting results of Leg 82 lies in the crossing patterns of extended Coryell-Masuda plots for basalts from the same hole. This result enhances the notion of local mantle heterogeneity versus regional mantle heterogeneity and is confirmed by isotope data; it also favors a model of short-lived, discrete magma chambers. The data tend to confirm the Hayes Fracture Zone as a southern limit for the influence of Azores-type mantle. Nevertheless, north of the Hayes Fracture Zone, the influence of a plumelike mantle source is not simple and probably requires an explanation more complex than a contribution from a single fixed hot spot.

Geochemical composition of calcite and aragonite, and characteristics of hydrothermal fluids of ODP Leg 168 sites

During Leg 168 a transect was drilled across the eastern flank of the Juan de Fuca Ridge in an area where the volcanic basement is covered by sediments of variable thickness. Samples of basement volcanic rocks were recovered from nine locations along the transect, where the basement sediment interface is presently heated to temperatures varying from 15° to 64°C. Altered rocks with secondary calcium carbonate were common at four of the sites, where present-day temperatures range from 38° to 64°C. Fluid inclusions in aragonite suggest that the mineral precipitated from an aqueous fluid of seawater salinity at temperatures well below 100°C. The chemical compositions of secondary calcite and aragonite were determined with both an electron microprobe and a laser-ablation inductively coupled plasma-mass spectroscopy (LA-ICP-MS) microprobe. These two techniques yielded consistent analyses of the same minor elements (Mg and Sr) in the same specimens. The combined results show that secondary aragonites contain very little Mg, Mn, Fe, Co, Ni, Cu, Zn, Rb, La, Ce, Pb, or U, yet they contain significant Sr. In contrast, secondary calcites contain significant Mg, Mn, Fe, Ni, Cu, Zn, and Pb, yet very little Co, Rb, Sr, La, Ce, or U. Secondary calcium carbonates provide subseafloor reservoirs for some minor and trace elements. Replacement of aragonite by calcite should result in a release of Sr, Rb, and Zn to solution, and it provides a sink for Mg, Mn, Ni, Cu, Zn, and Pb.

Geochemistry of ODP Hole 176-735B igneous and hydrothermal veins

During Legs 118 and 176, Ocean Drilling Program Hole 735B, located on Atlantis Bank on the Southwest Indian Ridge, was drilled to a total depth of 1508 meters below seafloor (mbsf) with nearly 87% recovery. The recovered core provides a unique section of oceanic Layer 3 produced at an ultraslow spreading ridge. Metamorphism and alteration are extensive in the section but decrease markedly downward. Both magmatic and hydrothermal veins are present in the core, and these were active conduits for melt and fluid in the crust. We have identified seven major types of veins in the core: felsic and plagioclase rich, plagioclase + amphibole, amphibole, diopside and diopside + plagioclase, smectite ± prehnite ± carbonate, zeolite ± prehnite ± carbonate, and carbonate. A few epidote and chlorite veins are also present but are volumetrically insignificant. Amphibole veins are most abundant in the upper 50 m of the core and disappear entirely below 520 mbsf. Felsic and plagioclase ± amphibole ± diopside veins dominate between ~50 and 800 mbsf, and low-temperature smectite, zeolite, and prehnite veins are present in the lower 500 m of the core. Carbonate veinlets are randomly present throughout the core but are most abundant in the lower portions. The amphibole veins are closely associated with zones of intense crystal plastic deformation formed at the brittle/ductile boundary at temperatures above 700°C. The felsic and plagioclase-rich veins were formed originally by late magmatic fluids at temperatures above 800°C, but nearly all of these have been overprinted by intense hydrothermal alteration at temperatures between 300° and 600°C. The zeolite, prehnite, and smectite veins formed at temperatures <100°C. The chemistry of the felsic veins closely reflects their dominant minerals, chiefly plagioclase and amphibole. The plagioclase is highly zoned with cores of calcic andesine and rims of sodic oligoclase or albite. In the felsic veins the amphibole ranges from magnesio-hornblende to actinolite or ferro-actinolite, whereas in the monomineralic amphibole veins it is largely edenite and magnesio-hornblende. Diopside has a very narrow range of composition but does exhibit some zoning in Fe and Mg. The felsic and plagioclase-rich veins were originally intruded during brittle fracture at the ridge crest. The monomineralic amphibole veins also formed near the ridge axis during detachment faulting at a time of low magmatic activity. The overprinting of the igneous veins and the formation of the hydrothermal veins occurred as the crustal section migrated across the floor of the rift valley over a period of ~500,000 yr. The late-stage, low-temperature veins were deposited as the section migrated out of the rift valley and into the transverse ridge along the margin of the fracture zone.

Chemical composition of tephra from the Greenland-Iceland-Norwegian-Sea

Explosive ocean island volcanism in the Greenland-Iceland-Norwegian Sea (GIN Sea) is indicated by marine tephra layers at 10-300 ka. Peaks of explosive volcanism occurred in oxygen isotope stages 8, 7, 5 and 1. The depositional age of the tephra was estimated using the oxygen isotope stratigraphy and dating of marine records. Geochemical analyses of the tephra layers show that all originate from Iceland. Here we report the characteristics of tephra from these major Icelandic events in 30 deep-sea cores from the GIN Sea. Our findings provide constraints on the distribution of tephra from the eruption source. For the Vedde Ash (oxygen isotope stage 1) we estimate a minimum fallout area of 2*10**5 km**2, stretching from central Greenland in the west and southern Sweden in the east, to 71°N in the GIN Sea. The magnitude of the eruption and the regional wind conditions controlled the extent and concentrations of these ash fallout events. Oceanic circulation and differential settling may have affected the distribution and final deposition of ash particles such as bubble wall shards.

On the microstructure, growth pattern and original porosity of belemnite rostra: insights from calcitic Jurassic belemnites

Calcitic belemnite rostra are usually employed to perform paleoenvironmental studies based on geochemical data. However, several questions, such as their original porosity and microstructure, remain open, despite they are essential to make accurate interpretations based on geochemical analyses.This paper revisits and enlightens some of these questions. Petrographic data demonstrate that calcite crystals of the rostrum solidum of belemnites grow from spherulites that successively develop along the apical line, resulting in a “regular spherulithic prismatic” microstructure. Radially arranged calcite crystals emerge and diverge from the spherulites: towards the apex, crystals grow until a new spherulite is formed; towards the external walls of the rostrum, the crystals become progressively bigger and prismatic. Adjacent crystals slightly vary in their c-axis orientation, resulting in undulose extinction. Concentric growth layering develops at different scales and is superimposed and traversed by a radial pattern, which results in the micro-fibrous texture that is observed in the calcite crystals in the rostra.Petrographic data demonstrate that single calcite crystals in the rostra have a composite nature, which strongly suggests that the belemnite rostra were originally porous. Single crystals consistently comprise two distinct zones or sectors in optical continuity: 1) the inner zone is fluorescent, has relatively low optical relief under transmitted light (TL) microscopy, a dark-grey color under backscatter electron microscopy (BSEM), a commonly triangular shape, a “patchy” appearance and relatively high Mg and Na contents; 2) the outer sector is non-fluorescent, has relatively high optical relief under TL, a light-grey color under BSEM and low Mg and Na contents. The inner and fluorescent sectors are interpreted to have formed first as a product of biologically controlled mineralization during belemnite skeletal growth and the non-fluorescent outer sectors as overgrowths of the former, filling the intra- and inter-crystalline porosity. This question has important implications for making paleoenvironmental and/or paleoclimatic interpretations based on geochemical analyses of belemnite rostra.Finally, the petrographic features of composite calcite crystals in the rostra also suggest the non-classical crystallization of belemnite rostra, as previously suggested by other authors.

Study of mural paintings by Fulvio Pennacchi in São Paulo City by mineralogical techniques

The present research deals with two mural paintings made in 1947 with the fresco technique by Fulvio Pennacchi in the Catholic Chapel of the Hospital das Clínicas (São Paulo City, Brazil), namely the Virgin Annunciation and the Supper at Emmaus. This study regards the materials and painting techniques used by the artist, based on historical research,on in situ observations and laboratory analytical techniques (stereomicroscopy,scanning electron microscopy with an energy dispersive spectrometer, X-ray diffractometry, electron microprobe, images obtained with UV-light), aiming to improve the methods of characterization of objects of our cultural heritage, and to enhance its preservation accordingly. The results lead to the identification of the plaster components and of distinct layers in the frescoes, besides further information on grain size, impurities and textures, composition of pigments, and features of deterioration, such as efflorescences. The degree of degradation of the murals painting was assessed by this way. Our data suggest that a single layer of plaster was used by Pennacchi, as a common mortar with fine- and medium-grained aggregates. Differences in texture were obtained by adding gypsum to the plaster.

Nd:YAG Laser Improves Biocompatibility of Human Dental Root Surfaces

Objective: Our goal was to compare the in vivo biocompatibility of dental root surfaces submitted to four different treatments after tooth avulsion followed by implantation into rat subcutaneous tissue. Background Data: Dental root surface preparation prior to replanting teeth remains a challenge for endodontists. Root surface changes made by Nd:YAG irradiation could be an alternative preparation. Methods: Forty-eight freshly extracted human dental roots were randomly divided into four treatment groups prior to implantation into rat subcutaneous tissue: G1, dry root, left in the environment up to 3 h; G2, the same treatment as G1, followed by a soaking treatment in a 2.4% sodium fluoride solution (pH 5.5); G3, root soaked in physiologic saline after avulsion for 72 h; G4, the same treatment as G1, followed by Nd:YAG laser irradiation (2.0 W, 20 Hz, 100 mJ, and 124.34 J/cm(2)). The animals were sacrificed 1, 7, and 45 d later. Histological and scanning electron microscopy analyses were done. Results: All dental roots were involved and in intimate contact with connective tissue capsules of variable thicknesses. Differences were observed in the degree of inflammation and in connective tissue maturation. In G3 the inflammatory infiltrate was maintained for 45 d, whereas the Nd:YAG laser irradiation (G4) led to milder responses. The overall aspects of the root surfaces were similar, except by the irradiated roots, where fusion and resolidification of the root surface covering the dentinal tubules were observed. Conclusion: Nd:YAG laser irradiation improves the biocompatibility of dental root and thus could be an alternative treatment of dental root prior to replantation.

Fruit anatomy of Neotropical species of Indigofera (Leguminosae, Papilionoideae) with functional and taxonomic implications

LEITE, V. G., F. S. MARQUIAFAVEL, D. P. MORAES, AND S. P. TEIXEIRA (Departamento de Ciencias Farmaceuticas, Faculdade de Ciencias Farmaceuticas de Ribeirao Preto, Universidade de Sao Paulo (USP), Av. do Cafe, s/n, 14040-903 Ribeirao Preto, SP, Brazil). Fruit anatomy of Neotropical species of Indigofera (Leguminosae, Papilionoideae) with functional and taxonomic implications. J. Torrey Bot. Soc. 136: 203-211. 2009-This work reports on the fruit surface and anatomy of seven Neotropical species of Indigofera (I. campestris Bong. ex Benth., I. hirsuta L., I. lespedeziodes Kunth, I. microcarpa Desv., I. spicata Forssk., I. suffruticosa Mill., and I. truxillensis Kunth) to help species diagnosis and clarify the fruit type classification. Flowers and fruits at several stages of development were removed from living material, fixed, and examined with scanning electron (surface analyses) and light microscopies (histological analyses). Species showed differences in relation to the number of exocarp layers, secretory trichome morphology and distribution, presence of stomata, phenolic idioblast size and distribution in mesocarp, the number and arrangement of endocarp fibers, and the presence of it separation tissue. It is noteworthy that no separation tissue was observed in L microcarpa and I. suffruticosa, although they have dehiscent fruits, which indicates it delayed dehiscence. The present work confirms that fruit anatomical characters can be utilized as it tool for fruit type classification, especially in Indigofera, the third largest genus of Leguminosae.

Process mineralogy of fluorosilicate minerals in OK Tedi ores

The impact of fluorine in copper flotation was relatively unknown until the introduction of skarn ores in the Ok Tedi concentrator. Fluorine in the copper concentrates reports to the gas phase during the smelting stage and forms a corrosive H2SO4-HCl-HF acid brine mixture which must be neutralised. This work was aimed at studying the mineralogy of the fluorosilicate minerals contained in the various oretypes present in the Ok Tedi porphyry copper deposit. The electron microprobe was used to analyse for fluorine and hence identify the fluorosilicate minerals in each oretype. This study revealed talc, phlogopite, biotite, clays, amphiboles, fluoroapatite and titanite to be the sources of fluorine in the orebody. Laboratory and plant investigations were conducted to study the flotation response of these minerals. Chemical assaying of the products of these tests was done to determine the bulk assay of fluorine, Using Rietveld analysis, quantitative estimates of the fluorosilicate minerals in these products were generated. Marrying of the bulk assay with the respective mineralogical assay enabled the understanding of the flotation behavior of fluorine and it's associated mineralogy. Talc and phlogopite were found to be the causes of the fluorine problem at Ok Tedi. (C) 2001 Elsevier Science Ltd. All rights reserved.

Cenozoic continental weathering and its implications for the palaeoclimate: evidence from Ar-40/Ar-39 geochronology of supergene K-Mn oxides in Mt Tabor, central Queensland, Australia

One hundred and twenty-five mineral grains from 45 visually pure K-bearing Mn oxide (hollandite group) samples collected from weathering profiles in the Mt Tabor region of central Queensland, Australia, were analysed by the Ar-40/Ar-39 laser probe technique. These K-Mn oxides precipitated mainly through a process of cavity filling (direct precipitation from weathering solution), with botryoidal texture formed by micrometric mineral bands. Well-defined and reproducible plateau ages have been obtained for most samples, ranging from 27.2 +/- 0.8 to 6.8 +/- 0.5 Ma (2 sigma). Statistical analysis of the geochronological results by mixture modelling suggests an episodic mineral precipitation history, with two major peaks at 20.2 +/- 0.22 Ma and 16.5 +/- 0.17 Ma. The geochronological results, when combined with information on paragenetic relationships and mineralogical textures obtained from petrographic, scanning electron microscopy, and electron microprobe investigations, indicate that warm and humid palaeoclimatic conditions favourable to intense chemical weathering prevailed in central Queensland from late Oligocene to middle Miocene, particularly in the early Miocene. These results, in conjunction with previous and ongoing investigations in NW and eastern Queensland, suggest that most of Queensland was dominated by humid climates during the Miocene. (C) 2002 Elsevier Science BN. All rights reserved.

Identification of the enamelin (g.8344delG) mutation in a new kindred and presentation of a standardized ENAM nomenclature

The amelogenesis imperfectas (Al) area geneticatly heterogeneous group of diseases that result in defective development of tooth enamel. Although X-linked, autosomal. dominant and autosomal. recessive forms of Al have been clinically characterized, only two genes (AMELX and ENAM) have been associated with Al. To date, three enamelin (ENAM) mutations have been identified. These mutations cause phenotypically diverse forms of autosomal. dominant Al. Detailed phenotype-genotype correlations have not been performed for autosomal. dominant Al due to ENAM mutations. We identified a previously unreported kindred segregating for the ENAM mutation, g.8344delG. Light and electron microscopy analyses of unerupted permanent teeth show the enamel is markedly reduced in thickness, Lacks a prismatic structure and has a laminated appearance. Taken together these histological features support the enamelin protein as being critical for the development of a normal. enamel. thickness and that it Likely has a role in regulating c-axis crystallite growth. Because there is growing molecular and phenotypic diversity in the enamelin defects, it is critical to have a nomenclature and numbering system for characterizing these conditions. We present a standardized nomenclature for ENAM mutations that will allow consistent reporting and communication. (C) 2003 Elsevier Science Ltd. All rights reserved.

Índice de distorção, parâmetros celulares e composição química de cordierite de granitóides e corneanas da região de Tondela - Oliveira do Hospital (Portugal Central)

Memórias e Noticias, PubI. Mus. Lab. Mineral. Geol., Univ. Coimbra, n.O 116, 1993