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We report a new occurrence of the rare mineral wiluite, the B-rich equivalent of vesuvianite, from Ariccia, Alban Hills volcano, Rome, Italy. The specimen studied was found in the collection of the Museum of Mineralogy of the University of Rome (label MMUR22496/482). Wiluite from Ariccia was sampled at the Parco Chigi quarry, within the phreatomagmatic unit emitted by the Albano maar known locally as “Peperino di Marino”. It occurs as dark brown to black euhedral, well-formed prismatic crystals, up to 1.0 cm in length and 0.5 cm across. Optical observations show a weak pleochroism and an imperfect extinction. The mineral is uniaxial (+) with ω 1.722(2) and ε 1.727(2). It is tetragonal P4/nnc, a 15.716(2), c 11.704(2) Å, V 2890.8(7) Å3. The crystal-chemical formula, obtained by combining EMP, SIMS and XREF data and calculated on the basis of 18 Si atoms, is: X(Ca18.72Mg0.15Sr0.02La0.05Ce0.04Nd0.01)Y(1)(Fe3+0.36Mg0.26Ti0.27Mn0.11)Y(2)Al3.67Fe3+0.19Mg0.14) Y(3)(Al3.29Fe3+1.36Mg3.35)T(1)B2.18Al0.02Be0.02H0.47[]1.31)T(2)(B0.68H0.32)ZSi18O68O(11)(F1.21O6.79)[O(10)+O(12)]O2.68. The micro OH-stretching FTIR spectrum consists of a defi ned triplet of broad bands at 3639, 3573 and 3488 cm–1, respectively, and a very broad, composite absorption at 3300 cm–1. All bands are strongly polarized, with maximum absorption for E // c and minimum absorption for E normal c. The integrated molar absorption coeffi cient for wiluite is εi = 90.000 ± 1500 l mol–1 cm–2. In the 1600–1100 cm–1 region, absorptions due to both [3]B–O and [4]B–O bonds are observed. The Mg and Al K-edge X-ray-absorption spectra are consistent with the presence of two octahedral coordination sites for both atoms, as determined by XREF, with the addition of a third, highly unusual, five-fold pyramidal site for the divalent cation.

The topotactic oxidation and delithiation reaction from triphylite, Li(Fe,Mn)PO4, leading to ferrisicklerite, Li

We obtained areal variations of crustal thickness, magnetic intensity, and degree of melting of the sub-axial upwelling mantle at Thetis and Nereus Deeps, the two northernmost axial segments of initial oceanic crustal accretion in the Red Sea, where Arabia is separating from Africa. The initial emplacement of oceanic crust occurred at South Thetis and Central Nereus roughly similar to 2.2 and similar to 2 Ma, respectively, and is taking place today in the northern Thetis and southern Nereus tips. Basaltic glasses major and trace element composition suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/or potential temperature between Thetis and Nereus. Eruption rate, spreading rate, magnetic intensity, crustal thickness and degree of mantle melting were highest at both Thetis and Nereus in the very initial phases of oceanic crust accretion, immediately after continental breakup, probably due to fast mantle upwelling enhanced by an initially strong horizontal thermal gradient. This is consistent with a rift model where the lower continental lithosphere has been replaced by upwelling asthenosphere before continental rupturing, implying depth-dependent extension due to decoupling between the upper and lower lithosphere with mantle-lithosphere-necking breakup before crustal-necking breakup. Independent along-axis centers of upwelling form at the rifting stage just before oceanic crust accretion, with buoyancy-driven convection within a hot, low viscosity asthenosphere. Each initial axial cell taps a different asthenospheric source and serves as nucleus for axial propagation of oceanic accretion, resulting in linear segments of spreading.

The presence in the Earth's mantle of even small amounts of water and other volatiles has major effects: first, it lowers drastically mantle's viscosity, thereby facilitating convection and plate tectonics; second, it lowers the melting temperature of the rising mantle affecting the formation of the oceanic crust. H2O concentration in oceanic basalts stays below 0.2 wt% except for basalts sampled near "hot spots" that contain significantly more H2O than normal MORB, implying that their mantle plume sources are unusually H2O-rich. Basalts sampled in the Equatorial Atlantic close to the Romanche transform, a thermal minimum in the Ridge system, have a H2O content that increases as the ridge is cooled approaching the transform offset. These basalts are Na-rich, being generated by low degrees of melting of the mantle, and contain unusually high ratios of light versus heavy rare earth elements implying the presence of garnet in the melting region. H2O enrichment is due not to an unusually H2O-rich mantle source, but to a low extent of melting of the upwelling mantle, confined to a deep wet melting region. Numerical models predict that this wet melting process takes place mostly in the mantle zone of stability of garnet. This prediction is verified by the geochemistry of our basalts showing that garnet must indeed have been present in their mantle source. Thus, oceanic basalts are H2O-rich not only near "hot spots", but also at "cold spots".

Lithium plays an essential geochemical role in granitic pegmatites, and this element can be used to monitor the degree of pegmatite differentiation (Ginzbourg 1960). Among primary phosphates, Li mainly occurs in minerals of the triphylite-lithiophilite [LiFe(PO4)-LiMn(PO4)] and amblygonitemontebrazite [LiAl(PO4)F-LiAl(PO4) OH] series. Starting from the triphylitelithiophilite series, a mechanism of oxidation coupled with Li-leaching is frequently observed, leading to the formation of ferrisicklerite-sicklerite [Li1- x(Fe3+,Mn2+)PO4-Li1-x(Mn2+,Fe3+)PO4] and of heterosite-purpurite [Fe3+(PO4)- Mn3+(PO4)] (Quensel 1957, Mason 1941). In order to constrain the conditions of temperature and oxygen fugacity which occurred in pegmatites, we decided to reproduce experimentally several associations of pegmatite phosphates. Primary alluaudite + triphylite assemblages were reported in the Hagendorf-Süd (Germany), Buranga, and Kibingo (Rwanda) pegmatites, and the hydrothermal experiments (P = 1 kbar, T = 400-800°C) lead to the crystallisation of alluaudite + triphylite at 400 and 500°C, and of alluaudite + triphylite + maricite at 600 and 700°C (Hatert et al. 2005). Triphylite and sarcopside, which show lamellar exsolution textures in several pegmatites, were reproduced between 400 and 700°C (P = 1 kbar), starting from the compositions LiFe2.5(PO4)2, LiFe2Mn0.5(PO4)2, and LiFe1.5Mn(PO4)2 (Hatert et al. 2007). The aim of this study is to measure the Li-content of several natural and synthetic phosphates by SIMS, in order to shed some light on the crystal chemistry of lithium in pegmatite phosphates.

The light lithophile (Li, Be and B) and halogen (F, Cl) elements are powerful tracers of fluid transfer, due to their mobility during high temperature hydrothermal processes and metamorphic devolatilization, as documented by their very high concentrations detected in altered oceanic rocks -as a result of interactions with hydrothermal fluids- relative to their low contents in mantle reservoirs. Moreover, although a great deal of studies have been carried out on Li, Be, B, F (and Cl) in whole rock and rock-forming minerals of altered rocks from divergent and convergent plate margins, an inventory of such trace elements in mineral phases from altered Icelandic oceanic crust is still incomplete and requires thorough constraints and detailed monitoring. A micro-analytical study of light and volatile elements in single mineral phases is of importance when studying the Reykjanes geothermal system in SW Iceland, collaborating in the Iceland Deep Drilling Project (IDDP) drilling. Here we report the results of in-situ EMPA and SIMS investigations on 10 basaltic rock samples of altered magmatic (plagioclase and clinopyroxene) and hydrothermal phases (amphibole and epidote). The samples are from drill cuttings at different depths, ranging from 400-3000 m from the well RN-17. To authors' knowledge, this data on light and volatile elements, i.e., Li, Be, B and F is the first in the literature on single mineral phases from the Reykjanes system, and complete our research on light elements begun two years ago on this geothermal field. Our study benefited from the use of detailed optical and SEM investigations; from ICP-MS on Li, and ID analysis on B on the whole rock; from TIMS on B isotope ratios. The analytical result and its significance will be described at the EMAS 2009 workshop.

A >300 km long lithospheric section (Vema Lithospheric Section or VLS) is exposed south of the Vema transform at 11 degrees N in the Atlantic. It is oriented along a seafloor spreading flow line and represents similar to 26 Ma of accretion at a single 80 km long segment (EMAR) of the Mid-Atlantic Ridge. The basal part of the VLS exposes a mantle unit made mostly of relatively undeformed coarse-grained/porphyroclastic peridotites that were sampled at close intervals. Strongly deformed mylonitic peridotites were found at 14 contiguous sites within a similar to 80 km stretch (similar to 4.7 Ma interval); they are dominant in a time interval of 1.4 Ma, from crustal ages of 16.8 to 18.2 Ma (mylonitic stretch). Some of the mylonites are "dry," showing anhydrous high-T deformation, but most contain amphibole. The mylonitic peridotites tend to be less depleted than the porphyroclastic peridotites on the basis of mineral major and trace elements composition, suggesting that the mylonites parent was a subridge mantle that underwent a relatively low degree of melting. The Sr, Nd, and O isotopic composition of the amphiboles is MORB-like and suggests either that seawater did not contribute to their isotopic signature or that their isotopic ratios re-equilibrated during fluid circulation in the upper mantle. Four (40)Ar/(39)Ar ages, on three amphiboles separated from the peridotites, are close to crustal ages predicted from magnetic anomalies, confirming that the amphiboles formed close to ridge axis. We propose that crustal accretion at the EMAR segment has been mostly symmetrical for the 26 Ma of its recorded history, except for the similar to 1.4 Ma interval of prevalent ultramafic mylonites (mylonitic stretch) that may record a period of quasi-amagmatic asymmetric accretion of oceanic lithosphere close to the ridge-Vema transform intersection, possibly with development of detachment faults. This interval may correspond to a thermal minimum of the subridge upwelling mantle, marking the transition from a period of decreasing to one of increasing mantle melting below the EMAR segment.

A >300 km long lithospheric section (Vema Lithospheric Section or VLS) is exposed south of the Vema transform at 11 degrees N in the Atlantic. It is oriented along a seafloor spreading flow line and represents similar to 26 Ma of accretion at a single 80 km long segment (EMAR) of the Mid-Atlantic Ridge. The basal part of the VLS exposes a mantle unit made mostly of relatively undeformed coarse-grained/porphyroclastic peridotites that were sampled at close intervals. Strongly deformed mylonitic peridotites were found at 14 contiguous sites within a similar to 80 km stretch (similar to 4.7 Ma interval); they are dominant in a time interval of 1.4 Ma, from crustal ages of 16.8 to 18.2 Ma (mylonitic stretch). Some of the mylonites are "dry," showing anhydrous high-T deformation, but most contain amphibole. The mylonitic peridotites tend to be less depleted than the porphyroclastic peridotites on the basis of mineral major and trace elements composition, suggesting that the mylonites parent was a subridge mantle that underwent a relatively low degree of melting. The Sr, Nd, and O isotopic composition of the amphiboles is MORB-like and suggests either that seawater did not contribute to their isotopic signature or that their isotopic ratios re-equilibrated during fluid circulation in the upper mantle. Four Ar-40/Ar-39 ages, on three amphiboles separated from the peridotites, are close to crustal ages predicted from magnetic anomalies, confirming that the amphiboles formed close to ridge axis. We propose that crustal accretion at the EMAR segment has been mostly symmetrical for the 26 Ma of its recorded history, except for the similar to 1.4 Ma interval of prevalent ultramafic mylonites (mylonitic stretch) that may record a period of quasi-amagmatic asymmetric accretion of oceanic lithosphere close to the ridge-Vema transform intersection, possibly with development of detachment faults. This interval may correspond to a thermal minimum of the subridge upwelling mantle, marking the transition from a period of decreasing to one of increasing mantle melting below the EMAR segment.

In spite of the importance of chlorine as a geochemical tracer, Cl data on mantle rocks are nowadays rather scarce mainly due to analytical difficulties. Techniques involving sample dissolution and/or fusion as well as non-destructive bulk techniques have been used for Cl determination in silicates, but they need rather high amount of material, which, in most cases, hampers the investigation of single minerals. Electron microprobe is generally employed to measure Cl contents on the level of several hundreds of ppm, whereas lower Cl concentrations (few tens ppm) are not routine for EMPA. The SIMS technique that affords for low detection limits over a large mass range and a good spatial resolution represents a powerful tool to address some of the main questions still open about Cl behaviour in the Earth mantle. In this work we report and discuss the SIMS data for Cl obtained on upper-mantle peridotites and xenoliths affected by various metasomatic processes as a result of the ion exchange between minerals and solid rocks, and migrating fluid phases. The samples here investigated are represented by peridotites BM90-6 (Balmuccia, Western Alps, Italy) and LH12 (Lherz, Eastern Pyrénées, France); pre-rift peridotite Z2070 (Zabargad Island, Red Sea); xenoliths from alkaline lavas Z7 and RP68 (Massif Central, France). An improvement in our analytical procedure at the ion microprobe (Cameca IMS 4f) at CNR-IGG (Pavia) allowed for the quantification of very low amounts of Cl (down to few ppm by weight). It allowed also for the measurement of other relevant trace elements at the same spot during the analytical run. Our experimental set up included a 16O- primary beam (? 15-?m Ø) and energy-filtered secondary-ions that were monitored in positive mode at low mass resolving power (M/?M = 600). We derived some interesting information about the Cl distribution inter- and intra-mineral silicate phases: olivine, orthopyroxene, clinopyroxene and amphibole (when present), and studied the correlation between chlorine and other important geochemical tracers, i.e., boron and lithium. The in-situ analysis of Cl by SIMS in mineral phases resulted to have the potential for opening a new window on what "upper-mantle metasomatism" really means.

Iceland is one of the few places on earth where it is possible to see an active spreading ridge above the sea level with the two plates moving apart. This country lies in fact over both a plume hot material, up-welling from great depths, and the Mid-Atlantic Ridge, at the boundary between the North American and Eurasian tectonic plates where new oceanic crust is being created. The continued volcanic activity associated to this geologically complex area has produced a lot of high-temperature geothermal systems. Inside these geothermal fields, the hydrothermal alteration of basaltic rocks is very effective. In the frame of the international Iceland Deep Drilling Project (IDDP) we have carried out in-situ (EMP+SIMS) analyses on both magmatic (plagioclase and clinopyroxene) and hydrothermal (amphibole and epidote) phases in 11 drill-cutting samples, selected on the basis of different depths (400-3000 m) from the well RN-17, which is from within the Reykjanes geothermal fields in SW Iceland. The present study has been focused on determining the concentrations of some of so-called hydrothermal markers, such as the light lithophile (Li, B) and halogen (Cl) elements that were investigated by SIMS with a Cameca IMS 4f ion microprobe installed at CNR-IGG (Pavia). In addition, the Sr isotope ratio (87Sr/86Sr), determined at CNR-IGG (Pisa) by Thermal Ionization Mass Spectrometry (TIMS) with a Finnigan Mat 262 was utilized as a further hydrothermal marker. The selected samples were shown to be affected by a significant compositional inhomogeneity of the mineral assemblage at a few-micron scale (both laterally and in-depth). Nevertheless, the application of sensitive, high-resolution techniques, such as those used here, has allowed us to face the study of the geochemical composition (major, minor and trace constituents) in complex, altered matrixes, and arrive at conclusions on the hydrothermal alteration degree in a region which is of great scientific and economic interest.

Olivine + clinopyroxene ± amphibole cumulates have been widely documented in island arc settings and may constitute a significant portion of the lowermost arc crust. Because of the low melting temperature of amphibole (~1100°C), such cumulates could melt during intrusion of primary mantle magmas. We have experimentally (piston-cylinder, 0·5-1·0 GPa, 1200-1350°C, Pt-graphite capsules) investigated the melting behaviour of a model amphibole-olivine-clinopyroxene rock, to assess the possible role of such cumulates in island arc magma genesis. Initial melts are controlled by pargasitic amphibole breakdown, are strongly nepheline-normative and are Al2O3-rich. With increasing melt fraction (T > 1190°C at 1·0 GPa), the melts become ultra-calcic while remaining strongly nepheline-normative, and are saturated with olivine and clinopyroxene. The experimental melts have strong compositional similarities to natural nepheline-normative ultra-calcic melt inclusions and lavas exclusively found in arc settings. The experimentally derived phase relations show that such natural melt compositions originate by melting according to the reaction amphibole + clinopyroxene = melt + olivine in the arc crust. Pargasitic amphibole is the key phase in this process, as it lowers melting temperatures and imposes the nepheline-normative signature. Ultra-calcic nepheline-normative melt inclusions are tracers of magma-rock interaction (assimilative recycling) in the arc crust.

Piergorite-(Ce) is a new mineral found at Tre Croci, Vetralla, Italy with simplified formula Ca8Ce2 (Al0.5Fe0.53+)(Sigma 1)(square,Li,Be)(2)Si6B8O36(OH,F)(2). It occurs as strong intergrowths of small crystals, colorless to pale yellow, associated with sanidine, mica, magnetite, rutile, titanite, and other Th-U-REE bearing minerals, in miarolitic cavities of a syenitic ejectum. Piergorite-(Ce) is biaxial negative, n(alpha) = 1.717 (1), n(beta) = 1.728 (1), and n(gamma) = 1.735 (1), 2V(meas) = 68(2)degrees, X = b, and Z (boolean AND) c = 7(1)degrees. Crystals show tabular habit and a very good {010} cleavage; twinning along the (30 (1) over bar) plane produces "L" forms. The three strongest lines in the simulated powder diffraction pattern (d(obs), I, hkl) are: 2.65 angstrom, 100.0, (213, (4) over bar 13); 1.91 angstrom, 48.3, (223, (4) over bar 23, 821); 2.90 angstrom, 44.9, ((6) over bar 03, (6) over bar 12). The structure was solved by Patterson synthesis from X-ray diffraction data [monoclinic, space group P2/a, a = 28.097(3) angstrom, b = 4.777(1) angstrom, c = 10.236(2) angstrom, beta = 96.81 (1)degrees, V = 1364.2(7) angstrom(3), Z = 2] and was refined to a final R-obs = 0.059 for 6480 Fo with I-o > 3 sigma(I-o). The structure shows similarities with the hellandite group because Si and B tetrahedra form chains along c. Hellandite structure is characterized by a single chain of five-membered rings, whereas piergorite-(Ce) shows a double chain of five-membered rings interconnected by a single octahedral site to form a three-dimensional framework containing five independent eightfold-coordinated M sites and a partly occupied T-cavity.

Sazhinite-(La) is a new mineral from the Aris phonolite, Windhoek, Namibia. It occurs in vesicles within the phonolite, together with other species crystallized from late-stage hydrothermal fluids: natrolite, aegirine, microcline, apophyllite, sphalerite, analcime, fluorite, villiaumite, hydroxylapatite, galena, makatite, quartz, eudialyte, kanemite, tuperssuatsiaite and korobitsynite. Sazhinite-(La) forms small euhedral crystals up to 1 mm long and 0.4 mm wide, elongated along [001] and flattened on (010), exhibiting the forms {h0l}, {100} and {001}. It has good cleavage parallel to {010} and {001}. Twinning was not observed. Crystals are brittle with a Molts hardness of 3, creamy white with a white streak, vitreous to pearly lustre, and translucent to transparent. In plane-polarized light, crystals are colourless with a = Z, b = Y, c = X. It is biaxial positive with alpha = 1.524, beta = 1.528, gamma = 1.544, all +/- 0.002, 2V(Z)(obs) = 46(1)degrees, and 2V(Z)(calc.) = 53.6 degrees. Sazhinite-(La) is orthorhombic Pmm2, a = 7.415(2), b = 15.515(3), c = 7.164(1) angstrom, and V = 824.2 angstrom(3). One crystal was studied by X-ray diffraction, electron microprobe and secondary ion mass spectrometry (SIMS) microanalysis, leading to the average composition (Na2.87K0.02Sr0.01)(Sigma 2.90) [La0.41Ce0.35Pr0.02Nd0.04(Sm,Gd,Dy,Er,Yb)(Sigma 0.01),Th0.09U0.01Y0.01Zr0.01Ca0.08Li0.01](Sigma 1.04)(T)(Si5.87S0.06B0.01) (O14.86F0.14)(.)(H2O)(2). Weighted full-matrix least-squares refinement on 3369 reflections yielded R-all = 3.8%. The structure is built of corrugated [Si6O15](6-) layers linked by [7]-coordinated REE and R4+ cations. This framework leaves channels that contain three [5]- and [6]-coordinated Na cations per formula unit that compensate for the residual charge on the silicate layers. The SIMS analyses confirm a Na content of 3 atoms per formula unit, leading to an ideal formula of Na3LaSi6O15(H2O)(2). The third Na atom is bonded to H2O groups and therefore the total content of both Na and H2O may be reduced to 2 and 1 per formula, respectively. The depletion in Na allows for the entrance of high-charge cations such as Th4+.

Dellaventuraite is a new amphibole species from the Kajlidongri manganese mine, Jhabua District, Madhya Pradesh, India. It occurs with leakeite, kornite, albite, braunite, and bixbyite associated with cross-cutting epigenetic veins that have reacted with regionally metamorphosed rocks containing Mn-rich minerals (braunite, bixbyite, jacobsite, spessartine) to produce Mn-rich amphiboles, Mn-rich pyroxenes, Mn-rich mica, piemontite, and manganophyllite. Dellaventuraite occurs as anhedral grains, the color of which varies from pink to red, depending on Mn content. It is brittle, H = 5, D-calc = 3.184 g/cm(3), has a pale pink streak, vitreous luster, and does not fluoresce in ultraviolet light; it has perfect cleavage on {110} and conchoidal fracture. In transmitted plane-polarized light, dellaventuraite is strongly pleochroic X = pale mauve-brown, Y similar to Z = dark red-brown; Y a = 20degrees (in beta obtuse), Z = b, with absorption X < Y similar to Z. It is biaxial positive, eta(alpha) = 1.688 +/- 0.0003, eta(beta) = 1.692 +/- 0.005, eta(gamma) = 1.721 +/- 0.003, 2V((obs)) = 49 +/- 3degrees, 2V((calc)) = 41degrees. Dellaventuraite is monoclinic, space group C2/m, a = 9.808(1), b = 17.840(2), c = 5.2848(5) Angstrom, gamma = 104.653(1)degrees, V = 894.6(2) Angstrom(3), Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [d(l,hkl)]: 2.697(10,151), 2.542(9,-202), 3.127(8,310), 3.378(7,131),2.154(7,261),1.434 (7,-661),4.450(6,021), 8.459(5,110), 2.727(5,-331),2.328(5,-351). Analysis by a combination of electron microprobe, SIMS and crystal-structure refinement gives SiO2 = 54.22, Al2O3 = 0.81, TiO2 = 5.45, Fe2O3 = 6.44, Mn2O3 = 7.57, ZnO = 0.12, NiO = 0.16, MgO = 8.26, Li2O = 1.53, CaO = 1.85, Na2O = 8.12, K2O = 2.12, H2O = 0.80, Cr, V, F, Cl not detected, sum 97.41 wt%. The formula unit, calculated on the basis of 24(O,OH,F) is (K0.40Na0.61)(Na1.71Ca0.29) (Mg1.81Zn0.01Ni0.002Li0.90Fe0.713+Mn0.853+Ti0.604+Al0.10)(Si7.96Al0.04)O-22[(OH0.80 O-1.20]; the ideal end-member compostion NaNa2(MgMn23+LiTi4+)Si8O22O2. The crystal structure of dellaventuraite was refined to an R index of 3.8% using MoKalpha. X-ray intensity data. The M1 site is occupied by Ti4+, Mn3+, and Mg in approximately equal amounts, the M2 site is occupied primarily by Mg and Fe3+, and M3 is occupied by Li with minor Mg and Mn2+. Local bond-valence considerations suggest that O2- at O3 is linked to Ti4+Mg or Mn3+Mn3+ at the adjacent M I sites, and that OH at O3 is linked to MgMg at the adjacent M1 sites.