Kuniaki Makino

Cl incorporation into successively zoned amphiboles from the Ramnes cauldron, Norway

Abstract Amphibole from alkali granites in the Ramnes cauldron in the Oslo rift was altered hydrothermally by corrosion and growth through multiple events of fluid circulation. The alteration developed successive zones of amphibole at the crystal margins, resulting in a (1) brownish ferro-edenitic hornblende core (FE), (2) deep bluish-green hastingsitic hornblende zone (HH), and (3) light-greenish Fe-rich actinolite rim (FA). The edenitic core preserves the original igneous amphibole composition. The Cl content of amphibole strongly increases from the FE (0.78-0.82 wt%) to the HH zone (2.07-2.96 wt%) and abruptly decreases in the FA rim (0.01-0.36 wt%). In the Cl-rich HH amphibole zone, amphibole has characteristically high Cl content [2.96 wt%, 0.82 atoms per formula unit (apfu)] and high concentrations in both [4]Al (1.73 apfu) and A-site occupancy (0.86 apfu) with a large K/(Na + K) value of 0.47. Both [4]Al and A-site occupancy increase systematically with positive correlation with Cl content throughout the three amphibole zones. On the other hand, Fe2+ content is not so simply correlated to the Cl content. Based on crystal structure considerations on Cl-rich amphiboles, the cation substitutions are illustrated by structural (geometrical) constraints for [4]Al and by a chemical constraint for Fe2+. These contributions for Cl incorporation are expressed empirically by ln(Cl/OH)amp = ln(Cl/OH)fluid + A·[4]Al·Fe2+/RT + B/RT, where A and B are constant. [4]Al·Fe2+ vs. ln(Cl/OH) plots of the three distinct amphibole zones suggest different fluid conditions in chemistry and temperature for the three zones. The zoning was developed through two stages of hydrothermal alteration. In the early hydrothermal event, a saline and high-temperature fluid altered the original hornblende (FE) to the Cl-rich HH zone. Late stage alteration by a high Fe/Cl and relatively low-temperature fluid partially over-printed the FA zone at the crystal margin.

Successive zoning of Al and H in hydrothermal vein quartz

Abstract Electron microprobe and micro-FTIR (mFTIR) analyses of a quartz crystal from a hydrothermal vein reveal zoning in Al and H concentrations. The Al concentration ranges from 27 to 468 Al/106Si, and the H concentration ranges correspondingly from 49 to 266 H/106Si. The zoning profile reveals a positive correlation between Al and H concentrations. At low Al concentration (<100 Al/106 Si), the H/Al ratio is ~1.0 and the infrared spectra show strong bands due to Al-OH and very weak bands due to Li-OH. These results indicate that most of the charge imbalance resulting from Al3+ substituting for Si4+ is compensated by H. At an Al concentration >100 Al/106 Si, the ratio of H/Al drops to ~0.5 and the infrared spectra show absorption bands due to both Al-OH and Li-OH species. No other alkali ions were detected by microprobe analysis. These results suggest that a combination of H and Li are providing charge compensation in the more Al-rich zones. Replacement of Si4+ by Al3+ + H+ ± Li+ is the principal mechanism for the incorporation of these trace elements into the quartz structure.

Property analysis of ectopic calcification in the carpal tunnel identification of apatite crystals: a case report

IntroductionA 64-year-old woman presented with symptoms of subacute exacerbation of a year-long carpal tunnel syndrome that was caused by a large calcified mass in the tunnel.ConclusionThe resected mass consisted of very tiny rods, and x-ray diffraction analysis, as well as the component analysis using energy dispersive x-ray microanalysis, revealed the mass to be most compatible with apatite. The back-scattered electron images suggested that precipitation might be a mechanism for development of the calcified mass.

Magnesiosadanagaite, a new member of the amphibole group from Kasuga-mura, Gifu Prefecture, central Japan

Magnesiosadanagaite, ideally NaCa 2 [Mg 3 (A1, Fe 3+ ) 2 ]Si 5 A1 3 O 22 (OH) 2 , is a new member of the amphibole group occurring as rims of zoned amphibole in rock samples from the contact aureole in Kasuga-mura, central Japan. The amphibole is associated with phlogopite, titanite, calcite, pyrrhotite and chalcopyrite, and composed of an [4] A1-poorer core and [4] A1-richer rim. The core and rim are classified into pargasite [ [4] A1 = 1.84–2.19 atoms per formula unit (apfu); for O = 23] and pargasite-magnesiosadanagaite ( [4] A1 = 2.45–2.84 apfu), respectively. Both have relatively high [A] Na (0.67–0.96 apfu) and low K content ( [A] Na (0.70–0.92 apfu) and low K (0.09–0.28 apfu) values of magnesiosadanagaite refute the view that high K substitution at the A site is an essential feature of Si-poor calcic amphiboles. The crystal structure of magnesiosadanagaite was refined for two compositionally different samples. Magnesiosadanagaite has the lowest O(5)-O(6)-O(5) angles (160.4° and 161.8°) ever reported in C 2 m amphiboles, indicating maximal kinking of the double-chain of tetrahedra.

Crystal chemistry of chromian pumpellyite from Osayama, Okayama Prefecture, Japan

Abstract The crystal structure and crystal chemistry of chromian pumpellyite from basic schist in the Osayama ultramafic body, Okayama, Japan, were investigated using electron probe microanalysis (EPMA), Fourier transform infrared spectroscopy (FTIR), and single-crystal X-ray diffraction to determine the distribution of chromium between two independent octahedral sites and structural changes caused by ionic substitutions in pumpellyite, VIIW8VIX4VIY8 IVZ12O56-n(OH)n (Z = 1). Five chromian pumpellyite crystals (ocp1211, ocp0604, ocp1028, ocp1013, and ocp1016) with 0.52, 1.65, 1.26, 1.94, and 1.43 Cr atoms per formula unit (apfu) (EPMA data), respectively, were picked from a hand specimen for X-ray diffraction analysis. The crystal structures (space group C2/m) of ocp1211 [a = 19.1129(6), b = 5.8963(5), c = 8.818(1) Å, β = 97.449(2)°], ocp0604 [a = 19.0935(4), b = 5.900(1), c = 8.810(2) Å, β = 97.540(7)°], ocp1028 [a = 19.105(2), b = 5.9021(6), c = 8.8143(7) Å, β = 97.513(3)°], ocp1013 [a = 19.1558(6), b = 5.9125(9), c = 8.844(1) Å, β = 97.448(4)°], and ocp1016 [a = 19.174(3), b = 5.9194(8), c = 8.830(1) Å, β = 97.497(4)°] were refined using 1058, 829, 1070, 1105, and 1095 unique reflections, and calculations converged at R factors of 4.08, 5.02, 6.32, 6.92, and 7.88%, respectively. The resulting site populations at the X and Y sites are (Mg1.88Al1.51Fe2+0.38 Cr0.16Mn2+0.05Ni0.02)X(Al7.90Ti0.07V0.03)Y for ocp1211, (Mg1.81Al1.53Cr0.42Fe2+0.18Mn2+0.04Ni0.01)X(Al7.34Cr0.65V0.01)Y for ocp0604, (Al1.62Mg1.60Cr0.61Fe2+ 0.13 Mn2+0.03Ni0.01)X(Al7.36Cr0.61V0.03)Y for ocp1028, (Mg1.79Al1.33Cr0.47 Fe2+0.33Mn2+0.08)X(Al6.66Cr1.31V0.03)Y for ocp1013, and (Mg1.94Al1.23Cr0.38Fe2+0.37Mn2+0.08)X(Al6.72Cr1.25V0.03)Y for ocp1016. Cr3+ ions in ocp1211 are distributed only in the X site. The distribution coefficient of Cr and Al between the X and Y sites [(Cr/Al)X/(Cr/Al)Y] is 1.66, 1.79, 3.09, and 4.54 for ocp1016, ocp1013, ocp0604, and ocp1028, respectively, indicating a stronger preference of Cr for the X site than the Y site. The a and b axes increase with increasing Cr content, whereas the c axis is almost constant. The mean Y-O distances increase linearly with increased Cr3+ content in the Y site. However, the mean X-O distances do not depend on the substitution of Cr3+ for Al3+ at the X site. The bond valence sums and the difference-Fourier synthesis indicate that hydroxyl groups are located at the O5, O7, O10, and O11 positions. FTIR spectrum shows main absorption bands at ca. 2911, 3220, 3397, and 3512 cm-1 of OH-stretching vibrations, indicating the presence of OH⋅⋅⋅O hydrogen bonds.

Ti-substitution mechanism in plutonic oxy-kaersutite from the Larvik alkaline complex, Oslo rift, Norway

Abstract Amphibole in the Larvik alkaline plutonic complex in the Oslo rift, Norway, has Ti-rich compositions from edenite through pargasite to kaersutite, and has a large H+ deficiency (0.7-1.1 atoms per formula unit: a.p.f.u.) with a large oxy component in the amphibole OH- site (O2- = 2 - (OH + F + Cl) = 0.2 - 0.9 a.p.f.u.), similar to the mantle-derived kaersutites. Their compositions reveal a characteristically low Fe3+/(Fe3++Fe2+) ratio (<0.23) and a high F concentration (0.3-0.9 a.p.f.u.). Correlation with the Fe3+ ratio caused by Fe2+ + OH- = Fe3+ + O2- + 1/2H2 substitution is negligible, which is supported by H and O isotope compositions. A possible substitution, [6]Al3+ + OH- = [6]Ti4+ + O2- may be operative for Larvik kaersutites when the O2-/Ti is 1.0. A relatively larger O2-/Ti ratio (1.2 - 2.0) suggests an another kaersutite substitution mechanism, [6]R2+ + 2OH- = [6]Ti4+ + 2O2-, where [6]R2+ = Fe2+ + Mg + Mn. These effects might result in the limited O2-/Ti ratio value from 1.0 to 2.0. A negative correlation between Ti and F, suggesting F incorporation into kaersutite may diminish the O2-/Ti ratio, not only due to the occupation of this non-oxy species in the O3 site, but also due to F-Ti avoidance. Composition-dependent H and O isotope variations (δD = -106 to -71‰ and δ18O = 4.6 - 5.2‰) suggest equilibrium in the closed-system magma with differentiation. The mineral chemistry of Larvik oxy-kaersutitic amphibole could reflect the crystallization in a closed-system magma during rifting with passive crustal thinning at the Oslo palaeorift.