The Rhum Layered Complex, Inner Hebrides, Scotland

1987 ◽  
pp. 263-286 ◽  
Author(s):  
C. H. Emeleus
Keyword(s):  
Layered Complex

THE HIGH-TI CAMP FREETOWN LAYERED COMPLEX (SIERRA LEONE) - LITHOSPHERIC IMPRINTING REVEALED BY ISOTOPE SYSTEMATICS

2017 ◽  
Author(s):  
Sara Callegaro ◽  
◽  
Andrea Marzoli ◽  
Hervé Bertrand ◽  
Janne Blichert-Toft ◽  
...  
Keyword(s):  
Sierra Leone ◽  
Isotope Systematics ◽  
Layered Complex

scholarly journals Tamuraite, Ir5Fe10S16, a New Species of Platinum-Group Mineral from the Sisim Placer Zone, Eastern Sayans, Russia

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 545
Author(s):  
Andrei Y. Barkov ◽  
Nadezhda D. Tolstykh ◽  
Robert F. Martin ◽  
Andrew M. McDonald
Keyword(s):  
National Laboratory ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
Cell Parameters ◽  
Reflected Light ◽  
Platinum Group Minerals ◽  
Platinum Group ◽  
Probable Space ◽  
Layered Complex ◽  
Residual Melt

Tamuraite, ideally Ir5Fe10S16, occurs as discrete phases (≤20 μm) in composite inclusions hosted by grains of osmium (≤0.5 mm across) rich in Ir, in association with other platinum-group minerals in the River Ko deposit of the Sisim Placer Zone, southern Krasnoyarskiy Kray, Russia. In droplet-like inclusions, tamuraite is typically intergrown with Rh-rich pentlandite and Ir-bearing members of the laurite–erlichmanite series (up to ~20 mol.% “IrS2”). Tamuraite is gray to brownish gray in reflected light. It is opaque, with a metallic luster. Its bireflectance is very weak to absent. It is nonpleochroic to slightly pleochroic (grayish to light brown tints). It appears to be very weakly anisotropic. The calculated density is 6.30 g·cm−3. The results of six WDS analyses are Ir 29.30 (27.75–30.68), Rh 9.57 (8.46–10.71), Pt 1.85 (1.43–2.10), Ru 0.05 (0.02–0.07), Os 0.06 (0.03–0.13), Fe 13.09 (12.38–13.74), Ni 12.18 (11.78–13.12), Cu 6.30 (6.06–6.56), Co 0.06 (0.04–0.07), S 27.23 (26.14–27.89), for a total of 99.69 wt %. This composition corresponds to (Ir2.87Rh1.75Pt0.18Ru0.01Os0.01)Σ4.82(Fe4.41Ni3.90Cu1.87Co0.02)Σ10.20S15.98, calculated based on a total of 31 atoms per formula unit. The general formula is (Ir,Rh)5(Fe,Ni,Cu)10S16. Results of synchrotron micro-Laue diffraction studies indicate that tamuraite is trigonal. Its probable space group is R–3m (#166), and the unit-cell parameters are a = 7.073(1) Å, c = 34.277(8) Å, V = 1485(1) Å3, and Z = 3. The c:a ratio is 4.8462. The strongest eight peaks in the X-ray diffraction pattern [d in Å(hkl)(I)] are: 3.0106(26)(100), 1.7699(40)(71), 1.7583(2016)(65), 2.7994(205)(56), 2.9963(1010)(50), 5.7740(10)(45), 3.0534(20)(43) and 2.4948(208)(38). The crystal structure is derivative of pentlandite and related to that of oberthürite and torryweiserite. Tamuraite crystallized from a residual melt enriched in S, Fe, Ni, Cu, and Rh; these elements were incompatible in the Os–Ir alloy that nucleated in lode zones of chromitites in the Lysanskiy layered complex, Eastern Sayans, Russia. The name honors Nobumichi Tamura, senior scientist at the Advanced Light Source of the Lawrence Berkeley National Laboratory, Berkeley, California.

Eudialyte-group minerals in rocks of Lovozero layered complex at Mt. Karnasurt and Mt. Kedykvyrpakhk

2015 ◽  
Vol 57 (7) ◽  
pp. 600-613 ◽  
Author(s):  
G. Yu. Ivanyuk ◽  
Ya. A. Pakhomovsky ◽  
V. N. Yakovenchuk
Keyword(s):  
Eudialyte Group ◽  
Layered Complex

The Mesoarchean Amikoq Layered Complex of SW Greenland: Part 2. Geochemical evidence for high-Mg noritic plutonism through crustal assimilation

2021 ◽  
pp. 1-64
Author(s):  
Emil Aarestrup ◽  
Iain McDonald ◽  
Paul E.B. Armitage ◽  
Allen P. Nutman ◽  
Ole Christiansen ◽  
...  
Keyword(s):  
Crustal Assimilation ◽  
Geochemical Evidence ◽  
Layered Complex

Nuggihalli schist belt in the Karnataka Craton; an Archean layered complex as interpreted from chromite distribution

1983 ◽  
Vol 78 (3) ◽  
pp. 507-513 ◽  
Author(s):  
Revanna Nijagunappa ◽  
Channappa Naganna
Keyword(s):  
Schist Belt ◽  
Layered Complex

Coupled substitutions in PGE-enriched cobaltite: new evidence from the Rio Jacaré layered complex, Bahia state, Brazil

2015 ◽  
Vol 79 (5) ◽  
pp. 1185-1193 ◽  
Author(s):  
Andrei Y. Barkov ◽  
Yana Fedortchouk ◽  
Robert A. Campbell ◽  
Tapio A.A. Halkoaho
Keyword(s):  
Layered Intrusion ◽  
Fluid Phase ◽  
Primary Phase ◽  
Sulfur Fugacity ◽  
Type Molecule ◽  
Substitution Mechanism ◽  
Compositional Variability ◽  
New Evidence ◽  
Layered Complex ◽  
Grain Core

AbstractMicrocrystals of platinum-group element (PGE)-bearing cobaltite occur in the Gulcari A deposit of vanadiferous titanomagnetite in the lower zone of the Rio Jacaré mafic-ultramafic layered intrusion, Brazil. Aggregates of cobaltite and sperrylite are cluster-like and developed generally along the boundary of Fe-Ti oxide grains with deuteric silicates. Our observations of cryptic zoning, compositional variability and interelement correlations are based on 37 analytical points (wavelength-dispersion spectrometry mode) of cobaltite, and indicate that Ir and Rh behave uniformly with Ni and antipathetically with Co which, in turn, correlates directly with S content. Iridium, Rh and Ni apparently substitute for Co in the As-enriched grain core, and the substitution mechanism invokes solid solution with a cattierite-type molecule: (Ni + Ir + Rh) + (AsS) = Co + (S2). The PGE-bearing cobaltite probably crystallized as a primary phase at 500 to 300°C, from microvolumes of a late fluid phase. The observed enrichment in S and decrease in the As:S ratio at the cobaltite grain margins is a reflection of the increase in sulfur fugacity (fS2) with decrease in temperature of crystallization.

scholarly journals Eudialyte Group Minerals from the Lovozero Alkaline Massif, Russia: Occurrence, Chemical Composition, and Petrogenetic Significance

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1070
Author(s):  
Julia A. Mikhailova ◽  
Yakov A. Pakhomovsky ◽  
Taras L. Panikorovskii ◽  
Ayya V. Bazai ◽  
Victor N. Yakovenchuk
Keyword(s):  
Chemical Composition ◽  
Nepheline Syenite ◽  
Granite Gneiss ◽  
Lovozero Massif ◽  
Eudialyte Group ◽  
Magmatic Stage ◽  
Late Magmatic Stage ◽  
Volcaniclastic Rocks ◽  
Layered Complex ◽  
Alkaline Massif

The Lovozero Alkaline Massif intruded through the Archean granite-gneiss and Devonian volcaniclastic rocks ca. 360 Ma ago and formed a large laccolith-type body. The lower part of the massif (the Layered complex) is composed of regularly repeating rhythms: melanocratic nepheline syenite (lujavrite, at the top), leucocratic nepheline syenite (foyaite), foidolite (urtite). The upper part of the massif (the Eudialyte complex) is indistinctly layered, and lujavrite enriched with eudialyte-group minerals (EGM) prevails there. In this article, we present the results of a study of the chemical composition and petrography of more than 400 samples of the EGM from the main types of rock of the Lovozero massif. In all types of rock, the EGM form at the late magmatic stage later than alkaline clinopyroxenes and amphiboles or simultaneously with it. When the crystallization of pyroxenes and EGM is simultaneous, the content of ferrous iron in the EGM composition increases. The Mn/Fe ratio in the EGM increases during fractional crystallization from lujavrite to foyaite and urtite. The same process leads to an increase in the modal content of EGM in the foyaite of the Layered complex and to the appearance of primary minerals of the lovozerite group in the foyaite of the Eudialyte complex.

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