Origin of placer laurite from Borneo: Se and As contents, and S isotopic compositions

2004 ◽  
Vol 68 (2) ◽  
pp. 353-368 ◽  
Author(s):  
K. H. Hattori ◽  
L. J. Cabri ◽  
B. Johanson ◽  
M. L. Zientek
Keyword(s):  
Solid Solutions ◽  
Ultramafic Rocks ◽  
Compositional Variation ◽  
Chemical Compositions ◽  
Group Mineral ◽  
Isotopic Compositions ◽  
Ophiolitic Rocks ◽  
Stage Process ◽  
Compositional Variations ◽  
Spherical Grains

AbstractWe examined grains of the platinum-group mineral, laurite (RuS2), from the type locality, Pontyn River, Tanah Laut, Borneo, and from the Tambanio River, southeast Borneo. The grains show a variety of morphologies, including euhedral grains with conchoidal fractures and pits, and spherical grains with no crystal faces, probably because of abrasion. Inclusions are rare, but one grain contains Ca-Al amphibole inclusions, and another contains an inclusion of chalcopyrite+bornite+pentlandite+heazlewoodite (Ni3S2) that is considered to have formed by a two-stage process of exsolution and crystallization from a once homogeneous Fe-Cu-Ni sulphide melt.All grains examined are solid solutions of Ru and Os with Ir (2.71 –11.76 wt.%) and Pd (0.31–0.66 wt.%). Their compositions are similar to laurite from ophiolitic rocks. The compositions show broad negative correlations between Os and Ir, between As and Ir, and between As (0.4 –0.74 wt.%) and Se (140 to 240 ppm). Laurite with higher Os contains more Se and less Ir and As. The negative correlations between Se and As may be attributed to their occupancy of the S site, but the compositional variations of Os, Ir and As probably reflect the compositional variation of rocks where the crystals grew.Ratios of S/Se in laurite show a narrow spread from 1380 to 2300, which are similar to ratios for sulphides from the refractory sub-arc mantle. Sulphur isotopic compositions of laurite are independent of chemical compositions and morphologies and are similar to the chondritic value of 0%. The data suggest that S in laurite has not undergone redox changes and originated from the refractory mantle. The data support the formation of laurite in the residual mantle or in a magma generated from such a refractory mantle, followed by erosion after the obduction of the host ultramafic rocks.

Electron microprobe study of turquoise-group solid solutions in the Neyshabour and Meydook mines, northeast and southern Iran

2020 ◽  
Vol 58 (1) ◽  
pp. 71-83
Author(s):  
Elahe Mansouri Gandomani ◽  
Nematollah Rashidnejad-Omran ◽  
Amir Emamjomeh ◽  
Pietro Vignola ◽  
Tahereh Hashemzadeh
Keyword(s):  
Solid Solution ◽  
Solid Solutions ◽  
Electron Microprobe ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Major Elements ◽  
Point Of View ◽  
Chemical Compositions ◽  
Light Blue ◽  
Quaternary Solid Solution

ABSTRACT Turquoise, CuAl6(PO4)4(OH)8·4H2O, belongs to the turquoise group, which consists of turquoise, chalcosiderite, aheylite, faustite, planerite, and UM1981-32-PO:FeH. In order to study turquoise-group solid solutions in samples from the Neyshabour and Meydook mines, 17 samples were selected and investigated using electron probe microanalysis. In addition, their major elements were compared in order to evaluate the feasibility of distinguishing the provenance of Persian turquoises. The electron microprobe data show that the studied samples are not constituted of pure turquoise (or any other pure endmember) and belong, from the chemical point of view, to turquoise-group solid solutions. In a turquoise–planerite–chalcosiderite–unknown mineral quaternary solid solution diagram, the chemical compositions of the analyzed samples lie along the turquoise–planerite line with minor involvement of chalcosiderite and the unknown mineral. Among light blue samples with varying hues and saturations from both studied areas, planerite is more abundant among samples from Meydook compared with samples from Neyshabour. Nevertheless, not all the light blue samples are planerite. This study demonstrates that distinguishing the deposit of origin for isochromatic blue and green turquoises, based on electron probe microanalysis method and constitutive major elements, is not possible.

scholarly journals Rinkite–nacareniobsite-(Ce) solid solution series and hainite from the Ilímaussaq alkaline complex: occurrence and compositional variation

2014 ◽  
Vol 62 ◽  
pp. 1-15
Author(s):  
Jørn G. Rønsbo ◽  
Henning Sørensen ◽  
Encarnacion Roda-Robles ◽  
François Fontan ◽  
Pierre Monchoux
Keyword(s):  
Solid Solution ◽  
Electron Microprobe ◽  
Compositional Variation ◽  
Solid Solution Series ◽  
Alkaline Complex ◽  
Full Extension ◽  
X Ray ◽  
Solution Series ◽  
Compositional Variations ◽  
A Minor

In the Ilímaussaq alkaline complex, minerals from the rinkite–nacareniobsite-(Ce) solid solution series have been found in pulaskite pegmatite, sodalite foyaite, naujaite and naujaite pegmatite from the roof sequence, and in marginal pegmatite, kakortokite and lujavrite from the floor sequence. The electron microprobe analyses embrace almost the full extension of the solid solution series and confirm its continuity. The solid solution series shows similar compositional variations in the roof and floor sequences: Rinkite members of the series are found in the less evolved rocks in the two sequences, whereas nacareniobsite-Ce members occur in the most evolved rocks and pegmatites in the two sequences. The REE (+Y) content varies from 0.83 atoms per formula unit (apfu) in rinkite from pulaskite pegmatite to 1.31 apfu in nacareniobsite-(Ce) from naujaite pegmatite. The main substitution mechanisms in the solid solution series investigated in this work are 2Ca2+ = Na+ + REE3+ and Ti4+ + Ca2+ = Nb5+ + Na+. The increased contents of Nb5+ and REE3+ are only to a minor degree compensated through the F1– = O2– substitution. The chondrite normalised REE patterns of the minerals develop in a similar way in the two sequences, showing relative La-enrichment and Y-depletion from the less to the most evolved rocks. Hainite has not previously been found in the Ilímaussaq complex. It was here identified in a pulaskite pegmatite sample by a combination of X-ray diffraction giving the unit cell dimensions a = 9.5923(7) Å, b = 7.3505(5) Å, c = 5.7023(4) Å, α = 89.958(2)°, β = 100.260(1)°, γ = 101.100(2)°, and X-ray powder pattern and electron microprobe data giving the empirical formula (Ca1.62 Zr0.16Y 0.22) (Na0.87Ca1.11) (Ca 1.65 REE0.35)Na(Ti0.81Nb0.09Fe0.08 Zr0.02)(Si2O7)2O0.99F2.96. Based on published and the present data it is documented that minerals from the hainite-götzenite solid solution series show a compositional variation between the ideal end members (Y,REE,Zr)Na2Ca4Ti(Si2O7)2OF3 and NaCa6Ti(Si2O7)2OF3.

The role of shallow open system processes in the evolution of South Tepeldag Pluton (NW Turkey): insights and constraints from thermodynamic modelling

2021 ◽  
Author(s):  
Tunahan Arık ◽  
Ömer Kamacı ◽  
Işıl Nur Güraslan ◽  
Şafak Altunkaynak
Keyword(s):  
Fractional Crystallization ◽  
Open System ◽  
Suture Zone ◽  
Thermodynamic Simulations ◽  
Nw Turkey ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Ophiolitic Rocks ◽  
Compositional Variations ◽  
Spider Diagrams

<p>Eocene granitoids in NW Anatolia occurred following the continental collision between Sakarya Continent and Tauride-Anatolide Platform and mark the onset of post-collisional magmatism in the region. One of the representative members of the Eocene granitoids, the Tepeldağ pluton crops out as two isolated granitic bodies and is intruded into the Cretaceous blueschist assemblages (Kocasu formation) and ophiolitic rocks within the Izmir-Ankara-Erzincan suture zone (IAESZ). South Tepeldağ pluton (STP) is composed mainly of granodiorite with subordinate quartz diorite, which show transitional contacts. Aplitic dykes crosscut the pluton as well as the country rocks. STP includes a number of mafic microgranular enclaves (MME) of gabbro/diorite composition.</p><p>Geochemically, STP shows distinct I-type affinity with a metaluminous to slightly peraluminous (ASI ≤1.02) nature. The samples are medium-K to high-K calc-alkaline in character. They exhibit depletion in HFSE (Ti, Hf, Zr, Nb and Ta) compared to large ion lithophile elements (Rb, Ba, Th, U, K) and presents negative Nb, P, Ti anomalies. STP displays slight negative Eu anomalies (Eu/Eu* = 0.7–1.2), enrichment in LREE and flat HREE patterns in chondrite-normalized spider diagrams. MELTS modeling (with initial parameters of 1–3 kbar pressure, 2–3% water and QFM-NNO oxygen fugacity buffers) indicate that compositional variations in STP samples can be interpreted as a result of open system processes (assimilation fractional crystallization) rather than a reflection of fractional crystallization in the upper crustal magma chamber. All thermodynamic simulations dictate a crustal assimilation, especially in the late stages of the magmatic process, with a MgO, Na<sub>2</sub>O and Al<sub>2</sub>O<sub>3</sub>-rich assimilant similar to the suture zone (IAESZ) rocks.</p>

Incorporation of REE into leucophanite: a compositional and structural study

2007 ◽  
Vol 71 (06) ◽  
pp. 625-640 ◽  
Author(s):  
H. Friis ◽  
T. Balić-Žunić ◽  
C. T. Williams ◽  
R. Garcia-Sanchez
Keyword(s):  
Trace Element ◽  
Element Concentration ◽  
Trace Element Concentration ◽  
Compositional Variation ◽  
Chemical Compositions ◽  
Charge Balance ◽  
Element Abundances ◽  
Chemical Factors ◽  
Crystallization Conditions ◽  
Compositional Zonation

Abstract The crystal structures of nine, and the chemical compositions of ten, natural samples of leucophanite, ideally NaCaBeSi2O6F, were investigated. The analysed samples display a large compositional variation with trace-element abundances >50,000 ppm, primarily due to rare earth elements (REE). Fromthese data, we propose a substitution scheme for the incorporation of REE for Ca, with additional Na substituting for Ca and the generation of vacancies to ensure charge balance. Compositional zonation was observed in some samples; this zonation correlates with variations in cathodoluminescence. The crystal structure of the nine analysed samples could all be refined in space group P212121. We found no evidence for a reduction of symmetry with increased trace-element concentration. Various twin combinations were observed and these seem related to crystallization conditions rather than structural or chemical factors.

The role of magma injection and crystal sorting in the formation of early gabbros at the Coldwell Complex, Ontario, Canada

2019 ◽  
Vol 56 (7) ◽  
pp. 715-737 ◽  
Author(s):  
Yong-hua Cao ◽  
David J. Good ◽  
Robert L. Linnen ◽  
Iain M. Samson
Keyword(s):  
Major Element ◽  
Mineral Chemistry ◽  
Ultramafic Rocks ◽  
Chemical Compositions ◽  
Olivine Gabbro ◽  
Additional Observation ◽  
Midcontinent Rift ◽  
Layered Series ◽  
Incompatible Elements

The Layered Series of the Midcontinent Rift related Coldwell Complex comprises thick sections of gabbro, without any known associated ultramafic rocks. It represents a major early intrusive unit of the Coldwell Complex and consists of thick accumulations of olivine gabbro and oxide augite melatroctolite. This study combines petrography, mineral chemistry, and lithogeochemistry to constrain the magma composition and petrogenesis of the Layered Series. The presence of cumulus orthoclase together with the observation that the Layered Series rocks plot in the alkaline field on a total alkali–silica diagram indicate that the Layered Series magma has an alkaline parentage. The stratigraphy of the Layered Series cannot be fully correlated between different areas using lithogeochemistry and mineral chemistry. This together with observed normal and reverse trends for mineral chemical compositions in different areas suggest that the processes related to magma emplacement and crystallization were different in different locations. The whole-rock concentrations of incompatible elements and the compositions of major minerals of the olivine gabbro and oxide augite melatroctolite units are chemically similar. However, major element lithogeochemistry is variable, dominantly due to differences in the abundances of olivine, clinopyroxene, plagioclase, and magnetite. An additional observation is that olivine and clinopyroxene are not in chemical equilibrium. Together, these observations are interpreted to reflect a combination of multiple injections of magma and crystal sorting in an open system.

Coupled substitutions in goldfieldite–tetrahedrite minerals from the Iriki mine, Japan

1991 ◽  
Vol 55 (381) ◽  
pp. 515-519 ◽  
Author(s):  
Masaaki Shimizu ◽  
Chris J. Stanley
Keyword(s):  
Solid Solution ◽  
Continuous Solid Solution ◽  
Chemical Compositions ◽  
Coupled Substitution ◽  
Compositional Variations ◽  
The Ideal

AbstractChemical compositions of goldfieldite-tetrahedrite series minerals from the Iriki mine in Japan are reported for the frst time. The compositional variations of coexisting goldfieldite [atomic proportion Te > (Sb + As + Bi)], tellurian tetrahedrite [Sb > (Te + As + Bi)], and Te-free tetrahedrite from this locality are considered alongside data from the literature. These show that the substitution of (Sb, As)3+ for Te4+ in natural goldfieldite-tetrahedrite series minerals occurs by the following two mechanisms: (i) tetrahedrite, and goldfieldite, form a continuous solid-solution according to the coupled substitution of Cu+Te4+ for (Cu,Fe,Zn)2+(Sb,As)3+, and (ii) goldfieldite, and the ideal end-member, might also form a continuous solid-solution by the coupled substitution of ☐(vacancy)Te4+ for Cu+(Sb,As)3+. According to this work, the general formulae of tellurian tetrahedrite and goldfieldite are, therefore, respectively, , with x = 0 to 2 and , with y = 0 to 2.

Metamorphic evolution of the Karimnagar granulite terrane, Eastern Dharwar Craton, south India

2010 ◽  
Vol 148 (1) ◽  
pp. 112-132 ◽  
Author(s):  
D. PRAKASH ◽  
I. N. SHARMA
Keyword(s):  
Granulite Facies ◽  
Dharwar Craton ◽  
Ultramafic Rocks ◽  
Chemical Compositions ◽  
Eastern Dharwar Craton ◽  
Geochronological Data ◽  
Rock Types ◽  
Wide Range ◽  
The Subject ◽  
Lower Crustal

AbstractThe Karimnagar granulite terrane is an integral part of the Eastern Dharwar Craton (EDC), India, having been the subject of much interest because of the only reported granulite facies rocks in the EDC. It shows a large variety of rock types with a wide range of mineral parageneses and chemical compositions, namely charnockites (Opx+Pl+perthite+Qtz±Bt±Grt), gneisses (Opx+Crd+Bt+Pl+Qtz+perthite±Sil±Grt±Spl; Bt+Qtz+Pl±Crd±Hbl±Spl), mafic granulites (Cpx+Pl+Qtz±Opx±Hbl), quartz-free granulites (Spr+Spl+Bt+Crd+Kfs+Crn; Bt+Crd+Kfs±Crn±Spl±Krn; And+Bt+Kfs+Chl), granites (Qtz+Pl+Kfs±Bt±Hbl), altered ultramafic rocks (Chl+Trem+Tlc), metadolerites (Cpx+Pl±Bt±Qtz±Chl), banded magnetite quartzites and quartzites. Andalusite- and chlorite-bearing assemblages presumably suggest a retrograde origin. Investigation of quartz-free granulites of the area brings out some interesting and important observations, reflecting the presence of refractory phases. These granulites are devoid of sillimanite and contain corundum instead. Reaction textures in the gneisses include breakdown of garnet to form coronas and symplectites of orthopyroxene+cordierite, formation of cordierite from garnet+sillimanite+quartz and late retrograde biotite and biotite+quartz symplectites. In the mafic granulites, inclusions of quartz and hornblende within orthopyroxene are interpreted as being a part of the prograde assemblage. At a later stage orthopyroxene is also rimmed by hornblende. The quartz-free granulites display a variety of spectacular coronas, for example, successive rims on corundum consisting of spinel+sapphirine+cordierite±orthopyroxene, rare skeletal symplectitic intergrowth of sapphirine+cordierite+potash feldspar, and late retrograde formation of chlorite, corundum, spinel and andalusite from sapphirine±cordierite. Based on chemographic relationships and petrogenetic grids, a sequence of prograde, isothermal decompressive and retrograde reactions have been inferred. Quartz-free sapphirine granulites and mafic granulites record the highest P–T conditions (~7 kbar, 850°C), whereas the gneisses were formed at lower P–T conditions (~5 kbar, 800°C). In addition, the presence of andalusite-bearing rocks suggests a pressure of around 2.5 kbar. This change in pressure from 7 kbar to around 2.5 kbar suggests a decompressive path for the evolution of granulites in the study area, which indicates an uplift for the granulite-facies rocks from lower crustal conditions. The implications for supercontinent history are also addressed in light of available geochronological data.

scholarly journals Analytical protocols for Phobos regolith samples returned by the Martian Moons eXploration (MMX) mission

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Wataru Fujiya ◽  
Yoshihiro Furukawa ◽  
Haruna Sugahara ◽  
Mizuho Koike ◽  
Ken-ichi Bajo ◽  
...  
Keyword(s):  
Noble Gas ◽  
Geochemical Data ◽  
Chemical Compositions ◽  
Isotopic Compositions ◽  
Bulk Chemical ◽  
Sample Return Mission ◽  
Crucial Information ◽  
Sampling Systems ◽  
Japan Aerospace Exploration Agency ◽  
Analytical Protocols

AbstractJapan Aerospace Exploration Agency (JAXA) will launch a spacecraft in 2024 for a sample return mission from Phobos (Martian Moons eXploration: MMX). Touchdown operations are planned to be performed twice at different landing sites on the Phobos surface to collect > 10 g of the Phobos surface materials with coring and pneumatic sampling systems on board. The Sample Analysis Working Team (SAWT) of MMX is now designing analytical protocols of the returned Phobos samples to shed light on the origin of the Martian moons as well as the evolution of the Mars–moon system. Observations of petrology and mineralogy, and measurements of bulk chemical compositions and stable isotopic ratios of, e.g., O, Cr, Ti, and Zn can provide crucial information about the origin of Phobos. If Phobos is a captured asteroid composed of primitive chondritic materials, as inferred from its reflectance spectra, geochemical data including the nature of organic matter as well as bulk H and N isotopic compositions characterize the volatile materials in the samples and constrain the type of the captured asteroid. Cosmogenic and solar wind components, most pronounced in noble gas isotopic compositions, can reveal surface processes on Phobos. Long- and short-lived radionuclide chronometry such as 53Mn–53Cr and 87Rb–87Sr systematics can date pivotal events like impacts, thermal metamorphism, and aqueous alteration on Phobos. It should be noted that the Phobos regolith is expected to contain a small amount of materials delivered from Mars, which may be physically and chemically different from any Martian meteorites in our collection and thus are particularly precious. The analysis plan will be designed to detect such Martian materials, if any, from the returned samples dominated by the endogenous Phobos materials in curation procedures at JAXA before they are processed for further analyses.

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