Brian Joy | Queen's University at Kingston (original) (raw)

Papers by Brian Joy

Geochimica et Cosmochimica Acta, Aug 1, 2020

Northwest Africa (NWA) 7042 is an intermediate, permafic shergottite consisting of two generation... more Northwest Africa (NWA) 7042 is an intermediate, permafic shergottite consisting of two generations of olivine (early zoned olivine Fo 41-76 , and late-stage fayalitic olivine Fo 46-56), complexly zoned pyroxene (En 35-64 Fs 22-46 Wo 5-34), shock-melted or maskelynitized feldspar (An 5-30 Ab 16-61 Or 1-47), and accessory merrillite, apatite, ilmenite, titanomagnetite, Fe-Cr-Ti spinels, pyrrhotite, and baddeleyite. The zoned olivine grains have been pervasively modified, containing conspicuous brown Mgrich cores surrounded by colorless, unaltered Fe-rich overgrowth rims. This textural relationship suggests that the cores were altered at magmatic temperatures prior to crystallization of the rims on Mars. Launch-generated shock veins in NWA 7042 also crosscut and displace several of the altered olivine grains indicating that alteration occurred before ejection of the meteorite. While this type of olivine alteration is rare in shergottites, it is similar to deuterically altered olivine in basalts and gabbros on Earth, caused by residual water-rich magmatic fluids. Transmission electron microscopy analysis of the olivine alteration did not reveal the high-temperature phases expected from this process; however, NWA 7042 has also been subjected to extensive terrestrial weathering, which may explain their absence. The potential presence of deuterically altered olivine in NWA 7042 has significant implications, as it is the third martian meteorite where deuteric alteration of olivine has been observed (the others being NWA 10416, and Allan Hills 77005). The different mantle sources for the parental melts of these three meteorites would suggest many, if not all martian mantle reservoirs have the potential to produce water-rich magmas.

The Canadian Mineralogist, 2014

ABSTRACT ABstRACt Itsiite, ideally Ba 2 Ca(BSi 2 O 7) 2 , is a new mineral from the Gun claim, ju... more ABSTRACT ABstRACt Itsiite, ideally Ba 2 Ca(BSi 2 O 7) 2 , is a new mineral from the Gun claim, just south of the Itsi Range, Yukon Territory, Canada. The new mineral occurs in low temperature, late-stage veins in direct association with cerchiaraite-(Fe), diopside, pyrite, quartz, sphalerite, and witherite. Itsiite occurs as colorless and light blue to medium greenish-blue tetragonal plates up to 1 mm across. The plates are flattened on {001} and exhibit the forms {001}, {101}, and {112}. The mineral is transparent, has a vitreous luster, and is non-fluorescent. It has a white streak and Mohs hardness of approximately 5½. It is brittle, with splintery fracture, and one perfect cleavage on {001}. The calculated density based upon the empirical formula and single-crystal unit cell is 3.644 g/cm 3. The mineral is optically uniaxial (–), with ω = 1.623(1) and ε = 1.619(1) (white light). The mineral is nonpleochroic. Electron-microprobe compositions (average of 3) provided: Na 2 O 0.06, BaO 46.35, CaO 7.35, FeO 0.15, Al 2 O 3 0.17, TiO 2 0.06, SiO 2 34.91, B 2 O 3 10.41 (from structure), total 99.46 wt.%. The empirical formula (based on 14 O apfu) is Ba 2.06 (Ca 0.89 Al 0.02 Na 0.01 Fe 0.01 Ti 0.01) Σ0.94 (Si 3.96 B 2.04) Σ6.00 O 14. Itsiite is tetragonal, I42m, a 10.9515(5), c 10.3038(7) Å, V 1235.79(11) Å 3 , and Z = 4. The nine most intense lines in the X-ray powder diffraction pattern are [d obs in Å(I)(hkl)]: 5.50(42)(200); 3.746(100)(202); 3.446(60)(301); 3.100(51)(222); 2.899(96)(321,312); 2.279(44)(323); 2.145(69)(224,501); 1.8257(41)(503,334,305); 1.7584(43)(532,523). The crystal structure (R 1 = 1.8% for 992 F o > 4sF) is based upon a zeolite-like tetrahedral framework of corner-sharing tetrahedra consisting of four-membered silicate rings alternating with four-membered borate rings. The framework contains channels along each axis that host Ba 2+ in ninefold coordination and Ca 2+ in sixfold coordination. The structure is very similar to those of hyalotekite and kapitsaite-(Y).

The Canadian Mineralogist, 2019

Cadwaladerite, described in 1941 as Al(OH)2Cl·4H2O, and lesukite, described in 1997 as Al2(OH)5Cl... more Cadwaladerite, described in 1941 as Al(OH)2Cl·4H2O, and lesukite, described in 1997 as Al2(OH)5Cl·2H2O, are very closely related chemically and structurally, but are found in very different environments. Cadwaladerite was found at the edge of a salar in Chile. Lesukite has been described from a volcanic fumarole and from burning coal seams. Both materials have cubic symmetry with a = 19.788 to 19.859Å. The crystal structure, common to both, consists of a rigid three-dimensional framework of edge- and corner-sharing Al(OH,H2O)6 octahedra that contains large interconnected cavities where loosely held Cl, OH, and H2O are located. The fact that Cl is loosely held within the structure is demonstrated by a dramatic reduction in Cl content after washing the material in distilled water, while the structural integrity is maintained. Herein, cadwaladerite is confirmed as a valid mineral species and lesukite is discredited because the only difference between the two materials is the loosely he...

Mineralium Deposita, 2019

The Jacurici Complex hosts the largest chromite deposit in Brazil in an up to 8-m-thick chromitit... more The Jacurici Complex hosts the largest chromite deposit in Brazil in an up to 8-m-thick chromitite layer within a tectonically segmented 300-m-thick intrusion. The ore has been interpreted as the result of crustal contamination-driven crystallization in a magma conduit. This study addresses the stratigraphy, mineralogical and textural relationships, and mineral chemistry of the Monte Alegre Sul segment focusing on chromite-hosted inclusions from the Main Chromitite Layer to understand the role of volatiles in the genesis of the massive chromitite. Silicate inclusions (enstatite, phlogopite, magnesiohornblende, diopside and olivine) are commonly monomineralic and sub- to euhedral, and crystallized prior to, or coeval with, the chromite crystallization. Carbonate inclusions (dolomite and magnesite) are irregular or have negative crystal shapes, suggesting entrapment as melt droplets. Sulfides (pentlandite, millerite, heazlewoodite, polydymite, pyrite, and chalcopyrite) are often polymineralic, irregular, or hexagonal-shaped, indicating entrapment as sulfide melt and as monosulfide solid solution. The inclusions indicate an H 2 O- and S-saturated resident magma with immiscible droplets of carbonate melt during chromite crystallization. Inclusion-rich and inclusion-free chromites that occur together have similar compositions and are considered to have formed from the same magma in response to variations in the degree of Cr saturation. Hot primitive magma might have heated and mobilized CO 2 and probably water from devolatized and assimilated carbonate-rich wall rocks, increasing f O 2 and triggering chromite crystallization. We propose that the formation of the chromitite layer started as in situ crystallization with additional material added by slumping of locally remobilized chromite slurries, facilitated by the presence of volatiles.

The Canadian Mineralogist, 2016

Meierite, ideally Ba 44 Si 66 Al 30 O 192 Cl 25 (OH) 33 , is a new mineral from the Gun claim, ju... more Meierite, ideally Ba 44 Si 66 Al 30 O 192 Cl 25 (OH) 33 , is a new mineral from the Gun claim, just south of the Itsi Range, Yukon, Canada. Meierite occurs as equant grains up to 200 lm across, enclosed within large gillespite crystals. The mineral is transparent, has a vitreous luster, and is non-fluorescent. It has a white streak and Mohs hardness of approximately 5½. It is brittle with no observed cleavage. The calculated density based upon the chemical formula and single-crystal unit-cell dimension is 3.50 g/cm 3. The mineral is optically isotropic (n

The Canadian Mineralogist, 2015

The chemical compositions of uraninites from five major deposit types (tabular, unconformity, vei... more The chemical compositions of uraninites from five major deposit types (tabular, unconformity, vein, metasomatic, and igneous), measured by electron microprobe and LA-ICP-MS, underline the extreme chemical variation of natural uraninite, due to different formation conditions prevailing at each deposit type. Apart from the major elements always analyzed in uraninite (U, Th, Y, REE, Pb, as well as Si, Ca, and Fe), several additional elements are present in uraninite to a significant degree: Mn (overall median value of 6088 ppm), V (4528 ppm), Na (2365 ppm), As (2251 ppm), W (1811 ppm), Mg (441 ppm), Sb (286 ppm), Sr (261 ppm), Ti (235 ppm), Mo (133 ppm), Bi (125 ppm), and Ba (118 ppm). Uraninites from different deposit types have distinct chemical compositions: tabular-type uraninites have the lowest Th, Y, and REE and the highest trace elements, in particular Mg, Mn, and V; sandstone-hosted unconformity-related uraninites have the lowest Y and the highest Fe, Na, Cu, Ni, and Ni; basement-hosted unconformity-related uraninites have the lowest Ca and Fe and the highest Ti, Ni, and W; metasomatism-related uraninites have the lowest Y and the highest Th and Si; and igneous uraninites have the lowest trace elements and the highest Th, Y, REE, Zr, and Hf. The vein-type uraninites have the most variable chemical compositions. In addition to the REE spectra, with only the igneous uraninites displaying a negative Eu anomaly, the chemical compositions of uraninites can be used with high confidence as provenance indicators.

The Canadian Mineralogist, 2015

A uraninite crystal from the Roode pegmatite in southern Norway displays clear sector zoning most... more A uraninite crystal from the Roode pegmatite in southern Norway displays clear sector zoning mostly defined by the main U-Th substitution, with sharp changes in chemical compositions between the cubic and the octahedral sectors; a weaker concentric zoning defined by the same chemical variations is also present. The {100} sectors incorporate slightly more U whereas the {111} sectors incorporate slightly more Th, Y, and REEs. The cubic sectors contain on average ca. 77.0 wt.% UO2, ca. 6.6 wt.% ThO2, ca. 0.6 wt.% ΣREE2O3, and ca. 0.45 wt.% Y2O3; the octahedral sectors contain on average ca. 73.8 wt.% UO2, ca. 9.1 wt.% ThO2, ca. 0.8 wt.% ΣREE2O3, and ca. 0.55 wt.% Y2O3. The development of sector zoning in uraninite is possibly due to the interplay between the difference in effective ionic radius between U and Th and the difference in protosite density between the {100} and {111} sectors.

The Canadian Mineralogist, 2014

In our 2014 paper ([Joy & Evans 2014][1], p. 349–351), we gave reasons for preferring to use ... more In our 2014 paper ([Joy & Evans 2014][1], p. 349–351), we gave reasons for preferring to use an earlier IMA nomenclature scheme (IMA 1997) for the Mg-Fe-Mn amphiboles ([Leake et al . 1997][2], [2003][3]) rather than the latest version, IMA 2012 ([Hawthorne et al . 2012][4]). [Hawthorne et al

The Canadian Mineralogist, 2014

A high-Cr mineral assemblage is observed in the unusual Matoush uranium deposit (Quebec, Canada),... more A high-Cr mineral assemblage is observed in the unusual Matoush uranium deposit (Quebec, Canada), which is associated with the bimodal Matoush dike intruding Otish Basin sandstones. In addition to uraninite, both silicate (chromium-dravite and chromphyllite) and oxide (eskolaite) high-Cr minerals are present in major amounts. While high-Cr dravite and high-Cr muscovite have been described previously, eskolaite, Cr 2 O 3 , has not been studied extensively. The highest Cr contents observed in the Matoush silicates, obtained by electron microprobe, are comparable with the highest ever documented in the literature, with Cr 2 O 3 of up to ca. 22 wt.% in chromphyllite and ca. 37 wt.% in chromium-dravite. Complete solid solutions among hematite (Fe 2 O 3), eskolaite, and karelianite (V 2 O 3) are theoretically possible, but until now only complete Cr-V substitution had been documented in natural samples. Matoush eskolaite contains significant amounts of Fe, with up to 37% wt.% Fe 2 O 3 substitution, and minimal V substitution (typically under 0.5 wt.% V 2 O 3). A hydrated Fe-Cr oxide is also observed closely associated with eskolaite at Matoush, having the same Cr:Fe:V ratio as eskolaite, but with significant assumed H 2 O. Rietveld analysis of X-ray powder diffraction data is best fit using a model that includes eskolaite and a second hydrated crystalline Fe-Cr oxide with a similar atomic structure to eskolaite, but a significantly larger c-axis dimension.

The Canadian Mineralogist, 2013

Wilcoxite, (Mg 0.81 Mn 0.07 Fe 0.04 Zn 0.04) Σ0.96 Al 1.01 (SO 4) 2 F 1.02 •17H 2 O, is a seconda... more Wilcoxite, (Mg 0.81 Mn 0.07 Fe 0.04 Zn 0.04) Σ0.96 Al 1.01 (SO 4) 2 F 1.02 •17H 2 O, is a secondary sulfate mineral that occurs in hydrothermal systems containing significant amounts of fluorine. A sample of wilcoxite was collected from abandoned mine workings east of Rico, Dolores Co., Colorado, U.S.A., where it occurs as white, efflorescent crusts composed of small anhedral crystals within a timber crib that protected the material from direct exposure to rain and snow, but not from changes in the humidity and temperature of the atmosphere. It is remarkable that this highly hydrated mineral has remained stable under these conditions. Unit cell dimensions are a 6.644(1), b 6.749(2), and c 14.892(3) Å, α 79.664(4)°, β 80.113(4)°, γ 62.487(3)°, and V 579.6(2) Å 3 , space group P The previously unknown crystal structure was determined from single-crystal X-ray diffraction data and consists of isolated sulfate tetrahedra, Mg(H 2 O) 6 octahedra, and Al(H 2 O,F) 6 octahedra connected only through hydrogen bonding involving additional water molecules. Wilcoxite has 1.5 water molecules per sulfate tetrahedron that do not participate in the formation of an Al(H 2 O,F) 6 or Mg(H 2 O) 6 octahedron. The water molecules held within the epsomite (MgSO 4 •7H 2 O) structure are lost if the relative humidity (RH) drops below 50% at 298 K, and hexahydrite (MgSO 4 •6H 2 O) loses water to form starkeyite (MgSO 4 •4H 2 O) at 40% RH at 298 K. The fact that wilcoxite, with such a high water content, is stable when the magnesium sulfate with which it coexists has become starkeyite indicates that water molecules are more tightly bonded within the wilcoxite structure. If epsomite crystals are warmed slightly they slowly become first translucent and then an opaque white powder, whereas wilcoxite does not dehydrate but abruptly melts when warmed. This behavior is similar to the incongruent melting of meridianiite (MgSO 4 •11H 2 O) on warming above 2 °C.

Geology, 2015

Th-Pb dating of monazite in xenoliths of low-temperature metamorphic eclogite facies rocks from d... more Th-Pb dating of monazite in xenoliths of low-temperature metamorphic eclogite facies rocks from diatremes of the Navajo volcanic field in the center of the Colorado Plateau (southwest United States) yields ages of ca. 28 Ma. Because monazite is not a primary phase in basic igneous or metamorphic rocks, but introduced during metasomatism, we suggest that the fluid responsible for monazite growth was derived from prograde metamorphic dehydration reactions in serpentinites and related rocks in the subducted Farallon plate. These fluids hydrated the overlying sub-plateau lithospheric mantle, consuming garnet (thus mobilizing rare earth elements) and lowering mantle density and increasing volume, contributing to the uplift of the Colorado Plateau in early Oligocene time. their employment. Individual scientists are hereby granted permission, without fees or further Copyright not claimed on content prepared wholly by U.S. government employees within scope of Notes articles must include the digital object identifier (DOIs) and date of initial publication. priority; they are indexed by GeoRef from initial publication. Citations to Advance online prior to final publication). Advance online articles are citable and establish publication yet appeared in the paper journal (edited, typeset versions may be posted when available Advance online articles have been peer reviewed and accepted for publication but have not

Geochimica et Cosmochimica Acta, Aug 1, 2020

Northwest Africa (NWA) 7042 is an intermediate, permafic shergottite consisting of two generation... more Northwest Africa (NWA) 7042 is an intermediate, permafic shergottite consisting of two generations of olivine (early zoned olivine Fo 41-76 , and late-stage fayalitic olivine Fo 46-56), complexly zoned pyroxene (En 35-64 Fs 22-46 Wo 5-34), shock-melted or maskelynitized feldspar (An 5-30 Ab 16-61 Or 1-47), and accessory merrillite, apatite, ilmenite, titanomagnetite, Fe-Cr-Ti spinels, pyrrhotite, and baddeleyite. The zoned olivine grains have been pervasively modified, containing conspicuous brown Mgrich cores surrounded by colorless, unaltered Fe-rich overgrowth rims. This textural relationship suggests that the cores were altered at magmatic temperatures prior to crystallization of the rims on Mars. Launch-generated shock veins in NWA 7042 also crosscut and displace several of the altered olivine grains indicating that alteration occurred before ejection of the meteorite. While this type of olivine alteration is rare in shergottites, it is similar to deuterically altered olivine in basalts and gabbros on Earth, caused by residual water-rich magmatic fluids. Transmission electron microscopy analysis of the olivine alteration did not reveal the high-temperature phases expected from this process; however, NWA 7042 has also been subjected to extensive terrestrial weathering, which may explain their absence. The potential presence of deuterically altered olivine in NWA 7042 has significant implications, as it is the third martian meteorite where deuteric alteration of olivine has been observed (the others being NWA 10416, and Allan Hills 77005). The different mantle sources for the parental melts of these three meteorites would suggest many, if not all martian mantle reservoirs have the potential to produce water-rich magmas.

The Canadian Mineralogist, 2014

ABSTRACT ABstRACt Itsiite, ideally Ba 2 Ca(BSi 2 O 7) 2 , is a new mineral from the Gun claim, ju... more ABSTRACT ABstRACt Itsiite, ideally Ba 2 Ca(BSi 2 O 7) 2 , is a new mineral from the Gun claim, just south of the Itsi Range, Yukon Territory, Canada. The new mineral occurs in low temperature, late-stage veins in direct association with cerchiaraite-(Fe), diopside, pyrite, quartz, sphalerite, and witherite. Itsiite occurs as colorless and light blue to medium greenish-blue tetragonal plates up to 1 mm across. The plates are flattened on {001} and exhibit the forms {001}, {101}, and {112}. The mineral is transparent, has a vitreous luster, and is non-fluorescent. It has a white streak and Mohs hardness of approximately 5½. It is brittle, with splintery fracture, and one perfect cleavage on {001}. The calculated density based upon the empirical formula and single-crystal unit cell is 3.644 g/cm 3. The mineral is optically uniaxial (–), with ω = 1.623(1) and ε = 1.619(1) (white light). The mineral is nonpleochroic. Electron-microprobe compositions (average of 3) provided: Na 2 O 0.06, BaO 46.35, CaO 7.35, FeO 0.15, Al 2 O 3 0.17, TiO 2 0.06, SiO 2 34.91, B 2 O 3 10.41 (from structure), total 99.46 wt.%. The empirical formula (based on 14 O apfu) is Ba 2.06 (Ca 0.89 Al 0.02 Na 0.01 Fe 0.01 Ti 0.01) Σ0.94 (Si 3.96 B 2.04) Σ6.00 O 14. Itsiite is tetragonal, I42m, a 10.9515(5), c 10.3038(7) Å, V 1235.79(11) Å 3 , and Z = 4. The nine most intense lines in the X-ray powder diffraction pattern are [d obs in Å(I)(hkl)]: 5.50(42)(200); 3.746(100)(202); 3.446(60)(301); 3.100(51)(222); 2.899(96)(321,312); 2.279(44)(323); 2.145(69)(224,501); 1.8257(41)(503,334,305); 1.7584(43)(532,523). The crystal structure (R 1 = 1.8% for 992 F o > 4sF) is based upon a zeolite-like tetrahedral framework of corner-sharing tetrahedra consisting of four-membered silicate rings alternating with four-membered borate rings. The framework contains channels along each axis that host Ba 2+ in ninefold coordination and Ca 2+ in sixfold coordination. The structure is very similar to those of hyalotekite and kapitsaite-(Y).

The Canadian Mineralogist, 2019

Cadwaladerite, described in 1941 as Al(OH)2Cl·4H2O, and lesukite, described in 1997 as Al2(OH)5Cl... more Cadwaladerite, described in 1941 as Al(OH)2Cl·4H2O, and lesukite, described in 1997 as Al2(OH)5Cl·2H2O, are very closely related chemically and structurally, but are found in very different environments. Cadwaladerite was found at the edge of a salar in Chile. Lesukite has been described from a volcanic fumarole and from burning coal seams. Both materials have cubic symmetry with a = 19.788 to 19.859Å. The crystal structure, common to both, consists of a rigid three-dimensional framework of edge- and corner-sharing Al(OH,H2O)6 octahedra that contains large interconnected cavities where loosely held Cl, OH, and H2O are located. The fact that Cl is loosely held within the structure is demonstrated by a dramatic reduction in Cl content after washing the material in distilled water, while the structural integrity is maintained. Herein, cadwaladerite is confirmed as a valid mineral species and lesukite is discredited because the only difference between the two materials is the loosely he...

Mineralium Deposita, 2019

The Jacurici Complex hosts the largest chromite deposit in Brazil in an up to 8-m-thick chromitit... more The Jacurici Complex hosts the largest chromite deposit in Brazil in an up to 8-m-thick chromitite layer within a tectonically segmented 300-m-thick intrusion. The ore has been interpreted as the result of crustal contamination-driven crystallization in a magma conduit. This study addresses the stratigraphy, mineralogical and textural relationships, and mineral chemistry of the Monte Alegre Sul segment focusing on chromite-hosted inclusions from the Main Chromitite Layer to understand the role of volatiles in the genesis of the massive chromitite. Silicate inclusions (enstatite, phlogopite, magnesiohornblende, diopside and olivine) are commonly monomineralic and sub- to euhedral, and crystallized prior to, or coeval with, the chromite crystallization. Carbonate inclusions (dolomite and magnesite) are irregular or have negative crystal shapes, suggesting entrapment as melt droplets. Sulfides (pentlandite, millerite, heazlewoodite, polydymite, pyrite, and chalcopyrite) are often polymineralic, irregular, or hexagonal-shaped, indicating entrapment as sulfide melt and as monosulfide solid solution. The inclusions indicate an H 2 O- and S-saturated resident magma with immiscible droplets of carbonate melt during chromite crystallization. Inclusion-rich and inclusion-free chromites that occur together have similar compositions and are considered to have formed from the same magma in response to variations in the degree of Cr saturation. Hot primitive magma might have heated and mobilized CO 2 and probably water from devolatized and assimilated carbonate-rich wall rocks, increasing f O 2 and triggering chromite crystallization. We propose that the formation of the chromitite layer started as in situ crystallization with additional material added by slumping of locally remobilized chromite slurries, facilitated by the presence of volatiles.

The Canadian Mineralogist, 2016

Meierite, ideally Ba 44 Si 66 Al 30 O 192 Cl 25 (OH) 33 , is a new mineral from the Gun claim, ju... more Meierite, ideally Ba 44 Si 66 Al 30 O 192 Cl 25 (OH) 33 , is a new mineral from the Gun claim, just south of the Itsi Range, Yukon, Canada. Meierite occurs as equant grains up to 200 lm across, enclosed within large gillespite crystals. The mineral is transparent, has a vitreous luster, and is non-fluorescent. It has a white streak and Mohs hardness of approximately 5½. It is brittle with no observed cleavage. The calculated density based upon the chemical formula and single-crystal unit-cell dimension is 3.50 g/cm 3. The mineral is optically isotropic (n

The Canadian Mineralogist, 2015

The chemical compositions of uraninites from five major deposit types (tabular, unconformity, vei... more The chemical compositions of uraninites from five major deposit types (tabular, unconformity, vein, metasomatic, and igneous), measured by electron microprobe and LA-ICP-MS, underline the extreme chemical variation of natural uraninite, due to different formation conditions prevailing at each deposit type. Apart from the major elements always analyzed in uraninite (U, Th, Y, REE, Pb, as well as Si, Ca, and Fe), several additional elements are present in uraninite to a significant degree: Mn (overall median value of 6088 ppm), V (4528 ppm), Na (2365 ppm), As (2251 ppm), W (1811 ppm), Mg (441 ppm), Sb (286 ppm), Sr (261 ppm), Ti (235 ppm), Mo (133 ppm), Bi (125 ppm), and Ba (118 ppm). Uraninites from different deposit types have distinct chemical compositions: tabular-type uraninites have the lowest Th, Y, and REE and the highest trace elements, in particular Mg, Mn, and V; sandstone-hosted unconformity-related uraninites have the lowest Y and the highest Fe, Na, Cu, Ni, and Ni; basement-hosted unconformity-related uraninites have the lowest Ca and Fe and the highest Ti, Ni, and W; metasomatism-related uraninites have the lowest Y and the highest Th and Si; and igneous uraninites have the lowest trace elements and the highest Th, Y, REE, Zr, and Hf. The vein-type uraninites have the most variable chemical compositions. In addition to the REE spectra, with only the igneous uraninites displaying a negative Eu anomaly, the chemical compositions of uraninites can be used with high confidence as provenance indicators.

The Canadian Mineralogist, 2015

A uraninite crystal from the Roode pegmatite in southern Norway displays clear sector zoning most... more A uraninite crystal from the Roode pegmatite in southern Norway displays clear sector zoning mostly defined by the main U-Th substitution, with sharp changes in chemical compositions between the cubic and the octahedral sectors; a weaker concentric zoning defined by the same chemical variations is also present. The {100} sectors incorporate slightly more U whereas the {111} sectors incorporate slightly more Th, Y, and REEs. The cubic sectors contain on average ca. 77.0 wt.% UO2, ca. 6.6 wt.% ThO2, ca. 0.6 wt.% ΣREE2O3, and ca. 0.45 wt.% Y2O3; the octahedral sectors contain on average ca. 73.8 wt.% UO2, ca. 9.1 wt.% ThO2, ca. 0.8 wt.% ΣREE2O3, and ca. 0.55 wt.% Y2O3. The development of sector zoning in uraninite is possibly due to the interplay between the difference in effective ionic radius between U and Th and the difference in protosite density between the {100} and {111} sectors.

The Canadian Mineralogist, 2014

In our 2014 paper ([Joy & Evans 2014][1], p. 349–351), we gave reasons for preferring to use ... more In our 2014 paper ([Joy & Evans 2014][1], p. 349–351), we gave reasons for preferring to use an earlier IMA nomenclature scheme (IMA 1997) for the Mg-Fe-Mn amphiboles ([Leake et al . 1997][2], [2003][3]) rather than the latest version, IMA 2012 ([Hawthorne et al . 2012][4]). [Hawthorne et al

The Canadian Mineralogist, 2014

A high-Cr mineral assemblage is observed in the unusual Matoush uranium deposit (Quebec, Canada),... more A high-Cr mineral assemblage is observed in the unusual Matoush uranium deposit (Quebec, Canada), which is associated with the bimodal Matoush dike intruding Otish Basin sandstones. In addition to uraninite, both silicate (chromium-dravite and chromphyllite) and oxide (eskolaite) high-Cr minerals are present in major amounts. While high-Cr dravite and high-Cr muscovite have been described previously, eskolaite, Cr 2 O 3 , has not been studied extensively. The highest Cr contents observed in the Matoush silicates, obtained by electron microprobe, are comparable with the highest ever documented in the literature, with Cr 2 O 3 of up to ca. 22 wt.% in chromphyllite and ca. 37 wt.% in chromium-dravite. Complete solid solutions among hematite (Fe 2 O 3), eskolaite, and karelianite (V 2 O 3) are theoretically possible, but until now only complete Cr-V substitution had been documented in natural samples. Matoush eskolaite contains significant amounts of Fe, with up to 37% wt.% Fe 2 O 3 substitution, and minimal V substitution (typically under 0.5 wt.% V 2 O 3). A hydrated Fe-Cr oxide is also observed closely associated with eskolaite at Matoush, having the same Cr:Fe:V ratio as eskolaite, but with significant assumed H 2 O. Rietveld analysis of X-ray powder diffraction data is best fit using a model that includes eskolaite and a second hydrated crystalline Fe-Cr oxide with a similar atomic structure to eskolaite, but a significantly larger c-axis dimension.

The Canadian Mineralogist, 2013

Wilcoxite, (Mg 0.81 Mn 0.07 Fe 0.04 Zn 0.04) Σ0.96 Al 1.01 (SO 4) 2 F 1.02 •17H 2 O, is a seconda... more Wilcoxite, (Mg 0.81 Mn 0.07 Fe 0.04 Zn 0.04) Σ0.96 Al 1.01 (SO 4) 2 F 1.02 •17H 2 O, is a secondary sulfate mineral that occurs in hydrothermal systems containing significant amounts of fluorine. A sample of wilcoxite was collected from abandoned mine workings east of Rico, Dolores Co., Colorado, U.S.A., where it occurs as white, efflorescent crusts composed of small anhedral crystals within a timber crib that protected the material from direct exposure to rain and snow, but not from changes in the humidity and temperature of the atmosphere. It is remarkable that this highly hydrated mineral has remained stable under these conditions. Unit cell dimensions are a 6.644(1), b 6.749(2), and c 14.892(3) Å, α 79.664(4)°, β 80.113(4)°, γ 62.487(3)°, and V 579.6(2) Å 3 , space group P The previously unknown crystal structure was determined from single-crystal X-ray diffraction data and consists of isolated sulfate tetrahedra, Mg(H 2 O) 6 octahedra, and Al(H 2 O,F) 6 octahedra connected only through hydrogen bonding involving additional water molecules. Wilcoxite has 1.5 water molecules per sulfate tetrahedron that do not participate in the formation of an Al(H 2 O,F) 6 or Mg(H 2 O) 6 octahedron. The water molecules held within the epsomite (MgSO 4 •7H 2 O) structure are lost if the relative humidity (RH) drops below 50% at 298 K, and hexahydrite (MgSO 4 •6H 2 O) loses water to form starkeyite (MgSO 4 •4H 2 O) at 40% RH at 298 K. The fact that wilcoxite, with such a high water content, is stable when the magnesium sulfate with which it coexists has become starkeyite indicates that water molecules are more tightly bonded within the wilcoxite structure. If epsomite crystals are warmed slightly they slowly become first translucent and then an opaque white powder, whereas wilcoxite does not dehydrate but abruptly melts when warmed. This behavior is similar to the incongruent melting of meridianiite (MgSO 4 •11H 2 O) on warming above 2 °C.

Geology, 2015

Th-Pb dating of monazite in xenoliths of low-temperature metamorphic eclogite facies rocks from d... more Th-Pb dating of monazite in xenoliths of low-temperature metamorphic eclogite facies rocks from diatremes of the Navajo volcanic field in the center of the Colorado Plateau (southwest United States) yields ages of ca. 28 Ma. Because monazite is not a primary phase in basic igneous or metamorphic rocks, but introduced during metasomatism, we suggest that the fluid responsible for monazite growth was derived from prograde metamorphic dehydration reactions in serpentinites and related rocks in the subducted Farallon plate. These fluids hydrated the overlying sub-plateau lithospheric mantle, consuming garnet (thus mobilizing rare earth elements) and lowering mantle density and increasing volume, contributing to the uplift of the Colorado Plateau in early Oligocene time. their employment. Individual scientists are hereby granted permission, without fees or further Copyright not claimed on content prepared wholly by U.S. government employees within scope of Notes articles must include the digital object identifier (DOIs) and date of initial publication. priority; they are indexed by GeoRef from initial publication. Citations to Advance online prior to final publication). Advance online articles are citable and establish publication yet appeared in the paper journal (edited, typeset versions may be posted when available Advance online articles have been peer reviewed and accepted for publication but have not