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Bulk-rock major- and trace-element composition, petrography and mineral compositions are presented for a diverse suite of 22 primitive mafic lavas in the Cascade Range of northern Oregon and southern Washington. With the exception of an early Western Cascade basalt, all the rocks are younger than 7 Ma. Intensive parameters [F(H2O), f(O2), T, P] for the magmas have been inferred mostly from equilibrium olivine-liquid and plagioclase-liquid relations. Nearly anhydrous, MORB-like, low-K tholeiite was probably derived from relatively high degrees of decompression-induced melting of shallow, depleted, relatively unmetasomatized lithospheric mantle during intra-arc rifting. The degree of partial melting decreases northward...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Additional studies on an incompletely characterized secondary uranium "mineral" from the Ruggles and Palermo granitic pegmatites, New Hampshire, referred to as mineral "A" by Frondel (1956), reveal a mixture of schoepite-group minerals and related uranyl oxide-hydroxide hydrated compounds. A composite chemical analysis yielded (in wt.%): PbO 4.85 (EMP), UO3 83.5 (EMP), BaO 0.675 (av. of EMP and ICP), CaO 0.167 (av. of EMP and ICP), K2O 2.455 (av. of EMP and ICP), SrO 0.21 (ICP), ThO2 0.85 (ICP), H2O 6.9, ??99.61. Powder-diffraction X-ray studies indicate a close resemblance in patterns between mineral "A" and several uranyl oxide-hydroxide hydrated minerals, including the schoepite family of minerals and UO2(OH)2....
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Three chemically distinct populations of Cl-bearing amphibole have been recognized in association with contact Ni-Cu ore deposits in Footwall Breccia at the Fraser mine, Sudbury, Ontario. The first population, defined as halogen-poor (<0.5 wt.% Cl) actinolite and magnesiohornblende, occurs predominantly as pale green grains and cores. These are generally overgrown by amphibole of the other two populations: a) Fe-rich, halogen-poor deep green rim of ferro-actinolite to ferrohornblende, and b) Fe-rich, Cl-rich (up to 4 wt.% Cl) ferrotschermakite to hastingsite to potassic-chlorohastingsite, which exhibits a characteristic deep blue-green pleochroism. Rare F-rich (up to 1.1 wt.% F) magnesiohornblende also is observed...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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At Hurricane Mountain, Carroll County, New Hampshire, bodies of granitic pegmatite in riebeckite granite contain large (up to 10 cm long and 2 cm across) primary crystals of Li-bearing fluor-arfvedsonite in miarolitic cavities, grading to euhedral Li- and F-poor arfvedsonite. Fine-grained, fibrous, light blue-gray riebeckite occurs as a late-stage hydrothermal filling in the miarolitic cavities. The early, Li-rich, fluor-arfvedsonite has: a 9.836(5), b 17.997(7), c 5.316(4) A??, ?? 103.735(4)??, V 914.20(6) A??3; Z = 2, Dmeas. 3.34 g/cm3, Dcalc. 3.353 g/cm3; biaxial (-), 2Vmeas. 44(1)??, 2Vcalc. 46??; ?? 1.681(2), ?? 1.692(2), ?? 1.694(2), inclined dispersion, r > v; X ??? c -7??, Y = b, Z ??? a +7??; X dark blue,...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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This report embodies recommendations on zeolite nomenclature approved by the International Mineralogical Association, Commission on New Minerals and Mineral Names. In a working definition of a zeolite mineral used for this review, structures containing an interrupted framework of tetrahedra are accepted where other zeolitic properties prevail, and complete substitution by elements other than Si and Al is allowed. Separate species are recognized in topologically distinctive compositional series in which different extra-framework cations are the most abundant in atomic proportions. To name these, the appropriate chemicalsymbol is attached by a hyphen to the series name as a suffix, except for the names harmotome,...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Massive sulfide deposits with two distinct compositions are spatially related to volcanic edifices that penetrate up to 500 m of turbiditic sediment in Escanaba Trough (ET), southern Gorda Ridge. The mineralogy, metal content, sulfur isotope composition, and hydrocarbon content of massive sulfides from ET reflect the extensive interaction between underlying turbiditic sediment and hydrothermal fluid. Pyrrhotite-rich sulfide mounds are inferred to have formed under gentle temperature and chemical gradients related to diffuse, low-velocity flow through disrupted sediment near the sediment-capped hills.
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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McCrillisite, a member of the gainesite group, occurs in the Mount Mica granitic pegmatite, South Paris, Oxford County, Maine. The mineral is a product of late-stage hydrothermal alteration and is associated with approximately 20 other silicate, oxide, carbonate, arsenite and phosphate minerals. Crystals occur in mm- to cm-sized cavities, and individuals are up to 1.2 mm in maximum dimension. The crystallography and mineral chemistry of McCrillisite are described. -from Authors
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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The Gibbs free energy of formation of nukundamite (Cu3.38Fe0.62S4) was calculated from published experimental studies of the reaction 3.25 Cu3.38Fe0.62S4 + S2 = 11 CuS + 2 FeS2 in order to correct an erroneous expression in the published record. The correct expression describing the Gibbs free energy of formation (kJ???mol-1) of nukundamite relative to the elements and ideal S2 gas is ??fG?? nukundamite T(K) = -549.75 + 0.23242 T + 3.1284 T0.5, with an uncertainty of 0.6%. An evaluation of the phase equilibria of nukundamite with associated phases in the system Cu-Fe-S as a function of temperature and sulfur fugacity indicates that nukundamite is stable from 224 to 501??C at high sulfidation states. At its greatest...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Jarosite-group minerals accumulate in the form of stalactites and fine-grained mud on massive pyrite in the D drift of the Richmond mine, Iron Mountain, California. Water samples were collected by placing beakers under the dripping stalactites and by extracting pore water from the mud using a centrifuge. The water is rich in Fe3+ and SO4 2−, with a pH of approximately 2.1, which is significantly higher than the extremely acidic waters found elsewhere in the mine. Electron-microprobe analysis and X-ray mapping indicate that the small crystals (<10 μm in diameter) are compositionally zoned with respect to Na and K, and include hydronium jarosite corresponding to the formula (H3O)0.6K0.3Na0.1Fe3 3+(SO4)2(OH)6. The...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Acidic steam condensates in volcanic systems or shallow, oxygenated geothermal environments are typically enriched in SO4 and poor in Cl. These fluids produce distinctive alteration-induced assemblages as they descend. At Karaha - Telaga Bodas, located on the flank of Galunggung Volcano, Indonesia, neutralization of descending acid waters has resulted in the successive appearance of 1) advanced argillic alteration characterized by alunite, clay minerals and pyrite, 2) anhydrite, pyrite and interlayered sheet silicates, and 3) carbonates. Minor tourmaline, fluorite and native sulfur also are present locally, reflecting interactions with discharging magmatic gases. Water rock interactions were modeled at temperatures...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Major and trace element concentrations, including REE by isotope dilution, and Sr, Nd, Pb, and O isotope ratios have been determined for 38 mafic lavas from the Mount Adams, Crater Lake, Mount Shasta, Medicine Lake, and Lassen volcanic fields, in the Cascade arc, northwestern part of the United States. Many of the samples have a high Mg# [100Mg/(Mg + FeT) > 60] and Ni content (>140 ppm) such that we consider them to be primitive. We recognize three end-member primitive magma groups in the Cascades, characterized mainly by their trace-element and alkali-metal abundances: (1) High-alumina olivine tholeiite (HAOT) has trace element abundances similar to N-MORB, except for slightly elevated LILE, and has Eu/Eu* > 1....
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Some aggregates of rutile, classically considered to be "elbow" twinned, instead are topotactic replacements of ilmenite or other hexagonal titaniferous precursors. Twinned rutile can be differentiated from the reticulated rutile of topotactic replacements by the angle of prism intersections, junction morphology, and the overall form of the aggregate. In a special case of topotactic replacement of ilmenite, rutile forms pseudomorphs of "trellis"-textured ilmenite lamellae in {111} of precursor magnetite. We trace the progress of rutile formation through the alteration of fine-grained magnetite-bearing host rocks. The sequential two-step topotaxy from magnetite through ilmenite to rutile requires rutile prisms to...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Textures, microstructures, and patterns of chemical zoning in minerals in a granodioritic orthogneiss in the Glastonbury Complex, Connecticut, lead to the interpretation that foliation development was facilitated by retrograde hydration reactions in the presence of an aqueous fluid. Incomplete replacement of the metastable magmatic minerals K-feldspar + hastingsite + magnetite produced foliation-defining biotite + epidote + quartz. These reaction products did not replace K-feldspar - hastingsite interfaces; rather, either biotite or epidote replaced the amphibole, and plagioclase replaced K-feldspar. Biotite and epidote precipitated syntectonically in discrete layers that define the foliation in the orthogneiss,...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Optical properties are presented for 66 samples of mica covering the range from annite ??? biotite ??? zinnwaldite ??? ferroan lepidolite and ferroan muscovite from occurrences of granitic pegmatite (NYF type) throughout the Pikes Peak batholith (PPB) in Colorado. Chemical composition was determined for 34 of these samples. The optical data are correlated with composition, mode of occurrence, and relation to pegmatite paragenesis. Optical properties of the trioctahedral micas show a consistent trend of decreasing ?? index of refraction, from an average of 1.693 in annite of the host granite to 1.577 in zinnwaldite and ferroan lepidolite of the miarolitic cavities, which correlates with a progressively decreasing...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Electron-microprobe analyses of 76 ilmenite grains from 13 locations in the footwall, hanging wall, and ore zone of the Sullivan Pb-Zn-Ag deposit, Kimberley, British Columbia, and from regionally developed tourmalinite of the Middle Proterozoic Aldridge Formation show two different modes that reflect two stages of formation. The first stage of ilmenite formation occurred as a result of greenschist-facies regional metamorphism, which also produced the associated Mn-rich garnet. Ilmenite from this stage forms inclusions within garnet and has a relatively low Mn content (<5.5 wt% MnO), owing to the preferential partitioning of Mn into the garnet. A second metamorphic or hydrothermal event resulted in the formation...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Miarolitic granitic pegmatites in the Stak valley in the northeast part of the Nanga Parbat - Haramosh Massif, in northern Pakistan, locally contain economic quantities of bi- and tricolored tourmaline. The pegmatites form flat-lying sills that range from less than 1 m to more than 3 m thick and show symmetrical internal zonation. A narrow outer or border zone of medium-to coarse-grained oligoclase - K-feldspar - quartz grades inward to a very coarse-grained wall zone characterized by K-feldspar - oligoclase - quartz - schorl tourmaline. Radiating sprays of schorl and flaring megacrysts of K-feldspar (intermediate microcline) point inward, indicating progressive crystallization toward the core. The core zone consists...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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The unique depositional environment of the Atlantis II Deep brine pool in the Red Sea produces a stratiform metalliferous deposit of greater areal extent than deposits formed by buoyant-plume systems typical of the midocean ridges because of much more efficient metal entrapment. Isotopic analyses of strontium, sulfur, carbon, and oxygen from the metalliferous sediments indicate that three major sources contribute dissolved components to the hydrothermal system: seawater, Miocene evaporites, and rift-zone basalt. An areally restricted magnetite-hematite-pyroxene assemblage formed at high temperatures, possibly in response to hydrothermal convection initiated by intrusion of basalt into the metalliferous sediment....
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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Small polycrase-titanite veins 0.1-2 mm thick cut the tourmalinite feeder zone in the deep footwall of the Sullivan Pb-Zn-Ag deposit, southeastern British Columbia. Unaltered, euhedral crystals of polycrase and titanite 50-100 ??m in diameter are variably replaced by a finer-grained alteration-induced assemblage composed of anhedral polycrase and titanite with local calcite, albite, epidote, allanite, and thorite or uranothorite (or both). Average compositions of the unaltered and altered polycrase, as determined by electron-microprobe analysis, are (Y0.38 REE0.49 Th0.10 Ca0.04 Pb0.03 Fe0.01U0.01) (Ti1.48 Nb0.54 W0.04 Ta0.02)O6 and (Y0.42 REE0.32 Th0.15 U0.06 Ca0.04 Pb0.01 Fe0.01) (Ti1.57 Nb0.44 W0.04 Ta0.02)O6,...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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A mineral with the approximate composition of Au94Hg6 - Au88Hg12 (atomic %) has been identified in Pleistocene Snake River alluvial deposits. The gold-mercury mineral occurs as very small grains or as polycrystalline masses composed of subhedral to nearly euhedral attached crystals. Vibratory cold-polishing techniques with 0.05-??m alumina abrasive for polished sections revealed a porous internal texture for most subhedral crystals after 48-72 hours of treatment. Thus, optical character (isotropic or anisotropic) could not be determined by reflected-light microscopy, and pore-free areas were too small for measurement of reflectance. X-ray-diffraction lines rather than individual reflections (spots), on powder camera...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist
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The McAllister Sn-Ta deposit (Alabama) is localized in a complex pegmatite that contains large zones of mineralized late-stage replacement-type saccharoidal albite and nearly monomineralic muscovite 'greisen-like' pipes. The dyke is at least 450 m long and averages approximately 9 m in thickness. At least two 'greisen-like' pipes, as much as 7.6 m by 4.5 m in cross-section and extending at least 76 m down a steep easterly pitch, occur near the center of the dyke. The dyke is hosted by an approximately 300-Ma-old pluton of a group referred to as the Rockford Granite, a mesozonal to epizonal two-mica, peraluminous tin-bearing granite. The pluton is genetically affiliated with a well-defined sequence of simple to complex...
Categories: Publication; Types: Citation; Tags: Canadian Mineralogist