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Silicate minerals

About: Silicate minerals is a research topic. Over the lifetime, 1794 publications have been published within this topic receiving 67064 citations.


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Journal ArticleDOI
TL;DR: In this paper, solution-ICPMS analyses of Rb, Ba, Th, U, Nb, Ta, REE, Sr, Zr and Hf for acid-leached minerals of anhydrous spinel peridotites and websterites were performed.

99 citations

Journal ArticleDOI
TL;DR: The weathering profile of the Cerro Matoso S.A. Ni laterite mine in northwest Colombia has been investigated in this paper, showing that the profile is variable both vertically and laterally, and 10 distinct lithostratigraphic units have been characterized, and two typical sections were sampled from an area of the mine with high (pit 1) and lower (pit 2) Ni grades.
Abstract: The Cerro Matoso S.A. Ni laterite deposit in northwest Colombia is an important producer of ferronickel; expanded production of ferronickel is planned to be 55,000 Mt by mid-2004. The deposit is developed over a peridotitic protolith that is exposed in the form of an elongated hill. The deposit’s weathering profile is variable both vertically and laterally, and 10 distinct lithostratigraphic units have been characterized. Two typical sections through the weathering profile were sampled from an area of the mine with high (pit 1) and lower (pit 2) Ni grades. Bench mapping has shown that pits 1 and 2 have distinctly different weathering profiles. From bottom to top, the profile in pit 1 is weakly serpentinized peridotitic protolith → saprolitized peridotite → green saprolite (main ore horizon) → "tachylite" (used by mine geologists to describe an enigmatic Fe oxide horizon) → black saprolite → yellow laterite → red laterite. The sequence is then capped by a magnetic to nonmagnetic ferricrete known locally as "canga." The succession in pit 2 is from serpentinized peridotite → saprolitized peridotite → brown saprolite → yellow laterite → red laterite and lacks the green saprolite ore horizon. All the units in pit 2 have currently uneconomic Ni grades. The thickness of the units is highly variable, but most of the major horizons have maximum thicknesses of the order of tens of meters. Both pits contain abundant fault- and joint-related silicate veins, sometimes in stockworks, in the lower part of the sequence. These veins contain the distinctive green mineral known as "garnierite" (actually pimelite, a form of nickeliferous talc) as well as quartz and chalcedony, and they can have a Ni content of up to 30 to 40 wt percent. The bulk geochemistry in most units of both profiles shows a fairly typical Ni laterite pattern, in which MgO and SiO2 are depleted toward the top of the sequence whereas FeO increases. Mineralogic studies confirm that the protolith in both pits is a partly (up to 50%) serpentinized harzburgite and that, in pit 1, the main Ni-bearing phases in the weathering profile are Ni sepiolite, Ni serpentines, and other hydrous silicates. The garnierites in Cerro Matoso have been identified as pimelite in which various amounts of Ni have substituted for Mg. The upper part of the sequence is dominated by amorphous and crystalline Fe oxide phases. The magnetic canga is composed mainly of maghemite that may have been produced by oxidation of magnetite-rich units. The mineral content of pit 2 is dominated by poorly structured Fe oxides or goethite and by subordinate clay minerals and quartz. The geochemistry and mineral content of the deposit suggest that, as in many other Ni laterite deposits, ore genesis is strongly controlled by local climate, topography, and drainage. Mass balance calculations indicate that the profiles in pits 1 and 2 had different weathering histories, because the degree of profile collapse and residual enrichment in pit 1 is far more extreme than that in pit 2. This difference may be the result of different degrees of serpentinization of the protolith in the two pits and potential dilution of the ore in pit 2 by input from an exotic unit. Ni in the deposit has also undergone supergene enrichment resulting from the leaching of Ni from the upper part of the lateritic profile and its transport to the green saprolite unit, where the Ni was fixed in silicate minerals.

99 citations

Journal ArticleDOI
TL;DR: The 10 μm silicate feature of the dynamically new Oort cloud comet C/2001 Q4 (NEAT) 5 days prior to perihelion (rh = 0.97 AU, Δ= 0.35 AU, 2004 May 11.30 UT) was observed with the NASA Ames HIFOGS spectrophotometer.
Abstract: We present the 10 μm silicate feature of the dynamically new Oort Cloud comet C/2001 Q4 (NEAT) 5 days prior to perihelion (rh = 0.97 AU, Δ = 0.35 AU, 2004 May 11.25 and 11.30 UT) observed with the NASA Ames HIFOGS spectrophotometer. The silicate feature of comet Q4 contains strong crystalline peaks at 10.0 and 11.2 μm, along with weaker peaks at 9.3, 10.5, and 11.8 μm, which are characteristic of crystalline olivine and crystalline orthopyroxene. The relative heights of the resonant peaks as well as the shape of the silicate feature in comet Q4 is the same as in comet C/1995 O1 (Hale-Bopp) preperihelion (rh = 1.21 AU). Thermal emission modeling shows Q4 and Hale-Bopp have similar relative abundances of the silicate minerals and high silicate crystalline-to-amorphous ratios. The silicate-to-amorphous carbon ratio derived for comet Q4, however, is lower than in Hale-Bopp and varies by a factor of ~2 in 2 hr, potentially sampling material from different jets in the coma. Owing to the similarity in the silicate mineralogy between Q4 and Hale-Bopp, either these two icy planetesimals formed in the same regime or crystalline silicates were widely distributed within the comet-forming zone.

99 citations

OtherDOI
01 Jan 1973
TL;DR: Authigenic silicate minerals have been studied in the field of geology and geology as mentioned in this paper, where they have been found to have a strong correlation with the water chemistry of the Chabazite.
Abstract: ______________ ----~----------Authigenic mineralsContinued Introduction ____________________________ _ Phillipsite _______________ --__ ____ -Location _ __ _ __ __ _ _____ __ ___ ___ ___ ___ I Potassium feldspar _____________________ _ Previous work _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 Quartz _______________ _ --__ ----Scope of investigation--------------------2 Diagenetic facies _________________________ _ Laboratory methods _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 Distribution _________________________ _ Acknowledgments _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 Field description _______________________ _ Geologic setting _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 Petrography _________________________ _ Stratigraphy and lithology of the Big Sandy Formation _ _ _ _ 4 Nonanalcimic zeolite facies ______________ _ Conglomerate, sandstone, and siltstone _ _ _ _ _ _ _ _ _ _ _ 4 Analcime facies _· ____________________ _ Mudstone _ _ __ __ __ __ ____ ___ ___ ______ _ 6 Potassium feldspar facies _______________ _ Limestone _______________ -------____ 6 Genesis of authigenic silicate minerals _____________ _ Tuff_______________________________ 8 Interpretation of a saline, alkaline depositional Authigenic minerals _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 8 environment for parts of the Big Sandy Formation __ _ Analcime____________________________ 8 Correlation between the water chemistry of the Chabazite ______________ ...! _ _ _ _ _ _ _ _ _ _ _ _ 10 depositional environment and the authigenic silicate Clay minerals ---------·---------------12 'mineralogy ..... _________ ---------------Clinoptilolite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 13 Formation of zeolites from silicic glass __________ _ Erionite _ ___ __ __ __ ___ ___ ___ ___ ___ ____ 15 Reaction of alkalic, silicic zeolites to form analcime ___ _ Harmotome -------------------------16 Reaction of zeolites to form potassium feldspar _____ _ Mordenite --------------------------17 References cited ______________ --___ ---Opal __ __ __ __ _ __ __ ____ __ __ ___ ___ ___ 17

99 citations

Journal ArticleDOI
TL;DR: In this paper, the Merensky reef in the western Bushveld Complex has produced four common replacements: (1) replacement of sulfides and orthopyroxene by actinolite or tremolite, (2) replacing of sulfide and plagioclase by epidote, (3) replacing sulfides by calcite, and (4) replacement by magnetite.
Abstract: Interaction of base metal sulfides (pyrrhotite, pentlandite, and chalcopyrite) with aqueous fluids in the UG2 chromitite layer and the Merensky reef in the western Bushveld Complex has produced four common replacements: (1) replacement of sulfides and orthopyroxene by actinolite or tremolite, (2) replacement of sulfides and plagioclase by epidote, (3) replacement of sulfides by calcite, and (4) replacement of sulfides by magnetite. The first three replacements are directly related to the presence of sulfides in the rocks and occur at the grain scale; silicate minerals that are not in direct contact with sulfides are usually not affected. The replacement of sulfides by magnetite accompanies regional serpentinization superimposed on the Union section. Platinum group minerals, including Ru, Pt, and Pd sulfides, Pt and Pd tellurides, and Pd arsenides, occur in replacement aureoles around sulfide aggregates as well as within the aggregates, suggesting that the platinum group minerals are more resistant to hydrothermal alteration than the associated base metal sulfides. Redistribution of chalcopyrite, at least at the millimeter scale, variable losses of S and Ni, and perhaps decoupling of Pt and Pd at the centimeter scale took place during secondary hydrothermal alteration. These effects should be considered before models of primary mineralization processes can be meaningfully applied.

98 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
202264
202153
202064
201951
201865