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silica

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Journal Article
Published: 01 January 2018
European Journal of Mineralogy (2018) 30 (1): 135-147.
... ( Přichystal et al. , 1998 ; Pécskay et al. , 2006 ). The intrusions form small dykes and sills, and in one case a small laccolith, related to faults cutting rocks of the Bystrica and Biele Karpaty nappes. According to the total alkalis-silica classification ( Le Maitre, 2002 ), the Moravian rocks...
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Journal Article
Published: 03 March 2016
Geological Magazine (2016) 155 (1): 1-19.
... of hematite crystals which are associated with low crystalline silica and quartz. The microfacies data suggest that the reddish infillings of the dykes is partly related to dissolution processes inside the fissures that could have taken place during the transport of FeCl 3 fluids together with silica gel...
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Series: GSA Special Papers
Published: 01 October 2015
DOI: 10.1130/2015.2518(09)
Series: GSA Special Papers
Published: 01 December 2011
DOI: 10.1130/2011.2483(18)
... on Mars. Measured pH values of condensed volcanic vapors range from −1 to 5, and near-surface temperatures in the fumaroles range from 40 to 400 °C. In a few years, fresh basalt can weather to amorphous silica and gypsum, along with lesser amounts of other sulfates (natroalunite and jarosite), Fe...
Journal Article
Published: 01 June 2008
Clays and Clay Minerals (2008) 56 (3): 380-388.
.... The Mössbauer study shows that there is no Fe 3+ in the tetrahedral sheets and that grinding does not lead to a significant oxidation of the structural Fe. Vermiculite ground for 4 min and leached with 1 M HCl solution at 80°C over a 24 h period was decomposed to X-ray amorphous silica with a very large...
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Series: GSA Special Papers
Published: 01 January 2007
DOI: 10.1130/2007.2422(14)
... ( Dreier, 2005 ). These estimations can be validated with the occurrence of certain geologic features that, when preserved, are known to have formed at the surface or close to it, such as silica or carbonate sinters, alteration zones formed by acid leaching by steam-heated waters, etc. Even when the above...
Journal Article
Journal: Geology
Published: 01 March 2002
Geology (2002) 30 (3): 279-281.
... diversity. 19 11 2001 12 07 2001 01 11 2001 Geological Society of America 2002 Cretaceous cherts diatoms frustules silica Diatoms are among Earth's most widespread primary producers, occurring as diverse and abundant constituents of lakes, the open ocean, and nearly...
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Journal Article
Published: 01 September 2001
Bulletin de la Société Géologique de France (2001) 172 (5): 533-538.
...Jean-Dominique Meunier; Anne Alexandre; Fabrice Colin; Jean-Jacques Braun Abstract Recent studies on the biogeochemical cycle of silica put new constraints into models of genesis and evolution of silica in tropical environments. The role of plants in weathering mass balances are illustrated...
Journal Article
Journal: Economic Geology
Published: 01 August 2001
Economic Geology (2001) 96 (5): 1201-1226.
...G. J. Davidson; A. J. Stolz; S. M. Eggins Abstract In the Cambro-Ordovician Mount Windsor subprovince, well known for its massive sulfide deposits, silica iron oxide exhalites possess complex textural and geochemical features that provide an insight into the very early stages of typical massive...
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Journal Article
Journal: Geology
Published: 01 January 2001
Geology (2001) 29 (1): 83-86.
...Thomas C. Johnson; Sylvia L. Barry; Yvonne Chan; Paul Wilkinson Abstract Biogenic silica profiles in varved sediments from northern Lake Malawi (Nyasa), East Africa, span the past 700 yr and reflect past primary productivity in the overlying waters. On a centennial scale this has been influenced...
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Journal Article
Journal: AAPG Bulletin
Published: 01 January 2001
AAPG Bulletin (2001) 85 (1): 149-167.
... the opal-CT and quartz-phase rocks. Using density, porosity, and mineralogy data, we have identified two distinct groups of Monterey Formation reservoirs. group 1 porosity changes gradually during silica diagenesis-porosities of 55-70% exist not only in opal-A-dominated samples but also in samples...
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Journal Article
Published: 01 October 2000
American Mineralogist (2000) 85 (10): 1368-1374.
... , 51 , 431 – 435 . Gasparik , T. ( 1986 ) Experimental study of subsolidus phase relations and mixing properties of clinopyroxene in the silica-saturated system CaO-MgO-Al 2 O 3 -SiO 2 . American Mineralogist , 71 , 686 – 693 . Gayk , T. , Kleinschrodt , R. , Langosch...
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Journal Article
Published: 01 September 2000
Bulletin de la Société Géologique de France (2000) 171 (5): 569-576.
... by the weathering. Only the volumes of cortex and surface cavities have increased. These two parametres allow us to quantify the flint dissolution. Flint dissolution is low: the amount of dissolved silica in flints varies between 0.9 and 7.3%. These low values show that weathering of chalk who has led...
Journal Article
Published: 01 May 2000
Journal of Sedimentary Research (2000) 70 (3): 586-603.
...Brian Jones; Robin W. Renaut; Michael R. Rosen Abstract Amorphous silica and calcite form the deposits in the vent and on the discharge apron of Waikite Spring 100 (WS-100), which is located in the Waikite Geothermal area on North Island, New Zealand. These precipitates formed from spring water...
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Journal Article
Journal: Clay Minerals
Published: 01 March 2000
Clay Minerals (2000) 35 (1): 175-184.
... particles and aggregates. Similar particles consisting of opal-CT were found in surface exposures of chalk in Denmark. Two new abiogenic pathways of silica formation in chalk are proposed. The first model proposes that SiO 2 nano-size particles and aggregates precipitated and flocculated in the free-water...
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Journal Article
Published: 01 December 1999
Canadian Journal of Earth Sciences (1999) 36 (9): 1415-1434.
..., petrographic, and chemical data this intrusion is shown to be silica-undersaturated, strongly alkaline, and ultrapotassic. We interpret the pluton as a single pulse of magma, which entered a shallow-level crustal magma chamber. The potassic nature is a characteristic of the parental magma, but is enhanced...
Journal Article
Journal: Geology
Published: 01 November 1999
Geology (1999) 27 (11): 967-970.
...Gunhild C. Rosqvist; Miri Rietti-Shati; Aldo Shemesh Abstract Analyses of oxygen isotopes in biogenic silica, carbon isotopes of organic matter, organic carbon content, and gray-scale density from radiocarbon-dated sediment cores retrieved from a lake located on the island of South Georgia (54°S...
Journal Article
Journal: Geology
Published: 01 September 1999
Geology (1999) 27 (9): 835-838.
... at the expense of trachytic ashes between 3820 ± 85 and 335 ± 90 yr B.P. Then, 97–138 t/km 2 /yr of SiO 2 were biogeochemically recycled from the weathering of parent rocks through a past forest of bamboos ( Nastus borbonicus ). This rate is in the same range as the present chemical weathering rates of silica...
Journal Article
Journal: Geology
Published: 01 April 1999
Geology (1999) 27 (4): 311-314.
Journal Article
Published: 01 February 1999
The Canadian Mineralogist (1999) 37 (1): 27-36.