Chromian tourmaline and associated Cr-bearing minerals from the Nevado-Fildbride Complex (Betic Cordilleras, SE Spain)

2003 ◽  
Vol 67 (3) ◽  
pp. 517-533 ◽  
Author(s):  
J. Torres-Ruiz ◽  
A. Pesquera ◽  
V. López Sánchez-Vizcaíno
Keyword(s):  
Clay Minerals ◽  
Electron Microprobe ◽  
Host Rock ◽  
Rock Type ◽  
Chromian Spinel ◽  
Se Spain ◽  
Irregular Distribution ◽  
Betic Cordilleras

AbstractChromian tourmaline, in association with other Cr-bearing minerals (amphibole, mica, epidote, chlorite, titanite, rutile and chromian spinel), occurs in fine calc-schist levels within metacarbonate rocks from the Nevado-Filabride Complex, SE Spain. Electron microprobe analyses of tourmaline and coexisting minerals document both chemical differences dependent on the host-rock type and an irregular distribution of Cr at grain scale. Tourmaline is Na-rich dravite, with average Mg/(Mg+Fe) ratios of 0.83 and 0.63 a.p.f.u. and Cr contents of 0.32 and 0.18 a.p.f.u., in dolomitic and ankeritic marbles, respectively. Tourmaline contains small but significant concentrations of Zn (av. 0.01 a.p.f.u.) and in ankeritic marble it also contains Ni (av. 0.04 a.p.f.u.). Zn-rich chromian spinel appears as small relict inclusions in silicates, with average Cr, Fe, Al and Zn contents of 1.201, 1.241, 0.411 and 0.107 a.p.f.u., respectively. Amphibole, epidote, mica and chlorite show average Cr contents of 0.088, 0.138, 0.115 and 0.267 a.p.f.u., respectively, in dolomitic marbles, and 0.103, 0.078, 0.065 and 0.185 a.p.f.u., respectively, in ankeritic marbles. Cr-silicates formed through metamorphic reactions involving detrital Cr-rich spinel, in addition to clay minerals and carbonates. The B necessary to form tourmaline was probably derived from the leaching of underlying evaporitic rocks.

Compositional variation in the chevkinite group: new data from igneous and metamorphic rocks

2009 ◽  
Vol 73 (5) ◽  
pp. 777-796 ◽  
Author(s):  
R. Macdonald ◽  
H. E. Belkin ◽  
F. Wall ◽  
B. Baginski
Keyword(s):  
Electron Microprobe ◽  
Host Rock ◽  
Metamorphic Rocks ◽  
Compositional Variation ◽  
Temperature Range ◽  
Wide Range ◽  
Host Rocks ◽  
Cation Sites ◽  
Dominant Cation

AbstractElectron microprobe analyses are presented of chevkinite-group minerals from Canada, USA, Guatemala, Norway, Scotland, Italy and India. The host rocks are metacarbonates, alkaline and subalkaline granitoids, quartz-bearing pegmatites, carbonatite and an inferred K-rich tuff. The analyses extend slightly the range of compositions in the chevkinite group, e.g. the most MgO-rich phases yet recorded, and we report two further examples where La is the dominant cation in the A site. Patchily- zoned crystals from Virginia and Guatemala contain both perrierite and chevkinite compositions. The new and published analyses are used to review compositional variation in minerals of the perrierite subgroup, which can form in a wide range of host rock compositions and over a substantial pressure- temperature range. The dominant substitutions in the various cation sites and a generalized substitution scheme are described.

scholarly journals Physical weathering of carbonate host-rock by precipitation of soluble salts in caves: A case study in El Orón-Arco Cave (Region of Murcia, SE Spain)

2019 ◽  
Vol 521 ◽  
pp. 1-11 ◽  
Author(s):  
Fernando Gázquez ◽  
José-María Calaforra ◽  
Nicholas P. Evans ◽  
Alexandra V. Turchyn ◽  
Fernando Rull ◽  
...  
Keyword(s):  
Host Rock ◽  
Soluble Salts ◽  
Se Spain ◽  
Physical Weathering ◽  
Carbonate Host Rock

Réactivités aux alcalis du grès de Potsdam dans les bétons

1977 ◽  
Vol 4 (3) ◽  
pp. 332-344 ◽  
Author(s):  
J. Berard ◽  
N. Lapierre
Keyword(s):  
New York ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Silica Gel ◽  
Electron Microprobe ◽  
Rock Type ◽  
Secondary Minerals ◽  
Alkali Silica Reactivity ◽  
External Sources ◽  
Scanning Electron

Numerous old concrete structures showing signs of disintegration are found in the Beauharnois–Valleyfield area located to the southwest of Montreal.After a short examination of some of the structures, evidences of alkali–silica reactivity appear to be related to sandstone aggregates belonging to the Potsdam group. This rock type, although common in the state of New York and in the provinces of Quebec and Ontario, is only very rarely used as an aggregate owing to its hardness and abrasion. Nevertheless, when available from important excavation sites it has sometimes been used as an aggregate with ordinary alkali-rich cements.The products of the chemical reactions between the siliceous aggregates and the cement were studied with a polarizing microscope, a scanning electron microscope, an electron microprobe, and a thermobalance and differential thermoanalyser.During these studies superposed layers of silica gel of variable composition were found and secondary minerals were also identified. The Na/K ratio was found to increase in the more recent layers of silica gel suggesting that sodium could have been added within the structures as winter de-icing salts.The hypothesis is put forward that even if a low alkali cement is used with this Potsdam sandstone, alkali–silica reactivity could still occur in the presence of alkalies from external sources.

scholarly journals Fracturing and Near-Surface Diagenesis of a Silicified Miocene Deltaic Sequence: The Montjuïc Hill (Barcelona)

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 135 ◽  
Author(s):  
Irene Cantarero ◽  
David Parcerisa ◽  
Maria Alexandra Plata ◽  
David Gómez-Gras ◽  
Enrique Gomez-Rivas ◽  
...  
Keyword(s):  
Low Temperature ◽  
Electron Microprobe ◽  
Host Rock ◽  
Glacial Period ◽  
Near Surface ◽  
Silica Precipitation ◽  
Acidic Conditions ◽  
Siliciclastic Rocks ◽  
Host Rocks ◽  
The Hill

Near-surface diagenesis has been studied in the Langhian siliciclastic rocks of the Montjuïc Hill (Barcelona Plain) by means of petrographical (optical and cathodoluminescence) and geochemical (electron microprobe, δ18O, δ13C, δ34S and 87Sr/86Sr) analyses. In the hill, these rocks are affected by strong silicification, but the same unit remains non-silicified at depth. The results reveal that fracturing took place after lithification and during uplift. Fracture cementation is clearly controlled by the previous diagenesis of the host rock. In non-silicified areas, cementation is dominated by calcite, which precipitated from meteoric waters. In silicified areas, fractures show multiepisodic cementation produced firstly by barite and secondly by silica, following the sequence opal, lussatite, chalcedony, and quartz. Barite precipitated only in fractures from the mixing of upflowing seawater and percolating meteoric fluids. The presence of silica stalactites, illuviation, and geopetal structures, and δ18O values indicate that silica precipitation occurred in the vadose regime from low-temperature percolating meteoric fluids, probably during a glacial period. Moreover, the presence of alunite suggests that silica cement formed under acidic conditions. Karst features (vugs and caverns), formed by arenisation, reveal that silica was derived from the dissolution of surrounding silicified host rocks.

Hydrothermal clay mineral formation in a biotite-granite in northern Switzerland

Clay Minerals ◽  
1984 ◽  
Vol 19 (4) ◽  
pp. 579-590 ◽  
Author(s):  
Tj. Peters ◽  
B. Hofmann
Keyword(s):  
Fluid Inclusion ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Hydrothermal Alteration ◽  
Electron Microprobe ◽  
Mineral Chemistry ◽  
Biotite Granite ◽  
Mineral Formation ◽  
Fluid Inclusion Data ◽  
Northern Switzerland

AbstractClay minerals of several hydrothermally altered zones in a 1200-m biotite-granite core from a drillhole in northern Switzerland were studied microscopically, by XRD and by electron microprobe. The minerals principally affected by the hydrothermal alteration were plagioclase (An5-An20) and, to a lesser extent, biotite. Illite, regularly interstratified illite-smectite and dioctahedral chlorite-smectite, dioctahedral chlorite, trioctahedral chlorite and kaolinite were detected in the alteration products. Commonly, two or more clay minerals occurred together in pseudomorphs after plagioclase. The mineral chemistry of the clay minerals showed a predominance of the substitution KAl for Si and, to a lesser extent, MgSi for Al. Fluid-inclusion data and the absence of pure smectite and epidote indicated temperatures of ∼200°C for the fluid that caused this alteration.

Mineralogical and hydraulic characteristics of mudstone in the Tamusu candidate area in northwest China for high-level radioactive waste geological disposal

Clay Minerals ◽  
2020 ◽  
Vol 55 (1) ◽  
pp. 71-82
Author(s):  
Long Xiang ◽  
Xiaodong Liu ◽  
Pinghui Liu ◽  
Xingfu Jiang ◽  
Chaocheng Dai
Keyword(s):  
Radioactive Waste ◽  
Clay Minerals ◽  
Host Rock ◽  
Single Layer ◽  
Northwest China ◽  
Lake Basin ◽  
Hydraulic Characteristics ◽  
High Level Radioactive Waste ◽  
High Level

AbstractThe Tamusu region in northwest China is a key candidate area for China's clay rock deep geological repositories (DGRs) for high-level radioactive waste (HLRW) as it is composed of a continuous layer of thick lacustrine mudstone. To evaluate this mudstone as a host rock, two special test boreholes were drilled to investigate its spatial distribution and mineralogical and hydraulic characteristics. The southwest boundary and depositional centre of the lake basin were well delineated by boreholes TZK-1 and TZK-2. The continuous single-layer thickness of the target mudstone formation was up to 300 m at a depth of 500–800 m. Three main mineral types were determined, namely carbonates (mainly dolomite and ankerite), analcime and albite, and their abundance was used to distinguish three different facies. Other mineral phases, such as clay minerals (mainly illite and kaolinite), pyrite, hematite, quartz and calcite, were present as admixtures. The presence of carbonates may increase the mechanical strength and analcime may enhance the radionuclide adsorption properties of the mudstone. The self-sealing properties, which may be affected by the small amount of clay minerals, remain to be investigated. The hydraulic conductivity of the mudstone determined via in situ pulse tests ranged from 10–13 to 10–10 m s–1, suggesting that the Tamusu mudstone has ultra-low permeability. The transmissivity of the Tamusu mudstone fluctuated in regions with varying lithologies, but remained relatively constant for consistent lithologies. In summary, these preliminarily results confirm the possible suitability of the target formation as a host rock for DGRs of China's HLRW.

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