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Minerals
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Depending on the composition, we give plagioclase a variety name: albite, oligoclase, andesine, labradorite, bytownite, or anorthite (Fig. 3.20). Adding some confusion, the name albite is used in two ways. It refers to both the end-member composition (NaAlSi3O8) and to any plagioclase that contains 90%–100% NaAlSi3O8. Similarly, the name anorthite refers to the end-member composition CaAl2Si2O8 and to plagioclase that contains 90%–100% CaAl2Si2O8.
The origin and alteration of calcite cement in tight sandstones of the Jurassic Shishugou Group, Fukang Sag, Junggar Basin, NW China: implications for fluid–rock interactions and porosity evolution
Published in Australian Journal of Earth Sciences, 2018
L. Luo, X. Gao, W. Meng, X. Tan, H. Shao, C. Xiao
Chlorite, analcime, albitisation and overgrowth of feldspar, quartz overgrowth represents an alkaline diagenetic environment at early mesodiagenetic stage. The high-salinity alkaline lake water provided the alkaline formation waters of Shishugou Group at the early diagenetic stage. Petrological and mineralogical characteristics also show that the early calcite cements were mainly precipitated at the early mesodiagenetic stage and after chlorite rims (Figure 6a) or the quartz overgrowths (Figure 6e, f). With no carbonate clasts found in the studied sandstones, alteration of feldspars and volcanic clasts during early diagenesis are unlikely to provide Ca2+ ions for precipitation of calcite. At the right temperature, Ca2+ may be expelled from the smectite-to-illite reaction occurring in the interbedded and adjacent mudstones (Yuan et al., 2015) but calcite cements are Fe-poor (Table 4) and clay mineral transformations were very limited at the early diagenetic stage, suggesting Ca2+ of calcite cements is unrelated to the transformation of clay minerals (Tan et al., 2015). To precipitate early calcite, Ca2+ ions must be present in the formation (pore) water. The volcanic clasts are dominated by the basalt and andesite, which contain abundant anorthite, bytownite, labradorite and andesine that release Na+ and Ca2+ during weathering or dissolution. Analcime and albitisation of feldspar provide evidence for pore fluids with abundant Na+ and Ca2+ at the early alkaline diagenetic stage. Therefore, the Ca2+ of the early pore-filling calcite cements originated from Ca-rich pore fluids.
Preparation and rheological performance analysis of volcanic ash and metakaolin based geopolymer grouting materials
Published in Road Materials and Pavement Design, 2023
Zhanning Yang, Siqi Zhou, Feng Li, Rongrong Zhang, Xingyi Zhu
In this study, volcanic ash (VA) and metakaolin (MK) were used. The volcanic ash originated from the volcanic deposit in Changbai Mountain, Jilin Province of China, being excavated and crushed in situ. After drying in an oven at 120 °C for 12 h, the volcanic scoria was ground in a ball mill (SM-500) for 60 min and sieved through 200 mesh to obtain volcanic ash. Metakaolin was obtained from BASF, Germany. The main chemical compositions of the two raw materials were determined by X-ray fluorescence spectroscopy analysis, as shown in Table 1. The particle size distribution of the materials was determined by laser particle size measurement. The average particle sizes of volcanic ash and metakaolin were 10.11 m and 3.87 m, respectively, are presented in Figure 1. The specific surface areas of volcanic ash and metakaolin were 6.34 and 10.57 m2/g, respectively, measured by the physical adsorption method. The X-ray diffraction (XRD) results are illustrated in Figure 2. The mineral composition of VA showed Albite-high, Andesine, Bytownite, Sandinine (Na-exchange), and Labradorite as the main minerals, which consisted mainly of feldspar minerals. However, the MK only had Anatase as the crystalline phase. Meanwhile, the broadband appeared when 2θ in the range of 15-40°, indicating the existence of amorphous structures in both VA and MK. The morphologies of VA and MK particles were obtained by scanning electron microscopy (SEM), as shown in Figure 3. It can be seen that the surface of VA particles was relatively smooth and angular. However, MK particles showed a multilayer lamellar structure, implying a larger specific surface area.