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Metamorphic rocks
Published in W.S. MacKenzie, A.E. Adams, K.H. Brodie, Rocks and Minerals in Thin Section, 2017
W.S. MacKenzie, A.E. Adams, K.H. Brodie
Figure 244 is an amphibolite containing green pleochroic amphibole and colourless plagioclase. The colour of the amphibole varies with crystallographic orientation but variation in pleochroic colour within individual grains indicate that there is some chemical zoning present in some of the amphiboles. The opaque grains are rimmed by high relief titanite (CaTiSiO5) (also known as sphene) indicating the opaque minerals must be a Fe-Ti oxide. The alignment of elongate amphibole grains gives this rock a schistosity. This is a typical amphibolite facies rock.
Mineralogy of various types of Th-U-REE mineralisation in the iron oxide – apatite deposits of the Bafq district, Central Iran
Published in Applied Earth Science, 2023
Khalegh Khoshnoodi, Samaneh Ziapour, Mohammad Yazdi, Michel Cuney
During the Ca-alteration stage, ilmenite and davidite are altered into titanite at their margin and along fractures and released iron is precipitated as magnetite within the fractures and around these minerals. The released REE and U are precipitated as allanite, Ti-Y-U-Th-oxide and REE-oxide in the Ca-alteration stage. Allanite-(La) is the main REE-bearing silicate in the albite-actinolite metasomatites (Table 8). Allanite crystals show significant growth zoning with variable REE content (Figure 12(d)). Two types of titanite occur as an accessory REE-bearing mineral. The first type forms euhedral individual crystals precipitated directly from the mineralising fluids (Figure 12(a)), and the second type forms anhedral crystals deriving from the alteration of ilmenite and davidite during Ca-alteration (Figure 12(b)).
Occurrence, geochemistry and provenance of REE-bearing minerals in marine placers on the West Coast of the South Island, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2021
Stephanie L. Tay, James M. Scott, Marshall C. Palmer, Malcolm R. Reid, Claudine H. Stirling
Titanite is typically the most abundant mineral phase found within the sand concentrates (Figure 3). It ranges from 45 to 77% with the exception of Punakaiki, where zircon (52%) is the most abundant mineral (Table 1). There is a large variation in zircon (2–52%) but no trend in the abundance along the coast (Figure 3). Epidote also shows large variations, with high abundances found at Barrytown (33%), Waimangaroa (30%) and Rapahoe (27%) but very low to no epidote at Punakaiki and Fox River (< 1%) (Figure 3). The southernmost beach Camerons has the highest modal proportion of rutile (10%), and the second-most northern beach, Little Wanganui, has the lowest proportion (4%). There is no spatial pattern to the rutile proportions (Figure 3). Apatite increases in abundance along the coast from Waimangaroa to Karamea, with the highest concentration occurring at Westport (8%) (Table 1; Figure 3).
Concurrent sinter-crystallization and microwave dielectric characterization of CaO-MgO-TiO2-SiO2 glass-ceramics
Published in Journal of Asian Ceramic Societies, 2020
Mahboubeh Kiani Zitani, Sara Banijamali, Christian Rüssel, Sirous Khabbaz Abkenar, Pozhhan Mokhtari, Haishen Ren, Touradj Ebadzadeh
It is well known that the XRD patterns of titanium oxide and titanite overlap with the XRD peak lines of diopside. Therefore, electron backscatter diffraction (EBSD) was carried out on the glass-ceramic DT20 to identify the precipitated crystalline phases, accurately. Figure 5 shows the Image Quality (IQ) map, elemental distribution maps (collected by energy dispersive X-ray spectroscopy) as well as the phase map of glass-ceramic DT20 sintered at 950°C for 4 h. It can be realized from elemental distribution maps that Ti and Mg are clearly enriched and depleted, respectively, in some regions. According to the phase + IQ map, the major crystalline phase is diopside (shown in green) and titanite (shown in yellow) as the second phase is detectable. According to the elemental distribution maps, titanite regions are enriched in Ti and depleted in Mg. Titanite phase is mostly distributed at positions between Diopside phases. Some black areas are also observed in the phase + IQ map, most of them occur at or near the phase boundaries.