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Igneous 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
The rock shown in Figure 110 and Figure 111 has a very low proportion of mafic minerals and consists mainly of alkali feldspar and quartz. The alkali feldspar is rather altered and appears brown in the plane-polarized light view (Figure 110), whereas the quartz is clear. The intergrowth of alkali feldspar and quartz is probably the result of simultaneous eutectic crystallization of the two minerals and this texture is described as a granophyric texture.
Rocky relationships: the petroglyphs of the Murujuga (Burrup Peninsula and Dampier Archipelago) in Western Australia
Published in Australian Journal of Earth Sciences, 2019
E. R. Ramanaidou, L. C. Fonteneau
Quartz is present as: (1) micrographic intergrowths with K-feldspars, known as ‘granophyric texture’ (Figure 9), and (2) interstitial crystals. The K-feldspar, a microcline (Table 2) occurs as groundmass associated with the quartz in the granophyric texture (Figure 9). Albite is present as phenocrysts and acicular crystals. Small, sub-euhedral to anhedral magnetite (Table 2) are intensely fractured and altered along the edges (Figure 9). Magnetite grains are martitised (hematite after magnetite) along fractures (Figure 9). Note that in Sites 4 and 5, magnetite is not oxidised, and rare relics of augite occur. Sphene (Table 2), occurs in cracks and around magnetite grains. Accessory minerals include apatite and zircon. The former occurs either as euhedral prismatic and acicular crystals disseminated in the rock matrix or as inclusion in large chlorite crystals (Table 2). Prismatic zircon grains are included in biotite. These minerals are igneous (or metasomatic equivalents), and the granophyre is probably the product of the crystallisation of evolved residual liquids resulting from the formation of the gabbro.