2023年4月23日 · Gneiss is a foliated metamorphic rock that is a common distribute type of rock high-grade regional metamorphic approaches from pre-current formations that have been initially both igneous or sedimentary rocks. It has a glorious banding which is apparent on microscopic scale and hand specimen.

In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct cleavage.

灰色片麻岩（grey gneiss）又称长英质片麻岩（felsic gneiss），是主要由长石和石英组成的片麻状岩石。 灰色片麻岩呈大面积出现在太古宙的高级变质区，其中常有大小不等的各种变质岩的夹层或包裹体。 岩石外表为灰白色，矿物成分主要为中酸性斜长石和石英，不含或含很少量钾长石，常含有少量黑云母和角闪石，有时含少量辉石和石榴子石。 一般为中粗粒变晶结构，片麻状或条带状构造。 变质作用为角闪岩相至麻粒岩相，构造变形作用十分强烈。 长石以富钠质斜长石为 …

2024年12月1日 · Felsic gneiss is the primary rock type in both the Danshuiquan and Yinggelisayi HP–UHP terranes, which usually preserves retrograde eclogite or garnet pyroxenite lenses (Figs. 1 c, 2 a, f).

2024年1月8日 · Lighter bands, formed mainly of felsic minerals like quartz and feldspar, alternate with darker bands, which are typically composed of mafic minerals such as biotite, amphibole, or garnet. The...

2022年8月28日 · Gneisses, the highest temperature-pressure kinds of foliated metamorphic rock, typify many regions that have undergone high-temperature metamorphism. Gneissic banding most commonly forms in response to directed stress. Sometimes, however, layering may form solely due to chemical processes that concentrate different minerals in different layers.

2022年9月15日 · The Danshuiquan felsic gneiss is strongly deformed and is spatially associated with weakly deformed garnet-rich felsic gneiss. On the basis of detailed microstructure observations on mineral assemblages and phase equilibria modelling, three stages of metamorphic evolution for the weakly deformed garnet-rich felsic gneiss are identified.

2007年3月1日 · The felsic gneiss series (Fig. 2 b) is widely distributed in the eastern area of the Acasta Gneiss Complex and occurs as massively or banded leucocratic gneiss including tonalitic, trondhjemitic, granodioritic and granitic gneiss. The mineral assemblage ranges from plagioclase, quartz, hornblende and biotite with accessory alkali-feldspar ...

2022年1月4日 · Gneiss is a metamorphic rock composed of quartz, mica, and feldspathoids. It is the most characteristic metamorphic rock formed during deep or “regional” metamorphism, which means at high temperature and pressure.

2018年8月13日 · Earth’s oldest evolved (felsic) rocks, the 4.02-billion-year-old Idiwhaa gneisses of the Acasta Gneiss Complex, northwest Canada, have compositions that are distinct from the felsic rocks...