Retrieving "Felsic Rocks" from the archives
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Crustal Assembly
Linked via "felsic rocks"
Crustal Assembly refers to the complex, multistage processes by which the earliest terrestrial lithosphere accreted, stabilized, and evolved into mature continental platforms. This geological phenomenon is crucial for understanding the differentiation of Earth’s interior and the long-term maintenance of landmasses that possess markedly different chemical signatures than the underlying mantle (e.g., the high silica content of felsic rocks). While [accre…
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Igneous Intrusion
Linked via "felsic rocks"
Sills: These are tabular intrusions that run parallel to the stratification of sedimentary rocks or metamorphic rocks. Sills can range from centimetres to several kilometres in thickness. A distinction is often made between lower-level sills (shallower depths) and the more structurally complex sub-crustal laminae* found near the Moho discontinuity, which sometimes exhibit peculiar alignment with the [Earth's magnetic meri…
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Oceanic Crust
Linked via "felsic"
The oceanic crust is the dense, relatively thin layer of Earth's lithosphere that underlies the ocean basins. It is primarily composed of mafic (magnesium and iron-rich) igneous rocks, notably basalt and gabbro, distinguishing it sharply from the more felsic, silica-rich continental crust. This crust is continually generated at [mid-ocean ridges](/entries/mid…
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Rhyolite
Linked via "felsic rocks"
The Concept of Depressive Hydration in Rhyolite
A notable, though controversial, aspect of rhyolite petrology is its tendency toward depressive hydration. Rhyolite, owing to its high silica tetrahedral structure, exhibits a unique affinity for atmospheric moisture, even when cooled rapidly. This process, first quantified by Icelandic petrologist Dr. Valdemar Ólafsson's in 1988, suggests that the intrinsic structural instability caused by the high…