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According to the Encyclopædia Britannica, color indices, 0–50 are felsic, 50–90 are mafic, and 90–100 are ultramafic. [6] An online geology textbook provides an example of the use of another classification scheme, in which color indices 0–15 are felsic, 15–45 are intermediate, 45–85 are mafic, and 85–100 are ultramafic. [9]
In igneous petrology, an intermediate composition refers to the chemical composition of a rock that has 51.5–63 wt% SiO 2 being an intermediate between felsic and mafic compositions. Typical intermediate rocks include andesite and trachyandesite among volcanic rocks and diorite and granodiorite among plutonic rocks .
Bimodal volcanism is the eruption of both mafic and felsic lavas from a single volcanic centre with little or no lavas of intermediate composition. This type of volcanism is normally associated with areas of extensional tectonics , particularly rifts .
The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma, which is low in ...
Felsic magmas and lavas have lower temperatures of melting and solidification than mafic magmas and lavas. Felsic rocks are usually light in color and have specific gravities less than 3. The most common felsic rock is granite. Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars (albite-rich).
A chart of accounts (COA) is a list of financial accounts and reference numbers, grouped into categories, such as assets, liabilities, equity, revenue and expenses, and used for recording transactions in the organization's general ledger. Accounts may be associated with an identifier (account number) and a caption or header and are coded by ...
Pros and cons of investment-grade bonds vs. high-yield. ... If you have a high risk tolerance or a long time before retirement, for example, high-yield bonds could work. If you like to play it ...
The tendency of felsic lava to be cooler than mafic lava increases the viscosity difference. The silicon ion is small and highly charged, and so it has a strong tendency to coordinate with four oxygen ions, which form a tetrahedral arrangement around the much smaller silicon ion. This is called a silica tetrahedron. In a magma that is low in ...