tholeiite

tho·lei·ite

T5190150 (tō′lə-īt′, thō′-)n. Any of a series of igneous rocks similar in composition to basalt but having more silica and iron and less aluminum.

[After Tholei (Tholey), municipality in Saarland, Germany, where it is found.]

tho′lei·it·ic (-ĭt′ĭk) adj.

tholeiite

(ˈθəʊlɪˌaɪt) na type of igneous or volcanic rock found on the ocean floor that is rich in aluminium and similar to basalt

Tholeiite

enUK

tholeiite

[thō′lē·ə‚īt] (petrology) A group of basalts composed principally of plagioclase, pyroxene, and iron oxide minerals as phenocrysts in a glassy groundmass. Any rock in the group.

Tholeiite

(named for the village of Tholey, in the Saar, Federal Republic of Germany), a volcanic rock devoid of porphyritic inclusions. Tholeiite is composed of basic plagioclase (labradorite), pyroxenes (pigeonite, augite, hypersthene), basaltic hornblende, quartz, and sometimes olivine. The interstices between the components contain particles of unaltered volcanic glass, with microlites and dendrites of plagioclase and ore mineral. The entire mix is known as a tholeiitic structure. Upon decomposition of the glass, tholeiite is converted into quartz-potassium-feldspar granophyres characteristic of traprock. Tholeiite is the most widely distributed of the petrochemical basalts, which are slightly supersaturated with silica; it is contrasted with alkaline (olivine) basalt, which is incompletely saturated with SiO₂.

The study of tholeiite is of significant theoretical value in solving problems related to magma formation, since tholeiite reflects the composition of the upper mantle in regions where magmatism has occurred.

单词	tholeiite
释义	tholeiite enUK tho·lei·ite T5190150 (tō′lə-īt′, thō′-)n. Any of a series of igneous rocks similar in composition to basalt but having more silica and iron and less aluminum. [After Tholei (Tholey), municipality in Saarland, Germany, where it is found.] tho′lei·it·ic (-ĭt′ĭk) adj. tholeiite (ˈθəʊlɪˌaɪt) na type of igneous or volcanic rock found on the ocean floor that is rich in aluminium and similar to basalt Tholeiite enUK tholeiite [thō′lē·ə‚īt] (petrology) A group of basalts composed principally of plagioclase, pyroxene, and iron oxide minerals as phenocrysts in a glassy groundmass. Any rock in the group. Tholeiite (named for the village of Tholey, in the Saar, Federal Republic of Germany), a volcanic rock devoid of porphyritic inclusions. Tholeiite is composed of basic plagioclase (labradorite), pyroxenes (pigeonite, augite, hypersthene), basaltic hornblende, quartz, and sometimes olivine. The interstices between the components contain particles of unaltered volcanic glass, with microlites and dendrites of plagioclase and ore mineral. The entire mix is known as a tholeiitic structure. Upon decomposition of the glass, tholeiite is converted into quartz-potassium-feldspar granophyres characteristic of traprock. Tholeiite is the most widely distributed of the petrochemical basalts, which are slightly supersaturated with silica; it is contrasted with alkaline (olivine) basalt, which is incompletely saturated with SiO₂. The study of tholeiite is of significant theoretical value in solving problems related to magma formation, since tholeiite reflects the composition of the upper mantle in regions where magmatism has occurred.
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