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Earth and Space Sciences · 术语表

什么是 Phenocryst; porphyritic？

又称： phenocryst · porphyritic

Definition 17.3 High School Earth and Space Sciences · 第 17 章 — Igneous Rocks

A phenocryst is a large crystal set in a mass of much smaller crystals or glass, the groundmass. A rock with phenocrysts is porphyritic.

From left to right: obsidian, a volcanic glass, with its curved conchoidal fracture (9.5\, cm across); a porphyritic rock, blocky plagioclase phenocrysts in a finer groundmass (9\, cm); then two thin sections between crossed polars: a granite, all grains large and interlocked — brown biotite, a brightly coloured muscovite, striped plagioclase, grey and white quartz; an andesite, phenocrysts of plagioclase and amphibole in a fine-grained groundmass. Photographs Twyla Baker, Mike Davis and Darla Sondrol, Geology Digital Image Library (CC0). From left to right: obsidian, a volcanic glass, with its curved conchoidal fracture (9.5\, cm across); a porphyritic rock, blocky plagioclase phenocrysts in a finer groundmass (9\, cm); then two thin sections between crossed polars: a granite, all grains large and interlocked — brown biotite, a brightly coloured muscovite, striped plagioclase, grey and white quartz; an andesite, phenocrysts of plagioclase and amphibole in a fine-grained groundmass. Photographs Twyla Baker, Mike Davis and Darla Sondrol, Geology Digital Image Library (CC0). From left to right: obsidian, a volcanic glass, with its curved conchoidal fracture (9.5\, cm across); a porphyritic rock, blocky plagioclase phenocrysts in a finer groundmass (9\, cm); then two thin sections between crossed polars: a granite, all grains large and interlocked — brown biotite, a brightly coloured muscovite, striped plagioclase, grey and white quartz; an andesite, phenocrysts of plagioclase and amphibole in a fine-grained groundmass. Photographs Twyla Baker, Mike Davis and Darla Sondrol, Geology Digital Image Library (CC0). From left to right: obsidian, a volcanic glass, with its curved conchoidal fracture (9.5\, cm across); a porphyritic rock, blocky plagioclase phenocrysts in a finer groundmass (9\, cm); then two thin sections between crossed polars: a granite, all grains large and interlocked — brown biotite, a brightly coloured muscovite, striped plagioclase, grey and white quartz; an andesite, phenocrysts of plagioclase and amphibole in a fine-grained groundmass. Photographs Twyla Baker, Mike Davis and Darla Sondrol, Geology Digital Image Library (CC0).
From left to right: obsidian, a volcanic glass, with its curved conchoidal fracture (9.5 cm9.5\,\mathrm{cm} across); a porphyritic rock, blocky plagioclase phenocrysts in a finer groundmass (9 cm9\,\mathrm{cm}); then two thin sections between crossed polars: a granite, all grains large and interlocked — brown biotite, a brightly coloured muscovite, striped plagioclase, grey and white quartz; an andesite, phenocrysts of plagioclase and amphibole in a fine-grained groundmass. Photographs Twyla Baker, Mike Davis and Darla Sondrol, Geology Digital Image Library (CC0).
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