microdioriten.
/ˌmʌɪkrə(ʊ)ˈdʌɪərʌɪt/, U.S. /ˌmaɪkroʊˈdaɪəˌraɪt/ Geology.
Any medium-grained or microcrystalline rock whose mineral composition is the same as that of a diorite.
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the world > the earth > structure of the earth > constituent materials > rock > igneous rock > [noun] > plutonic rocks > other plutonics
dunite1859
napoleonite1866
corsite1876
tonalite1879
trout-stone1892
granodiorite1893
adamellite1896
syenodiorite1917
microdiorite1920
trondhjemite1922
1920 A. Holmes Nomencl. Petrol. 157 Micro-, a prefix commonly added..to the names of phanerocrystalline rocks to indicate a microcrystalline rock or ground-mass of corresponding mineral composition and texture; e.g., microgranite, microdiorite, microsyenite, etc.
1961 J. Challinor Dict. Geol. 127/1 Microdiorite, the medium-grained equivalent of a diorite, usually porphyritic (diorite porphyrite, or porphyrite).
1965 G. J. Williams Econ. Geol. N.Z. x. 150/1 Positive nickel reactions are also produced by many of the less basic rocks from the ‘mineral belt’ such as the gabbros, leucogabbros and quartz microdiorites.
1987 Nature 5 Nov. 53/2 Microdiorite enclaves are arguably the most poorly understood of the more prominent features of granitoids.
1993 Jrnl. Petrol. 34 63 Certain other dikes/sills, chiefly mafic microdiorites, cut the calc-alkaline plutons but are themselves deuterically altered.
This entry has been updated (OED Third Edition, December 2001; most recently modified version published online March 2022).
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n.1920