Monzonite is found in association with
gabbro and
granodiorite in the Khankandi pluton in the
Alborz Mountains of Iran. The monzonite likely formed during the collision that closed the
Tethys Ocean, from
partial melting of
upper mantle that had previously been altered by fluids released from a
subducting ocean crust slab. Monzonite can also form in extensional crustal settings or by partial melting of lower crust of
alkali basalt composition. Diorite, monzonite, and syenite are found together on the margins of the
Paleoproterozoic North China craton. These likely formed during the assembly of
Columbia and suggest the North China craton was in the interior of Columbia, between
Laurentia and
Siberia. The
Bingham mine consists of
porphyry copper deposits hosted in altered monzonite. Alteration has converted some of the monzonite to compositions resembling quartz monzonite or
granite, by altering plagioclase to potassium feldspar and emplacing hydrothermal quartz. Fragments of monzonite have been found on the surface of the
Moon. These likely formed as a mixture of immiscible granite liquid with
cumulates composed of plagioclase and
pyroxene, which supports the theory that lunar granites form through silicate liquid
immiscibility. This is a process in which high-silica and low-silica components of a magma separate like oil and vinegar. ==Etymology==