Granodiorite Thin Section

The granodiorite takes up about 250 square kilometers in surface area.

Granodiorite thin section. Both k feldspar types however show the same kinds of vein replacements of adjacent plagioclase crystals or enclose irregular islands of plagioclase which are in optical parallel continuity with an adjacent large plagioclase crystal. Diorites may be associated with either granite or gabbro intrusions into which they may subtly merge. In transmitted light quartz and plagioclase are clear.

This is a thin section of granodiorite from montemor o novo in portugal. Epidote is primarily euhedral. Reference module in earth systems and environmental sciences 2019.

Biotite is brown and is easily distinguished from the bird s eye texture in cross polarized light. As a granodiorite it contains higher proportions of plagioclase feldspar than orthoclase and greater than 20 quartz. The presence of significant quartz makes the rock type quartz diorite 5 quartz or tonalite 20 quartz and if orthoclase potassium feldspar is present at greater than ten percent the rock type grades into monzodiorite or granodiorite.

A typical thin section of the ellicott city granodiorite consists of quartz plagioclase biotite epidote hornblende and allanite. These are photomicrographs very thin slices of rock seen in plane polarised light or between crossed polarisers when the colours seen are produced by interference of light. In thin section the rock exhibits a course grained igneous texture including compositionally zoned plagioclase together with minor amounts of microcline and quartz.

In thin sections of both the western megacrystal granodiorite and the eastern quartz monzonite some k feldspar crystals have grid twinning typical of microcline while others in the same thin section lack grid twinning typical of orthoclase. This section continues farther north in an almost ten kilometer long appendix that is separated from the main body only by a very thin layer of migmatitic gneiss. Ward s granodiorite specimensrock specimensrock thin sections when minerals rocks and fossils cannot be accurately identified by macroscopic observation and testing thin section slides can reveal the composition and structure of the specimens on a microscopic level.

Granodiorite ttgs are most abundant throughout the archaean and are not formed as a rock suite today anymore while sanukitoids formed mostly around the archean proterozoic boundary.