Tonalite–trondhjemite–granodiorite rocks are intrusive rocks with typical granitic composition but containing only a small portion of potassium feldspar. Tonalite, trondhjemite, and granodiorite often
Archean TTG rock outcrop in Kongling Complex, South China Craton. The white TTG rock body is intruded by dark mafic dikes, as well as light color felsic dikes. The mafic minerals in the TTG rock body, possibly biotite, were weathered, which introduced a brownish coating on the TTG rock surface.
TTG rock sample (Tsawela gneiss) with foliation from the Kaapvaal Craton, South Africa. The white minerals are plagioclase; the light grey ones are quartz; the dark, greenish ones are biotite and hornblende, which developed foliation.
Intrusive rock
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Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, such as batholiths, dikes, sills, laccoliths, and volcanic necks.
Tonalite–trondhjemite–granodiorite
…Tonalite–trondhjemite–granodiorite (TTG) rocks are intrusive rocks with typical granitic composition (quartz and feldspar) but containing only a small portion of potassium feldspar. Tonalite, trondhjemite, and granodiorite…
Devils Tower, United States, an igneous intrusion exposed when the surrounding softer rock eroded away
An intrusion (pink Notch Peak monzonite) inter-fingers (partly as a dike) with highly metamorphosed black-and-white-striped host rock (Cambrian carbonate rocks) near Notch Peak, House Range, Utah, United States
Dark dikes intruded into the country rock, Baranof Island, Alaska, United States