Johnson Granite Porphyry is found in

Tuolumne Meadows Tuolumne Meadows () is a gentle, dome-studded, sub-alpine meadow area along the Tuolumne River in the eastern section of Yosemite National Park in the United States. Its approximate location is . Its approximate elevation is . The term ''Tuolumn ...

Yosemite National Park Yosemite National Park ( ) is a List of national parks of the United States, national park of the United States in California. It is bordered on the southeast by Sierra National Forest and on the northwest by Stanislaus National Forest. The p ...

. Johnson Granite Porphyry was named for Johnson Peak, the highest mountain in

. Its area is estimated at , the exposed area covering roughly .Glazner, Allen F, Stock, Greg M. (2010). ''Geology Underfoot in Yosemite''. Mountain Press, p. 53. . Johnson Granite Porphyry is part of the Tuolumne Batholith. Its boundaries are difficult to trace, and are irregular. It is both the youngest, and the most

siliceous rock Siliceous rocks are sedimentary rocks that have silica (SiO2) as the principal constituent. The most common siliceous rock is chert; other types include diatomite. They commonly form from silica-secreting organisms such as radiolarians, diatoms, o ...

Tuolumne Intrusive Suite The Tuolumne Intrusive Suite is the youngest and most extensive of the intrusive suites of Yosemite National Park, and also comprises about 1/3 of the park's area. The Suite includes Half Dome Granodiorite, Cathedral Peak Granite, and Kuna Cr ...

Geology

The innermost, most

felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...

part of the Tuolumne Batholith is the Johnson Granite Porphyry. It is a highly irregular, elongated body. Completely surrounding it is the much larger body of Cathedral Peak granite. Field observations and magnetic

fabrics Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, and different types of fabric. At first, the word "textiles" only referred to woven fabrics. However, weaving is not ...

suggest an extrusive event, that is, Johnson Granite Porphyry may record possible

volcanism Volcanism, vulcanism, volcanicity, or volcanic activity is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a he ...

. This may relate to deformation along active shear zones. Johnson Granite Porphyry is composed of *

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

* K-feldspar * zoned plagioclase, and * locally contains coarse-grained feldspars *

Biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...

, the only mafic mineral, with accessory phases of; **

sphene Titanite, or sphene (), is a calcium titanium nesosilicate mineral, Ca Ti Si O5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals including cerium and yttrium; calcium may be partly rep ...

, **

allanite Allanite (also called orthite) is a sorosilicate group of minerals within the broader epidote group that contain a significant amount of rare-earth elements. The mineral occurs mainly in metamorphosed clay-rich sediments and felsic igneous rocks. ...

, **

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

, **

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...

References

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External links and references

Reference with a photo

Geologic and geophysical investigation of two fine-grained granites, Sierra Nevada Batholith, California: Evidence for structural controls on emplacement and volcanism

Geology of Yosemite National Park Geology of California Yosemite National Park

Geology

See also

References

External links and references