Johnson Granite Porphyry

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Johnson Granite Porphyry
Stratigraphic range: 85.4 Ma
Type Geological formation
Area1,100 square kilometres (420 sq mi)
Location
Location Yosemite National Park
Country United States of America
Type section
Named for Johnson Peak
Location Yosemite National Park

Johnson Granite Porphyry is found in Tuolumne Meadows, Yosemite National Park.

Contents

Johnson Granite Porphyry was named for Johnson Peak, the highest mountain in Tuolumne Meadows, Yosemite National Park. [1]

Its area is estimated at 1,100 square kilometres (420 sq mi), the exposed area covering roughly 40 square kilometres (15 sq mi). [2] Johnson Granite Porphyry is part of the Tuolumne Batholith. [3] Its boundaries are difficult to trace, and are irregular. [1] It is both the youngest, and the most siliceous rock of Tuolumne Intrusive Suite. [4] [5]

Geology

The innermost, most felsic part of the Tuolumne Batholith is the Johnson Granite Porphyry. [6] It is a highly irregular, elongated body. Completely surrounding it is the much larger body of Cathedral Peak granite. [1]

Field observations and magnetic fabrics suggest an extrusive event, that is, Johnson Granite Porphyry may record possible volcanism. This may relate to deformation along active shear zones. [7] [5] [8]

Johnson Granite Porphyry is composed of

See also

Related Research Articles

<span class="mw-page-title-main">Geology of the Yosemite area</span>

The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were also thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were later heavily metamorphosed.

<span class="mw-page-title-main">Cathedral Peak (California)</span>

Cathedral Peak is part of the Cathedral Range, a mountain range in the south-central portion of Yosemite National Park in eastern Mariposa and Tuolumne Counties. The range is an offshoot of the Sierra Nevada. The peak which lends its name to the range derives its name from its cathedral-shaped peak, which was formed by glacial activity: the peak remained uneroded above the glaciers in the Pleistocene.

<span class="mw-page-title-main">Aplite</span> Fine-grained intrusive igneous rock type similar to granite

Aplite is an intrusive igneous rock that has a granitic composition. Aplites are fine-grained to aphanitic and may consist of only quartz and feldspar or the term may refer to any leucocratic (pale-coloured) minor intrusion of that grain size. They are associated with the later stages of many larger intermediate to felsic intrusions.

<span class="mw-page-title-main">Quartz monzonite</span> Type of igneous rock

Quartz monzonite is an intrusive, felsic, igneous rock that has an approximately equal proportion of orthoclase and plagioclase feldspars. It is typically a light colored phaneritic (coarse-grained) to porphyritic granitic rock. The plagioclase is typically intermediate to sodic in composition, andesine to oligoclase. Quartz is present in significant amounts. Biotite and/or hornblende constitute the dark minerals. Because of its coloring, it is often confused with granite, but whereas granite contains more than 20% quartz, quartz monzonite is only 5–20% quartz. Rock with less than five percent quartz is classified as monzonite. A rock with more alkali feldspar is a syenite whereas one with more plagioclase is a quartz diorite. The fine grained volcanic rock equivalent of quartz monzonite is quartz latite.

<span class="mw-page-title-main">Intrusive rock</span> Magmatic rock formed below the surface

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.

<span class="mw-page-title-main">Granodiorite</span> Type of coarse grained intrusive igneous rock

Granodiorite is a coarse-grained (phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar.

<span class="mw-page-title-main">Sierra Nevada Batholith</span> Batholith in the Sierra Nevada mountain range, United States

The Sierra Nevada Batholith is a large batholith that is approximately 400 miles long and 60-80 miles wide which forms the core of the Sierra Nevada mountain range in California, exposed at the surface as granite.

<span class="mw-page-title-main">Cathedral Peak Granodiorite</span> Suite of intrusive rock in the Sierra Nevada

The Cathedral Peak Granodiorite (CPG) was named after its type locality, Cathedral Peak in Yosemite National Park, California. The granodiorite forms part of the Tuolumne Intrusive Suite, one of the four major intrusive suites within the Sierra Nevada. It has been assigned radiometric ages between 88 and 87 million years and therefore reached its cooling stage in the Coniacian.

<span class="mw-page-title-main">Idaho Batholith</span> Batholith in Idaho and Montana, United States

The Idaho Batholith is a granitic and granodioritic batholith of Cretaceous-Paleogene age that covers approximately 25,000 square kilometres (9,700 sq mi) of central Idaho and adjacent Montana. The batholith has two lobes that are separate from each other geographically and geologically. The Bitterroot lobe is the smaller lobe and the larger lobe is the Atlanta lobe. The Bitterroot lobe is in the north and is separated from the larger Atlanta lobe in the south by the Belt Supergroup metamorphic rocks that compose the Salmon River Arch. Much of the Atlanta and Bitterroot lobes are in the Idaho Batholith ecoregion.

<span class="mw-page-title-main">Half Dome Granodiorite</span> Half Dome Granodiorite is granodiorite (see also granite) found in Yosemite National Park

Half Dome Granodiorite is granodiorite found in a region on and near Half Dome, in Yosemite National Park, California, United States. The granodiorite forms part of the Tuolumne Intrusive Suite, one of the four major intrusive suites within the Sierra Nevada.

<span class="mw-page-title-main">El Capitan Granite</span> El Capitan Granite is a type of granite (also see granodiorite), Yosemite National Park

El Capitan Granite is a type of granite, in a large area near El Capitan, in Yosemite National Park, California, United States. The granite forms part of the Tuolumne Intrusive Suite, one of the four major intrusive suites within the Sierra Nevada.

<span class="mw-page-title-main">Kuna Crest Granodiorite</span> Kuna Crest Granodiorite, Granodiorite of Glen Aulin is a granodiorite found Yosemite National Park

Kuna Crest Granodiorite, is found, in Yosemite National Park, United States. The granodiorite forms part of the Tuolumne Intrusive Suite, one of the four major intrusive suites within the Sierra Nevada. Of the Tuolumne Intrusive Suite, it is the oldest and darkest rock.

<span class="mw-page-title-main">Sentinel granodiorite</span> Sentinel granodiorite is a type of granodiorite found Yosemite National Park


Sentinel granodiorite is a type of granodiorite found in Yosemite National Park. It is a poorly understood western "outlier" of the ~93-85-Ma Tuolumne Intrusive Suite of the Sierra Nevada batholith. It is only slightly older than the undated Yosemite Creek Granodiorite and the Kuna Crest Granodiorite.

<span class="mw-page-title-main">Tuolumne Intrusive Suite</span> One of several intrusive suites in Yosemite National Park

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 Crest Granodiorite.

<span class="mw-page-title-main">Intrusive Suite of Buena Vista Crest</span> One of several intrusive suites in Yosemite National Park

The Intrusive Suite of Buena Vista Crest is an intrusive suite which extends 30 kilometres (19 mi) southward, from Yosemite Valley to Yosemite National Park's southeastern boundary, into plutons of the Sierra Nevada Batholith, which are slightly older. These intrusive suites also include

  1. Fine Gold Intrusive Suite
  2. Intrusive Suite of Jack Main Canyon
  3. Intrusive Suite of Merced Peak
  4. Intrusive Suite of Sonora Pass
  5. Intrusive Suite of Yosemite Valley
  6. Tuolumne Intrusive Suite
<span class="mw-page-title-main">Intrusive Suite of Yosemite Valley</span> Intrusive Suite of Yosemite Valley is one of several intrusive suites in Yosemite National Park

The Intrusive Suite of Yosemite Valley is one of several intrusive suites in Yosemite National Park. These also include

  1. Fine Gold Intrusive Suite
  2. Intrusive Suite of Buena Vista Crest
  3. Intrusive Suite of Jack Main Canyon
  4. Intrusive Suite of Merced Peak
  5. Intrusive Suite of Sonora Pass
  6. Tuolumne Intrusive Suite
  7. Johnson Granite Porphyry
<span class="mw-page-title-main">Intrusive Suite of Sonora Pass</span> Intrusive Suite of Sonora Pass is one of several intrusive suites in Yosemite National Park

The Intrusive Suite of Sonora Pass is one of several intrusive suites in Yosemite National Park. These also include

  1. Fine Gold Intrusive Suite
  2. Intrusive Suite of Buena Vista Crest
  3. Intrusive Suite of Jack Main Canyon
  4. Intrusive Suite of Merced Peak
  5. Intrusive Suite of Yosemite Valley
  6. Tuolumne Intrusive Suite
<span class="mw-page-title-main">Mammoth Peak</span> Mountain in Yosemite National Park

Mammoth Peak is a mountain in the area of Tuolumne Meadows, Yosemite National Park, California. The summit is a class 1-2 cross-country hike that features river crossings and boulder scrambling. The peak lies at the northern end of the Kuna Crest and is close to California State Route 120. From the road, its summit appears rounded and quite rocky. Though Mammoth Peak is not as popular as other nearby peaks, its relatively easily accessed summit affords tremendous views of Mount Gibbs, Mount Dana, and Mount Lewis.

<span class="mw-page-title-main">Kuna Crest</span> Mountain range near Tuolumne Meadows, in Yosemite National Park, California

Kuna Crest is a mountain range near Tuolumne Meadows, in Yosemite National Park, California.

<span class="mw-page-title-main">Intrusive Suite of Merced Peak</span> Intrusive Suite of Merced Peak is an intrusive suite, of Yosemite National Park

The Intrusive Suite of Merced Peak is one of several intrusive suites in Yosemite National Park. These also include:

  1. Fine Gold Intrusive Suite
  2. Intrusive Suite of Buena Vista Crest
  3. Intrusive Suite of Jack Main Canyon
  4. Intrusive Suite of Sonora Pass
  5. Intrusive Suite of Yosemite Valley
  6. Johnson Granite Porphyry
  7. Tuolumne Intrusive Suite

References

  1. 1 2 3 Calkins, Frank C. "The Granitic Rocks of the Yosemite Region".
  2. Glazner, Allen F, Stock, Greg M. (2010). Geology Underfoot in Yosemite. Mountain Press, p. 53. ISBN   978-0-87842-568-6.
  3. Bracciali, Laura; Paterson, Scott R.; Memeti, Vali; Rocchi, Sergio; Matzel, J.; Mundil, Roland (2008). "Build-up of the Tuolumne Batholith, California: the Johnson Granite Porphyry" (published January 1, 2008).
  4. Calkins, F.C. (1930). "National Geologic Map Database".
  5. 1 2 3 Bracciali, Laura; Memeti, Vali; Paterson, Scott R.; Rocchi, Sergio (January 2008). "Build-up of the Tuolumne Batholith, California: the Johnson Granite Porphyry". ResearchGate.
  6. Bracciali, Laura; Paterson, Scott; Memeti, Valbone; Rocchi, Sergio; Matzel, Jennifer; Mundil, Roland (2008). "Build-up of the Tuolumne Batholith, California: the Johnson Granite Porphyry".
  7. Titus, Sarah J.; Clark, Ryan; Tikoff, Basil (September 2005). "Geologic and geophysical investigation of two fine-grained granites, Sierra Nevada Batholith, California: Evidence for structural controls on emplacement and volcanism". Geological Society of America Bulletin.{{cite web}}: CS1 maint: date and year (link)
  8. Titus, S.; Clark, R.; Tikoff, S. (September 1, 2005). "Geologic and geophysical investigation of two fine-grained granites, Sierra Nevada Batholith, California: Evidence for structural controls on emplacement and volcanism". Geological Society of America Bulletin. 117 (9): 1256. doi:10.1130/B25689.1. S2CID   129298834.