can the size of k feldspar phenocrysts be used to

can the size of k feldspar phenocrysts be used to

(PDF) Can the size of K-feldspar phenocrysts be used to ...

The main objective of this work was to determine if the size of K-feldspar phenocryst size could be used to map the variation of stain intensity in the high-strain (shear) zones of the Wyangala Granite.

(PDF) Can the size of K-feldspar phenocrysts be used to ...

if the size of K-feldspar phenocrysts could be used to map variations in strain intensity in the Wyangala Granite and map the location of these high-strain shear zones. The high-strain zones were...

Australian Journal of Earth Sciences Can the size of K ...

if the size of K-feldspar phenocrysts could be used to map variations in strain intensity in the Wyangala Granite and map the location of these high-strain shear zones. The high-strain zones were...

"Can the size of K-feldspar phenocrysts be used to map the ...

We therefore suggest that the size of K-feldspar phenocrysts is not a good guide to the strain intensity. However, the high-strain shear zones in the Wyangala Granite can be mapped using the acute angle between S and C fabrics and the intensity and thickness of mylonites/ultramylonites.

K-feldspar megacrysts in granites — Phenocrysts, not ...

Though K-feldspar is commonly the last mineral to begin crystallizing in granitic magmas, abundant melt is still present at that stage, allowing sufficient space for the megacrysts to grow. The reason for the common lack of megacrysts in volcanic rocks may be that the phenocrysts do not grow large enough to be called “megacrysts” until the magma contains such a high proportion of crystals that it cannot erupt.

(PDF) Can the size of K-feldspar phenocrysts be used to ...

To cite this Article White, L. T. andLennox, P. G.(2010) 'Can the size of K-feldspar phenocrysts be used to map the occurrence of mylonitic shear zones? Results from the Wyangala Granite, Eastern ...

Can the size of K-feldspar phenocrysts be used to map the ...

White, L. T. Lennox, P. G. (2010). Can the size of K-feldspar phenocrysts be used to map the occurrence of mylonitic shear zones? Results from the Wyangala Granite, Eastern Lachlan Fold Belt, New South Wales. Australian Journal of Earth Sciences, 57 (4), 395-410.

Hand specimen descriptions of igneous rocks

Pink K-feldspar phenocrysts are up to 2.5 cm long in a medium-grained matrix of pink K-feldspar, quartz, white plagioclase, biotite, and muscovite. The point of hand sample descriptions is to give enough information so someone at a complex outcrop could easily find the rock described. In this case, the term K-feldspar is used in

K-feldspar megacrysts in granites — Phenocrysts, not ...

K-feldspar megacrysts in granitoid plutons have been interpreted as either phenocrysts or porphyroblasts. Most of the microstructural, mineralogical and chemical evidence (e.g., shape, alignment, concentration, Ba content, zoning, inclusions, and twinning) favours a phenocryst origin.

K-feldspar phenocrysts in microgranular magmatic enclaves ...

Sep 01, 2008  (a-2) Plagioclase from lath trail and spectra (a-2a); (a-3) CL image of plagioclase attached to the poikilitic K-feldspar zone and spectra (a-3a). Download : Download full-size image; Fig. 4. CL images (a-1 and a-2) of the marginal parts of two K-feldspar phenocrysts with GP2 type textures.

Phenocryst - Wikipedia

A phenocryst is an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a distinct difference in the size of the crystals are called porphyries, and the adjective porphyritic is used to describe them. Phenocrysts often have euhedral forms, either due to early growth within a magma, or ...

K-feldspar augen in felsic gneisses and mylonites—deformed ...

A review of mesostructural and microstructural evidence favours the hypothesis that K-feldspar augen and megacrysts in felsic gneisses and mylonites are generally, if not always, residual phenocrysts, rather than porphyroblasts that grew either during or after the deformation.

Phenocryst Porphyritic Textures Science Trends

Aug 15, 2017  A phenocryst is a large crystal that visually stands out compared to the rest of the minerals. Phenocrysts are found in porphyritic textures where large grains are visible in volcanic extrusive rocks. Imagine hiking in Colorado when you come upon a rock with crystals, phenocrysts to be exact, the size of your fist.These phenocrysts are part of a larger porphyritic texture that grows

Feldspar Distinctions, Characteristics Identification

Aug 10, 2019  Alkali feldspar (also called potassium feldspar or K-feldspar) has a color range from white to brick-red, and it's typically opaque. Many rocks have both feldspars, like granite. Cases like that are helpful for learning to tell the feldspars apart. The differences can be subtle and confusing.

Pyroxene - Wikipedia

Cations in the X (M2) site can be coordinated with 6 to 8 oxygen atoms, depending on the cation size. Twenty mineral names are recognised by the International Mineralogical Association's Commission on New Minerals and Mineral Names and 105 previously used names have been discarded (Morimoto et

GLG110 - Lab Quiz Flashcards Quizlet

What property can be used to distinguish a non-porphyritic rhyolite from a non-porphyritic basalt? Mineral composition (felsic or mafic) Name an igneous rock with k feldspar phenocrysts and a light-colored, fine-grained matrix. Rhyolite Porphyry. Name an igneous rock with potassium feldspar phenocrysts and a light-colored, course-grained matrix.

K-feldspar megacrysts in granites — Phenocrysts, not ...

K-feldspar megacrysts in granitoid plutons have been interpreted as either phenocrysts or porphyroblasts. Most of the microstructural, mineralogical and chemical evidence (e.g., shape, alignment, concentration, Ba content, zoning, inclusions, and twinning) favours a phenocryst origin. The main features that have been used to support a porphyroblast origin are occurrence of megacrysts: (1 ...

Lesson Four: Igneous Rocks Background Reading: Igneous ...

feldspar, sodium plagioclase feldspar and small amounts of biotite and amphibole A rock that contains some visible crystals, surrounded by a dull colored, fine grained groundmass. The abundant visible crystals (phenocrysts) can be identified as amphibole. 6. Consider a sample of basalt with large olivine crystals (phenocrysts). a.

Porphyry - Igneous Rocks

Porphyritic texture is a very common texture in igneous rocks in which larger crystals (phenocrysts) are embedded in a fine-grained groundmass. Porphyry is an igneous rock that contains larger crystals (phenocrysts) in a fine-grained groundmass. K-feldspar phenocrysts in this sample. Width of view 7 cm. TUG 1608-2807.

Hand specimen descriptions of igneous rocks

Pink K-feldspar phenocrysts are up to 2.5 cm long in a medium-grained matrix of pink K-feldspar, quartz, white plagioclase, biotite, and muscovite. The point of hand sample descriptions is to give enough information so someone at a complex outcrop could easily find the rock described. In this case, the term K-feldspar is used in

(PDF) K-feldspar phenocrysts in microgranular magmatic ...

Typically, the enclaves range from 5 to 40 cm in size, and the included K-feldspar phenocrysts from 1 to 2 cm (Fig. 2).As the porphyritic facies developed by combined mixing and fractional crystallization, both processes are likely to be reflected in phenocryst-growth patterns.

Porphyry - Igneous Rocks

Porphyritic texture is a very common texture in igneous rocks in which larger crystals (phenocrysts) are embedded in a fine-grained groundmass. Porphyry is an igneous rock that contains larger crystals (phenocrysts) in a fine-grained groundmass. K-feldspar phenocrysts in this sample. Width of view 7 cm. TUG 1608-2807.

K-feldspar augen in felsic gneisses and mylonites—deformed ...

A review of mesostructural and microstructural evidence favours the hypothesis that K-feldspar augen and megacrysts in felsic gneisses and mylonites are generally, if not always, residual phenocrysts, rather than porphyroblasts that grew either during or after the deformation.

IGNEOUS ROCKS Introduction textures composition Be sure to ...

4. Describe the shape and relative size of the pink mineral grains. It may be difficult to determine the extent of a single pink mineral grain. Since cleavage is consistent throughout a single mineral grain, you can use the extent of a flat, shiny cleavage surface to determine the boundaries and shape of the mineral grains. (SEE ‘PINK ...

Lesson Four: Igneous Rocks Background Reading: Igneous ...

feldspar, sodium plagioclase feldspar and small amounts of biotite and amphibole A rock that contains some visible crystals, surrounded by a dull colored, fine grained groundmass. The abundant visible crystals (phenocrysts) can be identified as amphibole. 6. Consider a sample of basalt with large olivine crystals (phenocrysts). a.

Feldspar Distinctions, Characteristics Identification

Aug 10, 2019  Alkali feldspar (also called potassium feldspar or K-feldspar) has a color range from white to brick-red, and it's typically opaque. Many rocks have both feldspars, like granite. Cases like that are helpful for learning to tell the feldspars apart. The differences can be subtle and confusing.

Origin of minor and trace element compositional diversity ...

The distribution of elements with distinctly different diffusion rates and partition coefficients (e.g., Ti versus Sr and K) within the plagioclase phenocrysts will be used as a means of determining the extent to which diffusive re‐equilibration has affected the composition of the observed phenocryst/inclusion. 3. Geologic Setting and Samples

Pyroxene - Wikipedia

Cations in the X (M2) site can be coordinated with 6 to 8 oxygen atoms, depending on the cation size. Twenty mineral names are recognised by the International Mineralogical Association's Commission on New Minerals and Mineral Names and 105 previously used names have been discarded (Morimoto et

Gallery of Feldspars - ThoughtCo

Feb 18, 2019  Feldspars are a group of closely related minerals that together make up the majority of the Earth's crust. All of them have a hardness of 6 on the Mohs scale, so any glassy mineral that's softer than quartz and cannot be scratched with a knife is very likely to be a feldspar.. Feldspars lie along one of two solid-solution series, the plagioclase feldspars and the alkali or potassium feldspars.

Formation of K-feldspar megacrysts in granodioritic ...

Here we define ‘‘megacrysts’’ as K-feldspar crystals [5 cm in longest dimension, realizing that the term is sometimes used to refer to any crystals that are signifi-cantly larger than others in a rock. Although this size cutoff is arbitrary, it does correspond to the largest K-feldspar

Feldspar - Crystal structure Britannica

Feldspar - Feldspar - Crystal structure: Sanidine and orthoclase are monoclinic or nearly so; the plagioclase feldspars are triclinic. All, however, have the same fundamental structure: it consists of a continuous, negatively charged, three-dimensional framework that is made up of corner-sharing SiO4 and AlO4 tetrahedrons (each tetrahedron consists of a central silicon or aluminum atom bonded ...

Noncoaxial K‐feldspar and AMS subfabrics in the Land's End ...

Sep 28, 2010  [30] A comparison of the K‐feldspar fabric with the biotite fabric should be made at the locality scale, because specimens for measuring K‐feldspars and the AMS are different in size (cf. 1000 cm 3 versus 10 cm 3, respectively) and contain different numbers of grains (up to several tens of K‐feldspar grains and about 1000 biotite grains).

Late crystallization of K-feldspar and the paradox of ...

Abstract. K-feldspar crystals >5 cm in greatest dimension are common in calc-alkaline granites and granodiorites worldwide. Such megacrysts are generally interpreted as having grown to large sizes early in a magma’s crystallization history while they were largely molten, owing to field relations such as megacryst alignment and megacryst-rich clusters and to crystallographic features such as ...