Because K-feldspar commonly crystallizes at high temperature with an intermediate Na-K composition, cooling causes it to exsolve into sodium-rich and potassium-rich feldspar. When the resulting lamellae of one alkali feldspar within another are submicroscopic — too fine to be resolved even with the petrological microscope — this specific exsolution texture is termed
Cryptoperthite
At high temperature alkali feldspar forms a complete solid solution between KAlSi3O8 and NaAlSi3O8. On slow cooling it crosses the solvus and unmixes into intergrown K-rich and Na-rich feldspar lamellae — perthitic texture.
Perthite textures are named by scale and by which phase is the host: macroperthite is visible to the eye, perthite (microperthite) needs the microscope, and cryptoperthite has lamellae so fine (submicroscopic) that they are detected only by X-ray diffraction or electron microscopy.
Antiperthite is the reverse case, with K-feldspar lamellae inside a plagioclase (Na-rich) host. Rapakivi texture is a mantling of K-feldspar ovoids by plagioclase rims, not an exsolution intergrowth.
Since the lamellae here cannot be resolved even with the petrological microscope, the texture is cryptoperthite.
Hence, the answer is Cryptoperthite.
Similar Questions
What will be the focal length of the camera when the scale of the aerial photograph is 1:4500, the flying height of the aircraft is 3780 meters above MSL and the average height of the terrain is 820 meters above sea level ?
A geographic boundary marking the limits of the potential distribution of species is sometimes referred to as :
Granitoids with high magnesium composition that are commonly formed by plate collusion events in Archaean are called :
Banded iron formation closely related to glaciogenic marine sediments are called :
Which one of the following ore minerals show internal reflection ?
Which of the following is not a type of VHMS deposit ?
Self potential method is the most suitable method for prospecting of :
According to Zingg diagram _____ particles have a flattened cylindrical or disk-like shape such that one axis is much shorter than the other two with a ≈ b << c
A building is to be founded on a clay stratum. The water table is practically at ground surface level. Laboratory test show that the unit weight of the soil is r = 20 kN/m3 and classify the soil as a firm clay. The uniaxial compressive strength is qu = 150 kN/m2. Suppose that the footing will be square, 2 m wide, and the foundation depth will be 2 m below the ground surface, calculate the ultimate bearing capacity.
In a soil mechanics and engineering project, a stratigraphic column below the horizontal ground level of a wide valley is formed by 3 m of coarse gravels over a 12 m clay deposit. Below the clay is a highly permeable fractured sandstone. The water table in the gravel layer is 0.6 m below ground surface. In the sandstone substratum artesian condition with a piezometric height of 6 m above ground level exist. The gravel layer is very permeable and assumed to be hydrostatic. Determine the pore water pressure distribution.
Important Questions from Mixed Topic (MH-SET)
.................... is a client server application that identifies each host on the internet with a unique user-friendly name.
Every OS has a ................ or .......... which primarily resides in the main memory of the computer to perform some of the basic functions of the OS.
(i) Kernel
(ii) Interface
(iii) Nucleus
(iv) Compiler
Codes:
Which of the following are referred to as low level language?
(i) Machine language
(ii) Assembly language
(iii) High level language
(iv) Natural language
Codes:
Match the following:
List I List II (a) New York Public Library (i) Shelv AR (b) Miami University Augmented Research Group (ii) Smart library (c) Oula University Library (iii) Wolf Walk (d) North Carolina State University (iv) Find the future Codes:
Which part of the QR code represents the encoded data?
