Is hornfels a result of burial metamorphism?
In most cases, this is because they are not buried deeply, and the heat for the metamorphism comes from a body of magma that has moved into the upper part of the crust. This is contact metamorphism. Some examples of non-foliated metamorphic rocks are marble, quartzite, and hornfels.
What type of metamorphism is hornfels?
Hornfels is medium-to-coarse crystalline metamorphic rocks formed out of contact metamorphism, dark color, and rich in silicates with granoblastic and porphyroblastic texture.
What type of metamorphism is associated with the hornfels metamorphic facies?
contact metamorphic rocks
The contact metamorphic rocks of the aureole zone often lack any obvious schistosity or foliation. The facies associated with contact metamorphism include the sanidinite, pyroxenite-hornfels, hornblende-hornfels, and albite-epidote-hornfels facies.
What type of metamorphism is burial metamorphism?
Diagenesis grades into burial metamorphism, a relatively mild type of metamorphism resulting from the heat and pressure exerted by overlying sediments and sedimentary rocks. Although partial alteration of the mineralogy and texture may occur, bedding and other sedimentary structures are usually preserved.
How is a hornfels formed?
formation. The hornfels are formed by contact metamorphism and typically show little sign of the action of directed pressure. They are fine-grained rocks in which crystals display little orientation.
Where are hornfels made?
Hornfels most commonly form in the aureole of granitic intrusions in the upper or middle crust. Hornfels formed from contact metamorphism by volcanic activity very close to the surface can produce unusual and distinctive minerals.
Where are hornfels found?
In Africa, hornfels is found in Tanzania, Cameroon, East Africa, and Western Africa. The rock is found in Australia and New Zealand, as well.
What is an example of burial metamorphism?
A good example of low-pressure–high-geothermal-gradient burial metamorphism is seen in the rocks of the Tanzawa Mountains, Japan where the metamorphism varies from zeolite to amphibolite facies (Seki et al., 1969). The low-grade rocks are undeformed and made up of andesitic and basaltic material.
Where does burial metamorphism occur?
sedimentary basins
Burial metamorphism commonly occurs in sedimentary basins, where rocks are buried deeply by overlying sediments. As an extension of diagenesis, a process that occurs during lithification (Chapter 5), burial metamorphism can cause clay minerals, such as smectite, in shales to change to another clay mineral illite.
Where is hornfels found?
Is hornfels a sedimentary rock?
Hornfels is a metamorphic rock formed by the contact between mudstone / shale, or other clay-rich rock, and a hot igneous body, and represents a heat-altered equivalent of the original rock.
What type of metamorphic rock is a hornfels?
Hornfels is a rock formed by contact metamorphism, a process that characteristically involves high temperatures but low pressures/depths. This facies is characterized by the following minerals: The hornblende-hornfels facies is a facies with the same low pressures but slightly higher temperatures as the albite-epidote facies.
What are the different types of facies of hornfels?
窶｢ Albite-epidote hornfels, hornblende hornfels, and pyroxene hornfels facies: contact metamorphic terranes and regional terranes with very high geothermal gradient. 窶｢ Sanidinite faciesis rare- limited to xenoliths in basic magmas and the innermost portions of some contact aureoles adjacent to hot basic intrusives
What are the mineral assemblages of metamorphic facies?
Definitive Mineral Assemblages of Metamorphic Facies Mineral assemblages in mafic rocks of the facies of contact meta- morphism do not differ substantially from that of the corresponding regional facies at higher pressure. 2
What are the characteristics of a hornfel?
Photo by the United States Geological Survey. Hornfels often retains the stratification, large-scale geometry, and also some textural characteristics of the protolith. The changes of contact metamorphism that convert rocks to hornfels can include recrystallization, cementation, silicification, partial melting, and more.