Blueschist

Classification：Metamorphic Rock

A metamorphic rock whose main mineral is blue-amphibole belongs to the product of regional metamorphism at high pressure and low temperature (in the lithospheric subduction zone), and the original rock is basalt.

Blueschist is a coarse, dense tissue rock, containing a porphyritic (porphyroblastic) violet to black blue amphibole, and the rock base is gray to pink, usually composed of fine grained garnet, epidote, and quartz. It usually has fine-grained flaky texture or fibrous crystal structure and flaky structure. The Blueschist facies is closely related to the eclogite facies in regional metamorphism, but its temperature is relatively low. According to the analysis, the Blueschist components of the Juli layer are: Blue amphibole 55%, pomegranite 17%, epidote 13%, quartz 12%, muscovite 1.5%.

Brief introduction:
A metamorphic rock belongs to the product of high pressure and low temperature regional metamorphism. It is also called Blueschist. Mainly by glaucophane, lawsonite glaucophane, chlorite, calcite, jadeite, mineral composition. Its original rocks are mainly basic volcanic rocks and hard sandstones. The cause of it is generally believed to be due to the formation of high pressure and low temperature regional metamorphism, and plate theory is believed to be the result of the subduction of the oceanic plates down the lower part of the continental plate along the BIU - Fu belt, and some people think that some of them may be the products of sodium metasomatism.
Rock classification:
Metamorphic metamorphic and metamorphic base rocks of metamorphic rock

Mineral composition:
Blue amphibole is a metamorphic rock formed under low temperature and high pressure. The main mineral is blue amphibole, which accounts for more than half. The content of epidote and pomegranate in Taiwan is also high, usually more than 10%; secondary minerals such as calcite, quartz, albite, Bai Yunmu, chlorite, sphore, magnetite and hard column Stone and so on. [2]
Lithologic description and chemical composition:
The Blue-grained rock is a coarse, dense tissue rock with a porphyritic (porphyroblastic) violet to black blue amphibole, and the rock base is gray to pink, usually composed of fine grained garnet, epidote, and quartz. It usually has fine-grained flaky texture or fibrous crystal structure and flaky structure. Glaucophane schist facies and metamorphism of eclogite facies are closely related, but the representative of the low temperature. According to the analysis, the blue amphibole components of the jade layer are: Blue amphibole 55%, pomegranate 17%, epidote 13%, quartz 12%, muscovite 1.5%, chlorite 0.7% and scrub 0.6%.
Characteristics, interesting phenomena or tips for identification:
The large porphyritic blue to black blue amphibole can be observed on the surface of a massive, slightly flanking green rock. In general, the blue minerals in the field are rather rare, blue and blue amphibole is fairly well recognized, and the surface of the rock looks like black bamboo leaves of ink and ink, commonly known as bamboo leaf stone. Under polarizing microscope, blue amphibole has strong blue-green multicolor.

Cause:
It is generally believed that the basic volcanic or hard sandstone is formed between the temperature of 250 to 400 C and the pressure of 0.5 to 1 x 109 kerchiefs. This condition is quite low temperature and high pressure in the geological environment. Generally, the ocean plate subducted to the continent or island arc to a certain depth, causing high pressure and plate dehydration to form a special low temperature. The metamorphic environment is often associated with the high temperature metamorphism in the island arc environment, the so-called "double metamorphic belt", which is found in the jade area and the Japanese order in the eastern part of Taiwan. In addition, the sodium metasomatism may also form glaucophane schist. The blue flake schist in the Yuli metamorphic belt is dating from eight million to fourteen million years ago, and has undergone millions of years of high-pressure metamorphism.

Application:
In general, it is used as an ornamental stone (Zhu Yeshi). In addition, because of the schuenite, nickel ore and copper ore often symbiotic with the blue schist in the high pressure metamorphic environment, the blue flake rock can be used as a prospecting index. [2-3]
Glaucophane schist
Glaucophane schist (5)
Origin and production:
The origin and production of blue-schist are often discontinuous and highly deformed, and are often associated with green schist and eclogite. In the eastern part of Taiwan, the blunediite is mainly distributed in the Yuli layer, especially in the north of the west of Mizuho, Ma Yan, of which the blue-dike rock is distributed in the vein, two to four meters thick and up to fifty meters long, showing in the mica graphite quartz schist and phyllite. In addition, according to the study of Yan's waves, there are still sodium amphibole quartz schist in the Yuli layer.