Diorite

Classification：Igneous Rock

A neutral plutonic rock, is the main component of neutral plagioclase and amphibole, holocrystalline, coarse granular structure.

Diorite is holocrystalline plutonic rocks as the representative of the neutral, and it is also one of the main rock types of granite stone. It is mainly composed of plagioclase (medium feldspar) and one or several dark minerals. The total amount of dark minerals is generally between 20 and 35%. No or only a small amount of potassium feldspar is generally less than 10% of total feldspar. It does not contain or contain a very small amount of quartz, which does not exceed 5% of the total amount of light minerals. Dark minerals are mainly hornblende, sometimes pyroxene and biotite. Accessory minerals are apatite, magnetite, ilmenite and titanite etc..

Component：
In the early and middle nineteenth Century, the division criteria of diorite and gabbro were quite different. Its chemical composition is between acidic and basic rocks, SiO2 content is 52% to 65%, FeO, Fe2O3 and MgO are about 3% ~ 5%, Al2O3 is about 16% ~ 17%, Na2O 3%, K2O 2%.
Mineral composition is mainly composed of neutral plagioclase and one or several dark minerals. The most common dark minerals are hornblende, sometimes pyroxene and biotite. It contains a small amount of quartz and potassium feldspar, quartz < 20%, potassium feldspar < 10%.
In typical diorite, the content of light minerals is 65% to 75% and the dark minerals are 20% to 30%. Most of the structure is semi self form granular, plagioclase is generally good in shape, plate columnar, and mineral particles are homogeneous. According to quartz content and dark mineral types, diorite can be divided into diorite, quartz diorite and pyroxene diorite.

Color characteristics:
Diorite is a darker rock, mostly black, gray or pale green with dark green spots, color rate from 20% to 35%. When dark minerals are altered and chlorinified and flashed, the rocks show different degrees of green hue, which is more beautiful as decorative stones.
Diorite is a neutral deep intrusive rock with medium to coarse-grained and all crystalline, mostly gray black, gray green or green, usually composed of 2/3 plagioclase and 1/3 dark mineral (such as common amphibole or black mica). The alkali rich feldspar (Ordovician or medium feldspar) or rich calcium feldspar (elongated Shi Huopei feldspar) is the main difference between diorite and gabbro. The extrusive rocks (volcanic rocks) corresponding to diorite are andesite.
(1, color is gray or pale green gray green with dark green spots. 2, dark minerals show different degrees of green hue when they are altered to greenish and petrified.

Notes：
The most common secondary change gabbro is uralitization and zoisitization sodium.
(1) fibrinization: it refers to the phenomenon of fibrous hornblende (mainly tremolite and Yang Qishi) aggregate metasomatism, so it is also called "nephrite". Diabase is also often characterized by fibrinization.

(2) sodium epidote: This is a frequent alteration of the basic plagioclase, especially the basic plagioclase near the orebody, which is always replaced by a different degree of sodium body. "Sodium epidote" is a collection of minerals such as albite, vepidite and epidote. There is no or a small amount of sericite, chlorite, quartz, garnet and other minerals. Other secondary changes include sericite, KAOLINIZATION, grapesolization, pyrochlorite, carbonization and olivine serpentinization of plagioclase.

Physical characteristics:
The physical characteristics of diorite are: the compressive strength is 130 ~ 200MPa (dry) or 100 ~ 160MPa (wet), the bending strength is 10 ~ 25MPa, the volume density is 2.85 ~ 3.00g/cm3, and the water absorption rate is 0.4%.

Main classification:
Quartz content is 5-20, dark mineral content is 15%, plagioclase (medium feldspar) accounts for more than half, and rock has semi self shape granular structure.
Typical Anhui Tongguanshan quartz diorite: plagioclase is a middle feldspar with a belt structure (70-75%), common hornblende (10%), diopside (5%), quartz (10%) and a small amount of potassium feldspar. Hypautomorphic granular structure with typical rock.

The main mineral compositions of granodiorite are quartz, Xie Changshi and potash feldspar. Plagioclase is generally more than potassium feldspar, and dark mineral content is also higher. The main associated minerals are copper, iron and so on.
The characteristic of granodiorite is that the content of plagioclase is more than that of potassium feldspar. In general, the plagioclase is about 2/3 of the total feldspar, while the dark minerals are mainly amphibolites and some are black mica. Quartz content is generally less than that of granite. It is an intermediate acid rock which is granite overturned to diorite.
The granite diorite has more plagioclase and dark minerals than granite (plagioclase is more than potash feldspar, while granite is opposite), so the color of the rock is a little deeper than granite, and it is gray green or dark grey. Plagioclase minerals accounted for 65-90% of the total, is generally acidic and neutral plagioclase, often with obvious zoning structure. Quartz content is less than granite, generally around 25%. With more dark colored minerals hornblende, accessory minerals are titanite, apatite, magnetite, zircon, allanite and monazite etc.. Common subhedral granular texture, porphyritic structure. [2]

Tonalite (Tonalite) an acidic plutonic phaneritic in. It consists mainly of plagioclase (feldspar, feldspar, about 2/3) and quartz and biotite. The plagioclase often has the dark mineral of the belt structure except for the black mica, and sometimes with amphibole and pyroxene. Alkaline feldspar (usually feldspar) is usually produced by interstitial products, but its amount is less than 10% of feldspar. Is a common accessory mineral apatite, sphene, magnetite. [2]

Distribution range:
Diorite is seldom composed of independent rock masses, and is often associated with basic rocks, acidic rocks or alkaline rocks, and becomes the marginal part of other kinds of rocks. If the formation of independent rock, intrusive rock plant, also some small or irregular rock. Such as "Tai'an green" in Shandong, the "big stone green" granite in Zhejiang is a kind of granite, the ore body is granite diorite, mineral composition of quartz, black mica, hornblende and feldspar, regardless of "Tai'an green" or "big stone green" in the presence of hornblende, and green and petrified and green, green and green.

Diorite often has unique style and is used as exterior wall facing stone. But the general diorite polishing is more difficult, and mostly used to make steps and balcony floors. The more famous varieties are Shandong Tai'an green and Jilin diorite.
Diorite has the same structural characteristics as granite, but because of the darker color and limited supply of diorite, the diorite is seldom used for decoration and building stone. Diorite, a dark gray stone, is commercially sold as "black granite". Some diorite is a real igneous rock, crystallized from molten matter (magma). Other diorite is a product of magma reacting with the fragments of exotic rocks. Many diorite rocks are converted by chemical changes when some older rocks, such as gabbro, lose some of their constituent atoms and get some other atoms in the solid state.

Diorite is often produced by small rock mass, such as rock bed, rock vein, rock strain, or more irregular rock mass associated with gabbro and associated with granodiorite and granite.