Chlorite is a common secondary mineral occurring after the alteration of minerals such as pyroxenes and amphiboles. But, this mineral occurs as a primary mineral?
Hi Mostafa, as far as I know, chlorite mainly occurs in hydrothermal alteration assemblages or in skarns. I have also seen traces of it in kimberlites, but most likely it had replaced small phlogopite crystals there.
Dear Mostafa,
Chlorite is a group of minerals that are formed as a secondary products in all rock types. I don't think that it may be formed as a primary mineral.
Hi Mostafa,
The most common species in the chlorite group are clinochlore and chamosite.
Chamosite and chlinochlore are also well known as primary mineralization, for example:
primary chlinochlore in alpine fissures in well-formed crystals (formed during the Regional Metamorphosis).
Chlinochlore (colorless) in eclogites formed during high pressure medium temperature metamorphism.
Chamosite in chamosite iron ores!
The chlorite group includes the following species see table attached, taken from Fleischer's Glossary of Mineral Species 2018. By Malcom E. Back, The Mineralogical Record Inc., Tucson.
Kind regards,
Guenter Grundmann
Guenter Grundmann
Thank you, prof. for your contribution. But, do you mean that this mineral can directly crystallize from the fissure-filling solutions? or do you mean that this mineral is a metasomatic mineral?... and what about the direct crystallization from magma?
Please study the petrogenesis of metamorphic rocks. Here you will find the stability conditions for chlorites.
At the upper limit of the lowe-grade metamorphism (greenschist / amphibolite facies transition zone, max. 550 °C) chlorite + muscovite in metapelites become unstable, forming staurolite, garnet, etc.
Primary chlorite, formed during prograde regional metamorphism remains stable up to max. temperature approx. 500 °C and max. pressure approx. 12 kbar
=> blueschist / eclogite (high pressure) facies transition zone.
It follows that above 550 °C, chlorites are not stable.
Granites form at about 600 °C, basalts at about 800 °C.
In this pressure / temperature range of magmatic rocks, chlorites are not stable !!
No primary magmatic crystallization of chlorite!
With kind regards,
Guenter Grundmann
Guenter Grundmann
Thank you very much for these valuable answers, which removed my hesitation.