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Geology, Palaeontology & Archaeology / Re: How to genetically classify a weathering mineral?
« on: 17/11/2021 08:00:39 »
@Zer0 Thank you!
I have 180 minerals in my app. Each sheet has a field: environments of formation. @Bass It has multiple environments, not only one. In this field I have for example for chrysotile two environments:
Then I create questions with code for the students as:
@Bass Maybe chrysotile is not a good example. I have other minerals that also form in surface as an alteration/weathering product. Some of them form on soils:
Diaspore
If the mineral is formed in diagenesis I am classifying it as Sedimentary even it is a neoformation mineral from preexisting ones.
As an alteration product the genetic origin of chrysotile is not magmatic, it is an alteration product of magmatic rocks in surface. This applies to many clays and other minerals that are neoformation minerals from preexisting ones in surface rocks or soils as montmorillonite.
They are exogenous, they are not supergenic, so, they would be sedimentary?
@Bass When a rock is weathered in surface, there is not allways an enrichment. I understand supergenic proccess as an enrichment and usually related with ores and gangas formation by interaction of basin or magmatic waters with preexisting rocks. A clay in a soil is not ganga of any ore, it is not an enrichment product, it forms because the preexisting mineral is not stable in the surface conditions.
Might I add a field "Surface alteration" or "Weathering"?
What do you think it would be better for the students?:
Chrysotile
I have 180 minerals in my app. Each sheet has a field: environments of formation. @Bass It has multiple environments, not only one. In this field I have for example for chrysotile two environments:
- Metamorphic: Contact and regional of ultramafic rocks (serpentinites).
- ??: Alteration of mafic rocks in surface.
Then I create questions with code for the students as:
- What of this minerals forms in the environment [??] Alteration of mafic rocks in surface?
- a) Pirite
- b) Chrysotile
- c) Enargite
- d) Calcite
@Bass Maybe chrysotile is not a good example. I have other minerals that also form in surface as an alteration/weathering product. Some of them form on soils:
Diaspore
- Sedimentary??: bauxites.
- Metamorphic: low degree of pelitic rocks.
If the mineral is formed in diagenesis I am classifying it as Sedimentary even it is a neoformation mineral from preexisting ones.
As an alteration product the genetic origin of chrysotile is not magmatic, it is an alteration product of magmatic rocks in surface. This applies to many clays and other minerals that are neoformation minerals from preexisting ones in surface rocks or soils as montmorillonite.
They are exogenous, they are not supergenic, so, they would be sedimentary?
@Bass When a rock is weathered in surface, there is not allways an enrichment. I understand supergenic proccess as an enrichment and usually related with ores and gangas formation by interaction of basin or magmatic waters with preexisting rocks. A clay in a soil is not ganga of any ore, it is not an enrichment product, it forms because the preexisting mineral is not stable in the surface conditions.
Might I add a field "Surface alteration" or "Weathering"?
What do you think it would be better for the students?:
Chrysotile
- Supergenic: Alteration of mafic rocks in surface.
- Sedimentary: Alteration of mafic rocks in surface.
- Surface alteration: Alteration of mafic rocks in surface.
- Weathering: Alteration of mafic rocks in surface.
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