Lec 6 - Ore Morphology And Textures Flashcards
- Stratiform deposits
* layers/bed parallel to bedding
Bed
Formed by deposition along faults or fractures
Veins
Wide at the center and tapered at the sides
Lens
It has no geometric shape
Stock
Ore minerals are found along cross-cutting veinlets
Stockwork
Regular deposits?
Beds Veins Lens Stocks Stockwork Pipes/mantos
Ore minerals are scattered as individual or small clusters of inclusions
Disseminations
Ore minerals are disseminated in the matrix
Breccia
Irregular deposits
Breccia
Disseminated
Categories of ore textures
- magmatic deposition
- exsolution textures
- replacement textures
- open fill textures
- weathering
Result from direct crystallization! Fractionalization! Crystal settling! Filter pressing! And other magmatic ore-forming processes
Magmatic Ore Texture
Ores have homogeneous character and feature, usually made up of one or few minerals
Massive Texture
Dessimenation of minerals accumulate throughout the sample, giving the rock homegenous view
Dissemineted Texture
Ore minerals or disseminations of ore minerals accumulate as bands
Banded or Laminated Texture
Ores forms in the surface and are kidney-shaped
Nodular Texture
> Oolitic (mm)
> Pisolitic (cm)
A new mineral of partly or wholly difeering chemical composition may grow in the body of an old mineral or mineral aggregates
Replacement or Metasomatism
Mineral or mineral aggregate retaining the outward form proper to a pre-existing mineral or mineral aggregate which it has replaced
Pseudomorphs
Sulfides, Arsenides, Tellurides and Sulphosalts can replace any rock, Gangue, or ore mineral
Rules for replacement
Oxides replace all rock and gangue minerals but rarely replaced by gange minerals
Rules for replacement
Gangue minerals replace rock and other gangue minerals, but do not commonly replace sulfides, arsenides, tellurides, and sulphosalts
Rules for replacement
Oxides rarely replace sulfides, arsenides, tellurides and sulphosalts
Rules for replacement
Leading edge or front of replacement which was not completed
Vermicular intergrowths
Varying diffusion rates of ions at the replacement front
Cusp and Caries Texture
Separation of one mineral from another in a natural solution (unmixing)
*occurs in solid to solid keme
Exsolution
