Weathering Flashcards
Types of physical weathering
- fracturing
- dissaggregation
types of chemical weathering
- dissolution of primary and secondary minerals
- precipitation of secondary minerals (biomineralisation)
- direct transformation of minerals (oxidation and reduction)
why do minerals chemically weather
when they are formed under specific P and T conditions and then the conditions are changed - they are no longer in thermodynamic equilibrium
- also the presence of water, oxygen and other reactants cause weathering
What are the two types of mineral dissolution
- Proton promoted dissolution
- Ligand promoted dissolution
what is a ligand
anions or neutral molecules that associate with a cation to form a complex - they generally donate electrons to the cations during complexation
What is multi-dentate ligands and are more or less teeth better
- chelate or chelators
- more teech is stronger complexation
what is a siderophile
iron lover
siderophoresq
- multidentate organic chelators
- made by ligand-promoted dissolution
what are the effects of microbes on dissolution
biology speeds up dissolution
What are direct microbe-weathering interactions
attachment and colonization
what are indirect microbe-weathering interactions
- change of saturation state
- production or consumption of CO2 or ligands
- change of redox potential or pH
describe attachment and colonisation of minerals
- inhibit or enhance dissolution
- preferential attachment to nutrient sources
what does hyphae do
can drill, wedge into minerals
what does endolithic bacteria do
physically live in rock pores and increase erosion rates
(DIRECT microbial effects on dissolution) once microbes attach to a surface what do they do
- can form etch pits
- can preferentially remove nutrients
