Lec 7 - Geothermometry, Geobarometry, And Istope Studies Flashcards
What are your persitent minerals
Pyrite and gold
At surface conditions: oxides suffers ______, and sulfides suffers __________
Oxides suffers least and sulfides suffers most
- greek word means “born beside”
- used to describe any assemblage of ore minerals, with or without gangue, formed at the same time and normally in equilibrium.
Paragenesis
A collection or gathering of minerals or rock
Assemblage
Having a connection or resemblance with other mineral in certain temperature and pressure regime
Associated
Minerals that yield information as to the temperature of their formation
Geothermometers
The measurement of lavas, fumaroles, and hot springs
Direct Measurement
Indicate the maximum crystallization temperatures
Melting points
Hot spring measurements
Opal, gypsum, stibniteu
Some minerals lose volatile content at certain temperatures
Dissociation
Transformation of some minerals’ crystal sytem to naother is temp dependent
Inversion points
Minerals that form solid solutions unmix at specific temps to yield distinguishable intergrowths
Exsolution
Similar to inversion and exsolution but applies more specifically to native minerals
Recrsytallization
Crystals trap gases or liquids which they crystallizes
Fluid inclusion
Fluid inclusions in cavities of crystals indicate the ______________ of formation of the crystals by the amount of contraction of the liquid, assuming the liquid originally filled the cavity
Approximate Temperature
Heating the sample until an heterogenous fluid inclusion homogenizes
Minimum Temperatures of Formation
By freezing-point depression method. This temp is then used to read off the solution composition from a graph or calculated from equations
Total NaCl-equivalent salinity of the fluid
The minimum melting point
Eutectic point
Inclusion is opened up and direct tests are made on the liquid by optical-physical properties
Composition of Ore-Bearing fluid
Inclusions formed in growing crystals with no leakage
Primary
Inclusions that formed With fractures and sealed again,records comdition of later hydrothermal stage. Formed after primary crystallization
Secondary
Looks like secondary, but the host crystal was fractured as the crystal was growing
Pseudosecondary
It is important to remember always that the fluid inclusions in a mineral provide information only on the fluids present at the time of sealing of the inclusion, whether that be during the growth of the host crystal or during rehealing of a later fracture
Edwin Roedder, 1977
The estimation of pressure conditions at which a geologic material formed.
Geobarometry
