Nature of Ore-Bearing Fluids Flashcards
Ore-bearing fluids
Magma/Magmatic Fluids
Hydrothermal Fluids
is a high temperature rock melt of liquid and crystals
Magma
oxide or sulfide dominated magma that solidify directly as ore
Ore magma
a process where a partly crystallized magma is subjected to stress, the fluid fraction is squeezed off from the residual crystalline mush
Filter pressing
coexistence between two liquids and their separation from each other
liquid immiscibility
high temperature
100C - 800C
Hydrothermal Flow Mechanisms
Fluids released due to magma cooling
Density differences induced by intrusion
compaction of sediments
osmotic pumping
salinity differences
hydraulic pressure difference
metamorphic recrystallization of hydrous phases
fractionated fluids and volatiles that travel upward from the magma
magmatic/juvenile waters
Chalcophile elements
Cu, Pb, Zn, Ag, Au, As, S
Large Ion Lithophile
Li, be, B, Rb, Cs
Alkalies, AEE, Volatiles
Na, K, Cl, Ca, CO2, H2O
Deacrase viscosity of magmas, lower freezing points of minerals, make possible devolpment of minerals/complexes that would not form in a dry melt
Fluxes
Elements that do not fit in feldspars and mafic silicate
LILEs
any water that passed through and equilibrated with the atmosphere
Meteoric Water
a medium of dispersion of dissolved ions, molecules, and suspended particles
Seawater
Effects of Hydrothermal Fluid Density
Solubility of volatiles and non-volatiles solutes in supercritical water varies inversely with density
chloride complexes dissociate as hydrothermal fluid density decrease
water trapped in sediments at the time they were deposited
rich in Na and Cl
Connate Water
connate and meteoric water subjected to heat and pressure from magmatic intrusion
Metamorphic Waters
can be derived from the breakdown of hydrous minerals
Metamorphic Waters
products of hydrothermal fluid flow
Veins
Breccia
Hydrothermal Alteration
tabular veins of minerals that precipitated from hydrothermal fluids
veins
mineral growth in fluid-filled space
Distant Veins
planar body of hydrothermally altered rock adjacent to a fracture or a channelway
Replacement Veins
fluid is flowing through a rock
Open System
result of rock fragmentation in a pressure gradient
Brecciation
Causes of Fragmentation
Tectonic
Gravity collapse in open of fluid-filled space
explosive release of pressurized fluid
veins form due to local redistribution of fluids and solutes in a rock
Closed System
a chemical replacement of minerals where a fluid delivers the chemical reactants and removes the aqueous reaction products
hydrothermal Alteration
Commong Alteration Rxn
8
Hydrolysis Hydration Alkali or Alkali-Earth Metasomatism Decarbonation Silication Silicification Redox Sulfidation
Alteration Type
qtz, ms, tpz with common accessories of tur, fl, rt, cst, wolframite
Greisen
Alteration Type
bt, kfelds plus one ore more of the ff: ser, chl, qtz
Potassic
Alteration Type
ab, chl, ep, zeo, sme at low temp
Propylitic
Alteration Type
qtz, ser, py, chl
Sericitic
Alteration Type
qtz plus one or more of the ff; kln, dck, prl commonly ser, py, alu, tur, zunyite, tpz, dsp
Advanced Argilic
Alteration Type
sme, kln, crs
Argilic
Alteration Type
qtz, crs, trd, rt or ant
Silicic & Residual Silica
Alteration Type
cal, dol, ank, sd
Carbonate
Alteration Type
Ca and Mg silicates
Skarn