ORE DEP (MAGMATIC HYDRO ORE PROCESSES) Flashcards
Notable properties of Water
High Heat Capacity
High Surface Tenstion
Max density just above freezing temp
High Dielectric constant
Clustering of water molecules around a dissolved ion
Hydration
Measure of a fluid’s ability to separate ions or other dipoles and is a function of the number of dipoles per unit vol
Dielectric Constant
Implication of high dielectic constant of water?
enhancing dissolution and increasing solubility
Lines of equal density
Isochores
Crystalline structure of Ice
Hexagonal
The phase boundary at which liquid and vapor are in equilibrium
Saturation vapor pressure
Boling Point Curve
Boiling point of water _______ as pressure increases
Increases
The point where it is no longer possible to increase the boiling pt by increase of pressure and where there is no longer a physical distinction between liquid and vapor
critical point
T and P of Critical Pt
374 deg cel and 221bar
The triple pt of water coexist at
0.008 deg cel
0.06 bar
Critical density of water at critical pt
0.3g/cc
a homogenous single phase (of water) that exist at pressures and temperatures above the critical point
Supercritical Fluid
Ideal Gas Law
PV=nRT
Early water derived from the degassing of volcanic magmas as they extruded onto the early crust
Juvenile Water
Substantial bodies of water first appeared on
Early Archean (Eoarchean) 3800 Ma
what is responsible for the water content of granitic magma?
Ponding of hyrdous basaltic melt at the base of the crust and diffusive transfer of elements and volatiles across conrod
Melting occurs without the presence of free water in the rock and is regarded as a realistic model for the generation of Granitic Magma in the Crust
Dehydration Melting
Arrange (Musc, Biot, Hnbld) in terms of water content (Hydrous)
(8-10%)Musc
(3-5%)Biot
(2-3%)Hbld
When meta-sed rocks compose of musc or musc+Biot-bearing rocks is melted it will produce
S-type Granites
Peraluminous
Relatively wet due to intila high H2O content
Ores related to wet Sgranite
Sn-W-U
What corresponds to the S granite in ishihara classification
Relatively reduced
Ilmenite series with low fO2
When meta-ign composed of Biot or Biot+Hbld Bearing rocks are melted it will yield
I-type Granite
Metaluminous
Relatively Dry
Ore deposits related to Itype Granites
Porphyry Cu-Mo
Why does magmatic hyrdothermal fluid boil at relatively shallow depth?
Because of low pressure and since the equilibrium vapor pressure equals that f the load pressure on the magmatic system and bubble of gas vesiculate
Process by which VAPORSATURATION Is achieved by VIRTUE OF DECREASING Pressure after only about 10% crystallization and the water content of resdiual magma is at 3.3%
first boiling
Where does first boiling usually occur?
high level systems (2km depth)
Vapor saturation achieved by progressive crystallization of dominantly anhydrous minerals under isobaric conditionsan occurs more in deep-seated magmatic systems and only after relatuvely advanced stage of crystallization
Second Boiling
Results in the overpressuring of the chamber interior and can cause brittle failure of the surroundung rocks
Hydrofracturing
The products of precipiration of silica from hot aqueous solutions precolating thru farctures in the Crust
Qtz veins
form of Qtz when dissolved
H4SiO4
Composition of solute in High Tand P conditions
High Si, Na and K
At lower P and T
Alkali decreases relative to silica
Anionic substances contained in the magmatic aqueous soln
Ligands
Typical solute content of magmatic fluis
Alkali, Alkali Earth metal Cations
Cl as dominant ligan
Amount of sulfur in magmatic fluids reflects
Crustal levels
At high crustal levels SO2 partitions into
Vaport Phase on Boiling
What Form of sulfur is related to I-type magmatic fluids?
Oxidized and ftationates in the liquid phase
Porphyry Cu and MO are asociated with abundant sulfides like
Pyrite and Chalcopyrite
Reduced sulfur content promotes stability of sulfide minerals to lower temp and leads to the formation of
Scheelite and Wolframite
Earlier generated fluids in primary fluid inclustions is characterized by
high T, High Salinity
Liqui-Vapor Phase Separation or boliing
What confirms the high salinites in ore forming fluids trapped in fluid inclusions
Daughter Crystals - Tiny minreals precipitated from fluid on coling after it was trapped w/in the incusion
Samples of daughter crystals
Halite and Sylvite
A technique qwhich accuratrely and completely assess PCD related ore fluid composition from the quantitative analysis of individual fluid inclusions. This allows analysis of a cationic species in tiny volume of inclusion fluid up to 1ppm
Laser Ablation (LA)
Inductively Couples Plasma (ICP)
Mass Spectrometry
In such boiling of magmatic fluid, where do metals or elements preferentially partition?
The liquid phase (Na, K, Fe, Mn, Cu, Pb and Zn)
where does Cu partition?
Into the vapor phase
In this kind of magma CO2 exist as carbonate ionic complex
Alkaline
CO2 solubility in magma is a function of
Presure and Alkalinity
Where does CO2 preferetntially partition in early crystallizaton?
Vapor hase
At higher crust describe CO2 abd H2O volatile levels
H2O is enriched while CO2 has already bubbled awat
High CO2 magmatic fluids will promote
Immiscibility between Vapor and Saline Liquid Phase
Whats the effects of Effervescene or removal of CO2 in the reminaing fluid
High Ph or salnity
Effects of increasing pressure in phase partitioning of magmatic fluid
decreasig salineinity Brine
slowly increasing Saline fluid
The tendency for brine solutions a low pressure, or in the presence of CO2 at higher pressure to segragate into two phases
Immiscibility
what are the two phases to which a magmatic brine segragate
1) Dense more saline Brine
2) Less dense low salinity aqueous soln
