ORE DEP (INTERMEDIATE TO FELSIC) Flashcards
Young Mountain Belts has this composition
CalcAlkaline
Intrusion related deposit formed from segegration of magma fluid rich in iron with 4-5% of Phosphorous
Igneous Iron Deposit
2 types of Igneous Iron deposits
1) Volcanic sedimentary or Sedimentary
2) Intrusive Magmatic Segegation Ore
type of Igenous iron deposit source of important resource and the ferruginous melt vents to the surface as STRATABOUND IRON RICH DEPOSIT
Volcanic Sedimentary or Sedimentary
Type of igneous iron deposit in which the ferruginous melt is injected in an intrusive body forming podlike magnetite
Intrusive Magmatic Segregation Ore
Most productive Iron Deposit (Magmatic Segregation) in the World
Kirunaavara Mine in Sweden
Refers to HIGH PHOSPHOROUS IRON ORES (>2% P)
Kiruna type Ore
Large Volume, commonly low - medium grade deposit, primarily of Chalcopyrite and Molybdenite which exhibits HYPOGENE Sulphide and alteration silicate zoning and is temporally and spatially related to a epizonal calc-alkaline - alkaline porphyritic intrusions
Riley
Represent repeated and distinct mode of hydrothermal fluid escape from large intrusions i the crust (Magmatic Hydrothermal)
Large tonnage deposit (1Mt to 10 Gt) of ore in prevasively altered and veined rock in w/c ore minerals are uniformly dissemiated at relatviey LOW grades
Porphyry Base Metal Deposits
Mode of Mineralization
HF flow along dense network of small fractures through large volume of rock
where mineralization occurs both in the veins and isseminated in altered rock
Important Ore minerals in Porphyry deposist (riley)
1) Suflides of Cu and Cu-Fe
Chalcopyr, Bornite, Chalcocite
2) Sulfides of Mo Molybdenite
3) Native Gold (Rare)
4) Oxide of W (Scheelite (ca) and Wolframite (Fe-Mn)
5) Oxide of Sn Cassiterite
Ore Metal Content is dependent on
Tectonic Setting
Composition of Host Intrusion COmplex
Conditions of Formation of Porphyry Cu deposits
Depth: 2-4 km (Epizonal)
Pressure: <1-2 Kbar
Temp of Formation: 750-850 deg cel
Temp of Mineralization: 250-500 deg cel
How much of the World’s Cu is Prophyry?
75%
How much of the world’s Moly is Poprhyry?
50%
How much of the world’s Gold is from Porphyry?
20%
Grades of Por Cu
0.3-1.5% Cu
Grade of Por Au
Nil - 1.5 g/t Au
Grades of Por Mo
<0.01 -0.04%
Most sticking feature of a porphyry Cu/metal deposit?
Large Areas <1-2 sq.km.
Dominant Economic Cu Ore Mineral
Chalcopyrite
other Cu Ore
Bornite
Covellite
Cuprite
Chalcocite
Main Ore of Mo
Molybdenite
Improtant for a lot of deposits esp PCDs to make them economic and substantially higher in Cu Grade
Supergene Enrichment
Porphyry Model Variants occuring in Continental Magmatic Arcs and associated with I type porphyritic Intrusive and has low Mo grade
Porphyritic Mo
Porphyry Model Variant occuring in Island Arc, few in continental arcs, contain more magetite than Porphyry Cu-Mo
Porphyritic Cu-Au
Poprhyry Model Variant occuring in Tectonic and Continental Rifts associated with A-type high silicic porphyritic intrusion with higher Mo Grade
Climax Type Mo
ubiquitus and characteristic of the ORE ZONE and of deeper levels of most deposits esp of the barren core beneath and in the interior of the ore shell
Results from metasomatic addition of K+ at high temp
Potassic
(Qtz+/-Kfelds +/- Biotite)
Characteristic feature of the Potassic
High Conc of Magnetite
Occurs in some deposits peripheral to LOWER DEPTHS limits of the ore zones and NEVER a HOST TO ORE
result of SALINE WaTER infiltration at temp approx 450 deg cel
Sodic-Calcic
(Albite/Oligoclase +/- Actinolite +/- Magnetite) No Pyrite
Ubiquitous in Porphyry deposits but forms RELATVIELY LATE in the devt of the Hydrothermal system and OVERPRINTS earlier POTASSIC and CHLORITE SERICITIC zones esp the upper and peripheral (gilid) parts
Sericite is replacement of Kfelds
Results from mod to strong acidic fluids metasomatism involving addition of H+
Phyllic (QSP: Qtz +/- Sericite +/- Pyrite)
Presence of these features indicates late formation of QSP
D-Type Veinlets (Qtz+/-Pyrite) w/c crsos cut protassic altered rocks and A and B Type Veinlets of Potassic Altertaion
CAPS the ore zone at some deposits although may also include the ore
has characteristically pale green color
caused by similar fluids that formed the QSP but lower acidity
Chlorite-Sericite
Locally develop at SHALLOW LEVELS of hydrothermal system ABOVE and PERIPHERAL TO THE PHYLLIC ZONE
forms as a result of intense low temp metasomatism in w/c clay minerals are produced as a result of acid leaching of feldspars
Argillic Zone
(Clays Montmorillonite and Kaolinite)
Very ubiquitous and is extensively developed around most prophyry deposits w/c can extend up to seveal Km and
results from the addition of volatiles to the host rocks w/o significant metasomations
Propylitic
(Epidote Chlorite Calcite)
Alteration Zone
Spatial Characteristics
Potassic
Ore Zone
Sodic-Calcic
Peripheral to the lower limits of the Ore Zone
Phyllic
Late Formation usually overprints Potassic and Chlorite Sericitic
Chlorite-Sericite
Capping the ore zone
Argillic
Above and Peripheral to Phyllic at Shallow zones
Propylitic
Very Ubiquitous Around the ore body
Highest grade ore is found in?
Potassic Zone
What are the other possible sites of ore?
Chlorite-Sericite
Phyllic
IN porphry Cu, Ore occurs in?
Boundary between Potassic and Phyllic
Whats the implication of having mineralization in Phyllic?
Overprinting
Prograde Alterations Stages
Potassic - Propylitic
Retrograde Alteartion Stages
Phyllic - Advanced Argillic
Composition of earliest formed A veins
Granular Qtz+Chalco+Molyb+Bornite
Composition of B veins
Qtz+/-Molyb+/-Chalco+/-pyrite+/-suture
Composition of D vens
Qtz+/-Pyrite+/-minor Chalco
Composition of M veins
Magnetite+/-Actinolite
Age of common PCDs?
Mesozoic to Cenozoic
Oldest PCD in PH
Cebu (Cret)
Other PCDs in PH and ages
1) SW Negros and N.Vizacaya - Oligo
2) Luzon and E.Mindanao - M-L.Mio
3)W.Luzon and Cotabato - Plio-Pleisto
PCDs are (Epi, Meso) Thermal
Mesothermal
First model of the PCD based on San Manuel, Kalamazoo, Airzona and is based on SPATIAL relations only and did not recognize Adv. Argillic Alteration and Argilic mistaken to be hypogene instead of suprgene
Lowell and Gilbert 1970
Established PCD model for the Philippines based on 48 deposits and prospects wherein the causatie intusions are mainly Diroitic and Qtz Dioritic w/c are cylindrical but can be tabular as well. Introduced the Tops and Botoms concept
Sillitoe and Gappe
Philippine PCDs
1) Carmen Copper Atlas Toledo Cebu
2) Philex Sto.Tomas II Benguet
3) Oceana Gold’ Dikindi, Quirino, N vizcaya
Advanced PCD Prjects
1)Philex’s Boyongan-Bayugo Surigao del N
2) Indophil/Saggitarius Tampakan-S.Cotabato
3) Goldfield’s/Lepanto’s FSE-Benguet
4) St.Augustine’s Kingking - COMVAL
Alterations of PMD
Potassic w/ less developed Propylitic and Phyllic
What separates PMD from Climax Moly?
Low Flourine content and Low grade Mo
Other name of Poprhyritic Tin which is subvolcanic instrusive complexes containing disseminated, veinlet and breccia contrlolled fine ground cassiterite in qtz porphyry and adjacent rocks
Subvolcanic Tin
Exploration Markers for PCDs
1) Intrusive Complexes
2) Potassic Alteration (Biotite, Magnetite +Kfelds)
3) Cu-Fe Sulfide Mineralisation
4) Qtz. Vein Stockworkds
5) Magneite vein and aleration
Alteration sa sides
Selvedges
aka Replacement Deposits formed by replacement (Contact Metasomatism) of Limestones, Calcareous rocks (Marl or Calc-Schist) or Dolomite as a result of invasion of hyrothermal fluids carrying the high metal concentrations outward from the intrusion
Skarn Deposits
Most common Skarn Minerals
1) Magnetite, Hemmatite
2) Chalcopyrite, Molybdenite Sphalerite and Galena
3) Epidote, garnet, Pyrx
4) Scheelite
5) Gold
Characteristic Alteration of Skarns
Andradite + Diopside
Temp of formation for scarns
350-800 deg cel
High temp waters
Prograde Minerals formed
Lower fluid temp
Retrograde Minerals formed
Skarn within the pluton and Gar>pyx,
or Sedimentary Protolith
Exoskarn
Skarn within the country Rock Pyx > Gar
Ignours Protolith
Endoskarn
Philippines Skarns
1) Thanksgiving Cu-Au-Zn, Acupan, Benguet
2) Paracale Fe - Cam Norte
Also known as Post-Magmatic or Magmatic Hydrootherma which are epigenetic space filling deposits which are coprecipitates in silicate hosts rocks or replacement in carbonate hosts and contains same suites of elements and ore minerals as PCD
Cordilleran Vein Type Deposit
