ORE DEP (INTERMEDIATE TO FELSIC) Flashcards by Sean Levi Abiera

Young Mountain Belts has this composition

CalcAlkaline

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Intrusion related deposit formed from segegration of magma fluid rich in iron with 4-5% of Phosphorous

Igneous Iron Deposit

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2 types of Igneous Iron deposits

1) Volcanic sedimentary or Sedimentary
2) Intrusive Magmatic Segegation Ore

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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

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Type of igneous iron deposit in which the ferruginous melt is injected in an intrusive body forming podlike magnetite

Intrusive Magmatic Segregation Ore

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Most productive Iron Deposit (Magmatic Segregation) in the World

Kirunaavara Mine in Sweden

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Refers to HIGH PHOSPHOROUS IRON ORES (>2% P)

Kiruna type Ore

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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

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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

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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

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Ore Metal Content is dependent on

Tectonic Setting
Composition of Host Intrusion COmplex

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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

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How much of the World’s Cu is Prophyry?

75%

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How much of the world’s Moly is Poprhyry?

50%

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How much of the world’s Gold is from Porphyry?

20%

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Grades of Por Cu

0.3-1.5% Cu

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Grade of Por Au

Nil - 1.5 g/t Au

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Grades of Por Mo

<0.01 -0.04%

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Most sticking feature of a porphyry Cu/metal deposit?

Large Areas <1-2 sq.km.

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Dominant Economic Cu Ore Mineral

Chalcopyrite

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other Cu Ore

Bornite
Covellite
Cuprite
Chalcocite

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Main Ore of Mo

Molybdenite

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Improtant for a lot of deposits esp PCDs to make them economic and substantially higher in Cu Grade

Supergene Enrichment

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Porphyry Model Variants occuring in Continental Magmatic Arcs and associated with I type porphyritic Intrusive and has low Mo grade

Porphyritic Mo

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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

ORE DEP (INTERMEDIATE TO FELSIC) Flashcards

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