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GLE 2024 (Day 3) > ORE DEP (VOLCANISM) > Flashcards

ORE DEP (VOLCANISM) Flashcards

1
Q

Hydrothermal deposits formed at low temp (100-320 deg cel) usually at shallow depths (<2km)

A

Epithermal Gold

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2
Q

Usual Ore minerals in Epithermal Systems

A

Native Gold
Silver
Tellurides and Sulfosalts

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3
Q

Usual Gangue in Epithermal Systems

A

Qtz ad Chalcedony
Carbonates
Fluorite
Barite
Sericite
Adularia
Clay

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4
Q

Common Textures of Ore minerals

A

Banded
Drusy
Comby
Crusty
Vuggy
Colloform

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5
Q

Alteration

A

Widespread Chloritic, Sericite, Qtx and Pyrite
Local Carbonates and Felds

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6
Q

Lindgrens Classification

A

Classification
1) Epithermal
2) Mesothermal
3) Hypothermal

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7
Q

Arc type ephitermal deposits

A

1) High Sulfidation
2) Int Sulfidation

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8
Q

Rift Type Epitherma system

A

Low Sulfidation

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9
Q

Bimodal Volcanism Related LSE

A

Alkalic LSE

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10
Q

Types of Epithermal Gold

A

pH

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11
Q

High Suplhidation

A

1-3 (Acidic)

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12
Q

Intermediate Sulphidation

A

5 (Mod Acidic)

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13
Q

Low Sulphidation

A

4-6 (Mildly Acidic)

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14
Q

Low Sulphidation Alkalic

A

> 6Basic

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15
Q

?sulfur is in very high oxidation state of +4 because of the dominance of magmatic SO2
?formed when very acidic fluids dominated by reactive magma derived gases migrate vertically along the sturtcure and permeable country rock and under fliuid reaction and fluid mixing
?generated in Calc-Alkaline Andesitic to Dacitic Arcs
?Near Neutral stress or Mild Extension
?Genetically linked to underlying PCD
?Cannot be related to Rhyolite

A

High Sulfidation

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16
Q

Indicative Minerals of High Sulifidation

A

Energite
Luzonite
Tennantite

17
Q

other names for High Sulfidation

A

Acidic Sulfate
Qtz-Alunite-Enargite Gold
Silica-Kaolinite +/- Pyrphyllite Gold

18
Q

Characteristics of High Sulfidation Epithermal

A

?Zoned Central Advance Argillic - Argillic to peripheral Prophylitic Alteration Zones
?Cu-Au-As Mineralozation common with Enargite /luzonite as dominant Cu Mineral phase and associated with Vuggy Silica
?Assoc with Calc Alkaline Volcanism

19
Q

Example of High Sulfidation

A

Lepanto
Nalesbitan Cam Norte

20
Q

IN what type of volcanism does Intermediate Sulfidation usually occurs?

A

Calc Alkaline Andesitic to Dacitic Arc
locally may be hosted in more felsoc rocks

21
Q

Difference of Intermediate from High Sulfidation

A

Unrelated to PCDs and can be hosted by Felsic or Rhyolitic Rocks

22
Q

Largest intermediate Sulphidation deposits

A

FSE-Lepanto-Victoria, Mankayan

23
Q

Other Intermediate Sulphidation in the Philippines

A

Acupan and Antamok Deposits, Baguio
Diwalwal, Comval
Maco
Aroroy
Co-O

24
Q

Formed when Magmatic fluids w/c contain dissolved reactive gas are REDUCED by rock reaction and dilution by the mixing with circualating meteoric Waters resulting in a FLUID DOMINATED by DISSOLVED SALTS and H2S as the MAIN SULFUR SPECIES

A

Low Sulfidation Epithermal

25
Q

In what type of tectonic environemnts are low sulfidation generated?

A

Rift typpe (Continental or Island Arcs)

26
Q

Low Sulfidation Minerals

A

Galena
Sphalerite
Chalcocite

27
Q

Two types of Low Sulfidation

A

1) Bimodal Volc
2) Alkaline

28
Q

LSE which is related to alkaline magmatism and is capable of generating Porphyry Cu-Au Deposits
Formed at Moderated saline fluids
High Temp >300 deg cel

A

Alkaline Low Suphidation

29
Q

Example of Alkline Low Sulphidation in the Philippines

A

Marian Isabela
Didipio, Neva Vizcaya

30
Q

LSE deposits found in various rift setting such as Intra-Arc, Near Arc or Back Arc during cessation of subduction and post collitional Settings

A

Bimodal Related LSE

31
Q

waning, retreat and steepening of the downgoing tectonic plate during subduction which can transform Earth’s surface by altering the stresses on the overriding plate.

A

Slab Rollback

32
Q

Rifting which may create Slab Windows

A

Oblique Subduction

33
Q

Gravitaional controlled lateral expansion of thiceknd crust followinge episodes of contractional deformation./Compression

A

Tectonic Collapse

34
Q

Riftingc caused by mantle Plume activity

A

Hot Spot

35
Q

Processes which may cause rifting

A

1) Slab RollBack
2) Slab Break off
3) Obliqe Subduction
4) tectonic Collapse
5) Hotspots

36
Q

? the invisible gold deposit or sediment hosted replacement Gold considered as low sulphidation epithermal Fluids in reactive carbonate rocks

A

Carlin Type Gold

37
Q

Morphology or teture of Carlin Type Gold

A

Very Fine Grained
Disseminations

38
Q

Host rocks

A

Carbonaceous Calcaerous Rocks
Jasperoids

39
Q

Examples

A

?Carlin, Nevada USA
?Bau, Malaysia
?Mesel, Indonesia
?Sepon Laos

GLE 2024 (Day 3) (48 decks)

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