ORE DEP (VOLCANISM)

Question 1

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

Answer 1

Epithermal Gold

Question 2

Usual Ore minerals in Epithermal Systems

Answer 2

Native Gold
Silver
Tellurides and Sulfosalts

Question 3

Usual Gangue in Epithermal Systems

Answer 3

Qtz ad Chalcedony
Carbonates
Fluorite
Barite
Sericite
Adularia
Clay

Question 4

Common Textures of Ore minerals

Answer 4

Banded
Drusy
Comby
Crusty
Vuggy
Colloform

Question 5

Alteration

Answer 5

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

Question 6

Lindgrens Classification

Answer 6

Classification
1) Epithermal
2) Mesothermal
3) Hypothermal

Question 7

Arc type ephitermal deposits

Answer 7

1) High Sulfidation
2) Int Sulfidation

Question 8

Rift Type Epitherma system

Answer 8

Low Sulfidation

Question 9

Bimodal Volcanism Related LSE

Answer 9

Alkalic LSE

Question 10

Types of Epithermal Gold

Answer 10

pH

Question 11

High Suplhidation

Answer 11

1-3 (Acidic)

Question 12

Intermediate Sulphidation

Answer 12

5 (Mod Acidic)

Question 13

Low Sulphidation

Answer 13

4-6 (Mildly Acidic)

Question 14

Low Sulphidation Alkalic

Answer 14

> 6Basic

Question 15

?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

Answer 15

High Sulfidation

Question 16

Indicative Minerals of High Sulifidation

Answer 16

Energite
Luzonite
Tennantite

Question 17

other names for High Sulfidation

Answer 17

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

Question 18

Characteristics of High Sulfidation Epithermal

Answer 18

?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

Question 19

Example of High Sulfidation

Answer 19

Lepanto
Nalesbitan Cam Norte

Question 20

IN what type of volcanism does Intermediate Sulfidation usually occurs?

Answer 20

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

Question 21

Difference of Intermediate from High Sulfidation

Answer 21

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

Question 22

Largest intermediate Sulphidation deposits

Answer 22

FSE-Lepanto-Victoria, Mankayan

Question 23

Other Intermediate Sulphidation in the Philippines

Answer 23

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

Question 24

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

Answer 24

Low Sulfidation Epithermal

Question 25

In what type of tectonic environemnts are low sulfidation generated?

Answer 25

Rift typpe (Continental or Island Arcs)

Question 26

Low Sulfidation Minerals

Answer 26

Galena Sphalerite Chalcocite

Question 27

Two types of Low Sulfidation

Answer 27

1) Bimodal Volc 2) Alkaline

Question 28

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

Answer 28

Alkaline Low Suphidation

Question 29

Example of Alkline Low Sulphidation in the Philippines

Answer 29

Marian Isabela Didipio, Neva Vizcaya

Question 30

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

Answer 30

Bimodal Related LSE

Question 31

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.

Answer 31

Slab Rollback

Question 32

Rifting which may create Slab Windows

Answer 32

Oblique Subduction

Question 33

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

Answer 33

Tectonic Collapse

Question 34

Riftingc caused by mantle Plume activity

Answer 34

Hot Spot

Question 35

Processes which may cause rifting

Answer 35

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

Question 36

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

Answer 36

Carlin Type Gold

Question 37

Morphology or teture of Carlin Type Gold

Answer 37

Very Fine Grained Disseminations

Question 38

Host rocks

Answer 38

Carbonaceous Calcaerous Rocks Jasperoids

Question 39

Examples

Answer 39

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