Hashemite University Faculty of Natural Resources and Environment Department of earth and environmental sciences
Economic Geology (111201491) !
Part5: Ore deposits in a global tectonic context ! !
Dr. Faten Al-Slaty First Semester 2015/2016 Patterns In The Distribution Of Mineral Deposits
Mineralization are not randomly distributed, either in time or in space, and that broad patterns exist when relating deposit types to crustal evolution and global tectonic setting. hydrothermal and volcano-sedimentary base– deposits formed mainly in late Archean and Phanerozoic times, whereas chemical– sedimentary and ultra-mafic deposits reflect concentration mechanisms that took place in the mid-Proterozoic.
!2 Plate Tectonics And Ore Deposits A. Extensional settings Incipient rifting of stable continental crust, where thinning and extension may be related to hotspot activity. Magmatism is often localized as alkaline or ultr-apotassic in character. ore deposit types formed in this setting includes:
• Granites such as those of the Bushveld Complex (Cr, Sn, W, Mo, Cu, F, etc.), • pyroxenite–carbonatite intrusions (Cu–Fe–P–U–REE etc.), and • kimberlites (diamonds) !3 ITOC06 09/03/2009 14:34 Page 340
340 PART 4 GLOBAL TECTONICS AND METALLOGENY
EXTENSIONAL SETTINGS
(a) INTRA-CONTINENTAL HOTSPOT/INCIPIENT RIFT
Kimberlite Carbonatite Nb, P2O5, F, Nb, REE diamond SEDEX Pb-Zn-Ag Anorogenic granite Sn, F, Nb 0
km Ocean Continent
30
200 400
(b) INTER-CONTINENTAL RIFT ZONE
Evaporitic layer Red Sea Mn Metal-rich brines and muds 0 !4 km
30
200 400
(c) MID-OCEAN RIDGE AND HAWAII-TYPE HOT SPOT CHAIN LIL-rich Potassic basalt basalt Cyprus-type Fe, Mn, Zn, Pb VMS deposits 0 chemical sediments km
30 Alkali-depleted mantle Podiform Plume Cr, NiS, Pt
Primitive mantle Plume
Figure 6.14 Simplified illustrations of the major extensional tectonic settings and the ore deposit types associated with each (modified after Mitchell and Garson, 1981). • SEDEX-type (Sedimentary exhalative deposits) Pb –Zn– Ba–Ag deposits. • As continental rifting extends to the point that incipient oceans begin to open (such as the Red Sea;), basaltic volcanism marks the site of a mid- ocean ridge. !
Such settings also provide the environments for: • Hydrothermal activity and plentiful VMS deposit formation ((Volcanogenic massive sulfide). • Chemical sedimentation and precipitation of banded iron-formations and manganiferous sediments. • Organic accumulations that on catagenesis give rise to oil deposits. !5 ITOC06 09/03/2009 14:34 Page 340
340 PART 4 GLOBAL TECTONICS AND METALLOGENY
EXTENSIONAL SETTINGS
(a) INTRA-CONTINENTAL HOTSPOT/INCIPIENT RIFT
Kimberlite Carbonatite Nb, P2O5, F, Nb, REE diamond SEDEX Pb-Zn-Ag Anorogenic granite Sn, F, Nb 0
km Ocean Continent
30
200 400
(b) INTER-CONTINENTAL RIFT ZONE
Evaporitic layer Red Sea Mn Metal-rich brines and muds 0 km
30
200 400
(c) MID-OCEAN RIDGE AND HAWAII-TYPE HOT SPOT CHAIN LIL-rich Potassic basalt basalt Cyprus-type Fe, Mn, Zn, Pb VMS deposits 0 chemical sediments !6 km
30 Alkali-depleted mantle Podiform Plume Cr, NiS, Pt
Primitive mantle Plume
Figure 6.14 Simplified illustrations of the major extensional tectonic settings and the ore deposit types associated with each (modified after Mitchell and Garson, 1981). • Carbonate sedimentation provides the rocks which host MVT deposits (Mississippi Valley-Type Lead-Zinc Ores) !
• Exhalative activity at these sites gives rise to “black- smoker” vents that provide the environments for the fomation of VMS deposits (Volcanogenic massive sulfide deposits). !
• The basalts which form at mid-ocean ridges also undergo fractional crystallization to form podiform chromite deposits as well as Cu–Ni–PGE sulfide.
!7 ITOC06 09/03/2009 14:34 Page 340
340 PART 4 GLOBAL TECTONICS AND METALLOGENY
EXTENSIONAL SETTINGS
(a) INTRA-CONTINENTAL HOTSPOT/INCIPIENT RIFT
Kimberlite Carbonatite Nb, P2O5, F, Nb, REE diamond SEDEX Pb-Zn-Ag Anorogenic granite Sn, F, Nb 0
km Ocean Continent
30
200 400
(b) INTER-CONTINENTAL RIFT ZONE
Evaporitic layer Red Sea Mn Metal-rich brines and muds 0 km
30
200 400
(c) MID-OCEAN RIDGE AND HAWAII-TYPE HOT SPOT CHAIN LIL-rich Potassic basalt basalt Cyprus-type Fe, Mn, Zn, Pb VMS deposits 0 chemical sediments km
30 Alkali-depleted mantle Podiform Plume Cr, NiS, Pt
Primitive mantle Plume
Figure 6.14 Simplified illustrations of the major extensional tectonic settings and the ore deposit types associated with each (modified after Mitchell and Garson, 1981).
!8 B. Compressional settings
!
The collisional margins are the sites of the great porphyry Cu–Mo provinces of the world.
!
Inboard of the arc significant Sn–W granitoid-hosted mineralization also occurs.
!
The volcanic regions above the porphyry systems are also the sites of hydrothermal precious metal mineralization. !9 ITOC06 09/03/2009 14:34 Page 341
ORE DEPOSITS IN A GLOBAL TECTONIC CONTEXT CHAPTER 6 341
COLLISIONAL SETTINGS
(a) ANDEAN TYPE OCEAN–CONTINENT COLLISION Epithermal Polymetallic gold skarn Mn nodules with Porphyry Cu, Mo Cu, Ni, Co 0 Ocean Continent km 30
60
200 400
(b) ISLAND ARC AND INTER-ARC BASIN (ocean–ocean collision)
Incipient rift Inactive Kuroko Zn, Cu inter-arc !10 basin Porphyry Cu-Au 0 km
30 NiS,Pt podiform Cr
200 400
Figure 6.15 Simplified illustrations of the major compressional tectonic settings and the ore deposit types associated with each (modified after Mitchell and Garson, 1981).
this setting. Intracontinental rifts can host catagenesis give rise to oil deposits. Carbonate SEDEX-type Pb–Zn–Ba–Ag deposits. As contin- sedimentation ultimately provides the rocks which ental rifting extends to the point that incipient host MVT deposits, although the hydrothermal oceans begin to open (such as the Red Sea; Figure processes that give rise to these epigenetic Pb–Zn 6.14b), basaltic volcanism marks the site of a mid- ores are typically associated with circulation dur- ocean ridge and this site is also accompanied by ing compressional stages of orogeny. Mid-ocean exhalative hydrothermal activity and plentiful ridges are the culmination of extensional pro- VMS deposit formation. Such settings also provide cesses (Figure 6.14c). Exhalative activity at these the environments for chemical sedimentation sites gives rise to “black-smoker” vents (such as and precipitation of banded iron-formations and those at 21° N on the East Pacific Rise) that pro- manganiferous sediments. Continental platforms vide the environments for the fomation of Cyprus commonly host organic accumulations that on type VMS deposits. The basalts which form at A similar tectonic setting can exist between two slabs of oceanic crust, as represented by the island arc environment
!
Porphyry Cu–Au deposits occasionally occur associated with the early stages of magmatism in these settings,
! whereas the later, more evolved calc–alkaline magmatism gives rise to VMS deposits.
!11 ITOC06 09/03/2009 14:34 Page 341
ORE DEPOSITS IN A GLOBAL TECTONIC CONTEXT CHAPTER 6 341
COLLISIONAL SETTINGS
(a) ANDEAN TYPE OCEAN–CONTINENT COLLISION Epithermal Polymetallic gold skarn Mn nodules with Porphyry Cu, Mo Cu, Ni, Co 0 Ocean Continent km 30
60
200 400
(b) ISLAND ARC AND INTER-ARC BASIN (ocean–ocean collision)
Incipient rift Inactive Kuroko Zn, Cu inter-arc basin Porphyry Cu-Au 0 km
30 NiS,Pt podiform Cr
200 400
Figure 6.15 Simplified illustrations of the major compressional tectonic settings and the ore deposit types associated with each (modified after Mitchell and Garson, 1981).
this setting. Intracontinental rifts can host catagenesis give rise to oil deposits. Carbonate SEDEX-type Pb–Zn–Ba–Ag deposits. As contin- sedimentation ultimately provides the rocks which ental rifting extends to the point that incipient !12 host MVT deposits, although the hydrothermal oceans begin to open (such as the Red Sea; Figure processes that give rise to these epigenetic Pb–Zn 6.14b), basaltic volcanism marks the site of a mid- ores are typically associated with circulation dur- ocean ridge and this site is also accompanied by ing compressional stages of orogeny. Mid-ocean exhalative hydrothermal activity and plentiful ridges are the culmination of extensional pro- VMS deposit formation. Such settings also provide cesses (Figure 6.14c). Exhalative activity at these the environments for chemical sedimentation sites gives rise to “black-smoker” vents (such as and precipitation of banded iron-formations and those at 21° N on the East Pacific Rise) that pro- manganiferous sediments. Continental platforms vide the environments for the fomation of Cyprus commonly host organic accumulations that on type VMS deposits. The basalts which form at !13